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 PRINTF_HAS_LONG_LONG
2765 Define this if the host can handle printing of long long integers via
2766 the printf format conversion specifier @code{ll}. This is set by the
2767 @code{configure} script.
2769 @item LSEEK_NOT_LINEAR
2770 Define this if @code{lseek (n)} does not necessarily move to byte number
2771 @code{n} in the file. This is only used when reading source files. It
2772 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2775 Define this to help placate @code{lint} in some situations.
2778 Define this to override the defaults of @code{__volatile__} or
2783 @node Target Architecture Definition
2785 @chapter Target Architecture Definition
2787 @cindex target architecture definition
2788 @value{GDBN}'s target architecture defines what sort of
2789 machine-language programs @value{GDBN} can work with, and how it works
2792 The target architecture object is implemented as the C structure
2793 @code{struct gdbarch *}. The structure, and its methods, are generated
2794 using the Bourne shell script @file{gdbarch.sh}.
2797 * OS ABI Variant Handling::
2798 * Initialize New Architecture::
2799 * Registers and Memory::
2800 * Pointers and Addresses::
2802 * Register Representation::
2803 * Frame Interpretation::
2804 * Inferior Call Setup::
2805 * Adding support for debugging core files::
2806 * Defining Other Architecture Features::
2807 * Adding a New Target::
2810 @node OS ABI Variant Handling
2811 @section Operating System ABI Variant Handling
2812 @cindex OS ABI variants
2814 @value{GDBN} provides a mechanism for handling variations in OS
2815 ABIs. An OS ABI variant may have influence over any number of
2816 variables in the target architecture definition. There are two major
2817 components in the OS ABI mechanism: sniffers and handlers.
2819 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2820 (the architecture may be wildcarded) in an attempt to determine the
2821 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2822 to be @dfn{generic}, while sniffers for a specific architecture are
2823 considered to be @dfn{specific}. A match from a specific sniffer
2824 overrides a match from a generic sniffer. Multiple sniffers for an
2825 architecture/flavour may exist, in order to differentiate between two
2826 different operating systems which use the same basic file format. The
2827 OS ABI framework provides a generic sniffer for ELF-format files which
2828 examines the @code{EI_OSABI} field of the ELF header, as well as note
2829 sections known to be used by several operating systems.
2831 @cindex fine-tuning @code{gdbarch} structure
2832 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2833 selected OS ABI. There may be only one handler for a given OS ABI
2834 for each BFD architecture.
2836 The following OS ABI variants are defined in @file{defs.h}:
2840 @findex GDB_OSABI_UNINITIALIZED
2841 @item GDB_OSABI_UNINITIALIZED
2842 Used for struct gdbarch_info if ABI is still uninitialized.
2844 @findex GDB_OSABI_UNKNOWN
2845 @item GDB_OSABI_UNKNOWN
2846 The ABI of the inferior is unknown. The default @code{gdbarch}
2847 settings for the architecture will be used.
2849 @findex GDB_OSABI_SVR4
2850 @item GDB_OSABI_SVR4
2851 UNIX System V Release 4.
2853 @findex GDB_OSABI_HURD
2854 @item GDB_OSABI_HURD
2855 GNU using the Hurd kernel.
2857 @findex GDB_OSABI_SOLARIS
2858 @item GDB_OSABI_SOLARIS
2861 @findex GDB_OSABI_OSF1
2862 @item GDB_OSABI_OSF1
2863 OSF/1, including Digital UNIX and Compaq Tru64 UNIX.
2865 @findex GDB_OSABI_LINUX
2866 @item GDB_OSABI_LINUX
2867 GNU using the Linux kernel.
2869 @findex GDB_OSABI_FREEBSD_AOUT
2870 @item GDB_OSABI_FREEBSD_AOUT
2871 FreeBSD using the @code{a.out} executable format.
2873 @findex GDB_OSABI_FREEBSD_ELF
2874 @item GDB_OSABI_FREEBSD_ELF
2875 FreeBSD using the ELF executable format.
2877 @findex GDB_OSABI_NETBSD_AOUT
2878 @item GDB_OSABI_NETBSD_AOUT
2879 NetBSD using the @code{a.out} executable format.
2881 @findex GDB_OSABI_NETBSD_ELF
2882 @item GDB_OSABI_NETBSD_ELF
2883 NetBSD using the ELF executable format.
2885 @findex GDB_OSABI_OPENBSD_ELF
2886 @item GDB_OSABI_OPENBSD_ELF
2887 OpenBSD using the ELF executable format.
2889 @findex GDB_OSABI_WINCE
2890 @item GDB_OSABI_WINCE
2893 @findex GDB_OSABI_GO32
2894 @item GDB_OSABI_GO32
2897 @findex GDB_OSABI_IRIX
2898 @item GDB_OSABI_IRIX
2901 @findex GDB_OSABI_INTERIX
2902 @item GDB_OSABI_INTERIX
2903 Interix (Posix layer for MS-Windows systems).
2905 @findex GDB_OSABI_HPUX_ELF
2906 @item GDB_OSABI_HPUX_ELF
2907 HP/UX using the ELF executable format.
2909 @findex GDB_OSABI_HPUX_SOM
2910 @item GDB_OSABI_HPUX_SOM
2911 HP/UX using the SOM executable format.
2913 @findex GDB_OSABI_QNXNTO
2914 @item GDB_OSABI_QNXNTO
2917 @findex GDB_OSABI_CYGWIN
2918 @item GDB_OSABI_CYGWIN
2921 @findex GDB_OSABI_AIX
2927 Here are the functions that make up the OS ABI framework:
2929 @deftypefun {const char *} gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2930 Return the name of the OS ABI corresponding to @var{osabi}.
2933 @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}))
2934 Register the OS ABI handler specified by @var{init_osabi} for the
2935 architecture, machine type and OS ABI specified by @var{arch},
2936 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2937 machine type, which implies the architecture's default machine type,
2941 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2942 Register the OS ABI file sniffer specified by @var{sniffer} for the
2943 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2944 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2945 be generic, and is allowed to examine @var{flavour}-flavoured files for
2949 @deftypefun {enum gdb_osabi} gdbarch_lookup_osabi (bfd *@var{abfd})
2950 Examine the file described by @var{abfd} to determine its OS ABI.
2951 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2955 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2956 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2957 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2958 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2959 architecture, a warning will be issued and the debugging session will continue
2960 with the defaults already established for @var{gdbarch}.
2963 @deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj})
2964 Helper routine for ELF file sniffers. Examine the file described by
2965 @var{abfd} and look at ABI tag note sections to determine the OS ABI
2966 from the note. This function should be called via
2967 @code{bfd_map_over_sections}.
2970 @node Initialize New Architecture
2971 @section Initializing a New Architecture
2974 * How an Architecture is Represented::
2975 * Looking Up an Existing Architecture::
2976 * Creating a New Architecture::
2979 @node How an Architecture is Represented
2980 @subsection How an Architecture is Represented
2981 @cindex architecture representation
2982 @cindex representation of architecture
2984 Each @code{gdbarch} is associated with a single @sc{bfd} architecture,
2985 via a @code{bfd_arch_@var{arch}} in the @code{bfd_architecture}
2986 enumeration. The @code{gdbarch} is registered by a call to
2987 @code{register_gdbarch_init}, usually from the file's
2988 @code{_initialize_@var{filename}} routine, which will be automatically
2989 called during @value{GDBN} startup. The arguments are a @sc{bfd}
2990 architecture constant and an initialization function.
2992 @findex _initialize_@var{arch}_tdep
2993 @cindex @file{@var{arch}-tdep.c}
2994 A @value{GDBN} description for a new architecture, @var{arch} is created by
2995 defining a global function @code{_initialize_@var{arch}_tdep}, by
2996 convention in the source file @file{@var{arch}-tdep.c}. For example,
2997 in the case of the OpenRISC 1000, this function is called
2998 @code{_initialize_or1k_tdep} and is found in the file
3001 @cindex @file{configure.tgt}
3002 @cindex @code{gdbarch}
3003 @findex gdbarch_register
3004 The resulting object files containing the implementation of the
3005 @code{_initialize_@var{arch}_tdep} function are specified in the @value{GDBN}
3006 @file{configure.tgt} file, which includes a large case statement
3007 pattern matching against the @code{--target} option of the
3008 @code{configure} script. The new @code{struct gdbarch} is created
3009 within the @code{_initialize_@var{arch}_tdep} function by calling
3010 @code{gdbarch_register}:
3013 void gdbarch_register (enum bfd_architecture @var{architecture},
3014 gdbarch_init_ftype *@var{init_func},
3015 gdbarch_dump_tdep_ftype *@var{tdep_dump_func});
3018 The @var{architecture} will identify the unique @sc{bfd} to be
3019 associated with this @code{gdbarch}. The @var{init_func} funciton is
3020 called to create and return the new @code{struct gdbarch}. The
3021 @var{tdep_dump_func} function will dump the target specific details
3022 associated with this architecture.
3024 For example the function @code{_initialize_or1k_tdep} creates its
3025 architecture for 32-bit OpenRISC 1000 architectures by calling:
3028 gdbarch_register (bfd_arch_or32, or1k_gdbarch_init, or1k_dump_tdep);
3031 @node Looking Up an Existing Architecture
3032 @subsection Looking Up an Existing Architecture
3033 @cindex @code{gdbarch} lookup
3035 The initialization function has this prototype:
3038 static struct gdbarch *
3039 @var{arch}_gdbarch_init (struct gdbarch_info @var{info},
3040 struct gdbarch_list *@var{arches})
3043 The @var{info} argument contains parameters used to select the correct
3044 architecture, and @var{arches} is a list of architectures which
3045 have already been created with the same @code{bfd_arch_@var{arch}}
3048 The initialization function should first make sure that @var{info}
3049 is acceptable, and return @code{NULL} if it is not. Then, it should
3050 search through @var{arches} for an exact match to @var{info}, and
3051 return one if found. Lastly, if no exact match was found, it should
3052 create a new architecture based on @var{info} and return it.
3054 @findex gdbarch_list_lookup_by_info
3055 @cindex @code{gdbarch_info}
3056 The lookup is done using @code{gdbarch_list_lookup_by_info}. It is
3057 passed the list of existing architectures, @var{arches}, and the
3058 @code{struct gdbarch_info}, @var{info}, and returns the first matching
3059 architecture it finds, or @code{NULL} if none are found. If an
3060 architecture is found it can be returned as the result from the
3061 initialization function, otherwise a new @code{struct gdbach} will need
3064 The struct gdbarch_info has the following components:
3069 const struct bfd_arch_info *bfd_arch_info;
3072 struct gdbarch_tdep_info *tdep_info;
3073 enum gdb_osabi osabi;
3074 const struct target_desc *target_desc;
3078 @vindex bfd_arch_info
3079 The @code{bfd_arch_info} member holds the key details about the
3080 architecture. The @code{byte_order} member is a value in an
3081 enumeration indicating the endianism. The @code{abfd} member is a
3082 pointer to the full @sc{bfd}, the @code{tdep_info} member is
3083 additional custom target specific information, @code{osabi} identifies
3084 which (if any) of a number of operating specific ABIs are used by this
3085 architecture and the @code{target_desc} member is a set of name-value
3086 pairs with information about register usage in this target.
3088 When the @code{struct gdbarch} initialization function is called, not
3089 all the fields are provided---only those which can be deduced from the
3090 @sc{bfd}. The @code{struct gdbarch_info}, @var{info} is used as a
3091 look-up key with the list of existing architectures, @var{arches} to
3092 see if a suitable architecture already exists. The @var{tdep_info},
3093 @var{osabi} and @var{target_desc} fields may be added before this
3094 lookup to refine the search.
3096 Only information in @var{info} should be used to choose the new
3097 architecture. Historically, @var{info} could be sparse, and
3098 defaults would be collected from the first element on @var{arches}.
3099 However, @value{GDBN} now fills in @var{info} more thoroughly,
3100 so new @code{gdbarch} initialization functions should not take
3101 defaults from @var{arches}.
3103 @node Creating a New Architecture
3104 @subsection Creating a New Architecture
3105 @cindex @code{struct gdbarch} creation
3107 @findex gdbarch_alloc
3108 @cindex @code{gdbarch_tdep} when allocating new @code{gdbarch}
3109 If no architecture is found, then a new architecture must be created,
3110 by calling @code{gdbarch_alloc} using the supplied @code{@w{struct
3111 gdbarch_info}} and any additional custom target specific
3112 information in a @code{struct gdbarch_tdep}. The prototype for
3113 @code{gdbarch_alloc} is:
3116 struct gdbarch *gdbarch_alloc (const struct gdbarch_info *@var{info},
3117 struct gdbarch_tdep *@var{tdep});
3120 @cindex @code{set_gdbarch} functions
3121 @cindex @code{gdbarch} accessor functions
3122 The newly created struct gdbarch must then be populated. Although
3123 there are default values, in most cases they are not what is
3126 For each element, @var{X}, there is are a pair of corresponding accessor
3127 functions, one to set the value of that element,
3128 @code{set_gdbarch_@var{X}}, the second to either get the value of an
3129 element (if it is a variable) or to apply the element (if it is a
3130 function), @code{gdbarch_@var{X}}. Note that both accessor functions
3131 take a pointer to the @code{@w{struct gdbarch}} as first
3132 argument. Populating the new @code{gdbarch} should use the
3133 @code{set_gdbarch} functions.
3135 The following sections identify the main elements that should be set
3136 in this way. This is not the complete list, but represents the
3137 functions and elements that must commonly be specified for a new
3138 architecture. Many of the functions and variables are described in the
3139 header file @file{gdbarch.h}.
3141 This is the main work in defining a new architecture. Implementing the
3142 set of functions to populate the @code{struct gdbarch}.
3144 @cindex @code{gdbarch_tdep} definition
3145 @code{struct gdbarch_tdep} is not defined within @value{GDBN}---it is up
3146 to the user to define this struct if it is needed to hold custom target
3147 information that is not covered by the standard @code{@w{struct
3148 gdbarch}}. For example with the OpenRISC 1000 architecture it is used to
3149 hold the number of matchpoints available in the target (along with other
3152 If there is no additional target specific information, it can be set to
3155 @node Registers and Memory
3156 @section Registers and Memory
3158 @value{GDBN}'s model of the target machine is rather simple.
3159 @value{GDBN} assumes the machine includes a bank of registers and a
3160 block of memory. Each register may have a different size.
3162 @value{GDBN} does not have a magical way to match up with the
3163 compiler's idea of which registers are which; however, it is critical
3164 that they do match up accurately. The only way to make this work is
3165 to get accurate information about the order that the compiler uses,
3166 and to reflect that in the @code{gdbarch_register_name} and related functions.
3168 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
3170 @node Pointers and Addresses
3171 @section Pointers Are Not Always Addresses
3172 @cindex pointer representation
3173 @cindex address representation
3174 @cindex word-addressed machines
3175 @cindex separate data and code address spaces
3176 @cindex spaces, separate data and code address
3177 @cindex address spaces, separate data and code
3178 @cindex code pointers, word-addressed
3179 @cindex converting between pointers and addresses
3180 @cindex D10V addresses
3182 On almost all 32-bit architectures, the representation of a pointer is
3183 indistinguishable from the representation of some fixed-length number
3184 whose value is the byte address of the object pointed to. On such
3185 machines, the words ``pointer'' and ``address'' can be used interchangeably.
3186 However, architectures with smaller word sizes are often cramped for
3187 address space, so they may choose a pointer representation that breaks this
3188 identity, and allows a larger code address space.
3190 @c D10V is gone from sources - more current example?
3192 For example, the Renesas D10V is a 16-bit VLIW processor whose
3193 instructions are 32 bits long@footnote{Some D10V instructions are
3194 actually pairs of 16-bit sub-instructions. However, since you can't
3195 jump into the middle of such a pair, code addresses can only refer to
3196 full 32 bit instructions, which is what matters in this explanation.}.
3197 If the D10V used ordinary byte addresses to refer to code locations,
3198 then the processor would only be able to address 64kb of instructions.
3199 However, since instructions must be aligned on four-byte boundaries, the
3200 low two bits of any valid instruction's byte address are always
3201 zero---byte addresses waste two bits. So instead of byte addresses,
3202 the D10V uses word addresses---byte addresses shifted right two bits---to
3203 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
3206 However, this means that code pointers and data pointers have different
3207 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
3208 @code{0xC020} when used as a data address, but refers to byte address
3209 @code{0x30080} when used as a code address.
3211 (The D10V also uses separate code and data address spaces, which also
3212 affects the correspondence between pointers and addresses, but we're
3213 going to ignore that here; this example is already too long.)
3215 To cope with architectures like this---the D10V is not the only
3216 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
3217 byte numbers, and @dfn{pointers}, which are the target's representation
3218 of an address of a particular type of data. In the example above,
3219 @code{0xC020} is the pointer, which refers to one of the addresses
3220 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
3221 @value{GDBN} provides functions for turning a pointer into an address
3222 and vice versa, in the appropriate way for the current architecture.
3224 Unfortunately, since addresses and pointers are identical on almost all
3225 processors, this distinction tends to bit-rot pretty quickly. Thus,
3226 each time you port @value{GDBN} to an architecture which does
3227 distinguish between pointers and addresses, you'll probably need to
3228 clean up some architecture-independent code.
3230 Here are functions which convert between pointers and addresses:
3232 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
3233 Treat the bytes at @var{buf} as a pointer or reference of type
3234 @var{type}, and return the address it represents, in a manner
3235 appropriate for the current architecture. This yields an address
3236 @value{GDBN} can use to read target memory, disassemble, etc. Note that
3237 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
3240 For example, if the current architecture is the Intel x86, this function
3241 extracts a little-endian integer of the appropriate length from
3242 @var{buf} and returns it. However, if the current architecture is the
3243 D10V, this function will return a 16-bit integer extracted from
3244 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
3246 If @var{type} is not a pointer or reference type, then this function
3247 will signal an internal error.
3250 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
3251 Store the address @var{addr} in @var{buf}, in the proper format for a
3252 pointer of type @var{type} in the current architecture. Note that
3253 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
3256 For example, if the current architecture is the Intel x86, this function
3257 stores @var{addr} unmodified as a little-endian integer of the
3258 appropriate length in @var{buf}. However, if the current architecture
3259 is the D10V, this function divides @var{addr} by four if @var{type} is
3260 a pointer to a function, and then stores it in @var{buf}.
3262 If @var{type} is not a pointer or reference type, then this function
3263 will signal an internal error.
3266 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
3267 Assuming that @var{val} is a pointer, return the address it represents,
3268 as appropriate for the current architecture.
3270 This function actually works on integral values, as well as pointers.
3271 For pointers, it performs architecture-specific conversions as
3272 described above for @code{extract_typed_address}.
3275 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
3276 Create and return a value representing a pointer of type @var{type} to
3277 the address @var{addr}, as appropriate for the current architecture.
3278 This function performs architecture-specific conversions as described
3279 above for @code{store_typed_address}.
3282 Here are two functions which architectures can define to indicate the
3283 relationship between pointers and addresses. These have default
3284 definitions, appropriate for architectures on which all pointers are
3285 simple unsigned byte addresses.
3287 @deftypefun CORE_ADDR gdbarch_pointer_to_address (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf})
3288 Assume that @var{buf} holds a pointer of type @var{type}, in the
3289 appropriate format for the current architecture. Return the byte
3290 address the pointer refers to.
3292 This function may safely assume that @var{type} is either a pointer or a
3293 C@t{++} reference type.
3296 @deftypefun void gdbarch_address_to_pointer (struct gdbarch *@var{gdbarch}, struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
3297 Store in @var{buf} a pointer of type @var{type} representing the address
3298 @var{addr}, in the appropriate format for the current architecture.
3300 This function may safely assume that @var{type} is either a pointer or a
3301 C@t{++} reference type.
3304 @node Address Classes
3305 @section Address Classes
3306 @cindex address classes
3307 @cindex DW_AT_byte_size
3308 @cindex DW_AT_address_class
3310 Sometimes information about different kinds of addresses is available
3311 via the debug information. For example, some programming environments
3312 define addresses of several different sizes. If the debug information
3313 distinguishes these kinds of address classes through either the size
3314 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
3315 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
3316 following macros should be defined in order to disambiguate these
3317 types within @value{GDBN} as well as provide the added information to
3318 a @value{GDBN} user when printing type expressions.
3320 @deftypefun int gdbarch_address_class_type_flags (struct gdbarch *@var{gdbarch}, int @var{byte_size}, int @var{dwarf2_addr_class})
3321 Returns the type flags needed to construct a pointer type whose size
3322 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
3323 This function is normally called from within a symbol reader. See
3324 @file{dwarf2read.c}.
3327 @deftypefun {char *} gdbarch_address_class_type_flags_to_name (struct gdbarch *@var{gdbarch}, int @var{type_flags})
3328 Given the type flags representing an address class qualifier, return
3331 @deftypefun int gdbarch_address_class_name_to_type_flags (struct gdbarch *@var{gdbarch}, int @var{name}, int *@var{type_flags_ptr})
3332 Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags
3333 for that address class qualifier.
3336 Since the need for address classes is rather rare, none of
3337 the address class functions are defined by default. Predicate
3338 functions are provided to detect when they are defined.
3340 Consider a hypothetical architecture in which addresses are normally
3341 32-bits wide, but 16-bit addresses are also supported. Furthermore,
3342 suppose that the @w{DWARF 2} information for this architecture simply
3343 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
3344 of these "short" pointers. The following functions could be defined
3345 to implement the address class functions:
3348 somearch_address_class_type_flags (int byte_size,
3349 int dwarf2_addr_class)
3352 return TYPE_FLAG_ADDRESS_CLASS_1;
3358 somearch_address_class_type_flags_to_name (int type_flags)
3360 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
3367 somearch_address_class_name_to_type_flags (char *name,
3368 int *type_flags_ptr)
3370 if (strcmp (name, "short") == 0)
3372 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
3380 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
3381 to indicate the presence of one of these ``short'' pointers. For
3382 example if the debug information indicates that @code{short_ptr_var} is
3383 one of these short pointers, @value{GDBN} might show the following
3387 (gdb) ptype short_ptr_var
3388 type = int * @@short
3392 @node Register Representation
3393 @section Register Representation
3396 * Raw and Cooked Registers::
3397 * Register Architecture Functions & Variables::
3398 * Register Information Functions::
3399 * Register and Memory Data::
3400 * Register Caching::
3403 @node Raw and Cooked Registers
3404 @subsection Raw and Cooked Registers
3405 @cindex raw register representation
3406 @cindex cooked register representation
3407 @cindex representations, raw and cooked registers
3409 @value{GDBN} considers registers to be a set with members numbered
3410 linearly from 0 upwards. The first part of that set corresponds to real
3411 physical registers, the second part to any @dfn{pseudo-registers}.
3412 Pseudo-registers have no independent physical existence, but are useful
3413 representations of information within the architecture. For example the
3414 OpenRISC 1000 architecture has up to 32 general purpose registers, which
3415 are typically represented as 32-bit (or 64-bit) integers. However the
3416 GPRs are also used as operands to the floating point operations, and it
3417 could be convenient to define a set of pseudo-registers, to show the
3418 GPRs represented as floating point values.
3420 For any architecture, the implementer will decide on a mapping from
3421 hardware to @value{GDBN} register numbers. The registers corresponding to real
3422 hardware are referred to as @dfn{raw} registers, the remaining registers are
3423 @dfn{pseudo-registers}. The total register set (raw and pseudo) is called
3424 the @dfn{cooked} register set.
3427 @node Register Architecture Functions & Variables
3428 @subsection Functions and Variables Specifying the Register Architecture
3429 @cindex @code{gdbarch} register architecture functions
3431 These @code{struct gdbarch} functions and variables specify the number
3432 and type of registers in the architecture.
3434 @deftypefn {Architecture Function} CORE_ADDR read_pc (struct regcache *@var{regcache})
3436 @deftypefn {Architecture Function} void write_pc (struct regcache *@var{regcache}, CORE_ADDR @var{val})
3438 Read or write the program counter. The default value of both
3439 functions is @code{NULL} (no function available). If the program
3440 counter is just an ordinary register, it can be specified in
3441 @code{struct gdbarch} instead (see @code{pc_regnum} below) and it will
3442 be read or written using the standard routines to access registers. This
3443 function need only be specified if the program counter is not an
3446 Any register information can be obtained using the supplied register
3447 cache, @var{regcache}. @xref{Register Caching, , Register Caching}.
3451 @deftypefn {Architecture Function} void pseudo_register_read (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf})
3453 @deftypefn {Architecture Function} void pseudo_register_write (struct gdbarch *@var{gdbarch}, struct regcache *@var{regcache}, int @var{regnum}, const gdb_byte *@var{buf})
3455 These functions should be defined if there are any pseudo-registers.
3456 The default value is @code{NULL}. @var{regnum} is the number of the
3457 register to read or write (which will be a @dfn{cooked} register
3458 number) and @var{buf} is the buffer where the value read will be
3459 placed, or from which the value to be written will be taken. The
3460 value in the buffer may be converted to or from a signed or unsigned
3461 integral value using one of the utility functions (@pxref{Register and
3462 Memory Data, , Using Different Register and Memory Data
3465 The access should be for the specified architecture,
3466 @var{gdbarch}. Any register information can be obtained using the
3467 supplied register cache, @var{regcache}. @xref{Register Caching, ,
3472 @deftypevr {Architecture Variable} int sp_regnum
3474 @cindex stack pointer
3477 This specifies the register holding the stack pointer, which may be a
3478 raw or pseudo-register. It defaults to -1 (not defined), but it is an
3479 error for it not to be defined.
3481 The value of the stack pointer register can be accessed withing
3482 @value{GDBN} as the variable @kbd{$sp}.
3486 @deftypevr {Architecture Variable} int pc_regnum
3488 @cindex program counter
3491 This specifies the register holding the program counter, which may be a
3492 raw or pseudo-register. It defaults to -1 (not defined). If
3493 @code{pc_regnum} is not defined, then the functions @code{read_pc} and
3494 @code{write_pc} (see above) must be defined.
3496 The value of the program counter (whether defined as a register, or
3497 through @code{read_pc} and @code{write_pc}) can be accessed withing
3498 @value{GDBN} as the variable @kbd{$pc}.
3502 @deftypevr {Architecture Variable} int ps_regnum
3504 @cindex processor status register
3505 @cindex status register
3508 This specifies the register holding the processor status (often called
3509 the status register), which may be a raw or pseudo-register. It
3510 defaults to -1 (not defined).
3512 If defined, the value of this register can be accessed withing
3513 @value{GDBN} as the variable @kbd{$ps}.
3517 @deftypevr {Architecture Variable} int fp0_regnum
3519 @cindex first floating point register
3521 This specifies the first floating point register. It defaults to
3522 0. @code{fp0_regnum} is not needed unless the target offers support
3527 @node Register Information Functions
3528 @subsection Functions Giving Register Information
3529 @cindex @code{gdbarch} register information functions
3531 These functions return information about registers.
3533 @deftypefn {Architecture Function} {const char *} register_name (struct gdbarch *@var{gdbarch}, int @var{regnum})
3535 This function should convert a register number (raw or pseudo) to a
3536 register name (as a C @code{const char *}). This is used both to
3537 determine the name of a register for output and to work out the meaning
3538 of any register names used as input. The function may also return
3539 @code{NULL}, to indicate that @var{regnum} is not a valid register.
3541 For example with the OpenRISC 1000, @value{GDBN} registers 0-31 are the
3542 General Purpose Registers, register 32 is the program counter and
3543 register 33 is the supervision register (i.e.@: the processor status
3544 register), which map to the strings @code{"gpr00"} through
3545 @code{"gpr31"}, @code{"pc"} and @code{"sr"} respectively. This means
3546 that the @value{GDBN} command @kbd{print $gpr5} should print the value of
3547 the OR1K general purpose register 5@footnote{
3548 @cindex frame pointer
3550 Historically, @value{GDBN} always had a concept of a frame pointer
3551 register, which could be accessed via the @value{GDBN} variable,
3552 @kbd{$fp}. That concept is now deprecated, recognizing that not all
3553 architectures have a frame pointer. However if an architecture does
3554 have a frame pointer register, and defines a register or
3555 pseudo-register with the name @code{"fp"}, then that register will be
3556 used as the value of the @kbd{$fp} variable.}.
3558 The default value for this function is @code{NULL}, meaning
3559 undefined. It should always be defined.
3561 The access should be for the specified architecture, @var{gdbarch}.
3565 @deftypefn {Architecture Function} {struct type *} register_type (struct gdbarch *@var{gdbarch}, int @var{regnum})
3567 Given a register number, this function identifies the type of data it
3568 may be holding, specified as a @code{struct type}. @value{GDBN} allows
3569 creation of arbitrary types, but a number of built in types are
3570 provided (@code{builtin_type_void}, @code{builtin_type_int32} etc),
3571 together with functions to derive types from these.
3573 Typically the program counter will have a type of ``pointer to
3574 function'' (it points to code), the frame pointer and stack pointer
3575 will have types of ``pointer to void'' (they point to data on the stack)
3576 and all other integer registers will have a type of 32-bit integer or
3579 This information guides the formatting when displaying register
3580 information. The default value is @code{NULL} meaning no information is
3581 available to guide formatting when displaying registers.
3585 @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})
3587 Define this function to print out one or all of the registers for the
3588 @value{GDBN} @kbd{info registers} command. The default value is the
3589 function @code{default_print_registers_info}, which uses the register
3590 type information (see @code{register_type} above) to determine how each
3591 register should be printed. Define a custom version of this function
3592 for fuller control over how the registers are displayed.
3594 The access should be for the specified architecture, @var{gdbarch},
3595 with output to the file specified by the User Interface
3596 Independent Output file handle, @var{file} (@pxref{UI-Independent
3597 Output, , UI-Independent Output---the @code{ui_out}
3600 The registers should show their values in the frame specified by
3601 @var{frame}. If @var{regnum} is -1 and @var{all} is zero, then all
3602 the ``significant'' registers should be shown (the implementer should
3603 decide which registers are ``significant''). Otherwise only the value of
3604 the register specified by @var{regnum} should be output. If
3605 @var{regnum} is -1 and @var{all} is non-zero (true), then the value of
3606 all registers should be shown.
3608 By default @code{default_print_registers_info} prints one register per
3609 line, and if @var{all} is zero omits floating-point registers.
3613 @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})
3615 Define this function to provide output about the floating point unit and
3616 registers for the @value{GDBN} @kbd{info float} command respectively.
3617 The default value is @code{NULL} (not defined), meaning no information
3620 The @var{gdbarch} and @var{file} and @var{frame} arguments have the same
3621 meaning as in the @code{print_registers_info} function above. The string
3622 @var{args} contains any supplementary arguments to the @kbd{info float}
3625 Define this function if the target supports floating point operations.
3629 @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})
3631 Define this function to provide output about the vector unit and
3632 registers for the @value{GDBN} @kbd{info vector} command respectively.
3633 The default value is @code{NULL} (not defined), meaning no information
3636 The @var{gdbarch}, @var{file} and @var{frame} arguments have the
3637 same meaning as in the @code{print_registers_info} function above. The
3638 string @var{args} contains any supplementary arguments to the @kbd{info
3641 Define this function if the target supports vector operations.
3645 @deftypefn {Architecture Function} int register_reggroup_p (struct gdbarch *@var{gdbarch}, int @var{regnum}, struct reggroup *@var{group})
3647 @value{GDBN} groups registers into different categories (general,
3648 vector, floating point etc). This function, given a register,
3649 @var{regnum}, and group, @var{group}, returns 1 (true) if the register
3650 is in the group and 0 (false) otherwise.
3652 The information should be for the specified architecture,
3655 The default value is the function @code{default_register_reggroup_p}
3656 which will do a reasonable job based on the type of the register (see
3657 the function @code{register_type} above), with groups for general
3658 purpose registers, floating point registers, vector registers and raw
3659 (i.e not pseudo) registers.
3663 @node Register and Memory Data
3664 @subsection Using Different Register and Memory Data Representations
3665 @cindex register representation
3666 @cindex memory representation
3667 @cindex representations, register and memory
3668 @cindex register data formats, converting
3669 @cindex @code{struct value}, converting register contents to
3671 Some architectures have different representations of data objects,
3672 depending whether the object is held in a register or memory. For
3678 The Alpha architecture can represent 32 bit integer values in
3679 floating-point registers.
3682 The x86 architecture supports 80-bit floating-point registers. The
3683 @code{long double} data type occupies 96 bits in memory but only 80
3684 bits when stored in a register.
3688 In general, the register representation of a data type is determined by
3689 the architecture, or @value{GDBN}'s interface to the architecture, while
3690 the memory representation is determined by the Application Binary
3693 For almost all data types on almost all architectures, the two
3694 representations are identical, and no special handling is needed.
3695 However, they do occasionally differ. An architecture may define the
3696 following @code{struct gdbarch} functions to request conversions
3697 between the register and memory representations of a data type:
3699 @deftypefn {Architecture Function} int gdbarch_convert_register_p (struct gdbarch *@var{gdbarch}, int @var{reg})
3701 Return non-zero (true) if the representation of a data value stored in
3702 this register may be different to the representation of that same data
3703 value when stored in memory. The default value is @code{NULL}
3706 If this function is defined and returns non-zero, the @code{struct
3707 gdbarch} functions @code{gdbarch_register_to_value} and
3708 @code{gdbarch_value_to_register} (see below) should be used to perform
3709 any necessary conversion.
3711 If defined, this function should return zero for the register's native
3712 type, when no conversion is necessary.
3715 @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})
3717 Convert the value of register number @var{reg} to a data object of
3718 type @var{type}. The buffer at @var{from} holds the register's value
3719 in raw format; the converted value should be placed in the buffer at
3723 @emph{Note:} @code{gdbarch_register_to_value} and
3724 @code{gdbarch_value_to_register} take their @var{reg} and @var{type}
3725 arguments in different orders.
3728 @code{gdbarch_register_to_value} should only be used with registers
3729 for which the @code{gdbarch_convert_register_p} function returns a
3734 @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})
3736 Convert a data value of type @var{type} to register number @var{reg}'
3740 @emph{Note:} @code{gdbarch_register_to_value} and
3741 @code{gdbarch_value_to_register} take their @var{reg} and @var{type}
3742 arguments in different orders.
3745 @code{gdbarch_value_to_register} should only be used with registers
3746 for which the @code{gdbarch_convert_register_p} function returns a
3751 @node Register Caching
3752 @subsection Register Caching
3753 @cindex register caching
3755 Caching of registers is used, so that the target does not need to be
3756 accessed and reanalyzed multiple times for each register in
3757 circumstances where the register value cannot have changed.
3759 @cindex @code{struct regcache}
3760 @value{GDBN} provides @code{struct regcache}, associated with a
3761 particular @code{struct gdbarch} to hold the cached values of the raw
3762 registers. A set of functions is provided to access both the raw
3763 registers (with @code{raw} in their name) and the full set of cooked
3764 registers (with @code{cooked} in their name). Functions are provided
3765 to ensure the register cache is kept synchronized with the values of
3766 the actual registers in the target.
3768 Accessing registers through the @code{struct regcache} routines will
3769 ensure that the appropriate @code{struct gdbarch} functions are called
3770 when necessary to access the underlying target architecture. In general
3771 users should use the @dfn{cooked} functions, since these will map to the
3772 @dfn{raw} functions automatically as appropriate.
3774 @findex regcache_cooked_read
3775 @findex regcache_cooked_write
3776 @cindex @code{gdb_byte}
3777 @findex regcache_cooked_read_signed
3778 @findex regcache_cooked_read_unsigned
3779 @findex regcache_cooked_write_signed
3780 @findex regcache_cooked_write_unsigned
3781 The two key functions are @code{regcache_cooked_read} and
3782 @code{regcache_cooked_write} which read or write a register from or to
3783 a byte buffer (type @code{gdb_byte *}). For convenience the wrapper
3784 functions @code{regcache_cooked_read_signed},
3785 @code{regcache_cooked_read_unsigned},
3786 @code{regcache_cooked_write_signed} and
3787 @code{regcache_cooked_write_unsigned} are provided, which read or
3788 write the value using the buffer and convert to or from an integral
3789 value as appropriate.
3791 @node Frame Interpretation
3792 @section Frame Interpretation
3795 * All About Stack Frames::
3796 * Frame Handling Terminology::
3798 * Functions and Variable to Analyze Frames::
3799 * Functions to Access Frame Data::
3800 * Analyzing Stacks---Frame Sniffers::
3803 @node All About Stack Frames
3804 @subsection All About Stack Frames
3806 @value{GDBN} needs to understand the stack on which local (automatic)
3807 variables are stored. The area of the stack containing all the local
3808 variables for a function invocation is known as the @dfn{stack frame}
3809 for that function (or colloquially just as the @dfn{frame}). In turn the
3810 function that called the function will have its stack frame, and so on
3811 back through the chain of functions that have been called.
3813 Almost all architectures have one register dedicated to point to the
3814 end of the stack (the @dfn{stack pointer}). Many have a second register
3815 which points to the start of the currently active stack frame (the
3816 @dfn{frame pointer}). The specific arrangements for an architecture are
3817 a key part of the ABI.
3819 A diagram helps to explain this. Here is a simple program to compute
3832 return n * fact (n - 1);
3840 for (i = 0; i < 10; i++)
3843 printf ("%d! = %d\n", i, f);
3848 Consider the state of the stack when the code reaches line 6 after the
3849 main program has called @code{fact@w{ }(3)}. The chain of function
3850 calls will be @code{main ()}, @code{fact@w{ }(3)}, @code{fact@w{
3851 }(2)}, @code{@w{fact (1)}} and @code{fact@w{ }(0)}.
3853 In this illustration the stack is falling (as used for example by the
3854 OpenRISC 1000 ABI). The stack pointer (SP) is at the end of the stack
3855 (lowest address) and the frame pointer (FP) is at the highest address
3856 in the current stack frame. The following diagram shows how the stack
3859 @center @image{stack_frame,14cm}
3861 In each stack frame, offset 0 from the stack pointer is the frame
3862 pointer of the previous frame and offset 4 (this is illustrating a
3863 32-bit architecture) from the stack pointer is the return address.
3864 Local variables are indexed from the frame pointer, with negative
3865 indexes. In the function @code{fact}, offset -4 from the frame
3866 pointer is the argument @var{n}. In the @code{main} function, offset
3867 -4 from the frame pointer is the local variable @var{i} and offset -8
3868 from the frame pointer is the local variable @var{f}@footnote{This is
3869 a simplified example for illustrative purposes only. Good optimizing
3870 compilers would not put anything on the stack for such simple
3871 functions. Indeed they might eliminate the recursion and use of the
3874 It is very easy to get confused when examining stacks. @value{GDBN}
3875 has terminology it uses rigorously throughout. The stack frame of the
3876 function currently executing, or where execution stopped is numbered
3877 zero. In this example frame #0 is the stack frame of the call to
3878 @code{fact@w{ }(0)}. The stack frame of its calling function
3879 (@code{fact@w{ }(1)} in this case) is numbered #1 and so on back
3880 through the chain of calls.
3882 The main @value{GDBN} data structure describing frames is
3883 @code{@w{struct frame_info}}. It is not used directly, but only via
3884 its accessor functions. @code{frame_info} includes information about
3885 the registers in the frame and a pointer to the code of the function
3886 with which the frame is associated. The entire stack is represented as
3887 a linked list of @code{frame_info} structs.
3889 @node Frame Handling Terminology
3890 @subsection Frame Handling Terminology
3892 It is easy to get confused when referencing stack frames. @value{GDBN}
3893 uses some precise terminology.
3899 @cindex stack frame, definition of THIS frame
3900 @cindex frame, definition of THIS frame
3901 @dfn{THIS} frame is the frame currently under consideration.
3905 @cindex stack frame, definition of NEXT frame
3906 @cindex frame, definition of NEXT frame
3907 The @dfn{NEXT} frame, also sometimes called the inner or newer frame is the
3908 frame of the function called by the function of THIS frame.
3911 @cindex PREVIOUS frame
3912 @cindex stack frame, definition of PREVIOUS frame
3913 @cindex frame, definition of PREVIOUS frame
3914 The @dfn{PREVIOUS} frame, also sometimes called the outer or older frame is
3915 the frame of the function which called the function of THIS frame.
3919 So in the example in the previous section (@pxref{All About Stack
3920 Frames, , All About Stack Frames}), if THIS frame is #3 (the call to
3921 @code{fact@w{ }(3)}), the NEXT frame is frame #2 (the call to
3922 @code{fact@w{ }(2)}) and the PREVIOUS frame is frame #4 (the call to
3923 @code{main@w{ }()}).
3925 @cindex innermost frame
3926 @cindex stack frame, definition of innermost frame
3927 @cindex frame, definition of innermost frame
3928 The @dfn{innermost} frame is the frame of the current executing
3929 function, or where the program stopped, in this example, in the middle
3930 of the call to @code{@w{fact (0))}}. It is always numbered frame #0.
3932 @cindex base of a frame
3933 @cindex stack frame, definition of base of a frame
3934 @cindex frame, definition of base of a frame
3935 The @dfn{base} of a frame is the address immediately before the start
3936 of the NEXT frame. For a stack which grows down in memory (a
3937 @dfn{falling} stack) this will be the lowest address and for a stack
3938 which grows up in memory (a @dfn{rising} stack) this will be the
3939 highest address in the frame.
3941 @value{GDBN} functions to analyze the stack are typically given a
3942 pointer to the NEXT frame to determine information about THIS
3943 frame. Information about THIS frame includes data on where the
3944 registers of the PREVIOUS frame are stored in this stack frame. In
3945 this example the frame pointer of the PREVIOUS frame is stored at
3946 offset 0 from the stack pointer of THIS frame.
3949 @cindex stack frame, definition of unwinding
3950 @cindex frame, definition of unwinding
3951 The process whereby a function is given a pointer to the NEXT
3952 frame to work out information about THIS frame is referred to as
3953 @dfn{unwinding}. The @value{GDBN} functions involved in this typically
3954 include unwind in their name.
3957 @cindex stack frame, definition of sniffing
3958 @cindex frame, definition of sniffing
3959 The process of analyzing a target to determine the information that
3960 should go in struct frame_info is called @dfn{sniffing}. The functions
3961 that carry this out are called sniffers and typically include sniffer
3962 in their name. More than one sniffer may be required to extract all
3963 the information for a particular frame.
3965 @cindex sentinel frame
3966 @cindex stack frame, definition of sentinel frame
3967 @cindex frame, definition of sentinel frame
3968 Because so many functions work using the NEXT frame, there is an issue
3969 about addressing the innermost frame---it has no NEXT frame. To solve
3970 this @value{GDBN} creates a dummy frame #-1, known as the
3971 @dfn{sentinel} frame.
3973 @node Prologue Caches
3974 @subsection Prologue Caches
3976 @cindex function prologue
3977 @cindex prologue of a function
3978 All the frame sniffing functions typically examine the code at the
3979 start of the corresponding function, to determine the state of
3980 registers. The ABI will save old values and set new values of key
3981 registers at the start of each function in what is known as the
3982 function @dfn{prologue}.
3984 @cindex prologue cache
3985 For any particular stack frame this data does not change, so all the
3986 standard unwinding functions, in addition to receiving a pointer to
3987 the NEXT frame as their first argument, receive a pointer to a
3988 @dfn{prologue cache} as their second argument. This can be used to store
3989 values associated with a particular frame, for reuse on subsequent
3990 calls involving the same frame.
3992 It is up to the user to define the structure used (it is a
3993 @code{void@w{ }*} pointer) and arrange allocation and deallocation of
3994 storage. However for general use, @value{GDBN} provides
3995 @code{@w{struct trad_frame_cache}}, with a set of accessor
3996 routines. This structure holds the stack and code address of
3997 THIS frame, the base address of the frame, a pointer to the
3998 struct @code{frame_info} for the NEXT frame and details of
3999 where the registers of the PREVIOUS frame may be found in THIS
4002 Typically the first time any sniffer function is called with NEXT
4003 frame, the prologue sniffer for THIS frame will be @code{NULL}. The
4004 sniffer will analyze the frame, allocate a prologue cache structure
4005 and populate it. Subsequent calls using the same NEXT frame will
4006 pass in this prologue cache, so the data can be returned with no
4007 additional analysis.
4009 @node Functions and Variable to Analyze Frames
4010 @subsection Functions and Variable to Analyze Frames
4012 These struct @code{gdbarch} functions and variable should be defined
4013 to provide analysis of the stack frame and allow it to be adjusted as
4016 @deftypefn {Architecture Function} CORE_ADDR skip_prologue (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{pc})
4018 The prologue of a function is the code at the beginning of the
4019 function which sets up the stack frame, saves the return address
4020 etc. The code representing the behavior of the function starts after
4023 This function skips past the prologue of a function if the program
4024 counter, @var{pc}, is within the prologue of a function. The result is
4025 the program counter immediately after the prologue. With modern
4026 optimizing compilers, this may be a far from trivial exercise. However
4027 the required information may be within the binary as DWARF2 debugging
4028 information, making the job much easier.
4030 The default value is @code{NULL} (not defined). This function should always
4031 be provided, but can take advantage of DWARF2 debugging information,
4032 if that is available.
4036 @deftypefn {Architecture Function} int inner_than (CORE_ADDR @var{lhs}, CORE_ADDR @var{rhs})
4037 @findex core_addr_lessthan
4038 @findex core_addr_greaterthan
4040 Given two frame or stack pointers, return non-zero (true) if the first
4041 represents the @dfn{inner} stack frame and 0 (false) otherwise. This
4042 is used to determine whether the target has a stack which grows up in
4043 memory (rising stack) or grows down in memory (falling stack).
4044 @xref{All About Stack Frames, , All About Stack Frames}, for an
4045 explanation of @dfn{inner} frames.
4047 The default value of this function is @code{NULL} and it should always
4048 be defined. However for almost all architectures one of the built-in
4049 functions can be used: @code{core_addr_lessthan} (for stacks growing
4050 down in memory) or @code{core_addr_greaterthan} (for stacks growing up
4055 @anchor{frame_align}
4056 @deftypefn {Architecture Function} CORE_ADDR frame_align (struct gdbarch *@var{gdbarch}, CORE_ADDR @var{address})
4060 The architecture may have constraints on how its frames are
4061 aligned. For example the OpenRISC 1000 ABI requires stack frames to be
4062 double-word aligned, but 32-bit versions of the architecture allocate
4063 single-word values to the stack. Thus extra padding may be needed at
4064 the end of a stack frame.
4066 Given a proposed address for the stack pointer, this function
4067 returns a suitably aligned address (by expanding the stack frame).
4069 The default value is @code{NULL} (undefined). This function should be defined
4070 for any architecture where it is possible the stack could become
4071 misaligned. The utility functions @code{align_down} (for falling
4072 stacks) and @code{align_up} (for rising stacks) will facilitate the
4073 implementation of this function.
4077 @deftypevr {Architecture Variable} int frame_red_zone_size
4079 Some ABIs reserve space beyond the end of the stack for use by leaf
4080 functions without prologue or epilogue or by exception handlers (for
4081 example the OpenRISC 1000).
4083 This is known as a @dfn{red zone} (AMD terminology). The @sc{amd64}
4084 (nee x86-64) ABI documentation refers to the @dfn{red zone} when
4085 describing this scratch area.
4087 The default value is 0. Set this field if the architecture has such a
4088 red zone. The value must be aligned as required by the ABI (see
4089 @code{frame_align} above for an explanation of stack frame alignment).
4093 @node Functions to Access Frame Data
4094 @subsection Functions to Access Frame Data
4096 These functions provide access to key registers and arguments in the
4099 @deftypefn {Architecture Function} CORE_ADDR unwind_pc (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4101 This function is given a pointer to the NEXT stack frame (@pxref{All
4102 About Stack Frames, , All About Stack Frames}, for how frames are
4103 represented) and returns the value of the program counter in the
4104 PREVIOUS frame (i.e.@: the frame of the function that called THIS
4105 one). This is commonly referred to as the @dfn{return address}.
4107 The implementation, which must be frame agnostic (work with any frame),
4108 is typically no more than:
4112 pc = frame_unwind_register_unsigned (next_frame, @var{ARCH}_PC_REGNUM);
4113 return gdbarch_addr_bits_remove (gdbarch, pc);
4118 @deftypefn {Architecture Function} CORE_ADDR unwind_sp (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4120 This function is given a pointer to the NEXT stack frame
4121 (@pxref{All About Stack Frames, , All About Stack Frames} for how
4122 frames are represented) and returns the value of the stack pointer in
4123 the PREVIOUS frame (i.e.@: the frame of the function that called
4126 The implementation, which must be frame agnostic (work with any frame),
4127 is typically no more than:
4131 sp = frame_unwind_register_unsigned (next_frame, @var{ARCH}_SP_REGNUM);
4132 return gdbarch_addr_bits_remove (gdbarch, sp);
4137 @deftypefn {Architecture Function} int frame_num_args (struct gdbarch *@var{gdbarch}, struct frame_info *@var{this_frame})
4139 This function is given a pointer to THIS stack frame (@pxref{All
4140 About Stack Frames, , All About Stack Frames} for how frames are
4141 represented), and returns the number of arguments that are being
4142 passed, or -1 if not known.
4144 The default value is @code{NULL} (undefined), in which case the number of
4145 arguments passed on any stack frame is always unknown. For many
4146 architectures this will be a suitable default.
4150 @node Analyzing Stacks---Frame Sniffers
4151 @subsection Analyzing Stacks---Frame Sniffers
4153 When a program stops, @value{GDBN} needs to construct the chain of
4154 struct @code{frame_info} representing the state of the stack using
4155 appropriate @dfn{sniffers}.
4157 Each architecture requires appropriate sniffers, but they do not form
4158 entries in @code{@w{struct gdbarch}}, since more than one sniffer may
4159 be required and a sniffer may be suitable for more than one
4160 @code{@w{struct gdbarch}}. Instead sniffers are associated with
4161 architectures using the following functions.
4166 @findex frame_unwind_append_sniffer
4167 @code{frame_unwind_append_sniffer} is used to add a new sniffer to
4168 analyze THIS frame when given a pointer to the NEXT frame.
4171 @findex frame_base_append_sniffer
4172 @code{frame_base_append_sniffer} is used to add a new sniffer
4173 which can determine information about the base of a stack frame.
4176 @findex frame_base_set_default
4177 @code{frame_base_set_default} is used to specify the default base
4182 These functions all take a reference to @code{@w{struct gdbarch}}, so
4183 they are associated with a specific architecture. They are usually
4184 called in the @code{gdbarch} initialization function, after the
4185 @code{gdbarch} struct has been set up. Unless a default has been set, the
4186 most recently appended sniffer will be tried first.
4188 The main frame unwinding sniffer (as set by
4189 @code{frame_unwind_append_sniffer)} returns a structure specifying
4190 a set of sniffing functions:
4192 @cindex @code{frame_unwind}
4196 enum frame_type type;
4197 frame_this_id_ftype *this_id;
4198 frame_prev_register_ftype *prev_register;
4199 const struct frame_data *unwind_data;
4200 frame_sniffer_ftype *sniffer;
4201 frame_prev_pc_ftype *prev_pc;
4202 frame_dealloc_cache_ftype *dealloc_cache;
4206 The @code{type} field indicates the type of frame this sniffer can
4207 handle: normal, dummy (@pxref{Functions Creating Dummy Frames, ,
4208 Functions Creating Dummy Frames}), signal handler or sentinel. Signal
4209 handlers sometimes have their own simplified stack structure for
4210 efficiency, so may need their own handlers.
4212 The @code{unwind_data} field holds additional information which may be
4213 relevant to particular types of frame. For example it may hold
4214 additional information for signal handler frames.
4216 The remaining fields define functions that yield different types of
4217 information when given a pointer to the NEXT stack frame. Not all
4218 functions need be provided. If an entry is @code{NULL}, the next sniffer will
4224 @code{this_id} determines the stack pointer and function (code
4225 entry point) for THIS stack frame.
4228 @code{prev_register} determines where the values of registers for
4229 the PREVIOUS stack frame are stored in THIS stack frame.
4232 @code{sniffer} takes a look at THIS frame's registers to
4233 determine if this is the appropriate unwinder.
4236 @code{prev_pc} determines the program counter for THIS
4237 frame. Only needed if the program counter is not an ordinary register
4238 (@pxref{Register Architecture Functions & Variables,
4239 , Functions and Variables Specifying the Register Architecture}).
4242 @code{dealloc_cache} frees any additional memory associated with
4243 the prologue cache for this frame (@pxref{Prologue Caches, , Prologue
4248 In general it is only the @code{this_id} and @code{prev_register}
4249 fields that need be defined for custom sniffers.
4251 The frame base sniffer is much simpler. It is a @code{@w{struct
4252 frame_base}}, which refers to the corresponding @code{frame_unwind}
4253 struct and whose fields refer to functions yielding various addresses
4256 @cindex @code{frame_base}
4260 const struct frame_unwind *unwind;
4261 frame_this_base_ftype *this_base;
4262 frame_this_locals_ftype *this_locals;
4263 frame_this_args_ftype *this_args;
4267 All the functions referred to take a pointer to the NEXT frame as
4268 argument. The function referred to by @code{this_base} returns the
4269 base address of THIS frame, the function referred to by
4270 @code{this_locals} returns the base address of local variables in THIS
4271 frame and the function referred to by @code{this_args} returns the
4272 base address of the function arguments in this frame.
4274 As described above, the base address of a frame is the address
4275 immediately before the start of the NEXT frame. For a falling
4276 stack, this is the lowest address in the frame and for a rising stack
4277 it is the highest address in the frame. For most architectures the
4278 same address is also the base address for local variables and
4279 arguments, in which case the same function can be used for all three
4280 entries@footnote{It is worth noting that if it cannot be determined in any
4281 other way (for example by there being a register with the name
4282 @code{"fp"}), then the result of the @code{this_base} function will be
4283 used as the value of the frame pointer variable @kbd{$fp} in
4284 @value{GDBN}. This is very often not correct (for example with the
4285 OpenRISC 1000, this value is the stack pointer, @kbd{$sp}). In this
4286 case a register (raw or pseudo) with the name @code{"fp"} should be
4287 defined. It will be used in preference as the value of @kbd{$fp}.}.
4289 @node Inferior Call Setup
4290 @section Inferior Call Setup
4291 @cindex calls to the inferior
4294 * About Dummy Frames::
4295 * Functions Creating Dummy Frames::
4298 @node About Dummy Frames
4299 @subsection About Dummy Frames
4300 @cindex dummy frames
4302 @value{GDBN} can call functions in the target code (for example by
4303 using the @kbd{call} or @kbd{print} commands). These functions may be
4304 breakpointed, and it is essential that if a function does hit a
4305 breakpoint, commands like @kbd{backtrace} work correctly.
4307 This is achieved by making the stack look as though the function had
4308 been called from the point where @value{GDBN} had previously stopped.
4309 This requires that @value{GDBN} can set up stack frames appropriate for
4310 such function calls.
4312 @node Functions Creating Dummy Frames
4313 @subsection Functions Creating Dummy Frames
4315 The following functions provide the functionality to set up such
4316 @dfn{dummy} stack frames.
4318 @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})
4320 This function sets up a dummy stack frame for the function about to be
4321 called. @code{push_dummy_call} is given the arguments to be passed
4322 and must copy them into registers or push them on to the stack as
4323 appropriate for the ABI.
4325 @var{function} is a pointer to the function
4326 that will be called and @var{regcache} the register cache from which
4327 values should be obtained. @var{bp_addr} is the address to which the
4328 function should return (which is breakpointed, so @value{GDBN} can
4329 regain control, hence the name). @var{nargs} is the number of
4330 arguments to pass and @var{args} an array containing the argument
4331 values. @var{struct_return} is non-zero (true) if the function returns
4332 a structure, and if so @var{struct_addr} is the address in which the
4333 structure should be returned.
4335 After calling this function, @value{GDBN} will pass control to the
4336 target at the address of the function, which will find the stack and
4337 registers set up just as expected.
4339 The default value of this function is @code{NULL} (undefined). If the
4340 function is not defined, then @value{GDBN} will not allow the user to
4341 call functions within the target being debugged.
4345 @deftypefn {Architecture Function} {struct frame_id} unwind_dummy_id (struct gdbarch *@var{gdbarch}, struct frame_info *@var{next_frame})
4347 This is the inverse of @code{push_dummy_call} which restores the stack
4348 pointer and program counter after a call to evaluate a function using
4349 a dummy stack frame. The result is a @code{@w{struct frame_id}}, which
4350 contains the value of the stack pointer and program counter to be
4353 The NEXT frame pointer is provided as argument,
4354 @var{next_frame}. THIS frame is the frame of the dummy function,
4355 which can be unwound, to yield the required stack pointer and program
4356 counter from the PREVIOUS frame.
4358 The default value is @code{NULL} (undefined). If @code{push_dummy_call} is
4359 defined, then this function should also be defined.
4363 @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})
4365 If this function is not defined (its default value is @code{NULL}), a dummy
4366 call will use the entry point of the currently loaded code on the
4367 target as its return address. A temporary breakpoint will be set
4368 there, so the location must be writable and have room for a
4371 It is possible that this default is not suitable. It might not be
4372 writable (in ROM possibly), or the ABI might require code to be
4373 executed on return from a call to unwind the stack before the
4374 breakpoint is encountered.
4376 If either of these is the case, then push_dummy_code should be defined
4377 to push an instruction sequence onto the end of the stack to which the
4378 dummy call should return.
4380 The arguments are essentially the same as those to
4381 @code{push_dummy_call}. However the function is provided with the
4382 type of the function result, @var{value_type}, @var{bp_addr} is used
4383 to return a value (the address at which the breakpoint instruction
4384 should be inserted) and @var{real pc} is used to specify the resume
4385 address when starting the call sequence. The function should return
4386 the updated innermost stack address.
4389 @emph{Note:} This does require that code in the stack can be executed.
4390 Some Harvard architectures may not allow this.
4395 @node Adding support for debugging core files
4396 @section Adding support for debugging core files
4399 The prerequisite for adding core file support in @value{GDBN} is to have
4400 core file support in BFD.
4402 Once BFD support is available, writing the apropriate
4403 @code{regset_from_core_section} architecture function should be all
4404 that is needed in order to add support for core files in @value{GDBN}.
4406 @node Defining Other Architecture Features
4407 @section Defining Other Architecture Features
4409 This section describes other functions and values in @code{gdbarch},
4410 together with some useful macros, that you can use to define the
4411 target architecture.
4415 @item CORE_ADDR gdbarch_addr_bits_remove (@var{gdbarch}, @var{addr})
4416 @findex gdbarch_addr_bits_remove
4417 If a raw machine instruction address includes any bits that are not
4418 really part of the address, then this function is used to zero those bits in
4419 @var{addr}. This is only used for addresses of instructions, and even then not
4422 For example, the two low-order bits of the PC on the Hewlett-Packard PA
4423 2.0 architecture contain the privilege level of the corresponding
4424 instruction. Since instructions must always be aligned on four-byte
4425 boundaries, the processor masks out these bits to generate the actual
4426 address of the instruction. @code{gdbarch_addr_bits_remove} would then for
4427 example look like that:
4429 arch_addr_bits_remove (CORE_ADDR addr)
4431 return (addr &= ~0x3);
4435 @item int address_class_name_to_type_flags (@var{gdbarch}, @var{name}, @var{type_flags_ptr})
4436 @findex address_class_name_to_type_flags
4437 If @var{name} is a valid address class qualifier name, set the @code{int}
4438 referenced by @var{type_flags_ptr} to the mask representing the qualifier
4439 and return 1. If @var{name} is not a valid address class qualifier name,
4442 The value for @var{type_flags_ptr} should be one of
4443 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
4444 possibly some combination of these values or'd together.
4445 @xref{Target Architecture Definition, , Address Classes}.
4447 @item int address_class_name_to_type_flags_p (@var{gdbarch})
4448 @findex address_class_name_to_type_flags_p
4449 Predicate which indicates whether @code{address_class_name_to_type_flags}
4452 @item int gdbarch_address_class_type_flags (@var{gdbarch}, @var{byte_size}, @var{dwarf2_addr_class})
4453 @findex gdbarch_address_class_type_flags
4454 Given a pointers byte size (as described by the debug information) and
4455 the possible @code{DW_AT_address_class} value, return the type flags
4456 used by @value{GDBN} to represent this address class. The value
4457 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
4458 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
4459 values or'd together.
4460 @xref{Target Architecture Definition, , Address Classes}.
4462 @item int gdbarch_address_class_type_flags_p (@var{gdbarch})
4463 @findex gdbarch_address_class_type_flags_p
4464 Predicate which indicates whether @code{gdbarch_address_class_type_flags_p} has
4467 @item const char *gdbarch_address_class_type_flags_to_name (@var{gdbarch}, @var{type_flags})
4468 @findex gdbarch_address_class_type_flags_to_name
4469 Return the name of the address class qualifier associated with the type
4470 flags given by @var{type_flags}.
4472 @item int gdbarch_address_class_type_flags_to_name_p (@var{gdbarch})
4473 @findex gdbarch_address_class_type_flags_to_name_p
4474 Predicate which indicates whether @code{gdbarch_address_class_type_flags_to_name} has been defined.
4475 @xref{Target Architecture Definition, , Address Classes}.
4477 @item void gdbarch_address_to_pointer (@var{gdbarch}, @var{type}, @var{buf}, @var{addr})
4478 @findex gdbarch_address_to_pointer
4479 Store in @var{buf} a pointer of type @var{type} representing the address
4480 @var{addr}, in the appropriate format for the current architecture.
4481 This function may safely assume that @var{type} is either a pointer or a
4482 C@t{++} reference type.
4483 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
4485 @item int gdbarch_believe_pcc_promotion (@var{gdbarch})
4486 @findex gdbarch_believe_pcc_promotion
4487 Used to notify if the compiler promotes a @code{short} or @code{char}
4488 parameter to an @code{int}, but still reports the parameter as its
4489 original type, rather than the promoted type.
4491 @item gdbarch_bits_big_endian (@var{gdbarch})
4492 @findex gdbarch_bits_big_endian
4493 This is used if the numbering of bits in the targets does @strong{not} match
4494 the endianism of the target byte order. A value of 1 means that the bits
4495 are numbered in a big-endian bit order, 0 means little-endian.
4497 @item set_gdbarch_bits_big_endian (@var{gdbarch}, @var{bits_big_endian})
4498 @findex set_gdbarch_bits_big_endian
4499 Calling set_gdbarch_bits_big_endian with a value of 1 indicates that the
4500 bits in the target are numbered in a big-endian bit order, 0 indicates
4505 This is the character array initializer for the bit pattern to put into
4506 memory where a breakpoint is set. Although it's common to use a trap
4507 instruction for a breakpoint, it's not required; for instance, the bit
4508 pattern could be an invalid instruction. The breakpoint must be no
4509 longer than the shortest instruction of the architecture.
4511 @code{BREAKPOINT} has been deprecated in favor of
4512 @code{gdbarch_breakpoint_from_pc}.
4514 @item BIG_BREAKPOINT
4515 @itemx LITTLE_BREAKPOINT
4516 @findex LITTLE_BREAKPOINT
4517 @findex BIG_BREAKPOINT
4518 Similar to BREAKPOINT, but used for bi-endian targets.
4520 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
4521 favor of @code{gdbarch_breakpoint_from_pc}.
4523 @item const gdb_byte *gdbarch_breakpoint_from_pc (@var{gdbarch}, @var{pcptr}, @var{lenptr})
4524 @findex gdbarch_breakpoint_from_pc
4525 @anchor{gdbarch_breakpoint_from_pc} Use the program counter to determine the
4526 contents and size of a breakpoint instruction. It returns a pointer to
4527 a static string of bytes that encode a breakpoint instruction, stores the
4528 length of the string to @code{*@var{lenptr}}, and adjusts the program
4529 counter (if necessary) to point to the actual memory location where the
4530 breakpoint should be inserted. On input, the program counter
4531 (@code{*@var{pcptr}} is the encoded inferior's PC register. If software
4532 breakpoints are supported, the function sets this argument to the PC's
4533 plain address. If software breakpoints are not supported, the function
4534 returns NULL instead of the encoded breakpoint instruction.
4536 Although it is common to use a trap instruction for a breakpoint, it's
4537 not required; for instance, the bit pattern could be an invalid
4538 instruction. The breakpoint must be no longer than the shortest
4539 instruction of the architecture.
4541 Provided breakpoint bytes can be also used by @code{bp_loc_is_permanent} to
4542 detect permanent breakpoints. @code{gdbarch_breakpoint_from_pc} should return
4543 an unchanged memory copy if it was called for a location with permanent
4544 breakpoint as some architectures use breakpoint instructions containing
4545 arbitrary parameter value.
4547 Replaces all the other @var{BREAKPOINT} macros.
4549 @item int gdbarch_memory_insert_breakpoint (@var{gdbarch}, @var{bp_tgt})
4550 @itemx gdbarch_memory_remove_breakpoint (@var{gdbarch}, @var{bp_tgt})
4551 @findex gdbarch_memory_remove_breakpoint
4552 @findex gdbarch_memory_insert_breakpoint
4553 Insert or remove memory based breakpoints. Reasonable defaults
4554 (@code{default_memory_insert_breakpoint} and
4555 @code{default_memory_remove_breakpoint} respectively) have been
4556 provided so that it is not necessary to set these for most
4557 architectures. Architectures which may want to set
4558 @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
4559 conventional manner.
4561 It may also be desirable (from an efficiency standpoint) to define
4562 custom breakpoint insertion and removal routines if
4563 @code{gdbarch_breakpoint_from_pc} needs to read the target's memory for some
4566 @item CORE_ADDR gdbarch_adjust_breakpoint_address (@var{gdbarch}, @var{bpaddr})
4567 @findex gdbarch_adjust_breakpoint_address
4568 @cindex breakpoint address adjusted
4569 Given an address at which a breakpoint is desired, return a breakpoint
4570 address adjusted to account for architectural constraints on
4571 breakpoint placement. This method is not needed by most targets.
4573 The FR-V target (see @file{frv-tdep.c}) requires this method.
4574 The FR-V is a VLIW architecture in which a number of RISC-like
4575 instructions are grouped (packed) together into an aggregate
4576 instruction or instruction bundle. When the processor executes
4577 one of these bundles, the component instructions are executed
4580 In the course of optimization, the compiler may group instructions
4581 from distinct source statements into the same bundle. The line number
4582 information associated with one of the latter statements will likely
4583 refer to some instruction other than the first one in the bundle. So,
4584 if the user attempts to place a breakpoint on one of these latter
4585 statements, @value{GDBN} must be careful to @emph{not} place the break
4586 instruction on any instruction other than the first one in the bundle.
4587 (Remember though that the instructions within a bundle execute
4588 in parallel, so the @emph{first} instruction is the instruction
4589 at the lowest address and has nothing to do with execution order.)
4591 The FR-V's @code{gdbarch_adjust_breakpoint_address} method will adjust a
4592 breakpoint's address by scanning backwards for the beginning of
4593 the bundle, returning the address of the bundle.
4595 Since the adjustment of a breakpoint may significantly alter a user's
4596 expectation, @value{GDBN} prints a warning when an adjusted breakpoint
4597 is initially set and each time that that breakpoint is hit.
4599 @item int gdbarch_call_dummy_location (@var{gdbarch})
4600 @findex gdbarch_call_dummy_location
4601 See the file @file{inferior.h}.
4603 This method has been replaced by @code{gdbarch_push_dummy_code}
4604 (@pxref{gdbarch_push_dummy_code}).
4606 @item int gdbarch_cannot_fetch_register (@var{gdbarch}, @var{regum})
4607 @findex gdbarch_cannot_fetch_register
4608 This function should return nonzero if @var{regno} cannot be fetched
4609 from an inferior process.
4611 @item int gdbarch_cannot_store_register (@var{gdbarch}, @var{regnum})
4612 @findex gdbarch_cannot_store_register
4613 This function should return nonzero if @var{regno} should not be
4614 written to the target. This is often the case for program counters,
4615 status words, and other special registers. This function returns 0 as
4616 default so that @value{GDBN} will assume that all registers may be written.
4618 @item int gdbarch_convert_register_p (@var{gdbarch}, @var{regnum}, struct type *@var{type})
4619 @findex gdbarch_convert_register_p
4620 Return non-zero if register @var{regnum} represents data values of type
4621 @var{type} in a non-standard form.
4622 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4624 @item int gdbarch_fp0_regnum (@var{gdbarch})
4625 @findex gdbarch_fp0_regnum
4626 This function returns the number of the first floating point register,
4627 if the machine has such registers. Otherwise, it returns -1.
4629 @item CORE_ADDR gdbarch_decr_pc_after_break (@var{gdbarch})
4630 @findex gdbarch_decr_pc_after_break
4631 This function shall return the amount by which to decrement the PC after the
4632 program encounters a breakpoint. This is often the number of bytes in
4633 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
4635 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
4636 @findex DISABLE_UNSETTABLE_BREAK
4637 If defined, this should evaluate to 1 if @var{addr} is in a shared
4638 library in which breakpoints cannot be set and so should be disabled.
4640 @item int gdbarch_dwarf2_reg_to_regnum (@var{gdbarch}, @var{dwarf2_regnr})
4641 @findex gdbarch_dwarf2_reg_to_regnum
4642 Convert DWARF2 register number @var{dwarf2_regnr} into @value{GDBN} regnum.
4643 If not defined, no conversion will be performed.
4645 @item int gdbarch_ecoff_reg_to_regnum (@var{gdbarch}, @var{ecoff_regnr})
4646 @findex gdbarch_ecoff_reg_to_regnum
4647 Convert ECOFF register number @var{ecoff_regnr} into @value{GDBN} regnum. If
4648 not defined, no conversion will be performed.
4650 @item GCC_COMPILED_FLAG_SYMBOL
4651 @itemx GCC2_COMPILED_FLAG_SYMBOL
4652 @findex GCC2_COMPILED_FLAG_SYMBOL
4653 @findex GCC_COMPILED_FLAG_SYMBOL
4654 If defined, these are the names of the symbols that @value{GDBN} will
4655 look for to detect that GCC compiled the file. The default symbols
4656 are @code{gcc_compiled.} and @code{gcc2_compiled.},
4657 respectively. (Currently only defined for the Delta 68.)
4659 @item gdbarch_get_longjmp_target
4660 @findex gdbarch_get_longjmp_target
4661 This function determines the target PC address that @code{longjmp}
4662 will jump to, assuming that we have just stopped at a @code{longjmp}
4663 breakpoint. It takes a @code{CORE_ADDR *} as argument, and stores the
4664 target PC value through this pointer. It examines the current state
4665 of the machine as needed, typically by using a manually-determined
4666 offset into the @code{jmp_buf}. (While we might like to get the offset
4667 from the target's @file{jmpbuf.h}, that header file cannot be assumed
4668 to be available when building a cross-debugger.)
4670 @item DEPRECATED_IBM6000_TARGET
4671 @findex DEPRECATED_IBM6000_TARGET
4672 Shows that we are configured for an IBM RS/6000 system. This
4673 conditional should be eliminated (FIXME) and replaced by
4674 feature-specific macros. It was introduced in haste and we are
4675 repenting at leisure.
4677 @item I386_USE_GENERIC_WATCHPOINTS
4678 An x86-based target can define this to use the generic x86 watchpoint
4679 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4681 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{addr})
4682 @findex gdbarch_in_function_epilogue_p
4683 Returns non-zero if the given @var{addr} is in the epilogue of a function.
4684 The epilogue of a function is defined as the part of a function where
4685 the stack frame of the function already has been destroyed up to the
4686 final `return from function call' instruction.
4688 @item int gdbarch_in_solib_return_trampoline (@var{gdbarch}, @var{pc}, @var{name})
4689 @findex gdbarch_in_solib_return_trampoline
4690 Define this function to return nonzero if the program is stopped in the
4691 trampoline that returns from a shared library.
4693 @item target_so_ops.in_dynsym_resolve_code (@var{pc})
4694 @findex in_dynsym_resolve_code
4695 Define this to return nonzero if the program is stopped in the
4698 @item SKIP_SOLIB_RESOLVER (@var{pc})
4699 @findex SKIP_SOLIB_RESOLVER
4700 Define this to evaluate to the (nonzero) address at which execution
4701 should continue to get past the dynamic linker's symbol resolution
4702 function. A zero value indicates that it is not important or necessary
4703 to set a breakpoint to get through the dynamic linker and that single
4704 stepping will suffice.
4706 @item CORE_ADDR gdbarch_integer_to_address (@var{gdbarch}, @var{type}, @var{buf})
4707 @findex gdbarch_integer_to_address
4708 @cindex converting integers to addresses
4709 Define this when the architecture needs to handle non-pointer to address
4710 conversions specially. Converts that value to an address according to
4711 the current architectures conventions.
4713 @emph{Pragmatics: When the user copies a well defined expression from
4714 their source code and passes it, as a parameter, to @value{GDBN}'s
4715 @code{print} command, they should get the same value as would have been
4716 computed by the target program. Any deviation from this rule can cause
4717 major confusion and annoyance, and needs to be justified carefully. In
4718 other words, @value{GDBN} doesn't really have the freedom to do these
4719 conversions in clever and useful ways. It has, however, been pointed
4720 out that users aren't complaining about how @value{GDBN} casts integers
4721 to pointers; they are complaining that they can't take an address from a
4722 disassembly listing and give it to @code{x/i}. Adding an architecture
4723 method like @code{gdbarch_integer_to_address} certainly makes it possible for
4724 @value{GDBN} to ``get it right'' in all circumstances.}
4726 @xref{Target Architecture Definition, , Pointers Are Not Always
4729 @item CORE_ADDR gdbarch_pointer_to_address (@var{gdbarch}, @var{type}, @var{buf})
4730 @findex gdbarch_pointer_to_address
4731 Assume that @var{buf} holds a pointer of type @var{type}, in the
4732 appropriate format for the current architecture. Return the byte
4733 address the pointer refers to.
4734 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
4736 @item void gdbarch_register_to_value(@var{gdbarch}, @var{frame}, @var{regnum}, @var{type}, @var{fur})
4737 @findex gdbarch_register_to_value
4738 Convert the raw contents of register @var{regnum} into a value of type
4740 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4742 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
4743 @findex REGISTER_CONVERT_TO_VIRTUAL
4744 Convert the value of register @var{reg} from its raw form to its virtual
4746 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
4748 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
4749 @findex REGISTER_CONVERT_TO_RAW
4750 Convert the value of register @var{reg} from its virtual form to its raw
4752 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
4754 @item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size})
4755 @findex regset_from_core_section
4756 Return the appropriate register set for a core file section with name
4757 @var{sect_name} and size @var{sect_size}.
4759 @item SOFTWARE_SINGLE_STEP_P()
4760 @findex SOFTWARE_SINGLE_STEP_P
4761 Define this as 1 if the target does not have a hardware single-step
4762 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
4764 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p})
4765 @findex SOFTWARE_SINGLE_STEP
4766 A function that inserts or removes (depending on
4767 @var{insert_breakpoints_p}) breakpoints at each possible destinations of
4768 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
4771 @item set_gdbarch_sofun_address_maybe_missing (@var{gdbarch}, @var{set})
4772 @findex set_gdbarch_sofun_address_maybe_missing
4773 Somebody clever observed that, the more actual addresses you have in the
4774 debug information, the more time the linker has to spend relocating
4775 them. So whenever there's some other way the debugger could find the
4776 address it needs, you should omit it from the debug info, to make
4779 Calling @code{set_gdbarch_sofun_address_maybe_missing} with a non-zero
4780 argument @var{set} indicates that a particular set of hacks of this sort
4781 are in use, affecting @code{N_SO} and @code{N_FUN} entries in stabs-format
4782 debugging information. @code{N_SO} stabs mark the beginning and ending
4783 addresses of compilation units in the text segment. @code{N_FUN} stabs
4784 mark the starts and ends of functions.
4786 In this case, @value{GDBN} assumes two things:
4790 @code{N_FUN} stabs have an address of zero. Instead of using those
4791 addresses, you should find the address where the function starts by
4792 taking the function name from the stab, and then looking that up in the
4793 minsyms (the linker/assembler symbol table). In other words, the stab
4794 has the name, and the linker/assembler symbol table is the only place
4795 that carries the address.
4798 @code{N_SO} stabs have an address of zero, too. You just look at the
4799 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab, and
4800 guess the starting and ending addresses of the compilation unit from them.
4803 @item int gdbarch_stabs_argument_has_addr (@var{gdbarch}, @var{type})
4804 @findex gdbarch_stabs_argument_has_addr
4805 @anchor{gdbarch_stabs_argument_has_addr} Define this function to return
4806 nonzero if a function argument of type @var{type} is passed by reference
4809 @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})
4810 @findex gdbarch_push_dummy_call
4811 @anchor{gdbarch_push_dummy_call} Define this to push the dummy frame's call to
4812 the inferior function onto the stack. In addition to pushing @var{nargs}, the
4813 code should push @var{struct_addr} (when @var{struct_return} is non-zero), and
4814 the return address (@var{bp_addr}, in inferior's PC register encoding).
4816 @var{function} is a pointer to a @code{struct value}; on architectures that use
4817 function descriptors, this contains the function descriptor value.
4819 Returns the updated top-of-stack pointer.
4821 @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})
4822 @findex gdbarch_push_dummy_code
4823 @anchor{gdbarch_push_dummy_code} Given a stack based call dummy, push the
4824 instruction sequence (including space for a breakpoint) to which the
4825 called function should return.
4827 Set @var{bp_addr} to the address at which the breakpoint instruction
4828 should be inserted (in inferior's PC register encoding), @var{real_pc} to the
4829 resume address when starting the call sequence, and return the updated
4830 inner-most stack address.
4832 By default, the stack is grown sufficient to hold a frame-aligned
4833 (@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address
4834 reserved for that breakpoint (in inferior's PC register encoding), and
4835 @var{real_pc} set to @var{funaddr}.
4837 This method replaces @w{@code{gdbarch_call_dummy_location (@var{gdbarch})}}.
4839 @item int gdbarch_sdb_reg_to_regnum (@var{gdbarch}, @var{sdb_regnr})
4840 @findex gdbarch_sdb_reg_to_regnum
4841 Use this function to convert sdb register @var{sdb_regnr} into @value{GDBN}
4842 regnum. If not defined, no conversion will be done.
4844 @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})
4845 @findex gdbarch_return_value
4846 @anchor{gdbarch_return_value} Given a function with a return-value of
4847 type @var{rettype}, return which return-value convention that function
4850 @value{GDBN} currently recognizes two function return-value conventions:
4851 @code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found
4852 in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return
4853 value is found in memory and the address of that memory location is
4854 passed in as the function's first parameter.
4856 If the register convention is being used, and @var{writebuf} is
4857 non-@code{NULL}, also copy the return-value in @var{writebuf} into
4860 If the register convention is being used, and @var{readbuf} is
4861 non-@code{NULL}, also copy the return value from @var{regcache} into
4862 @var{readbuf} (@var{regcache} contains a copy of the registers from the
4863 just returned function).
4865 @emph{Maintainer note: This method replaces separate predicate, extract,
4866 store methods. By having only one method, the logic needed to determine
4867 the return-value convention need only be implemented in one place. If
4868 @value{GDBN} were written in an @sc{oo} language, this method would
4869 instead return an object that knew how to perform the register
4870 return-value extract and store.}
4872 @emph{Maintainer note: This method does not take a @var{gcc_p}
4873 parameter, and such a parameter should not be added. If an architecture
4874 that requires per-compiler or per-function information be identified,
4875 then the replacement of @var{rettype} with @code{struct value}
4876 @var{function} should be pursued.}
4878 @emph{Maintainer note: The @var{regcache} parameter limits this methods
4879 to the inner most frame. While replacing @var{regcache} with a
4880 @code{struct frame_info} @var{frame} parameter would remove that
4881 limitation there has yet to be a demonstrated need for such a change.}
4883 @item void gdbarch_skip_permanent_breakpoint (@var{gdbarch}, @var{regcache})
4884 @findex gdbarch_skip_permanent_breakpoint
4885 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
4886 steps over a breakpoint by removing it, stepping one instruction, and
4887 re-inserting the breakpoint. However, permanent breakpoints are
4888 hardwired into the inferior, and can't be removed, so this strategy
4889 doesn't work. Calling @code{gdbarch_skip_permanent_breakpoint} adjusts the
4890 processor's state so that execution will resume just after the breakpoint.
4891 This function does the right thing even when the breakpoint is in the delay slot
4892 of a branch or jump.
4894 @item CORE_ADDR gdbarch_skip_trampoline_code (@var{gdbarch}, @var{frame}, @var{pc})
4895 @findex gdbarch_skip_trampoline_code
4896 If the target machine has trampoline code that sits between callers and
4897 the functions being called, then define this function to return a new PC
4898 that is at the start of the real function.
4900 @item int gdbarch_deprecated_fp_regnum (@var{gdbarch})
4901 @findex gdbarch_deprecated_fp_regnum
4902 If the frame pointer is in a register, use this function to return the
4903 number of that register.
4905 @item int gdbarch_stab_reg_to_regnum (@var{gdbarch}, @var{stab_regnr})
4906 @findex gdbarch_stab_reg_to_regnum
4907 Use this function to convert stab register @var{stab_regnr} into @value{GDBN}
4908 regnum. If not defined, no conversion will be done.
4910 @item TARGET_CHAR_BIT
4911 @findex TARGET_CHAR_BIT
4912 Number of bits in a char; defaults to 8.
4914 @item int gdbarch_char_signed (@var{gdbarch})
4915 @findex gdbarch_char_signed
4916 Non-zero if @code{char} is normally signed on this architecture; zero if
4917 it should be unsigned.
4919 The ISO C standard requires the compiler to treat @code{char} as
4920 equivalent to either @code{signed char} or @code{unsigned char}; any
4921 character in the standard execution set is supposed to be positive.
4922 Most compilers treat @code{char} as signed, but @code{char} is unsigned
4923 on the IBM S/390, RS6000, and PowerPC targets.
4925 @item int gdbarch_double_bit (@var{gdbarch})
4926 @findex gdbarch_double_bit
4927 Number of bits in a double float; defaults to @w{@code{8 * TARGET_CHAR_BIT}}.
4929 @item int gdbarch_float_bit (@var{gdbarch})
4930 @findex gdbarch_float_bit
4931 Number of bits in a float; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4933 @item int gdbarch_int_bit (@var{gdbarch})
4934 @findex gdbarch_int_bit
4935 Number of bits in an integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4937 @item int gdbarch_long_bit (@var{gdbarch})
4938 @findex gdbarch_long_bit
4939 Number of bits in a long integer; defaults to @w{@code{4 * TARGET_CHAR_BIT}}.
4941 @item int gdbarch_long_double_bit (@var{gdbarch})
4942 @findex gdbarch_long_double_bit
4943 Number of bits in a long double float;
4944 defaults to @w{@code{2 * gdbarch_double_bit (@var{gdbarch})}}.
4946 @item int gdbarch_long_long_bit (@var{gdbarch})
4947 @findex gdbarch_long_long_bit
4948 Number of bits in a long long integer; defaults to
4949 @w{@code{2 * gdbarch_long_bit (@var{gdbarch})}}.
4951 @item int gdbarch_ptr_bit (@var{gdbarch})
4952 @findex gdbarch_ptr_bit
4953 Number of bits in a pointer; defaults to
4954 @w{@code{gdbarch_int_bit (@var{gdbarch})}}.
4956 @item int gdbarch_short_bit (@var{gdbarch})
4957 @findex gdbarch_short_bit
4958 Number of bits in a short integer; defaults to @w{@code{2 * TARGET_CHAR_BIT}}.
4960 @item void gdbarch_virtual_frame_pointer (@var{gdbarch}, @var{pc}, @var{frame_regnum}, @var{frame_offset})
4961 @findex gdbarch_virtual_frame_pointer
4962 Returns a @code{(@var{register}, @var{offset})} pair representing the virtual
4963 frame pointer in use at the code address @var{pc}. If virtual frame
4964 pointers are not used, a default definition simply returns
4965 @code{gdbarch_deprecated_fp_regnum} (or @code{gdbarch_sp_regnum}, if
4966 no frame pointer is defined), with an offset of zero.
4968 @c need to explain virtual frame pointers, they are recorded in agent
4969 @c expressions for tracepoints
4971 @item TARGET_HAS_HARDWARE_WATCHPOINTS
4972 If non-zero, the target has support for hardware-assisted
4973 watchpoints. @xref{Algorithms, watchpoints}, for more details and
4974 other related macros.
4976 @item int gdbarch_print_insn (@var{gdbarch}, @var{vma}, @var{info})
4977 @findex gdbarch_print_insn
4978 This is the function used by @value{GDBN} to print an assembly
4979 instruction. It prints the instruction at address @var{vma} in
4980 debugged memory and returns the length of the instruction, in bytes.
4981 This usually points to a function in the @code{opcodes} library
4982 (@pxref{Support Libraries, ,Opcodes}). @var{info} is a structure (of
4983 type @code{disassemble_info}) defined in the header file
4984 @file{include/dis-asm.h}, and used to pass information to the
4985 instruction decoding routine.
4987 @item frame_id gdbarch_dummy_id (@var{gdbarch}, @var{frame})
4988 @findex gdbarch_dummy_id
4989 @anchor{gdbarch_dummy_id} Given @var{frame} return a @w{@code{struct
4990 frame_id}} that uniquely identifies an inferior function call's dummy
4991 frame. The value returned must match the dummy frame stack value
4992 previously saved by @code{call_function_by_hand}.
4994 @item void gdbarch_value_to_register (@var{gdbarch}, @var{frame}, @var{type}, @var{buf})
4995 @findex gdbarch_value_to_register
4996 Convert a value of type @var{type} into the raw contents of a register.
4997 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
5001 Motorola M68K target conditionals.
5005 Define this to be the 4-bit location of the breakpoint trap vector. If
5006 not defined, it will default to @code{0xf}.
5008 @item REMOTE_BPT_VECTOR
5009 Defaults to @code{1}.
5013 @node Adding a New Target
5014 @section Adding a New Target
5016 @cindex adding a target
5017 The following files add a target to @value{GDBN}:
5020 @cindex target dependent files
5022 @item gdb/@var{ttt}-tdep.c
5023 Contains any miscellaneous code required for this target machine. On
5024 some machines it doesn't exist at all.
5026 @item gdb/@var{arch}-tdep.c
5027 @itemx gdb/@var{arch}-tdep.h
5028 This is required to describe the basic layout of the target machine's
5029 processor chip (registers, stack, etc.). It can be shared among many
5030 targets that use the same processor architecture.
5034 (Target header files such as
5035 @file{gdb/config/@var{arch}/tm-@var{ttt}.h},
5036 @file{gdb/config/@var{arch}/tm-@var{arch}.h}, and
5037 @file{config/tm-@var{os}.h} are no longer used.)
5039 @findex _initialize_@var{arch}_tdep
5040 A @value{GDBN} description for a new architecture, arch is created by
5041 defining a global function @code{_initialize_@var{arch}_tdep}, by
5042 convention in the source file @file{@var{arch}-tdep.c}. For
5043 example, in the case of the OpenRISC 1000, this function is called
5044 @code{_initialize_or1k_tdep} and is found in the file
5047 The object file resulting from compiling this source file, which will
5048 contain the implementation of the
5049 @code{_initialize_@var{arch}_tdep} function is specified in the
5050 @value{GDBN} @file{configure.tgt} file, which includes a large case
5051 statement pattern matching against the @code{--target} option of the
5052 @kbd{configure} script.
5055 @emph{Note:} If the architecture requires multiple source files, the
5056 corresponding binaries should be included in
5057 @file{configure.tgt}. However if there are header files, the
5058 dependencies on these will not be picked up from the entries in
5059 @file{configure.tgt}. The @file{Makefile.in} file will need extending to
5060 show these dependencies.
5063 @findex gdbarch_register
5064 A new struct gdbarch, defining the new architecture, is created within
5065 the @code{_initialize_@var{arch}_tdep} function by calling
5066 @code{gdbarch_register}:
5069 void gdbarch_register (enum bfd_architecture architecture,
5070 gdbarch_init_ftype *init_func,
5071 gdbarch_dump_tdep_ftype *tdep_dump_func);
5074 This function has been described fully in an earlier
5075 section. @xref{How an Architecture is Represented, , How an
5076 Architecture is Represented}.
5078 The new @code{@w{struct gdbarch}} should contain implementations of
5079 the necessary functions (described in the previous sections) to
5080 describe the basic layout of the target machine's processor chip
5081 (registers, stack, etc.). It can be shared among many targets that use
5082 the same processor architecture.
5084 @node Target Descriptions
5085 @chapter Target Descriptions
5086 @cindex target descriptions
5088 The target architecture definition (@pxref{Target Architecture Definition})
5089 contains @value{GDBN}'s hard-coded knowledge about an architecture. For
5090 some platforms, it is handy to have more flexible knowledge about a specific
5091 instance of the architecture---for instance, a processor or development board.
5092 @dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN}
5093 more about what their target supports, or for the target to tell @value{GDBN}
5096 For details on writing, automatically supplying, and manually selecting
5097 target descriptions, see @ref{Target Descriptions, , , gdb,
5098 Debugging with @value{GDBN}}. This section will cover some related
5099 topics about the @value{GDBN} internals.
5102 * Target Descriptions Implementation::
5103 * Adding Target Described Register Support::
5106 @node Target Descriptions Implementation
5107 @section Target Descriptions Implementation
5108 @cindex target descriptions, implementation
5110 Before @value{GDBN} connects to a new target, or runs a new program on
5111 an existing target, it discards any existing target description and
5112 reverts to a default gdbarch. Then, after connecting, it looks for a
5113 new target description by calling @code{target_find_description}.
5115 A description may come from a user specified file (XML), the remote
5116 @samp{qXfer:features:read} packet (also XML), or from any custom
5117 @code{to_read_description} routine in the target vector. For instance,
5118 the remote target supports guessing whether a MIPS target is 32-bit or
5119 64-bit based on the size of the @samp{g} packet.
5121 If any target description is found, @value{GDBN} creates a new gdbarch
5122 incorporating the description by calling @code{gdbarch_update_p}. Any
5123 @samp{<architecture>} element is handled first, to determine which
5124 architecture's gdbarch initialization routine is called to create the
5125 new architecture. Then the initialization routine is called, and has
5126 a chance to adjust the constructed architecture based on the contents
5127 of the target description. For instance, it can recognize any
5128 properties set by a @code{to_read_description} routine. Also
5129 see @ref{Adding Target Described Register Support}.
5131 @node Adding Target Described Register Support
5132 @section Adding Target Described Register Support
5133 @cindex target descriptions, adding register support
5135 Target descriptions can report additional registers specific to an
5136 instance of the target. But it takes a little work in the architecture
5137 specific routines to support this.
5139 A target description must either have no registers or a complete
5140 set---this avoids complexity in trying to merge standard registers
5141 with the target defined registers. It is the architecture's
5142 responsibility to validate that a description with registers has
5143 everything it needs. To keep architecture code simple, the same
5144 mechanism is used to assign fixed internal register numbers to
5147 If @code{tdesc_has_registers} returns 1, the description contains
5148 registers. The architecture's @code{gdbarch_init} routine should:
5153 Call @code{tdesc_data_alloc} to allocate storage, early, before
5154 searching for a matching gdbarch or allocating a new one.
5157 Use @code{tdesc_find_feature} to locate standard features by name.
5160 Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices}
5161 to locate the expected registers in the standard features.
5164 Return @code{NULL} if a required feature is missing, or if any standard
5165 feature is missing expected registers. This will produce a warning that
5166 the description was incomplete.
5169 Free the allocated data before returning, unless @code{tdesc_use_registers}
5173 Call @code{set_gdbarch_num_regs} as usual, with a number higher than any
5174 fixed number passed to @code{tdesc_numbered_register}.
5177 Call @code{tdesc_use_registers} after creating a new gdbarch, before
5182 After @code{tdesc_use_registers} has been called, the architecture's
5183 @code{register_name}, @code{register_type}, and @code{register_reggroup_p}
5184 routines will not be called; that information will be taken from
5185 the target description. @code{num_regs} may be increased to account
5186 for any additional registers in the description.
5188 Pseudo-registers require some extra care:
5193 Using @code{tdesc_numbered_register} allows the architecture to give
5194 constant register numbers to standard architectural registers, e.g.@:
5195 as an @code{enum} in @file{@var{arch}-tdep.h}. But because
5196 pseudo-registers are always numbered above @code{num_regs},
5197 which may be increased by the description, constant numbers
5198 can not be used for pseudos. They must be numbered relative to
5199 @code{num_regs} instead.
5202 The description will not describe pseudo-registers, so the
5203 architecture must call @code{set_tdesc_pseudo_register_name},
5204 @code{set_tdesc_pseudo_register_type}, and
5205 @code{set_tdesc_pseudo_register_reggroup_p} to supply routines
5206 describing pseudo registers. These routines will be passed
5207 internal register numbers, so the same routines used for the
5208 gdbarch equivalents are usually suitable.
5213 @node Target Vector Definition
5215 @chapter Target Vector Definition
5216 @cindex target vector
5218 The target vector defines the interface between @value{GDBN}'s
5219 abstract handling of target systems, and the nitty-gritty code that
5220 actually exercises control over a process or a serial port.
5221 @value{GDBN} includes some 30-40 different target vectors; however,
5222 each configuration of @value{GDBN} includes only a few of them.
5225 * Managing Execution State::
5226 * Existing Targets::
5229 @node Managing Execution State
5230 @section Managing Execution State
5231 @cindex execution state
5233 A target vector can be completely inactive (not pushed on the target
5234 stack), active but not running (pushed, but not connected to a fully
5235 manifested inferior), or completely active (pushed, with an accessible
5236 inferior). Most targets are only completely inactive or completely
5237 active, but some support persistent connections to a target even
5238 when the target has exited or not yet started.
5240 For example, connecting to the simulator using @code{target sim} does
5241 not create a running program. Neither registers nor memory are
5242 accessible until @code{run}. Similarly, after @code{kill}, the
5243 program can not continue executing. But in both cases @value{GDBN}
5244 remains connected to the simulator, and target-specific commands
5245 are directed to the simulator.
5247 A target which only supports complete activation should push itself
5248 onto the stack in its @code{to_open} routine (by calling
5249 @code{push_target}), and unpush itself from the stack in its
5250 @code{to_mourn_inferior} routine (by calling @code{unpush_target}).
5252 A target which supports both partial and complete activation should
5253 still call @code{push_target} in @code{to_open}, but not call
5254 @code{unpush_target} in @code{to_mourn_inferior}. Instead, it should
5255 call either @code{target_mark_running} or @code{target_mark_exited}
5256 in its @code{to_open}, depending on whether the target is fully active
5257 after connection. It should also call @code{target_mark_running} any
5258 time the inferior becomes fully active (e.g.@: in
5259 @code{to_create_inferior} and @code{to_attach}), and
5260 @code{target_mark_exited} when the inferior becomes inactive (in
5261 @code{to_mourn_inferior}). The target should also make sure to call
5262 @code{target_mourn_inferior} from its @code{to_kill}, to return the
5263 target to inactive state.
5265 @node Existing Targets
5266 @section Existing Targets
5269 @subsection File Targets
5271 Both executables and core files have target vectors.
5273 @subsection Standard Protocol and Remote Stubs
5275 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code that
5276 runs in the target system. @value{GDBN} provides several sample
5277 @dfn{stubs} that can be integrated into target programs or operating
5278 systems for this purpose; they are named @file{@var{cpu}-stub.c}. Many
5279 operating systems, embedded targets, emulators, and simulators already
5280 have a @value{GDBN} stub built into them, and maintenance of the remote
5281 protocol must be careful to preserve compatibility.
5283 The @value{GDBN} user's manual describes how to put such a stub into
5284 your target code. What follows is a discussion of integrating the
5285 SPARC stub into a complicated operating system (rather than a simple
5286 program), by Stu Grossman, the author of this stub.
5288 The trap handling code in the stub assumes the following upon entry to
5293 %l1 and %l2 contain pc and npc respectively at the time of the trap;
5299 you are in the correct trap window.
5302 As long as your trap handler can guarantee those conditions, then there
5303 is no reason why you shouldn't be able to ``share'' traps with the stub.
5304 The stub has no requirement that it be jumped to directly from the
5305 hardware trap vector. That is why it calls @code{exceptionHandler()},
5306 which is provided by the external environment. For instance, this could
5307 set up the hardware traps to actually execute code which calls the stub
5308 first, and then transfers to its own trap handler.
5310 For the most point, there probably won't be much of an issue with
5311 ``sharing'' traps, as the traps we use are usually not used by the kernel,
5312 and often indicate unrecoverable error conditions. Anyway, this is all
5313 controlled by a table, and is trivial to modify. The most important
5314 trap for us is for @code{ta 1}. Without that, we can't single step or
5315 do breakpoints. Everything else is unnecessary for the proper operation
5316 of the debugger/stub.
5318 From reading the stub, it's probably not obvious how breakpoints work.
5319 They are simply done by deposit/examine operations from @value{GDBN}.
5321 @subsection ROM Monitor Interface
5323 @subsection Custom Protocols
5325 @subsection Transport Layer
5327 @subsection Builtin Simulator
5330 @node Native Debugging
5332 @chapter Native Debugging
5333 @cindex native debugging
5335 Several files control @value{GDBN}'s configuration for native support:
5339 @item gdb/config/@var{arch}/@var{xyz}.mh
5340 Specifies Makefile fragments needed by a @emph{native} configuration on
5341 machine @var{xyz}. In particular, this lists the required
5342 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
5343 Also specifies the header file which describes native support on
5344 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
5345 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
5346 @samp{NAT_CDEPS}, @samp{NAT_GENERATED_FILES}, etc.; see @file{Makefile.in}.
5348 @emph{Maintainer's note: The @file{.mh} suffix is because this file
5349 originally contained @file{Makefile} fragments for hosting @value{GDBN}
5350 on machine @var{xyz}. While the file is no longer used for this
5351 purpose, the @file{.mh} suffix remains. Perhaps someone will
5352 eventually rename these fragments so that they have a @file{.mn}
5355 @item gdb/config/@var{arch}/nm-@var{xyz}.h
5356 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
5357 macro definitions describing the native system environment, such as
5358 child process control and core file support.
5360 @item gdb/@var{xyz}-nat.c
5361 Contains any miscellaneous C code required for this native support of
5362 this machine. On some machines it doesn't exist at all.
5365 There are some ``generic'' versions of routines that can be used by
5366 various systems. These can be customized in various ways by macros
5367 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
5368 the @var{xyz} host, you can just include the generic file's name (with
5369 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
5371 Otherwise, if your machine needs custom support routines, you will need
5372 to write routines that perform the same functions as the generic file.
5373 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
5374 into @code{NATDEPFILES}.
5378 This contains the @emph{target_ops vector} that supports Unix child
5379 processes on systems which use ptrace and wait to control the child.
5382 This contains the @emph{target_ops vector} that supports Unix child
5383 processes on systems which use /proc to control the child.
5386 This does the low-level grunge that uses Unix system calls to do a ``fork
5387 and exec'' to start up a child process.
5390 This is the low level interface to inferior processes for systems using
5391 the Unix @code{ptrace} call in a vanilla way.
5400 @section shared libraries
5402 @section Native Conditionals
5403 @cindex native conditionals
5405 When @value{GDBN} is configured and compiled, various macros are
5406 defined or left undefined, to control compilation when the host and
5407 target systems are the same. These macros should be defined (or left
5408 undefined) in @file{nm-@var{system}.h}.
5412 @item I386_USE_GENERIC_WATCHPOINTS
5413 An x86-based machine can define this to use the generic x86 watchpoint
5414 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
5416 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
5418 Define this to expand into an expression that will cause the symbols in
5419 @var{filename} to be added to @value{GDBN}'s symbol table. If
5420 @var{readsyms} is zero symbols are not read but any necessary low level
5421 processing for @var{filename} is still done.
5423 @item SOLIB_CREATE_INFERIOR_HOOK
5424 @findex SOLIB_CREATE_INFERIOR_HOOK
5425 Define this to expand into any shared-library-relocation code that you
5426 want to be run just after the child process has been forked.
5428 @item START_INFERIOR_TRAPS_EXPECTED
5429 @findex START_INFERIOR_TRAPS_EXPECTED
5430 When starting an inferior, @value{GDBN} normally expects to trap
5432 the shell execs, and once when the program itself execs. If the actual
5433 number of traps is something other than 2, then define this macro to
5434 expand into the number expected.
5438 @node Support Libraries
5440 @chapter Support Libraries
5445 BFD provides support for @value{GDBN} in several ways:
5448 @item identifying executable and core files
5449 BFD will identify a variety of file types, including a.out, coff, and
5450 several variants thereof, as well as several kinds of core files.
5452 @item access to sections of files
5453 BFD parses the file headers to determine the names, virtual addresses,
5454 sizes, and file locations of all the various named sections in files
5455 (such as the text section or the data section). @value{GDBN} simply
5456 calls BFD to read or write section @var{x} at byte offset @var{y} for
5459 @item specialized core file support
5460 BFD provides routines to determine the failing command name stored in a
5461 core file, the signal with which the program failed, and whether a core
5462 file matches (i.e.@: could be a core dump of) a particular executable
5465 @item locating the symbol information
5466 @value{GDBN} uses an internal interface of BFD to determine where to find the
5467 symbol information in an executable file or symbol-file. @value{GDBN} itself
5468 handles the reading of symbols, since BFD does not ``understand'' debug
5469 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
5474 @cindex opcodes library
5476 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
5477 library because it's also used in binutils, for @file{objdump}).
5480 @cindex readline library
5481 The @code{readline} library provides a set of functions for use by applications
5482 that allow users to edit command lines as they are typed in.
5485 @cindex @code{libiberty} library
5487 The @code{libiberty} library provides a set of functions and features
5488 that integrate and improve on functionality found in modern operating
5489 systems. Broadly speaking, such features can be divided into three
5490 groups: supplemental functions (functions that may be missing in some
5491 environments and operating systems), replacement functions (providing
5492 a uniform and easier to use interface for commonly used standard
5493 functions), and extensions (which provide additional functionality
5494 beyond standard functions).
5496 @value{GDBN} uses various features provided by the @code{libiberty}
5497 library, for instance the C@t{++} demangler, the @acronym{IEEE}
5498 floating format support functions, the input options parser
5499 @samp{getopt}, the @samp{obstack} extension, and other functions.
5501 @subsection @code{obstacks} in @value{GDBN}
5502 @cindex @code{obstacks}
5504 The obstack mechanism provides a convenient way to allocate and free
5505 chunks of memory. Each obstack is a pool of memory that is managed
5506 like a stack. Objects (of any nature, size and alignment) are
5507 allocated and freed in a @acronym{LIFO} fashion on an obstack (see
5508 @code{libiberty}'s documentation for a more detailed explanation of
5511 The most noticeable use of the @code{obstacks} in @value{GDBN} is in
5512 object files. There is an obstack associated with each internal
5513 representation of an object file. Lots of things get allocated on
5514 these @code{obstacks}: dictionary entries, blocks, blockvectors,
5515 symbols, minimal symbols, types, vectors of fundamental types, class
5516 fields of types, object files section lists, object files section
5517 offset lists, line tables, symbol tables, partial symbol tables,
5518 string tables, symbol table private data, macros tables, debug
5519 information sections and entries, import and export lists (som),
5520 unwind information (hppa), dwarf2 location expressions data. Plus
5521 various strings such as directory names strings, debug format strings,
5524 An essential and convenient property of all data on @code{obstacks} is
5525 that memory for it gets allocated (with @code{obstack_alloc}) at
5526 various times during a debugging session, but it is released all at
5527 once using the @code{obstack_free} function. The @code{obstack_free}
5528 function takes a pointer to where in the stack it must start the
5529 deletion from (much like the cleanup chains have a pointer to where to
5530 start the cleanups). Because of the stack like structure of the
5531 @code{obstacks}, this allows to free only a top portion of the
5532 obstack. There are a few instances in @value{GDBN} where such thing
5533 happens. Calls to @code{obstack_free} are done after some local data
5534 is allocated to the obstack. Only the local data is deleted from the
5535 obstack. Of course this assumes that nothing between the
5536 @code{obstack_alloc} and the @code{obstack_free} allocates anything
5537 else on the same obstack. For this reason it is best and safest to
5538 use temporary @code{obstacks}.
5540 Releasing the whole obstack is also not safe per se. It is safe only
5541 under the condition that we know the @code{obstacks} memory is no
5542 longer needed. In @value{GDBN} we get rid of the @code{obstacks} only
5543 when we get rid of the whole objfile(s), for instance upon reading a
5547 @cindex regular expressions library
5558 @item SIGN_EXTEND_CHAR
5560 @item SWITCH_ENUM_BUG
5569 @section Array Containers
5570 @cindex Array Containers
5573 Often it is necessary to manipulate a dynamic array of a set of
5574 objects. C forces some bookkeeping on this, which can get cumbersome
5575 and repetitive. The @file{vec.h} file contains macros for defining
5576 and using a typesafe vector type. The functions defined will be
5577 inlined when compiling, and so the abstraction cost should be zero.
5578 Domain checks are added to detect programming errors.
5580 An example use would be an array of symbols or section information.
5581 The array can be grown as symbols are read in (or preallocated), and
5582 the accessor macros provided keep care of all the necessary
5583 bookkeeping. Because the arrays are type safe, there is no danger of
5584 accidentally mixing up the contents. Think of these as C++ templates,
5585 but implemented in C.
5587 Because of the different behavior of structure objects, scalar objects
5588 and of pointers, there are three flavors of vector, one for each of
5589 these variants. Both the structure object and pointer variants pass
5590 pointers to objects around --- in the former case the pointers are
5591 stored into the vector and in the latter case the pointers are
5592 dereferenced and the objects copied into the vector. The scalar
5593 object variant is suitable for @code{int}-like objects, and the vector
5594 elements are returned by value.
5596 There are both @code{index} and @code{iterate} accessors. The iterator
5597 returns a boolean iteration condition and updates the iteration
5598 variable passed by reference. Because the iterator will be inlined,
5599 the address-of can be optimized away.
5601 The vectors are implemented using the trailing array idiom, thus they
5602 are not resizeable without changing the address of the vector object
5603 itself. This means you cannot have variables or fields of vector type
5604 --- always use a pointer to a vector. The one exception is the final
5605 field of a structure, which could be a vector type. You will have to
5606 use the @code{embedded_size} & @code{embedded_init} calls to create
5607 such objects, and they will probably not be resizeable (so don't use
5608 the @dfn{safe} allocation variants). The trailing array idiom is used
5609 (rather than a pointer to an array of data), because, if we allow
5610 @code{NULL} to also represent an empty vector, empty vectors occupy
5611 minimal space in the structure containing them.
5613 Each operation that increases the number of active elements is
5614 available in @dfn{quick} and @dfn{safe} variants. The former presumes
5615 that there is sufficient allocated space for the operation to succeed
5616 (it dies if there is not). The latter will reallocate the vector, if
5617 needed. Reallocation causes an exponential increase in vector size.
5618 If you know you will be adding N elements, it would be more efficient
5619 to use the reserve operation before adding the elements with the
5620 @dfn{quick} operation. This will ensure there are at least as many
5621 elements as you ask for, it will exponentially increase if there are
5622 too few spare slots. If you want reserve a specific number of slots,
5623 but do not want the exponential increase (for instance, you know this
5624 is the last allocation), use a negative number for reservation. You
5625 can also create a vector of a specific size from the get go.
5627 You should prefer the push and pop operations, as they append and
5628 remove from the end of the vector. If you need to remove several items
5629 in one go, use the truncate operation. The insert and remove
5630 operations allow you to change elements in the middle of the vector.
5631 There are two remove operations, one which preserves the element
5632 ordering @code{ordered_remove}, and one which does not
5633 @code{unordered_remove}. The latter function copies the end element
5634 into the removed slot, rather than invoke a memmove operation. The
5635 @code{lower_bound} function will determine where to place an item in
5636 the array using insert that will maintain sorted order.
5638 If you need to directly manipulate a vector, then the @code{address}
5639 accessor will return the address of the start of the vector. Also the
5640 @code{space} predicate will tell you whether there is spare capacity in the
5641 vector. You will not normally need to use these two functions.
5643 Vector types are defined using a
5644 @code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector
5645 type are declared using a @code{VEC(@var{typename})} macro. The
5646 characters @code{O}, @code{P} and @code{I} indicate whether
5647 @var{typename} is an object (@code{O}), pointer (@code{P}) or integral
5648 (@code{I}) type. Be careful to pick the correct one, as you'll get an
5649 awkward and inefficient API if you use the wrong one. There is a
5650 check, which results in a compile-time warning, for the @code{P} and
5651 @code{I} versions, but there is no check for the @code{O} versions, as
5652 that is not possible in plain C.
5654 An example of their use would be,
5657 DEF_VEC_P(tree); // non-managed tree vector.
5660 VEC(tree) *v; // A (pointer to) a vector of tree pointers.
5663 struct my_struct *s;
5665 if (VEC_length(tree, s->v)) @{ we have some contents @}
5666 VEC_safe_push(tree, s->v, decl); // append some decl onto the end
5667 for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
5668 @{ do something with elt @}
5672 The @file{vec.h} file provides details on how to invoke the various
5673 accessors provided. They are enumerated here:
5677 Return the number of items in the array,
5680 Return true if the array has no elements.
5684 Return the last or arbitrary item in the array.
5687 Access an array element and indicate whether the array has been
5692 Create and destroy an array.
5694 @item VEC_embedded_size
5695 @itemx VEC_embedded_init
5696 Helpers for embedding an array as the final element of another struct.
5702 Return the amount of free space in an array.
5705 Ensure a certain amount of free space.
5707 @item VEC_quick_push
5708 @itemx VEC_safe_push
5709 Append to an array, either assuming the space is available, or making
5713 Remove the last item from an array.
5716 Remove several items from the end of an array.
5719 Add several items to the end of an array.
5722 Overwrite an item in the array.
5724 @item VEC_quick_insert
5725 @itemx VEC_safe_insert
5726 Insert an item into the middle of the array. Either the space must
5727 already exist, or the space is created.
5729 @item VEC_ordered_remove
5730 @itemx VEC_unordered_remove
5731 Remove an item from the array, preserving order or not.
5733 @item VEC_block_remove
5734 Remove a set of items from the array.
5737 Provide the address of the first element.
5739 @item VEC_lower_bound
5740 Binary search the array.
5746 @node Coding Standards
5748 @chapter Coding Standards
5749 @cindex coding standards
5751 @section @value{GDBN} C Coding Standards
5753 @value{GDBN} follows the GNU coding standards, as described in
5754 @file{etc/standards.texi}. This file is also available for anonymous
5755 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
5756 of the standard; in general, when the GNU standard recommends a practice
5757 but does not require it, @value{GDBN} requires it.
5759 @value{GDBN} follows an additional set of coding standards specific to
5760 @value{GDBN}, as described in the following sections.
5764 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
5767 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
5769 @subsection Formatting
5771 @cindex source code formatting
5772 The standard GNU recommendations for formatting must be followed
5773 strictly. Any @value{GDBN}-specific deviation from GNU
5774 recomendations is described below.
5776 A function declaration should not have its name in column zero. A
5777 function definition should have its name in column zero.
5781 static void foo (void);
5789 @emph{Pragmatics: This simplifies scripting. Function definitions can
5790 be found using @samp{^function-name}.}
5792 There must be a space between a function or macro name and the opening
5793 parenthesis of its argument list (except for macro definitions, as
5794 required by C). There must not be a space after an open paren/bracket
5795 or before a close paren/bracket.
5797 While additional whitespace is generally helpful for reading, do not use
5798 more than one blank line to separate blocks, and avoid adding whitespace
5799 after the end of a program line (as of 1/99, some 600 lines had
5800 whitespace after the semicolon). Excess whitespace causes difficulties
5801 for @code{diff} and @code{patch} utilities.
5803 Pointers are declared using the traditional K&R C style:
5817 In addition, whitespace around casts and unary operators should follow
5818 the following guidelines:
5820 @multitable @columnfractions .2 .2 .8
5821 @item Use... @tab ...instead of @tab
5830 @item @code{(foo) x}
5835 @tab (pointer dereference)
5838 Any two or more lines in code should be wrapped in braces, even if
5839 they are comments, as they look like separate statements:
5844 /* Return success. */
5854 /* Return success. */
5858 @subsection Comments
5860 @cindex comment formatting
5861 The standard GNU requirements on comments must be followed strictly.
5863 Block comments must appear in the following form, with no @code{/*}- or
5864 @code{*/}-only lines, and no leading @code{*}:
5867 /* Wait for control to return from inferior to debugger. If inferior
5868 gets a signal, we may decide to start it up again instead of
5869 returning. That is why there is a loop in this function. When
5870 this function actually returns it means the inferior should be left
5871 stopped and @value{GDBN} should read more commands. */
5874 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5875 comment works correctly, and @kbd{M-q} fills the block consistently.)
5877 Put a blank line between the block comments preceding function or
5878 variable definitions, and the definition itself.
5880 In general, put function-body comments on lines by themselves, rather
5881 than trying to fit them into the 20 characters left at the end of a
5882 line, since either the comment or the code will inevitably get longer
5883 than will fit, and then somebody will have to move it anyhow.
5887 @cindex C data types
5888 Code must not depend on the sizes of C data types, the format of the
5889 host's floating point numbers, the alignment of anything, or the order
5890 of evaluation of expressions.
5892 @cindex function usage
5893 Use functions freely. There are only a handful of compute-bound areas
5894 in @value{GDBN} that might be affected by the overhead of a function
5895 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5896 limited by the target interface (whether serial line or system call).
5898 However, use functions with moderation. A thousand one-line functions
5899 are just as hard to understand as a single thousand-line function.
5901 @emph{Macros are bad, M'kay.}
5902 (But if you have to use a macro, make sure that the macro arguments are
5903 protected with parentheses.)
5907 Declarations like @samp{struct foo *} should be used in preference to
5908 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5910 @subsection Function Prototypes
5911 @cindex function prototypes
5913 Prototypes must be used when both @emph{declaring} and @emph{defining}
5914 a function. Prototypes for @value{GDBN} functions must include both the
5915 argument type and name, with the name matching that used in the actual
5916 function definition.
5918 All external functions should have a declaration in a header file that
5919 callers include, except for @code{_initialize_*} functions, which must
5920 be external so that @file{init.c} construction works, but shouldn't be
5921 visible to random source files.
5923 Where a source file needs a forward declaration of a static function,
5924 that declaration must appear in a block near the top of the source file.
5926 @subsection File Names
5928 Any file used when building the core of @value{GDBN} must be in lower
5929 case. Any file used when building the core of @value{GDBN} must be 8.3
5930 unique. These requirements apply to both source and generated files.
5932 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5933 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5934 is introduced to the build process both @file{Makefile.in} and
5935 @file{configure.in} need to be modified accordingly. Compare the
5936 convoluted conversion process needed to transform @file{COPYING} into
5937 @file{copying.c} with the conversion needed to transform
5938 @file{version.in} into @file{version.c}.}
5940 Any file non 8.3 compliant file (that is not used when building the core
5941 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5943 @emph{Pragmatics: This is clearly a compromise.}
5945 When @value{GDBN} has a local version of a system header file (ex
5946 @file{string.h}) the file name based on the POSIX header prefixed with
5947 @file{gdb_} (@file{gdb_string.h}). These headers should be relatively
5948 independent: they should use only macros defined by @file{configure},
5949 the compiler, or the host; they should include only system headers; they
5950 should refer only to system types. They may be shared between multiple
5951 programs, e.g.@: @value{GDBN} and @sc{gdbserver}.
5953 For other files @samp{-} is used as the separator.
5955 @subsection Include Files
5957 A @file{.c} file should include @file{defs.h} first.
5959 A @file{.c} file should directly include the @code{.h} file of every
5960 declaration and/or definition it directly refers to. It cannot rely on
5963 A @file{.h} file should directly include the @code{.h} file of every
5964 declaration and/or definition it directly refers to. It cannot rely on
5965 indirect inclusion. Exception: The file @file{defs.h} does not need to
5966 be directly included.
5968 An external declaration should only appear in one include file.
5970 An external declaration should never appear in a @code{.c} file.
5971 Exception: a declaration for the @code{_initialize} function that
5972 pacifies @option{-Wmissing-declaration}.
5974 A @code{typedef} definition should only appear in one include file.
5976 An opaque @code{struct} declaration can appear in multiple @file{.h}
5977 files. Where possible, a @file{.h} file should use an opaque
5978 @code{struct} declaration instead of an include.
5980 All @file{.h} files should be wrapped in:
5983 #ifndef INCLUDE_FILE_NAME_H
5984 #define INCLUDE_FILE_NAME_H
5989 @section @value{GDBN} Python Coding Standards
5991 @value{GDBN} follows the published @code{Python} coding standards in
5992 @uref{http://www.python.org/dev/peps/pep-0008/, @code{PEP008}}.
5994 In addition, the guidelines in the
5995 @uref{http://google-styleguide.googlecode.com/svn/trunk/pyguide.html,
5996 Google Python Style Guide} are also followed where they do not
5997 conflict with @code{PEP008}.
5999 @subsection @value{GDBN}-specific exceptions
6001 There are a few exceptions to the published standards.
6002 They exist mainly for consistency with the @code{C} standards.
6004 @c It is expected that there are a few more exceptions,
6005 @c so we use itemize here.
6010 Use @code{FIXME} instead of @code{TODO}.
6014 @node Misc Guidelines
6016 @chapter Misc Guidelines
6018 This chapter covers topics that are lower-level than the major
6019 algorithms of @value{GDBN}.
6024 Cleanups are a structured way to deal with things that need to be done
6027 When your code does something (e.g., @code{xmalloc} some memory, or
6028 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
6029 the memory or @code{close} the file), it can make a cleanup. The
6030 cleanup will be done at some future point: when the command is finished
6031 and control returns to the top level; when an error occurs and the stack
6032 is unwound; or when your code decides it's time to explicitly perform
6033 cleanups. Alternatively you can elect to discard the cleanups you
6039 @item struct cleanup *@var{old_chain};
6040 Declare a variable which will hold a cleanup chain handle.
6042 @findex make_cleanup
6043 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
6044 Make a cleanup which will cause @var{function} to be called with
6045 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
6046 handle that can later be passed to @code{do_cleanups} or
6047 @code{discard_cleanups}. Unless you are going to call
6048 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
6049 from @code{make_cleanup}.
6052 @item do_cleanups (@var{old_chain});
6053 Do all cleanups added to the chain since the corresponding
6054 @code{make_cleanup} call was made.
6056 @findex discard_cleanups
6057 @item discard_cleanups (@var{old_chain});
6058 Same as @code{do_cleanups} except that it just removes the cleanups from
6059 the chain and does not call the specified functions.
6062 Cleanups are implemented as a chain. The handle returned by
6063 @code{make_cleanups} includes the cleanup passed to the call and any
6064 later cleanups appended to the chain (but not yet discarded or
6068 make_cleanup (a, 0);
6070 struct cleanup *old = make_cleanup (b, 0);
6078 will call @code{c()} and @code{b()} but will not call @code{a()}. The
6079 cleanup that calls @code{a()} will remain in the cleanup chain, and will
6080 be done later unless otherwise discarded.@refill
6082 Your function should explicitly do or discard the cleanups it creates.
6083 Failing to do this leads to non-deterministic behavior since the caller
6084 will arbitrarily do or discard your functions cleanups. This need leads
6085 to two common cleanup styles.
6087 The first style is try/finally. Before it exits, your code-block calls
6088 @code{do_cleanups} with the old cleanup chain and thus ensures that your
6089 code-block's cleanups are always performed. For instance, the following
6090 code-segment avoids a memory leak problem (even when @code{error} is
6091 called and a forced stack unwind occurs) by ensuring that the
6092 @code{xfree} will always be called:
6095 struct cleanup *old = make_cleanup (null_cleanup, 0);
6096 data = xmalloc (sizeof blah);
6097 make_cleanup (xfree, data);
6102 The second style is try/except. Before it exits, your code-block calls
6103 @code{discard_cleanups} with the old cleanup chain and thus ensures that
6104 any created cleanups are not performed. For instance, the following
6105 code segment, ensures that the file will be closed but only if there is
6109 FILE *file = fopen ("afile", "r");
6110 struct cleanup *old = make_cleanup (close_file, file);
6112 discard_cleanups (old);
6116 Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify
6117 that they ``should not be called when cleanups are not in place''. This
6118 means that any actions you need to reverse in the case of an error or
6119 interruption must be on the cleanup chain before you call these
6120 functions, since they might never return to your code (they
6121 @samp{longjmp} instead).
6123 @section Per-architecture module data
6124 @cindex per-architecture module data
6125 @cindex multi-arch data
6126 @cindex data-pointer, per-architecture/per-module
6128 The multi-arch framework includes a mechanism for adding module
6129 specific per-architecture data-pointers to the @code{struct gdbarch}
6130 architecture object.
6132 A module registers one or more per-architecture data-pointers using:
6134 @deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init})
6135 @var{pre_init} is used to, on-demand, allocate an initial value for a
6136 per-architecture data-pointer using the architecture's obstack (passed
6137 in as a parameter). Since @var{pre_init} can be called during
6138 architecture creation, it is not parameterized with the architecture.
6139 and must not call modules that use per-architecture data.
6142 @deftypefn {Architecture Function} {struct gdbarch_data *} gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init})
6143 @var{post_init} is used to obtain an initial value for a
6144 per-architecture data-pointer @emph{after}. Since @var{post_init} is
6145 always called after architecture creation, it both receives the fully
6146 initialized architecture and is free to call modules that use
6147 per-architecture data (care needs to be taken to ensure that those
6148 other modules do not try to call back to this module as that will
6149 create in cycles in the initialization call graph).
6152 These functions return a @code{struct gdbarch_data} that is used to
6153 identify the per-architecture data-pointer added for that module.
6155 The per-architecture data-pointer is accessed using the function:
6157 @deftypefn {Architecture Function} {void *} gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
6158 Given the architecture @var{arch} and module data handle
6159 @var{data_handle} (returned by @code{gdbarch_data_register_pre_init}
6160 or @code{gdbarch_data_register_post_init}), this function returns the
6161 current value of the per-architecture data-pointer. If the data
6162 pointer is @code{NULL}, it is first initialized by calling the
6163 corresponding @var{pre_init} or @var{post_init} method.
6166 The examples below assume the following definitions:
6169 struct nozel @{ int total; @};
6170 static struct gdbarch_data *nozel_handle;
6173 A module can extend the architecture vector, adding additional
6174 per-architecture data, using the @var{pre_init} method. The module's
6175 per-architecture data is then initialized during architecture
6178 In the below, the module's per-architecture @emph{nozel} is added. An
6179 architecture can specify its nozel by calling @code{set_gdbarch_nozel}
6180 from @code{gdbarch_init}.
6184 nozel_pre_init (struct obstack *obstack)
6186 struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
6193 set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
6195 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
6196 data->total = nozel;
6200 A module can on-demand create architecture dependent data structures
6201 using @code{post_init}.
6203 In the below, the nozel's total is computed on-demand by
6204 @code{nozel_post_init} using information obtained from the
6209 nozel_post_init (struct gdbarch *gdbarch)
6211 struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
6212 nozel->total = gdbarch@dots{} (gdbarch);
6219 nozel_total (struct gdbarch *gdbarch)
6221 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
6226 @section Wrapping Output Lines
6227 @cindex line wrap in output
6230 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
6231 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
6232 added in places that would be good breaking points. The utility
6233 routines will take care of actually wrapping if the line width is
6236 The argument to @code{wrap_here} is an indentation string which is
6237 printed @emph{only} if the line breaks there. This argument is saved
6238 away and used later. It must remain valid until the next call to
6239 @code{wrap_here} or until a newline has been printed through the
6240 @code{*_filtered} functions. Don't pass in a local variable and then
6243 It is usually best to call @code{wrap_here} after printing a comma or
6244 space. If you call it before printing a space, make sure that your
6245 indentation properly accounts for the leading space that will print if
6246 the line wraps there.
6248 Any function or set of functions that produce filtered output must
6249 finish by printing a newline, to flush the wrap buffer, before switching
6250 to unfiltered (@code{printf}) output. Symbol reading routines that
6251 print warnings are a good example.
6253 @section Memory Management
6255 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
6256 @code{calloc}, @code{free} and @code{asprintf}.
6258 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
6259 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
6260 these functions do not return when the memory pool is empty. Instead,
6261 they unwind the stack using cleanups. These functions return
6262 @code{NULL} when requested to allocate a chunk of memory of size zero.
6264 @emph{Pragmatics: By using these functions, the need to check every
6265 memory allocation is removed. These functions provide portable
6268 @value{GDBN} does not use the function @code{free}.
6270 @value{GDBN} uses the function @code{xfree} to return memory to the
6271 memory pool. Consistent with ISO-C, this function ignores a request to
6272 free a @code{NULL} pointer.
6274 @emph{Pragmatics: On some systems @code{free} fails when passed a
6275 @code{NULL} pointer.}
6277 @value{GDBN} can use the non-portable function @code{alloca} for the
6278 allocation of small temporary values (such as strings).
6280 @emph{Pragmatics: This function is very non-portable. Some systems
6281 restrict the memory being allocated to no more than a few kilobytes.}
6283 @value{GDBN} uses the string function @code{xstrdup} and the print
6284 function @code{xstrprintf}.
6286 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
6287 functions such as @code{sprintf} are very prone to buffer overflow
6291 @section Compiler Warnings
6292 @cindex compiler warnings
6294 With few exceptions, developers should avoid the configuration option
6295 @samp{--disable-werror} when building @value{GDBN}. The exceptions
6296 are listed in the file @file{gdb/MAINTAINERS}. The default, when
6297 building with @sc{gcc}, is @samp{--enable-werror}.
6299 This option causes @value{GDBN} (when built using GCC) to be compiled
6300 with a carefully selected list of compiler warning flags. Any warnings
6301 from those flags are treated as errors.
6303 The current list of warning flags includes:
6307 Recommended @sc{gcc} warnings.
6309 @item -Wdeclaration-after-statement
6311 @sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
6312 code, but @sc{gcc} 2.x and @sc{c89} do not.
6314 @item -Wpointer-arith
6316 @item -Wformat-nonliteral
6317 Non-literal format strings, with a few exceptions, are bugs - they
6318 might contain unintended user-supplied format specifiers.
6319 Since @value{GDBN} uses the @code{format printf} attribute on all
6320 @code{printf} like functions this checks not just @code{printf} calls
6321 but also calls to functions such as @code{fprintf_unfiltered}.
6323 @item -Wno-pointer-sign
6324 In version 4.0, GCC began warning about pointer argument passing or
6325 assignment even when the source and destination differed only in
6326 signedness. However, most @value{GDBN} code doesn't distinguish
6327 carefully between @code{char} and @code{unsigned char}. In early 2006
6328 the @value{GDBN} developers decided correcting these warnings wasn't
6329 worth the time it would take.
6331 @item -Wno-unused-parameter
6332 Due to the way that @value{GDBN} is implemented many functions have
6333 unused parameters. Consequently this warning is avoided. The macro
6334 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
6335 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
6340 @itemx -Wno-char-subscripts
6341 These are warnings which might be useful for @value{GDBN}, but are
6342 currently too noisy to enable with @samp{-Werror}.
6346 @section Internal Error Recovery
6348 During its execution, @value{GDBN} can encounter two types of errors.
6349 User errors and internal errors. User errors include not only a user
6350 entering an incorrect command but also problems arising from corrupt
6351 object files and system errors when interacting with the target.
6352 Internal errors include situations where @value{GDBN} has detected, at
6353 run time, a corrupt or erroneous situation.
6355 When reporting an internal error, @value{GDBN} uses
6356 @code{internal_error} and @code{gdb_assert}.
6358 @value{GDBN} must not call @code{abort} or @code{assert}.
6360 @emph{Pragmatics: There is no @code{internal_warning} function. Either
6361 the code detected a user error, recovered from it and issued a
6362 @code{warning} or the code failed to correctly recover from the user
6363 error and issued an @code{internal_error}.}
6365 @section Command Names
6367 GDB U/I commands are written @samp{foo-bar}, not @samp{foo_bar}.
6369 @section Clean Design and Portable Implementation
6372 In addition to getting the syntax right, there's the little question of
6373 semantics. Some things are done in certain ways in @value{GDBN} because long
6374 experience has shown that the more obvious ways caused various kinds of
6377 @cindex assumptions about targets
6378 You can't assume the byte order of anything that comes from a target
6379 (including @var{value}s, object files, and instructions). Such things
6380 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
6381 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
6382 such as @code{bfd_get_32}.
6384 You can't assume that you know what interface is being used to talk to
6385 the target system. All references to the target must go through the
6386 current @code{target_ops} vector.
6388 You can't assume that the host and target machines are the same machine
6389 (except in the ``native'' support modules). In particular, you can't
6390 assume that the target machine's header files will be available on the
6391 host machine. Target code must bring along its own header files --
6392 written from scratch or explicitly donated by their owner, to avoid
6396 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
6397 to write the code portably than to conditionalize it for various
6400 @cindex system dependencies
6401 New @code{#ifdef}'s which test for specific compilers or manufacturers
6402 or operating systems are unacceptable. All @code{#ifdef}'s should test
6403 for features. The information about which configurations contain which
6404 features should be segregated into the configuration files. Experience
6405 has proven far too often that a feature unique to one particular system
6406 often creeps into other systems; and that a conditional based on some
6407 predefined macro for your current system will become worthless over
6408 time, as new versions of your system come out that behave differently
6409 with regard to this feature.
6411 Adding code that handles specific architectures, operating systems,
6412 target interfaces, or hosts, is not acceptable in generic code.
6414 @cindex portable file name handling
6415 @cindex file names, portability
6416 One particularly notorious area where system dependencies tend to
6417 creep in is handling of file names. The mainline @value{GDBN} code
6418 assumes Posix semantics of file names: absolute file names begin with
6419 a forward slash @file{/}, slashes are used to separate leading
6420 directories, case-sensitive file names. These assumptions are not
6421 necessarily true on non-Posix systems such as MS-Windows. To avoid
6422 system-dependent code where you need to take apart or construct a file
6423 name, use the following portable macros:
6426 @findex HAVE_DOS_BASED_FILE_SYSTEM
6427 @item HAVE_DOS_BASED_FILE_SYSTEM
6428 This preprocessing symbol is defined to a non-zero value on hosts
6429 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
6430 symbol to write conditional code which should only be compiled for
6433 @findex IS_DIR_SEPARATOR
6434 @item IS_DIR_SEPARATOR (@var{c})
6435 Evaluates to a non-zero value if @var{c} is a directory separator
6436 character. On Unix and GNU/Linux systems, only a slash @file{/} is
6437 such a character, but on Windows, both @file{/} and @file{\} will
6440 @findex IS_ABSOLUTE_PATH
6441 @item IS_ABSOLUTE_PATH (@var{file})
6442 Evaluates to a non-zero value if @var{file} is an absolute file name.
6443 For Unix and GNU/Linux hosts, a name which begins with a slash
6444 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
6445 @file{x:\bar} are also absolute file names.
6447 @findex FILENAME_CMP
6448 @item FILENAME_CMP (@var{f1}, @var{f2})
6449 Calls a function which compares file names @var{f1} and @var{f2} as
6450 appropriate for the underlying host filesystem. For Posix systems,
6451 this simply calls @code{strcmp}; on case-insensitive filesystems it
6452 will call @code{strcasecmp} instead.
6454 @findex DIRNAME_SEPARATOR
6455 @item DIRNAME_SEPARATOR
6456 Evaluates to a character which separates directories in
6457 @code{PATH}-style lists, typically held in environment variables.
6458 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
6460 @findex SLASH_STRING
6462 This evaluates to a constant string you should use to produce an
6463 absolute filename from leading directories and the file's basename.
6464 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
6465 @code{"\\"} for some Windows-based ports.
6468 In addition to using these macros, be sure to use portable library
6469 functions whenever possible. For example, to extract a directory or a
6470 basename part from a file name, use the @code{dirname} and
6471 @code{basename} library functions (available in @code{libiberty} for
6472 platforms which don't provide them), instead of searching for a slash
6473 with @code{strrchr}.
6475 Another way to generalize @value{GDBN} along a particular interface is with an
6476 attribute struct. For example, @value{GDBN} has been generalized to handle
6477 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
6478 by defining the @code{target_ops} structure and having a current target (as
6479 well as a stack of targets below it, for memory references). Whenever
6480 something needs to be done that depends on which remote interface we are
6481 using, a flag in the current target_ops structure is tested (e.g.,
6482 @code{target_has_stack}), or a function is called through a pointer in the
6483 current target_ops structure. In this way, when a new remote interface
6484 is added, only one module needs to be touched---the one that actually
6485 implements the new remote interface. Other examples of
6486 attribute-structs are BFD access to multiple kinds of object file
6487 formats, or @value{GDBN}'s access to multiple source languages.
6489 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
6490 the code interfacing between @code{ptrace} and the rest of
6491 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
6492 something was very painful. In @value{GDBN} 4.x, these have all been
6493 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
6494 with variations between systems the same way any system-independent
6495 file would (hooks, @code{#if defined}, etc.), and machines which are
6496 radically different don't need to use @file{infptrace.c} at all.
6498 All debugging code must be controllable using the @samp{set debug
6499 @var{module}} command. Do not use @code{printf} to print trace
6500 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
6501 @code{#ifdef DEBUG}.
6505 @chapter Porting @value{GDBN}
6506 @cindex porting to new machines
6508 Most of the work in making @value{GDBN} compile on a new machine is in
6509 specifying the configuration of the machine. Porting a new
6510 architecture to @value{GDBN} can be broken into a number of steps.
6515 Ensure a @sc{bfd} exists for executables of the target architecture in
6516 the @file{bfd} directory. If one does not exist, create one by
6517 modifying an existing similar one.
6520 Implement a disassembler for the target architecture in the @file{opcodes}
6524 Define the target architecture in the @file{gdb} directory
6525 (@pxref{Adding a New Target, , Adding a New Target}). Add the pattern
6526 for the new target to @file{configure.tgt} with the names of the files
6527 that contain the code. By convention the target architecture
6528 definition for an architecture @var{arch} is placed in
6529 @file{@var{arch}-tdep.c}.
6531 Within @file{@var{arch}-tdep.c} define the function
6532 @code{_initialize_@var{arch}_tdep} which calls
6533 @code{gdbarch_register} to create the new @code{@w{struct
6534 gdbarch}} for the architecture.
6537 If a new remote target is needed, consider adding a new remote target
6538 by defining a function
6539 @code{_initialize_remote_@var{arch}}. However if at all possible
6540 use the @value{GDBN} @emph{Remote Serial Protocol} for this and implement
6541 the server side protocol independently with the target.
6544 If desired implement a simulator in the @file{sim} directory. This
6545 should create the library @file{libsim.a} implementing the interface
6546 in @file{remote-sim.h} (found in the @file{include} directory).
6549 Build and test. If desired, lobby the @sc{gdb} steering group to
6550 have the new port included in the main distribution!
6553 Add a description of the new architecture to the main @value{GDBN} user
6554 guide (@pxref{Configuration Specific Information, , Configuration
6555 Specific Information, gdb, Debugging with @value{GDBN}}).
6559 @node Versions and Branches
6560 @chapter Versions and Branches
6564 @value{GDBN}'s version is determined by the file
6565 @file{gdb/version.in} and takes one of the following forms:
6568 @item @var{major}.@var{minor}
6569 @itemx @var{major}.@var{minor}.@var{patchlevel}
6570 an official release (e.g., 6.2 or 6.2.1)
6571 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}
6572 a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g.,
6573 6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308)
6574 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs
6575 a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g.,
6576 6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
6577 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor})
6578 a vendor specific release of @value{GDBN}, that while based on@*
6579 @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD},
6580 may include additional changes
6583 @value{GDBN}'s mainline uses the @var{major} and @var{minor} version
6584 numbers from the most recent release branch, with a @var{patchlevel}
6585 of 50. At the time each new release branch is created, the mainline's
6586 @var{major} and @var{minor} version numbers are updated.
6588 @value{GDBN}'s release branch is similar. When the branch is cut, the
6589 @var{patchlevel} is changed from 50 to 90. As draft releases are
6590 drawn from the branch, the @var{patchlevel} is incremented. Once the
6591 first release (@var{major}.@var{minor}) has been made, the
6592 @var{patchlevel} is set to 0 and updates have an incremented
6595 For snapshots, and @sc{cvs} check outs, it is also possible to
6596 identify the @sc{cvs} origin:
6599 @item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD}
6600 drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302)
6601 @item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD}
6602 @itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{}
6603 drawn from a release branch prior to the release (e.g.,
6605 @item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD}
6606 @itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{}
6607 drawn from a release branch after the release (e.g., 6.2.0.20020308)
6610 If the previous @value{GDBN} version is 6.1 and the current version is
6611 6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor},
6612 here's an illustration of a typical sequence:
6619 +--------------------------.
6622 6.2.50.20020303-cvs 6.1.90 (draft #1)
6624 6.2.50.20020304-cvs 6.1.90.20020304-cvs
6626 6.2.50.20020305-cvs 6.1.91 (draft #2)
6628 6.2.50.20020306-cvs 6.1.91.20020306-cvs
6630 6.2.50.20020307-cvs 6.2 (release)
6632 6.2.50.20020308-cvs 6.2.0.20020308-cvs
6634 6.2.50.20020309-cvs 6.2.1 (update)
6636 6.2.50.20020310-cvs <branch closed>
6640 +--------------------------.
6643 6.3.50.20020312-cvs 6.2.90 (draft #1)
6647 @section Release Branches
6648 @cindex Release Branches
6650 @value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a
6651 single release branch, and identifies that branch using the @sc{cvs}
6655 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint
6656 gdb_@var{major}_@var{minor}-branch
6657 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release
6660 @emph{Pragmatics: To help identify the date at which a branch or
6661 release is made, both the branchpoint and release tags include the
6662 date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The
6663 branch tag, denoting the head of the branch, does not need this.}
6665 @section Vendor Branches
6666 @cindex vendor branches
6668 To avoid version conflicts, vendors are expected to modify the file
6669 @file{gdb/version.in} to include a vendor unique alphabetic identifier
6670 (an official @value{GDBN} release never uses alphabetic characters in
6671 its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit
6674 @section Experimental Branches
6675 @cindex experimental branches
6677 @subsection Guidelines
6679 @value{GDBN} permits the creation of branches, cut from the @sc{cvs}
6680 repository, for experimental development. Branches make it possible
6681 for developers to share preliminary work, and maintainers to examine
6682 significant new developments.
6684 The following are a set of guidelines for creating such branches:
6688 @item a branch has an owner
6689 The owner can set further policy for a branch, but may not change the
6690 ground rules. In particular, they can set a policy for commits (be it
6691 adding more reviewers or deciding who can commit).
6693 @item all commits are posted
6694 All changes committed to a branch shall also be posted to
6695 @email{gdb-patches@@sourceware.org, the @value{GDBN} patches
6696 mailing list}. While commentary on such changes are encouraged, people
6697 should remember that the changes only apply to a branch.
6699 @item all commits are covered by an assignment
6700 This ensures that all changes belong to the Free Software Foundation,
6701 and avoids the possibility that the branch may become contaminated.
6703 @item a branch is focused
6704 A focused branch has a single objective or goal, and does not contain
6705 unnecessary or irrelevant changes. Cleanups, where identified, being
6706 be pushed into the mainline as soon as possible.
6708 @item a branch tracks mainline
6709 This keeps the level of divergence under control. It also keeps the
6710 pressure on developers to push cleanups and other stuff into the
6713 @item a branch shall contain the entire @value{GDBN} module
6714 The @value{GDBN} module @code{gdb} should be specified when creating a
6715 branch (branches of individual files should be avoided). @xref{Tags}.
6717 @item a branch shall be branded using @file{version.in}
6718 The file @file{gdb/version.in} shall be modified so that it identifies
6719 the branch @var{owner} and branch @var{name}, e.g.,
6720 @samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}.
6727 To simplify the identification of @value{GDBN} branches, the following
6728 branch tagging convention is strongly recommended:
6732 @item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6733 @itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch
6734 The branch point and corresponding branch tag. @var{YYYYMMDD} is the
6735 date that the branch was created. A branch is created using the
6736 sequence: @anchor{experimental branch tags}
6738 cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb
6739 cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \
6740 @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb
6743 @item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6744 The tagged point, on the mainline, that was used when merging the branch
6745 on @var{yyyymmdd}. To merge in all changes since the branch was cut,
6746 use a command sequence like:
6748 cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb
6750 -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6751 -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6754 Similar sequences can be used to just merge in changes since the last
6760 For further information on @sc{cvs}, see
6761 @uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}.
6763 @node Start of New Year Procedure
6764 @chapter Start of New Year Procedure
6765 @cindex new year procedure
6767 At the start of each new year, the following actions should be performed:
6771 Rotate the ChangeLog file
6773 The current @file{ChangeLog} file should be renamed into
6774 @file{ChangeLog-YYYY} where YYYY is the year that has just passed.
6775 A new @file{ChangeLog} file should be created, and its contents should
6776 contain a reference to the previous ChangeLog. The following should
6777 also be preserved at the end of the new ChangeLog, in order to provide
6778 the appropriate settings when editing this file with Emacs:
6784 version-control: never
6790 Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY})
6791 in @file{gdb/config/djgpp/fnchange.lst}.
6794 Update the copyright year in the startup message
6796 Update the copyright year in:
6799 file @file{top.c}, function @code{print_gdb_version}
6801 file @file{gdbserver/server.c}, function @code{gdbserver_version}
6803 file @file{gdbserver/gdbreplay.c}, function @code{gdbreplay_version}
6807 Run the @file{copyright.py} Python script to add the new year in the copyright
6808 notices of most source files. This script has been tested with Python
6815 @chapter Releasing @value{GDBN}
6816 @cindex making a new release of gdb
6818 @section Branch Commit Policy
6820 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
6821 5.1 and 5.2 all used the below:
6825 The @file{gdb/MAINTAINERS} file still holds.
6827 Don't fix something on the branch unless/until it is also fixed in the
6828 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
6829 file is better than committing a hack.
6831 When considering a patch for the branch, suggested criteria include:
6832 Does it fix a build? Does it fix the sequence @kbd{break main; run}
6833 when debugging a static binary?
6835 The further a change is from the core of @value{GDBN}, the less likely
6836 the change will worry anyone (e.g., target specific code).
6838 Only post a proposal to change the core of @value{GDBN} after you've
6839 sent individual bribes to all the people listed in the
6840 @file{MAINTAINERS} file @t{;-)}
6843 @emph{Pragmatics: Provided updates are restricted to non-core
6844 functionality there is little chance that a broken change will be fatal.
6845 This means that changes such as adding a new architectures or (within
6846 reason) support for a new host are considered acceptable.}
6849 @section Obsoleting code
6851 Before anything else, poke the other developers (and around the source
6852 code) to see if there is anything that can be removed from @value{GDBN}
6853 (an old target, an unused file).
6855 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
6856 line. Doing this means that it is easy to identify something that has
6857 been obsoleted when greping through the sources.
6859 The process is done in stages --- this is mainly to ensure that the
6860 wider @value{GDBN} community has a reasonable opportunity to respond.
6861 Remember, everything on the Internet takes a week.
6865 Post the proposal on @email{gdb@@sourceware.org, the GDB mailing
6866 list} Creating a bug report to track the task's state, is also highly
6871 Post the proposal on @email{gdb-announce@@sourceware.org, the GDB
6872 Announcement mailing list}.
6876 Go through and edit all relevant files and lines so that they are
6877 prefixed with the word @code{OBSOLETE}.
6879 Wait until the next GDB version, containing this obsolete code, has been
6882 Remove the obsolete code.
6886 @emph{Maintainer note: While removing old code is regrettable it is
6887 hopefully better for @value{GDBN}'s long term development. Firstly it
6888 helps the developers by removing code that is either no longer relevant
6889 or simply wrong. Secondly since it removes any history associated with
6890 the file (effectively clearing the slate) the developer has a much freer
6891 hand when it comes to fixing broken files.}
6895 @section Before the Branch
6897 The most important objective at this stage is to find and fix simple
6898 changes that become a pain to track once the branch is created. For
6899 instance, configuration problems that stop @value{GDBN} from even
6900 building. If you can't get the problem fixed, document it in the
6901 @file{gdb/PROBLEMS} file.
6903 @subheading Prompt for @file{gdb/NEWS}
6905 People always forget. Send a post reminding them but also if you know
6906 something interesting happened add it yourself. The @code{schedule}
6907 script will mention this in its e-mail.
6909 @subheading Review @file{gdb/README}
6911 Grab one of the nightly snapshots and then walk through the
6912 @file{gdb/README} looking for anything that can be improved. The
6913 @code{schedule} script will mention this in its e-mail.
6915 @subheading Refresh any imported files.
6917 A number of files are taken from external repositories. They include:
6921 @file{texinfo/texinfo.tex}
6923 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
6926 @file{etc/standards.texi}, @file{etc/make-stds.texi}
6929 @subheading Check the ARI
6931 @uref{http://sourceware.org/gdb/ari,,A.R.I.} is an @code{awk} script
6932 (Awk Regression Index ;-) that checks for a number of errors and coding
6933 conventions. The checks include things like using @code{malloc} instead
6934 of @code{xmalloc} and file naming problems. There shouldn't be any
6937 @subsection Review the bug data base
6939 Close anything obviously fixed.
6941 @subsection Check all cross targets build
6943 The targets are listed in @file{gdb/MAINTAINERS}.
6946 @section Cut the Branch
6948 @subheading Create the branch
6953 $ V=`echo $v | sed 's/\./_/g'`
6954 $ D=`date -u +%Y-%m-%d`
6957 $ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6958 -D $D-gmt gdb_$V-$D-branchpoint insight
6959 cvs -f -d :ext:sourceware.org:/cvs/src rtag
6960 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight
6963 $ echo cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6964 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
6965 cvs -f -d :ext:sourceware.org:/cvs/src rtag \
6966 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
6974 By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact
6977 The trunk is first tagged so that the branch point can easily be found.
6979 Insight, which includes @value{GDBN}, is tagged at the same time.
6981 @file{version.in} gets bumped to avoid version number conflicts.
6983 The reading of @file{.cvsrc} is disabled using @file{-f}.
6986 @subheading Update @file{version.in}
6991 $ V=`echo $v | sed 's/\./_/g'`
6995 $ echo cvs -f -d :ext:sourceware.org:/cvs/src co \
6996 -r gdb_$V-branch src/gdb/version.in
6997 cvs -f -d :ext:sourceware.org:/cvs/src co
6998 -r gdb_5_2-branch src/gdb/version.in
7000 U src/gdb/version.in
7002 $ echo $u.90-0000-00-00-cvs > version.in
7004 5.1.90-0000-00-00-cvs
7005 $ cvs -f commit version.in
7010 @file{0000-00-00} is used as a date to pump prime the version.in update
7013 @file{.90} and the previous branch version are used as fairly arbitrary
7014 initial branch version number.
7018 @subheading Update the web and news pages
7022 @subheading Tweak cron to track the new branch
7024 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
7025 This file needs to be updated so that:
7029 A daily timestamp is added to the file @file{version.in}.
7031 The new branch is included in the snapshot process.
7035 See the file @file{gdbadmin/cron/README} for how to install the updated
7038 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
7039 any changes. That file is copied to both the branch/ and current/
7040 snapshot directories.
7043 @subheading Update the NEWS and README files
7045 The @file{NEWS} file needs to be updated so that on the branch it refers
7046 to @emph{changes in the current release} while on the trunk it also
7047 refers to @emph{changes since the current release}.
7049 The @file{README} file needs to be updated so that it refers to the
7052 @subheading Post the branch info
7054 Send an announcement to the mailing lists:
7058 @email{gdb-announce@@sourceware.org, GDB Announcement mailing list}
7060 @email{gdb@@sourceware.org, GDB Discussion mailing list} and
7061 @email{gdb-testers@@sourceware.org, GDB Testers mailing list}
7064 @emph{Pragmatics: The branch creation is sent to the announce list to
7065 ensure that people people not subscribed to the higher volume discussion
7068 The announcement should include:
7074 How to check out the branch using CVS.
7076 The date/number of weeks until the release.
7078 The branch commit policy still holds.
7081 @section Stabilize the branch
7083 Something goes here.
7085 @section Create a Release
7087 The process of creating and then making available a release is broken
7088 down into a number of stages. The first part addresses the technical
7089 process of creating a releasable tar ball. The later stages address the
7090 process of releasing that tar ball.
7092 When making a release candidate just the first section is needed.
7094 @subsection Create a release candidate
7096 The objective at this stage is to create a set of tar balls that can be
7097 made available as a formal release (or as a less formal release
7100 @subsubheading Freeze the branch
7102 Send out an e-mail notifying everyone that the branch is frozen to
7103 @email{gdb-patches@@sourceware.org}.
7105 @subsubheading Establish a few defaults.
7110 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
7112 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
7116 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
7118 /home/gdbadmin/bin/autoconf
7127 Check the @code{autoconf} version carefully. You want to be using the
7128 version documented in the toplevel @file{README-maintainer-mode} file.
7129 It is very unlikely that the version of @code{autoconf} installed in
7130 system directories (e.g., @file{/usr/bin/autoconf}) is correct.
7133 @subsubheading Check out the relevant modules:
7136 $ for m in gdb insight
7138 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
7148 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
7149 any confusion between what is written here and what your local
7150 @code{cvs} really does.
7153 @subsubheading Update relevant files.
7159 Major releases get their comments added as part of the mainline. Minor
7160 releases should probably mention any significant bugs that were fixed.
7162 Don't forget to include the @file{ChangeLog} entry.
7165 $ emacs gdb/src/gdb/NEWS
7170 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
7171 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7176 You'll need to update:
7188 $ emacs gdb/src/gdb/README
7193 $ cp gdb/src/gdb/README insight/src/gdb/README
7194 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7197 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
7198 before the initial branch was cut so just a simple substitute is needed
7201 @emph{Maintainer note: Other projects generate @file{README} and
7202 @file{INSTALL} from the core documentation. This might be worth
7205 @item gdb/version.in
7208 $ echo $v > gdb/src/gdb/version.in
7209 $ cat gdb/src/gdb/version.in
7211 $ emacs gdb/src/gdb/version.in
7214 ... Bump to version ...
7216 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
7217 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
7222 @subsubheading Do the dirty work
7224 This is identical to the process used to create the daily snapshot.
7227 $ for m in gdb insight
7229 ( cd $m/src && gmake -f src-release $m.tar )
7233 If the top level source directory does not have @file{src-release}
7234 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
7237 $ for m in gdb insight
7239 ( cd $m/src && gmake -f Makefile.in $m.tar )
7243 @subsubheading Check the source files
7245 You're looking for files that have mysteriously disappeared.
7246 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
7247 for the @file{version.in} update @kbd{cronjob}.
7250 $ ( cd gdb/src && cvs -f -q -n update )
7254 @dots{} lots of generated files @dots{}
7259 @dots{} lots of generated files @dots{}
7264 @emph{Don't worry about the @file{gdb.info-??} or
7265 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
7266 was also generated only something strange with CVS means that they
7267 didn't get suppressed). Fixing it would be nice though.}
7269 @subsubheading Create compressed versions of the release
7275 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
7276 $ for m in gdb insight
7278 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
7279 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
7289 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
7290 in that mode, @code{gzip} does not know the name of the file and, hence,
7291 can not include it in the compressed file. This is also why the release
7292 process runs @code{tar} and @code{bzip2} as separate passes.
7295 @subsection Sanity check the tar ball
7297 Pick a popular machine (Solaris/PPC?) and try the build on that.
7300 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
7305 $ ./gdb/gdb ./gdb/gdb
7309 Breakpoint 1 at 0x80732bc: file main.c, line 734.
7311 Starting program: /tmp/gdb-5.2/gdb/gdb
7313 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
7314 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
7316 $1 = @{argc = 136426532, argv = 0x821b7f0@}
7320 @subsection Make a release candidate available
7322 If this is a release candidate then the only remaining steps are:
7326 Commit @file{version.in} and @file{ChangeLog}
7328 Tweak @file{version.in} (and @file{ChangeLog} to read
7329 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
7330 process can restart.
7332 Make the release candidate available in
7333 @uref{ftp://sourceware.org/pub/gdb/snapshots/branch}
7335 Notify the relevant mailing lists ( @email{gdb@@sourceware.org} and
7336 @email{gdb-testers@@sourceware.org} that the candidate is available.
7339 @subsection Make a formal release available
7341 (And you thought all that was required was to post an e-mail.)
7343 @subsubheading Install on sware
7345 Copy the new files to both the release and the old release directory:
7348 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
7349 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
7353 Clean up the releases directory so that only the most recent releases
7354 are available (e.g.@: keep 5.2 and 5.2.1 but remove 5.1):
7357 $ cd ~ftp/pub/gdb/releases
7362 Update the file @file{README} and @file{.message} in the releases
7369 $ ln README .message
7372 @subsubheading Update the web pages.
7376 @item htdocs/download/ANNOUNCEMENT
7377 This file, which is posted as the official announcement, includes:
7380 General announcement.
7382 News. If making an @var{M}.@var{N}.1 release, retain the news from
7383 earlier @var{M}.@var{N} release.
7388 @item htdocs/index.html
7389 @itemx htdocs/news/index.html
7390 @itemx htdocs/download/index.html
7391 These files include:
7394 Announcement of the most recent release.
7396 News entry (remember to update both the top level and the news directory).
7398 These pages also need to be regenerate using @code{index.sh}.
7400 @item download/onlinedocs/
7401 You need to find the magic command that is used to generate the online
7402 docs from the @file{.tar.bz2}. The best way is to look in the output
7403 from one of the nightly @code{cron} jobs and then just edit accordingly.
7407 $ ~/ss/update-web-docs \
7408 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
7410 /www/sourceware/htdocs/gdb/download/onlinedocs \
7415 Just like the online documentation. Something like:
7418 $ /bin/sh ~/ss/update-web-ari \
7419 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
7421 /www/sourceware/htdocs/gdb/download/ari \
7427 @subsubheading Shadow the pages onto gnu
7429 Something goes here.
7432 @subsubheading Install the @value{GDBN} tar ball on GNU
7434 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
7435 @file{~ftp/gnu/gdb}.
7437 @subsubheading Make the @file{ANNOUNCEMENT}
7439 Post the @file{ANNOUNCEMENT} file you created above to:
7443 @email{gdb-announce@@sourceware.org, GDB Announcement mailing list}
7445 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
7446 day or so to let things get out)
7448 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
7453 The release is out but you're still not finished.
7455 @subsubheading Commit outstanding changes
7457 In particular you'll need to commit any changes to:
7461 @file{gdb/ChangeLog}
7463 @file{gdb/version.in}
7470 @subsubheading Tag the release
7475 $ d=`date -u +%Y-%m-%d`
7478 $ ( cd insight/src/gdb && cvs -f -q update )
7479 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
7482 Insight is used since that contains more of the release than
7485 @subsubheading Mention the release on the trunk
7487 Just put something in the @file{ChangeLog} so that the trunk also
7488 indicates when the release was made.
7490 @subsubheading Restart @file{gdb/version.in}
7492 If @file{gdb/version.in} does not contain an ISO date such as
7493 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
7494 committed all the release changes it can be set to
7495 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
7496 is important - it affects the snapshot process).
7498 Don't forget the @file{ChangeLog}.
7500 @subsubheading Merge into trunk
7502 The files committed to the branch may also need changes merged into the
7505 @subsubheading Revise the release schedule
7507 Post a revised release schedule to @email{gdb@@sourceware.org, GDB
7508 Discussion List} with an updated announcement. The schedule can be
7509 generated by running:
7512 $ ~/ss/schedule `date +%s` schedule
7516 The first parameter is approximate date/time in seconds (from the epoch)
7517 of the most recent release.
7519 Also update the schedule @code{cronjob}.
7521 @section Post release
7523 Remove any @code{OBSOLETE} code.
7530 The testsuite is an important component of the @value{GDBN} package.
7531 While it is always worthwhile to encourage user testing, in practice
7532 this is rarely sufficient; users typically use only a small subset of
7533 the available commands, and it has proven all too common for a change
7534 to cause a significant regression that went unnoticed for some time.
7536 The @value{GDBN} testsuite uses the DejaGNU testing framework. The
7537 tests themselves are calls to various @code{Tcl} procs; the framework
7538 runs all the procs and summarizes the passes and fails.
7540 @section Using the Testsuite
7542 @cindex running the test suite
7543 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
7544 testsuite's objdir) and type @code{make check}. This just sets up some
7545 environment variables and invokes DejaGNU's @code{runtest} script. While
7546 the testsuite is running, you'll get mentions of which test file is in use,
7547 and a mention of any unexpected passes or fails. When the testsuite is
7548 finished, you'll get a summary that looks like this:
7553 # of expected passes 6016
7554 # of unexpected failures 58
7555 # of unexpected successes 5
7556 # of expected failures 183
7557 # of unresolved testcases 3
7558 # of untested testcases 5
7561 To run a specific test script, type:
7563 make check RUNTESTFLAGS='@var{tests}'
7565 where @var{tests} is a list of test script file names, separated by
7568 If you use GNU make, you can use its @option{-j} option to run the
7569 testsuite in parallel. This can greatly reduce the amount of time it
7570 takes for the testsuite to run. In this case, if you set
7571 @code{RUNTESTFLAGS} then, by default, the tests will be run serially
7572 even under @option{-j}. You can override this and force a parallel run
7573 by setting the @code{make} variable @code{FORCE_PARALLEL} to any
7574 non-empty value. Note that the parallel @kbd{make check} assumes
7575 that you want to run the entire testsuite, so it is not compatible
7576 with some dejagnu options, like @option{--directory}.
7578 The ideal test run consists of expected passes only; however, reality
7579 conspires to keep us from this ideal. Unexpected failures indicate
7580 real problems, whether in @value{GDBN} or in the testsuite. Expected
7581 failures are still failures, but ones which have been decided are too
7582 hard to deal with at the time; for instance, a test case might work
7583 everywhere except on AIX, and there is no prospect of the AIX case
7584 being fixed in the near future. Expected failures should not be added
7585 lightly, since you may be masking serious bugs in @value{GDBN}.
7586 Unexpected successes are expected fails that are passing for some
7587 reason, while unresolved and untested cases often indicate some minor
7588 catastrophe, such as the compiler being unable to deal with a test
7591 When making any significant change to @value{GDBN}, you should run the
7592 testsuite before and after the change, to confirm that there are no
7593 regressions. Note that truly complete testing would require that you
7594 run the testsuite with all supported configurations and a variety of
7595 compilers; however this is more than really necessary. In many cases
7596 testing with a single configuration is sufficient. Other useful
7597 options are to test one big-endian (Sparc) and one little-endian (x86)
7598 host, a cross config with a builtin simulator (powerpc-eabi,
7599 mips-elf), or a 64-bit host (Alpha).
7601 If you add new functionality to @value{GDBN}, please consider adding
7602 tests for it as well; this way future @value{GDBN} hackers can detect
7603 and fix their changes that break the functionality you added.
7604 Similarly, if you fix a bug that was not previously reported as a test
7605 failure, please add a test case for it. Some cases are extremely
7606 difficult to test, such as code that handles host OS failures or bugs
7607 in particular versions of compilers, and it's OK not to try to write
7608 tests for all of those.
7610 DejaGNU supports separate build, host, and target machines. However,
7611 some @value{GDBN} test scripts do not work if the build machine and
7612 the host machine are not the same. In such an environment, these scripts
7613 will give a result of ``UNRESOLVED'', like this:
7616 UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
7619 @section Testsuite Parameters
7621 Several variables exist to modify the behavior of the testsuite.
7625 @item @code{TRANSCRIPT}
7627 Sometimes it is convenient to get a transcript of the commands which
7628 the testsuite sends to @value{GDBN}. For example, if @value{GDBN}
7629 crashes during testing, a transcript can be used to more easily
7630 reconstruct the failure when running @value{GDBN} under @value{GDBN}.
7632 You can instruct the @value{GDBN} testsuite to write transcripts by
7633 setting the DejaGNU variable @code{TRANSCRIPT} (to any value)
7634 before invoking @code{runtest} or @kbd{make check}. The transcripts
7635 will be written into DejaGNU's output directory. One transcript will
7636 be made for each invocation of @value{GDBN}; they will be named
7637 @file{transcript.@var{n}}, where @var{n} is an integer. The first
7638 line of the transcript file will show how @value{GDBN} was invoked;
7639 each subsequent line is a command sent as input to @value{GDBN}.
7642 make check RUNTESTFLAGS=TRANSCRIPT=y
7645 Note that the transcript is not always complete. In particular, tests
7646 of completion can yield partial command lines.
7650 Sometimes one wishes to test a different @value{GDBN} than the one in the build
7651 directory. For example, one may wish to run the testsuite on
7652 @file{/usr/bin/gdb}.
7655 make check RUNTESTFLAGS=GDB=/usr/bin/gdb
7658 @item @code{GDBSERVER}
7660 When testing a different @value{GDBN}, it is often useful to also test a
7661 different gdbserver.
7664 make check RUNTESTFLAGS="GDB=/usr/bin/gdb GDBSERVER=/usr/bin/gdbserver"
7667 @item @code{INTERNAL_GDBFLAGS}
7669 When running the testsuite normally one doesn't want whatever is in
7670 @file{~/.gdbinit} to interfere with the tests, therefore the test harness
7671 passes @option{-nx} to @value{GDBN}. One also doesn't want any windowed
7672 version of @value{GDBN}, e.g., @samp{gdb -tui}, to run.
7673 This is achieved via @code{INTERNAL_GDBFLAGS}.
7676 set INTERNAL_GDBFLAGS "-nw -nx"
7679 This is all well and good, except when testing an installed @value{GDBN}
7680 that has been configured with @option{--with-system-gdbinit}. Here one
7681 does not want @file{~/.gdbinit} loaded but one may want the system
7682 @file{.gdbinit} file loaded. This can be achieved by pointing @code{$HOME}
7683 at a directory without a @file{.gdbinit} and by overriding
7684 @code{INTERNAL_GDBFLAGS} and removing @option{-nx}.
7688 HOME=`pwd` runtest \
7690 GDBSERVER=/usr/bin/gdbserver \
7691 INTERNAL_GDBFLAGS=-nw
7696 There are two ways to run the testsuite and pass additional parameters
7697 to DejaGnu. The first is with @kbd{make check} and specifying the
7698 makefile variable @samp{RUNTESTFLAGS}.
7701 make check RUNTESTFLAGS=TRANSCRIPT=y
7704 The second is to cd to the @file{testsuite} directory and invoke the DejaGnu
7705 @command{runtest} command directly.
7710 runtest TRANSCRIPT=y
7713 @section Testsuite Configuration
7714 @cindex Testsuite Configuration
7716 It is possible to adjust the behavior of the testsuite by defining
7717 the global variables listed below, either in a @file{site.exp} file,
7722 @item @code{gdb_test_timeout}
7724 Defining this variable changes the default timeout duration used during
7725 communication with @value{GDBN}. More specifically, the global variable
7726 used during testing is @code{timeout}, but this variable gets reset to
7727 @code{gdb_test_timeout} at the beginning of each testcase, making sure
7728 that any local change to @code{timeout} in a testcase does not affect
7729 subsequent testcases.
7731 This global variable comes in handy when the debugger is slower than
7732 normal due to the testing environment, triggering unexpected @code{TIMEOUT}
7733 test failures. Examples include when testing on a remote machine, or
7734 against a system where communications are slow.
7736 If not specifically defined, this variable gets automatically defined
7737 to the same value as @code{timeout} during the testsuite initialization.
7738 The default value of the timeout is defined in the file
7739 @file{gdb/testsuite/config/unix.exp} that is part of the @value{GDBN}
7740 test suite@footnote{If you are using a board file, it could override
7741 the test-suite default; search the board file for "timeout".}.
7745 @section Testsuite Organization
7747 @cindex test suite organization
7748 The testsuite is entirely contained in @file{gdb/testsuite}. While the
7749 testsuite includes some makefiles and configury, these are very minimal,
7750 and used for little besides cleaning up, since the tests themselves
7751 handle the compilation of the programs that @value{GDBN} will run. The file
7752 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
7753 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
7754 configuration-specific files, typically used for special-purpose
7755 definitions of procs like @code{gdb_load} and @code{gdb_start}.
7757 The tests themselves are to be found in @file{testsuite/gdb.*} and
7758 subdirectories of those. The names of the test files must always end
7759 with @file{.exp}. DejaGNU collects the test files by wildcarding
7760 in the test directories, so both subdirectories and individual files
7761 get chosen and run in alphabetical order.
7763 The following table lists the main types of subdirectories and what they
7764 are for. Since DejaGNU finds test files no matter where they are
7765 located, and since each test file sets up its own compilation and
7766 execution environment, this organization is simply for convenience and
7771 This is the base testsuite. The tests in it should apply to all
7772 configurations of @value{GDBN} (but generic native-only tests may live here).
7773 The test programs should be in the subset of C that is valid K&R,
7774 ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance
7777 @item gdb.@var{lang}
7778 Language-specific tests for any language @var{lang} besides C. Examples are
7779 @file{gdb.cp} and @file{gdb.java}.
7781 @item gdb.@var{platform}
7782 Non-portable tests. The tests are specific to a specific configuration
7783 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
7786 @item gdb.@var{compiler}
7787 Tests specific to a particular compiler. As of this writing (June
7788 1999), there aren't currently any groups of tests in this category that
7789 couldn't just as sensibly be made platform-specific, but one could
7790 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
7793 @item gdb.@var{subsystem}
7794 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
7795 instance, @file{gdb.disasm} exercises various disassemblers, while
7796 @file{gdb.stabs} tests pathways through the stabs symbol reader.
7799 @section Writing Tests
7800 @cindex writing tests
7802 In many areas, the @value{GDBN} tests are already quite comprehensive; you
7803 should be able to copy existing tests to handle new cases.
7805 You should try to use @code{gdb_test} whenever possible, since it
7806 includes cases to handle all the unexpected errors that might happen.
7807 However, it doesn't cost anything to add new test procedures; for
7808 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
7809 calls @code{gdb_test} multiple times.
7811 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
7812 necessary. Even if @value{GDBN} has several valid responses to
7813 a command, you can use @code{gdb_test_multiple}. Like @code{gdb_test},
7814 @code{gdb_test_multiple} recognizes internal errors and unexpected
7817 Do not write tests which expect a literal tab character from @value{GDBN}.
7818 On some operating systems (e.g.@: OpenBSD) the TTY layer expands tabs to
7819 spaces, so by the time @value{GDBN}'s output reaches expect the tab is gone.
7821 The source language programs do @emph{not} need to be in a consistent
7822 style. Since @value{GDBN} is used to debug programs written in many different
7823 styles, it's worth having a mix of styles in the testsuite; for
7824 instance, some @value{GDBN} bugs involving the display of source lines would
7825 never manifest themselves if the programs used GNU coding style
7828 Some testcase results need more detailed explanation:
7832 Known problem of @value{GDBN} itself. You must specify the @value{GDBN} bug
7833 report number like in these sample tests:
7835 kfail "gdb/13392" "continue to marker 2"
7839 setup_kfail gdb/13392 "*-*-*"
7840 kfail "continue to marker 2"
7844 Known problem of environment. This typically includes @value{NGCC} but it
7845 includes also many other system components which cannot be fixed in the
7846 @value{GDBN} project. Sample test with sanity check not knowing the specific
7847 cause of the problem:
7849 # On x86_64 it is commonly about 4MB.
7850 if @{$stub_size > 25000000@} @{
7851 xfail "stub size $stub_size is too large"
7856 You should provide bug report number for the failing component of the
7857 environment, if such bug report is available:
7859 if @{[test_compiler_info @{gcc-[0-3]-*@}]
7860 || [test_compiler_info @{gcc-4-[0-5]-*@}]@} @{
7861 setup_xfail "gcc/46955" *-*-*
7863 gdb_test "python print ttype.template_argument(2)" "&C::c"
7867 @section Board settings
7868 In @value{GDBN} testsuite, the tests can be configured or customized in the board
7869 file by means of @dfn{Board Settings}. Each setting should be consulted by
7870 test cases that depend on the corresponding feature.
7872 Here are the supported board settings:
7876 @item gdb,cannot_call_functions
7877 The board does not support inferior call, that is, invoking inferior functions
7879 @item gdb,can_reverse
7880 The board supports reverse execution.
7881 @item gdb,no_hardware_watchpoints
7882 The board does not support hardware watchpoints.
7884 @value{GDBN} is unable to intercept target file operations in remote and perform
7886 @item gdb,noinferiorio
7887 The board is unable to provide I/O capability to the inferior.
7888 @c @item gdb,noresults
7891 The board does not support signals.
7892 @item gdb,skip_huge_test
7893 Skip time-consuming tests on the board with slow connection.
7894 @item gdb,skip_float_tests
7895 Skip tests related to float points on target board.
7896 @item gdb,use_precord
7897 The board supports process record.
7898 @item gdb_server_prog
7899 The location of GDBserver. If GDBserver somewhere other than its default
7900 location is used in test, specify the location of GDBserver in this variable.
7901 The location is a file name of GDBserver that can be either absolute or
7902 relative to testsuite subdirectory in build directory.
7904 The location of in-process agent. If in-process agent other than its default
7905 location is used in test, specify the location of in-process agent in
7906 this variable. The location is a file name of in-process agent that can be
7907 either absolute or relative to testsuite subdirectory in build directory.
7909 @value{GDBN} does not support argument passing for inferior.
7911 The board does not support type @code{long long}.
7915 The tests are running with gdb stub.
7922 Check the @file{README} file, it often has useful information that does not
7923 appear anywhere else in the directory.
7926 * Getting Started:: Getting started working on @value{GDBN}
7927 * Debugging GDB:: Debugging @value{GDBN} with itself
7930 @node Getting Started
7932 @section Getting Started
7934 @value{GDBN} is a large and complicated program, and if you first starting to
7935 work on it, it can be hard to know where to start. Fortunately, if you
7936 know how to go about it, there are ways to figure out what is going on.
7938 This manual, the @value{GDBN} Internals manual, has information which applies
7939 generally to many parts of @value{GDBN}.
7941 Information about particular functions or data structures are located in
7942 comments with those functions or data structures. If you run across a
7943 function or a global variable which does not have a comment correctly
7944 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
7945 free to submit a bug report, with a suggested comment if you can figure
7946 out what the comment should say. If you find a comment which is
7947 actually wrong, be especially sure to report that.
7949 Comments explaining the function of macros defined in host, target, or
7950 native dependent files can be in several places. Sometimes they are
7951 repeated every place the macro is defined. Sometimes they are where the
7952 macro is used. Sometimes there is a header file which supplies a
7953 default definition of the macro, and the comment is there. This manual
7954 also documents all the available macros.
7955 @c (@pxref{Host Conditionals}, @pxref{Target
7956 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
7959 Start with the header files. Once you have some idea of how
7960 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
7961 @file{gdbtypes.h}), you will find it much easier to understand the
7962 code which uses and creates those symbol tables.
7964 You may wish to process the information you are getting somehow, to
7965 enhance your understanding of it. Summarize it, translate it to another
7966 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
7967 the code to predict what a test case would do and write the test case
7968 and verify your prediction, etc. If you are reading code and your eyes
7969 are starting to glaze over, this is a sign you need to use a more active
7972 Once you have a part of @value{GDBN} to start with, you can find more
7973 specifically the part you are looking for by stepping through each
7974 function with the @code{next} command. Do not use @code{step} or you
7975 will quickly get distracted; when the function you are stepping through
7976 calls another function try only to get a big-picture understanding
7977 (perhaps using the comment at the beginning of the function being
7978 called) of what it does. This way you can identify which of the
7979 functions being called by the function you are stepping through is the
7980 one which you are interested in. You may need to examine the data
7981 structures generated at each stage, with reference to the comments in
7982 the header files explaining what the data structures are supposed to
7985 Of course, this same technique can be used if you are just reading the
7986 code, rather than actually stepping through it. The same general
7987 principle applies---when the code you are looking at calls something
7988 else, just try to understand generally what the code being called does,
7989 rather than worrying about all its details.
7991 @cindex command implementation
7992 A good place to start when tracking down some particular area is with
7993 a command which invokes that feature. Suppose you want to know how
7994 single-stepping works. As a @value{GDBN} user, you know that the
7995 @code{step} command invokes single-stepping. The command is invoked
7996 via command tables (see @file{command.h}); by convention the function
7997 which actually performs the command is formed by taking the name of
7998 the command and adding @samp{_command}, or in the case of an
7999 @code{info} subcommand, @samp{_info}. For example, the @code{step}
8000 command invokes the @code{step_command} function and the @code{info
8001 display} command invokes @code{display_info}. When this convention is
8002 not followed, you might have to use @code{grep} or @kbd{M-x
8003 tags-search} in emacs, or run @value{GDBN} on itself and set a
8004 breakpoint in @code{execute_command}.
8006 @cindex @code{bug-gdb} mailing list
8007 If all of the above fail, it may be appropriate to ask for information
8008 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
8009 wondering if anyone could give me some tips about understanding
8010 @value{GDBN}''---if we had some magic secret we would put it in this manual.
8011 Suggestions for improving the manual are always welcome, of course.
8015 @section Debugging @value{GDBN} with itself
8016 @cindex debugging @value{GDBN}
8018 If @value{GDBN} is limping on your machine, this is the preferred way to get it
8019 fully functional. Be warned that in some ancient Unix systems, like
8020 Ultrix 4.2, a program can't be running in one process while it is being
8021 debugged in another. Rather than typing the command @kbd{@w{./gdb
8022 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
8023 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
8025 When you run @value{GDBN} in the @value{GDBN} source directory, it will read
8026 @file{gdb-gdb.gdb} file (plus possibly @file{gdb-gdb.py} file) that sets up
8027 some simple things to make debugging gdb easier. The @code{info} command, when
8028 executed without a subcommand in a @value{GDBN} being debugged by gdb, will pop
8029 you back up to the top level gdb. See @file{gdb-gdb.gdb} for details.
8031 If you use emacs, you will probably want to do a @code{make TAGS} after
8032 you configure your distribution; this will put the machine dependent
8033 routines for your local machine where they will be accessed first by
8036 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
8037 have run @code{fixincludes} if you are compiling with gcc.
8039 @section Submitting Patches
8041 @cindex submitting patches
8042 Thanks for thinking of offering your changes back to the community of
8043 @value{GDBN} users. In general we like to get well designed enhancements.
8044 Thanks also for checking in advance about the best way to transfer the
8047 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
8048 This manual summarizes what we believe to be clean design for @value{GDBN}.
8050 If the maintainers don't have time to put the patch in when it arrives,
8051 or if there is any question about a patch, it goes into a large queue
8052 with everyone else's patches and bug reports.
8054 @cindex legal papers for code contributions
8055 The legal issue is that to incorporate substantial changes requires a
8056 copyright assignment from you and/or your employer, granting ownership
8057 of the changes to the Free Software Foundation. You can get the
8058 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
8059 and asking for it. We recommend that people write in "All programs
8060 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
8061 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
8063 contributed with only one piece of legalese pushed through the
8064 bureaucracy and filed with the FSF. We can't start merging changes until
8065 this paperwork is received by the FSF (their rules, which we follow
8066 since we maintain it for them).
8068 Technically, the easiest way to receive changes is to receive each
8069 feature as a small context diff or unidiff, suitable for @code{patch}.
8070 Each message sent to me should include the changes to C code and
8071 header files for a single feature, plus @file{ChangeLog} entries for
8072 each directory where files were modified, and diffs for any changes
8073 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
8074 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
8075 single feature, they can be split down into multiple messages.
8077 In this way, if we read and like the feature, we can add it to the
8078 sources with a single patch command, do some testing, and check it in.
8079 If you leave out the @file{ChangeLog}, we have to write one. If you leave
8080 out the doc, we have to puzzle out what needs documenting. Etc., etc.
8082 The reason to send each change in a separate message is that we will not
8083 install some of the changes. They'll be returned to you with questions
8084 or comments. If we're doing our job correctly, the message back to you
8085 will say what you have to fix in order to make the change acceptable.
8086 The reason to have separate messages for separate features is so that
8087 the acceptable changes can be installed while one or more changes are
8088 being reworked. If multiple features are sent in a single message, we
8089 tend to not put in the effort to sort out the acceptable changes from
8090 the unacceptable, so none of the features get installed until all are
8093 If this sounds painful or authoritarian, well, it is. But we get a lot
8094 of bug reports and a lot of patches, and many of them don't get
8095 installed because we don't have the time to finish the job that the bug
8096 reporter or the contributor could have done. Patches that arrive
8097 complete, working, and well designed, tend to get installed on the day
8098 they arrive. The others go into a queue and get installed as time
8099 permits, which, since the maintainers have many demands to meet, may not
8100 be for quite some time.
8102 Please send patches directly to
8103 @email{gdb-patches@@sourceware.org, the @value{GDBN} maintainers}.
8105 @section Build Script
8107 @cindex build script
8109 The script @file{gdb_buildall.sh} builds @value{GDBN} with flag
8110 @option{--enable-targets=all} set. This builds @value{GDBN} with all supported
8111 targets activated. This helps testing @value{GDBN} when doing changes that
8112 affect more than one architecture and is much faster than using
8113 @file{gdb_mbuild.sh}.
8115 After building @value{GDBN} the script checks which architectures are
8116 supported and then switches the current architecture to each of those to get
8117 information about the architecture. The test results are stored in log files
8118 in the directory the script was called from.
8120 @include observer.texi
8122 @node GNU Free Documentation License
8123 @appendix GNU Free Documentation License
8127 @unnumbered Concept Index
8131 @node Function and Variable Index
8132 @unnumbered Function and Variable Index