1 \input texinfo @c -*- texinfo -*-
2 @setfilename gdbint.info
4 @settitle @value{GDBN} Internals
6 @dircategory Software development
8 * Gdb-Internals: (gdbint). The GNU debugger's internals.
12 Copyright @copyright{} 1990-1994, 1996, 1998-2006, 2008-2012 Free
13 Software Foundation, Inc.
14 Contributed by Cygnus Solutions. Written by John Gilmore.
15 Second Edition by Stan Shebs.
17 Permission is granted to copy, distribute and/or modify this document
18 under the terms of the GNU Free Documentation License, Version 1.3 or
19 any later version published by the Free Software Foundation; with no
20 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
21 Texts. A copy of the license is included in the section entitled ``GNU
22 Free Documentation License''.
26 This file documents the internals of the GNU debugger @value{GDBN}.
34 @title @value{GDBN} Internals
35 @subtitle A guide to the internals of the GNU debugger
37 @author Cygnus Solutions
38 @author Second Edition:
40 @author Cygnus Solutions
43 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
44 \xdef\manvers{\$Revision$} % For use in headers, footers too
46 \hfill Cygnus Solutions\par
48 \hfill \TeX{}info \texinfoversion\par
52 @vskip 0pt plus 1filll
59 @c Perhaps this should be the title of the document (but only for info,
60 @c not for TeX). Existing GNU manuals seem inconsistent on this point.
61 @top Scope of this Document
63 This document documents the internals of the GNU debugger, @value{GDBN}. It
64 includes description of @value{GDBN}'s key algorithms and operations, as well
65 as the mechanisms that adapt @value{GDBN} to specific hosts and targets.
78 * Target Architecture Definition::
79 * Target Descriptions::
80 * Target Vector Definition::
86 * Versions and Branches::
87 * Start of New Year Procedure::
92 * GDB Observers:: @value{GDBN} Currently available observers
93 * GNU Free Documentation License:: The license for this documentation
95 * Function and Variable Index::
107 @section Requirements
108 @cindex requirements for @value{GDBN}
110 Before diving into the internals, you should understand the formal
111 requirements and other expectations for @value{GDBN}. Although some
112 of these may seem obvious, there have been proposals for @value{GDBN}
113 that have run counter to these requirements.
115 First of all, @value{GDBN} is a debugger. It's not designed to be a
116 front panel for embedded systems. It's not a text editor. It's not a
117 shell. It's not a programming environment.
119 @value{GDBN} is an interactive tool. Although a batch mode is
120 available, @value{GDBN}'s primary role is to interact with a human
123 @value{GDBN} should be responsive to the user. A programmer hot on
124 the trail of a nasty bug, and operating under a looming deadline, is
125 going to be very impatient of everything, including the response time
126 to debugger commands.
128 @value{GDBN} should be relatively permissive, such as for expressions.
129 While the compiler should be picky (or have the option to be made
130 picky), since source code lives for a long time usually, the
131 programmer doing debugging shouldn't be spending time figuring out to
132 mollify the debugger.
134 @value{GDBN} will be called upon to deal with really large programs.
135 Executable sizes of 50 to 100 megabytes occur regularly, and we've
136 heard reports of programs approaching 1 gigabyte in size.
138 @value{GDBN} should be able to run everywhere. No other debugger is
139 available for even half as many configurations as @value{GDBN}
143 @section Contributors
145 The first edition of this document was written by John Gilmore of
146 Cygnus Solutions. The current second edition was written by Stan Shebs
147 of Cygnus Solutions, who continues to update the manual.
149 Over the years, many others have made additions and changes to this
150 document. This section attempts to record the significant contributors
151 to that effort. One of the virtues of free software is that everyone
152 is free to contribute to it; with regret, we cannot actually
153 acknowledge everyone here.
156 @emph{Plea:} This section has only been added relatively recently (four
157 years after publication of the second edition). Additions to this
158 section are particularly welcome. If you or your friends (or enemies,
159 to be evenhanded) have been unfairly omitted from this list, we would
160 like to add your names!
163 A document such as this relies on being kept up to date by numerous
164 small updates by contributing engineers as they make changes to the
165 code base. The file @file{ChangeLog} in the @value{GDBN} distribution
166 approximates a blow-by-blow account. The most prolific contributors to
167 this important, but low profile task are Andrew Cagney (responsible
168 for over half the entries), Daniel Jacobowitz, Mark Kettenis, Jim
169 Blandy and Eli Zaretskii.
171 Eli Zaretskii and Daniel Jacobowitz wrote the sections documenting
174 Jeremy Bennett updated the sections on initializing a new architecture
175 and register representation, and added the section on Frame Interpretation.
178 @node Overall Structure
180 @chapter Overall Structure
182 @value{GDBN} consists of three major subsystems: user interface,
183 symbol handling (the @dfn{symbol side}), and target system handling (the
186 The user interface consists of several actual interfaces, plus
189 The symbol side consists of object file readers, debugging info
190 interpreters, symbol table management, source language expression
191 parsing, type and value printing.
193 The target side consists of execution control, stack frame analysis, and
194 physical target manipulation.
196 The target side/symbol side division is not formal, and there are a
197 number of exceptions. For instance, core file support involves symbolic
198 elements (the basic core file reader is in BFD) and target elements (it
199 supplies the contents of memory and the values of registers). Instead,
200 this division is useful for understanding how the minor subsystems
203 @section The Symbol Side
205 The symbolic side of @value{GDBN} can be thought of as ``everything
206 you can do in @value{GDBN} without having a live program running''.
207 For instance, you can look at the types of variables, and evaluate
208 many kinds of expressions.
210 @section The Target Side
212 The target side of @value{GDBN} is the ``bits and bytes manipulator''.
213 Although it may make reference to symbolic info here and there, most
214 of the target side will run with only a stripped executable
215 available---or even no executable at all, in remote debugging cases.
217 Operations such as disassembly, stack frame crawls, and register
218 display, are able to work with no symbolic info at all. In some cases,
219 such as disassembly, @value{GDBN} will use symbolic info to present addresses
220 relative to symbols rather than as raw numbers, but it will work either
223 @section Configurations
227 @dfn{Host} refers to attributes of the system where @value{GDBN} runs.
228 @dfn{Target} refers to the system where the program being debugged
229 executes. In most cases they are the same machine, in which case a
230 third type of @dfn{Native} attributes come into play.
232 Defines and include files needed to build on the host are host
233 support. Examples are tty support, system defined types, host byte
234 order, host float format. These are all calculated by @code{autoconf}
235 when the debugger is built.
237 Defines and information needed to handle the target format are target
238 dependent. Examples are the stack frame format, instruction set,
239 breakpoint instruction, registers, and how to set up and tear down the stack
242 Information that is only needed when the host and target are the same,
243 is native dependent. One example is Unix child process support; if the
244 host and target are not the same, calling @code{fork} to start the target
245 process is a bad idea. The various macros needed for finding the
246 registers in the @code{upage}, running @code{ptrace}, and such are all
247 in the native-dependent files.
249 Another example of native-dependent code is support for features that
250 are really part of the target environment, but which require
251 @code{#include} files that are only available on the host system. Core
252 file handling and @code{setjmp} handling are two common cases.
254 When you want to make @value{GDBN} work as the traditional native debugger
255 on a system, you will need to supply both target and native information.
257 @section Source Tree Structure
258 @cindex @value{GDBN} source tree structure
260 The @value{GDBN} source directory has a mostly flat structure---there
261 are only a few subdirectories. A file's name usually gives a hint as
262 to what it does; for example, @file{stabsread.c} reads stabs,
263 @file{dwarf2read.c} reads @sc{DWARF 2}, etc.
265 Files that are related to some common task have names that share
266 common substrings. For example, @file{*-thread.c} files deal with
267 debugging threads on various platforms; @file{*read.c} files deal with
268 reading various kinds of symbol and object files; @file{inf*.c} files
269 deal with direct control of the @dfn{inferior program} (@value{GDBN}
270 parlance for the program being debugged).
272 There are several dozens of files in the @file{*-tdep.c} family.
273 @samp{tdep} stands for @dfn{target-dependent code}---each of these
274 files implements debug support for a specific target architecture
275 (sparc, mips, etc). Usually, only one of these will be used in a
276 specific @value{GDBN} configuration (sometimes two, closely related).
278 Similarly, there are many @file{*-nat.c} files, each one for native
279 debugging on a specific system (e.g., @file{sparc-linux-nat.c} is for
280 native debugging of Sparc machines running the Linux kernel).
282 The few subdirectories of the source tree are:
286 Code that implements @dfn{CLI}, the @value{GDBN} Command-Line
287 Interpreter. @xref{User Interface, Command Interpreter}.
290 Code for the @value{GDBN} remote server.
293 Code for Insight, the @value{GDBN} TK-based GUI front-end.
296 The @dfn{GDB/MI}, the @value{GDBN} Machine Interface interpreter.
299 Target signal translation code.
302 Code for @dfn{TUI}, the @value{GDBN} Text-mode full-screen User
303 Interface. @xref{User Interface, TUI}.
311 @value{GDBN} uses a number of debugging-specific algorithms. They are
312 often not very complicated, but get lost in the thicket of special
313 cases and real-world issues. This chapter describes the basic
314 algorithms and mentions some of the specific target definitions that
317 @section Prologue Analysis
319 @cindex prologue analysis
320 @cindex call frame information
321 @cindex CFI (call frame information)
322 To produce a backtrace and allow the user to manipulate older frames'
323 variables and arguments, @value{GDBN} needs to find the base addresses
324 of older frames, and discover where those frames' registers have been
325 saved. Since a frame's ``callee-saves'' registers get saved by
326 younger frames if and when they're reused, a frame's registers may be
327 scattered unpredictably across younger frames. This means that
328 changing the value of a register-allocated variable in an older frame
329 may actually entail writing to a save slot in some younger frame.
331 Modern versions of GCC emit Dwarf call frame information (``CFI''),
332 which describes how to find frame base addresses and saved registers.
333 But CFI is not always available, so as a fallback @value{GDBN} uses a
334 technique called @dfn{prologue analysis} to find frame sizes and saved
335 registers. A prologue analyzer disassembles the function's machine
336 code starting from its entry point, and looks for instructions that
337 allocate frame space, save the stack pointer in a frame pointer
338 register, save registers, and so on. Obviously, this can't be done
339 accurately in general, but it's tractable to do well enough to be very
340 helpful. Prologue analysis predates the GNU toolchain's support for
341 CFI; at one time, prologue analysis was the only mechanism
342 @value{GDBN} used for stack unwinding at all, when the function
343 calling conventions didn't specify a fixed frame layout.
345 In the olden days, function prologues were generated by hand-written,
346 target-specific code in GCC, and treated as opaque and untouchable by
347 optimizers. Looking at this code, it was usually straightforward to
348 write a prologue analyzer for @value{GDBN} that would accurately
349 understand all the prologues GCC would generate. However, over time
350 GCC became more aggressive about instruction scheduling, and began to
351 understand more about the semantics of the prologue instructions
352 themselves; in response, @value{GDBN}'s analyzers became more complex
353 and fragile. Keeping the prologue analyzers working as GCC (and the
354 instruction sets themselves) evolved became a substantial task.
356 @cindex @file{prologue-value.c}
357 @cindex abstract interpretation of function prologues
358 @cindex pseudo-evaluation of function prologues
359 To try to address this problem, the code in @file{prologue-value.h}
360 and @file{prologue-value.c} provides a general framework for writing
361 prologue analyzers that are simpler and more robust than ad-hoc
362 analyzers. When we analyze a prologue using the prologue-value
363 framework, we're really doing ``abstract interpretation'' or
364 ``pseudo-evaluation'': running the function's code in simulation, but
365 using conservative approximations of the values registers and memory
366 would hold when the code actually runs. For example, if our function
367 starts with the instruction:
370 addi r1, 42 # add 42 to r1
373 we don't know exactly what value will be in @code{r1} after executing
374 this instruction, but we do know it'll be 42 greater than its original
377 If we then see an instruction like:
380 addi r1, 22 # add 22 to r1
383 we still don't know what @code{r1's} value is, but again, we can say
384 it is now 64 greater than its original value.
386 If the next instruction were:
389 mov r2, r1 # set r2 to r1's value
392 then we can say that @code{r2's} value is now the original value of
395 It's common for prologues to save registers on the stack, so we'll
396 need to track the values of stack frame slots, as well as the
397 registers. So after an instruction like this:
403 then we'd know that the stack slot four bytes above the frame pointer
404 holds the original value of @code{r1} plus 64.
408 Of course, this can only go so far before it gets unreasonable. If we
409 wanted to be able to say anything about the value of @code{r1} after
413 xor r1, r3 # exclusive-or r1 and r3, place result in r1
416 then things would get pretty complex. But remember, we're just doing
417 a conservative approximation; if exclusive-or instructions aren't
418 relevant to prologues, we can just say @code{r1}'s value is now
419 ``unknown''. We can ignore things that are too complex, if that loss of
420 information is acceptable for our application.
422 So when we say ``conservative approximation'' here, what we mean is an
423 approximation that is either accurate, or marked ``unknown'', but
426 Using this framework, a prologue analyzer is simply an interpreter for
427 machine code, but one that uses conservative approximations for the
428 contents of registers and memory instead of actual values. Starting
429 from the function's entry point, you simulate instructions up to the
430 current PC, or an instruction that you don't know how to simulate.
431 Now you can examine the state of the registers and stack slots you've
437 To see how large your stack frame is, just check the value of the
438 stack pointer register; if it's the original value of the SP
439 minus a constant, then that constant is the stack frame's size.
440 If the SP's value has been marked as ``unknown'', then that means
441 the prologue has done something too complex for us to track, and
442 we don't know the frame size.
445 To see where we've saved the previous frame's registers, we just
446 search the values we've tracked --- stack slots, usually, but
447 registers, too, if you want --- for something equal to the register's
448 original value. If the calling conventions suggest a standard place
449 to save a given register, then we can check there first, but really,
450 anything that will get us back the original value will probably work.
453 This does take some work. But prologue analyzers aren't
454 quick-and-simple pattern patching to recognize a few fixed prologue
455 forms any more; they're big, hairy functions. Along with inferior
456 function calls, prologue analysis accounts for a substantial portion
457 of the time needed to stabilize a @value{GDBN} port. So it's
458 worthwhile to look for an approach that will be easier to understand
459 and maintain. In the approach described above:
464 It's easier to see that the analyzer is correct: you just see
465 whether the analyzer properly (albeit conservatively) simulates
466 the effect of each instruction.
469 It's easier to extend the analyzer: you can add support for new
470 instructions, and know that you haven't broken anything that
471 wasn't already broken before.
474 It's orthogonal: to gather new information, you don't need to
475 complicate the code for each instruction. As long as your domain
476 of conservative values is already detailed enough to tell you
477 what you need, then all the existing instruction simulations are
478 already gathering the right data for you.
482 The file @file{prologue-value.h} contains detailed comments explaining
483 the framework and how to use it.
486 @section Breakpoint Handling
489 In general, a breakpoint is a user-designated location in the program
490 where the user wants to regain control if program execution ever reaches
493 There are two main ways to implement breakpoints; either as ``hardware''
494 breakpoints or as ``software'' breakpoints.
496 @cindex hardware breakpoints
497 @cindex program counter
498 Hardware breakpoints are sometimes available as a builtin debugging
499 features with some chips. Typically these work by having dedicated
500 register into which the breakpoint address may be stored. If the PC
501 (shorthand for @dfn{program counter})
502 ever matches a value in a breakpoint registers, the CPU raises an
503 exception and reports it to @value{GDBN}.
505 Another possibility is when an emulator is in use; many emulators
506 include circuitry that watches the address lines coming out from the
507 processor, and force it to stop if the address matches a breakpoint's
510 A third possibility is that the target already has the ability to do
511 breakpoints somehow; for instance, a ROM monitor may do its own
512 software breakpoints. So although these are not literally ``hardware
513 breakpoints'', from @value{GDBN}'s point of view they work the same;
514 @value{GDBN} need not do anything more than set the breakpoint and wait
515 for something to happen.
517 Since they depend on hardware resources, hardware breakpoints may be
518 limited in number; when the user asks for more, @value{GDBN} will
519 start trying to set software breakpoints. (On some architectures,
520 notably the 32-bit x86 platforms, @value{GDBN} cannot always know
521 whether there's enough hardware resources to insert all the hardware
522 breakpoints and watchpoints. On those platforms, @value{GDBN} prints
523 an error message only when the program being debugged is continued.)
525 @cindex software breakpoints
526 Software breakpoints require @value{GDBN} to do somewhat more work.
527 The basic theory is that @value{GDBN} will replace a program
528 instruction with a trap, illegal divide, or some other instruction
529 that will cause an exception, and then when it's encountered,
530 @value{GDBN} will take the exception and stop the program. When the
531 user says to continue, @value{GDBN} will restore the original
532 instruction, single-step, re-insert the trap, and continue on.
534 Since it literally overwrites the program being tested, the program area
535 must be writable, so this technique won't work on programs in ROM. It
536 can also distort the behavior of programs that examine themselves,
537 although such a situation would be highly unusual.
539 Also, the software breakpoint instruction should be the smallest size of
540 instruction, so it doesn't overwrite an instruction that might be a jump
541 target, and cause disaster when the program jumps into the middle of the
542 breakpoint instruction. (Strictly speaking, the breakpoint must be no
543 larger than the smallest interval between instructions that may be jump
544 targets; perhaps there is an architecture where only even-numbered
545 instructions may jumped to.) Note that it's possible for an instruction
546 set not to have any instructions usable for a software breakpoint,
547 although in practice only the ARC has failed to define such an
550 Basic breakpoint object handling is in @file{breakpoint.c}. However,
551 much of the interesting breakpoint action is in @file{infrun.c}.
554 @cindex insert or remove software breakpoint
555 @findex target_remove_breakpoint
556 @findex target_insert_breakpoint
557 @item target_remove_breakpoint (@var{bp_tgt})
558 @itemx target_insert_breakpoint (@var{bp_tgt})
559 Insert or remove a software breakpoint at address
560 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
561 non-zero for failure. On input, @var{bp_tgt} contains the address of the
562 breakpoint, and is otherwise initialized to zero. The fields of the
563 @code{struct bp_target_info} pointed to by @var{bp_tgt} are updated
564 to contain other information about the breakpoint on output. The field
565 @code{placed_address} may be updated if the breakpoint was placed at a
566 related address; the field @code{shadow_contents} contains the real
567 contents of the bytes where the breakpoint has been inserted,
568 if reading memory would return the breakpoint instead of the
569 underlying memory; the field @code{shadow_len} is the length of
570 memory cached in @code{shadow_contents}, if any; and the field
571 @code{placed_size} is optionally set and used by the target, if
572 it could differ from @code{shadow_len}.
574 For example, the remote target @samp{Z0} packet does not require
575 shadowing memory, so @code{shadow_len} is left at zero. However,
576 the length reported by @code{gdbarch_breakpoint_from_pc} is cached in
577 @code{placed_size}, so that a matching @samp{z0} packet can be
578 used to remove the breakpoint.
580 @cindex insert or remove hardware breakpoint
581 @findex target_remove_hw_breakpoint
582 @findex target_insert_hw_breakpoint
583 @item target_remove_hw_breakpoint (@var{bp_tgt})
584 @itemx target_insert_hw_breakpoint (@var{bp_tgt})
585 Insert or remove a hardware-assisted breakpoint at address
586 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
587 non-zero for failure. See @code{target_insert_breakpoint} for
588 a description of the @code{struct bp_target_info} pointed to by
589 @var{bp_tgt}; the @code{shadow_contents} and
590 @code{shadow_len} members are not used for hardware breakpoints,
591 but @code{placed_size} may be.
594 @section Single Stepping
596 @section Signal Handling
598 @section Thread Handling
600 @section Inferior Function Calls
602 @section Longjmp Support
604 @cindex @code{longjmp} debugging
605 @value{GDBN} has support for figuring out that the target is doing a
606 @code{longjmp} and for stopping at the target of the jump, if we are
607 stepping. This is done with a few specialized internal breakpoints,
608 which are visible in the output of the @samp{maint info breakpoint}
611 @findex gdbarch_get_longjmp_target
612 To make this work, you need to define a function called
613 @code{gdbarch_get_longjmp_target}, which will examine the
614 @code{jmp_buf} structure and extract the @code{longjmp} target address.
615 Since @code{jmp_buf} is target specific and typically defined in a
616 target header not available to @value{GDBN}, you will need to
617 determine the offset of the PC manually and return that; many targets
618 define a @code{jb_pc_offset} field in the tdep structure to save the
619 value once calculated.
624 Watchpoints are a special kind of breakpoints (@pxref{Algorithms,
625 breakpoints}) which break when data is accessed rather than when some
626 instruction is executed. When you have data which changes without
627 your knowing what code does that, watchpoints are the silver bullet to
628 hunt down and kill such bugs.
630 @cindex hardware watchpoints
631 @cindex software watchpoints
632 Watchpoints can be either hardware-assisted or not; the latter type is
633 known as ``software watchpoints.'' @value{GDBN} always uses
634 hardware-assisted watchpoints if they are available, and falls back on
635 software watchpoints otherwise. Typical situations where @value{GDBN}
636 will use software watchpoints are:
640 The watched memory region is too large for the underlying hardware
641 watchpoint support. For example, each x86 debug register can watch up
642 to 4 bytes of memory, so trying to watch data structures whose size is
643 more than 16 bytes will cause @value{GDBN} to use software
647 The value of the expression to be watched depends on data held in
648 registers (as opposed to memory).
651 Too many different watchpoints requested. (On some architectures,
652 this situation is impossible to detect until the debugged program is
653 resumed.) Note that x86 debug registers are used both for hardware
654 breakpoints and for watchpoints, so setting too many hardware
655 breakpoints might cause watchpoint insertion to fail.
658 No hardware-assisted watchpoints provided by the target
662 Software watchpoints are very slow, since @value{GDBN} needs to
663 single-step the program being debugged and test the value of the
664 watched expression(s) after each instruction. The rest of this
665 section is mostly irrelevant for software watchpoints.
667 When the inferior stops, @value{GDBN} tries to establish, among other
668 possible reasons, whether it stopped due to a watchpoint being hit.
669 It first uses @code{STOPPED_BY_WATCHPOINT} to see if any watchpoint
670 was hit. If not, all watchpoint checking is skipped.
672 Then @value{GDBN} calls @code{target_stopped_data_address} exactly
673 once. This method returns the address of the watchpoint which
674 triggered, if the target can determine it. If the triggered address
675 is available, @value{GDBN} compares the address returned by this
676 method with each watched memory address in each active watchpoint.
677 For data-read and data-access watchpoints, @value{GDBN} announces
678 every watchpoint that watches the triggered address as being hit.
679 For this reason, data-read and data-access watchpoints
680 @emph{require} that the triggered address be available; if not, read
681 and access watchpoints will never be considered hit. For data-write
682 watchpoints, if the triggered address is available, @value{GDBN}
683 considers only those watchpoints which match that address;
684 otherwise, @value{GDBN} considers all data-write watchpoints. For
685 each data-write watchpoint that @value{GDBN} considers, it evaluates
686 the expression whose value is being watched, and tests whether the
687 watched value has changed. Watchpoints whose watched values have
688 changed are announced as hit.
690 @c FIXME move these to the main lists of target/native defns
692 @value{GDBN} uses several macros and primitives to support hardware
696 @findex TARGET_CAN_USE_HARDWARE_WATCHPOINT
697 @item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other})
698 Return the number of hardware watchpoints of type @var{type} that are
699 possible to be set. The value is positive if @var{count} watchpoints
700 of this type can be set, zero if setting watchpoints of this type is
701 not supported, and negative if @var{count} is more than the maximum
702 number of watchpoints of type @var{type} that can be set. @var{other}
703 is non-zero if other types of watchpoints are currently enabled (there
704 are architectures which cannot set watchpoints of different types at
707 @findex TARGET_REGION_OK_FOR_HW_WATCHPOINT
708 @item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len})
709 Return non-zero if hardware watchpoints can be used to watch a region
710 whose address is @var{addr} and whose length in bytes is @var{len}.
712 @cindex insert or remove hardware watchpoint
713 @findex target_insert_watchpoint
714 @findex target_remove_watchpoint
715 @item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
716 @itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type})
717 Insert or remove a hardware watchpoint starting at @var{addr}, for
718 @var{len} bytes. @var{type} is the watchpoint type, one of the
719 possible values of the enumerated data type @code{target_hw_bp_type},
720 defined by @file{breakpoint.h} as follows:
723 enum target_hw_bp_type
725 hw_write = 0, /* Common (write) HW watchpoint */
726 hw_read = 1, /* Read HW watchpoint */
727 hw_access = 2, /* Access (read or write) HW watchpoint */
728 hw_execute = 3 /* Execute HW breakpoint */
733 These two macros should return 0 for success, non-zero for failure.
735 @findex target_stopped_data_address
736 @item target_stopped_data_address (@var{addr_p})
737 If the inferior has some watchpoint that triggered, place the address
738 associated with the watchpoint at the location pointed to by
739 @var{addr_p} and return non-zero. Otherwise, return zero. This
740 is required for data-read and data-access watchpoints. It is
741 not required for data-write watchpoints, but @value{GDBN} uses
742 it to improve handling of those also.
744 @value{GDBN} will only call this method once per watchpoint stop,
745 immediately after calling @code{STOPPED_BY_WATCHPOINT}. If the
746 target's watchpoint indication is sticky, i.e., stays set after
747 resuming, this method should clear it. For instance, the x86 debug
748 control register has sticky triggered flags.
750 @findex target_watchpoint_addr_within_range
751 @item target_watchpoint_addr_within_range (@var{target}, @var{addr}, @var{start}, @var{length})
752 Check whether @var{addr} (as returned by @code{target_stopped_data_address})
753 lies within the hardware-defined watchpoint region described by
754 @var{start} and @var{length}. This only needs to be provided if the
755 granularity of a watchpoint is greater than one byte, i.e., if the
756 watchpoint can also trigger on nearby addresses outside of the watched
759 @findex HAVE_STEPPABLE_WATCHPOINT
760 @item HAVE_STEPPABLE_WATCHPOINT
761 If defined to a non-zero value, it is not necessary to disable a
762 watchpoint to step over it. Like @code{gdbarch_have_nonsteppable_watchpoint},
763 this is usually set when watchpoints trigger at the instruction
764 which will perform an interesting read or write. It should be
765 set if there is a temporary disable bit which allows the processor
766 to step over the interesting instruction without raising the
767 watchpoint exception again.
769 @findex gdbarch_have_nonsteppable_watchpoint
770 @item int gdbarch_have_nonsteppable_watchpoint (@var{gdbarch})
771 If it returns a non-zero value, @value{GDBN} should disable a
772 watchpoint to step the inferior over it. This is usually set when
773 watchpoints trigger at the instruction which will perform an
774 interesting read or write.
776 @findex HAVE_CONTINUABLE_WATCHPOINT
777 @item HAVE_CONTINUABLE_WATCHPOINT
778 If defined to a non-zero value, it is possible to continue the
779 inferior after a watchpoint has been hit. This is usually set
780 when watchpoints trigger at the instruction following an interesting
783 @findex STOPPED_BY_WATCHPOINT
784 @item STOPPED_BY_WATCHPOINT (@var{wait_status})
785 Return non-zero if stopped by a watchpoint. @var{wait_status} is of
786 the type @code{struct target_waitstatus}, defined by @file{target.h}.
787 Normally, this macro is defined to invoke the function pointed to by
788 the @code{to_stopped_by_watchpoint} member of the structure (of the
789 type @code{target_ops}, defined on @file{target.h}) that describes the
790 target-specific operations; @code{to_stopped_by_watchpoint} ignores
791 the @var{wait_status} argument.
793 @value{GDBN} does not require the non-zero value returned by
794 @code{STOPPED_BY_WATCHPOINT} to be 100% correct, so if a target cannot
795 determine for sure whether the inferior stopped due to a watchpoint,
796 it could return non-zero ``just in case''.
799 @subsection Watchpoints and Threads
800 @cindex watchpoints, with threads
802 @value{GDBN} only supports process-wide watchpoints, which trigger
803 in all threads. @value{GDBN} uses the thread ID to make watchpoints
804 act as if they were thread-specific, but it cannot set hardware
805 watchpoints that only trigger in a specific thread. Therefore, even
806 if the target supports threads, per-thread debug registers, and
807 watchpoints which only affect a single thread, it should set the
808 per-thread debug registers for all threads to the same value. On
809 @sc{gnu}/Linux native targets, this is accomplished by using
810 @code{ALL_LWPS} in @code{target_insert_watchpoint} and
811 @code{target_remove_watchpoint} and by using
812 @code{linux_set_new_thread} to register a handler for newly created
815 @value{GDBN}'s @sc{gnu}/Linux support only reports a single event
816 at a time, although multiple events can trigger simultaneously for
817 multi-threaded programs. When multiple events occur, @file{linux-nat.c}
818 queues subsequent events and returns them the next time the program
819 is resumed. This means that @code{STOPPED_BY_WATCHPOINT} and
820 @code{target_stopped_data_address} only need to consult the current
821 thread's state---the thread indicated by @code{inferior_ptid}. If
822 two threads have hit watchpoints simultaneously, those routines
823 will be called a second time for the second thread.
825 @subsection x86 Watchpoints
826 @cindex x86 debug registers
827 @cindex watchpoints, on x86
829 The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug
830 registers designed to facilitate debugging. @value{GDBN} provides a
831 generic library of functions that x86-based ports can use to implement
832 support for watchpoints and hardware-assisted breakpoints. This
833 subsection documents the x86 watchpoint facilities in @value{GDBN}.
835 (At present, the library functions read and write debug registers directly, and are
836 thus only available for native configurations.)
838 To use the generic x86 watchpoint support, a port should do the
842 @findex I386_USE_GENERIC_WATCHPOINTS
844 Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the
845 target-dependent headers.
848 Include the @file{config/i386/nm-i386.h} header file @emph{after}
849 defining @code{I386_USE_GENERIC_WATCHPOINTS}.
852 Add @file{i386-nat.o} to the value of the Make variable
853 @code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}).
856 Provide implementations for the @code{I386_DR_LOW_*} macros described
857 below. Typically, each macro should call a target-specific function
858 which does the real work.
861 The x86 watchpoint support works by maintaining mirror images of the
862 debug registers. Values are copied between the mirror images and the
863 real debug registers via a set of macros which each target needs to
867 @findex I386_DR_LOW_SET_CONTROL
868 @item I386_DR_LOW_SET_CONTROL (@var{val})
869 Set the Debug Control (DR7) register to the value @var{val}.
871 @findex I386_DR_LOW_SET_ADDR
872 @item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr})
873 Put the address @var{addr} into the debug register number @var{idx}.
875 @findex I386_DR_LOW_RESET_ADDR
876 @item I386_DR_LOW_RESET_ADDR (@var{idx})
877 Reset (i.e.@: zero out) the address stored in the debug register
880 @findex I386_DR_LOW_GET_STATUS
881 @item I386_DR_LOW_GET_STATUS
882 Return the value of the Debug Status (DR6) register. This value is
883 used immediately after it is returned by
884 @code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status
888 For each one of the 4 debug registers (whose indices are from 0 to 3)
889 that store addresses, a reference count is maintained by @value{GDBN},
890 to allow sharing of debug registers by several watchpoints. This
891 allows users to define several watchpoints that watch the same
892 expression, but with different conditions and/or commands, without
893 wasting debug registers which are in short supply. @value{GDBN}
894 maintains the reference counts internally, targets don't have to do
895 anything to use this feature.
897 The x86 debug registers can each watch a region that is 1, 2, or 4
898 bytes long. The ia32 architecture requires that each watched region
899 be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte
900 region on 4-byte boundary. However, the x86 watchpoint support in
901 @value{GDBN} can watch unaligned regions and regions larger than 4
902 bytes (up to 16 bytes) by allocating several debug registers to watch
903 a single region. This allocation of several registers per a watched
904 region is also done automatically without target code intervention.
906 The generic x86 watchpoint support provides the following API for the
907 @value{GDBN}'s application code:
910 @findex i386_region_ok_for_watchpoint
911 @item i386_region_ok_for_watchpoint (@var{addr}, @var{len})
912 The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call
913 this function. It counts the number of debug registers required to
914 watch a given region, and returns a non-zero value if that number is
915 less than 4, the number of debug registers available to x86
918 @findex i386_stopped_data_address
919 @item i386_stopped_data_address (@var{addr_p})
921 @code{target_stopped_data_address} is set to call this function.
923 function examines the breakpoint condition bits in the DR6 Debug
924 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
925 macro, and returns the address associated with the first bit that is
928 @findex i386_stopped_by_watchpoint
929 @item i386_stopped_by_watchpoint (void)
930 The macro @code{STOPPED_BY_WATCHPOINT}
931 is set to call this function. The
932 argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This
933 function examines the breakpoint condition bits in the DR6 Debug
934 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
935 macro, and returns true if any bit is set. Otherwise, false is
938 @findex i386_insert_watchpoint
939 @findex i386_remove_watchpoint
940 @item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type})
941 @itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type})
942 Insert or remove a watchpoint. The macros
943 @code{target_insert_watchpoint} and @code{target_remove_watchpoint}
944 are set to call these functions. @code{i386_insert_watchpoint} first
945 looks for a debug register which is already set to watch the same
946 region for the same access types; if found, it just increments the
947 reference count of that debug register, thus implementing debug
948 register sharing between watchpoints. If no such register is found,
949 the function looks for a vacant debug register, sets its mirrored
950 value to @var{addr}, sets the mirrored value of DR7 Debug Control
951 register as appropriate for the @var{len} and @var{type} parameters,
952 and then passes the new values of the debug register and DR7 to the
953 inferior by calling @code{I386_DR_LOW_SET_ADDR} and
954 @code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is
955 required to cover the given region, the above process is repeated for
958 @code{i386_remove_watchpoint} does the opposite: it resets the address
959 in the mirrored value of the debug register and its read/write and
960 length bits in the mirrored value of DR7, then passes these new
961 values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and
962 @code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several
963 watchpoints, each time a @code{i386_remove_watchpoint} is called, it
964 decrements the reference count, and only calls
965 @code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when
966 the count goes to zero.
968 @findex i386_insert_hw_breakpoint
969 @findex i386_remove_hw_breakpoint
970 @item i386_insert_hw_breakpoint (@var{bp_tgt})
971 @itemx i386_remove_hw_breakpoint (@var{bp_tgt})
972 These functions insert and remove hardware-assisted breakpoints. The
973 macros @code{target_insert_hw_breakpoint} and
974 @code{target_remove_hw_breakpoint} are set to call these functions.
975 The argument is a @code{struct bp_target_info *}, as described in
976 the documentation for @code{target_insert_breakpoint}.
977 These functions work like @code{i386_insert_watchpoint} and
978 @code{i386_remove_watchpoint}, respectively, except that they set up
979 the debug registers to watch instruction execution, and each
980 hardware-assisted breakpoint always requires exactly one debug
983 @findex i386_cleanup_dregs
984 @item i386_cleanup_dregs (void)
985 This function clears all the reference counts, addresses, and control
986 bits in the mirror images of the debug registers. It doesn't affect
987 the actual debug registers in the inferior process.
994 x86 processors support setting watchpoints on I/O reads or writes.
995 However, since no target supports this (as of March 2001), and since
996 @code{enum target_hw_bp_type} doesn't even have an enumeration for I/O
997 watchpoints, this feature is not yet available to @value{GDBN} running
1001 x86 processors can enable watchpoints locally, for the current task
1002 only, or globally, for all the tasks. For each debug register,
1003 there's a bit in the DR7 Debug Control register that determines
1004 whether the associated address is watched locally or globally. The
1005 current implementation of x86 watchpoint support in @value{GDBN}
1006 always sets watchpoints to be locally enabled, since global
1007 watchpoints might interfere with the underlying OS and are probably
1008 unavailable in many platforms.
1011 @section Checkpoints
1014 In the abstract, a checkpoint is a point in the execution history of
1015 the program, which the user may wish to return to at some later time.
1017 Internally, a checkpoint is a saved copy of the program state, including
1018 whatever information is required in order to restore the program to that
1019 state at a later time. This can be expected to include the state of
1020 registers and memory, and may include external state such as the state
1021 of open files and devices.
1023 There are a number of ways in which checkpoints may be implemented
1024 in gdb, e.g.@: as corefiles, as forked processes, and as some opaque
1025 method implemented on the target side.
1027 A corefile can be used to save an image of target memory and register
1028 state, which can in principle be restored later --- but corefiles do
1029 not typically include information about external entities such as
1030 open files. Currently this method is not implemented in gdb.
1032 A forked process can save the state of user memory and registers,
1033 as well as some subset of external (kernel) state. This method
1034 is used to implement checkpoints on Linux, and in principle might
1035 be used on other systems.
1037 Some targets, e.g.@: simulators, might have their own built-in
1038 method for saving checkpoints, and gdb might be able to take
1039 advantage of that capability without necessarily knowing any
1040 details of how it is done.
1043 @section Observing changes in @value{GDBN} internals
1044 @cindex observer pattern interface
1045 @cindex notifications about changes in internals
1047 In order to function properly, several modules need to be notified when
1048 some changes occur in the @value{GDBN} internals. Traditionally, these
1049 modules have relied on several paradigms, the most common ones being
1050 hooks and gdb-events. Unfortunately, none of these paradigms was
1051 versatile enough to become the standard notification mechanism in
1052 @value{GDBN}. The fact that they only supported one ``client'' was also
1053 a strong limitation.
1055 A new paradigm, based on the Observer pattern of the @cite{Design
1056 Patterns} book, has therefore been implemented. The goal was to provide
1057 a new interface overcoming the issues with the notification mechanisms
1058 previously available. This new interface needed to be strongly typed,
1059 easy to extend, and versatile enough to be used as the standard
1060 interface when adding new notifications.
1062 See @ref{GDB Observers} for a brief description of the observers
1063 currently implemented in GDB. The rationale for the current
1064 implementation is also briefly discussed.
1066 @node User Interface
1068 @chapter User Interface
1070 @value{GDBN} has several user interfaces, of which the traditional
1071 command-line interface is perhaps the most familiar.
1073 @section Command Interpreter
1075 @cindex command interpreter
1077 The command interpreter in @value{GDBN} is fairly simple. It is designed to
1078 allow for the set of commands to be augmented dynamically, and also
1079 has a recursive subcommand capability, where the first argument to
1080 a command may itself direct a lookup on a different command list.
1082 For instance, the @samp{set} command just starts a lookup on the
1083 @code{setlist} command list, while @samp{set thread} recurses
1084 to the @code{set_thread_cmd_list}.
1088 To add commands in general, use @code{add_cmd}. @code{add_com} adds to
1089 the main command list, and should be used for those commands. The usual
1090 place to add commands is in the @code{_initialize_@var{xyz}} routines at
1091 the ends of most source files.
1093 @findex add_setshow_cmd
1094 @findex add_setshow_cmd_full
1095 To add paired @samp{set} and @samp{show} commands, use
1096 @code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is
1097 a slightly simpler interface which is useful when you don't need to
1098 further modify the new command structures, while the latter returns
1099 the new command structures for manipulation.
1101 @cindex deprecating commands
1102 @findex deprecate_cmd
1103 Before removing commands from the command set it is a good idea to
1104 deprecate them for some time. Use @code{deprecate_cmd} on commands or
1105 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
1106 @code{struct cmd_list_element} as it's first argument. You can use the
1107 return value from @code{add_com} or @code{add_cmd} to deprecate the
1108 command immediately after it is created.
1110 The first time a command is used the user will be warned and offered a
1111 replacement (if one exists). Note that the replacement string passed to
1112 @code{deprecate_cmd} should be the full name of the command, i.e., the
1113 entire string the user should type at the command line.
1115 @anchor{UI-Independent Output}
1116 @section UI-Independent Output---the @code{ui_out} Functions
1117 @c This section is based on the documentation written by Fernando
1118 @c Nasser <fnasser@redhat.com>.
1120 @cindex @code{ui_out} functions
1121 The @code{ui_out} functions present an abstraction level for the
1122 @value{GDBN} output code. They hide the specifics of different user
1123 interfaces supported by @value{GDBN}, and thus free the programmer
1124 from the need to write several versions of the same code, one each for
1125 every UI, to produce output.
1127 @subsection Overview and Terminology
1129 In general, execution of each @value{GDBN} command produces some sort
1130 of output, and can even generate an input request.
1132 Output can be generated for the following purposes:
1136 to display a @emph{result} of an operation;
1139 to convey @emph{info} or produce side-effects of a requested
1143 to provide a @emph{notification} of an asynchronous event (including
1144 progress indication of a prolonged asynchronous operation);
1147 to display @emph{error messages} (including warnings);
1150 to show @emph{debug data};
1153 to @emph{query} or prompt a user for input (a special case).
1157 This section mainly concentrates on how to build result output,
1158 although some of it also applies to other kinds of output.
1160 Generation of output that displays the results of an operation
1161 involves one or more of the following:
1165 output of the actual data
1168 formatting the output as appropriate for console output, to make it
1169 easily readable by humans
1172 machine oriented formatting--a more terse formatting to allow for easy
1173 parsing by programs which read @value{GDBN}'s output
1176 annotation, whose purpose is to help legacy GUIs to identify interesting
1180 The @code{ui_out} routines take care of the first three aspects.
1181 Annotations are provided by separate annotation routines. Note that use
1182 of annotations for an interface between a GUI and @value{GDBN} is
1185 Output can be in the form of a single item, which we call a @dfn{field};
1186 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
1187 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
1188 header and a body. In a BNF-like form:
1191 @item <table> @expansion{}
1192 @code{<header> <body>}
1193 @item <header> @expansion{}
1194 @code{@{ <column> @}}
1195 @item <column> @expansion{}
1196 @code{<width> <alignment> <title>}
1197 @item <body> @expansion{}
1202 @subsection General Conventions
1204 Most @code{ui_out} routines are of type @code{void}, the exceptions are
1205 @code{ui_out_stream_new} (which returns a pointer to the newly created
1206 object) and the @code{make_cleanup} routines.
1208 The first parameter is always the @code{ui_out} vector object, a pointer
1209 to a @code{struct ui_out}.
1211 The @var{format} parameter is like in @code{printf} family of functions.
1212 When it is present, there must also be a variable list of arguments
1213 sufficient used to satisfy the @code{%} specifiers in the supplied
1216 When a character string argument is not used in a @code{ui_out} function
1217 call, a @code{NULL} pointer has to be supplied instead.
1220 @subsection Table, Tuple and List Functions
1222 @cindex list output functions
1223 @cindex table output functions
1224 @cindex tuple output functions
1225 This section introduces @code{ui_out} routines for building lists,
1226 tuples and tables. The routines to output the actual data items
1227 (fields) are presented in the next section.
1229 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
1230 containing information about an object; a @dfn{list} is a sequence of
1231 fields where each field describes an identical object.
1233 Use the @dfn{table} functions when your output consists of a list of
1234 rows (tuples) and the console output should include a heading. Use this
1235 even when you are listing just one object but you still want the header.
1237 @cindex nesting level in @code{ui_out} functions
1238 Tables can not be nested. Tuples and lists can be nested up to a
1239 maximum of five levels.
1241 The overall structure of the table output code is something like this:
1256 Here is the description of table-, tuple- and list-related @code{ui_out}
1259 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
1260 The function @code{ui_out_table_begin} marks the beginning of the output
1261 of a table. It should always be called before any other @code{ui_out}
1262 function for a given table. @var{nbrofcols} is the number of columns in
1263 the table. @var{nr_rows} is the number of rows in the table.
1264 @var{tblid} is an optional string identifying the table. The string
1265 pointed to by @var{tblid} is copied by the implementation of
1266 @code{ui_out_table_begin}, so the application can free the string if it
1267 was @code{malloc}ed.
1269 The companion function @code{ui_out_table_end}, described below, marks
1270 the end of the table's output.
1273 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
1274 @code{ui_out_table_header} provides the header information for a single
1275 table column. You call this function several times, one each for every
1276 column of the table, after @code{ui_out_table_begin}, but before
1277 @code{ui_out_table_body}.
1279 The value of @var{width} gives the column width in characters. The
1280 value of @var{alignment} is one of @code{left}, @code{center}, and
1281 @code{right}, and it specifies how to align the header: left-justify,
1282 center, or right-justify it. @var{colhdr} points to a string that
1283 specifies the column header; the implementation copies that string, so
1284 column header strings in @code{malloc}ed storage can be freed after the
1288 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
1289 This function delimits the table header from the table body.
1292 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
1293 This function signals the end of a table's output. It should be called
1294 after the table body has been produced by the list and field output
1297 There should be exactly one call to @code{ui_out_table_end} for each
1298 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
1299 will signal an internal error.
1302 The output of the tuples that represent the table rows must follow the
1303 call to @code{ui_out_table_body} and precede the call to
1304 @code{ui_out_table_end}. You build a tuple by calling
1305 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
1306 calls to functions which actually output fields between them.
1308 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
1309 This function marks the beginning of a tuple output. @var{id} points
1310 to an optional string that identifies the tuple; it is copied by the
1311 implementation, and so strings in @code{malloc}ed storage can be freed
1315 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
1316 This function signals an end of a tuple output. There should be exactly
1317 one call to @code{ui_out_tuple_end} for each call to
1318 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
1322 @deftypefun {struct cleanup *} make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1323 This function first opens the tuple and then establishes a cleanup
1324 (@pxref{Misc Guidelines, Cleanups}) to close the tuple.
1325 It provides a convenient and correct implementation of the
1326 non-portable@footnote{The function cast is not portable ISO C.} code sequence:
1328 struct cleanup *old_cleanup;
1329 ui_out_tuple_begin (uiout, "...");
1330 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
1335 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
1336 This function marks the beginning of a list output. @var{id} points to
1337 an optional string that identifies the list; it is copied by the
1338 implementation, and so strings in @code{malloc}ed storage can be freed
1342 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
1343 This function signals an end of a list output. There should be exactly
1344 one call to @code{ui_out_list_end} for each call to
1345 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
1349 @deftypefun {struct cleanup *} make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1350 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
1351 opens a list and then establishes cleanup
1352 (@pxref{Misc Guidelines, Cleanups})
1353 that will close the list.
1356 @subsection Item Output Functions
1358 @cindex item output functions
1359 @cindex field output functions
1361 The functions described below produce output for the actual data
1362 items, or fields, which contain information about the object.
1364 Choose the appropriate function accordingly to your particular needs.
1366 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
1367 This is the most general output function. It produces the
1368 representation of the data in the variable-length argument list
1369 according to formatting specifications in @var{format}, a
1370 @code{printf}-like format string. The optional argument @var{fldname}
1371 supplies the name of the field. The data items themselves are
1372 supplied as additional arguments after @var{format}.
1374 This generic function should be used only when it is not possible to
1375 use one of the specialized versions (see below).
1378 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1379 This function outputs a value of an @code{int} variable. It uses the
1380 @code{"%d"} output conversion specification. @var{fldname} specifies
1381 the name of the field.
1384 @deftypefun void ui_out_field_fmt_int (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{fldname}, int @var{value})
1385 This function outputs a value of an @code{int} variable. It differs from
1386 @code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output.
1387 @var{fldname} specifies
1388 the name of the field.
1391 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, struct gdbarch *@var{gdbarch}, CORE_ADDR @var{address})
1392 This function outputs an address as appropriate for @var{gdbarch}.
1395 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1396 This function outputs a string using the @code{"%s"} conversion
1400 Sometimes, there's a need to compose your output piece by piece using
1401 functions that operate on a stream, such as @code{value_print} or
1402 @code{fprintf_symbol_filtered}. These functions accept an argument of
1403 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1404 used to store the data stream used for the output. When you use one
1405 of these functions, you need a way to pass their results stored in a
1406 @code{ui_file} object to the @code{ui_out} functions. To this end,
1407 you first create a @code{ui_stream} object by calling
1408 @code{ui_out_stream_new}, pass the @code{stream} member of that
1409 @code{ui_stream} object to @code{value_print} and similar functions,
1410 and finally call @code{ui_out_field_stream} to output the field you
1411 constructed. When the @code{ui_stream} object is no longer needed,
1412 you should destroy it and free its memory by calling
1413 @code{ui_out_stream_delete}.
1415 @deftypefun {struct ui_stream *} ui_out_stream_new (struct ui_out *@var{uiout})
1416 This function creates a new @code{ui_stream} object which uses the
1417 same output methods as the @code{ui_out} object whose pointer is
1418 passed in @var{uiout}. It returns a pointer to the newly created
1419 @code{ui_stream} object.
1422 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1423 This functions destroys a @code{ui_stream} object specified by
1427 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1428 This function consumes all the data accumulated in
1429 @code{streambuf->stream} and outputs it like
1430 @code{ui_out_field_string} does. After a call to
1431 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1432 the stream is still valid and may be used for producing more fields.
1435 @strong{Important:} If there is any chance that your code could bail
1436 out before completing output generation and reaching the point where
1437 @code{ui_out_stream_delete} is called, it is necessary to set up a
1438 cleanup, to avoid leaking memory and other resources. Here's a
1439 skeleton code to do that:
1442 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1443 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1448 If the function already has the old cleanup chain set (for other kinds
1449 of cleanups), you just have to add your cleanup to it:
1452 mybuf = ui_out_stream_new (uiout);
1453 make_cleanup (ui_out_stream_delete, mybuf);
1456 Note that with cleanups in place, you should not call
1457 @code{ui_out_stream_delete} directly, or you would attempt to free the
1460 @subsection Utility Output Functions
1462 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1463 This function skips a field in a table. Use it if you have to leave
1464 an empty field without disrupting the table alignment. The argument
1465 @var{fldname} specifies a name for the (missing) filed.
1468 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1469 This function outputs the text in @var{string} in a way that makes it
1470 easy to be read by humans. For example, the console implementation of
1471 this method filters the text through a built-in pager, to prevent it
1472 from scrolling off the visible portion of the screen.
1474 Use this function for printing relatively long chunks of text around
1475 the actual field data: the text it produces is not aligned according
1476 to the table's format. Use @code{ui_out_field_string} to output a
1477 string field, and use @code{ui_out_message}, described below, to
1478 output short messages.
1481 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1482 This function outputs @var{nspaces} spaces. It is handy to align the
1483 text produced by @code{ui_out_text} with the rest of the table or
1487 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1488 This function produces a formatted message, provided that the current
1489 verbosity level is at least as large as given by @var{verbosity}. The
1490 current verbosity level is specified by the user with the @samp{set
1491 verbositylevel} command.@footnote{As of this writing (April 2001),
1492 setting verbosity level is not yet implemented, and is always returned
1493 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1494 argument more than zero will cause the message to never be printed.}
1497 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1498 This function gives the console output filter (a paging filter) a hint
1499 of where to break lines which are too long. Ignored for all other
1500 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1501 be printed to indent the wrapped text on the next line; it must remain
1502 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1503 explicit newline is produced by one of the other functions. If
1504 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1507 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1508 This function flushes whatever output has been accumulated so far, if
1509 the UI buffers output.
1513 @subsection Examples of Use of @code{ui_out} functions
1515 @cindex using @code{ui_out} functions
1516 @cindex @code{ui_out} functions, usage examples
1517 This section gives some practical examples of using the @code{ui_out}
1518 functions to generalize the old console-oriented code in
1519 @value{GDBN}. The examples all come from functions defined on the
1520 @file{breakpoints.c} file.
1522 This example, from the @code{breakpoint_1} function, shows how to
1525 The original code was:
1528 if (!found_a_breakpoint++)
1530 annotate_breakpoints_headers ();
1533 printf_filtered ("Num ");
1535 printf_filtered ("Type ");
1537 printf_filtered ("Disp ");
1539 printf_filtered ("Enb ");
1543 printf_filtered ("Address ");
1546 printf_filtered ("What\n");
1548 annotate_breakpoints_table ();
1552 Here's the new version:
1555 nr_printable_breakpoints = @dots{};
1558 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1560 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1562 if (nr_printable_breakpoints > 0)
1563 annotate_breakpoints_headers ();
1564 if (nr_printable_breakpoints > 0)
1566 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1567 if (nr_printable_breakpoints > 0)
1569 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1570 if (nr_printable_breakpoints > 0)
1572 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1573 if (nr_printable_breakpoints > 0)
1575 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1578 if (nr_printable_breakpoints > 0)
1580 if (print_address_bits <= 32)
1581 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1583 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1585 if (nr_printable_breakpoints > 0)
1587 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1588 ui_out_table_body (uiout);
1589 if (nr_printable_breakpoints > 0)
1590 annotate_breakpoints_table ();
1593 This example, from the @code{print_one_breakpoint} function, shows how
1594 to produce the actual data for the table whose structure was defined
1595 in the above example. The original code was:
1600 printf_filtered ("%-3d ", b->number);
1602 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1603 || ((int) b->type != bptypes[(int) b->type].type))
1604 internal_error ("bptypes table does not describe type #%d.",
1606 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1608 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1610 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1614 This is the new version:
1618 ui_out_tuple_begin (uiout, "bkpt");
1620 ui_out_field_int (uiout, "number", b->number);
1622 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1623 || ((int) b->type != bptypes[(int) b->type].type))
1624 internal_error ("bptypes table does not describe type #%d.",
1626 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1628 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1630 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1634 This example, also from @code{print_one_breakpoint}, shows how to
1635 produce a complicated output field using the @code{print_expression}
1636 functions which requires a stream to be passed. It also shows how to
1637 automate stream destruction with cleanups. The original code was:
1641 print_expression (b->exp, gdb_stdout);
1647 struct ui_stream *stb = ui_out_stream_new (uiout);
1648 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1651 print_expression (b->exp, stb->stream);
1652 ui_out_field_stream (uiout, "what", local_stream);
1655 This example, also from @code{print_one_breakpoint}, shows how to use
1656 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1661 if (b->dll_pathname == NULL)
1662 printf_filtered ("<any library> ");
1664 printf_filtered ("library \"%s\" ", b->dll_pathname);
1671 if (b->dll_pathname == NULL)
1673 ui_out_field_string (uiout, "what", "<any library>");
1674 ui_out_spaces (uiout, 1);
1678 ui_out_text (uiout, "library \"");
1679 ui_out_field_string (uiout, "what", b->dll_pathname);
1680 ui_out_text (uiout, "\" ");
1684 The following example from @code{print_one_breakpoint} shows how to
1685 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1690 if (b->forked_inferior_pid != 0)
1691 printf_filtered ("process %d ", b->forked_inferior_pid);
1698 if (b->forked_inferior_pid != 0)
1700 ui_out_text (uiout, "process ");
1701 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1702 ui_out_spaces (uiout, 1);
1706 Here's an example of using @code{ui_out_field_string}. The original
1711 if (b->exec_pathname != NULL)
1712 printf_filtered ("program \"%s\" ", b->exec_pathname);
1719 if (b->exec_pathname != NULL)
1721 ui_out_text (uiout, "program \"");
1722 ui_out_field_string (uiout, "what", b->exec_pathname);
1723 ui_out_text (uiout, "\" ");
1727 Finally, here's an example of printing an address. The original code:
1731 printf_filtered ("%s ",
1732 hex_string_custom ((unsigned long) b->address, 8));
1739 ui_out_field_core_addr (uiout, "Address", b->address);
1743 @section Console Printing
1752 @cindex @code{libgdb}
1753 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1754 to provide an API to @value{GDBN}'s functionality.
1757 @cindex @code{libgdb}
1758 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1759 better able to support graphical and other environments.
1761 Since @code{libgdb} development is on-going, its architecture is still
1762 evolving. The following components have so far been identified:
1766 Observer - @file{gdb-events.h}.
1768 Builder - @file{ui-out.h}
1770 Event Loop - @file{event-loop.h}
1772 Library - @file{gdb.h}
1775 The model that ties these components together is described below.
1777 @section The @code{libgdb} Model
1779 A client of @code{libgdb} interacts with the library in two ways.
1783 As an observer (using @file{gdb-events}) receiving notifications from
1784 @code{libgdb} of any internal state changes (break point changes, run
1787 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1788 obtain various status values from @value{GDBN}.
1791 Since @code{libgdb} could have multiple clients (e.g., a GUI supporting
1792 the existing @value{GDBN} CLI), those clients must co-operate when
1793 controlling @code{libgdb}. In particular, a client must ensure that
1794 @code{libgdb} is idle (i.e.@: no other client is using @code{libgdb})
1795 before responding to a @file{gdb-event} by making a query.
1797 @section CLI support
1799 At present @value{GDBN}'s CLI is very much entangled in with the core of
1800 @code{libgdb}. Consequently, a client wishing to include the CLI in
1801 their interface needs to carefully co-ordinate its own and the CLI's
1804 It is suggested that the client set @code{libgdb} up to be bi-modal
1805 (alternate between CLI and client query modes). The notes below sketch
1810 The client registers itself as an observer of @code{libgdb}.
1812 The client create and install @code{cli-out} builder using its own
1813 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1814 @code{gdb_stdout} streams.
1816 The client creates a separate custom @code{ui-out} builder that is only
1817 used while making direct queries to @code{libgdb}.
1820 When the client receives input intended for the CLI, it simply passes it
1821 along. Since the @code{cli-out} builder is installed by default, all
1822 the CLI output in response to that command is routed (pronounced rooted)
1823 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1824 At the same time, the client is kept abreast of internal changes by
1825 virtue of being a @code{libgdb} observer.
1827 The only restriction on the client is that it must wait until
1828 @code{libgdb} becomes idle before initiating any queries (using the
1829 client's custom builder).
1831 @section @code{libgdb} components
1833 @subheading Observer - @file{gdb-events.h}
1834 @file{gdb-events} provides the client with a very raw mechanism that can
1835 be used to implement an observer. At present it only allows for one
1836 observer and that observer must, internally, handle the need to delay
1837 the processing of any event notifications until after @code{libgdb} has
1838 finished the current command.
1840 @subheading Builder - @file{ui-out.h}
1841 @file{ui-out} provides the infrastructure necessary for a client to
1842 create a builder. That builder is then passed down to @code{libgdb}
1843 when doing any queries.
1845 @subheading Event Loop - @file{event-loop.h}
1846 @c There could be an entire section on the event-loop
1847 @file{event-loop}, currently non-re-entrant, provides a simple event
1848 loop. A client would need to either plug its self into this loop or,
1849 implement a new event-loop that @value{GDBN} would use.
1851 The event-loop will eventually be made re-entrant. This is so that
1852 @value{GDBN} can better handle the problem of some commands blocking
1853 instead of returning.
1855 @subheading Library - @file{gdb.h}
1856 @file{libgdb} is the most obvious component of this system. It provides
1857 the query interface. Each function is parameterized by a @code{ui-out}
1858 builder. The result of the query is constructed using that builder
1859 before the query function returns.
1866 @cindex @code{value} structure
1867 @value{GDBN} uses @code{struct value}, or @dfn{values}, as an internal
1868 abstraction for the representation of a variety of inferior objects
1869 and @value{GDBN} convenience objects.
1871 Values have an associated @code{struct type}, that describes a virtual
1872 view of the raw data or object stored in or accessed through the
1875 A value is in addition discriminated by its lvalue-ness, given its
1876 @code{enum lval_type} enumeration type:
1878 @cindex @code{lval_type} enumeration, for values.
1880 @item @code{not_lval}
1881 This value is not an lval. It can't be assigned to.
1883 @item @code{lval_memory}
1884 This value represents an object in memory.
1886 @item @code{lval_register}
1887 This value represents an object that lives in a register.
1889 @item @code{lval_internalvar}
1890 Represents the value of an internal variable.
1892 @item @code{lval_internalvar_component}
1893 Represents part of a @value{GDBN} internal variable. E.g., a
1896 @cindex computed values
1897 @item @code{lval_computed}
1898 These are ``computed'' values. They allow creating specialized value
1899 objects for specific purposes, all abstracted away from the core value
1900 support code. The creator of such a value writes specialized
1901 functions to handle the reading and writing to/from the value's
1902 backend data, and optionally, a ``copy operator'' and a
1905 Pointers to these functions are stored in a @code{struct lval_funcs}
1906 instance (declared in @file{value.h}), and passed to the
1907 @code{allocate_computed_value} function, as in the example below.
1911 nil_value_read (struct value *v)
1913 /* This callback reads data from some backend, and stores it in V.
1914 In this case, we always read null data. You'll want to fill in
1915 something more interesting. */
1917 memset (value_contents_all_raw (v),
1919 TYPE_LENGTH (value_type (v)));
1923 nil_value_write (struct value *v, struct value *fromval)
1925 /* Takes the data from FROMVAL and stores it in the backend of V. */
1927 to_oblivion (value_contents_all_raw (fromval),
1929 TYPE_LENGTH (value_type (fromval)));
1932 static struct lval_funcs nil_value_funcs =
1939 make_nil_value (void)
1944 type = make_nils_type ();
1945 v = allocate_computed_value (type, &nil_value_funcs, NULL);
1951 See the implementation of the @code{$_siginfo} convenience variable in
1952 @file{infrun.c} as a real example use of lval_computed.
1957 @chapter Stack Frames
1960 @cindex call stack frame
1961 A frame is a construct that @value{GDBN} uses to keep track of calling
1962 and called functions.
1964 @cindex unwind frame
1965 @value{GDBN}'s frame model, a fresh design, was implemented with the
1966 need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
1967 the term ``unwind'' is taken directly from that specification.
1968 Developers wishing to learn more about unwinders, are encouraged to
1969 read the @sc{dwarf} specification, available from
1970 @url{http://www.dwarfstd.org}.
1972 @findex frame_register_unwind
1973 @findex get_frame_register
1974 @value{GDBN}'s model is that you find a frame's registers by
1975 ``unwinding'' them from the next younger frame. That is,
1976 @samp{get_frame_register} which returns the value of a register in
1977 frame #1 (the next-to-youngest frame), is implemented by calling frame
1978 #0's @code{frame_register_unwind} (the youngest frame). But then the
1979 obvious question is: how do you access the registers of the youngest
1982 @cindex sentinel frame
1983 @findex get_frame_type
1984 @vindex SENTINEL_FRAME
1985 To answer this question, @value{GDBN} has the @dfn{sentinel} frame, the
1986 ``-1st'' frame. Unwinding registers from the sentinel frame gives you
1987 the current values of the youngest real frame's registers. If @var{f}
1988 is a sentinel frame, then @code{get_frame_type (@var{f}) @equiv{}
1991 @section Selecting an Unwinder
1993 @findex frame_unwind_prepend_unwinder
1994 @findex frame_unwind_append_unwinder
1995 The architecture registers a list of frame unwinders (@code{struct
1996 frame_unwind}), using the functions
1997 @code{frame_unwind_prepend_unwinder} and
1998 @code{frame_unwind_append_unwinder}. Each unwinder includes a
1999 sniffer. Whenever @value{GDBN} needs to unwind a frame (to fetch the
2000 previous frame's registers or the current frame's ID), it calls
2001 registered sniffers in order to find one which recognizes the frame.
2002 The first time a sniffer returns non-zero, the corresponding unwinder
2003 is assigned to the frame.
2005 @section Unwinding the Frame ID
2008 Every frame has an associated ID, of type @code{struct frame_id}.
2009 The ID includes the stack base and function start address for
2010 the frame. The ID persists through the entire life of the frame,
2011 including while other called frames are running; it is used to
2012 locate an appropriate @code{struct frame_info} from the cache.
2014 Every time the inferior stops, and at various other times, the frame
2015 cache is flushed. Because of this, parts of @value{GDBN} which need
2016 to keep track of individual frames cannot use pointers to @code{struct
2017 frame_info}. A frame ID provides a stable reference to a frame, even
2018 when the unwinder must be run again to generate a new @code{struct
2019 frame_info} for the same frame.
2021 The frame's unwinder's @code{this_id} method is called to find the ID.
2022 Note that this is different from register unwinding, where the next
2023 frame's @code{prev_register} is called to unwind this frame's
2026 Both stack base and function address are required to identify the
2027 frame, because a recursive function has the same function address for
2028 two consecutive frames and a leaf function may have the same stack
2029 address as its caller. On some platforms, a third address is part of
2030 the ID to further disambiguate frames---for instance, on IA-64
2031 the separate register stack address is included in the ID.
2033 An invalid frame ID (@code{outer_frame_id}) returned from the
2034 @code{this_id} method means to stop unwinding after this frame.
2036 @code{null_frame_id} is another invalid frame ID which should be used
2037 when there is no frame. For instance, certain breakpoints are attached
2038 to a specific frame, and that frame is identified through its frame ID
2039 (we use this to implement the "finish" command). Using
2040 @code{null_frame_id} as the frame ID for a given breakpoint means
2041 that the breakpoint is not specific to any frame. The @code{this_id}
2042 method should never return @code{null_frame_id}.
2044 @section Unwinding Registers
2046 Each unwinder includes a @code{prev_register} method. This method
2047 takes a frame, an associated cache pointer, and a register number.
2048 It returns a @code{struct value *} describing the requested register,
2049 as saved by this frame. This is the value of the register that is
2050 current in this frame's caller.
2052 The returned value must have the same type as the register. It may
2053 have any lvalue type. In most circumstances one of these routines
2054 will generate the appropriate value:
2057 @item frame_unwind_got_optimized
2058 @findex frame_unwind_got_optimized
2059 This register was not saved.
2061 @item frame_unwind_got_register
2062 @findex frame_unwind_got_register
2063 This register was copied into another register in this frame. This
2064 is also used for unchanged registers; they are ``copied'' into the
2067 @item frame_unwind_got_memory
2068 @findex frame_unwind_got_memory
2069 This register was saved in memory.
2071 @item frame_unwind_got_constant
2072 @findex frame_unwind_got_constant
2073 This register was not saved, but the unwinder can compute the previous
2074 value some other way.
2076 @item frame_unwind_got_address
2077 @findex frame_unwind_got_address
2078 Same as @code{frame_unwind_got_constant}, except that the value is a target
2079 address. This is frequently used for the stack pointer, which is not
2080 explicitly saved but has a known offset from this frame's stack
2081 pointer. For architectures with a flat unified address space, this is
2082 generally the same as @code{frame_unwind_got_constant}.
2085 @node Symbol Handling
2087 @chapter Symbol Handling
2089 Symbols are a key part of @value{GDBN}'s operation. Symbols include
2090 variables, functions, and types.
2092 Symbol information for a large program can be truly massive, and
2093 reading of symbol information is one of the major performance
2094 bottlenecks in @value{GDBN}; it can take many minutes to process it
2095 all. Studies have shown that nearly all the time spent is
2096 computational, rather than file reading.
2098 One of the ways for @value{GDBN} to provide a good user experience is
2099 to start up quickly, taking no more than a few seconds. It is simply
2100 not possible to process all of a program's debugging info in that
2101 time, and so we attempt to handle symbols incrementally. For instance,
2102 we create @dfn{partial symbol tables} consisting of only selected
2103 symbols, and only expand them to full symbol tables when necessary.
2105 @section Symbol Reading
2107 @cindex symbol reading
2108 @cindex reading of symbols
2109 @cindex symbol files
2110 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
2111 file is the file containing the program which @value{GDBN} is
2112 debugging. @value{GDBN} can be directed to use a different file for
2113 symbols (with the @samp{symbol-file} command), and it can also read
2114 more symbols via the @samp{add-file} and @samp{load} commands. In
2115 addition, it may bring in more symbols while loading shared
2118 @findex find_sym_fns
2119 Symbol files are initially opened by code in @file{symfile.c} using
2120 the BFD library (@pxref{Support Libraries}). BFD identifies the type
2121 of the file by examining its header. @code{find_sym_fns} then uses
2122 this identification to locate a set of symbol-reading functions.
2124 @findex add_symtab_fns
2125 @cindex @code{sym_fns} structure
2126 @cindex adding a symbol-reading module
2127 Symbol-reading modules identify themselves to @value{GDBN} by calling
2128 @code{add_symtab_fns} during their module initialization. The argument
2129 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
2130 name (or name prefix) of the symbol format, the length of the prefix,
2131 and pointers to four functions. These functions are called at various
2132 times to process symbol files whose identification matches the specified
2135 The functions supplied by each module are:
2138 @item @var{xyz}_symfile_init(struct sym_fns *sf)
2140 @cindex secondary symbol file
2141 Called from @code{symbol_file_add} when we are about to read a new
2142 symbol file. This function should clean up any internal state (possibly
2143 resulting from half-read previous files, for example) and prepare to
2144 read a new symbol file. Note that the symbol file which we are reading
2145 might be a new ``main'' symbol file, or might be a secondary symbol file
2146 whose symbols are being added to the existing symbol table.
2148 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
2149 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
2150 new symbol file being read. Its @code{private} field has been zeroed,
2151 and can be modified as desired. Typically, a struct of private
2152 information will be @code{malloc}'d, and a pointer to it will be placed
2153 in the @code{private} field.
2155 There is no result from @code{@var{xyz}_symfile_init}, but it can call
2156 @code{error} if it detects an unavoidable problem.
2158 @item @var{xyz}_new_init()
2160 Called from @code{symbol_file_add} when discarding existing symbols.
2161 This function needs only handle the symbol-reading module's internal
2162 state; the symbol table data structures visible to the rest of
2163 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
2164 arguments and no result. It may be called after
2165 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
2166 may be called alone if all symbols are simply being discarded.
2168 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
2170 Called from @code{symbol_file_add} to actually read the symbols from a
2171 symbol-file into a set of psymtabs or symtabs.
2173 @code{sf} points to the @code{struct sym_fns} originally passed to
2174 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
2175 the offset between the file's specified start address and its true
2176 address in memory. @code{mainline} is 1 if this is the main symbol
2177 table being read, and 0 if a secondary symbol file (e.g., shared library
2178 or dynamically loaded file) is being read.@refill
2181 In addition, if a symbol-reading module creates psymtabs when
2182 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
2183 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
2184 from any point in the @value{GDBN} symbol-handling code.
2187 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
2189 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
2190 the psymtab has not already been read in and had its @code{pst->symtab}
2191 pointer set. The argument is the psymtab to be fleshed-out into a
2192 symtab. Upon return, @code{pst->readin} should have been set to 1, and
2193 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
2194 zero if there were no symbols in that part of the symbol file.
2197 @section Partial Symbol Tables
2199 @value{GDBN} has three types of symbol tables:
2202 @cindex full symbol table
2205 Full symbol tables (@dfn{symtabs}). These contain the main
2206 information about symbols and addresses.
2210 Partial symbol tables (@dfn{psymtabs}). These contain enough
2211 information to know when to read the corresponding part of the full
2214 @cindex minimal symbol table
2217 Minimal symbol tables (@dfn{msymtabs}). These contain information
2218 gleaned from non-debugging symbols.
2221 @cindex partial symbol table
2222 This section describes partial symbol tables.
2224 A psymtab is constructed by doing a very quick pass over an executable
2225 file's debugging information. Small amounts of information are
2226 extracted---enough to identify which parts of the symbol table will
2227 need to be re-read and fully digested later, when the user needs the
2228 information. The speed of this pass causes @value{GDBN} to start up very
2229 quickly. Later, as the detailed rereading occurs, it occurs in small
2230 pieces, at various times, and the delay therefrom is mostly invisible to
2232 @c (@xref{Symbol Reading}.)
2234 The symbols that show up in a file's psymtab should be, roughly, those
2235 visible to the debugger's user when the program is not running code from
2236 that file. These include external symbols and types, static symbols and
2237 types, and @code{enum} values declared at file scope.
2239 The psymtab also contains the range of instruction addresses that the
2240 full symbol table would represent.
2242 @cindex finding a symbol
2243 @cindex symbol lookup
2244 The idea is that there are only two ways for the user (or much of the
2245 code in the debugger) to reference a symbol:
2248 @findex find_pc_function
2249 @findex find_pc_line
2251 By its address (e.g., execution stops at some address which is inside a
2252 function in this file). The address will be noticed to be in the
2253 range of this psymtab, and the full symtab will be read in.
2254 @code{find_pc_function}, @code{find_pc_line}, and other
2255 @code{find_pc_@dots{}} functions handle this.
2257 @cindex lookup_symbol
2260 (e.g., the user asks to print a variable, or set a breakpoint on a
2261 function). Global names and file-scope names will be found in the
2262 psymtab, which will cause the symtab to be pulled in. Local names will
2263 have to be qualified by a global name, or a file-scope name, in which
2264 case we will have already read in the symtab as we evaluated the
2265 qualifier. Or, a local symbol can be referenced when we are ``in'' a
2266 local scope, in which case the first case applies. @code{lookup_symbol}
2267 does most of the work here.
2270 The only reason that psymtabs exist is to cause a symtab to be read in
2271 at the right moment. Any symbol that can be elided from a psymtab,
2272 while still causing that to happen, should not appear in it. Since
2273 psymtabs don't have the idea of scope, you can't put local symbols in
2274 them anyway. Psymtabs don't have the idea of the type of a symbol,
2275 either, so types need not appear, unless they will be referenced by
2278 It is a bug for @value{GDBN} to behave one way when only a psymtab has
2279 been read, and another way if the corresponding symtab has been read
2280 in. Such bugs are typically caused by a psymtab that does not contain
2281 all the visible symbols, or which has the wrong instruction address
2284 The psymtab for a particular section of a symbol file (objfile) could be
2285 thrown away after the symtab has been read in. The symtab should always
2286 be searched before the psymtab, so the psymtab will never be used (in a
2287 bug-free environment). Currently, psymtabs are allocated on an obstack,
2288 and all the psymbols themselves are allocated in a pair of large arrays
2289 on an obstack, so there is little to be gained by trying to free them
2290 unless you want to do a lot more work.
2292 Whether or not psymtabs are created depends on the objfile's symbol
2293 reader. The core of @value{GDBN} hides the details of partial symbols
2294 and partial symbol tables behind a set of function pointers known as
2295 the @dfn{quick symbol functions}. These are documented in
2300 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
2302 @cindex fundamental types
2303 These are the fundamental types that @value{GDBN} uses internally. Fundamental
2304 types from the various debugging formats (stabs, ELF, etc) are mapped
2305 into one of these. They are basically a union of all fundamental types
2306 that @value{GDBN} knows about for all the languages that @value{GDBN}
2309 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
2312 Each time @value{GDBN} builds an internal type, it marks it with one
2313 of these types. The type may be a fundamental type, such as
2314 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
2315 which is a pointer to another type. Typically, several @code{FT_*}
2316 types map to one @code{TYPE_CODE_*} type, and are distinguished by
2317 other members of the type struct, such as whether the type is signed
2318 or unsigned, and how many bits it uses.
2320 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
2322 These are instances of type structs that roughly correspond to
2323 fundamental types and are created as global types for @value{GDBN} to
2324 use for various ugly historical reasons. We eventually want to
2325 eliminate these. Note for example that @code{builtin_type_int}
2326 initialized in @file{gdbtypes.c} is basically the same as a
2327 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
2328 an @code{FT_INTEGER} fundamental type. The difference is that the
2329 @code{builtin_type} is not associated with any particular objfile, and
2330 only one instance exists, while @file{c-lang.c} builds as many
2331 @code{TYPE_CODE_INT} types as needed, with each one associated with
2332 some particular objfile.
2334 @section Object File Formats
2335 @cindex object file formats
2339 @cindex @code{a.out} format
2340 The @code{a.out} format is the original file format for Unix. It
2341 consists of three sections: @code{text}, @code{data}, and @code{bss},
2342 which are for program code, initialized data, and uninitialized data,
2345 The @code{a.out} format is so simple that it doesn't have any reserved
2346 place for debugging information. (Hey, the original Unix hackers used
2347 @samp{adb}, which is a machine-language debugger!) The only debugging
2348 format for @code{a.out} is stabs, which is encoded as a set of normal
2349 symbols with distinctive attributes.
2351 The basic @code{a.out} reader is in @file{dbxread.c}.
2356 The COFF format was introduced with System V Release 3 (SVR3) Unix.
2357 COFF files may have multiple sections, each prefixed by a header. The
2358 number of sections is limited.
2360 The COFF specification includes support for debugging. Although this
2361 was a step forward, the debugging information was woefully limited.
2362 For instance, it was not possible to represent code that came from an
2363 included file. GNU's COFF-using configs often use stabs-type info,
2364 encapsulated in special sections.
2366 The COFF reader is in @file{coffread.c}.
2370 @cindex ECOFF format
2371 ECOFF is an extended COFF originally introduced for Mips and Alpha
2374 The basic ECOFF reader is in @file{mipsread.c}.
2378 @cindex XCOFF format
2379 The IBM RS/6000 running AIX uses an object file format called XCOFF.
2380 The COFF sections, symbols, and line numbers are used, but debugging
2381 symbols are @code{dbx}-style stabs whose strings are located in the
2382 @code{.debug} section (rather than the string table). For more
2383 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
2385 The shared library scheme has a clean interface for figuring out what
2386 shared libraries are in use, but the catch is that everything which
2387 refers to addresses (symbol tables and breakpoints at least) needs to be
2388 relocated for both shared libraries and the main executable. At least
2389 using the standard mechanism this can only be done once the program has
2390 been run (or the core file has been read).
2394 @cindex PE-COFF format
2395 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
2396 executables. PE is basically COFF with additional headers.
2398 While BFD includes special PE support, @value{GDBN} needs only the basic
2404 The ELF format came with System V Release 4 (SVR4) Unix. ELF is
2405 similar to COFF in being organized into a number of sections, but it
2406 removes many of COFF's limitations. Debugging info may be either stabs
2407 encapsulated in ELF sections, or more commonly these days, DWARF.
2409 The basic ELF reader is in @file{elfread.c}.
2414 SOM is HP's object file and debug format (not to be confused with IBM's
2415 SOM, which is a cross-language ABI).
2417 The SOM reader is in @file{somread.c}.
2419 @section Debugging File Formats
2421 This section describes characteristics of debugging information that
2422 are independent of the object file format.
2426 @cindex stabs debugging info
2427 @code{stabs} started out as special symbols within the @code{a.out}
2428 format. Since then, it has been encapsulated into other file
2429 formats, such as COFF and ELF.
2431 While @file{dbxread.c} does some of the basic stab processing,
2432 including for encapsulated versions, @file{stabsread.c} does
2437 @cindex COFF debugging info
2438 The basic COFF definition includes debugging information. The level
2439 of support is minimal and non-extensible, and is not often used.
2441 @subsection Mips debug (Third Eye)
2443 @cindex ECOFF debugging info
2444 ECOFF includes a definition of a special debug format.
2446 The file @file{mdebugread.c} implements reading for this format.
2448 @c mention DWARF 1 as a formerly-supported format
2452 @cindex DWARF 2 debugging info
2453 DWARF 2 is an improved but incompatible version of DWARF 1.
2455 The DWARF 2 reader is in @file{dwarf2read.c}.
2457 @subsection Compressed DWARF 2
2459 @cindex Compressed DWARF 2 debugging info
2460 Compressed DWARF 2 is not technically a separate debugging format, but
2461 merely DWARF 2 debug information that has been compressed. In this
2462 format, every object-file section holding DWARF 2 debugging
2463 information is compressed and prepended with a header. (The section
2464 is also typically renamed, so a section called @code{.debug_info} in a
2465 DWARF 2 binary would be called @code{.zdebug_info} in a compressed
2466 DWARF 2 binary.) The header is 12 bytes long:
2470 4 bytes: the literal string ``ZLIB''
2472 8 bytes: the uncompressed size of the section, in big-endian byte
2476 The same reader is used for both compressed an normal DWARF 2 info.
2477 Section decompression is done in @code{zlib_decompress_section} in
2478 @file{dwarf2read.c}.
2482 @cindex DWARF 3 debugging info
2483 DWARF 3 is an improved version of DWARF 2.
2487 @cindex SOM debugging info
2488 Like COFF, the SOM definition includes debugging information.
2490 @section Adding a New Symbol Reader to @value{GDBN}
2492 @cindex adding debugging info reader
2493 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
2494 there is probably little to be done.
2496 If you need to add a new object file format, you must first add it to
2497 BFD. This is beyond the scope of this document.
2499 You must then arrange for the BFD code to provide access to the
2500 debugging symbols. Generally @value{GDBN} will have to call swapping
2501 routines from BFD and a few other BFD internal routines to locate the
2502 debugging information. As much as possible, @value{GDBN} should not
2503 depend on the BFD internal data structures.
2505 For some targets (e.g., COFF), there is a special transfer vector used
2506 to call swapping routines, since the external data structures on various
2507 platforms have different sizes and layouts. Specialized routines that
2508 will only ever be implemented by one object file format may be called
2509 directly. This interface should be described in a file
2510 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
2512 @section Memory Management for Symbol Files
2514 Most memory associated with a loaded symbol file is stored on
2515 its @code{objfile_obstack}. This includes symbols, types,
2516 namespace data, and other information produced by the symbol readers.
2518 Because this data lives on the objfile's obstack, it is automatically
2519 released when the objfile is unloaded or reloaded. Therefore one
2520 objfile must not reference symbol or type data from another objfile;
2521 they could be unloaded at different times.
2523 User convenience variables, et cetera, have associated types. Normally
2524 these types live in the associated objfile. However, when the objfile
2525 is unloaded, those types are deep copied to global memory, so that
2526 the values of the user variables and history items are not lost.
2529 @node Language Support
2531 @chapter Language Support
2533 @cindex language support
2534 @value{GDBN}'s language support is mainly driven by the symbol reader,
2535 although it is possible for the user to set the source language
2538 @value{GDBN} chooses the source language by looking at the extension
2539 of the file recorded in the debug info; @file{.c} means C, @file{.f}
2540 means Fortran, etc. It may also use a special-purpose language
2541 identifier if the debug format supports it, like with DWARF.
2543 @section Adding a Source Language to @value{GDBN}
2545 @cindex adding source language
2546 To add other languages to @value{GDBN}'s expression parser, follow the
2550 @item Create the expression parser.
2552 @cindex expression parser
2553 This should reside in a file @file{@var{lang}-exp.y}. Routines for
2554 building parsed expressions into a @code{union exp_element} list are in
2557 @cindex language parser
2558 Since we can't depend upon everyone having Bison, and YACC produces
2559 parsers that define a bunch of global names, the following lines
2560 @strong{must} be included at the top of the YACC parser, to prevent the
2561 various parsers from defining the same global names:
2564 #define yyparse @var{lang}_parse
2565 #define yylex @var{lang}_lex
2566 #define yyerror @var{lang}_error
2567 #define yylval @var{lang}_lval
2568 #define yychar @var{lang}_char
2569 #define yydebug @var{lang}_debug
2570 #define yypact @var{lang}_pact
2571 #define yyr1 @var{lang}_r1
2572 #define yyr2 @var{lang}_r2
2573 #define yydef @var{lang}_def
2574 #define yychk @var{lang}_chk
2575 #define yypgo @var{lang}_pgo
2576 #define yyact @var{lang}_act
2577 #define yyexca @var{lang}_exca
2578 #define yyerrflag @var{lang}_errflag
2579 #define yynerrs @var{lang}_nerrs
2582 At the bottom of your parser, define a @code{struct language_defn} and
2583 initialize it with the right values for your language. Define an
2584 @code{initialize_@var{lang}} routine and have it call
2585 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
2586 that your language exists. You'll need some other supporting variables
2587 and functions, which will be used via pointers from your
2588 @code{@var{lang}_language_defn}. See the declaration of @code{struct
2589 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
2590 for more information.
2592 @item Add any evaluation routines, if necessary
2594 @cindex expression evaluation routines
2595 @findex evaluate_subexp
2596 @findex prefixify_subexp
2597 @findex length_of_subexp
2598 If you need new opcodes (that represent the operations of the language),
2599 add them to the enumerated type in @file{expression.h}. Add support
2600 code for these operations in the @code{evaluate_subexp} function
2601 defined in the file @file{eval.c}. Add cases
2602 for new opcodes in two functions from @file{parse.c}:
2603 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
2604 the number of @code{exp_element}s that a given operation takes up.
2606 @item Update some existing code
2608 Add an enumerated identifier for your language to the enumerated type
2609 @code{enum language} in @file{defs.h}.
2611 Update the routines in @file{language.c} so your language is included.
2612 These routines include type predicates and such, which (in some cases)
2613 are language dependent. If your language does not appear in the switch
2614 statement, an error is reported.
2616 @vindex current_language
2617 Also included in @file{language.c} is the code that updates the variable
2618 @code{current_language}, and the routines that translate the
2619 @code{language_@var{lang}} enumerated identifier into a printable
2622 @findex _initialize_language
2623 Update the function @code{_initialize_language} to include your
2624 language. This function picks the default language upon startup, so is
2625 dependent upon which languages that @value{GDBN} is built for.
2627 @findex allocate_symtab
2628 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
2629 code so that the language of each symtab (source file) is set properly.
2630 This is used to determine the language to use at each stack frame level.
2631 Currently, the language is set based upon the extension of the source
2632 file. If the language can be better inferred from the symbol
2633 information, please set the language of the symtab in the symbol-reading
2636 @findex print_subexp
2637 @findex op_print_tab
2638 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
2639 expression opcodes you have added to @file{expression.h}. Also, add the
2640 printed representations of your operators to @code{op_print_tab}.
2642 @item Add a place of call
2645 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2646 @code{parse_exp_1} (defined in @file{parse.c}).
2648 @item Edit @file{Makefile.in}
2650 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2651 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2652 not get linked in, or, worse yet, it may not get @code{tar}red into the
2657 @node Host Definition
2659 @chapter Host Definition
2661 With the advent of Autoconf, it's rarely necessary to have host
2662 definition machinery anymore. The following information is provided,
2663 mainly, as an historical reference.
2665 @section Adding a New Host
2667 @cindex adding a new host
2668 @cindex host, adding
2669 @value{GDBN}'s host configuration support normally happens via Autoconf.
2670 New host-specific definitions should not be needed. Older hosts
2671 @value{GDBN} still use the host-specific definitions and files listed
2672 below, but these mostly exist for historical reasons, and will
2673 eventually disappear.
2676 @item gdb/config/@var{arch}/@var{xyz}.mh
2677 This file is a Makefile fragment that once contained both host and
2678 native configuration information (@pxref{Native Debugging}) for the
2679 machine @var{xyz}. The host configuration information is now handled
2682 Host configuration information included definitions for @code{CC},
2683 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2684 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2686 New host-only configurations do not need this file.
2690 (Files named @file{gdb/config/@var{arch}/xm-@var{xyz}.h} were once
2691 used to define host-specific macros, but were no longer needed and
2692 have all been removed.)
2694 @subheading Generic Host Support Files
2696 @cindex generic host support
2697 There are some ``generic'' versions of routines that can be used by
2701 @cindex remote debugging support
2702 @cindex serial line support
2704 This contains serial line support for Unix systems. It is included by
2705 default on all Unix-like hosts.
2708 This contains serial pipe support for Unix systems. It is included by
2709 default on all Unix-like hosts.
2712 This contains serial line support for 32-bit programs running under
2713 Windows using MinGW.
2716 This contains serial line support for 32-bit programs running under DOS,
2717 using the DJGPP (a.k.a.@: GO32) execution environment.
2719 @cindex TCP remote support
2721 This contains generic TCP support using sockets. It is included by
2722 default on all Unix-like hosts and with MinGW.
2725 @section Host Conditionals
2727 When @value{GDBN} is configured and compiled, various macros are
2728 defined or left undefined, to control compilation based on the
2729 attributes of the host system. While formerly they could be set in
2730 host-specific header files, at present they can be changed only by
2731 setting @code{CFLAGS} when building, or by editing the source code.
2733 These macros and their meanings (or if the meaning is not documented
2734 here, then one of the source files where they are used is indicated)
2738 @item @value{GDBN}INIT_FILENAME
2739 The default name of @value{GDBN}'s initialization file (normally
2742 @item CRLF_SOURCE_FILES
2743 @cindex DOS text files
2744 Define this if host files use @code{\r\n} rather than @code{\n} as a
2745 line terminator. This will cause source file listings to omit @code{\r}
2746 characters when printing and it will allow @code{\r\n} line endings of files
2747 which are ``sourced'' by gdb. It must be possible to open files in binary
2748 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2750 @item DEFAULT_PROMPT
2752 The default value of the prompt string (normally @code{"(gdb) "}).
2755 @cindex terminal device
2756 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2759 Substitute for isatty, if not available.
2762 Define this if binary files are opened the same way as text files.
2764 @item CC_HAS_LONG_LONG
2765 @cindex @code{long long} data type
2766 Define this if the host C compiler supports @code{long long}. This is set
2767 by the @code{configure} script.
2769 @item PRINTF_HAS_LONG_LONG
2770 Define this if the host can handle printing of long long integers via
2771 the printf format conversion specifier @code{ll}. This is set by the
2772 @code{configure} script.
2774 @item LSEEK_NOT_LINEAR
2775 Define this if @code{lseek (n)} does not necessarily move to byte number
2776 @code{n} in the file. This is only used when reading source files. It
2777 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2780 Define this to help placate @code{lint} in some situations.
2783 Define this to override the defaults of @code{__volatile__} or
2788 @node Target Architecture Definition
2790 @chapter Target Architecture Definition
2792 @cindex target architecture definition
2793 @value{GDBN}'s target architecture defines what sort of
2794 machine-language programs @value{GDBN} can work with, and how it works
2797 The target architecture object is implemented as the C structure
2798 @code{struct gdbarch *}. The structure, and its methods, are generated
2799 using the Bourne shell script @file{gdbarch.sh}.
2802 * OS ABI Variant Handling::
2803 * Initialize New Architecture::
2804 * Registers and Memory::
2805 * Pointers and Addresses::
2807 * Register Representation::
2808 * Frame Interpretation::
2809 * Inferior Call Setup::
2810 * Adding support for debugging core files::
2811 * Defining Other Architecture Features::
2812 * Adding a New Target::
2815 @node OS ABI Variant Handling
2816 @section Operating System ABI Variant Handling
2817 @cindex OS ABI variants
2819 @value{GDBN} provides a mechanism for handling variations in OS
2820 ABIs. An OS ABI variant may have influence over any number of
2821 variables in the target architecture definition. There are two major
2822 components in the OS ABI mechanism: sniffers and handlers.
2824 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2825 (the architecture may be wildcarded) in an attempt to determine the
2826 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2827 to be @dfn{generic}, while sniffers for a specific architecture are
2828 considered to be @dfn{specific}. A match from a specific sniffer
2829 overrides a match from a generic sniffer. Multiple sniffers for an
2830 architecture/flavour may exist, in order to differentiate between two
2831 different operating systems which use the same basic file format. The
2832 OS ABI framework provides a generic sniffer for ELF-format files which
2833 examines the @code{EI_OSABI} field of the ELF header, as well as note
2834 sections known to be used by several operating systems.
2836 @cindex fine-tuning @code{gdbarch} structure
2837 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2838 selected OS ABI. There may be only one handler for a given OS ABI
2839 for each BFD architecture.
2841 The following OS ABI variants are defined in @file{defs.h}:
2845 @findex GDB_OSABI_UNINITIALIZED
2846 @item GDB_OSABI_UNINITIALIZED
2847 Used for struct gdbarch_info if ABI is still uninitialized.
2849 @findex GDB_OSABI_UNKNOWN
2850 @item GDB_OSABI_UNKNOWN
2851 The ABI of the inferior is unknown. The default @code{gdbarch}
2852 settings for the architecture will be used.
2854 @findex GDB_OSABI_SVR4
2855 @item GDB_OSABI_SVR4
2856 UNIX System V Release 4.
2858 @findex GDB_OSABI_HURD
2859 @item GDB_OSABI_HURD
2860 GNU using the Hurd kernel.
2862 @findex GDB_OSABI_SOLARIS
2863 @item GDB_OSABI_SOLARIS
2866 @findex GDB_OSABI_OSF1
2867 @item GDB_OSABI_OSF1
2868 OSF/1, including Digital UNIX and Compaq Tru64 UNIX.
2870 @findex GDB_OSABI_LINUX
2871 @item GDB_OSABI_LINUX
2872 GNU using the Linux kernel.
2874 @findex GDB_OSABI_FREEBSD_AOUT
2875 @item GDB_OSABI_FREEBSD_AOUT
2876 FreeBSD using the @code{a.out} executable format.
2878 @findex GDB_OSABI_FREEBSD_ELF
2879 @item GDB_OSABI_FREEBSD_ELF
2880 FreeBSD using the ELF executable format.
2882 @findex GDB_OSABI_NETBSD_AOUT
2883 @item GDB_OSABI_NETBSD_AOUT
2884 NetBSD using the @code{a.out} executable format.
2886 @findex GDB_OSABI_NETBSD_ELF
2887 @item GDB_OSABI_NETBSD_ELF
2888 NetBSD using the ELF executable format.
2890 @findex GDB_OSABI_OPENBSD_ELF
2891 @item GDB_OSABI_OPENBSD_ELF
2892 OpenBSD using the ELF executable format.
2894 @findex GDB_OSABI_WINCE
2895 @item GDB_OSABI_WINCE
2898 @findex GDB_OSABI_GO32
2899 @item GDB_OSABI_GO32
2902 @findex GDB_OSABI_IRIX
2903 @item GDB_OSABI_IRIX
2906 @findex GDB_OSABI_INTERIX
2907 @item GDB_OSABI_INTERIX
2908 Interix (Posix layer for MS-Windows systems).
2910 @findex GDB_OSABI_HPUX_ELF
2911 @item GDB_OSABI_HPUX_ELF
2912 HP/UX using the ELF executable format.
2914 @findex GDB_OSABI_HPUX_SOM
2915 @item GDB_OSABI_HPUX_SOM
2916 HP/UX using the SOM executable format.
2918 @findex GDB_OSABI_QNXNTO
2919 @item GDB_OSABI_QNXNTO
2922 @findex GDB_OSABI_CYGWIN
2923 @item GDB_OSABI_CYGWIN
2926 @findex GDB_OSABI_AIX
2932 Here are the functions that make up the OS ABI framework:
2934 @deftypefun {const char *} gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2935 Return the name of the OS ABI corresponding to @var{osabi}.
2938 @deftypefun void gdbarch_register_osabi (enum bfd_architecture @var{arch}, unsigned long @var{machine}, enum gdb_osabi @var{osabi}, void (*@var{init_osabi})(struct gdbarch_info @var{info}, struct gdbarch *@var{gdbarch}))
2939 Register the OS ABI handler specified by @var{init_osabi} for the
2940 architecture, machine type and OS ABI specified by @var{arch},
2941 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2942 machine type, which implies the architecture's default machine type,
2946 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2947 Register the OS ABI file sniffer specified by @var{sniffer} for the
2948 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2949 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2950 be generic, and is allowed to examine @var{flavour}-flavoured files for
2954 @deftypefun {enum gdb_osabi} gdbarch_lookup_osabi (bfd *@var{abfd})
2955 Examine the file described by @var{abfd} to determine its OS ABI.
2956 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2960 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2961 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2962 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2963 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2964 architecture, a warning will be issued and the debugging session will continue
2965 with the defaults already established for @var{gdbarch}.
2968 @deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj})
2969 Helper routine for ELF file sniffers. Examine the file described by
2970 @var{abfd} and look at ABI tag note sections to determine the OS ABI
2971 from the note. This function should be called via
2972 @code{bfd_map_over_sections}.
2975 @node Initialize New Architecture
2976 @section Initializing a New Architecture
2979 * How an Architecture is Represented::
2980 * Looking Up an Existing Architecture::
2981 * Creating a New Architecture::
2984 @node How an Architecture is Represented
2985 @subsection How an Architecture is Represented
2986 @cindex architecture representation
2987 @cindex representation of architecture
2989 Each @code{gdbarch} is associated with a single @sc{bfd} architecture,
2990 via a @code{bfd_arch_@var{arch}} in the @code{bfd_architecture}
2991 enumeration. The @code{gdbarch} is registered by a call to
2992 @code{register_gdbarch_init}, usually from the file's
2993 @code{_initialize_@var{filename}} routine, which will be automatically
2994 called during @value{GDBN} startup. The arguments are a @sc{bfd}
2995 architecture constant and an initialization function.
2997 @findex _initialize_@var{arch}_tdep
2998 @cindex @file{@var{arch}-tdep.c}
2999 A @value{GDBN} description for a new architecture, @var{arch} is created by
3000 defining a global function @code{_initialize_@var{arch}_tdep}, by
3001 convention in the source file @file{@var{arch}-tdep.c}. For example,
3002 in the case of the OpenRISC 1000, this function is called
3003 @code{_initialize_or1k_tdep} and is found in the file
3006 @cindex @file{configure.tgt}
3007 @cindex @code{gdbarch}
3008 @findex gdbarch_register
3009 The resulting object files containing the implementation of the
3010 @code{_initialize_@var{arch}_tdep} function are specified in the @value{GDBN}
3011 @file{configure.tgt} file, which includes a large case statement
3012 pattern matching against the @code{--target} option of the
3013 @code{configure} script. The new @code{struct gdbarch} is created
3014 within the @code{_initialize_@var{arch}_tdep} function by calling
3015 @code{gdbarch_register}:
3018 void gdbarch_register (enum bfd_architecture @var{architecture},
3019 gdbarch_init_ftype *@var{init_func},
3020 gdbarch_dump_tdep_ftype *@var{tdep_dump_func});
3023 The @var{architecture} will identify the unique @sc{bfd} to be
3024 associated with this @code{gdbarch}. The @var{init_func} funciton is
3025 called to create and return the new @code{struct gdbarch}. The
3026 @var{tdep_dump_func} function will dump the target specific details
3027 associated with this architecture.
3029 For example the function @code{_initialize_or1k_tdep} creates its
3030 architecture for 32-bit OpenRISC 1000 architectures by calling:
3033 gdbarch_register (bfd_arch_or32, or1k_gdbarch_init, or1k_dump_tdep);
3036 @node Looking Up an Existing Architecture
3037 @subsection Looking Up an Existing Architecture
3038 @cindex @code{gdbarch} lookup
3040 The initialization function has this prototype:
3043 static struct gdbarch *
3044 @var{arch}_gdbarch_init (struct gdbarch_info @var{info},
3045 struct gdbarch_list *@var{arches})
3048 The @var{info} argument contains parameters used to select the correct
3049 architecture, and @var{arches} is a list of architectures which
3050 have already been created with the same @code{bfd_arch_@var{arch}}
3053 The initialization function should first make sure that @var{info}
3054 is acceptable, and return @code{NULL} if it is not. Then, it should
3055 search through @var{arches} for an exact match to @var{info}, and
3056 return one if found. Lastly, if no exact match was found, it should
3057 create a new architecture based on @var{info} and return it.
3059 @findex gdbarch_list_lookup_by_info
3060 @cindex @code{gdbarch_info}
3061 The lookup is done using @code{gdbarch_list_lookup_by_info}. It is
3062 passed the list of existing architectures, @var{arches}, and the
3063 @code{struct gdbarch_info}, @var{info}, and returns the first matching
3064 architecture it finds, or @code{NULL} if none are found. If an
3065 architecture is found it can be returned as the result from the
3066 initialization function, otherwise a new @code{struct gdbach} will need
3069 The struct gdbarch_info has the following components:
3074 const struct bfd_arch_info *bfd_arch_info;
3077 struct gdbarch_tdep_info *tdep_info;
3078 enum gdb_osabi osabi;
3079 const struct target_desc *target_desc;
3083 @vindex bfd_arch_info
3084 The @code{bfd_arch_info} member holds the key details about the
3085 architecture. The @code{byte_order} member is a value in an
3086 enumeration indicating the endianism. The @code{abfd} member is a
3087 pointer to the full @sc{bfd}, the @code{tdep_info} member is
3088 additional custom target specific information, @code{osabi} identifies
3089 which (if any) of a number of operating specific ABIs are used by this
3090 architecture and the @code{target_desc} member is a set of name-value
3091 pairs with information about register usage in this target.
3093 When the @code{struct gdbarch} initialization function is called, not
3094 all the fields are provided---only those which can be deduced from the
3095 @sc{bfd}. The @code{struct gdbarch_info}, @var{info} is used as a
3096 look-up key with the list of existing architectures, @var{arches} to
3097 see if a suitable architecture already exists. The @var{tdep_info},
3098 @var{osabi} and @var{target_desc} fields may be added before this
3099 lookup to refine the search.
3101 Only information in @var{info} should be used to choose the new
3102 architecture. Historically, @var{info} could be sparse, and
3103 defaults would be collected from the first element on @var{arches}.
3104 However, @value{GDBN} now fills in @var{info} more thoroughly,
3105 so new @code{gdbarch} initialization functions should not take
3106 defaults from @var{arches}.
3108 @node Creating a New Architecture
3109 @subsection Creating a New Architecture
3110 @cindex @code{struct gdbarch} creation
3112 @findex gdbarch_alloc
3113 @cindex @code{gdbarch_tdep} when allocating new @code{gdbarch}
3114 If no architecture is found, then a new architecture must be created,
3115 by calling @code{gdbarch_alloc} using the supplied @code{@w{struct
3116 gdbarch_info}} and any additional custom target specific
3117 information in a @code{struct gdbarch_tdep}. The prototype for
3118 @code{gdbarch_alloc} is:
3121 struct gdbarch *gdbarch_alloc (const struct gdbarch_info *@var{info},
3122 struct gdbarch_tdep *@var{tdep});
3125 @cindex @code{set_gdbarch} functions
3126 @cindex @code{gdbarch} accessor functions
3127 The newly created struct gdbarch must then be populated. Although
3128 there are default values, in most cases they are not what is
3131 For each element, @var{X}, there is are a pair of corresponding accessor
3132 functions, one to set the value of that element,
3133 @code{set_gdbarch_@var{X}}, the second to either get the value of an
3134 element (if it is a variable) or to apply the element (if it is a
3135 function), @code{gdbarch_@var{X}}. Note that both accessor functions
3136 take a pointer to the @code{@w{struct gdbarch}} as first
3137 argument. Populating the new @code{gdbarch} should use the
3138 @code{set_gdbarch} functions.
3140 The following sections identify the main elements that should be set
3141 in this way. This is not the complete list, but represents the
3142 functions and elements that must commonly be specified for a new
3143 architecture. Many of the functions and variables are described in the
3144 header file @file{gdbarch.h}.
3146 This is the main work in defining a new architecture. Implementing the
3147 set of functions to populate the @code{struct gdbarch}.
3149 @cindex @code{gdbarch_tdep} definition
3150 @code{struct gdbarch_tdep} is not defined within @value{GDBN}---it is up
3151 to the user to define this struct if it is needed to hold custom target
3152 information that is not covered by the standard @code{@w{struct
3153 gdbarch}}. For example with the OpenRISC 1000 architecture it is used to
3154 hold the number of matchpoints available in the target (along with other
3157 If there is no additional target specific information, it can be set to
3160 @node Registers and Memory
3161 @section Registers and Memory
3163 @value{GDBN}'s model of the target machine is rather simple.
3164 @value{GDBN} assumes the machine includes a bank of registers and a
3165 block of memory. Each register may have a different size.
3167 @value{GDBN} does not have a magical way to match up with the
3168 compiler's idea of which registers are which; however, it is critical
3169 that they do match up accurately. The only way to make this work is
3170 to get accurate information about the order that the compiler uses,
3171 and to reflect that in the @code{gdbarch_register_name} and related functions.
3173 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
3175 @node Pointers and Addresses
3176 @section Pointers Are Not Always Addresses
3177 @cindex pointer representation
3178 @cindex address representation
3179 @cindex word-addressed machines
3180 @cindex separate data and code address spaces
3181 @cindex spaces, separate data and code address
3182 @cindex address spaces, separate data and code
3183 @cindex code pointers, word-addressed
3184 @cindex converting between pointers and addresses
3185 @cindex D10V addresses
3187 On almost all 32-bit architectures, the representation of a pointer is
3188 indistinguishable from the representation of some fixed-length number
3189 whose value is the byte address of the object pointed to. On such
3190 machines, the words ``pointer'' and ``address'' can be used interchangeably.
3191 However, architectures with smaller word sizes are often cramped for
3192 address space, so they may choose a pointer representation that breaks this
3193 identity, and allows a larger code address space.
3195 @c D10V is gone from sources - more current example?
3197 For example, the Renesas D10V is a 16-bit VLIW processor whose
3198 instructions are 32 bits long@footnote{Some D10V instructions are
3199 actually pairs of 16-bit sub-instructions. However, since you can't
3200 jump into the middle of such a pair, code addresses can only refer to
3201 full 32 bit instructions, which is what matters in this explanation.}.
3202 If the D10V used ordinary byte addresses to refer to code locations,
3203 then the processor would only be able to address 64kb of instructions.
3204 However, since instructions must be aligned on four-byte boundaries, the
3205 low two bits of any valid instruction's byte address are always
3206 zero---byte addresses waste two bits. So instead of byte addresses,
3207 the D10V uses word addresses---byte addresses shifted right two bits---to
3208 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
3211 However, this means that code pointers and data pointers have different
3212 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
3213 @code{0xC020} when used as a data address, but refers to byte address
3214 @code{0x30080} when used as a code address.
3216 (The D10V also uses separate code and data address spaces, which also
3217 affects the correspondence between pointers and addresses, but we're
3218 going to ignore that here; this example is already too long.)
3220 To cope with architectures like this---the D10V is not the only
3221 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
3222 byte numbers, and @dfn{pointers}, which are the target's representation
3223 of an address of a particular type of data. In the example above,
3224 @code{0xC020} is the pointer, which refers to one of the addresses
3225 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
3226 @value{GDBN} provides functions for turning a pointer into an address
3227 and vice versa, in the appropriate way for the current architecture.
3229 Unfortunately, since addresses and pointers are identical on almost all
3230 processors, this distinction tends to bit-rot pretty quickly. Thus,
3231 each time you port @value{GDBN} to an architecture which does
3232 distinguish between pointers and addresses, you'll probably need to
3233 clean up some architecture-independent code.
3235 Here are functions which convert between pointers and addresses:
3237 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
3238 Treat the bytes at @var{buf} as a pointer or reference of type
3239 @var{type}, and return the address it represents, in a manner
3240 appropriate for the current architecture. This yields an address
3241 @value{GDBN} can use to read target memory, disassemble, etc. Note that
3242 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
3245 For example, if the current architecture is the Intel x86, this function
3246 extracts a little-endian integer of the appropriate length from
3247 @var{buf} and returns it. However, if the current architecture is the
3248 D10V, this function will return a 16-bit integer extracted from
3249 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
3251 If @var{type} is not a pointer or reference type, then this function
3252 will signal an internal error.
3255 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
3256 Store the address @var{addr} in @var{buf}, in the proper format for a
3257 pointer of type @var{type} in the current architecture. Note that
3258 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
3261 For example, if the current architecture is the Intel x86, this function
3262 stores @var{addr} unmodified as a little-endian integer of the
3263 appropriate length in @var{buf}. However, if the current architecture
3264 is the D10V, this function divides @var{addr} by four if @var{type} is
3265 a pointer to a function, and then stores it in @var{buf}.
3267 If @var{type} is not a pointer or reference type, then this function
3268 will signal an internal error.
3271 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
3272 Assuming that @var{val} is a pointer, return the address it represents,
3273 as appropriate for the current architecture.
3275 This function actually works on integral values, as well as pointers.
3276 For pointers, it performs architecture-specific conversions as
3277 described above for @code{extract_typed_address}.
3280 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
3281 Create and return a value representing a pointer of type @var{type} to
3282 the address @var{addr}, as appropriate for the current architecture.
3283 This function performs architecture-specific conversions as described
3284 above for @code{store_typed_address}.
3287 Here are two functions which architectures can define to indicate the
3288 relationship between pointers and addresses. These have default
3289 definitions, appropriate for architectures on which all pointers are
3290 simple unsigned byte addresses.
3292 @deftypefun CORE_ADDR gdbarch_pointer_to_address (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf})
3293 Assume that @var{buf} holds a pointer of type @var{type}, in the
3294 appropriate format for the current architecture. Return the byte
3295 address the pointer refers to.
3297 This function may safely assume that @var{type} is either a pointer or a
3298 C@t{++} reference type.
3301 @deftypefun void gdbarch_address_to_pointer (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
3302 Store in @var{buf} a pointer of type @var{type} representing the address
3303 @var{addr}, in the appropriate format for the current architecture.
3305 This function may safely assume that @var{type} is either a pointer or a
3306 C@t{++} reference type.
3309 @node Address Classes
3310 @section Address Classes
3311 @cindex address classes
3312 @cindex DW_AT_byte_size
3313 @cindex DW_AT_address_class
3315 Sometimes information about different kinds of addresses is available
3316 via the debug information. For example, some programming environments
3317 define addresses of several different sizes. If the debug information
3318 distinguishes these kinds of address classes through either the size
3319 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
3320 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
3321 following macros should be defined in order to disambiguate these
3322 types within @value{GDBN} as well as provide the added information to
3323 a @value{GDBN} user when printing type expressions.
3325 @deftypefun int gdbarch_address_class_type_flags (struct gdbarch *@var{gdbarch}, int @var{byte_size}, int @var{dwarf2_addr_class})
3326 Returns the type flags needed to construct a pointer type whose size
3327 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
3328 This function is normally called from within a symbol reader. See
3329 @file{dwarf2read.c}.
3332 @deftypefun {char *} gdbarch_address_class_type_flags_to_name (struct gdbarch *@var{gdbarch}, int @var{type_flags})
3333 Given the type flags representing an address class qualifier, return
3336 @deftypefun int gdbarch_address_class_name_to_type_flags (struct gdbarch *@var{gdbarch}, int @var{name}, int *@var{type_flags_ptr})
3337 Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags
3338 for that address class qualifier.
3341 Since the need for address classes is rather rare, none of
3342 the address class functions are defined by default. Predicate
3343 functions are provided to detect when they are defined.
3345 Consider a hypothetical architecture in which addresses are normally
3346 32-bits wide, but 16-bit addresses are also supported. Furthermore,
3347 suppose that the @w{DWARF 2} information for this architecture simply
3348 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
3349 of these "short" pointers. The following functions could be defined
3350 to implement the address class functions:
3353 somearch_address_class_type_flags (int byte_size,
3354 int dwarf2_addr_class)
3357 return TYPE_FLAG_ADDRESS_CLASS_1;
3363 somearch_address_class_type_flags_to_name (int type_flags)
3365 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
3372 somearch_address_class_name_to_type_flags (char *name,
3373 int *type_flags_ptr)
3375 if (strcmp (name, "short") == 0)
3377 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
3385 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
3386 to indicate the presence of one of these ``short'' pointers. For
3387 example if the debug information indicates that @code{short_ptr_var} is
3388 one of these short pointers, @value{GDBN} might show the following
3392 (gdb) ptype short_ptr_var
3393 type = int * @@short
3397 @node Register Representation
3398 @section Register Representation
3401 * Raw and Cooked Registers::
3402 * Register Architecture Functions & Variables::
3403 * Register Information Functions::
3404 * Register and Memory Data::
3405 * Register Caching::
3408 @node Raw and Cooked Registers
3409 @subsection Raw and Cooked Registers
3410 @cindex raw register representation
3411 @cindex cooked register representation
3412 @cindex representations, raw and cooked registers
3414 @value{GDBN} considers registers to be a set with members numbered
3415 linearly from 0 upwards. The first part of that set corresponds to real
3416 physical registers, the second part to any @dfn{pseudo-registers}.
3417 Pseudo-registers have no independent physical existence, but are useful
3418 representations of information within the architecture. For example the
3419 OpenRISC 1000 architecture has up to 32 general purpose registers, which
3420 are typically represented as 32-bit (or 64-bit) integers. However the
3421 GPRs are also used as operands to the floating point operations, and it
3422 could be convenient to define a set of pseudo-registers, to show the
3423 GPRs represented as floating point values.
3425 For any architecture, the implementer will decide on a mapping from
3426 hardware to @value{GDBN} register numbers. The registers corresponding to real
3427 hardware are referred to as @dfn{raw} registers, the remaining registers are
3428 @dfn{pseudo-registers}. The total register set (raw and pseudo) is called
3429 the @dfn{cooked} register set.
3432 @node Register Architecture Functions & Variables
3433 @subsection Functions and Variables Specifying the Register Architecture
3434 @cindex @code{gdbarch} register architecture functions
3436 These @code{struct gdbarch} functions and variables specify the number
3437 and type of registers in the architecture.
3439 @deftypefn {Architecture Function} CORE_ADDR read_pc (struct regcache *@var{regcache})
3441 @deftypefn {Architecture Function} void write_pc (struct regcache *@var{regcache}, CORE_ADDR @var{val})
3443 Read or write the program counter. The default value of both
3444 functions is @code{NULL} (no function available). If the program
3445 counter is just an ordinary register, it can be specified in
3446 @code{struct gdbarch} instead (see @code{pc_regnum} below) and it will
3447 be read or written using the standard routines to access registers. This
3448 function need only be specified if the program counter is not an
3451 Any register information can be obtained using the supplied register
3452 cache, @var{regcache}. @xref{Register Caching, , Register Caching}.
3456 @deftypefn {Architecture Function} void pseudo_register_read (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf})
3458 @deftypefn {Architecture Function} void pseudo_register_write (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf})
3460 These functions should be defined if there are any pseudo-registers.
3461 The default value is @code{NULL}. @var{regnum} is the number of the
3462 register to read or write (which will be a @dfn{cooked} register
3463 number) and @var{buf} is the buffer where the value read will be
3464 placed, or from which the value to be written will be taken. The
3465 value in the buffer may be converted to or from a signed or unsigned
3466 integral value using one of the utility functions (@pxref{Register and
3467 Memory Data, , Using Different Register and Memory Data
3470 The access should be for the specified architecture,
3471 @var{gdbarch}. Any register information can be obtained using the
3472 supplied register cache, @var{regcache}. @xref{Register Caching, ,
3477 @deftypevr {Architecture Variable} int sp_regnum
3479 @cindex stack pointer
3482 This specifies the register holding the stack pointer, which may be a
3483 raw or pseudo-register. It defaults to -1 (not defined), but it is an
3484 error for it not to be defined.
3486 The value of the stack pointer register can be accessed withing
3487 @value{GDBN} as the variable @kbd{$sp}.
3491 @deftypevr {Architecture Variable} int pc_regnum
3493 @cindex program counter
3496 This specifies the register holding the program counter, which may be a
3497 raw or pseudo-register. It defaults to -1 (not defined). If
3498 @code{pc_regnum} is not defined, then the functions @code{read_pc} and
3499 @code{write_pc} (see above) must be defined.
3501 The value of the program counter (whether defined as a register, or
3502 through @code{read_pc} and @code{write_pc}) can be accessed withing
3503 @value{GDBN} as the variable @kbd{$pc}.
3507 @deftypevr {Architecture Variable} int ps_regnum
3509 @cindex processor status register
3510 @cindex status register
3513 This specifies the register holding the processor status (often called
3514 the status register), which may be a raw or pseudo-register. It
3515 defaults to -1 (not defined).
3517 If defined, the value of this register can be accessed withing
3518 @value{GDBN} as the variable @kbd{$ps}.
3522 @deftypevr {Architecture Variable} int fp0_regnum
3524 @cindex first floating point register
3526 This specifies the first floating point register. It defaults to
3527 0. @code{fp0_regnum} is not needed unless the target offers support
3532 @node Register Information Functions
3533 @subsection Functions Giving Register Information
3534 @cindex @code{gdbarch} register information functions
3536 These functions return information about registers.
3538 @deftypefn {Architecture Function} {const char *} register_name (struct gdbarch *@var{gdbarch}, int @var{regnum})
3540 This function should convert a register number (raw or pseudo) to a
3541 register name (as a C @code{const char *}). This is used both to
3542 determine the name of a register for output and to work out the meaning
3543 of any register names used as input. The function may also return
3544 @code{NULL}, to indicate that @var{regnum} is not a valid register.
3546 For example with the OpenRISC 1000, @value{GDBN} registers 0-31 are the
3547 General Purpose Registers, register 32 is the program counter and
3548 register 33 is the supervision register (i.e.@: the processor status
3549 register), which map to the strings @code{"gpr00"} through
3550 @code{"gpr31"}, @code{"pc"} and @code{"sr"} respectively. This means
3551 that the @value{GDBN} command @kbd{print $gpr5} should print the value of
3552 the OR1K general purpose register 5@footnote{
3553 @cindex frame pointer
3555 Historically, @value{GDBN} always had a concept of a frame pointer
3556 register, which could be accessed via the @value{GDBN} variable,
3557 @kbd{$fp}. That concept is now deprecated, recognizing that not all
3558 architectures have a frame pointer. However if an architecture does
3559 have a frame pointer register, and defines a register or
3560 pseudo-register with the name @code{"fp"}, then that register will be
3561 used as the value of the @kbd{$fp} variable.}.
3563 The default value for this function is @code{NULL}, meaning
3564 undefined. It should always be defined.
3566 The access should be for the specified architecture, @var{gdbarch}.
3570 @deftypefn {Architecture Function} {struct type *} register_type (struct gdbarch *@var{gdbarch}, int @var{regnum})
3572 Given a register number, this function identifies the type of data it
3573 may be holding, specified as a @code{struct type}. @value{GDBN} allows
3574 creation of arbitrary types, but a number of built in types are
3575 provided (@code{builtin_type_void}, @code{builtin_type_int32} etc),
3576 together with functions to derive types from these.
3578 Typically the program counter will have a type of ``pointer to
3579 function'' (it points to code), the frame pointer and stack pointer
3580 will have types of ``pointer to void'' (they point to data on the stack)
3581 and all other integer registers will have a type of 32-bit integer or
3584 This information guides the formatting when displaying register
3585 information. The default value is @code{NULL} meaning no information is
3586 available to guide formatting when displaying registers.
3590 @deftypefn {Architecture Function} void print_registers_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, int @var{regnum}, int @var{all})
3592 Define this function to print out one or all of the registers for the
3593 @value{GDBN} @kbd{info registers} command. The default value is the
3594 function @code{default_print_registers_info}, which uses the register
3595 type information (see @code{register_type} above) to determine how each
3596 register should be printed. Define a custom version of this function
3597 for fuller control over how the registers are displayed.
3599 The access should be for the specified architecture, @var{gdbarch},
3600 with output to the file specified by the User Interface
3601 Independent Output file handle, @var{file} (@pxref{UI-Independent
3602 Output, , UI-Independent Output---the @code{ui_out}
3605 The registers should show their values in the frame specified by
3606 @var{frame}. If @var{regnum} is -1 and @var{all} is zero, then all
3607 the ``significant'' registers should be shown (the implementer should
3608 decide which registers are ``significant''). Otherwise only the value of
3609 the register specified by @var{regnum} should be output. If
3610 @var{regnum} is -1 and @var{all} is non-zero (true), then the value of
3611 all registers should be shown.
3613 By default @code{default_print_registers_info} prints one register per
3614 line, and if @var{all} is zero omits floating-point registers.
3618 @deftypefn {Architecture Function} void print_float_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, const char *@var{args})
3620 Define this function to provide output about the floating point unit and
3621 registers for the @value{GDBN} @kbd{info float} command respectively.
3622 The default value is @code{NULL} (not defined), meaning no information
3625 The @var{gdbarch} and @var{file} and @var{frame} arguments have the same
3626 meaning as in the @code{print_registers_info} function above. The string
3627 @var{args} contains any supplementary arguments to the @kbd{info float}
3630 Define this function if the target supports floating point operations.
3634 @deftypefn {Architecture Function} void print_vector_info (struct gdbarch *@var{gdbarch}, struct ui_file *@var{file}, struct frame_info *@var{frame}, const char *@var{args})
3636 Define this function to provide output about the vector unit and
3637 registers for the @value{GDBN} @kbd{info vector} command respectively.
3638 The default value is @code{NULL} (not defined), meaning no information
3641 The @var{gdbarch}, @var{file} and @var{frame} arguments have the
3642 same meaning as in the @code{print_registers_info} function above. The
3643 string @var{args} contains any supplementary arguments to the @kbd{info
3646 Define this function if the target supports vector operations.
3650 @deftypefn {Architecture Function} int register_reggroup_p (struct gdbarch *@var{gdbarch}, int @var{regnum}, struct reggroup *@var{group})
3652 @value{GDBN} groups registers into different categories (general,
3653 vector, floating point etc). This function, given a register,
3654 @var{regnum}, and group, @var{group}, returns 1 (true) if the register
3655 is in the group and 0 (false) otherwise.
3657 The information should be for the specified architecture,
3660 The default value is the function @code{default_register_reggroup_p}
3661 which will do a reasonable job based on the type of the register (see
3662 the function @code{register_type} above), with groups for general
3663 purpose registers, floating point registers, vector registers and raw
3664 (i.e not pseudo) registers.
3668 @node Register and Memory Data
3669 @subsection Using Different Register and Memory Data Representations
3670 @cindex register representation
3671 @cindex memory representation
3672 @cindex representations, register and memory
3673 @cindex register data formats, converting
3674 @cindex @code{struct value}, converting register contents to
3676 Some architectures have different representations of data objects,
3677 depending whether the object is held in a register or memory. For
3683 The Alpha architecture can represent 32 bit integer values in
3684 floating-point registers.
3687 The x86 architecture supports 80-bit floating-point registers. The
3688 @code{long double} data type occupies 96 bits in memory but only 80
3689 bits when stored in a register.
3693 In general, the register representation of a data type is determined by
3694 the architecture, or @value{GDBN}'s interface to the architecture, while
3695 the memory representation is determined by the Application Binary
3698 For almost all data types on almost all architectures, the two
3699 representations are identical, and no special handling is needed.
3700 However, they do occasionally differ. An architecture may define the
3701 following @code{struct gdbarch} functions to request conversions
3702 between the register and memory representations of a data type:
3704 @deftypefn {Architecture Function} int gdbarch_convert_register_p (struct gdbarch *@var{gdbarch}, int @var{reg})
3706 Return non-zero (true) if the representation of a data value stored in
3707 this register may be different to the representation of that same data
3708 value when stored in memory. The default value is @code{NULL}
3711 If this function is defined and returns non-zero, the @code{struct
3712 gdbarch} functions @code{gdbarch_register_to_value} and
3713 @code{gdbarch_value_to_register} (see below) should be used to perform
3714 any necessary conversion.
3716 If defined, this function should return zero for the register's native
3717 type, when no conversion is necessary.
3720 @deftypefn {Architecture Function} void gdbarch_register_to_value (struct gdbarch *@var{gdbarch}, int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3722 Convert the value of register number @var{reg} to a data object of
3723 type @var{type}. The buffer at @var{from} holds the register's value
3724 in raw format; the converted value should be placed in the buffer at
3728 @emph{Note:} @code{gdbarch_register_to_value} and
3729 @code{gdbarch_value_to_register} take their @var{reg} and @var{type}
3730 arguments in different orders.
3733 @code{gdbarch_register_to_value} should only be used with registers
3734 for which the @code{gdbarch_convert_register_p} function returns a
3739 @deftypefn {Architecture Function} void gdbarch_value_to_register (struct gdbarch *@var{gdbarch}, struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3741 Convert a data value of type @var{type} to register number @var{reg}'
3745 @emph{Note:} @code{gdbarch_register_to_value} and
3746 @code{gdbarch_value_to_register} take their @var{reg} and @var{type}
3747 arguments in different orders.
3750 @code{gdbarch_value_to_register} should only be used with registers
3751 for which the @code{gdbarch_convert_register_p} function returns a
3756 @node Register Caching
3757 @subsection Register Caching
3758 @cindex register caching
3760 Caching of registers is used, so that the target does not need to be
3761 accessed and reanalyzed multiple times for each register in
3762 circumstances where the register value cannot have changed.
3764 @cindex @code{struct regcache}
3765 @value{GDBN} provides @code{struct regcache}, associated with a
3766 particular @code{struct gdbarch} to hold the cached values of the raw
3767 registers. A set of functions is provided to access both the raw
3768 registers (with @code{raw} in their name) and the full set of cooked
3769 registers (with @code{cooked} in their name). Functions are provided
3770 to ensure the register cache is kept synchronized with the values of
3771 the actual registers in the target.
3773 Accessing registers through the @code{struct regcache} routines will
3774 ensure that the appropriate @code{struct gdbarch} functions are called
3775 when necessary to access the underlying target architecture. In general
3776 users should use the @dfn{cooked} functions, since these will map to the
3777 @dfn{raw} functions automatically as appropriate.
3779 @findex regcache_cooked_read
3780 @findex regcache_cooked_write
3781 @cindex @code{gdb_byte}
3782 @findex regcache_cooked_read_signed
3783 @findex regcache_cooked_read_unsigned
3784 @findex regcache_cooked_write_signed
3785 @findex regcache_cooked_write_unsigned
3786 The two key functions are @code{regcache_cooked_read} and
3787 @code{regcache_cooked_write} which read or write a register from or to
3788 a byte buffer (type @code{gdb_byte *}). For convenience the wrapper
3789 functions @code{regcache_cooked_read_signed},
3790 @code{regcache_cooked_read_unsigned},
3791 @code{regcache_cooked_write_signed} and
3792 @code{regcache_cooked_write_unsigned} are provided, which read or
3793 write the value using the buffer and convert to or from an integral
3794 value as appropriate.
3796 @node Frame Interpretation
3797 @section Frame Interpretation
3800 * All About Stack Frames::
3801 * Frame Handling Terminology::
3803 * Functions and Variable to Analyze Frames::
3804 * Functions to Access Frame Data::
3805 * Analyzing Stacks---Frame Sniffers::
3808 @node All About Stack Frames
3809 @subsection All About Stack Frames
3811 @value{GDBN} needs to understand the stack on which local (automatic)
3812 variables are stored. The area of the stack containing all the local
3813 variables for a function invocation is known as the @dfn{stack frame}
3814 for that function (or colloquially just as the @dfn{frame}). In turn the
3815 function that called the function will have its stack frame, and so on
3816 back through the chain of functions that have been called.
3818 Almost all architectures have one register dedicated to point to the
3819 end of the stack (the @dfn{stack pointer}). Many have a second register
3820 which points to the start of the currently active stack frame (the
3821 @dfn{frame pointer}). The specific arrangements for an architecture are
3822 a key part of the ABI.
3824 A diagram helps to explain this. Here is a simple program to compute
3837 return n * fact (n - 1);
3845 for (i = 0; i < 10; i++)
3848 printf ("%d! = %d\n", i, f);
3853 Consider the state of the stack when the code reaches line 6 after the
3854 main program has called @code{fact@w{ }(3)}. The chain of function
3855 calls will be @code{main ()}, @code{fact@w{ }(3)}, @code{fact@w{
3856 }(2)}, @code{@w{fact (1)}} and @code{fact@w{ }(0)}.
3858 In this illustration the stack is falling (as used for example by the
3859 OpenRISC 1000 ABI). The stack pointer (SP) is at the end of the stack
3860 (lowest address) and the frame pointer (FP) is at the highest address
3861 in the current stack frame. The following diagram shows how the stack
3864 @center @image{stack_frame,14cm}
3866 In each stack frame, offset 0 from the stack pointer is the frame
3867 pointer of the previous frame and offset 4 (this is illustrating a
3868 32-bit architecture) from the stack pointer is the return address.
3869 Local variables are indexed from the frame pointer, with negative
3870 indexes. In the function @code{fact}, offset -4 from the frame
3871 pointer is the argument @var{n}. In the @code{main} function, offset
3872 -4 from the frame pointer is the local variable @var{i} and offset -8
3873 from the frame pointer is the local variable @var{f}@footnote{This is
3874 a simplified example for illustrative purposes only. Good optimizing
3875 compilers would not put anything on the stack for such simple
3876 functions. Indeed they might eliminate the recursion and use of the
3879 It is very easy to get confused when examining stacks. @value{GDBN}
3880 has terminology it uses rigorously throughout. The stack frame of the
3881 function currently executing, or where execution stopped is numbered
3882 zero. In this example frame #0 is the stack frame of the call to
3883 @code{fact@w{ }(0)}. The stack frame of its calling function
3884 (@code{fact@w{ }(1)} in this case) is numbered #1 and so on back
3885 through the chain of calls.
3887 The main @value{GDBN} data structure describing frames is
3888 @code{@w{struct frame_info}}. It is not used directly, but only via
3889 its accessor functions. @code{frame_info} includes information about
3890 the registers in the frame and a pointer to the code of the function
3891 with which the frame is associated. The entire stack is represented as
3892 a linked list of @code{frame_info} structs.
3894 @node Frame Handling Terminology
3895 @subsection Frame Handling Terminology
3897 It is easy to get confused when referencing stack frames. @value{GDBN}
3898 uses some precise terminology.
3904 @cindex stack frame, definition of THIS frame
3905 @cindex frame, definition of THIS frame
3906 @dfn{THIS} frame is the frame currently under consideration.
3910 @cindex stack frame, definition of NEXT frame
3911 @cindex frame, definition of NEXT frame
3912 The @dfn{NEXT} frame, also sometimes called the inner or newer frame is the
3913 frame of the function called by the function of THIS frame.
3916 @cindex PREVIOUS frame
3917 @cindex stack frame, definition of PREVIOUS frame
3918 @cindex frame, definition of PREVIOUS frame
3919 The @dfn{PREVIOUS} frame, also sometimes called the outer or older frame is
3920 the frame of the function which called the function of THIS frame.
3924 So in the example in the previous section (@pxref{All About Stack
3925 Frames, , All About Stack Frames}), if THIS frame is #3 (the call to
3926 @code{fact@w{ }(3)}), the NEXT frame is frame #2 (the call to
3927 @code{fact@w{ }(2)}) and the PREVIOUS frame is frame #4 (the call to
3928 @code{main@w{ }()}).
3930 @cindex innermost frame
3931 @cindex stack frame, definition of innermost frame
3932 @cindex frame, definition of innermost frame
3933 The @dfn{innermost} frame is the frame of the current executing
3934 function, or where the program stopped, in this example, in the middle
3935 of the call to @code{@w{fact (0))}}. It is always numbered frame #0.
3937 @cindex base of a frame
3938 @cindex stack frame, definition of base of a frame
3939 @cindex frame, definition of base of a frame
3940 The @dfn{base} of a frame is the address immediately before the start
3941 of the NEXT frame. For a stack which grows down in memory (a
3942 @dfn{falling} stack) this will be the lowest address and for a stack
3943 which grows up in memory (a @dfn{rising} stack) this will be the
3944 highest address in the frame.
3946 @value{GDBN} functions to analyze the stack are typically given a
3947 pointer to the NEXT frame to determine information about THIS
3948 frame. Information about THIS frame includes data on where the
3949 registers of the PREVIOUS frame are stored in this stack frame. In
3950 this example the frame pointer of the PREVIOUS frame is stored at
3951 offset 0 from the stack pointer of THIS frame.
3954 @cindex stack frame, definition of unwinding
3955 @cindex frame, definition of unwinding
3956 The process whereby a function is given a pointer to the NEXT
3957 frame to work out information about THIS frame is referred to as
3958 @dfn{unwinding}. The @value{GDBN} functions involved in this typically
3959 include unwind in their name.
3962 @cindex stack frame, definition of sniffing
3963 @cindex frame, definition of sniffing
3964 The process of analyzing a target to determine the information that
3965 should go in struct frame_info is called @dfn{sniffing}. The functions
3966 that carry this out are called sniffers and typically include sniffer
3967 in their name. More than one sniffer may be required to extract all
3968 the information for a particular frame.
3970 @cindex sentinel frame
3971 @cindex stack frame, definition of sentinel frame
3972 @cindex frame, definition of sentinel frame
3973 Because so many functions work using the NEXT frame, there is an issue
3974 about addressing the innermost frame---it has no NEXT frame. To solve
3975 this @value{GDBN} creates a dummy frame #-1, known as the
3976 @dfn{sentinel} frame.
3978 @node Prologue Caches
3979 @subsection Prologue Caches
3981 @cindex function prologue
3982 @cindex prologue of a function
3983 All the frame sniffing functions typically examine the code at the
3984 start of the corresponding function, to determine the state of
3985 registers. The ABI will save old values and set new values of key
3986 registers at the start of each function in what is known as the
3987 function @dfn{prologue}.
3989 @cindex prologue cache
3990 For any particular stack frame this data does not change, so all the
3991 standard unwinding functions, in addition to receiving a pointer to
3992 the NEXT frame as their first argument, receive a pointer to a
3993 @dfn{prologue cache} as their second argument. This can be used to store
3994 values associated with a particular frame, for reuse on subsequent
3995 calls involving the same frame.
3997 It is up to the user to define the structure used (it is a
3998 @code{void@w{ }*} pointer) and arrange allocation and deallocation of
3999 storage. However for general use, @value{GDBN} provides
4000 @code{@w{struct trad_frame_cache}}, with a set of accessor
4001 routines. This structure holds the stack and code address of
4002 THIS frame, the base address of the frame, a pointer to the
4003 struct @code{frame_info} for the NEXT frame and details of
4004 where the registers of the PREVIOUS frame may be found in THIS
4007 Typically the first time any sniffer function is called with NEXT
4008 frame, the prologue sniffer for THIS frame will be @code{NULL}. The
4009 sniffer will analyze the frame, allocate a prologue cache structure
4010 and populate it. Subsequent calls using the same NEXT frame will
4011 pass in this prologue cache, so the data can be returned with no
4012 additional analysis.
4014 @node Functions and Variable to Analyze Frames
4015 @subsection Functions and Variable to Analyze Frames
4017 These struct @code{gdbarch} functions and variable should be defined
4018 to provide analysis of the stack frame and allow it to be adjusted as
4021 @deftypefn {Architecture Function} CORE_ADDR skip_prologue (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{pc})
4023 The prologue of a function is the code at the beginning of the
4024 function which sets up the stack frame, saves the return address
4025 etc. The code representing the behavior of the function starts after
4028 This function skips past the prologue of a function if the program
4029 counter, @var{pc}, is within the prologue of a function. The result is
4030 the program counter immediately after the prologue. With modern
4031 optimizing compilers, this may be a far from trivial exercise. However
4032 the required information may be within the binary as DWARF2 debugging
4033 information, making the job much easier.
4035 The default value is @code{NULL} (not defined). This function should always
4036 be provided, but can take advantage of DWARF2 debugging information,
4037 if that is available.
4041 @deftypefn {Architecture Function} int inner_than (CORE_ADDR @var{lhs}, CORE_ADDR @var{rhs})
4042 @findex core_addr_lessthan
4043 @findex core_addr_greaterthan
4045 Given two frame or stack pointers, return non-zero (true) if the first
4046 represents the @dfn{inner} stack frame and 0 (false) otherwise. This
4047 is used to determine whether the target has a stack which grows up in
4048 memory (rising stack) or grows down in memory (falling stack).
4049 @xref{All About Stack Frames, , All About Stack Frames}, for an
4050 explanation of @dfn{inner} frames.
4052 The default value of this function is @code{NULL} and it should always
4053 be defined. However for almost all architectures one of the built-in
4054 functions can be used: @code{core_addr_lessthan} (for stacks growing
4055 down in memory) or @code{core_addr_greaterthan} (for stacks growing up
4060 @anchor{frame_align}
4061 @deftypefn {Architecture Function} CORE_ADDR frame_align (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{address})
4065 The architecture may have constraints on how its frames are
4066 aligned. For example the OpenRISC 1000 ABI requires stack frames to be
4067 double-word aligned, but 32-bit versions of the architecture allocate
4068 single-word values to the stack. Thus extra padding may be needed at
4069 the end of a stack frame.
4071 Given a proposed address for the stack pointer, this function
4072 returns a suitably aligned address (by expanding the stack frame).
4074 The default value is @code{NULL} (undefined). This function should be defined
4075 for any architecture where it is possible the stack could become
4076 misaligned. The utility functions @code{align_down} (for falling
4077 stacks) and @code{align_up} (for rising stacks) will facilitate the
4078 implementation of this function.
4082 @deftypevr {Architecture Variable} int frame_red_zone_size
4084 Some ABIs reserve space beyond the end of the stack for use by leaf
4085 functions without prologue or epilogue or by exception handlers (for
4086 example the OpenRISC 1000).
4088 This is known as a @dfn{red zone} (AMD terminology). The @sc{amd64}
4089 (nee x86-64) ABI documentation refers to the @dfn{red zone} when
4090 describing this scratch area.
4092 The default value is 0. Set this field if the architecture has such a
4093 red zone. The value must be aligned as required by the ABI (see
4094 @code{frame_align} above for an explanation of stack frame alignment).
4098 @node Functions to Access Frame Data
4099 @subsection Functions to Access Frame Data
4101 These functions provide access to key registers and arguments in the
4104 @deftypefn {Architecture Function} CORE_ADDR unwind_pc (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4106 This function is given a pointer to the NEXT stack frame (@pxref{All
4107 About Stack Frames, , All About Stack Frames}, for how frames are
4108 represented) and returns the value of the program counter in the
4109 PREVIOUS frame (i.e.@: the frame of the function that called THIS
4110 one). This is commonly referred to as the @dfn{return address}.
4112 The implementation, which must be frame agnostic (work with any frame),
4113 is typically no more than:
4117 pc = frame_unwind_register_unsigned (next_frame, @var{ARCH}_PC_REGNUM);
4118 return gdbarch_addr_bits_remove (gdbarch, pc);
4123 @deftypefn {Architecture Function} CORE_ADDR unwind_sp (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4125 This function is given a pointer to the NEXT stack frame
4126 (@pxref{All About Stack Frames, , All About Stack Frames} for how
4127 frames are represented) and returns the value of the stack pointer in
4128 the PREVIOUS frame (i.e.@: the frame of the function that called
4131 The implementation, which must be frame agnostic (work with any frame),
4132 is typically no more than:
4136 sp = frame_unwind_register_unsigned (next_frame, @var{ARCH}_SP_REGNUM);
4137 return gdbarch_addr_bits_remove (gdbarch, sp);
4142 @deftypefn {Architecture Function} int frame_num_args (struct gdbarch *@var{gdbarch}, struct frame_info *@var{this_frame})
4144 This function is given a pointer to THIS stack frame (@pxref{All
4145 About Stack Frames, , All About Stack Frames} for how frames are
4146 represented), and returns the number of arguments that are being
4147 passed, or -1 if not known.
4149 The default value is @code{NULL} (undefined), in which case the number of
4150 arguments passed on any stack frame is always unknown. For many
4151 architectures this will be a suitable default.
4155 @node Analyzing Stacks---Frame Sniffers
4156 @subsection Analyzing Stacks---Frame Sniffers
4158 When a program stops, @value{GDBN} needs to construct the chain of
4159 struct @code{frame_info} representing the state of the stack using
4160 appropriate @dfn{sniffers}.
4162 Each architecture requires appropriate sniffers, but they do not form
4163 entries in @code{@w{struct gdbarch}}, since more than one sniffer may
4164 be required and a sniffer may be suitable for more than one
4165 @code{@w{struct gdbarch}}. Instead sniffers are associated with
4166 architectures using the following functions.
4171 @findex frame_unwind_append_sniffer
4172 @code{frame_unwind_append_sniffer} is used to add a new sniffer to
4173 analyze THIS frame when given a pointer to the NEXT frame.
4176 @findex frame_base_append_sniffer
4177 @code{frame_base_append_sniffer} is used to add a new sniffer
4178 which can determine information about the base of a stack frame.
4181 @findex frame_base_set_default
4182 @code{frame_base_set_default} is used to specify the default base
4187 These functions all take a reference to @code{@w{struct gdbarch}}, so
4188 they are associated with a specific architecture. They are usually
4189 called in the @code{gdbarch} initialization function, after the
4190 @code{gdbarch} struct has been set up. Unless a default has been set, the
4191 most recently appended sniffer will be tried first.
4193 The main frame unwinding sniffer (as set by
4194 @code{frame_unwind_append_sniffer)} returns a structure specifying
4195 a set of sniffing functions:
4197 @cindex @code{frame_unwind}
4201 enum frame_type type;
4202 frame_this_id_ftype *this_id;
4203 frame_prev_register_ftype *prev_register;
4204 const struct frame_data *unwind_data;
4205 frame_sniffer_ftype *sniffer;
4206 frame_prev_pc_ftype *prev_pc;
4207 frame_dealloc_cache_ftype *dealloc_cache;
4211 The @code{type} field indicates the type of frame this sniffer can
4212 handle: normal, dummy (@pxref{Functions Creating Dummy Frames, ,
4213 Functions Creating Dummy Frames}), signal handler or sentinel. Signal
4214 handlers sometimes have their own simplified stack structure for
4215 efficiency, so may need their own handlers.
4217 The @code{unwind_data} field holds additional information which may be
4218 relevant to particular types of frame. For example it may hold
4219 additional information for signal handler frames.
4221 The remaining fields define functions that yield different types of
4222 information when given a pointer to the NEXT stack frame. Not all
4223 functions need be provided. If an entry is @code{NULL}, the next sniffer will
4229 @code{this_id} determines the stack pointer and function (code
4230 entry point) for THIS stack frame.
4233 @code{prev_register} determines where the values of registers for
4234 the PREVIOUS stack frame are stored in THIS stack frame.
4237 @code{sniffer} takes a look at THIS frame's registers to
4238 determine if this is the appropriate unwinder.
4241 @code{prev_pc} determines the program counter for THIS
4242 frame. Only needed if the program counter is not an ordinary register
4243 (@pxref{Register Architecture Functions & Variables,
4244 , Functions and Variables Specifying the Register Architecture}).
4247 @code{dealloc_cache} frees any additional memory associated with
4248 the prologue cache for this frame (@pxref{Prologue Caches, , Prologue
4253 In general it is only the @code{this_id} and @code{prev_register}
4254 fields that need be defined for custom sniffers.
4256 The frame base sniffer is much simpler. It is a @code{@w{struct
4257 frame_base}}, which refers to the corresponding @code{frame_unwind}
4258 struct and whose fields refer to functions yielding various addresses
4261 @cindex @code{frame_base}
4265 const struct frame_unwind *unwind;
4266 frame_this_base_ftype *this_base;
4267 frame_this_locals_ftype *this_locals;
4268 frame_this_args_ftype *this_args;
4272 All the functions referred to take a pointer to the NEXT frame as
4273 argument. The function referred to by @code{this_base} returns the
4274 base address of THIS frame, the function referred to by
4275 @code{this_locals} returns the base address of local variables in THIS
4276 frame and the function referred to by @code{this_args} returns the
4277 base address of the function arguments in this frame.
4279 As described above, the base address of a frame is the address
4280 immediately before the start of the NEXT frame. For a falling
4281 stack, this is the lowest address in the frame and for a rising stack
4282 it is the highest address in the frame. For most architectures the
4283 same address is also the base address for local variables and
4284 arguments, in which case the same function can be used for all three
4285 entries@footnote{It is worth noting that if it cannot be determined in any
4286 other way (for example by there being a register with the name
4287 @code{"fp"}), then the result of the @code{this_base} function will be
4288 used as the value of the frame pointer variable @kbd{$fp} in
4289 @value{GDBN}. This is very often not correct (for example with the
4290 OpenRISC 1000, this value is the stack pointer, @kbd{$sp}). In this
4291 case a register (raw or pseudo) with the name @code{"fp"} should be
4292 defined. It will be used in preference as the value of @kbd{$fp}.}.
4294 @node Inferior Call Setup
4295 @section Inferior Call Setup
4296 @cindex calls to the inferior
4299 * About Dummy Frames::
4300 * Functions Creating Dummy Frames::
4303 @node About Dummy Frames
4304 @subsection About Dummy Frames
4305 @cindex dummy frames
4307 @value{GDBN} can call functions in the target code (for example by
4308 using the @kbd{call} or @kbd{print} commands). These functions may be
4309 breakpointed, and it is essential that if a function does hit a
4310 breakpoint, commands like @kbd{backtrace} work correctly.
4312 This is achieved by making the stack look as though the function had
4313 been called from the point where @value{GDBN} had previously stopped.
4314 This requires that @value{GDBN} can set up stack frames appropriate for
4315 such function calls.
4317 @node Functions Creating Dummy Frames
4318 @subsection Functions Creating Dummy Frames
4320 The following functions provide the functionality to set up such
4321 @dfn{dummy} stack frames.
4323 @deftypefn {Architecture Function} CORE_ADDR push_dummy_call (struct gdbarch *@var{gdbarch}, struct value *@var{function}, struct regcache *@var{regcache}, CORE_ADDR @var{bp_addr}, int @var{nargs}, struct value **@var{args}, CORE_ADDR @var{sp}, int @var{struct_return}, CORE_ADDR @var{struct_addr})
4325 This function sets up a dummy stack frame for the function about to be
4326 called. @code{push_dummy_call} is given the arguments to be passed
4327 and must copy them into registers or push them on to the stack as
4328 appropriate for the ABI.
4330 @var{function} is a pointer to the function
4331 that will be called and @var{regcache} the register cache from which
4332 values should be obtained. @var{bp_addr} is the address to which the
4333 function should return (which is breakpointed, so @value{GDBN} can
4334 regain control, hence the name). @var{nargs} is the number of
4335 arguments to pass and @var{args} an array containing the argument
4336 values. @var{struct_return} is non-zero (true) if the function returns
4337 a structure, and if so @var{struct_addr} is the address in which the
4338 structure should be returned.
4340 After calling this function, @value{GDBN} will pass control to the
4341 target at the address of the function, which will find the stack and
4342 registers set up just as expected.
4344 The default value of this function is @code{NULL} (undefined). If the
4345 function is not defined, then @value{GDBN} will not allow the user to
4346 call functions within the target being debugged.
4350 @deftypefn {Architecture Function} {struct frame_id} unwind_dummy_id (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4352 This is the inverse of @code{push_dummy_call} which restores the stack
4353 pointer and program counter after a call to evaluate a function using
4354 a dummy stack frame. The result is a @code{@w{struct frame_id}}, which
4355 contains the value of the stack pointer and program counter to be
4358 The NEXT frame pointer is provided as argument,
4359 @var{next_frame}. THIS frame is the frame of the dummy function,
4360 which can be unwound, to yield the required stack pointer and program
4361 counter from the PREVIOUS frame.
4363 The default value is @code{NULL} (undefined). If @code{push_dummy_call} is
4364 defined, then this function should also be defined.
4368 @deftypefn {Architecture Function} CORE_ADDR push_dummy_code (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{sp}, CORE_ADDR @var{funaddr}, struct value **@var{args}, int @var{nargs}, struct type *@var{value_type}, CORE_ADDR *@var{real_pc}, CORE_ADDR *@var{bp_addr}, struct regcache *@var{regcache})
4370 If this function is not defined (its default value is @code{NULL}), a dummy
4371 call will use the entry point of the currently loaded code on the
4372 target as its return address. A temporary breakpoint will be set
4373 there, so the location must be writable and have room for a
4376 It is possible that this default is not suitable. It might not be
4377 writable (in ROM possibly), or the ABI might require code to be
4378 executed on return from a call to unwind the stack before the
4379 breakpoint is encountered.
4381 If either of these is the case, then push_dummy_code should be defined
4382 to push an instruction sequence onto the end of the stack to which the
4383 dummy call should return.
4385 The arguments are essentially the same as those to
4386 @code{push_dummy_call}. However the function is provided with the
4387 type of the function result, @var{value_type}, @var{bp_addr} is used
4388 to return a value (the address at which the breakpoint instruction
4389 should be inserted) and @var{real pc} is used to specify the resume
4390 address when starting the call sequence. The function should return
4391 the updated innermost stack address.
4394 @emph{Note:} This does require that code in the stack can be executed.
4395 Some Harvard architectures may not allow this.
4400 @node Adding support for debugging core files
4401 @section Adding support for debugging core files
4404 The prerequisite for adding core file support in @value{GDBN} is to have
4405 core file support in BFD.
4407 Once BFD support is available, writing the apropriate
4408 @code{regset_from_core_section} architecture function should be all
4409 that is needed in order to add support for core files in @value{GDBN}.
4411 @node Defining Other Architecture Features
4412 @section Defining Other Architecture Features
4414 This section describes other functions and values in @code{gdbarch},
4415 together with some useful macros, that you can use to define the
4416 target architecture.
4420 @item CORE_ADDR gdbarch_addr_bits_remove (@var{gdbarch}, @var{addr})
4421 @findex gdbarch_addr_bits_remove
4422 If a raw machine instruction address includes any bits that are not
4423 really part of the address, then this function is used to zero those bits in
4424 @var{addr}. This is only used for addresses of instructions, and even then not
4427 For example, the two low-order bits of the PC on the Hewlett-Packard PA
4428 2.0 architecture contain the privilege level of the corresponding
4429 instruction. Since instructions must always be aligned on four-byte
4430 boundaries, the processor masks out these bits to generate the actual
4431 address of the instruction. @code{gdbarch_addr_bits_remove} would then for
4432 example look like that:
4434 arch_addr_bits_remove (CORE_ADDR addr)
4436 return (addr &= ~0x3);
4440 @item int address_class_name_to_type_flags (@var{gdbarch}, @var{name}, @var{type_flags_ptr})
4441 @findex address_class_name_to_type_flags
4442 If @var{name} is a valid address class qualifier name, set the @code{int}
4443 referenced by @var{type_flags_ptr} to the mask representing the qualifier
4444 and return 1. If @var{name} is not a valid address class qualifier name,
4447 The value for @var{type_flags_ptr} should be one of
4448 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
4449 possibly some combination of these values or'd together.
4450 @xref{Target Architecture Definition, , Address Classes}.
4452 @item int address_class_name_to_type_flags_p (@var{gdbarch})
4453 @findex address_class_name_to_type_flags_p
4454 Predicate which indicates whether @code{address_class_name_to_type_flags}
4457 @item int gdbarch_address_class_type_flags (@var{gdbarch}, @var{byte_size}, @var{dwarf2_addr_class})
4458 @findex gdbarch_address_class_type_flags
4459 Given a pointers byte size (as described by the debug information) and
4460 the possible @code{DW_AT_address_class} value, return the type flags
4461 used by @value{GDBN} to represent this address class. The value
4462 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
4463 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
4464 values or'd together.
4465 @xref{Target Architecture Definition, , Address Classes}.
4467 @item int gdbarch_address_class_type_flags_p (@var{gdbarch})
4468 @findex gdbarch_address_class_type_flags_p
4469 Predicate which indicates whether @code{gdbarch_address_class_type_flags_p} has
4472 @item const char *gdbarch_address_class_type_flags_to_name (@var{gdbarch}, @var{type_flags})
4473 @findex gdbarch_address_class_type_flags_to_name
4474 Return the name of the address class qualifier associated with the type
4475 flags given by @var{type_flags}.
4477 @item int gdbarch_address_class_type_flags_to_name_p (@var{gdbarch})
4478 @findex gdbarch_address_class_type_flags_to_name_p
4479 Predicate which indicates whether @code{gdbarch_address_class_type_flags_to_name} has been defined.
4480 @xref{Target Architecture Definition, , Address Classes}.
4482 @item void gdbarch_address_to_pointer (@var{gdbarch}, @var{type}, @var{buf}, @var{addr})
4483 @findex gdbarch_address_to_pointer
4484 Store in @var{buf} a pointer of type @var{type} representing the address
4485 @var{addr}, in the appropriate format for the current architecture.
4486 This function may safely assume that @var{type} is either a pointer or a
4487 C@t{++} reference type.
4488 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
4490 @item int gdbarch_believe_pcc_promotion (@var{gdbarch})
4491 @findex gdbarch_believe_pcc_promotion
4492 Used to notify if the compiler promotes a @code{short} or @code{char}
4493 parameter to an @code{int}, but still reports the parameter as its
4494 original type, rather than the promoted type.
4496 @item gdbarch_bits_big_endian (@var{gdbarch})
4497 @findex gdbarch_bits_big_endian
4498 This is used if the numbering of bits in the targets does @strong{not} match
4499 the endianism of the target byte order. A value of 1 means that the bits
4500 are numbered in a big-endian bit order, 0 means little-endian.
4502 @item set_gdbarch_bits_big_endian (@var{gdbarch}, @var{bits_big_endian})
4503 @findex set_gdbarch_bits_big_endian
4504 Calling set_gdbarch_bits_big_endian with a value of 1 indicates that the
4505 bits in the target are numbered in a big-endian bit order, 0 indicates
4510 This is the character array initializer for the bit pattern to put into
4511 memory where a breakpoint is set. Although it's common to use a trap
4512 instruction for a breakpoint, it's not required; for instance, the bit
4513 pattern could be an invalid instruction. The breakpoint must be no
4514 longer than the shortest instruction of the architecture.
4516 @code{BREAKPOINT} has been deprecated in favor of
4517 @code{gdbarch_breakpoint_from_pc}.
4519 @item BIG_BREAKPOINT
4520 @itemx LITTLE_BREAKPOINT
4521 @findex LITTLE_BREAKPOINT
4522 @findex BIG_BREAKPOINT
4523 Similar to BREAKPOINT, but used for bi-endian targets.
4525 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
4526 favor of @code{gdbarch_breakpoint_from_pc}.
4528 @item const gdb_byte *gdbarch_breakpoint_from_pc (@var{gdbarch}, @var{pcptr}, @var{lenptr})
4529 @findex gdbarch_breakpoint_from_pc
4530 @anchor{gdbarch_breakpoint_from_pc} Use the program counter to determine the
4531 contents and size of a breakpoint instruction. It returns a pointer to
4532 a static string of bytes that encode a breakpoint instruction, stores the
4533 length of the string to @code{*@var{lenptr}}, and adjusts the program
4534 counter (if necessary) to point to the actual memory location where the
4535 breakpoint should be inserted. On input, the program counter
4536 (@code{*@var{pcptr}} is the encoded inferior's PC register. If software
4537 breakpoints are supported, the function sets this argument to the PC's
4538 plain address. If software breakpoints are not supported, the function
4539 returns NULL instead of the encoded breakpoint instruction.
4541 Although it is common to use a trap instruction for a breakpoint, it's
4542 not required; for instance, the bit pattern could be an invalid
4543 instruction. The breakpoint must be no longer than the shortest
4544 instruction of the architecture.
4546 Provided breakpoint bytes can be also used by @code{bp_loc_is_permanent} to
4547 detect permanent breakpoints. @code{gdbarch_breakpoint_from_pc} should return
4548 an unchanged memory copy if it was called for a location with permanent
4549 breakpoint as some architectures use breakpoint instructions containing
4550 arbitrary parameter value.
4552 Replaces all the other @var{BREAKPOINT} macros.
4554 @item int gdbarch_memory_insert_breakpoint (@var{gdbarch}, @var{bp_tgt})
4555 @itemx gdbarch_memory_remove_breakpoint (@var{gdbarch}, @var{bp_tgt})
4556 @findex gdbarch_memory_remove_breakpoint
4557 @findex gdbarch_memory_insert_breakpoint
4558 Insert or remove memory based breakpoints. Reasonable defaults
4559 (@code{default_memory_insert_breakpoint} and
4560 @code{default_memory_remove_breakpoint} respectively) have been
4561 provided so that it is not necessary to set these for most
4562 architectures. Architectures which may want to set
4563 @code{gdbarch_memory_insert_breakpoint} and @code{gdbarch_memory_remove_breakpoint} will likely have instructions that are oddly sized or are not stored in a
4564 conventional manner.
4566 It may also be desirable (from an efficiency standpoint) to define
4567 custom breakpoint insertion and removal routines if
4568 @code{gdbarch_breakpoint_from_pc} needs to read the target's memory for some
4571 @item CORE_ADDR gdbarch_adjust_breakpoint_address (@var{gdbarch}, @var{bpaddr})
4572 @findex gdbarch_adjust_breakpoint_address
4573 @cindex breakpoint address adjusted
4574 Given an address at which a breakpoint is desired, return a breakpoint
4575 address adjusted to account for architectural constraints on
4576 breakpoint placement. This method is not needed by most targets.
4578 The FR-V target (see @file{frv-tdep.c}) requires this method.
4579 The FR-V is a VLIW architecture in which a number of RISC-like
4580 instructions are grouped (packed) together into an aggregate
4581 instruction or instruction bundle. When the processor executes
4582 one of these bundles, the component instructions are executed
4585 In the course of optimization, the compiler may group instructions
4586 from distinct source statements into the same bundle. The line number
4587 information associated with one of the latter statements will likely
4588 refer to some instruction other than the first one in the bundle. So,
4589 if the user attempts to place a breakpoint on one of these latter
4590 statements, @value{GDBN} must be careful to @emph{not} place the break
4591 instruction on any instruction other than the first one in the bundle.
4592 (Remember though that the instructions within a bundle execute
4593 in parallel, so the @emph{first} instruction is the instruction
4594 at the lowest address and has nothing to do with execution order.)
4596 The FR-V's @code{gdbarch_adjust_breakpoint_address} method will adjust a
4597 breakpoint's address by scanning backwards for the beginning of
4598 the bundle, returning the address of the bundle.
4600 Since the adjustment of a breakpoint may significantly alter a user's
4601 expectation, @value{GDBN} prints a warning when an adjusted breakpoint
4602 is initially set and each time that that breakpoint is hit.
4604 @item int gdbarch_call_dummy_location (@var{gdbarch})
4605 @findex gdbarch_call_dummy_location
4606 See the file @file{inferior.h}.
4608 This method has been replaced by @code{gdbarch_push_dummy_code}
4609 (@pxref{gdbarch_push_dummy_code}).
4611 @item int gdbarch_cannot_fetch_register (@var{gdbarch}, @var{regum})
4612 @findex gdbarch_cannot_fetch_register
4613 This function should return nonzero if @var{regno} cannot be fetched
4614 from an inferior process.
4616 @item int gdbarch_cannot_store_register (@var{gdbarch}, @var{regnum})
4617 @findex gdbarch_cannot_store_register
4618 This function should return nonzero if @var{regno} should not be
4619 written to the target. This is often the case for program counters,
4620 status words, and other special registers. This function returns 0 as
4621 default so that @value{GDBN} will assume that all registers may be written.
4623 @item int gdbarch_convert_register_p (@var{gdbarch}, @var{regnum}, struct type *@var{type})
4624 @findex gdbarch_convert_register_p
4625 Return non-zero if register @var{regnum} represents data values of type
4626 @var{type} in a non-standard form.
4627 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4629 @item int gdbarch_fp0_regnum (@var{gdbarch})
4630 @findex gdbarch_fp0_regnum
4631 This function returns the number of the first floating point register,
4632 if the machine has such registers. Otherwise, it returns -1.
4634 @item CORE_ADDR gdbarch_decr_pc_after_break (@var{gdbarch})
4635 @findex gdbarch_decr_pc_after_break
4636 This function shall return the amount by which to decrement the PC after the
4637 program encounters a breakpoint. This is often the number of bytes in
4638 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
4640 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
4641 @findex DISABLE_UNSETTABLE_BREAK
4642 If defined, this should evaluate to 1 if @var{addr} is in a shared
4643 library in which breakpoints cannot be set and so should be disabled.
4645 @item int gdbarch_dwarf2_reg_to_regnum (@var{gdbarch}, @var{dwarf2_regnr})
4646 @findex gdbarch_dwarf2_reg_to_regnum
4647 Convert DWARF2 register number @var{dwarf2_regnr} into @value{GDBN} regnum.
4648 If not defined, no conversion will be performed.
4650 @item int gdbarch_ecoff_reg_to_regnum (@var{gdbarch}, @var{ecoff_regnr})
4651 @findex gdbarch_ecoff_reg_to_regnum
4652 Convert ECOFF register number @var{ecoff_regnr} into @value{GDBN} regnum. If
4653 not defined, no conversion will be performed.
4655 @item GCC_COMPILED_FLAG_SYMBOL
4656 @itemx GCC2_COMPILED_FLAG_SYMBOL
4657 @findex GCC2_COMPILED_FLAG_SYMBOL
4658 @findex GCC_COMPILED_FLAG_SYMBOL
4659 If defined, these are the names of the symbols that @value{GDBN} will
4660 look for to detect that GCC compiled the file. The default symbols
4661 are @code{gcc_compiled.} and @code{gcc2_compiled.},
4662 respectively. (Currently only defined for the Delta 68.)
4664 @item gdbarch_get_longjmp_target
4665 @findex gdbarch_get_longjmp_target
4666 This function determines the target PC address that @code{longjmp}
4667 will jump to, assuming that we have just stopped at a @code{longjmp}
4668 breakpoint. It takes a @code{CORE_ADDR *} as argument, and stores the
4669 target PC value through this pointer. It examines the current state
4670 of the machine as needed, typically by using a manually-determined
4671 offset into the @code{jmp_buf}. (While we might like to get the offset
4672 from the target's @file{jmpbuf.h}, that header file cannot be assumed
4673 to be available when building a cross-debugger.)
4675 @item DEPRECATED_IBM6000_TARGET
4676 @findex DEPRECATED_IBM6000_TARGET
4677 Shows that we are configured for an IBM RS/6000 system. This
4678 conditional should be eliminated (FIXME) and replaced by
4679 feature-specific macros. It was introduced in haste and we are
4680 repenting at leisure.
4682 @item I386_USE_GENERIC_WATCHPOINTS
4683 An x86-based target can define this to use the generic x86 watchpoint
4684 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4686 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{addr})
4687 @findex gdbarch_in_function_epilogue_p
4688 Returns non-zero if the given @var{addr} is in the epilogue of a function.
4689 The epilogue of a function is defined as the part of a function where
4690 the stack frame of the function already has been destroyed up to the
4691 final `return from function call' instruction.
4693 @item int gdbarch_in_solib_return_trampoline (@var{gdbarch}, @var{pc}, @var{name})
4694 @findex gdbarch_in_solib_return_trampoline
4695 Define this function to return nonzero if the program is stopped in the
4696 trampoline that returns from a shared library.
4698 @item target_so_ops.in_dynsym_resolve_code (@var{pc})
4699 @findex in_dynsym_resolve_code
4700 Define this to return nonzero if the program is stopped in the
4703 @item SKIP_SOLIB_RESOLVER (@var{pc})
4704 @findex SKIP_SOLIB_RESOLVER
4705 Define this to evaluate to the (nonzero) address at which execution
4706 should continue to get past the dynamic linker's symbol resolution
4707 function. A zero value indicates that it is not important or necessary
4708 to set a breakpoint to get through the dynamic linker and that single
4709 stepping will suffice.
4711 @item CORE_ADDR gdbarch_integer_to_address (@var{gdbarch}, @var{type}, @var{buf})
4712 @findex gdbarch_integer_to_address
4713 @cindex converting integers to addresses
4714 Define this when the architecture needs to handle non-pointer to address
4715 conversions specially. Converts that value to an address according to
4716 the current architectures conventions.
4718 @emph{Pragmatics: When the user copies a well defined expression from
4719 their source code and passes it, as a parameter, to @value{GDBN}'s
4720 @code{print} command, they should get the same value as would have been
4721 computed by the target program. Any deviation from this rule can cause
4722 major confusion and annoyance, and needs to be justified carefully. In
4723 other words, @value{GDBN} doesn't really have the freedom to do these
4724 conversions in clever and useful ways. It has, however, been pointed
4725 out that users aren't complaining about how @value{GDBN} casts integers
4726 to pointers; they are complaining that they can't take an address from a
4727 disassembly listing and give it to @code{x/i}. Adding an architecture
4728 method like @code{gdbarch_integer_to_address} certainly makes it possible for
4729 @value{GDBN} to ``get it right'' in all circumstances.}
4731 @xref{Target Architecture Definition, , Pointers Are Not Always
4734 @item CORE_ADDR gdbarch_pointer_to_address (@var{gdbarch}, @var{type}, @var{buf})
4735 @findex gdbarch_pointer_to_address
4736 Assume that @var{buf} holds a pointer of type @var{type}, in the
4737 appropriate format for the current architecture. Return the byte
4738 address the pointer refers to.
4739 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
4741 @item void gdbarch_register_to_value(@var{gdbarch}, @var{frame}, @var{regnum}, @var{type}, @var{fur})
4742 @findex gdbarch_register_to_value
4743 Convert the raw contents of register @var{regnum} into a value of type
4745 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4747 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
4748 @findex REGISTER_CONVERT_TO_VIRTUAL
4749 Convert the value of register @var{reg} from its raw form to its virtual
4751 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
4753 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
4754 @findex REGISTER_CONVERT_TO_RAW
4755 Convert the value of register @var{reg} from its virtual form to its raw
4757 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
4759 @item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size})
4760 @findex regset_from_core_section
4761 Return the appropriate register set for a core file section with name
4762 @var{sect_name} and size @var{sect_size}.
4764 @item SOFTWARE_SINGLE_STEP_P()
4765 @findex SOFTWARE_SINGLE_STEP_P
4766 Define this as 1 if the target does not have a hardware single-step
4767 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
4769 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p})
4770 @findex SOFTWARE_SINGLE_STEP
4771 A function that inserts or removes (depending on
4772 @var{insert_breakpoints_p}) breakpoints at each possible destinations of
4773 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
4776 @item set_gdbarch_sofun_address_maybe_missing (@var{gdbarch}, @var{set})
4777 @findex set_gdbarch_sofun_address_maybe_missing
4778 Somebody clever observed that, the more actual addresses you have in the
4779 debug information, the more time the linker has to spend relocating
4780 them. So whenever there's some other way the debugger could find the
4781 address it needs, you should omit it from the debug info, to make
4784 Calling @code{set_gdbarch_sofun_address_maybe_missing} with a non-zero
4785 argument @var{set} indicates that a particular set of hacks of this sort
4786 are in use, affecting @code{N_SO} and @code{N_FUN} entries in stabs-format
4787 debugging information. @code{N_SO} stabs mark the beginning and ending
4788 addresses of compilation units in the text segment. @code{N_FUN} stabs
4789 mark the starts and ends of functions.
4791 In this case, @value{GDBN} assumes two things:
4795 @code{N_FUN} stabs have an address of zero. Instead of using those
4796 addresses, you should find the address where the function starts by
4797 taking the function name from the stab, and then looking that up in the
4798 minsyms (the linker/assembler symbol table). In other words, the stab
4799 has the name, and the linker/assembler symbol table is the only place
4800 that carries the address.
4803 @code{N_SO} stabs have an address of zero, too. You just look at the
4804 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab, and
4805 guess the starting and ending addresses of the compilation unit from them.
4808 @item int gdbarch_stabs_argument_has_addr (@var{gdbarch}, @var{type})
4809 @findex gdbarch_stabs_argument_has_addr
4810 @anchor{gdbarch_stabs_argument_has_addr} Define this function to return
4811 nonzero if a function argument of type @var{type} is passed by reference
4814 @item CORE_ADDR gdbarch_push_dummy_call (@var{gdbarch}, @var{function}, @var{regcache}, @var{bp_addr}, @var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
4815 @findex gdbarch_push_dummy_call
4816 @anchor{gdbarch_push_dummy_call} Define this to push the dummy frame's call to
4817 the inferior function onto the stack. In addition to pushing @var{nargs}, the
4818 code should push @var{struct_addr} (when @var{struct_return} is non-zero), and
4819 the return address (@var{bp_addr}, in inferior's PC register encoding).
4821 @var{function} is a pointer to a @code{struct value}; on architectures that use
4822 function descriptors, this contains the function descriptor value.
4824 Returns the updated top-of-stack pointer.
4826 @item CORE_ADDR gdbarch_push_dummy_code (@var{gdbarch}, @var{sp}, @var{funaddr}, @var{using_gcc}, @var{args}, @var{nargs}, @var{value_type}, @var{real_pc}, @var{bp_addr}, @var{regcache})
4827 @findex gdbarch_push_dummy_code
4828 @anchor{gdbarch_push_dummy_code} Given a stack based call dummy, push the
4829 instruction sequence (including space for a breakpoint) to which the
4830 called function should return.
4832 Set @var{bp_addr} to the address at which the breakpoint instruction
4833 should be inserted (in inferior's PC register encoding), @var{real_pc} to the
4834 resume address when starting the call sequence, and return the updated
4835 inner-most stack address.
4837 By default, the stack is grown sufficient to hold a frame-aligned
4838 (@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address
4839 reserved for that breakpoint (in inferior's PC register encoding), and
4840 @var{real_pc} set to @var{funaddr}.
4842 This method replaces @w{@code{gdbarch_call_dummy_location (@var{gdbarch})}}.
4844 @item int gdbarch_sdb_reg_to_regnum (@var{gdbarch}, @var{sdb_regnr})
4845 @findex gdbarch_sdb_reg_to_regnum
4846 Use this function to convert sdb register @var{sdb_regnr} into @value{GDBN}
4847 regnum. If not defined, no conversion will be done.
4849 @item enum return_value_convention gdbarch_return_value (struct gdbarch *@var{gdbarch}, struct type *@var{valtype}, struct regcache *@var{regcache}, void *@var{readbuf}, const void *@var{writebuf})
4850 @findex gdbarch_return_value
4851 @anchor{gdbarch_return_value} Given a function with a return-value of
4852 type @var{rettype}, return which return-value convention that function
4855 @value{GDBN} currently recognizes two function return-value conventions:
4856 @code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found
4857 in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return
4858 value is found in memory and the address of that memory location is
4859 passed in as the function's first parameter.
4861 If the register convention is being used, and @var{writebuf} is
4862 non-@code{NULL}, also copy the return-value in @var{writebuf} into
4865 If the register convention is being used, and @var{readbuf} is
4866 non-@code{NULL}, also copy the return value from @var{regcache} into
4867 @var{readbuf} (@var{regcache} contains a copy of the registers from the
4868 just returned function).
4870 @emph{Maintainer note: This method replaces separate predicate, extract,
4871 store methods. By having only one method, the logic needed to determine
4872 the return-value convention need only be implemented in one place. If
4873 @value{GDBN} were written in an @sc{oo} language, this method would
4874 instead return an object that knew how to perform the register
4875 return-value extract and store.}
4877 @emph{Maintainer note: This method does not take a @var{gcc_p}
4878 parameter, and such a parameter should not be added. If an architecture
4879 that requires per-compiler or per-function information be identified,
4880 then the replacement of @var{rettype} with @code{struct value}
4881 @var{function} should be pursued.}
4883 @emph{Maintainer note: The @var{regcache} parameter limits this methods
4884 to the inner most frame. While replacing @var{regcache} with a
4885 @code{struct frame_info} @var{frame} parameter would remove that
4886 limitation there has yet to be a demonstrated need for such a change.}
4888 @item void gdbarch_skip_permanent_breakpoint (@var{gdbarch}, @var{regcache})
4889 @findex gdbarch_skip_permanent_breakpoint
4890 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
4891 steps over a breakpoint by removing it, stepping one instruction, and
4892 re-inserting the breakpoint. However, permanent breakpoints are
4893 hardwired into the inferior, and can't be removed, so this strategy
4894 doesn't work. Calling @code{gdbarch_skip_permanent_breakpoint} adjusts the
4895 processor's state so that execution will resume just after the breakpoint.
4896 This function does the right thing even when the breakpoint is in the delay slot
4897 of a branch or jump.
4899 @item CORE_ADDR gdbarch_skip_trampoline_code (@var{gdbarch}, @var{frame}, @var{pc})
4900 @findex gdbarch_skip_trampoline_code
4901 If the target machine has trampoline code that sits between callers and
4902 the functions being called, then define this function to return a new PC
4903 that is at the start of the real function.
4905 @item int gdbarch_deprecated_fp_regnum (@var{gdbarch})
4906 @findex gdbarch_deprecated_fp_regnum
4907 If the frame pointer is in a register, use this function to return the
4908 number of that register.
4910 @item int gdbarch_stab_reg_to_regnum (@var{gdbarch}, @var{stab_regnr})
4911 @findex gdbarch_stab_reg_to_regnum
4912 Use this function to convert stab register @var{stab_regnr} into @value{GDBN}
4913 regnum. If not defined, no conversion will be done.
4915 @item TARGET_CHAR_BIT
4916 @findex TARGET_CHAR_BIT
4917 Number of bits in a char; defaults to 8.
4919 @item int gdbarch_char_signed (@var{gdbarch})
4920 @findex gdbarch_char_signed
4921 Non-zero if @code{char} is normally signed on this architecture; zero if
4922 it should be unsigned.
4924 The ISO C standard requires the compiler to treat @code{char} as
4925 equivalent to either @code{signed char} or @code{unsigned char}; any
4926 character in the standard execution set is supposed to be positive.
4927 Most compilers treat @code{char} as signed, but @code{char} is unsigned
4928 on the IBM S/390, RS6000, and PowerPC targets.
4930 @item int gdbarch_double_bit (@var{gdbarch})
4931 @findex gdbarch_double_bit
4932 Number of bits in a double float; defaults to @w{@code{8 * TARGET_CHAR_BIT}}.
4934 @item int gdbarch_float_bit (@var{gdbarch})
4935 @findex gdbarch_float_bit
4936 Number of bits in a float; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4938 @item int gdbarch_int_bit (@var{gdbarch})
4939 @findex gdbarch_int_bit
4940 Number of bits in an integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4942 @item int gdbarch_long_bit (@var{gdbarch})
4943 @findex gdbarch_long_bit
4944 Number of bits in a long integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4946 @item int gdbarch_long_double_bit (@var{gdbarch})
4947 @findex gdbarch_long_double_bit
4948 Number of bits in a long double float;
4949 defaults to @w{@code{2 * gdbarch_double_bit (@var{gdbarch})}}.
4951 @item int gdbarch_long_long_bit (@var{gdbarch})
4952 @findex gdbarch_long_long_bit
4953 Number of bits in a long long integer; defaults to
4954 @w{@code{2 * gdbarch_long_bit (@var{gdbarch})}}.
4956 @item int gdbarch_ptr_bit (@var{gdbarch})
4957 @findex gdbarch_ptr_bit
4958 Number of bits in a pointer; defaults to
4959 @w{@code{gdbarch_int_bit (@var{gdbarch})}}.
4961 @item int gdbarch_short_bit (@var{gdbarch})
4962 @findex gdbarch_short_bit
4963 Number of bits in a short integer; defaults to @w{@code{2 * TARGET_CHAR_BIT}}.
4965 @item void gdbarch_virtual_frame_pointer (@var{gdbarch}, @var{pc}, @var{frame_regnum}, @var{frame_offset})
4966 @findex gdbarch_virtual_frame_pointer
4967 Returns a @code{(@var{register}, @var{offset})} pair representing the virtual
4968 frame pointer in use at the code address @var{pc}. If virtual frame
4969 pointers are not used, a default definition simply returns
4970 @code{gdbarch_deprecated_fp_regnum} (or @code{gdbarch_sp_regnum}, if
4971 no frame pointer is defined), with an offset of zero.
4973 @c need to explain virtual frame pointers, they are recorded in agent
4974 @c expressions for tracepoints
4976 @item TARGET_HAS_HARDWARE_WATCHPOINTS
4977 If non-zero, the target has support for hardware-assisted
4978 watchpoints. @xref{Algorithms, watchpoints}, for more details and
4979 other related macros.
4981 @item int gdbarch_print_insn (@var{gdbarch}, @var{vma}, @var{info})
4982 @findex gdbarch_print_insn
4983 This is the function used by @value{GDBN} to print an assembly
4984 instruction. It prints the instruction at address @var{vma} in
4985 debugged memory and returns the length of the instruction, in bytes.
4986 This usually points to a function in the @code{opcodes} library
4987 (@pxref{Support Libraries, ,Opcodes}). @var{info} is a structure (of
4988 type @code{disassemble_info}) defined in the header file
4989 @file{include/dis-asm.h}, and used to pass information to the
4990 instruction decoding routine.
4992 @item frame_id gdbarch_dummy_id (@var{gdbarch}, @var{frame})
4993 @findex gdbarch_dummy_id
4994 @anchor{gdbarch_dummy_id} Given @var{frame} return a @w{@code{struct
4995 frame_id}} that uniquely identifies an inferior function call's dummy
4996 frame. The value returned must match the dummy frame stack value
4997 previously saved by @code{call_function_by_hand}.
4999 @item void gdbarch_value_to_register (@var{gdbarch}, @var{frame}, @var{type}, @var{buf})
5000 @findex gdbarch_value_to_register
5001 Convert a value of type @var{type} into the raw contents of a register.
5002 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
5006 Motorola M68K target conditionals.
5010 Define this to be the 4-bit location of the breakpoint trap vector. If
5011 not defined, it will default to @code{0xf}.
5013 @item REMOTE_BPT_VECTOR
5014 Defaults to @code{1}.
5018 @node Adding a New Target
5019 @section Adding a New Target
5021 @cindex adding a target
5022 The following files add a target to @value{GDBN}:
5025 @cindex target dependent files
5027 @item gdb/@var{ttt}-tdep.c
5028 Contains any miscellaneous code required for this target machine. On
5029 some machines it doesn't exist at all.
5031 @item gdb/@var{arch}-tdep.c
5032 @itemx gdb/@var{arch}-tdep.h
5033 This is required to describe the basic layout of the target machine's
5034 processor chip (registers, stack, etc.). It can be shared among many
5035 targets that use the same processor architecture.
5039 (Target header files such as
5040 @file{gdb/config/@var{arch}/tm-@var{ttt}.h},
5041 @file{gdb/config/@var{arch}/tm-@var{arch}.h}, and
5042 @file{config/tm-@var{os}.h} are no longer used.)
5044 @findex _initialize_@var{arch}_tdep
5045 A @value{GDBN} description for a new architecture, arch is created by
5046 defining a global function @code{_initialize_@var{arch}_tdep}, by
5047 convention in the source file @file{@var{arch}-tdep.c}. For
5048 example, in the case of the OpenRISC 1000, this function is called
5049 @code{_initialize_or1k_tdep} and is found in the file
5052 The object file resulting from compiling this source file, which will
5053 contain the implementation of the
5054 @code{_initialize_@var{arch}_tdep} function is specified in the
5055 @value{GDBN} @file{configure.tgt} file, which includes a large case
5056 statement pattern matching against the @code{--target} option of the
5057 @kbd{configure} script.
5060 @emph{Note:} If the architecture requires multiple source files, the
5061 corresponding binaries should be included in
5062 @file{configure.tgt}. However if there are header files, the
5063 dependencies on these will not be picked up from the entries in
5064 @file{configure.tgt}. The @file{Makefile.in} file will need extending to
5065 show these dependencies.
5068 @findex gdbarch_register
5069 A new struct gdbarch, defining the new architecture, is created within
5070 the @code{_initialize_@var{arch}_tdep} function by calling
5071 @code{gdbarch_register}:
5074 void gdbarch_register (enum bfd_architecture architecture,
5075 gdbarch_init_ftype *init_func,
5076 gdbarch_dump_tdep_ftype *tdep_dump_func);
5079 This function has been described fully in an earlier
5080 section. @xref{How an Architecture is Represented, , How an
5081 Architecture is Represented}.
5083 The new @code{@w{struct gdbarch}} should contain implementations of
5084 the necessary functions (described in the previous sections) to
5085 describe the basic layout of the target machine's processor chip
5086 (registers, stack, etc.). It can be shared among many targets that use
5087 the same processor architecture.
5089 @node Target Descriptions
5090 @chapter Target Descriptions
5091 @cindex target descriptions
5093 The target architecture definition (@pxref{Target Architecture Definition})
5094 contains @value{GDBN}'s hard-coded knowledge about an architecture. For
5095 some platforms, it is handy to have more flexible knowledge about a specific
5096 instance of the architecture---for instance, a processor or development board.
5097 @dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN}
5098 more about what their target supports, or for the target to tell @value{GDBN}
5101 For details on writing, automatically supplying, and manually selecting
5102 target descriptions, see @ref{Target Descriptions, , , gdb,
5103 Debugging with @value{GDBN}}. This section will cover some related
5104 topics about the @value{GDBN} internals.
5107 * Target Descriptions Implementation::
5108 * Adding Target Described Register Support::
5111 @node Target Descriptions Implementation
5112 @section Target Descriptions Implementation
5113 @cindex target descriptions, implementation
5115 Before @value{GDBN} connects to a new target, or runs a new program on
5116 an existing target, it discards any existing target description and
5117 reverts to a default gdbarch. Then, after connecting, it looks for a
5118 new target description by calling @code{target_find_description}.
5120 A description may come from a user specified file (XML), the remote
5121 @samp{qXfer:features:read} packet (also XML), or from any custom
5122 @code{to_read_description} routine in the target vector. For instance,
5123 the remote target supports guessing whether a MIPS target is 32-bit or
5124 64-bit based on the size of the @samp{g} packet.
5126 If any target description is found, @value{GDBN} creates a new gdbarch
5127 incorporating the description by calling @code{gdbarch_update_p}. Any
5128 @samp{<architecture>} element is handled first, to determine which
5129 architecture's gdbarch initialization routine is called to create the
5130 new architecture. Then the initialization routine is called, and has
5131 a chance to adjust the constructed architecture based on the contents
5132 of the target description. For instance, it can recognize any
5133 properties set by a @code{to_read_description} routine. Also
5134 see @ref{Adding Target Described Register Support}.
5136 @node Adding Target Described Register Support
5137 @section Adding Target Described Register Support
5138 @cindex target descriptions, adding register support
5140 Target descriptions can report additional registers specific to an
5141 instance of the target. But it takes a little work in the architecture
5142 specific routines to support this.
5144 A target description must either have no registers or a complete
5145 set---this avoids complexity in trying to merge standard registers
5146 with the target defined registers. It is the architecture's
5147 responsibility to validate that a description with registers has
5148 everything it needs. To keep architecture code simple, the same
5149 mechanism is used to assign fixed internal register numbers to
5152 If @code{tdesc_has_registers} returns 1, the description contains
5153 registers. The architecture's @code{gdbarch_init} routine should:
5158 Call @code{tdesc_data_alloc} to allocate storage, early, before
5159 searching for a matching gdbarch or allocating a new one.
5162 Use @code{tdesc_find_feature} to locate standard features by name.
5165 Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices}
5166 to locate the expected registers in the standard features.
5169 Return @code{NULL} if a required feature is missing, or if any standard
5170 feature is missing expected registers. This will produce a warning that
5171 the description was incomplete.
5174 Free the allocated data before returning, unless @code{tdesc_use_registers}
5178 Call @code{set_gdbarch_num_regs} as usual, with a number higher than any
5179 fixed number passed to @code{tdesc_numbered_register}.
5182 Call @code{tdesc_use_registers} after creating a new gdbarch, before
5187 After @code{tdesc_use_registers} has been called, the architecture's
5188 @code{register_name}, @code{register_type}, and @code{register_reggroup_p}
5189 routines will not be called; that information will be taken from
5190 the target description. @code{num_regs} may be increased to account
5191 for any additional registers in the description.
5193 Pseudo-registers require some extra care:
5198 Using @code{tdesc_numbered_register} allows the architecture to give
5199 constant register numbers to standard architectural registers, e.g.@:
5200 as an @code{enum} in @file{@var{arch}-tdep.h}. But because
5201 pseudo-registers are always numbered above @code{num_regs},
5202 which may be increased by the description, constant numbers
5203 can not be used for pseudos. They must be numbered relative to
5204 @code{num_regs} instead.
5207 The description will not describe pseudo-registers, so the
5208 architecture must call @code{set_tdesc_pseudo_register_name},
5209 @code{set_tdesc_pseudo_register_type}, and
5210 @code{set_tdesc_pseudo_register_reggroup_p} to supply routines
5211 describing pseudo registers. These routines will be passed
5212 internal register numbers, so the same routines used for the
5213 gdbarch equivalents are usually suitable.
5218 @node Target Vector Definition
5220 @chapter Target Vector Definition
5221 @cindex target vector
5223 The target vector defines the interface between @value{GDBN}'s
5224 abstract handling of target systems, and the nitty-gritty code that
5225 actually exercises control over a process or a serial port.
5226 @value{GDBN} includes some 30-40 different target vectors; however,
5227 each configuration of @value{GDBN} includes only a few of them.
5230 * Managing Execution State::
5231 * Existing Targets::
5234 @node Managing Execution State
5235 @section Managing Execution State
5236 @cindex execution state
5238 A target vector can be completely inactive (not pushed on the target
5239 stack), active but not running (pushed, but not connected to a fully
5240 manifested inferior), or completely active (pushed, with an accessible
5241 inferior). Most targets are only completely inactive or completely
5242 active, but some support persistent connections to a target even
5243 when the target has exited or not yet started.
5245 For example, connecting to the simulator using @code{target sim} does
5246 not create a running program. Neither registers nor memory are
5247 accessible until @code{run}. Similarly, after @code{kill}, the
5248 program can not continue executing. But in both cases @value{GDBN}
5249 remains connected to the simulator, and target-specific commands
5250 are directed to the simulator.
5252 A target which only supports complete activation should push itself
5253 onto the stack in its @code{to_open} routine (by calling
5254 @code{push_target}), and unpush itself from the stack in its
5255 @code{to_mourn_inferior} routine (by calling @code{unpush_target}).
5257 A target which supports both partial and complete activation should
5258 still call @code{push_target} in @code{to_open}, but not call
5259 @code{unpush_target} in @code{to_mourn_inferior}. Instead, it should
5260 call either @code{target_mark_running} or @code{target_mark_exited}
5261 in its @code{to_open}, depending on whether the target is fully active
5262 after connection. It should also call @code{target_mark_running} any
5263 time the inferior becomes fully active (e.g.@: in
5264 @code{to_create_inferior} and @code{to_attach}), and
5265 @code{target_mark_exited} when the inferior becomes inactive (in
5266 @code{to_mourn_inferior}). The target should also make sure to call
5267 @code{target_mourn_inferior} from its @code{to_kill}, to return the
5268 target to inactive state.
5270 @node Existing Targets
5271 @section Existing Targets
5274 @subsection File Targets
5276 Both executables and core files have target vectors.
5278 @subsection Standard Protocol and Remote Stubs
5280 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code that
5281 runs in the target system. @value{GDBN} provides several sample
5282 @dfn{stubs} that can be integrated into target programs or operating
5283 systems for this purpose; they are named @file{@var{cpu}-stub.c}. Many
5284 operating systems, embedded targets, emulators, and simulators already
5285 have a @value{GDBN} stub built into them, and maintenance of the remote
5286 protocol must be careful to preserve compatibility.
5288 The @value{GDBN} user's manual describes how to put such a stub into
5289 your target code. What follows is a discussion of integrating the
5290 SPARC stub into a complicated operating system (rather than a simple
5291 program), by Stu Grossman, the author of this stub.
5293 The trap handling code in the stub assumes the following upon entry to
5298 %l1 and %l2 contain pc and npc respectively at the time of the trap;
5304 you are in the correct trap window.
5307 As long as your trap handler can guarantee those conditions, then there
5308 is no reason why you shouldn't be able to ``share'' traps with the stub.
5309 The stub has no requirement that it be jumped to directly from the
5310 hardware trap vector. That is why it calls @code{exceptionHandler()},
5311 which is provided by the external environment. For instance, this could
5312 set up the hardware traps to actually execute code which calls the stub
5313 first, and then transfers to its own trap handler.
5315 For the most point, there probably won't be much of an issue with
5316 ``sharing'' traps, as the traps we use are usually not used by the kernel,
5317 and often indicate unrecoverable error conditions. Anyway, this is all
5318 controlled by a table, and is trivial to modify. The most important
5319 trap for us is for @code{ta 1}. Without that, we can't single step or
5320 do breakpoints. Everything else is unnecessary for the proper operation
5321 of the debugger/stub.
5323 From reading the stub, it's probably not obvious how breakpoints work.
5324 They are simply done by deposit/examine operations from @value{GDBN}.
5326 @subsection ROM Monitor Interface
5328 @subsection Custom Protocols
5330 @subsection Transport Layer
5332 @subsection Builtin Simulator
5335 @node Native Debugging
5337 @chapter Native Debugging
5338 @cindex native debugging
5340 Several files control @value{GDBN}'s configuration for native support:
5344 @item gdb/config/@var{arch}/@var{xyz}.mh
5345 Specifies Makefile fragments needed by a @emph{native} configuration on
5346 machine @var{xyz}. In particular, this lists the required
5347 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
5348 Also specifies the header file which describes native support on
5349 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
5350 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
5351 @samp{NAT_CDEPS}, @samp{NAT_GENERATED_FILES}, etc.; see @file{Makefile.in}.
5353 @emph{Maintainer's note: The @file{.mh} suffix is because this file
5354 originally contained @file{Makefile} fragments for hosting @value{GDBN}
5355 on machine @var{xyz}. While the file is no longer used for this
5356 purpose, the @file{.mh} suffix remains. Perhaps someone will
5357 eventually rename these fragments so that they have a @file{.mn}
5360 @item gdb/config/@var{arch}/nm-@var{xyz}.h
5361 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
5362 macro definitions describing the native system environment, such as
5363 child process control and core file support.
5365 @item gdb/@var{xyz}-nat.c
5366 Contains any miscellaneous C code required for this native support of
5367 this machine. On some machines it doesn't exist at all.
5370 There are some ``generic'' versions of routines that can be used by
5371 various systems. These can be customized in various ways by macros
5372 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
5373 the @var{xyz} host, you can just include the generic file's name (with
5374 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
5376 Otherwise, if your machine needs custom support routines, you will need
5377 to write routines that perform the same functions as the generic file.
5378 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
5379 into @code{NATDEPFILES}.
5383 This contains the @emph{target_ops vector} that supports Unix child
5384 processes on systems which use ptrace and wait to control the child.
5387 This contains the @emph{target_ops vector} that supports Unix child
5388 processes on systems which use /proc to control the child.
5391 This does the low-level grunge that uses Unix system calls to do a ``fork
5392 and exec'' to start up a child process.
5395 This is the low level interface to inferior processes for systems using
5396 the Unix @code{ptrace} call in a vanilla way.
5405 @section shared libraries
5407 @section Native Conditionals
5408 @cindex native conditionals
5410 When @value{GDBN} is configured and compiled, various macros are
5411 defined or left undefined, to control compilation when the host and
5412 target systems are the same. These macros should be defined (or left
5413 undefined) in @file{nm-@var{system}.h}.
5417 @item I386_USE_GENERIC_WATCHPOINTS
5418 An x86-based machine can define this to use the generic x86 watchpoint
5419 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
5421 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
5423 Define this to expand into an expression that will cause the symbols in
5424 @var{filename} to be added to @value{GDBN}'s symbol table. If
5425 @var{readsyms} is zero symbols are not read but any necessary low level
5426 processing for @var{filename} is still done.
5428 @item SOLIB_CREATE_INFERIOR_HOOK
5429 @findex SOLIB_CREATE_INFERIOR_HOOK
5430 Define this to expand into any shared-library-relocation code that you
5431 want to be run just after the child process has been forked.
5433 @item START_INFERIOR_TRAPS_EXPECTED
5434 @findex START_INFERIOR_TRAPS_EXPECTED
5435 When starting an inferior, @value{GDBN} normally expects to trap
5437 the shell execs, and once when the program itself execs. If the actual
5438 number of traps is something other than 2, then define this macro to
5439 expand into the number expected.
5443 @node Support Libraries
5445 @chapter Support Libraries
5450 BFD provides support for @value{GDBN} in several ways:
5453 @item identifying executable and core files
5454 BFD will identify a variety of file types, including a.out, coff, and
5455 several variants thereof, as well as several kinds of core files.
5457 @item access to sections of files
5458 BFD parses the file headers to determine the names, virtual addresses,
5459 sizes, and file locations of all the various named sections in files
5460 (such as the text section or the data section). @value{GDBN} simply
5461 calls BFD to read or write section @var{x} at byte offset @var{y} for
5464 @item specialized core file support
5465 BFD provides routines to determine the failing command name stored in a
5466 core file, the signal with which the program failed, and whether a core
5467 file matches (i.e.@: could be a core dump of) a particular executable
5470 @item locating the symbol information
5471 @value{GDBN} uses an internal interface of BFD to determine where to find the
5472 symbol information in an executable file or symbol-file. @value{GDBN} itself
5473 handles the reading of symbols, since BFD does not ``understand'' debug
5474 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
5479 @cindex opcodes library
5481 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
5482 library because it's also used in binutils, for @file{objdump}).
5485 @cindex readline library
5486 The @code{readline} library provides a set of functions for use by applications
5487 that allow users to edit command lines as they are typed in.
5490 @cindex @code{libiberty} library
5492 The @code{libiberty} library provides a set of functions and features
5493 that integrate and improve on functionality found in modern operating
5494 systems. Broadly speaking, such features can be divided into three
5495 groups: supplemental functions (functions that may be missing in some
5496 environments and operating systems), replacement functions (providing
5497 a uniform and easier to use interface for commonly used standard
5498 functions), and extensions (which provide additional functionality
5499 beyond standard functions).
5501 @value{GDBN} uses various features provided by the @code{libiberty}
5502 library, for instance the C@t{++} demangler, the @acronym{IEEE}
5503 floating format support functions, the input options parser
5504 @samp{getopt}, the @samp{obstack} extension, and other functions.
5506 @subsection @code{obstacks} in @value{GDBN}
5507 @cindex @code{obstacks}
5509 The obstack mechanism provides a convenient way to allocate and free
5510 chunks of memory. Each obstack is a pool of memory that is managed
5511 like a stack. Objects (of any nature, size and alignment) are
5512 allocated and freed in a @acronym{LIFO} fashion on an obstack (see
5513 @code{libiberty}'s documentation for a more detailed explanation of
5516 The most noticeable use of the @code{obstacks} in @value{GDBN} is in
5517 object files. There is an obstack associated with each internal
5518 representation of an object file. Lots of things get allocated on
5519 these @code{obstacks}: dictionary entries, blocks, blockvectors,
5520 symbols, minimal symbols, types, vectors of fundamental types, class
5521 fields of types, object files section lists, object files section
5522 offset lists, line tables, symbol tables, partial symbol tables,
5523 string tables, symbol table private data, macros tables, debug
5524 information sections and entries, import and export lists (som),
5525 unwind information (hppa), dwarf2 location expressions data. Plus
5526 various strings such as directory names strings, debug format strings,
5529 An essential and convenient property of all data on @code{obstacks} is
5530 that memory for it gets allocated (with @code{obstack_alloc}) at
5531 various times during a debugging session, but it is released all at
5532 once using the @code{obstack_free} function. The @code{obstack_free}
5533 function takes a pointer to where in the stack it must start the
5534 deletion from (much like the cleanup chains have a pointer to where to
5535 start the cleanups). Because of the stack like structure of the
5536 @code{obstacks}, this allows to free only a top portion of the
5537 obstack. There are a few instances in @value{GDBN} where such thing
5538 happens. Calls to @code{obstack_free} are done after some local data
5539 is allocated to the obstack. Only the local data is deleted from the
5540 obstack. Of course this assumes that nothing between the
5541 @code{obstack_alloc} and the @code{obstack_free} allocates anything
5542 else on the same obstack. For this reason it is best and safest to
5543 use temporary @code{obstacks}.
5545 Releasing the whole obstack is also not safe per se. It is safe only
5546 under the condition that we know the @code{obstacks} memory is no
5547 longer needed. In @value{GDBN} we get rid of the @code{obstacks} only
5548 when we get rid of the whole objfile(s), for instance upon reading a
5552 @cindex regular expressions library
5563 @item SIGN_EXTEND_CHAR
5565 @item SWITCH_ENUM_BUG
5574 @section Array Containers
5575 @cindex Array Containers
5578 Often it is necessary to manipulate a dynamic array of a set of
5579 objects. C forces some bookkeeping on this, which can get cumbersome
5580 and repetitive. The @file{vec.h} file contains macros for defining
5581 and using a typesafe vector type. The functions defined will be
5582 inlined when compiling, and so the abstraction cost should be zero.
5583 Domain checks are added to detect programming errors.
5585 An example use would be an array of symbols or section information.
5586 The array can be grown as symbols are read in (or preallocated), and
5587 the accessor macros provided keep care of all the necessary
5588 bookkeeping. Because the arrays are type safe, there is no danger of
5589 accidentally mixing up the contents. Think of these as C++ templates,
5590 but implemented in C.
5592 Because of the different behavior of structure objects, scalar objects
5593 and of pointers, there are three flavors of vector, one for each of
5594 these variants. Both the structure object and pointer variants pass
5595 pointers to objects around --- in the former case the pointers are
5596 stored into the vector and in the latter case the pointers are
5597 dereferenced and the objects copied into the vector. The scalar
5598 object variant is suitable for @code{int}-like objects, and the vector
5599 elements are returned by value.
5601 There are both @code{index} and @code{iterate} accessors. The iterator
5602 returns a boolean iteration condition and updates the iteration
5603 variable passed by reference. Because the iterator will be inlined,
5604 the address-of can be optimized away.
5606 The vectors are implemented using the trailing array idiom, thus they
5607 are not resizeable without changing the address of the vector object
5608 itself. This means you cannot have variables or fields of vector type
5609 --- always use a pointer to a vector. The one exception is the final
5610 field of a structure, which could be a vector type. You will have to
5611 use the @code{embedded_size} & @code{embedded_init} calls to create
5612 such objects, and they will probably not be resizeable (so don't use
5613 the @dfn{safe} allocation variants). The trailing array idiom is used
5614 (rather than a pointer to an array of data), because, if we allow
5615 @code{NULL} to also represent an empty vector, empty vectors occupy
5616 minimal space in the structure containing them.
5618 Each operation that increases the number of active elements is
5619 available in @dfn{quick} and @dfn{safe} variants. The former presumes
5620 that there is sufficient allocated space for the operation to succeed
5621 (it dies if there is not). The latter will reallocate the vector, if
5622 needed. Reallocation causes an exponential increase in vector size.
5623 If you know you will be adding N elements, it would be more efficient
5624 to use the reserve operation before adding the elements with the
5625 @dfn{quick} operation. This will ensure there are at least as many
5626 elements as you ask for, it will exponentially increase if there are
5627 too few spare slots. If you want reserve a specific number of slots,
5628 but do not want the exponential increase (for instance, you know this
5629 is the last allocation), use a negative number for reservation. You
5630 can also create a vector of a specific size from the get go.
5632 You should prefer the push and pop operations, as they append and
5633 remove from the end of the vector. If you need to remove several items
5634 in one go, use the truncate operation. The insert and remove
5635 operations allow you to change elements in the middle of the vector.
5636 There are two remove operations, one which preserves the element
5637 ordering @code{ordered_remove}, and one which does not
5638 @code{unordered_remove}. The latter function copies the end element
5639 into the removed slot, rather than invoke a memmove operation. The
5640 @code{lower_bound} function will determine where to place an item in
5641 the array using insert that will maintain sorted order.
5643 If you need to directly manipulate a vector, then the @code{address}
5644 accessor will return the address of the start of the vector. Also the
5645 @code{space} predicate will tell you whether there is spare capacity in the
5646 vector. You will not normally need to use these two functions.
5648 Vector types are defined using a
5649 @code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector
5650 type are declared using a @code{VEC(@var{typename})} macro. The
5651 characters @code{O}, @code{P} and @code{I} indicate whether
5652 @var{typename} is an object (@code{O}), pointer (@code{P}) or integral
5653 (@code{I}) type. Be careful to pick the correct one, as you'll get an
5654 awkward and inefficient API if you use the wrong one. There is a
5655 check, which results in a compile-time warning, for the @code{P} and
5656 @code{I} versions, but there is no check for the @code{O} versions, as
5657 that is not possible in plain C.
5659 An example of their use would be,
5662 DEF_VEC_P(tree); // non-managed tree vector.
5665 VEC(tree) *v; // A (pointer to) a vector of tree pointers.
5668 struct my_struct *s;
5670 if (VEC_length(tree, s->v)) @{ we have some contents @}
5671 VEC_safe_push(tree, s->v, decl); // append some decl onto the end
5672 for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
5673 @{ do something with elt @}
5677 The @file{vec.h} file provides details on how to invoke the various
5678 accessors provided. They are enumerated here:
5682 Return the number of items in the array,
5685 Return true if the array has no elements.
5689 Return the last or arbitrary item in the array.
5692 Access an array element and indicate whether the array has been
5697 Create and destroy an array.
5699 @item VEC_embedded_size
5700 @itemx VEC_embedded_init
5701 Helpers for embedding an array as the final element of another struct.
5707 Return the amount of free space in an array.
5710 Ensure a certain amount of free space.
5712 @item VEC_quick_push
5713 @itemx VEC_safe_push
5714 Append to an array, either assuming the space is available, or making
5718 Remove the last item from an array.
5721 Remove several items from the end of an array.
5724 Add several items to the end of an array.
5727 Overwrite an item in the array.
5729 @item VEC_quick_insert
5730 @itemx VEC_safe_insert
5731 Insert an item into the middle of the array. Either the space must
5732 already exist, or the space is created.
5734 @item VEC_ordered_remove
5735 @itemx VEC_unordered_remove
5736 Remove an item from the array, preserving order or not.
5738 @item VEC_block_remove
5739 Remove a set of items from the array.
5742 Provide the address of the first element.
5744 @item VEC_lower_bound
5745 Binary search the array.
5751 @node Coding Standards
5753 @chapter Coding Standards
5754 @cindex coding standards
5756 @section @value{GDBN} C Coding Standards
5758 @value{GDBN} follows the GNU coding standards, as described in
5759 @file{etc/standards.texi}. This file is also available for anonymous
5760 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
5761 of the standard; in general, when the GNU standard recommends a practice
5762 but does not require it, @value{GDBN} requires it.
5764 @value{GDBN} follows an additional set of coding standards specific to
5765 @value{GDBN}, as described in the following sections.
5769 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
5772 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
5774 @subsection Formatting
5776 @cindex source code formatting
5777 The standard GNU recommendations for formatting must be followed
5778 strictly. Any @value{GDBN}-specific deviation from GNU
5779 recomendations is described below.
5781 A function declaration should not have its name in column zero. A
5782 function definition should have its name in column zero.
5786 static void foo (void);
5794 @emph{Pragmatics: This simplifies scripting. Function definitions can
5795 be found using @samp{^function-name}.}
5797 There must be a space between a function or macro name and the opening
5798 parenthesis of its argument list (except for macro definitions, as
5799 required by C). There must not be a space after an open paren/bracket
5800 or before a close paren/bracket.
5802 While additional whitespace is generally helpful for reading, do not use
5803 more than one blank line to separate blocks, and avoid adding whitespace
5804 after the end of a program line (as of 1/99, some 600 lines had
5805 whitespace after the semicolon). Excess whitespace causes difficulties
5806 for @code{diff} and @code{patch} utilities.
5808 Pointers are declared using the traditional K&R C style:
5822 In addition, whitespace around casts and unary operators should follow
5823 the following guidelines:
5825 @multitable @columnfractions .2 .2 .8
5826 @item Use... @tab ...instead of @tab
5835 @item @code{(foo) x}
5840 @tab (pointer dereference)
5843 Any two or more lines in code should be wrapped in braces, even if
5844 they are comments, as they look like separate statements:
5849 /* Return success. */
5859 /* Return success. */
5863 @subsection Comments
5865 @cindex comment formatting
5866 The standard GNU requirements on comments must be followed strictly.
5868 Block comments must appear in the following form, with no @code{/*}- or
5869 @code{*/}-only lines, and no leading @code{*}:
5872 /* Wait for control to return from inferior to debugger. If inferior
5873 gets a signal, we may decide to start it up again instead of
5874 returning. That is why there is a loop in this function. When
5875 this function actually returns it means the inferior should be left
5876 stopped and @value{GDBN} should read more commands. */
5879 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5880 comment works correctly, and @kbd{M-q} fills the block consistently.)
5882 Put a blank line between the block comments preceding function or
5883 variable definitions, and the definition itself.
5885 In general, put function-body comments on lines by themselves, rather
5886 than trying to fit them into the 20 characters left at the end of a
5887 line, since either the comment or the code will inevitably get longer
5888 than will fit, and then somebody will have to move it anyhow.
5892 @cindex C data types
5893 Code must not depend on the sizes of C data types, the format of the
5894 host's floating point numbers, the alignment of anything, or the order
5895 of evaluation of expressions.
5897 @cindex function usage
5898 Use functions freely. There are only a handful of compute-bound areas
5899 in @value{GDBN} that might be affected by the overhead of a function
5900 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5901 limited by the target interface (whether serial line or system call).
5903 However, use functions with moderation. A thousand one-line functions
5904 are just as hard to understand as a single thousand-line function.
5906 @emph{Macros are bad, M'kay.}
5907 (But if you have to use a macro, make sure that the macro arguments are
5908 protected with parentheses.)
5912 Declarations like @samp{struct foo *} should be used in preference to
5913 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5915 @subsection Function Prototypes
5916 @cindex function prototypes
5918 Prototypes must be used when both @emph{declaring} and @emph{defining}
5919 a function. Prototypes for @value{GDBN} functions must include both the
5920 argument type and name, with the name matching that used in the actual
5921 function definition.
5923 All external functions should have a declaration in a header file that
5924 callers include, except for @code{_initialize_*} functions, which must
5925 be external so that @file{init.c} construction works, but shouldn't be
5926 visible to random source files.
5928 Where a source file needs a forward declaration of a static function,
5929 that declaration must appear in a block near the top of the source file.
5931 @subsection File Names
5933 Any file used when building the core of @value{GDBN} must be in lower
5934 case. Any file used when building the core of @value{GDBN} must be 8.3
5935 unique. These requirements apply to both source and generated files.
5937 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5938 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5939 is introduced to the build process both @file{Makefile.in} and
5940 @file{configure.in} need to be modified accordingly. Compare the
5941 convoluted conversion process needed to transform @file{COPYING} into
5942 @file{copying.c} with the conversion needed to transform
5943 @file{version.in} into @file{version.c}.}
5945 Any file non 8.3 compliant file (that is not used when building the core
5946 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5948 @emph{Pragmatics: This is clearly a compromise.}
5950 When @value{GDBN} has a local version of a system header file (ex
5951 @file{string.h}) the file name based on the POSIX header prefixed with
5952 @file{gdb_} (@file{gdb_string.h}). These headers should be relatively
5953 independent: they should use only macros defined by @file{configure},
5954 the compiler, or the host; they should include only system headers; they
5955 should refer only to system types. They may be shared between multiple
5956 programs, e.g.@: @value{GDBN} and @sc{gdbserver}.
5958 For other files @samp{-} is used as the separator.
5960 @subsection Include Files
5962 A @file{.c} file should include @file{defs.h} first.
5964 A @file{.c} file should directly include the @code{.h} file of every
5965 declaration and/or definition it directly refers to. It cannot rely on
5968 A @file{.h} file should directly include the @code{.h} file of every
5969 declaration and/or definition it directly refers to. It cannot rely on
5970 indirect inclusion. Exception: The file @file{defs.h} does not need to
5971 be directly included.
5973 An external declaration should only appear in one include file.
5975 An external declaration should never appear in a @code{.c} file.
5976 Exception: a declaration for the @code{_initialize} function that
5977 pacifies @option{-Wmissing-declaration}.
5979 A @code{typedef} definition should only appear in one include file.
5981 An opaque @code{struct} declaration can appear in multiple @file{.h}
5982 files. Where possible, a @file{.h} file should use an opaque
5983 @code{struct} declaration instead of an include.
5985 All @file{.h} files should be wrapped in:
5988 #ifndef INCLUDE_FILE_NAME_H
5989 #define INCLUDE_FILE_NAME_H
5994 @section @value{GDBN} Python Coding Standards
5996 @value{GDBN} follows the published @code{Python} coding standards in
5997 @uref{http://www.python.org/dev/peps/pep-0008/, @code{PEP008}}.
5999 In addition, the guidelines in the
6000 @uref{http://google-styleguide.googlecode.com/svn/trunk/pyguide.html,
6001 Google Python Style Guide} are also followed where they do not
6002 conflict with @code{PEP008}.
6004 @subsection @value{GDBN}-specific exceptions
6006 There are a few exceptions to the published standards.
6007 They exist mainly for consistency with the @code{C} standards.
6009 @c It is expected that there are a few more exceptions,
6010 @c so we use itemize here.
6015 Use @code{FIXME} instead of @code{TODO}.
6019 @node Misc Guidelines
6021 @chapter Misc Guidelines
6023 This chapter covers topics that are lower-level than the major
6024 algorithms of @value{GDBN}.
6029 Cleanups are a structured way to deal with things that need to be done
6032 When your code does something (e.g., @code{xmalloc} some memory, or
6033 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
6034 the memory or @code{close} the file), it can make a cleanup. The
6035 cleanup will be done at some future point: when the command is finished
6036 and control returns to the top level; when an error occurs and the stack
6037 is unwound; or when your code decides it's time to explicitly perform
6038 cleanups. Alternatively you can elect to discard the cleanups you
6044 @item struct cleanup *@var{old_chain};
6045 Declare a variable which will hold a cleanup chain handle.
6047 @findex make_cleanup
6048 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
6049 Make a cleanup which will cause @var{function} to be called with
6050 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
6051 handle that can later be passed to @code{do_cleanups} or
6052 @code{discard_cleanups}. Unless you are going to call
6053 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
6054 from @code{make_cleanup}.
6057 @item do_cleanups (@var{old_chain});
6058 Do all cleanups added to the chain since the corresponding
6059 @code{make_cleanup} call was made.
6061 @findex discard_cleanups
6062 @item discard_cleanups (@var{old_chain});
6063 Same as @code{do_cleanups} except that it just removes the cleanups from
6064 the chain and does not call the specified functions.
6067 Cleanups are implemented as a chain. The handle returned by
6068 @code{make_cleanups} includes the cleanup passed to the call and any
6069 later cleanups appended to the chain (but not yet discarded or
6073 make_cleanup (a, 0);
6075 struct cleanup *old = make_cleanup (b, 0);
6083 will call @code{c()} and @code{b()} but will not call @code{a()}. The
6084 cleanup that calls @code{a()} will remain in the cleanup chain, and will
6085 be done later unless otherwise discarded.@refill
6087 Your function should explicitly do or discard the cleanups it creates.
6088 Failing to do this leads to non-deterministic behavior since the caller
6089 will arbitrarily do or discard your functions cleanups. This need leads
6090 to two common cleanup styles.
6092 The first style is try/finally. Before it exits, your code-block calls
6093 @code{do_cleanups} with the old cleanup chain and thus ensures that your
6094 code-block's cleanups are always performed. For instance, the following
6095 code-segment avoids a memory leak problem (even when @code{error} is
6096 called and a forced stack unwind occurs) by ensuring that the
6097 @code{xfree} will always be called:
6100 struct cleanup *old = make_cleanup (null_cleanup, 0);
6101 data = xmalloc (sizeof blah);
6102 make_cleanup (xfree, data);
6107 The second style is try/except. Before it exits, your code-block calls
6108 @code{discard_cleanups} with the old cleanup chain and thus ensures that
6109 any created cleanups are not performed. For instance, the following
6110 code segment, ensures that the file will be closed but only if there is
6114 FILE *file = fopen ("afile", "r");
6115 struct cleanup *old = make_cleanup (close_file, file);
6117 discard_cleanups (old);
6121 Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify
6122 that they ``should not be called when cleanups are not in place''. This
6123 means that any actions you need to reverse in the case of an error or
6124 interruption must be on the cleanup chain before you call these
6125 functions, since they might never return to your code (they
6126 @samp{longjmp} instead).
6128 @section Per-architecture module data
6129 @cindex per-architecture module data
6130 @cindex multi-arch data
6131 @cindex data-pointer, per-architecture/per-module
6133 The multi-arch framework includes a mechanism for adding module
6134 specific per-architecture data-pointers to the @code{struct gdbarch}
6135 architecture object.
6137 A module registers one or more per-architecture data-pointers using:
6139 @deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init})
6140 @var{pre_init} is used to, on-demand, allocate an initial value for a
6141 per-architecture data-pointer using the architecture's obstack (passed
6142 in as a parameter). Since @var{pre_init} can be called during
6143 architecture creation, it is not parameterized with the architecture.
6144 and must not call modules that use per-architecture data.
6147 @deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init})
6148 @var{post_init} is used to obtain an initial value for a
6149 per-architecture data-pointer @emph{after}. Since @var{post_init} is
6150 always called after architecture creation, it both receives the fully
6151 initialized architecture and is free to call modules that use
6152 per-architecture data (care needs to be taken to ensure that those
6153 other modules do not try to call back to this module as that will
6154 create in cycles in the initialization call graph).
6157 These functions return a @code{struct gdbarch_data} that is used to
6158 identify the per-architecture data-pointer added for that module.
6160 The per-architecture data-pointer is accessed using the function:
6162 @deftypefn {Architecture Function} {void *} gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
6163 Given the architecture @var{arch} and module data handle
6164 @var{data_handle} (returned by @code{gdbarch_data_register_pre_init}
6165 or @code{gdbarch_data_register_post_init}), this function returns the
6166 current value of the per-architecture data-pointer. If the data
6167 pointer is @code{NULL}, it is first initialized by calling the
6168 corresponding @var{pre_init} or @var{post_init} method.
6171 The examples below assume the following definitions:
6174 struct nozel @{ int total; @};
6175 static struct gdbarch_data *nozel_handle;
6178 A module can extend the architecture vector, adding additional
6179 per-architecture data, using the @var{pre_init} method. The module's
6180 per-architecture data is then initialized during architecture
6183 In the below, the module's per-architecture @emph{nozel} is added. An
6184 architecture can specify its nozel by calling @code{set_gdbarch_nozel}
6185 from @code{gdbarch_init}.
6189 nozel_pre_init (struct obstack *obstack)
6191 struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
6198 set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
6200 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
6201 data->total = nozel;
6205 A module can on-demand create architecture dependent data structures
6206 using @code{post_init}.
6208 In the below, the nozel's total is computed on-demand by
6209 @code{nozel_post_init} using information obtained from the
6214 nozel_post_init (struct gdbarch *gdbarch)
6216 struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
6217 nozel->total = gdbarch@dots{} (gdbarch);
6224 nozel_total (struct gdbarch *gdbarch)
6226 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
6231 @section Wrapping Output Lines
6232 @cindex line wrap in output
6235 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
6236 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
6237 added in places that would be good breaking points. The utility
6238 routines will take care of actually wrapping if the line width is
6241 The argument to @code{wrap_here} is an indentation string which is
6242 printed @emph{only} if the line breaks there. This argument is saved
6243 away and used later. It must remain valid until the next call to
6244 @code{wrap_here} or until a newline has been printed through the
6245 @code{*_filtered} functions. Don't pass in a local variable and then
6248 It is usually best to call @code{wrap_here} after printing a comma or
6249 space. If you call it before printing a space, make sure that your
6250 indentation properly accounts for the leading space that will print if
6251 the line wraps there.
6253 Any function or set of functions that produce filtered output must
6254 finish by printing a newline, to flush the wrap buffer, before switching
6255 to unfiltered (@code{printf}) output. Symbol reading routines that
6256 print warnings are a good example.
6258 @section Memory Management
6260 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
6261 @code{calloc}, @code{free} and @code{asprintf}.
6263 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
6264 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
6265 these functions do not return when the memory pool is empty. Instead,
6266 they unwind the stack using cleanups. These functions return
6267 @code{NULL} when requested to allocate a chunk of memory of size zero.
6269 @emph{Pragmatics: By using these functions, the need to check every
6270 memory allocation is removed. These functions provide portable
6273 @value{GDBN} does not use the function @code{free}.
6275 @value{GDBN} uses the function @code{xfree} to return memory to the
6276 memory pool. Consistent with ISO-C, this function ignores a request to
6277 free a @code{NULL} pointer.
6279 @emph{Pragmatics: On some systems @code{free} fails when passed a
6280 @code{NULL} pointer.}
6282 @value{GDBN} can use the non-portable function @code{alloca} for the
6283 allocation of small temporary values (such as strings).
6285 @emph{Pragmatics: This function is very non-portable. Some systems
6286 restrict the memory being allocated to no more than a few kilobytes.}
6288 @value{GDBN} uses the string function @code{xstrdup} and the print
6289 function @code{xstrprintf}.
6291 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
6292 functions such as @code{sprintf} are very prone to buffer overflow
6296 @section Compiler Warnings
6297 @cindex compiler warnings
6299 With few exceptions, developers should avoid the configuration option
6300 @samp{--disable-werror} when building @value{GDBN}. The exceptions
6301 are listed in the file @file{gdb/MAINTAINERS}. The default, when
6302 building with @sc{gcc}, is @samp{--enable-werror}.
6304 This option causes @value{GDBN} (when built using GCC) to be compiled
6305 with a carefully selected list of compiler warning flags. Any warnings
6306 from those flags are treated as errors.
6308 The current list of warning flags includes:
6312 Recommended @sc{gcc} warnings.
6314 @item -Wdeclaration-after-statement
6316 @sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
6317 code, but @sc{gcc} 2.x and @sc{c89} do not.
6319 @item -Wpointer-arith
6321 @item -Wformat-nonliteral
6322 Non-literal format strings, with a few exceptions, are bugs - they
6323 might contain unintended user-supplied format specifiers.
6324 Since @value{GDBN} uses the @code{format printf} attribute on all
6325 @code{printf} like functions this checks not just @code{printf} calls
6326 but also calls to functions such as @code{fprintf_unfiltered}.
6328 @item -Wno-pointer-sign
6329 In version 4.0, GCC began warning about pointer argument passing or
6330 assignment even when the source and destination differed only in
6331 signedness. However, most @value{GDBN} code doesn't distinguish
6332 carefully between @code{char} and @code{unsigned char}. In early 2006
6333 the @value{GDBN} developers decided correcting these warnings wasn't
6334 worth the time it would take.
6336 @item -Wno-unused-parameter
6337 Due to the way that @value{GDBN} is implemented many functions have
6338 unused parameters. Consequently this warning is avoided. The macro
6339 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
6340 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
6345 @itemx -Wno-char-subscripts
6346 These are warnings which might be useful for @value{GDBN}, but are
6347 currently too noisy to enable with @samp{-Werror}.
6351 @section Internal Error Recovery
6353 During its execution, @value{GDBN} can encounter two types of errors.
6354 User errors and internal errors. User errors include not only a user
6355 entering an incorrect command but also problems arising from corrupt
6356 object files and system errors when interacting with the target.
6357 Internal errors include situations where @value{GDBN} has detected, at
6358 run time, a corrupt or erroneous situation.
6360 When reporting an internal error, @value{GDBN} uses
6361 @code{internal_error} and @code{gdb_assert}.
6363 @value{GDBN} must not call @code{abort} or @code{assert}.
6365 @emph{Pragmatics: There is no @code{internal_warning} function. Either
6366 the code detected a user error, recovered from it and issued a
6367 @code{warning} or the code failed to correctly recover from the user
6368 error and issued an @code{internal_error}.}
6370 @section Command Names
6372 GDB U/I commands are written @samp{foo-bar}, not @samp{foo_bar}.
6374 @section Clean Design and Portable Implementation
6377 In addition to getting the syntax right, there's the little question of
6378 semantics. Some things are done in certain ways in @value{GDBN} because long
6379 experience has shown that the more obvious ways caused various kinds of
6382 @cindex assumptions about targets
6383 You can't assume the byte order of anything that comes from a target
6384 (including @var{value}s, object files, and instructions). Such things
6385 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
6386 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
6387 such as @code{bfd_get_32}.
6389 You can't assume that you know what interface is being used to talk to
6390 the target system. All references to the target must go through the
6391 current @code{target_ops} vector.
6393 You can't assume that the host and target machines are the same machine
6394 (except in the ``native'' support modules). In particular, you can't
6395 assume that the target machine's header files will be available on the
6396 host machine. Target code must bring along its own header files --
6397 written from scratch or explicitly donated by their owner, to avoid
6401 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
6402 to write the code portably than to conditionalize it for various
6405 @cindex system dependencies
6406 New @code{#ifdef}'s which test for specific compilers or manufacturers
6407 or operating systems are unacceptable. All @code{#ifdef}'s should test
6408 for features. The information about which configurations contain which
6409 features should be segregated into the configuration files. Experience
6410 has proven far too often that a feature unique to one particular system
6411 often creeps into other systems; and that a conditional based on some
6412 predefined macro for your current system will become worthless over
6413 time, as new versions of your system come out that behave differently
6414 with regard to this feature.
6416 Adding code that handles specific architectures, operating systems,
6417 target interfaces, or hosts, is not acceptable in generic code.
6419 @cindex portable file name handling
6420 @cindex file names, portability
6421 One particularly notorious area where system dependencies tend to
6422 creep in is handling of file names. The mainline @value{GDBN} code
6423 assumes Posix semantics of file names: absolute file names begin with
6424 a forward slash @file{/}, slashes are used to separate leading
6425 directories, case-sensitive file names. These assumptions are not
6426 necessarily true on non-Posix systems such as MS-Windows. To avoid
6427 system-dependent code where you need to take apart or construct a file
6428 name, use the following portable macros:
6431 @findex HAVE_DOS_BASED_FILE_SYSTEM
6432 @item HAVE_DOS_BASED_FILE_SYSTEM
6433 This preprocessing symbol is defined to a non-zero value on hosts
6434 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
6435 symbol to write conditional code which should only be compiled for
6438 @findex IS_DIR_SEPARATOR
6439 @item IS_DIR_SEPARATOR (@var{c})
6440 Evaluates to a non-zero value if @var{c} is a directory separator
6441 character. On Unix and GNU/Linux systems, only a slash @file{/} is
6442 such a character, but on Windows, both @file{/} and @file{\} will
6445 @findex IS_ABSOLUTE_PATH
6446 @item IS_ABSOLUTE_PATH (@var{file})
6447 Evaluates to a non-zero value if @var{file} is an absolute file name.
6448 For Unix and GNU/Linux hosts, a name which begins with a slash
6449 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
6450 @file{x:\bar} are also absolute file names.
6452 @findex FILENAME_CMP
6453 @item FILENAME_CMP (@var{f1}, @var{f2})
6454 Calls a function which compares file names @var{f1} and @var{f2} as
6455 appropriate for the underlying host filesystem. For Posix systems,
6456 this simply calls @code{strcmp}; on case-insensitive filesystems it
6457 will call @code{strcasecmp} instead.
6459 @findex DIRNAME_SEPARATOR
6460 @item DIRNAME_SEPARATOR
6461 Evaluates to a character which separates directories in
6462 @code{PATH}-style lists, typically held in environment variables.
6463 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
6465 @findex SLASH_STRING
6467 This evaluates to a constant string you should use to produce an
6468 absolute filename from leading directories and the file's basename.
6469 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
6470 @code{"\\"} for some Windows-based ports.
6473 In addition to using these macros, be sure to use portable library
6474 functions whenever possible. For example, to extract a directory or a
6475 basename part from a file name, use the @code{dirname} and
6476 @code{basename} library functions (available in @code{libiberty} for
6477 platforms which don't provide them), instead of searching for a slash
6478 with @code{strrchr}.
6480 Another way to generalize @value{GDBN} along a particular interface is with an
6481 attribute struct. For example, @value{GDBN} has been generalized to handle
6482 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
6483 by defining the @code{target_ops} structure and having a current target (as
6484 well as a stack of targets below it, for memory references). Whenever
6485 something needs to be done that depends on which remote interface we are
6486 using, a flag in the current target_ops structure is tested (e.g.,
6487 @code{target_has_stack}), or a function is called through a pointer in the
6488 current target_ops structure. In this way, when a new remote interface
6489 is added, only one module needs to be touched---the one that actually
6490 implements the new remote interface. Other examples of
6491 attribute-structs are BFD access to multiple kinds of object file
6492 formats, or @value{GDBN}'s access to multiple source languages.
6494 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
6495 the code interfacing between @code{ptrace} and the rest of
6496 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
6497 something was very painful. In @value{GDBN} 4.x, these have all been
6498 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
6499 with variations between systems the same way any system-independent
6500 file would (hooks, @code{#if defined}, etc.), and machines which are
6501 radically different don't need to use @file{infptrace.c} at all.
6503 All debugging code must be controllable using the @samp{set debug
6504 @var{module}} command. Do not use @code{printf} to print trace
6505 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
6506 @code{#ifdef DEBUG}.
6510 @chapter Porting @value{GDBN}
6511 @cindex porting to new machines
6513 Most of the work in making @value{GDBN} compile on a new machine is in
6514 specifying the configuration of the machine. Porting a new
6515 architecture to @value{GDBN} can be broken into a number of steps.
6520 Ensure a @sc{bfd} exists for executables of the target architecture in
6521 the @file{bfd} directory. If one does not exist, create one by
6522 modifying an existing similar one.
6525 Implement a disassembler for the target architecture in the @file{opcodes}
6529 Define the target architecture in the @file{gdb} directory
6530 (@pxref{Adding a New Target, , Adding a New Target}). Add the pattern
6531 for the new target to @file{configure.tgt} with the names of the files
6532 that contain the code. By convention the target architecture
6533 definition for an architecture @var{arch} is placed in
6534 @file{@var{arch}-tdep.c}.
6536 Within @file{@var{arch}-tdep.c} define the function
6537 @code{_initialize_@var{arch}_tdep} which calls
6538 @code{gdbarch_register} to create the new @code{@w{struct
6539 gdbarch}} for the architecture.
6542 If a new remote target is needed, consider adding a new remote target
6543 by defining a function
6544 @code{_initialize_remote_@var{arch}}. However if at all possible
6545 use the @value{GDBN} @emph{Remote Serial Protocol} for this and implement
6546 the server side protocol independently with the target.
6549 If desired implement a simulator in the @file{sim} directory. This
6550 should create the library @file{libsim.a} implementing the interface
6551 in @file{remote-sim.h} (found in the @file{include} directory).
6554 Build and test. If desired, lobby the @sc{gdb} steering group to
6555 have the new port included in the main distribution!
6558 Add a description of the new architecture to the main @value{GDBN} user
6559 guide (@pxref{Configuration Specific Information, , Configuration
6560 Specific Information, gdb, Debugging with @value{GDBN}}).
6564 @node Versions and Branches
6565 @chapter Versions and Branches
6569 @value{GDBN}'s version is determined by the file
6570 @file{gdb/version.in} and takes one of the following forms:
6573 @item @var{major}.@var{minor}
6574 @itemx @var{major}.@var{minor}.@var{patchlevel}
6575 an official release (e.g., 6.2 or 6.2.1)
6576 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}
6577 a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g.,
6578 6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308)
6579 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs
6580 a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g.,
6581 6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
6582 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor})
6583 a vendor specific release of @value{GDBN}, that while based on@*
6584 @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD},
6585 may include additional changes
6588 @value{GDBN}'s mainline uses the @var{major} and @var{minor} version
6589 numbers from the most recent release branch, with a @var{patchlevel}
6590 of 50. At the time each new release branch is created, the mainline's
6591 @var{major} and @var{minor} version numbers are updated.
6593 @value{GDBN}'s release branch is similar. When the branch is cut, the
6594 @var{patchlevel} is changed from 50 to 90. As draft releases are
6595 drawn from the branch, the @var{patchlevel} is incremented. Once the
6596 first release (@var{major}.@var{minor}) has been made, the
6597 @var{patchlevel} is set to 0 and updates have an incremented
6600 For snapshots, and @sc{cvs} check outs, it is also possible to
6601 identify the @sc{cvs} origin:
6604 @item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD}
6605 drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302)
6606 @item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD}
6607 @itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{}
6608 drawn from a release branch prior to the release (e.g.,
6610 @item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD}
6611 @itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{}
6612 drawn from a release branch after the release (e.g., 6.2.0.20020308)
6615 If the previous @value{GDBN} version is 6.1 and the current version is
6616 6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor},
6617 here's an illustration of a typical sequence:
6624 +--------------------------.
6627 6.2.50.20020303-cvs 6.1.90 (draft #1)
6629 6.2.50.20020304-cvs 6.1.90.20020304-cvs
6631 6.2.50.20020305-cvs 6.1.91 (draft #2)
6633 6.2.50.20020306-cvs 6.1.91.20020306-cvs
6635 6.2.50.20020307-cvs 6.2 (release)
6637 6.2.50.20020308-cvs 6.2.0.20020308-cvs
6639 6.2.50.20020309-cvs 6.2.1 (update)
6641 6.2.50.20020310-cvs <branch closed>
6645 +--------------------------.
6648 6.3.50.20020312-cvs 6.2.90 (draft #1)
6652 @section Release Branches
6653 @cindex Release Branches
6655 @value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a
6656 single release branch, and identifies that branch using the @sc{cvs}
6660 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint
6661 gdb_@var{major}_@var{minor}-branch
6662 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release
6665 @emph{Pragmatics: To help identify the date at which a branch or
6666 release is made, both the branchpoint and release tags include the
6667 date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The
6668 branch tag, denoting the head of the branch, does not need this.}
6670 @section Vendor Branches
6671 @cindex vendor branches
6673 To avoid version conflicts, vendors are expected to modify the file
6674 @file{gdb/version.in} to include a vendor unique alphabetic identifier
6675 (an official @value{GDBN} release never uses alphabetic characters in
6676 its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit
6679 @section Experimental Branches
6680 @cindex experimental branches
6682 @subsection Guidelines
6684 @value{GDBN} permits the creation of branches, cut from the @sc{cvs}
6685 repository, for experimental development. Branches make it possible
6686 for developers to share preliminary work, and maintainers to examine
6687 significant new developments.
6689 The following are a set of guidelines for creating such branches:
6693 @item a branch has an owner
6694 The owner can set further policy for a branch, but may not change the
6695 ground rules. In particular, they can set a policy for commits (be it
6696 adding more reviewers or deciding who can commit).
6698 @item all commits are posted
6699 All changes committed to a branch shall also be posted to
6700 @email{gdb-patches@@sourceware.org, the @value{GDBN} patches
6701 mailing list}. While commentary on such changes are encouraged, people
6702 should remember that the changes only apply to a branch.
6704 @item all commits are covered by an assignment
6705 This ensures that all changes belong to the Free Software Foundation,
6706 and avoids the possibility that the branch may become contaminated.
6708 @item a branch is focused
6709 A focused branch has a single objective or goal, and does not contain
6710 unnecessary or irrelevant changes. Cleanups, where identified, being
6711 be pushed into the mainline as soon as possible.
6713 @item a branch tracks mainline
6714 This keeps the level of divergence under control. It also keeps the
6715 pressure on developers to push cleanups and other stuff into the
6718 @item a branch shall contain the entire @value{GDBN} module
6719 The @value{GDBN} module @code{gdb} should be specified when creating a
6720 branch (branches of individual files should be avoided). @xref{Tags}.
6722 @item a branch shall be branded using @file{version.in}
6723 The file @file{gdb/version.in} shall be modified so that it identifies
6724 the branch @var{owner} and branch @var{name}, e.g.,
6725 @samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}.
6732 To simplify the identification of @value{GDBN} branches, the following
6733 branch tagging convention is strongly recommended:
6737 @item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6738 @itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch
6739 The branch point and corresponding branch tag. @var{YYYYMMDD} is the
6740 date that the branch was created. A branch is created using the
6741 sequence: @anchor{experimental branch tags}
6743 cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb
6744 cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \
6745 @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb
6748 @item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6749 The tagged point, on the mainline, that was used when merging the branch
6750 on @var{yyyymmdd}. To merge in all changes since the branch was cut,
6751 use a command sequence like:
6753 cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb
6755 -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6756 -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6759 Similar sequences can be used to just merge in changes since the last
6765 For further information on @sc{cvs}, see
6766 @uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}.
6768 @node Start of New Year Procedure
6769 @chapter Start of New Year Procedure
6770 @cindex new year procedure
6772 At the start of each new year, the following actions should be performed:
6776 Rotate the ChangeLog file
6778 The current @file{ChangeLog} file should be renamed into
6779 @file{ChangeLog-YYYY} where YYYY is the year that has just passed.
6780 A new @file{ChangeLog} file should be created, and its contents should
6781 contain a reference to the previous ChangeLog. The following should
6782 also be preserved at the end of the new ChangeLog, in order to provide
6783 the appropriate settings when editing this file with Emacs:
6789 version-control: never
6795 Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY})
6796 in @file{gdb/config/djgpp/fnchange.lst}.
6799 Update the copyright year in the startup message
6801 Update the copyright year in:
6804 file @file{top.c}, function @code{print_gdb_version}
6806 file @file{gdbserver/server.c}, function @code{gdbserver_version}
6808 file @file{gdbserver/gdbreplay.c}, function @code{gdbreplay_version}
6812 Run the @file{copyright.py} Python script to add the new year in the copyright
6813 notices of most source files. This script has been tested with Python
6820 @chapter Releasing @value{GDBN}
6821 @cindex making a new release of gdb
6823 @section Branch Commit Policy
6825 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
6826 5.1 and 5.2 all used the below:
6830 The @file{gdb/MAINTAINERS} file still holds.
6832 Don't fix something on the branch unless/until it is also fixed in the
6833 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
6834 file is better than committing a hack.
6836 When considering a patch for the branch, suggested criteria include:
6837 Does it fix a build? Does it fix the sequence @kbd{break main; run}
6838 when debugging a static binary?
6840 The further a change is from the core of @value{GDBN}, the less likely
6841 the change will worry anyone (e.g., target specific code).
6843 Only post a proposal to change the core of @value{GDBN} after you've
6844 sent individual bribes to all the people listed in the
6845 @file{MAINTAINERS} file @t{;-)}
6848 @emph{Pragmatics: Provided updates are restricted to non-core
6849 functionality there is little chance that a broken change will be fatal.
6850 This means that changes such as adding a new architectures or (within
6851 reason) support for a new host are considered acceptable.}
6854 @section Obsoleting code
6856 Before anything else, poke the other developers (and around the source
6857 code) to see if there is anything that can be removed from @value{GDBN}
6858 (an old target, an unused file).
6860 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
6861 line. Doing this means that it is easy to identify something that has
6862 been obsoleted when greping through the sources.
6864 The process is done in stages --- this is mainly to ensure that the
6865 wider @value{GDBN} community has a reasonable opportunity to respond.
6866 Remember, everything on the Internet takes a week.
6870 Post the proposal on @email{gdb@@sourceware.org, the GDB mailing
6871 list} Creating a bug report to track the task's state, is also highly
6876 Post the proposal on @email{gdb-announce@@sourceware.org, the GDB
6877 Announcement mailing list}.
6881 Go through and edit all relevant files and lines so that they are
6882 prefixed with the word @code{OBSOLETE}.
6884 Wait until the next GDB version, containing this obsolete code, has been
6887 Remove the obsolete code.
6891 @emph{Maintainer note: While removing old code is regrettable it is
6892 hopefully better for @value{GDBN}'s long term development. Firstly it
6893 helps the developers by removing code that is either no longer relevant
6894 or simply wrong. Secondly since it removes any history associated with
6895 the file (effectively clearing the slate) the developer has a much freer
6896 hand when it comes to fixing broken files.}
6900 @section Before the Branch
6902 The most important objective at this stage is to find and fix simple
6903 changes that become a pain to track once the branch is created. For
6904 instance, configuration problems that stop @value{GDBN} from even
6905 building. If you can't get the problem fixed, document it in the
6906 @file{gdb/PROBLEMS} file.
6908 @subheading Prompt for @file{gdb/NEWS}
6910 People always forget. Send a post reminding them but also if you know
6911 something interesting happened add it yourself. The @code{schedule}
6912 script will mention this in its e-mail.
6914 @subheading Review @file{gdb/README}
6916 Grab one of the nightly snapshots and then walk through the
6917 @file{gdb/README} looking for anything that can be improved. The
6918 @code{schedule} script will mention this in its e-mail.
6920 @subheading Refresh any imported files.
6922 A number of files are taken from external repositories. They include:
6926 @file{texinfo/texinfo.tex}
6928 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
6931 @file{etc/standards.texi}, @file{etc/make-stds.texi}
6934 @subheading Check the ARI
6936 @uref{http://sourceware.org/gdb/ari,,A.R.I.} is an @code{awk} script
6937 (Awk Regression Index ;-) that checks for a number of errors and coding
6938 conventions. The checks include things like using @code{malloc} instead
6939 of @code{xmalloc} and file naming problems. There shouldn't be any
6942 @subsection Review the bug data base
6944 Close anything obviously fixed.
6946 @subsection Check all cross targets build
6948 The targets are listed in @file{gdb/MAINTAINERS}.
6951 @section Cut the Branch
6953 @subheading Create the branch
6958 $ V=`echo $v | sed 's/\./_/g'`
6959 $ D=`date -u +%Y-%m-%d`
6962 $ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6963 -D $D-gmt gdb_$V-$D-branchpoint insight
6964 cvs -f -d :ext:sourceware.org:/cvs/src rtag
6965 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight
6968 $ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6969 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
6970 cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6971 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
6979 By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact
6982 The trunk is first tagged so that the branch point can easily be found.
6984 Insight, which includes @value{GDBN}, is tagged at the same time.
6986 @file{version.in} gets bumped to avoid version number conflicts.
6988 The reading of @file{.cvsrc} is disabled using @file{-f}.
6991 @subheading Update @file{version.in}
6996 $ V=`echo $v | sed 's/\./_/g'`
7000 $ echo cvs -f -d :ext:sourceware.org:/cvs/src co \
7001 -r gdb_$V-branch src/gdb/version.in
7002 cvs -f -d :ext:sourceware.org:/cvs/src co
7003 -r gdb_5_2-branch src/gdb/version.in
7005 U src/gdb/version.in
7007 $ echo $u.90-0000-00-00-cvs > version.in
7009 5.1.90-0000-00-00-cvs
7010 $ cvs -f commit version.in
7015 @file{0000-00-00} is used as a date to pump prime the version.in update
7018 @file{.90} and the previous branch version are used as fairly arbitrary
7019 initial branch version number.
7023 @subheading Update the web and news pages
7027 @subheading Tweak cron to track the new branch
7029 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
7030 This file needs to be updated so that:
7034 A daily timestamp is added to the file @file{version.in}.
7036 The new branch is included in the snapshot process.
7040 See the file @file{gdbadmin/cron/README} for how to install the updated
7043 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
7044 any changes. That file is copied to both the branch/ and current/
7045 snapshot directories.
7048 @subheading Update the NEWS and README files
7050 The @file{NEWS} file needs to be updated so that on the branch it refers
7051 to @emph{changes in the current release} while on the trunk it also
7052 refers to @emph{changes since the current release}.
7054 The @file{README} file needs to be updated so that it refers to the
7057 @subheading Post the branch info
7059 Send an announcement to the mailing lists:
7063 @email{gdb-announce@@sourceware.org, GDB Announcement mailing list}
7065 @email{gdb@@sourceware.org, GDB Discussion mailing list} and
7066 @email{gdb-testers@@sourceware.org, GDB Testers mailing list}
7069 @emph{Pragmatics: The branch creation is sent to the announce list to
7070 ensure that people people not subscribed to the higher volume discussion
7073 The announcement should include:
7079 How to check out the branch using CVS.
7081 The date/number of weeks until the release.
7083 The branch commit policy still holds.
7086 @section Stabilize the branch
7088 Something goes here.
7090 @section Create a Release
7092 The process of creating and then making available a release is broken
7093 down into a number of stages. The first part addresses the technical
7094 process of creating a releasable tar ball. The later stages address the
7095 process of releasing that tar ball.
7097 When making a release candidate just the first section is needed.
7099 @subsection Create a release candidate
7101 The objective at this stage is to create a set of tar balls that can be
7102 made available as a formal release (or as a less formal release
7105 @subsubheading Freeze the branch
7107 Send out an e-mail notifying everyone that the branch is frozen to
7108 @email{gdb-patches@@sourceware.org}.
7110 @subsubheading Establish a few defaults.
7115 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
7117 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
7121 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
7123 /home/gdbadmin/bin/autoconf
7132 Check the @code{autoconf} version carefully. You want to be using the
7133 version documented in the toplevel @file{README-maintainer-mode} file.
7134 It is very unlikely that the version of @code{autoconf} installed in
7135 system directories (e.g., @file{/usr/bin/autoconf}) is correct.
7138 @subsubheading Check out the relevant modules:
7141 $ for m in gdb insight
7143 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
7153 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
7154 any confusion between what is written here and what your local
7155 @code{cvs} really does.
7158 @subsubheading Update relevant files.
7164 Major releases get their comments added as part of the mainline. Minor
7165 releases should probably mention any significant bugs that were fixed.
7167 Don't forget to include the @file{ChangeLog} entry.
7170 $ emacs gdb/src/gdb/NEWS
7175 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
7176 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7181 You'll need to update:
7193 $ emacs gdb/src/gdb/README
7198 $ cp gdb/src/gdb/README insight/src/gdb/README
7199 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7202 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
7203 before the initial branch was cut so just a simple substitute is needed
7206 @emph{Maintainer note: Other projects generate @file{README} and
7207 @file{INSTALL} from the core documentation. This might be worth
7210 @item gdb/version.in
7213 $ echo $v > gdb/src/gdb/version.in
7214 $ cat gdb/src/gdb/version.in
7216 $ emacs gdb/src/gdb/version.in
7219 ... Bump to version ...
7221 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
7222 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7227 @subsubheading Do the dirty work
7229 This is identical to the process used to create the daily snapshot.
7232 $ for m in gdb insight
7234 ( cd $m/src && gmake -f src-release $m.tar )
7238 If the top level source directory does not have @file{src-release}
7239 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
7242 $ for m in gdb insight
7244 ( cd $m/src && gmake -f Makefile.in $m.tar )
7248 @subsubheading Check the source files
7250 You're looking for files that have mysteriously disappeared.
7251 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
7252 for the @file{version.in} update @kbd{cronjob}.
7255 $ ( cd gdb/src && cvs -f -q -n update )
7259 @dots{} lots of generated files @dots{}
7264 @dots{} lots of generated files @dots{}
7269 @emph{Don't worry about the @file{gdb.info-??} or
7270 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
7271 was also generated only something strange with CVS means that they
7272 didn't get suppressed). Fixing it would be nice though.}
7274 @subsubheading Create compressed versions of the release
7280 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
7281 $ for m in gdb insight
7283 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
7284 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
7294 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
7295 in that mode, @code{gzip} does not know the name of the file and, hence,
7296 can not include it in the compressed file. This is also why the release
7297 process runs @code{tar} and @code{bzip2} as separate passes.
7300 @subsection Sanity check the tar ball
7302 Pick a popular machine (Solaris/PPC?) and try the build on that.
7305 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
7310 $ ./gdb/gdb ./gdb/gdb
7314 Breakpoint 1 at 0x80732bc: file main.c, line 734.
7316 Starting program: /tmp/gdb-5.2/gdb/gdb
7318 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
7319 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
7321 $1 = @{argc = 136426532, argv = 0x821b7f0@}
7325 @subsection Make a release candidate available
7327 If this is a release candidate then the only remaining steps are:
7331 Commit @file{version.in} and @file{ChangeLog}
7333 Tweak @file{version.in} (and @file{ChangeLog} to read
7334 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
7335 process can restart.
7337 Make the release candidate available in
7338 @uref{ftp://sourceware.org/pub/gdb/snapshots/branch}
7340 Notify the relevant mailing lists ( @email{gdb@@sourceware.org} and
7341 @email{gdb-testers@@sourceware.org} that the candidate is available.
7344 @subsection Make a formal release available
7346 (And you thought all that was required was to post an e-mail.)
7348 @subsubheading Install on sware
7350 Copy the new files to both the release and the old release directory:
7353 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
7354 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
7358 Clean up the releases directory so that only the most recent releases
7359 are available (e.g.@: keep 5.2 and 5.2.1 but remove 5.1):
7362 $ cd ~ftp/pub/gdb/releases
7367 Update the file @file{README} and @file{.message} in the releases
7374 $ ln README .message
7377 @subsubheading Update the web pages.
7381 @item htdocs/download/ANNOUNCEMENT
7382 This file, which is posted as the official announcement, includes:
7385 General announcement.
7387 News. If making an @var{M}.@var{N}.1 release, retain the news from
7388 earlier @var{M}.@var{N} release.
7393 @item htdocs/index.html
7394 @itemx htdocs/news/index.html
7395 @itemx htdocs/download/index.html
7396 These files include:
7399 Announcement of the most recent release.
7401 News entry (remember to update both the top level and the news directory).
7403 These pages also need to be regenerate using @code{index.sh}.
7405 @item download/onlinedocs/
7406 You need to find the magic command that is used to generate the online
7407 docs from the @file{.tar.bz2}. The best way is to look in the output
7408 from one of the nightly @code{cron} jobs and then just edit accordingly.
7412 $ ~/ss/update-web-docs \
7413 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
7415 /www/sourceware/htdocs/gdb/download/onlinedocs \
7420 Just like the online documentation. Something like:
7423 $ /bin/sh ~/ss/update-web-ari \
7424 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
7426 /www/sourceware/htdocs/gdb/download/ari \
7432 @subsubheading Shadow the pages onto gnu
7434 Something goes here.
7437 @subsubheading Install the @value{GDBN} tar ball on GNU
7439 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
7440 @file{~ftp/gnu/gdb}.
7442 @subsubheading Make the @file{ANNOUNCEMENT}
7444 Post the @file{ANNOUNCEMENT} file you created above to:
7448 @email{gdb-announce@@sourceware.org, GDB Announcement mailing list}
7450 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
7451 day or so to let things get out)
7453 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
7458 The release is out but you're still not finished.
7460 @subsubheading Commit outstanding changes
7462 In particular you'll need to commit any changes to:
7466 @file{gdb/ChangeLog}
7468 @file{gdb/version.in}
7475 @subsubheading Tag the release
7480 $ d=`date -u +%Y-%m-%d`
7483 $ ( cd insight/src/gdb && cvs -f -q update )
7484 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
7487 Insight is used since that contains more of the release than
7490 @subsubheading Mention the release on the trunk
7492 Just put something in the @file{ChangeLog} so that the trunk also
7493 indicates when the release was made.
7495 @subsubheading Restart @file{gdb/version.in}
7497 If @file{gdb/version.in} does not contain an ISO date such as
7498 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
7499 committed all the release changes it can be set to
7500 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
7501 is important - it affects the snapshot process).
7503 Don't forget the @file{ChangeLog}.
7505 @subsubheading Merge into trunk
7507 The files committed to the branch may also need changes merged into the
7510 @subsubheading Revise the release schedule
7512 Post a revised release schedule to @email{gdb@@sourceware.org, GDB
7513 Discussion List} with an updated announcement. The schedule can be
7514 generated by running:
7517 $ ~/ss/schedule `date +%s` schedule
7521 The first parameter is approximate date/time in seconds (from the epoch)
7522 of the most recent release.
7524 Also update the schedule @code{cronjob}.
7526 @section Post release
7528 Remove any @code{OBSOLETE} code.
7535 The testsuite is an important component of the @value{GDBN} package.
7536 While it is always worthwhile to encourage user testing, in practice
7537 this is rarely sufficient; users typically use only a small subset of
7538 the available commands, and it has proven all too common for a change
7539 to cause a significant regression that went unnoticed for some time.
7541 The @value{GDBN} testsuite uses the DejaGNU testing framework. The
7542 tests themselves are calls to various @code{Tcl} procs; the framework
7543 runs all the procs and summarizes the passes and fails.
7545 @section Using the Testsuite
7547 @cindex running the test suite
7548 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
7549 testsuite's objdir) and type @code{make check}. This just sets up some
7550 environment variables and invokes DejaGNU's @code{runtest} script. While
7551 the testsuite is running, you'll get mentions of which test file is in use,
7552 and a mention of any unexpected passes or fails. When the testsuite is
7553 finished, you'll get a summary that looks like this:
7558 # of expected passes 6016
7559 # of unexpected failures 58
7560 # of unexpected successes 5
7561 # of expected failures 183
7562 # of unresolved testcases 3
7563 # of untested testcases 5
7566 To run a specific test script, type:
7568 make check RUNTESTFLAGS='@var{tests}'
7570 where @var{tests} is a list of test script file names, separated by
7573 If you use GNU make, you can use its @option{-j} option to run the
7574 testsuite in parallel. This can greatly reduce the amount of time it
7575 takes for the testsuite to run. In this case, if you set
7576 @code{RUNTESTFLAGS} then, by default, the tests will be run serially
7577 even under @option{-j}. You can override this and force a parallel run
7578 by setting the @code{make} variable @code{FORCE_PARALLEL} to any
7579 non-empty value. Note that the parallel @kbd{make check} assumes
7580 that you want to run the entire testsuite, so it is not compatible
7581 with some dejagnu options, like @option{--directory}.
7583 The ideal test run consists of expected passes only; however, reality
7584 conspires to keep us from this ideal. Unexpected failures indicate
7585 real problems, whether in @value{GDBN} or in the testsuite. Expected
7586 failures are still failures, but ones which have been decided are too
7587 hard to deal with at the time; for instance, a test case might work
7588 everywhere except on AIX, and there is no prospect of the AIX case
7589 being fixed in the near future. Expected failures should not be added
7590 lightly, since you may be masking serious bugs in @value{GDBN}.
7591 Unexpected successes are expected fails that are passing for some
7592 reason, while unresolved and untested cases often indicate some minor
7593 catastrophe, such as the compiler being unable to deal with a test
7596 When making any significant change to @value{GDBN}, you should run the
7597 testsuite before and after the change, to confirm that there are no
7598 regressions. Note that truly complete testing would require that you
7599 run the testsuite with all supported configurations and a variety of
7600 compilers; however this is more than really necessary. In many cases
7601 testing with a single configuration is sufficient. Other useful
7602 options are to test one big-endian (Sparc) and one little-endian (x86)
7603 host, a cross config with a builtin simulator (powerpc-eabi,
7604 mips-elf), or a 64-bit host (Alpha).
7606 If you add new functionality to @value{GDBN}, please consider adding
7607 tests for it as well; this way future @value{GDBN} hackers can detect
7608 and fix their changes that break the functionality you added.
7609 Similarly, if you fix a bug that was not previously reported as a test
7610 failure, please add a test case for it. Some cases are extremely
7611 difficult to test, such as code that handles host OS failures or bugs
7612 in particular versions of compilers, and it's OK not to try to write
7613 tests for all of those.
7615 DejaGNU supports separate build, host, and target machines. However,
7616 some @value{GDBN} test scripts do not work if the build machine and
7617 the host machine are not the same. In such an environment, these scripts
7618 will give a result of ``UNRESOLVED'', like this:
7621 UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
7624 @section Testsuite Parameters
7626 Several variables exist to modify the behavior of the testsuite.
7630 @item @code{TRANSCRIPT}
7632 Sometimes it is convenient to get a transcript of the commands which
7633 the testsuite sends to @value{GDBN}. For example, if @value{GDBN}
7634 crashes during testing, a transcript can be used to more easily
7635 reconstruct the failure when running @value{GDBN} under @value{GDBN}.
7637 You can instruct the @value{GDBN} testsuite to write transcripts by
7638 setting the DejaGNU variable @code{TRANSCRIPT} (to any value)
7639 before invoking @code{runtest} or @kbd{make check}. The transcripts
7640 will be written into DejaGNU's output directory. One transcript will
7641 be made for each invocation of @value{GDBN}; they will be named
7642 @file{transcript.@var{n}}, where @var{n} is an integer. The first
7643 line of the transcript file will show how @value{GDBN} was invoked;
7644 each subsequent line is a command sent as input to @value{GDBN}.
7647 make check RUNTESTFLAGS=TRANSCRIPT=y
7650 Note that the transcript is not always complete. In particular, tests
7651 of completion can yield partial command lines.
7655 Sometimes one wishes to test a different @value{GDBN} than the one in the build
7656 directory. For example, one may wish to run the testsuite on
7657 @file{/usr/bin/gdb}.
7660 make check RUNTESTFLAGS=GDB=/usr/bin/gdb
7663 @item @code{GDBSERVER}
7665 When testing a different @value{GDBN}, it is often useful to also test a
7666 different gdbserver.
7669 make check RUNTESTFLAGS="GDB=/usr/bin/gdb GDBSERVER=/usr/bin/gdbserver"
7672 @item @code{INTERNAL_GDBFLAGS}
7674 When running the testsuite normally one doesn't want whatever is in
7675 @file{~/.gdbinit} to interfere with the tests, therefore the test harness
7676 passes @option{-nx} to @value{GDBN}. One also doesn't want any windowed
7677 version of @value{GDBN}, e.g., @samp{gdb -tui}, to run.
7678 This is achieved via @code{INTERNAL_GDBFLAGS}.
7681 set INTERNAL_GDBFLAGS "-nw -nx"
7684 This is all well and good, except when testing an installed @value{GDBN}
7685 that has been configured with @option{--with-system-gdbinit}. Here one
7686 does not want @file{~/.gdbinit} loaded but one may want the system
7687 @file{.gdbinit} file loaded. This can be achieved by pointing @code{$HOME}
7688 at a directory without a @file{.gdbinit} and by overriding
7689 @code{INTERNAL_GDBFLAGS} and removing @option{-nx}.
7693 HOME=`pwd` runtest \
7695 GDBSERVER=/usr/bin/gdbserver \
7696 INTERNAL_GDBFLAGS=-nw
7701 There are two ways to run the testsuite and pass additional parameters
7702 to DejaGnu. The first is with @kbd{make check} and specifying the
7703 makefile variable @samp{RUNTESTFLAGS}.
7706 make check RUNTESTFLAGS=TRANSCRIPT=y
7709 The second is to cd to the @file{testsuite} directory and invoke the DejaGnu
7710 @command{runtest} command directly.
7715 runtest TRANSCRIPT=y
7718 @section Testsuite Configuration
7719 @cindex Testsuite Configuration
7721 It is possible to adjust the behavior of the testsuite by defining
7722 the global variables listed below, either in a @file{site.exp} file,
7727 @item @code{gdb_test_timeout}
7729 Defining this variable changes the default timeout duration used during
7730 communication with @value{GDBN}. More specifically, the global variable
7731 used during testing is @code{timeout}, but this variable gets reset to
7732 @code{gdb_test_timeout} at the beginning of each testcase, making sure
7733 that any local change to @code{timeout} in a testcase does not affect
7734 subsequent testcases.
7736 This global variable comes in handy when the debugger is slower than
7737 normal due to the testing environment, triggering unexpected @code{TIMEOUT}
7738 test failures. Examples include when testing on a remote machine, or
7739 against a system where communications are slow.
7741 If not specifically defined, this variable gets automatically defined
7742 to the same value as @code{timeout} during the testsuite initialization.
7743 The default value of the timeout is defined in the file
7744 @file{gdb/testsuite/config/unix.exp} that is part of the @value{GDBN}
7745 test suite@footnote{If you are using a board file, it could override
7746 the test-suite default; search the board file for "timeout".}.
7750 @section Testsuite Organization
7752 @cindex test suite organization
7753 The testsuite is entirely contained in @file{gdb/testsuite}. While the
7754 testsuite includes some makefiles and configury, these are very minimal,
7755 and used for little besides cleaning up, since the tests themselves
7756 handle the compilation of the programs that @value{GDBN} will run. The file
7757 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
7758 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
7759 configuration-specific files, typically used for special-purpose
7760 definitions of procs like @code{gdb_load} and @code{gdb_start}.
7762 The tests themselves are to be found in @file{testsuite/gdb.*} and
7763 subdirectories of those. The names of the test files must always end
7764 with @file{.exp}. DejaGNU collects the test files by wildcarding
7765 in the test directories, so both subdirectories and individual files
7766 get chosen and run in alphabetical order.
7768 The following table lists the main types of subdirectories and what they
7769 are for. Since DejaGNU finds test files no matter where they are
7770 located, and since each test file sets up its own compilation and
7771 execution environment, this organization is simply for convenience and
7776 This is the base testsuite. The tests in it should apply to all
7777 configurations of @value{GDBN} (but generic native-only tests may live here).
7778 The test programs should be in the subset of C that is valid K&R,
7779 ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance
7782 @item gdb.@var{lang}
7783 Language-specific tests for any language @var{lang} besides C. Examples are
7784 @file{gdb.cp} and @file{gdb.java}.
7786 @item gdb.@var{platform}
7787 Non-portable tests. The tests are specific to a specific configuration
7788 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
7791 @item gdb.@var{compiler}
7792 Tests specific to a particular compiler. As of this writing (June
7793 1999), there aren't currently any groups of tests in this category that
7794 couldn't just as sensibly be made platform-specific, but one could
7795 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
7798 @item gdb.@var{subsystem}
7799 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
7800 instance, @file{gdb.disasm} exercises various disassemblers, while
7801 @file{gdb.stabs} tests pathways through the stabs symbol reader.
7804 @section Writing Tests
7805 @cindex writing tests
7807 In many areas, the @value{GDBN} tests are already quite comprehensive; you
7808 should be able to copy existing tests to handle new cases.
7810 You should try to use @code{gdb_test} whenever possible, since it
7811 includes cases to handle all the unexpected errors that might happen.
7812 However, it doesn't cost anything to add new test procedures; for
7813 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
7814 calls @code{gdb_test} multiple times.
7816 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
7817 necessary. Even if @value{GDBN} has several valid responses to
7818 a command, you can use @code{gdb_test_multiple}. Like @code{gdb_test},
7819 @code{gdb_test_multiple} recognizes internal errors and unexpected
7822 Do not write tests which expect a literal tab character from @value{GDBN}.
7823 On some operating systems (e.g.@: OpenBSD) the TTY layer expands tabs to
7824 spaces, so by the time @value{GDBN}'s output reaches expect the tab is gone.
7826 The source language programs do @emph{not} need to be in a consistent
7827 style. Since @value{GDBN} is used to debug programs written in many different
7828 styles, it's worth having a mix of styles in the testsuite; for
7829 instance, some @value{GDBN} bugs involving the display of source lines would
7830 never manifest themselves if the programs used GNU coding style
7833 Some testcase results need more detailed explanation:
7837 Known problem of @value{GDBN} itself. You must specify the @value{GDBN} bug
7838 report number like in these sample tests:
7840 kfail "gdb/13392" "continue to marker 2"
7844 setup_kfail gdb/13392 "*-*-*"
7845 kfail "continue to marker 2"
7849 Known problem of environment. This typically includes @value{NGCC} but it
7850 includes also many other system components which cannot be fixed in the
7851 @value{GDBN} project. Sample test with sanity check not knowing the specific
7852 cause of the problem:
7854 # On x86_64 it is commonly about 4MB.
7855 if @{$stub_size > 25000000@} @{
7856 xfail "stub size $stub_size is too large"
7861 You should provide bug report number for the failing component of the
7862 environment, if such bug report is available:
7864 if @{[test_compiler_info @{gcc-[0-3]-*@}]
7865 || [test_compiler_info @{gcc-4-[0-5]-*@}]@} @{
7866 setup_xfail "gcc/46955" *-*-*
7868 gdb_test "python print ttype.template_argument(2)" "&C::c"
7872 @section Board settings
7873 In @value{GDBN} testsuite, the tests can be configured or customized in the board
7874 file by means of @dfn{Board Settings}. Each setting should be consulted by
7875 test cases that depend on the corresponding feature.
7877 Here are the supported board settings:
7881 @item gdb,cannot_call_functions
7882 The board does not support inferior call, that is, invoking inferior functions
7884 @item gdb,can_reverse
7885 The board supports reverse execution.
7886 @item gdb,no_hardware_watchpoints
7887 The board does not support hardware watchpoints.
7889 @value{GDBN} is unable to intercept target file operations in remote and perform
7891 @item gdb,noinferiorio
7892 The board is unable to provide I/O capability to the inferior.
7893 @c @item gdb,noresults
7896 The board does not support signals.
7897 @item gdb,skip_huge_test
7898 Skip time-consuming tests on the board with slow connection.
7899 @item gdb,skip_float_tests
7900 Skip tests related to float points on target board.
7901 @item gdb,use_precord
7902 The board supports process record.
7903 @item gdb_server_prog
7904 The location of GDBserver. If GDBserver somewhere other than its default
7905 location is used in test, specify the location of GDBserver in this variable.
7906 The location is a file name of GDBserver that can be either absolute or
7907 relative to testsuite subdirectory in build directory.
7909 The location of in-process agent. If in-process agent other than its default
7910 location is used in test, specify the location of in-process agent in
7911 this variable. The location is a file name of in-process agent that can be
7912 either absolute or relative to testsuite subdirectory in build directory.
7914 @value{GDBN} does not support argument passing for inferior.
7916 The board does not support type @code{long long}.
7920 The tests are running with gdb stub.
7927 Check the @file{README} file, it often has useful information that does not
7928 appear anywhere else in the directory.
7931 * Getting Started:: Getting started working on @value{GDBN}
7932 * Debugging GDB:: Debugging @value{GDBN} with itself
7935 @node Getting Started
7937 @section Getting Started
7939 @value{GDBN} is a large and complicated program, and if you first starting to
7940 work on it, it can be hard to know where to start. Fortunately, if you
7941 know how to go about it, there are ways to figure out what is going on.
7943 This manual, the @value{GDBN} Internals manual, has information which applies
7944 generally to many parts of @value{GDBN}.
7946 Information about particular functions or data structures are located in
7947 comments with those functions or data structures. If you run across a
7948 function or a global variable which does not have a comment correctly
7949 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
7950 free to submit a bug report, with a suggested comment if you can figure
7951 out what the comment should say. If you find a comment which is
7952 actually wrong, be especially sure to report that.
7954 Comments explaining the function of macros defined in host, target, or
7955 native dependent files can be in several places. Sometimes they are
7956 repeated every place the macro is defined. Sometimes they are where the
7957 macro is used. Sometimes there is a header file which supplies a
7958 default definition of the macro, and the comment is there. This manual
7959 also documents all the available macros.
7960 @c (@pxref{Host Conditionals}, @pxref{Target
7961 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
7964 Start with the header files. Once you have some idea of how
7965 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
7966 @file{gdbtypes.h}), you will find it much easier to understand the
7967 code which uses and creates those symbol tables.
7969 You may wish to process the information you are getting somehow, to
7970 enhance your understanding of it. Summarize it, translate it to another
7971 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
7972 the code to predict what a test case would do and write the test case
7973 and verify your prediction, etc. If you are reading code and your eyes
7974 are starting to glaze over, this is a sign you need to use a more active
7977 Once you have a part of @value{GDBN} to start with, you can find more
7978 specifically the part you are looking for by stepping through each
7979 function with the @code{next} command. Do not use @code{step} or you
7980 will quickly get distracted; when the function you are stepping through
7981 calls another function try only to get a big-picture understanding
7982 (perhaps using the comment at the beginning of the function being
7983 called) of what it does. This way you can identify which of the
7984 functions being called by the function you are stepping through is the
7985 one which you are interested in. You may need to examine the data
7986 structures generated at each stage, with reference to the comments in
7987 the header files explaining what the data structures are supposed to
7990 Of course, this same technique can be used if you are just reading the
7991 code, rather than actually stepping through it. The same general
7992 principle applies---when the code you are looking at calls something
7993 else, just try to understand generally what the code being called does,
7994 rather than worrying about all its details.
7996 @cindex command implementation
7997 A good place to start when tracking down some particular area is with
7998 a command which invokes that feature. Suppose you want to know how
7999 single-stepping works. As a @value{GDBN} user, you know that the
8000 @code{step} command invokes single-stepping. The command is invoked
8001 via command tables (see @file{command.h}); by convention the function
8002 which actually performs the command is formed by taking the name of
8003 the command and adding @samp{_command}, or in the case of an
8004 @code{info} subcommand, @samp{_info}. For example, the @code{step}
8005 command invokes the @code{step_command} function and the @code{info
8006 display} command invokes @code{display_info}. When this convention is
8007 not followed, you might have to use @code{grep} or @kbd{M-x
8008 tags-search} in emacs, or run @value{GDBN} on itself and set a
8009 breakpoint in @code{execute_command}.
8011 @cindex @code{bug-gdb} mailing list
8012 If all of the above fail, it may be appropriate to ask for information
8013 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
8014 wondering if anyone could give me some tips about understanding
8015 @value{GDBN}''---if we had some magic secret we would put it in this manual.
8016 Suggestions for improving the manual are always welcome, of course.
8020 @section Debugging @value{GDBN} with itself
8021 @cindex debugging @value{GDBN}
8023 If @value{GDBN} is limping on your machine, this is the preferred way to get it
8024 fully functional. Be warned that in some ancient Unix systems, like
8025 Ultrix 4.2, a program can't be running in one process while it is being
8026 debugged in another. Rather than typing the command @kbd{@w{./gdb
8027 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
8028 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
8030 When you run @value{GDBN} in the @value{GDBN} source directory, it will read
8031 @file{gdb-gdb.gdb} file (plus possibly @file{gdb-gdb.py} file) that sets up
8032 some simple things to make debugging gdb easier. The @code{info} command, when
8033 executed without a subcommand in a @value{GDBN} being debugged by gdb, will pop
8034 you back up to the top level gdb. See @file{gdb-gdb.gdb} for details.
8036 If you use emacs, you will probably want to do a @code{make TAGS} after
8037 you configure your distribution; this will put the machine dependent
8038 routines for your local machine where they will be accessed first by
8041 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
8042 have run @code{fixincludes} if you are compiling with gcc.
8044 @section Submitting Patches
8046 @cindex submitting patches
8047 Thanks for thinking of offering your changes back to the community of
8048 @value{GDBN} users. In general we like to get well designed enhancements.
8049 Thanks also for checking in advance about the best way to transfer the
8052 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
8053 This manual summarizes what we believe to be clean design for @value{GDBN}.
8055 If the maintainers don't have time to put the patch in when it arrives,
8056 or if there is any question about a patch, it goes into a large queue
8057 with everyone else's patches and bug reports.
8059 @cindex legal papers for code contributions
8060 The legal issue is that to incorporate substantial changes requires a
8061 copyright assignment from you and/or your employer, granting ownership
8062 of the changes to the Free Software Foundation. You can get the
8063 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
8064 and asking for it. We recommend that people write in "All programs
8065 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
8066 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
8068 contributed with only one piece of legalese pushed through the
8069 bureaucracy and filed with the FSF. We can't start merging changes until
8070 this paperwork is received by the FSF (their rules, which we follow
8071 since we maintain it for them).
8073 Technically, the easiest way to receive changes is to receive each
8074 feature as a small context diff or unidiff, suitable for @code{patch}.
8075 Each message sent to me should include the changes to C code and
8076 header files for a single feature, plus @file{ChangeLog} entries for
8077 each directory where files were modified, and diffs for any changes
8078 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
8079 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
8080 single feature, they can be split down into multiple messages.
8082 In this way, if we read and like the feature, we can add it to the
8083 sources with a single patch command, do some testing, and check it in.
8084 If you leave out the @file{ChangeLog}, we have to write one. If you leave
8085 out the doc, we have to puzzle out what needs documenting. Etc., etc.
8087 The reason to send each change in a separate message is that we will not
8088 install some of the changes. They'll be returned to you with questions
8089 or comments. If we're doing our job correctly, the message back to you
8090 will say what you have to fix in order to make the change acceptable.
8091 The reason to have separate messages for separate features is so that
8092 the acceptable changes can be installed while one or more changes are
8093 being reworked. If multiple features are sent in a single message, we
8094 tend to not put in the effort to sort out the acceptable changes from
8095 the unacceptable, so none of the features get installed until all are
8098 If this sounds painful or authoritarian, well, it is. But we get a lot
8099 of bug reports and a lot of patches, and many of them don't get
8100 installed because we don't have the time to finish the job that the bug
8101 reporter or the contributor could have done. Patches that arrive
8102 complete, working, and well designed, tend to get installed on the day
8103 they arrive. The others go into a queue and get installed as time
8104 permits, which, since the maintainers have many demands to meet, may not
8105 be for quite some time.
8107 Please send patches directly to
8108 @email{gdb-patches@@sourceware.org, the @value{GDBN} maintainers}.
8110 @section Build Script
8112 @cindex build script
8114 The script @file{gdb_buildall.sh} builds @value{GDBN} with flag
8115 @option{--enable-targets=all} set. This builds @value{GDBN} with all supported
8116 targets activated. This helps testing @value{GDBN} when doing changes that
8117 affect more than one architecture and is much faster than using
8118 @file{gdb_mbuild.sh}.
8120 After building @value{GDBN} the script checks which architectures are
8121 supported and then switches the current architecture to each of those to get
8122 information about the architecture. The test results are stored in log files
8123 in the directory the script was called from.
8125 @include observer.texi
8127 @node GNU Free Documentation License
8128 @appendix GNU Free Documentation License
8132 @unnumbered Concept Index
8136 @node Function and Variable Index
8137 @unnumbered Function and Variable Index