1 \input texinfo @c -*- texinfo -*-
2 @setfilename gdbint.info
4 @dircategory Software development
6 * Gdb-Internals: (gdbint). The GNU debugger's internals.
10 This file documents the internals of the GNU debugger @value{GDBN}.
11 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1996, 1998, 1999, 2000, 2001,
12 2002, 2003, 2004, 2005, 2006
13 Free 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 1.1 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''.
25 @setchapternewpage off
26 @settitle @value{GDBN} Internals
32 @title @value{GDBN} Internals
33 @subtitle{A guide to the internals of the GNU debugger}
35 @author Cygnus Solutions
36 @author Second Edition:
38 @author Cygnus Solutions
41 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
42 \xdef\manvers{\$Revision$} % For use in headers, footers too
44 \hfill Cygnus Solutions\par
46 \hfill \TeX{}info \texinfoversion\par
50 @vskip 0pt plus 1filll
51 Copyright @copyright{} 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001,
52 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.1 or
56 any later version published by the Free Software Foundation; with no
57 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
58 Texts. A copy of the license is included in the section entitled ``GNU
59 Free Documentation License''.
65 @c Perhaps this should be the title of the document (but only for info,
66 @c not for TeX). Existing GNU manuals seem inconsistent on this point.
67 @top Scope of this Document
69 This document documents the internals of the GNU debugger, @value{GDBN}. It
70 includes description of @value{GDBN}'s key algorithms and operations, as well
71 as the mechanisms that adapt @value{GDBN} to specific hosts and targets.
82 * Target Architecture Definition::
83 * Target Descriptions::
84 * Target Vector Definition::
89 * Versions and Branches::
90 * Start of New Year Procedure::
95 * GDB Observers:: @value{GDBN} Currently available observers
96 * GNU Free Documentation License:: The license for this documentation
102 @chapter Requirements
103 @cindex requirements for @value{GDBN}
105 Before diving into the internals, you should understand the formal
106 requirements and other expectations for @value{GDBN}. Although some
107 of these may seem obvious, there have been proposals for @value{GDBN}
108 that have run counter to these requirements.
110 First of all, @value{GDBN} is a debugger. It's not designed to be a
111 front panel for embedded systems. It's not a text editor. It's not a
112 shell. It's not a programming environment.
114 @value{GDBN} is an interactive tool. Although a batch mode is
115 available, @value{GDBN}'s primary role is to interact with a human
118 @value{GDBN} should be responsive to the user. A programmer hot on
119 the trail of a nasty bug, and operating under a looming deadline, is
120 going to be very impatient of everything, including the response time
121 to debugger commands.
123 @value{GDBN} should be relatively permissive, such as for expressions.
124 While the compiler should be picky (or have the option to be made
125 picky), since source code lives for a long time usually, the
126 programmer doing debugging shouldn't be spending time figuring out to
127 mollify the debugger.
129 @value{GDBN} will be called upon to deal with really large programs.
130 Executable sizes of 50 to 100 megabytes occur regularly, and we've
131 heard reports of programs approaching 1 gigabyte in size.
133 @value{GDBN} should be able to run everywhere. No other debugger is
134 available for even half as many configurations as @value{GDBN}
138 @node Overall Structure
140 @chapter Overall Structure
142 @value{GDBN} consists of three major subsystems: user interface,
143 symbol handling (the @dfn{symbol side}), and target system handling (the
146 The user interface consists of several actual interfaces, plus
149 The symbol side consists of object file readers, debugging info
150 interpreters, symbol table management, source language expression
151 parsing, type and value printing.
153 The target side consists of execution control, stack frame analysis, and
154 physical target manipulation.
156 The target side/symbol side division is not formal, and there are a
157 number of exceptions. For instance, core file support involves symbolic
158 elements (the basic core file reader is in BFD) and target elements (it
159 supplies the contents of memory and the values of registers). Instead,
160 this division is useful for understanding how the minor subsystems
163 @section The Symbol Side
165 The symbolic side of @value{GDBN} can be thought of as ``everything
166 you can do in @value{GDBN} without having a live program running''.
167 For instance, you can look at the types of variables, and evaluate
168 many kinds of expressions.
170 @section The Target Side
172 The target side of @value{GDBN} is the ``bits and bytes manipulator''.
173 Although it may make reference to symbolic info here and there, most
174 of the target side will run with only a stripped executable
175 available---or even no executable at all, in remote debugging cases.
177 Operations such as disassembly, stack frame crawls, and register
178 display, are able to work with no symbolic info at all. In some cases,
179 such as disassembly, @value{GDBN} will use symbolic info to present addresses
180 relative to symbols rather than as raw numbers, but it will work either
183 @section Configurations
187 @dfn{Host} refers to attributes of the system where @value{GDBN} runs.
188 @dfn{Target} refers to the system where the program being debugged
189 executes. In most cases they are the same machine, in which case a
190 third type of @dfn{Native} attributes come into play.
192 Defines and include files needed to build on the host are host support.
193 Examples are tty support, system defined types, host byte order, host
196 Defines and information needed to handle the target format are target
197 dependent. Examples are the stack frame format, instruction set,
198 breakpoint instruction, registers, and how to set up and tear down the stack
201 Information that is only needed when the host and target are the same,
202 is native dependent. One example is Unix child process support; if the
203 host and target are not the same, doing a fork to start the target
204 process is a bad idea. The various macros needed for finding the
205 registers in the @code{upage}, running @code{ptrace}, and such are all
206 in the native-dependent files.
208 Another example of native-dependent code is support for features that
209 are really part of the target environment, but which require
210 @code{#include} files that are only available on the host system. Core
211 file handling and @code{setjmp} handling are two common cases.
213 When you want to make @value{GDBN} work ``native'' on a particular machine, you
214 have to include all three kinds of information.
216 @section Source Tree Structure
217 @cindex @value{GDBN} source tree structure
219 The @value{GDBN} source directory has a mostly flat structure---there
220 are only a few subdirectories. A file's name usually gives a hint as
221 to what it does; for example, @file{stabsread.c} reads stabs,
222 @file{dwarfread.c} reads DWARF, etc.
224 Files that are related to some common task have names that share
225 common substrings. For example, @file{*-thread.c} files deal with
226 debugging threads on various platforms; @file{*read.c} files deal with
227 reading various kinds of symbol and object files; @file{inf*.c} files
228 deal with direct control of the @dfn{inferior program} (@value{GDBN}
229 parlance for the program being debugged).
231 There are several dozens of files in the @file{*-tdep.c} family.
232 @samp{tdep} stands for @dfn{target-dependent code}---each of these
233 files implements debug support for a specific target architecture
234 (sparc, mips, etc). Usually, only one of these will be used in a
235 specific @value{GDBN} configuration (sometimes two, closely related).
237 Similarly, there are many @file{*-nat.c} files, each one for native
238 debugging on a specific system (e.g., @file{sparc-linux-nat.c} is for
239 native debugging of Sparc machines running the Linux kernel).
241 The few subdirectories of the source tree are:
245 Code that implements @dfn{CLI}, the @value{GDBN} Command-Line
246 Interpreter. @xref{User Interface, Command Interpreter}.
249 Code for the @value{GDBN} remote server.
252 Code for Insight, the @value{GDBN} TK-based GUI front-end.
255 The @dfn{GDB/MI}, the @value{GDBN} Machine Interface interpreter.
258 Target signal translation code.
261 Code for @dfn{TUI}, the @value{GDBN} Text-mode full-screen User
262 Interface. @xref{User Interface, TUI}.
270 @value{GDBN} uses a number of debugging-specific algorithms. They are
271 often not very complicated, but get lost in the thicket of special
272 cases and real-world issues. This chapter describes the basic
273 algorithms and mentions some of the specific target definitions that
279 @cindex call stack frame
280 A frame is a construct that @value{GDBN} uses to keep track of calling
281 and called functions.
283 @cindex frame, unwind
284 @value{GDBN}'s frame model, a fresh design, was implemented with the
285 need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
286 the term ``unwind'' is taken directly from that specification.
287 Developers wishing to learn more about unwinders, are encouraged to
288 read the @sc{dwarf} specification.
290 @findex frame_register_unwind
291 @findex get_frame_register
292 @value{GDBN}'s model is that you find a frame's registers by
293 ``unwinding'' them from the next younger frame. That is,
294 @samp{get_frame_register} which returns the value of a register in
295 frame #1 (the next-to-youngest frame), is implemented by calling frame
296 #0's @code{frame_register_unwind} (the youngest frame). But then the
297 obvious question is: how do you access the registers of the youngest
300 @cindex sentinel frame
301 @findex get_frame_type
302 @vindex SENTINEL_FRAME
303 To answer this question, GDB has the @dfn{sentinel} frame, the
304 ``-1st'' frame. Unwinding registers from the sentinel frame gives you
305 the current values of the youngest real frame's registers. If @var{f}
306 is a sentinel frame, then @code{get_frame_type (@var{f}) ==
309 @section Prologue Analysis
311 @cindex prologue analysis
312 @cindex call frame information
313 @cindex CFI (call frame information)
314 To produce a backtrace and allow the user to manipulate older frames'
315 variables and arguments, @value{GDBN} needs to find the base addresses
316 of older frames, and discover where those frames' registers have been
317 saved. Since a frame's ``callee-saves'' registers get saved by
318 younger frames if and when they're reused, a frame's registers may be
319 scattered unpredictably across younger frames. This means that
320 changing the value of a register-allocated variable in an older frame
321 may actually entail writing to a save slot in some younger frame.
323 Modern versions of GCC emit Dwarf call frame information (``CFI''),
324 which describes how to find frame base addresses and saved registers.
325 But CFI is not always available, so as a fallback @value{GDBN} uses a
326 technique called @dfn{prologue analysis} to find frame sizes and saved
327 registers. A prologue analyzer disassembles the function's machine
328 code starting from its entry point, and looks for instructions that
329 allocate frame space, save the stack pointer in a frame pointer
330 register, save registers, and so on. Obviously, this can't be done
331 accurately in general, but it's tractable to do well enough to be very
332 helpful. Prologue analysis predates the GNU toolchain's support for
333 CFI; at one time, prologue analysis was the only mechanism
334 @value{GDBN} used for stack unwinding at all, when the function
335 calling conventions didn't specify a fixed frame layout.
337 In the olden days, function prologues were generated by hand-written,
338 target-specific code in GCC, and treated as opaque and untouchable by
339 optimizers. Looking at this code, it was usually straightforward to
340 write a prologue analyzer for @value{GDBN} that would accurately
341 understand all the prologues GCC would generate. However, over time
342 GCC became more aggressive about instruction scheduling, and began to
343 understand more about the semantics of the prologue instructions
344 themselves; in response, @value{GDBN}'s analyzers became more complex
345 and fragile. Keeping the prologue analyzers working as GCC (and the
346 instruction sets themselves) evolved became a substantial task.
348 @cindex @file{prologue-value.c}
349 @cindex abstract interpretation of function prologues
350 @cindex pseudo-evaluation of function prologues
351 To try to address this problem, the code in @file{prologue-value.h}
352 and @file{prologue-value.c} provides a general framework for writing
353 prologue analyzers that are simpler and more robust than ad-hoc
354 analyzers. When we analyze a prologue using the prologue-value
355 framework, we're really doing ``abstract interpretation'' or
356 ``pseudo-evaluation'': running the function's code in simulation, but
357 using conservative approximations of the values registers and memory
358 would hold when the code actually runs. For example, if our function
359 starts with the instruction:
362 addi r1, 42 # add 42 to r1
365 we don't know exactly what value will be in @code{r1} after executing
366 this instruction, but we do know it'll be 42 greater than its original
369 If we then see an instruction like:
372 addi r1, 22 # add 22 to r1
375 we still don't know what @code{r1's} value is, but again, we can say
376 it is now 64 greater than its original value.
378 If the next instruction were:
381 mov r2, r1 # set r2 to r1's value
384 then we can say that @code{r2's} value is now the original value of
387 It's common for prologues to save registers on the stack, so we'll
388 need to track the values of stack frame slots, as well as the
389 registers. So after an instruction like this:
395 then we'd know that the stack slot four bytes above the frame pointer
396 holds the original value of @code{r1} plus 64.
400 Of course, this can only go so far before it gets unreasonable. If we
401 wanted to be able to say anything about the value of @code{r1} after
405 xor r1, r3 # exclusive-or r1 and r3, place result in r1
408 then things would get pretty complex. But remember, we're just doing
409 a conservative approximation; if exclusive-or instructions aren't
410 relevant to prologues, we can just say @code{r1}'s value is now
411 ``unknown''. We can ignore things that are too complex, if that loss of
412 information is acceptable for our application.
414 So when we say ``conservative approximation'' here, what we mean is an
415 approximation that is either accurate, or marked ``unknown'', but
418 Using this framework, a prologue analyzer is simply an interpreter for
419 machine code, but one that uses conservative approximations for the
420 contents of registers and memory instead of actual values. Starting
421 from the function's entry point, you simulate instructions up to the
422 current PC, or an instruction that you don't know how to simulate.
423 Now you can examine the state of the registers and stack slots you've
429 To see how large your stack frame is, just check the value of the
430 stack pointer register; if it's the original value of the SP
431 minus a constant, then that constant is the stack frame's size.
432 If the SP's value has been marked as ``unknown'', then that means
433 the prologue has done something too complex for us to track, and
434 we don't know the frame size.
437 To see where we've saved the previous frame's registers, we just
438 search the values we've tracked --- stack slots, usually, but
439 registers, too, if you want --- for something equal to the register's
440 original value. If the calling conventions suggest a standard place
441 to save a given register, then we can check there first, but really,
442 anything that will get us back the original value will probably work.
445 This does take some work. But prologue analyzers aren't
446 quick-and-simple pattern patching to recognize a few fixed prologue
447 forms any more; they're big, hairy functions. Along with inferior
448 function calls, prologue analysis accounts for a substantial portion
449 of the time needed to stabilize a @value{GDBN} port. So it's
450 worthwhile to look for an approach that will be easier to understand
451 and maintain. In the approach described above:
456 It's easier to see that the analyzer is correct: you just see
457 whether the analyzer properly (albeit conservatively) simulates
458 the effect of each instruction.
461 It's easier to extend the analyzer: you can add support for new
462 instructions, and know that you haven't broken anything that
463 wasn't already broken before.
466 It's orthogonal: to gather new information, you don't need to
467 complicate the code for each instruction. As long as your domain
468 of conservative values is already detailed enough to tell you
469 what you need, then all the existing instruction simulations are
470 already gathering the right data for you.
474 The file @file{prologue-value.h} contains detailed comments explaining
475 the framework and how to use it.
478 @section Breakpoint Handling
481 In general, a breakpoint is a user-designated location in the program
482 where the user wants to regain control if program execution ever reaches
485 There are two main ways to implement breakpoints; either as ``hardware''
486 breakpoints or as ``software'' breakpoints.
488 @cindex hardware breakpoints
489 @cindex program counter
490 Hardware breakpoints are sometimes available as a builtin debugging
491 features with some chips. Typically these work by having dedicated
492 register into which the breakpoint address may be stored. If the PC
493 (shorthand for @dfn{program counter})
494 ever matches a value in a breakpoint registers, the CPU raises an
495 exception and reports it to @value{GDBN}.
497 Another possibility is when an emulator is in use; many emulators
498 include circuitry that watches the address lines coming out from the
499 processor, and force it to stop if the address matches a breakpoint's
502 A third possibility is that the target already has the ability to do
503 breakpoints somehow; for instance, a ROM monitor may do its own
504 software breakpoints. So although these are not literally ``hardware
505 breakpoints'', from @value{GDBN}'s point of view they work the same;
506 @value{GDBN} need not do anything more than set the breakpoint and wait
507 for something to happen.
509 Since they depend on hardware resources, hardware breakpoints may be
510 limited in number; when the user asks for more, @value{GDBN} will
511 start trying to set software breakpoints. (On some architectures,
512 notably the 32-bit x86 platforms, @value{GDBN} cannot always know
513 whether there's enough hardware resources to insert all the hardware
514 breakpoints and watchpoints. On those platforms, @value{GDBN} prints
515 an error message only when the program being debugged is continued.)
517 @cindex software breakpoints
518 Software breakpoints require @value{GDBN} to do somewhat more work.
519 The basic theory is that @value{GDBN} will replace a program
520 instruction with a trap, illegal divide, or some other instruction
521 that will cause an exception, and then when it's encountered,
522 @value{GDBN} will take the exception and stop the program. When the
523 user says to continue, @value{GDBN} will restore the original
524 instruction, single-step, re-insert the trap, and continue on.
526 Since it literally overwrites the program being tested, the program area
527 must be writable, so this technique won't work on programs in ROM. It
528 can also distort the behavior of programs that examine themselves,
529 although such a situation would be highly unusual.
531 Also, the software breakpoint instruction should be the smallest size of
532 instruction, so it doesn't overwrite an instruction that might be a jump
533 target, and cause disaster when the program jumps into the middle of the
534 breakpoint instruction. (Strictly speaking, the breakpoint must be no
535 larger than the smallest interval between instructions that may be jump
536 targets; perhaps there is an architecture where only even-numbered
537 instructions may jumped to.) Note that it's possible for an instruction
538 set not to have any instructions usable for a software breakpoint,
539 although in practice only the ARC has failed to define such an
543 The basic definition of the software breakpoint is the macro
546 Basic breakpoint object handling is in @file{breakpoint.c}. However,
547 much of the interesting breakpoint action is in @file{infrun.c}.
550 @cindex insert or remove software breakpoint
551 @findex target_remove_breakpoint
552 @findex target_insert_breakpoint
553 @item target_remove_breakpoint (@var{bp_tgt})
554 @itemx target_insert_breakpoint (@var{bp_tgt})
555 Insert or remove a software breakpoint at address
556 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
557 non-zero for failure. On input, @var{bp_tgt} contains the address of the
558 breakpoint, and is otherwise initialized to zero. The fields of the
559 @code{struct bp_target_info} pointed to by @var{bp_tgt} are updated
560 to contain other information about the breakpoint on output. The field
561 @code{placed_address} may be updated if the breakpoint was placed at a
562 related address; the field @code{shadow_contents} contains the real
563 contents of the bytes where the breakpoint has been inserted,
564 if reading memory would return the breakpoint instead of the
565 underlying memory; the field @code{shadow_len} is the length of
566 memory cached in @code{shadow_contents}, if any; and the field
567 @code{placed_size} is optionally set and used by the target, if
568 it could differ from @code{shadow_len}.
570 For example, the remote target @samp{Z0} packet does not require
571 shadowing memory, so @code{shadow_len} is left at zero. However,
572 the length reported by @code{BREAKPOINT_FROM_PC} is cached in
573 @code{placed_size}, so that a matching @samp{z0} packet can be
574 used to remove the breakpoint.
576 @cindex insert or remove hardware breakpoint
577 @findex target_remove_hw_breakpoint
578 @findex target_insert_hw_breakpoint
579 @item target_remove_hw_breakpoint (@var{bp_tgt})
580 @itemx target_insert_hw_breakpoint (@var{bp_tgt})
581 Insert or remove a hardware-assisted breakpoint at address
582 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
583 non-zero for failure. See @code{target_insert_breakpoint} for
584 a description of the @code{struct bp_target_info} pointed to by
585 @var{bp_tgt}; the @code{shadow_contents} and
586 @code{shadow_len} members are not used for hardware breakpoints,
587 but @code{placed_size} may be.
590 @section Single Stepping
592 @section Signal Handling
594 @section Thread Handling
596 @section Inferior Function Calls
598 @section Longjmp Support
600 @cindex @code{longjmp} debugging
601 @value{GDBN} has support for figuring out that the target is doing a
602 @code{longjmp} and for stopping at the target of the jump, if we are
603 stepping. This is done with a few specialized internal breakpoints,
604 which are visible in the output of the @samp{maint info breakpoint}
607 @findex GET_LONGJMP_TARGET
608 To make this work, you need to define a macro called
609 @code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
610 structure and extract the longjmp target address. Since @code{jmp_buf}
611 is target specific, you will need to define it in the appropriate
612 @file{tm-@var{target}.h} file. Look in @file{tm-sun4os4.h} and
613 @file{sparc-tdep.c} for examples of how to do this.
618 Watchpoints are a special kind of breakpoints (@pxref{Algorithms,
619 breakpoints}) which break when data is accessed rather than when some
620 instruction is executed. When you have data which changes without
621 your knowing what code does that, watchpoints are the silver bullet to
622 hunt down and kill such bugs.
624 @cindex hardware watchpoints
625 @cindex software watchpoints
626 Watchpoints can be either hardware-assisted or not; the latter type is
627 known as ``software watchpoints.'' @value{GDBN} always uses
628 hardware-assisted watchpoints if they are available, and falls back on
629 software watchpoints otherwise. Typical situations where @value{GDBN}
630 will use software watchpoints are:
634 The watched memory region is too large for the underlying hardware
635 watchpoint support. For example, each x86 debug register can watch up
636 to 4 bytes of memory, so trying to watch data structures whose size is
637 more than 16 bytes will cause @value{GDBN} to use software
641 The value of the expression to be watched depends on data held in
642 registers (as opposed to memory).
645 Too many different watchpoints requested. (On some architectures,
646 this situation is impossible to detect until the debugged program is
647 resumed.) Note that x86 debug registers are used both for hardware
648 breakpoints and for watchpoints, so setting too many hardware
649 breakpoints might cause watchpoint insertion to fail.
652 No hardware-assisted watchpoints provided by the target
656 Software watchpoints are very slow, since @value{GDBN} needs to
657 single-step the program being debugged and test the value of the
658 watched expression(s) after each instruction. The rest of this
659 section is mostly irrelevant for software watchpoints.
661 When the inferior stops, @value{GDBN} tries to establish, among other
662 possible reasons, whether it stopped due to a watchpoint being hit.
663 For a data-write watchpoint, it does so by evaluating, for each
664 watchpoint, the expression whose value is being watched, and testing
665 whether the watched value has changed. For data-read and data-access
666 watchpoints, @value{GDBN} needs the target to supply a primitive that
667 returns the address of the data that was accessed or read (see the
668 description of @code{target_stopped_data_address} below): if this
669 primitive returns a valid address, @value{GDBN} infers that a
670 watchpoint triggered if it watches an expression whose evaluation uses
673 @value{GDBN} uses several macros and primitives to support hardware
677 @findex TARGET_HAS_HARDWARE_WATCHPOINTS
678 @item TARGET_HAS_HARDWARE_WATCHPOINTS
679 If defined, the target supports hardware watchpoints.
681 @findex TARGET_CAN_USE_HARDWARE_WATCHPOINT
682 @item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other})
683 Return the number of hardware watchpoints of type @var{type} that are
684 possible to be set. The value is positive if @var{count} watchpoints
685 of this type can be set, zero if setting watchpoints of this type is
686 not supported, and negative if @var{count} is more than the maximum
687 number of watchpoints of type @var{type} that can be set. @var{other}
688 is non-zero if other types of watchpoints are currently enabled (there
689 are architectures which cannot set watchpoints of different types at
692 @findex TARGET_REGION_OK_FOR_HW_WATCHPOINT
693 @item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len})
694 Return non-zero if hardware watchpoints can be used to watch a region
695 whose address is @var{addr} and whose length in bytes is @var{len}.
697 @cindex insert or remove hardware watchpoint
698 @findex target_insert_watchpoint
699 @findex target_remove_watchpoint
700 @item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
701 @itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type})
702 Insert or remove a hardware watchpoint starting at @var{addr}, for
703 @var{len} bytes. @var{type} is the watchpoint type, one of the
704 possible values of the enumerated data type @code{target_hw_bp_type},
705 defined by @file{breakpoint.h} as follows:
708 enum target_hw_bp_type
710 hw_write = 0, /* Common (write) HW watchpoint */
711 hw_read = 1, /* Read HW watchpoint */
712 hw_access = 2, /* Access (read or write) HW watchpoint */
713 hw_execute = 3 /* Execute HW breakpoint */
718 These two macros should return 0 for success, non-zero for failure.
720 @findex target_stopped_data_address
721 @item target_stopped_data_address (@var{addr_p})
722 If the inferior has some watchpoint that triggered, place the address
723 associated with the watchpoint at the location pointed to by
724 @var{addr_p} and return non-zero. Otherwise, return zero. Note that
725 this primitive is used by @value{GDBN} only on targets that support
726 data-read or data-access type watchpoints, so targets that have
727 support only for data-write watchpoints need not implement these
730 @findex HAVE_STEPPABLE_WATCHPOINT
731 @item HAVE_STEPPABLE_WATCHPOINT
732 If defined to a non-zero value, it is not necessary to disable a
733 watchpoint to step over it.
735 @findex HAVE_NONSTEPPABLE_WATCHPOINT
736 @item HAVE_NONSTEPPABLE_WATCHPOINT
737 If defined to a non-zero value, @value{GDBN} should disable a
738 watchpoint to step the inferior over it.
740 @findex HAVE_CONTINUABLE_WATCHPOINT
741 @item HAVE_CONTINUABLE_WATCHPOINT
742 If defined to a non-zero value, it is possible to continue the
743 inferior after a watchpoint has been hit.
745 @findex CANNOT_STEP_HW_WATCHPOINTS
746 @item CANNOT_STEP_HW_WATCHPOINTS
747 If this is defined to a non-zero value, @value{GDBN} will remove all
748 watchpoints before stepping the inferior.
750 @findex STOPPED_BY_WATCHPOINT
751 @item STOPPED_BY_WATCHPOINT (@var{wait_status})
752 Return non-zero if stopped by a watchpoint. @var{wait_status} is of
753 the type @code{struct target_waitstatus}, defined by @file{target.h}.
754 Normally, this macro is defined to invoke the function pointed to by
755 the @code{to_stopped_by_watchpoint} member of the structure (of the
756 type @code{target_ops}, defined on @file{target.h}) that describes the
757 target-specific operations; @code{to_stopped_by_watchpoint} ignores
758 the @var{wait_status} argument.
760 @value{GDBN} does not require the non-zero value returned by
761 @code{STOPPED_BY_WATCHPOINT} to be 100% correct, so if a target cannot
762 determine for sure whether the inferior stopped due to a watchpoint,
763 it could return non-zero ``just in case''.
766 @subsection x86 Watchpoints
767 @cindex x86 debug registers
768 @cindex watchpoints, on x86
770 The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug
771 registers designed to facilitate debugging. @value{GDBN} provides a
772 generic library of functions that x86-based ports can use to implement
773 support for watchpoints and hardware-assisted breakpoints. This
774 subsection documents the x86 watchpoint facilities in @value{GDBN}.
776 To use the generic x86 watchpoint support, a port should do the
780 @findex I386_USE_GENERIC_WATCHPOINTS
782 Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the
783 target-dependent headers.
786 Include the @file{config/i386/nm-i386.h} header file @emph{after}
787 defining @code{I386_USE_GENERIC_WATCHPOINTS}.
790 Add @file{i386-nat.o} to the value of the Make variable
791 @code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}) or
792 @code{TDEPFILES} (@pxref{Target Architecture Definition, TDEPFILES}).
795 Provide implementations for the @code{I386_DR_LOW_*} macros described
796 below. Typically, each macro should call a target-specific function
797 which does the real work.
800 The x86 watchpoint support works by maintaining mirror images of the
801 debug registers. Values are copied between the mirror images and the
802 real debug registers via a set of macros which each target needs to
806 @findex I386_DR_LOW_SET_CONTROL
807 @item I386_DR_LOW_SET_CONTROL (@var{val})
808 Set the Debug Control (DR7) register to the value @var{val}.
810 @findex I386_DR_LOW_SET_ADDR
811 @item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr})
812 Put the address @var{addr} into the debug register number @var{idx}.
814 @findex I386_DR_LOW_RESET_ADDR
815 @item I386_DR_LOW_RESET_ADDR (@var{idx})
816 Reset (i.e.@: zero out) the address stored in the debug register
819 @findex I386_DR_LOW_GET_STATUS
820 @item I386_DR_LOW_GET_STATUS
821 Return the value of the Debug Status (DR6) register. This value is
822 used immediately after it is returned by
823 @code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status
827 For each one of the 4 debug registers (whose indices are from 0 to 3)
828 that store addresses, a reference count is maintained by @value{GDBN},
829 to allow sharing of debug registers by several watchpoints. This
830 allows users to define several watchpoints that watch the same
831 expression, but with different conditions and/or commands, without
832 wasting debug registers which are in short supply. @value{GDBN}
833 maintains the reference counts internally, targets don't have to do
834 anything to use this feature.
836 The x86 debug registers can each watch a region that is 1, 2, or 4
837 bytes long. The ia32 architecture requires that each watched region
838 be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte
839 region on 4-byte boundary. However, the x86 watchpoint support in
840 @value{GDBN} can watch unaligned regions and regions larger than 4
841 bytes (up to 16 bytes) by allocating several debug registers to watch
842 a single region. This allocation of several registers per a watched
843 region is also done automatically without target code intervention.
845 The generic x86 watchpoint support provides the following API for the
846 @value{GDBN}'s application code:
849 @findex i386_region_ok_for_watchpoint
850 @item i386_region_ok_for_watchpoint (@var{addr}, @var{len})
851 The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call
852 this function. It counts the number of debug registers required to
853 watch a given region, and returns a non-zero value if that number is
854 less than 4, the number of debug registers available to x86
857 @findex i386_stopped_data_address
858 @item i386_stopped_data_address (@var{addr_p})
860 @code{target_stopped_data_address} is set to call this function.
862 function examines the breakpoint condition bits in the DR6 Debug
863 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
864 macro, and returns the address associated with the first bit that is
867 @findex i386_stopped_by_watchpoint
868 @item i386_stopped_by_watchpoint (void)
869 The macro @code{STOPPED_BY_WATCHPOINT}
870 is set to call this function. The
871 argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This
872 function examines the breakpoint condition bits in the DR6 Debug
873 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
874 macro, and returns true if any bit is set. Otherwise, false is
877 @findex i386_insert_watchpoint
878 @findex i386_remove_watchpoint
879 @item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type})
880 @itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type})
881 Insert or remove a watchpoint. The macros
882 @code{target_insert_watchpoint} and @code{target_remove_watchpoint}
883 are set to call these functions. @code{i386_insert_watchpoint} first
884 looks for a debug register which is already set to watch the same
885 region for the same access types; if found, it just increments the
886 reference count of that debug register, thus implementing debug
887 register sharing between watchpoints. If no such register is found,
888 the function looks for a vacant debug register, sets its mirrored
889 value to @var{addr}, sets the mirrored value of DR7 Debug Control
890 register as appropriate for the @var{len} and @var{type} parameters,
891 and then passes the new values of the debug register and DR7 to the
892 inferior by calling @code{I386_DR_LOW_SET_ADDR} and
893 @code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is
894 required to cover the given region, the above process is repeated for
897 @code{i386_remove_watchpoint} does the opposite: it resets the address
898 in the mirrored value of the debug register and its read/write and
899 length bits in the mirrored value of DR7, then passes these new
900 values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and
901 @code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several
902 watchpoints, each time a @code{i386_remove_watchpoint} is called, it
903 decrements the reference count, and only calls
904 @code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when
905 the count goes to zero.
907 @findex i386_insert_hw_breakpoint
908 @findex i386_remove_hw_breakpoint
909 @item i386_insert_hw_breakpoint (@var{bp_tgt})
910 @itemx i386_remove_hw_breakpoint (@var{bp_tgt})
911 These functions insert and remove hardware-assisted breakpoints. The
912 macros @code{target_insert_hw_breakpoint} and
913 @code{target_remove_hw_breakpoint} are set to call these functions.
914 The argument is a @code{struct bp_target_info *}, as described in
915 the documentation for @code{target_insert_breakpoint}.
916 These functions work like @code{i386_insert_watchpoint} and
917 @code{i386_remove_watchpoint}, respectively, except that they set up
918 the debug registers to watch instruction execution, and each
919 hardware-assisted breakpoint always requires exactly one debug
922 @findex i386_stopped_by_hwbp
923 @item i386_stopped_by_hwbp (void)
924 This function returns non-zero if the inferior has some watchpoint or
925 hardware breakpoint that triggered. It works like
926 @code{i386_stopped_data_address}, except that it doesn't record the
927 address whose watchpoint triggered.
929 @findex i386_cleanup_dregs
930 @item i386_cleanup_dregs (void)
931 This function clears all the reference counts, addresses, and control
932 bits in the mirror images of the debug registers. It doesn't affect
933 the actual debug registers in the inferior process.
940 x86 processors support setting watchpoints on I/O reads or writes.
941 However, since no target supports this (as of March 2001), and since
942 @code{enum target_hw_bp_type} doesn't even have an enumeration for I/O
943 watchpoints, this feature is not yet available to @value{GDBN} running
947 x86 processors can enable watchpoints locally, for the current task
948 only, or globally, for all the tasks. For each debug register,
949 there's a bit in the DR7 Debug Control register that determines
950 whether the associated address is watched locally or globally. The
951 current implementation of x86 watchpoint support in @value{GDBN}
952 always sets watchpoints to be locally enabled, since global
953 watchpoints might interfere with the underlying OS and are probably
954 unavailable in many platforms.
960 In the abstract, a checkpoint is a point in the execution history of
961 the program, which the user may wish to return to at some later time.
963 Internally, a checkpoint is a saved copy of the program state, including
964 whatever information is required in order to restore the program to that
965 state at a later time. This can be expected to include the state of
966 registers and memory, and may include external state such as the state
967 of open files and devices.
969 There are a number of ways in which checkpoints may be implemented
970 in gdb, e.g.@: as corefiles, as forked processes, and as some opaque
971 method implemented on the target side.
973 A corefile can be used to save an image of target memory and register
974 state, which can in principle be restored later --- but corefiles do
975 not typically include information about external entities such as
976 open files. Currently this method is not implemented in gdb.
978 A forked process can save the state of user memory and registers,
979 as well as some subset of external (kernel) state. This method
980 is used to implement checkpoints on Linux, and in principle might
981 be used on other systems.
983 Some targets, e.g.@: simulators, might have their own built-in
984 method for saving checkpoints, and gdb might be able to take
985 advantage of that capability without necessarily knowing any
986 details of how it is done.
989 @section Observing changes in @value{GDBN} internals
990 @cindex observer pattern interface
991 @cindex notifications about changes in internals
993 In order to function properly, several modules need to be notified when
994 some changes occur in the @value{GDBN} internals. Traditionally, these
995 modules have relied on several paradigms, the most common ones being
996 hooks and gdb-events. Unfortunately, none of these paradigms was
997 versatile enough to become the standard notification mechanism in
998 @value{GDBN}. The fact that they only supported one ``client'' was also
1001 A new paradigm, based on the Observer pattern of the @cite{Design
1002 Patterns} book, has therefore been implemented. The goal was to provide
1003 a new interface overcoming the issues with the notification mechanisms
1004 previously available. This new interface needed to be strongly typed,
1005 easy to extend, and versatile enough to be used as the standard
1006 interface when adding new notifications.
1008 See @ref{GDB Observers} for a brief description of the observers
1009 currently implemented in GDB. The rationale for the current
1010 implementation is also briefly discussed.
1012 @node User Interface
1014 @chapter User Interface
1016 @value{GDBN} has several user interfaces. Although the command-line interface
1017 is the most common and most familiar, there are others.
1019 @section Command Interpreter
1021 @cindex command interpreter
1023 The command interpreter in @value{GDBN} is fairly simple. It is designed to
1024 allow for the set of commands to be augmented dynamically, and also
1025 has a recursive subcommand capability, where the first argument to
1026 a command may itself direct a lookup on a different command list.
1028 For instance, the @samp{set} command just starts a lookup on the
1029 @code{setlist} command list, while @samp{set thread} recurses
1030 to the @code{set_thread_cmd_list}.
1034 To add commands in general, use @code{add_cmd}. @code{add_com} adds to
1035 the main command list, and should be used for those commands. The usual
1036 place to add commands is in the @code{_initialize_@var{xyz}} routines at
1037 the ends of most source files.
1039 @findex add_setshow_cmd
1040 @findex add_setshow_cmd_full
1041 To add paired @samp{set} and @samp{show} commands, use
1042 @code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is
1043 a slightly simpler interface which is useful when you don't need to
1044 further modify the new command structures, while the latter returns
1045 the new command structures for manipulation.
1047 @cindex deprecating commands
1048 @findex deprecate_cmd
1049 Before removing commands from the command set it is a good idea to
1050 deprecate them for some time. Use @code{deprecate_cmd} on commands or
1051 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
1052 @code{struct cmd_list_element} as it's first argument. You can use the
1053 return value from @code{add_com} or @code{add_cmd} to deprecate the
1054 command immediately after it is created.
1056 The first time a command is used the user will be warned and offered a
1057 replacement (if one exists). Note that the replacement string passed to
1058 @code{deprecate_cmd} should be the full name of the command, i.e., the
1059 entire string the user should type at the command line.
1061 @section UI-Independent Output---the @code{ui_out} Functions
1062 @c This section is based on the documentation written by Fernando
1063 @c Nasser <fnasser@redhat.com>.
1065 @cindex @code{ui_out} functions
1066 The @code{ui_out} functions present an abstraction level for the
1067 @value{GDBN} output code. They hide the specifics of different user
1068 interfaces supported by @value{GDBN}, and thus free the programmer
1069 from the need to write several versions of the same code, one each for
1070 every UI, to produce output.
1072 @subsection Overview and Terminology
1074 In general, execution of each @value{GDBN} command produces some sort
1075 of output, and can even generate an input request.
1077 Output can be generated for the following purposes:
1081 to display a @emph{result} of an operation;
1084 to convey @emph{info} or produce side-effects of a requested
1088 to provide a @emph{notification} of an asynchronous event (including
1089 progress indication of a prolonged asynchronous operation);
1092 to display @emph{error messages} (including warnings);
1095 to show @emph{debug data};
1098 to @emph{query} or prompt a user for input (a special case).
1102 This section mainly concentrates on how to build result output,
1103 although some of it also applies to other kinds of output.
1105 Generation of output that displays the results of an operation
1106 involves one or more of the following:
1110 output of the actual data
1113 formatting the output as appropriate for console output, to make it
1114 easily readable by humans
1117 machine oriented formatting--a more terse formatting to allow for easy
1118 parsing by programs which read @value{GDBN}'s output
1121 annotation, whose purpose is to help legacy GUIs to identify interesting
1125 The @code{ui_out} routines take care of the first three aspects.
1126 Annotations are provided by separate annotation routines. Note that use
1127 of annotations for an interface between a GUI and @value{GDBN} is
1130 Output can be in the form of a single item, which we call a @dfn{field};
1131 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
1132 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
1133 header and a body. In a BNF-like form:
1136 @item <table> @expansion{}
1137 @code{<header> <body>}
1138 @item <header> @expansion{}
1139 @code{@{ <column> @}}
1140 @item <column> @expansion{}
1141 @code{<width> <alignment> <title>}
1142 @item <body> @expansion{}
1147 @subsection General Conventions
1149 Most @code{ui_out} routines are of type @code{void}, the exceptions are
1150 @code{ui_out_stream_new} (which returns a pointer to the newly created
1151 object) and the @code{make_cleanup} routines.
1153 The first parameter is always the @code{ui_out} vector object, a pointer
1154 to a @code{struct ui_out}.
1156 The @var{format} parameter is like in @code{printf} family of functions.
1157 When it is present, there must also be a variable list of arguments
1158 sufficient used to satisfy the @code{%} specifiers in the supplied
1161 When a character string argument is not used in a @code{ui_out} function
1162 call, a @code{NULL} pointer has to be supplied instead.
1165 @subsection Table, Tuple and List Functions
1167 @cindex list output functions
1168 @cindex table output functions
1169 @cindex tuple output functions
1170 This section introduces @code{ui_out} routines for building lists,
1171 tuples and tables. The routines to output the actual data items
1172 (fields) are presented in the next section.
1174 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
1175 containing information about an object; a @dfn{list} is a sequence of
1176 fields where each field describes an identical object.
1178 Use the @dfn{table} functions when your output consists of a list of
1179 rows (tuples) and the console output should include a heading. Use this
1180 even when you are listing just one object but you still want the header.
1182 @cindex nesting level in @code{ui_out} functions
1183 Tables can not be nested. Tuples and lists can be nested up to a
1184 maximum of five levels.
1186 The overall structure of the table output code is something like this:
1201 Here is the description of table-, tuple- and list-related @code{ui_out}
1204 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
1205 The function @code{ui_out_table_begin} marks the beginning of the output
1206 of a table. It should always be called before any other @code{ui_out}
1207 function for a given table. @var{nbrofcols} is the number of columns in
1208 the table. @var{nr_rows} is the number of rows in the table.
1209 @var{tblid} is an optional string identifying the table. The string
1210 pointed to by @var{tblid} is copied by the implementation of
1211 @code{ui_out_table_begin}, so the application can free the string if it
1212 was @code{malloc}ed.
1214 The companion function @code{ui_out_table_end}, described below, marks
1215 the end of the table's output.
1218 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
1219 @code{ui_out_table_header} provides the header information for a single
1220 table column. You call this function several times, one each for every
1221 column of the table, after @code{ui_out_table_begin}, but before
1222 @code{ui_out_table_body}.
1224 The value of @var{width} gives the column width in characters. The
1225 value of @var{alignment} is one of @code{left}, @code{center}, and
1226 @code{right}, and it specifies how to align the header: left-justify,
1227 center, or right-justify it. @var{colhdr} points to a string that
1228 specifies the column header; the implementation copies that string, so
1229 column header strings in @code{malloc}ed storage can be freed after the
1233 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
1234 This function delimits the table header from the table body.
1237 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
1238 This function signals the end of a table's output. It should be called
1239 after the table body has been produced by the list and field output
1242 There should be exactly one call to @code{ui_out_table_end} for each
1243 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
1244 will signal an internal error.
1247 The output of the tuples that represent the table rows must follow the
1248 call to @code{ui_out_table_body} and precede the call to
1249 @code{ui_out_table_end}. You build a tuple by calling
1250 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
1251 calls to functions which actually output fields between them.
1253 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
1254 This function marks the beginning of a tuple output. @var{id} points
1255 to an optional string that identifies the tuple; it is copied by the
1256 implementation, and so strings in @code{malloc}ed storage can be freed
1260 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
1261 This function signals an end of a tuple output. There should be exactly
1262 one call to @code{ui_out_tuple_end} for each call to
1263 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
1267 @deftypefun struct cleanup *make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1268 This function first opens the tuple and then establishes a cleanup
1269 (@pxref{Coding, Cleanups}) to close the tuple. It provides a convenient
1270 and correct implementation of the non-portable@footnote{The function
1271 cast is not portable ISO C.} code sequence:
1273 struct cleanup *old_cleanup;
1274 ui_out_tuple_begin (uiout, "...");
1275 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
1280 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
1281 This function marks the beginning of a list output. @var{id} points to
1282 an optional string that identifies the list; it is copied by the
1283 implementation, and so strings in @code{malloc}ed storage can be freed
1287 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
1288 This function signals an end of a list output. There should be exactly
1289 one call to @code{ui_out_list_end} for each call to
1290 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
1294 @deftypefun struct cleanup *make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1295 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
1296 opens a list and then establishes cleanup (@pxref{Coding, Cleanups})
1297 that will close the list.list.
1300 @subsection Item Output Functions
1302 @cindex item output functions
1303 @cindex field output functions
1305 The functions described below produce output for the actual data
1306 items, or fields, which contain information about the object.
1308 Choose the appropriate function accordingly to your particular needs.
1310 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
1311 This is the most general output function. It produces the
1312 representation of the data in the variable-length argument list
1313 according to formatting specifications in @var{format}, a
1314 @code{printf}-like format string. The optional argument @var{fldname}
1315 supplies the name of the field. The data items themselves are
1316 supplied as additional arguments after @var{format}.
1318 This generic function should be used only when it is not possible to
1319 use one of the specialized versions (see below).
1322 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1323 This function outputs a value of an @code{int} variable. It uses the
1324 @code{"%d"} output conversion specification. @var{fldname} specifies
1325 the name of the field.
1328 @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})
1329 This function outputs a value of an @code{int} variable. It differs from
1330 @code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output.
1331 @var{fldname} specifies
1332 the name of the field.
1335 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, CORE_ADDR @var{address})
1336 This function outputs an address.
1339 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1340 This function outputs a string using the @code{"%s"} conversion
1344 Sometimes, there's a need to compose your output piece by piece using
1345 functions that operate on a stream, such as @code{value_print} or
1346 @code{fprintf_symbol_filtered}. These functions accept an argument of
1347 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1348 used to store the data stream used for the output. When you use one
1349 of these functions, you need a way to pass their results stored in a
1350 @code{ui_file} object to the @code{ui_out} functions. To this end,
1351 you first create a @code{ui_stream} object by calling
1352 @code{ui_out_stream_new}, pass the @code{stream} member of that
1353 @code{ui_stream} object to @code{value_print} and similar functions,
1354 and finally call @code{ui_out_field_stream} to output the field you
1355 constructed. When the @code{ui_stream} object is no longer needed,
1356 you should destroy it and free its memory by calling
1357 @code{ui_out_stream_delete}.
1359 @deftypefun struct ui_stream *ui_out_stream_new (struct ui_out *@var{uiout})
1360 This function creates a new @code{ui_stream} object which uses the
1361 same output methods as the @code{ui_out} object whose pointer is
1362 passed in @var{uiout}. It returns a pointer to the newly created
1363 @code{ui_stream} object.
1366 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1367 This functions destroys a @code{ui_stream} object specified by
1371 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1372 This function consumes all the data accumulated in
1373 @code{streambuf->stream} and outputs it like
1374 @code{ui_out_field_string} does. After a call to
1375 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1376 the stream is still valid and may be used for producing more fields.
1379 @strong{Important:} If there is any chance that your code could bail
1380 out before completing output generation and reaching the point where
1381 @code{ui_out_stream_delete} is called, it is necessary to set up a
1382 cleanup, to avoid leaking memory and other resources. Here's a
1383 skeleton code to do that:
1386 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1387 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1392 If the function already has the old cleanup chain set (for other kinds
1393 of cleanups), you just have to add your cleanup to it:
1396 mybuf = ui_out_stream_new (uiout);
1397 make_cleanup (ui_out_stream_delete, mybuf);
1400 Note that with cleanups in place, you should not call
1401 @code{ui_out_stream_delete} directly, or you would attempt to free the
1404 @subsection Utility Output Functions
1406 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1407 This function skips a field in a table. Use it if you have to leave
1408 an empty field without disrupting the table alignment. The argument
1409 @var{fldname} specifies a name for the (missing) filed.
1412 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1413 This function outputs the text in @var{string} in a way that makes it
1414 easy to be read by humans. For example, the console implementation of
1415 this method filters the text through a built-in pager, to prevent it
1416 from scrolling off the visible portion of the screen.
1418 Use this function for printing relatively long chunks of text around
1419 the actual field data: the text it produces is not aligned according
1420 to the table's format. Use @code{ui_out_field_string} to output a
1421 string field, and use @code{ui_out_message}, described below, to
1422 output short messages.
1425 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1426 This function outputs @var{nspaces} spaces. It is handy to align the
1427 text produced by @code{ui_out_text} with the rest of the table or
1431 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1432 This function produces a formatted message, provided that the current
1433 verbosity level is at least as large as given by @var{verbosity}. The
1434 current verbosity level is specified by the user with the @samp{set
1435 verbositylevel} command.@footnote{As of this writing (April 2001),
1436 setting verbosity level is not yet implemented, and is always returned
1437 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1438 argument more than zero will cause the message to never be printed.}
1441 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1442 This function gives the console output filter (a paging filter) a hint
1443 of where to break lines which are too long. Ignored for all other
1444 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1445 be printed to indent the wrapped text on the next line; it must remain
1446 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1447 explicit newline is produced by one of the other functions. If
1448 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1451 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1452 This function flushes whatever output has been accumulated so far, if
1453 the UI buffers output.
1457 @subsection Examples of Use of @code{ui_out} functions
1459 @cindex using @code{ui_out} functions
1460 @cindex @code{ui_out} functions, usage examples
1461 This section gives some practical examples of using the @code{ui_out}
1462 functions to generalize the old console-oriented code in
1463 @value{GDBN}. The examples all come from functions defined on the
1464 @file{breakpoints.c} file.
1466 This example, from the @code{breakpoint_1} function, shows how to
1469 The original code was:
1472 if (!found_a_breakpoint++)
1474 annotate_breakpoints_headers ();
1477 printf_filtered ("Num ");
1479 printf_filtered ("Type ");
1481 printf_filtered ("Disp ");
1483 printf_filtered ("Enb ");
1487 printf_filtered ("Address ");
1490 printf_filtered ("What\n");
1492 annotate_breakpoints_table ();
1496 Here's the new version:
1499 nr_printable_breakpoints = @dots{};
1502 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1504 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1506 if (nr_printable_breakpoints > 0)
1507 annotate_breakpoints_headers ();
1508 if (nr_printable_breakpoints > 0)
1510 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1511 if (nr_printable_breakpoints > 0)
1513 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1514 if (nr_printable_breakpoints > 0)
1516 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1517 if (nr_printable_breakpoints > 0)
1519 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1522 if (nr_printable_breakpoints > 0)
1524 if (TARGET_ADDR_BIT <= 32)
1525 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1527 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1529 if (nr_printable_breakpoints > 0)
1531 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1532 ui_out_table_body (uiout);
1533 if (nr_printable_breakpoints > 0)
1534 annotate_breakpoints_table ();
1537 This example, from the @code{print_one_breakpoint} function, shows how
1538 to produce the actual data for the table whose structure was defined
1539 in the above example. The original code was:
1544 printf_filtered ("%-3d ", b->number);
1546 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1547 || ((int) b->type != bptypes[(int) b->type].type))
1548 internal_error ("bptypes table does not describe type #%d.",
1550 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1552 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1554 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1558 This is the new version:
1562 ui_out_tuple_begin (uiout, "bkpt");
1564 ui_out_field_int (uiout, "number", b->number);
1566 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1567 || ((int) b->type != bptypes[(int) b->type].type))
1568 internal_error ("bptypes table does not describe type #%d.",
1570 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1572 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1574 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1578 This example, also from @code{print_one_breakpoint}, shows how to
1579 produce a complicated output field using the @code{print_expression}
1580 functions which requires a stream to be passed. It also shows how to
1581 automate stream destruction with cleanups. The original code was:
1585 print_expression (b->exp, gdb_stdout);
1591 struct ui_stream *stb = ui_out_stream_new (uiout);
1592 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1595 print_expression (b->exp, stb->stream);
1596 ui_out_field_stream (uiout, "what", local_stream);
1599 This example, also from @code{print_one_breakpoint}, shows how to use
1600 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1605 if (b->dll_pathname == NULL)
1606 printf_filtered ("<any library> ");
1608 printf_filtered ("library \"%s\" ", b->dll_pathname);
1615 if (b->dll_pathname == NULL)
1617 ui_out_field_string (uiout, "what", "<any library>");
1618 ui_out_spaces (uiout, 1);
1622 ui_out_text (uiout, "library \"");
1623 ui_out_field_string (uiout, "what", b->dll_pathname);
1624 ui_out_text (uiout, "\" ");
1628 The following example from @code{print_one_breakpoint} shows how to
1629 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1634 if (b->forked_inferior_pid != 0)
1635 printf_filtered ("process %d ", b->forked_inferior_pid);
1642 if (b->forked_inferior_pid != 0)
1644 ui_out_text (uiout, "process ");
1645 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1646 ui_out_spaces (uiout, 1);
1650 Here's an example of using @code{ui_out_field_string}. The original
1655 if (b->exec_pathname != NULL)
1656 printf_filtered ("program \"%s\" ", b->exec_pathname);
1663 if (b->exec_pathname != NULL)
1665 ui_out_text (uiout, "program \"");
1666 ui_out_field_string (uiout, "what", b->exec_pathname);
1667 ui_out_text (uiout, "\" ");
1671 Finally, here's an example of printing an address. The original code:
1675 printf_filtered ("%s ",
1676 hex_string_custom ((unsigned long) b->address, 8));
1683 ui_out_field_core_addr (uiout, "Address", b->address);
1687 @section Console Printing
1696 @cindex @code{libgdb}
1697 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1698 to provide an API to @value{GDBN}'s functionality.
1701 @cindex @code{libgdb}
1702 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1703 better able to support graphical and other environments.
1705 Since @code{libgdb} development is on-going, its architecture is still
1706 evolving. The following components have so far been identified:
1710 Observer - @file{gdb-events.h}.
1712 Builder - @file{ui-out.h}
1714 Event Loop - @file{event-loop.h}
1716 Library - @file{gdb.h}
1719 The model that ties these components together is described below.
1721 @section The @code{libgdb} Model
1723 A client of @code{libgdb} interacts with the library in two ways.
1727 As an observer (using @file{gdb-events}) receiving notifications from
1728 @code{libgdb} of any internal state changes (break point changes, run
1731 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1732 obtain various status values from @value{GDBN}.
1735 Since @code{libgdb} could have multiple clients (e.g., a GUI supporting
1736 the existing @value{GDBN} CLI), those clients must co-operate when
1737 controlling @code{libgdb}. In particular, a client must ensure that
1738 @code{libgdb} is idle (i.e. no other client is using @code{libgdb})
1739 before responding to a @file{gdb-event} by making a query.
1741 @section CLI support
1743 At present @value{GDBN}'s CLI is very much entangled in with the core of
1744 @code{libgdb}. Consequently, a client wishing to include the CLI in
1745 their interface needs to carefully co-ordinate its own and the CLI's
1748 It is suggested that the client set @code{libgdb} up to be bi-modal
1749 (alternate between CLI and client query modes). The notes below sketch
1754 The client registers itself as an observer of @code{libgdb}.
1756 The client create and install @code{cli-out} builder using its own
1757 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1758 @code{gdb_stdout} streams.
1760 The client creates a separate custom @code{ui-out} builder that is only
1761 used while making direct queries to @code{libgdb}.
1764 When the client receives input intended for the CLI, it simply passes it
1765 along. Since the @code{cli-out} builder is installed by default, all
1766 the CLI output in response to that command is routed (pronounced rooted)
1767 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1768 At the same time, the client is kept abreast of internal changes by
1769 virtue of being a @code{libgdb} observer.
1771 The only restriction on the client is that it must wait until
1772 @code{libgdb} becomes idle before initiating any queries (using the
1773 client's custom builder).
1775 @section @code{libgdb} components
1777 @subheading Observer - @file{gdb-events.h}
1778 @file{gdb-events} provides the client with a very raw mechanism that can
1779 be used to implement an observer. At present it only allows for one
1780 observer and that observer must, internally, handle the need to delay
1781 the processing of any event notifications until after @code{libgdb} has
1782 finished the current command.
1784 @subheading Builder - @file{ui-out.h}
1785 @file{ui-out} provides the infrastructure necessary for a client to
1786 create a builder. That builder is then passed down to @code{libgdb}
1787 when doing any queries.
1789 @subheading Event Loop - @file{event-loop.h}
1790 @c There could be an entire section on the event-loop
1791 @file{event-loop}, currently non-re-entrant, provides a simple event
1792 loop. A client would need to either plug its self into this loop or,
1793 implement a new event-loop that GDB would use.
1795 The event-loop will eventually be made re-entrant. This is so that
1796 @value{GDBN} can better handle the problem of some commands blocking
1797 instead of returning.
1799 @subheading Library - @file{gdb.h}
1800 @file{libgdb} is the most obvious component of this system. It provides
1801 the query interface. Each function is parameterized by a @code{ui-out}
1802 builder. The result of the query is constructed using that builder
1803 before the query function returns.
1805 @node Symbol Handling
1807 @chapter Symbol Handling
1809 Symbols are a key part of @value{GDBN}'s operation. Symbols include variables,
1810 functions, and types.
1812 @section Symbol Reading
1814 @cindex symbol reading
1815 @cindex reading of symbols
1816 @cindex symbol files
1817 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
1818 file is the file containing the program which @value{GDBN} is
1819 debugging. @value{GDBN} can be directed to use a different file for
1820 symbols (with the @samp{symbol-file} command), and it can also read
1821 more symbols via the @samp{add-file} and @samp{load} commands, or while
1822 reading symbols from shared libraries.
1824 @findex find_sym_fns
1825 Symbol files are initially opened by code in @file{symfile.c} using
1826 the BFD library (@pxref{Support Libraries}). BFD identifies the type
1827 of the file by examining its header. @code{find_sym_fns} then uses
1828 this identification to locate a set of symbol-reading functions.
1830 @findex add_symtab_fns
1831 @cindex @code{sym_fns} structure
1832 @cindex adding a symbol-reading module
1833 Symbol-reading modules identify themselves to @value{GDBN} by calling
1834 @code{add_symtab_fns} during their module initialization. The argument
1835 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
1836 name (or name prefix) of the symbol format, the length of the prefix,
1837 and pointers to four functions. These functions are called at various
1838 times to process symbol files whose identification matches the specified
1841 The functions supplied by each module are:
1844 @item @var{xyz}_symfile_init(struct sym_fns *sf)
1846 @cindex secondary symbol file
1847 Called from @code{symbol_file_add} when we are about to read a new
1848 symbol file. This function should clean up any internal state (possibly
1849 resulting from half-read previous files, for example) and prepare to
1850 read a new symbol file. Note that the symbol file which we are reading
1851 might be a new ``main'' symbol file, or might be a secondary symbol file
1852 whose symbols are being added to the existing symbol table.
1854 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
1855 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
1856 new symbol file being read. Its @code{private} field has been zeroed,
1857 and can be modified as desired. Typically, a struct of private
1858 information will be @code{malloc}'d, and a pointer to it will be placed
1859 in the @code{private} field.
1861 There is no result from @code{@var{xyz}_symfile_init}, but it can call
1862 @code{error} if it detects an unavoidable problem.
1864 @item @var{xyz}_new_init()
1866 Called from @code{symbol_file_add} when discarding existing symbols.
1867 This function needs only handle the symbol-reading module's internal
1868 state; the symbol table data structures visible to the rest of
1869 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
1870 arguments and no result. It may be called after
1871 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
1872 may be called alone if all symbols are simply being discarded.
1874 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
1876 Called from @code{symbol_file_add} to actually read the symbols from a
1877 symbol-file into a set of psymtabs or symtabs.
1879 @code{sf} points to the @code{struct sym_fns} originally passed to
1880 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
1881 the offset between the file's specified start address and its true
1882 address in memory. @code{mainline} is 1 if this is the main symbol
1883 table being read, and 0 if a secondary symbol file (e.g., shared library
1884 or dynamically loaded file) is being read.@refill
1887 In addition, if a symbol-reading module creates psymtabs when
1888 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
1889 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
1890 from any point in the @value{GDBN} symbol-handling code.
1893 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
1895 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
1896 the psymtab has not already been read in and had its @code{pst->symtab}
1897 pointer set. The argument is the psymtab to be fleshed-out into a
1898 symtab. Upon return, @code{pst->readin} should have been set to 1, and
1899 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
1900 zero if there were no symbols in that part of the symbol file.
1903 @section Partial Symbol Tables
1905 @value{GDBN} has three types of symbol tables:
1908 @cindex full symbol table
1911 Full symbol tables (@dfn{symtabs}). These contain the main
1912 information about symbols and addresses.
1916 Partial symbol tables (@dfn{psymtabs}). These contain enough
1917 information to know when to read the corresponding part of the full
1920 @cindex minimal symbol table
1923 Minimal symbol tables (@dfn{msymtabs}). These contain information
1924 gleaned from non-debugging symbols.
1927 @cindex partial symbol table
1928 This section describes partial symbol tables.
1930 A psymtab is constructed by doing a very quick pass over an executable
1931 file's debugging information. Small amounts of information are
1932 extracted---enough to identify which parts of the symbol table will
1933 need to be re-read and fully digested later, when the user needs the
1934 information. The speed of this pass causes @value{GDBN} to start up very
1935 quickly. Later, as the detailed rereading occurs, it occurs in small
1936 pieces, at various times, and the delay therefrom is mostly invisible to
1938 @c (@xref{Symbol Reading}.)
1940 The symbols that show up in a file's psymtab should be, roughly, those
1941 visible to the debugger's user when the program is not running code from
1942 that file. These include external symbols and types, static symbols and
1943 types, and @code{enum} values declared at file scope.
1945 The psymtab also contains the range of instruction addresses that the
1946 full symbol table would represent.
1948 @cindex finding a symbol
1949 @cindex symbol lookup
1950 The idea is that there are only two ways for the user (or much of the
1951 code in the debugger) to reference a symbol:
1954 @findex find_pc_function
1955 @findex find_pc_line
1957 By its address (e.g., execution stops at some address which is inside a
1958 function in this file). The address will be noticed to be in the
1959 range of this psymtab, and the full symtab will be read in.
1960 @code{find_pc_function}, @code{find_pc_line}, and other
1961 @code{find_pc_@dots{}} functions handle this.
1963 @cindex lookup_symbol
1966 (e.g., the user asks to print a variable, or set a breakpoint on a
1967 function). Global names and file-scope names will be found in the
1968 psymtab, which will cause the symtab to be pulled in. Local names will
1969 have to be qualified by a global name, or a file-scope name, in which
1970 case we will have already read in the symtab as we evaluated the
1971 qualifier. Or, a local symbol can be referenced when we are ``in'' a
1972 local scope, in which case the first case applies. @code{lookup_symbol}
1973 does most of the work here.
1976 The only reason that psymtabs exist is to cause a symtab to be read in
1977 at the right moment. Any symbol that can be elided from a psymtab,
1978 while still causing that to happen, should not appear in it. Since
1979 psymtabs don't have the idea of scope, you can't put local symbols in
1980 them anyway. Psymtabs don't have the idea of the type of a symbol,
1981 either, so types need not appear, unless they will be referenced by
1984 It is a bug for @value{GDBN} to behave one way when only a psymtab has
1985 been read, and another way if the corresponding symtab has been read
1986 in. Such bugs are typically caused by a psymtab that does not contain
1987 all the visible symbols, or which has the wrong instruction address
1990 The psymtab for a particular section of a symbol file (objfile) could be
1991 thrown away after the symtab has been read in. The symtab should always
1992 be searched before the psymtab, so the psymtab will never be used (in a
1993 bug-free environment). Currently, psymtabs are allocated on an obstack,
1994 and all the psymbols themselves are allocated in a pair of large arrays
1995 on an obstack, so there is little to be gained by trying to free them
1996 unless you want to do a lot more work.
2000 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
2002 @cindex fundamental types
2003 These are the fundamental types that @value{GDBN} uses internally. Fundamental
2004 types from the various debugging formats (stabs, ELF, etc) are mapped
2005 into one of these. They are basically a union of all fundamental types
2006 that @value{GDBN} knows about for all the languages that @value{GDBN}
2009 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
2012 Each time @value{GDBN} builds an internal type, it marks it with one
2013 of these types. The type may be a fundamental type, such as
2014 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
2015 which is a pointer to another type. Typically, several @code{FT_*}
2016 types map to one @code{TYPE_CODE_*} type, and are distinguished by
2017 other members of the type struct, such as whether the type is signed
2018 or unsigned, and how many bits it uses.
2020 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
2022 These are instances of type structs that roughly correspond to
2023 fundamental types and are created as global types for @value{GDBN} to
2024 use for various ugly historical reasons. We eventually want to
2025 eliminate these. Note for example that @code{builtin_type_int}
2026 initialized in @file{gdbtypes.c} is basically the same as a
2027 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
2028 an @code{FT_INTEGER} fundamental type. The difference is that the
2029 @code{builtin_type} is not associated with any particular objfile, and
2030 only one instance exists, while @file{c-lang.c} builds as many
2031 @code{TYPE_CODE_INT} types as needed, with each one associated with
2032 some particular objfile.
2034 @section Object File Formats
2035 @cindex object file formats
2039 @cindex @code{a.out} format
2040 The @code{a.out} format is the original file format for Unix. It
2041 consists of three sections: @code{text}, @code{data}, and @code{bss},
2042 which are for program code, initialized data, and uninitialized data,
2045 The @code{a.out} format is so simple that it doesn't have any reserved
2046 place for debugging information. (Hey, the original Unix hackers used
2047 @samp{adb}, which is a machine-language debugger!) The only debugging
2048 format for @code{a.out} is stabs, which is encoded as a set of normal
2049 symbols with distinctive attributes.
2051 The basic @code{a.out} reader is in @file{dbxread.c}.
2056 The COFF format was introduced with System V Release 3 (SVR3) Unix.
2057 COFF files may have multiple sections, each prefixed by a header. The
2058 number of sections is limited.
2060 The COFF specification includes support for debugging. Although this
2061 was a step forward, the debugging information was woefully limited. For
2062 instance, it was not possible to represent code that came from an
2065 The COFF reader is in @file{coffread.c}.
2069 @cindex ECOFF format
2070 ECOFF is an extended COFF originally introduced for Mips and Alpha
2073 The basic ECOFF reader is in @file{mipsread.c}.
2077 @cindex XCOFF format
2078 The IBM RS/6000 running AIX uses an object file format called XCOFF.
2079 The COFF sections, symbols, and line numbers are used, but debugging
2080 symbols are @code{dbx}-style stabs whose strings are located in the
2081 @code{.debug} section (rather than the string table). For more
2082 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
2084 The shared library scheme has a clean interface for figuring out what
2085 shared libraries are in use, but the catch is that everything which
2086 refers to addresses (symbol tables and breakpoints at least) needs to be
2087 relocated for both shared libraries and the main executable. At least
2088 using the standard mechanism this can only be done once the program has
2089 been run (or the core file has been read).
2093 @cindex PE-COFF format
2094 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
2095 executables. PE is basically COFF with additional headers.
2097 While BFD includes special PE support, @value{GDBN} needs only the basic
2103 The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
2104 to COFF in being organized into a number of sections, but it removes
2105 many of COFF's limitations.
2107 The basic ELF reader is in @file{elfread.c}.
2112 SOM is HP's object file and debug format (not to be confused with IBM's
2113 SOM, which is a cross-language ABI).
2115 The SOM reader is in @file{hpread.c}.
2117 @section Debugging File Formats
2119 This section describes characteristics of debugging information that
2120 are independent of the object file format.
2124 @cindex stabs debugging info
2125 @code{stabs} started out as special symbols within the @code{a.out}
2126 format. Since then, it has been encapsulated into other file
2127 formats, such as COFF and ELF.
2129 While @file{dbxread.c} does some of the basic stab processing,
2130 including for encapsulated versions, @file{stabsread.c} does
2135 @cindex COFF debugging info
2136 The basic COFF definition includes debugging information. The level
2137 of support is minimal and non-extensible, and is not often used.
2139 @subsection Mips debug (Third Eye)
2141 @cindex ECOFF debugging info
2142 ECOFF includes a definition of a special debug format.
2144 The file @file{mdebugread.c} implements reading for this format.
2148 @cindex DWARF 1 debugging info
2149 DWARF 1 is a debugging format that was originally designed to be
2150 used with ELF in SVR4 systems.
2155 @c If defined, these are the producer strings in a DWARF 1 file. All of
2156 @c these have reasonable defaults already.
2158 The DWARF 1 reader is in @file{dwarfread.c}.
2162 @cindex DWARF 2 debugging info
2163 DWARF 2 is an improved but incompatible version of DWARF 1.
2165 The DWARF 2 reader is in @file{dwarf2read.c}.
2169 @cindex SOM debugging info
2170 Like COFF, the SOM definition includes debugging information.
2172 @section Adding a New Symbol Reader to @value{GDBN}
2174 @cindex adding debugging info reader
2175 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
2176 there is probably little to be done.
2178 If you need to add a new object file format, you must first add it to
2179 BFD. This is beyond the scope of this document.
2181 You must then arrange for the BFD code to provide access to the
2182 debugging symbols. Generally @value{GDBN} will have to call swapping routines
2183 from BFD and a few other BFD internal routines to locate the debugging
2184 information. As much as possible, @value{GDBN} should not depend on the BFD
2185 internal data structures.
2187 For some targets (e.g., COFF), there is a special transfer vector used
2188 to call swapping routines, since the external data structures on various
2189 platforms have different sizes and layouts. Specialized routines that
2190 will only ever be implemented by one object file format may be called
2191 directly. This interface should be described in a file
2192 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
2194 @section Memory Management for Symbol Files
2196 Most memory associated with a loaded symbol file is stored on
2197 its @code{objfile_obstack}. This includes symbols, types,
2198 namespace data, and other information produced by the symbol readers.
2200 Because this data lives on the objfile's obstack, it is automatically
2201 released when the objfile is unloaded or reloaded. Therefore one
2202 objfile must not reference symbol or type data from another objfile;
2203 they could be unloaded at different times.
2205 User convenience variables, et cetera, have associated types. Normally
2206 these types live in the associated objfile. However, when the objfile
2207 is unloaded, those types are deep copied to global memory, so that
2208 the values of the user variables and history items are not lost.
2211 @node Language Support
2213 @chapter Language Support
2215 @cindex language support
2216 @value{GDBN}'s language support is mainly driven by the symbol reader,
2217 although it is possible for the user to set the source language
2220 @value{GDBN} chooses the source language by looking at the extension
2221 of the file recorded in the debug info; @file{.c} means C, @file{.f}
2222 means Fortran, etc. It may also use a special-purpose language
2223 identifier if the debug format supports it, like with DWARF.
2225 @section Adding a Source Language to @value{GDBN}
2227 @cindex adding source language
2228 To add other languages to @value{GDBN}'s expression parser, follow the
2232 @item Create the expression parser.
2234 @cindex expression parser
2235 This should reside in a file @file{@var{lang}-exp.y}. Routines for
2236 building parsed expressions into a @code{union exp_element} list are in
2239 @cindex language parser
2240 Since we can't depend upon everyone having Bison, and YACC produces
2241 parsers that define a bunch of global names, the following lines
2242 @strong{must} be included at the top of the YACC parser, to prevent the
2243 various parsers from defining the same global names:
2246 #define yyparse @var{lang}_parse
2247 #define yylex @var{lang}_lex
2248 #define yyerror @var{lang}_error
2249 #define yylval @var{lang}_lval
2250 #define yychar @var{lang}_char
2251 #define yydebug @var{lang}_debug
2252 #define yypact @var{lang}_pact
2253 #define yyr1 @var{lang}_r1
2254 #define yyr2 @var{lang}_r2
2255 #define yydef @var{lang}_def
2256 #define yychk @var{lang}_chk
2257 #define yypgo @var{lang}_pgo
2258 #define yyact @var{lang}_act
2259 #define yyexca @var{lang}_exca
2260 #define yyerrflag @var{lang}_errflag
2261 #define yynerrs @var{lang}_nerrs
2264 At the bottom of your parser, define a @code{struct language_defn} and
2265 initialize it with the right values for your language. Define an
2266 @code{initialize_@var{lang}} routine and have it call
2267 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
2268 that your language exists. You'll need some other supporting variables
2269 and functions, which will be used via pointers from your
2270 @code{@var{lang}_language_defn}. See the declaration of @code{struct
2271 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
2272 for more information.
2274 @item Add any evaluation routines, if necessary
2276 @cindex expression evaluation routines
2277 @findex evaluate_subexp
2278 @findex prefixify_subexp
2279 @findex length_of_subexp
2280 If you need new opcodes (that represent the operations of the language),
2281 add them to the enumerated type in @file{expression.h}. Add support
2282 code for these operations in the @code{evaluate_subexp} function
2283 defined in the file @file{eval.c}. Add cases
2284 for new opcodes in two functions from @file{parse.c}:
2285 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
2286 the number of @code{exp_element}s that a given operation takes up.
2288 @item Update some existing code
2290 Add an enumerated identifier for your language to the enumerated type
2291 @code{enum language} in @file{defs.h}.
2293 Update the routines in @file{language.c} so your language is included.
2294 These routines include type predicates and such, which (in some cases)
2295 are language dependent. If your language does not appear in the switch
2296 statement, an error is reported.
2298 @vindex current_language
2299 Also included in @file{language.c} is the code that updates the variable
2300 @code{current_language}, and the routines that translate the
2301 @code{language_@var{lang}} enumerated identifier into a printable
2304 @findex _initialize_language
2305 Update the function @code{_initialize_language} to include your
2306 language. This function picks the default language upon startup, so is
2307 dependent upon which languages that @value{GDBN} is built for.
2309 @findex allocate_symtab
2310 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
2311 code so that the language of each symtab (source file) is set properly.
2312 This is used to determine the language to use at each stack frame level.
2313 Currently, the language is set based upon the extension of the source
2314 file. If the language can be better inferred from the symbol
2315 information, please set the language of the symtab in the symbol-reading
2318 @findex print_subexp
2319 @findex op_print_tab
2320 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
2321 expression opcodes you have added to @file{expression.h}. Also, add the
2322 printed representations of your operators to @code{op_print_tab}.
2324 @item Add a place of call
2327 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2328 @code{parse_exp_1} (defined in @file{parse.c}).
2330 @item Use macros to trim code
2332 @cindex trimming language-dependent code
2333 The user has the option of building @value{GDBN} for some or all of the
2334 languages. If the user decides to build @value{GDBN} for the language
2335 @var{lang}, then every file dependent on @file{language.h} will have the
2336 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2337 leave out large routines that the user won't need if he or she is not
2338 using your language.
2340 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2341 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2342 compiled form of your parser) is not linked into @value{GDBN} at all.
2344 See the file @file{configure.in} for how @value{GDBN} is configured
2345 for different languages.
2347 @item Edit @file{Makefile.in}
2349 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2350 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2351 not get linked in, or, worse yet, it may not get @code{tar}red into the
2356 @node Host Definition
2358 @chapter Host Definition
2360 With the advent of Autoconf, it's rarely necessary to have host
2361 definition machinery anymore. The following information is provided,
2362 mainly, as an historical reference.
2364 @section Adding a New Host
2366 @cindex adding a new host
2367 @cindex host, adding
2368 @value{GDBN}'s host configuration support normally happens via Autoconf.
2369 New host-specific definitions should not be needed. Older hosts
2370 @value{GDBN} still use the host-specific definitions and files listed
2371 below, but these mostly exist for historical reasons, and will
2372 eventually disappear.
2375 @item gdb/config/@var{arch}/@var{xyz}.mh
2376 This file once contained both host and native configuration information
2377 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2378 configuration information is now handed by Autoconf.
2380 Host configuration information included a definition of
2381 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2382 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2383 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2385 New host only configurations do not need this file.
2387 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2388 This file once contained definitions and includes required when hosting
2389 gdb on machine @var{xyz}. Those definitions and includes are now
2390 handled by Autoconf.
2392 New host and native configurations do not need this file.
2394 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2395 file to define the macros @var{HOST_FLOAT_FORMAT},
2396 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2397 also needs to be replaced with either an Autoconf or run-time test.}
2401 @subheading Generic Host Support Files
2403 @cindex generic host support
2404 There are some ``generic'' versions of routines that can be used by
2405 various systems. These can be customized in various ways by macros
2406 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2407 the @var{xyz} host, you can just include the generic file's name (with
2408 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2410 Otherwise, if your machine needs custom support routines, you will need
2411 to write routines that perform the same functions as the generic file.
2412 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2413 into @code{XDEPFILES}.
2416 @cindex remote debugging support
2417 @cindex serial line support
2419 This contains serial line support for Unix systems. This is always
2420 included, via the makefile variable @code{SER_HARDWIRE}; override this
2421 variable in the @file{.mh} file to avoid it.
2424 This contains serial line support for 32-bit programs running under DOS,
2425 using the DJGPP (a.k.a.@: GO32) execution environment.
2427 @cindex TCP remote support
2429 This contains generic TCP support using sockets.
2432 @section Host Conditionals
2434 When @value{GDBN} is configured and compiled, various macros are
2435 defined or left undefined, to control compilation based on the
2436 attributes of the host system. These macros and their meanings (or if
2437 the meaning is not documented here, then one of the source files where
2438 they are used is indicated) are:
2441 @item @value{GDBN}INIT_FILENAME
2442 The default name of @value{GDBN}'s initialization file (normally
2446 This macro is deprecated.
2448 @item SIGWINCH_HANDLER
2449 If your host defines @code{SIGWINCH}, you can define this to be the name
2450 of a function to be called if @code{SIGWINCH} is received.
2452 @item SIGWINCH_HANDLER_BODY
2453 Define this to expand into code that will define the function named by
2454 the expansion of @code{SIGWINCH_HANDLER}.
2456 @item ALIGN_STACK_ON_STARTUP
2457 @cindex stack alignment
2458 Define this if your system is of a sort that will crash in
2459 @code{tgetent} if the stack happens not to be longword-aligned when
2460 @code{main} is called. This is a rare situation, but is known to occur
2461 on several different types of systems.
2463 @item CRLF_SOURCE_FILES
2464 @cindex DOS text files
2465 Define this if host files use @code{\r\n} rather than @code{\n} as a
2466 line terminator. This will cause source file listings to omit @code{\r}
2467 characters when printing and it will allow @code{\r\n} line endings of files
2468 which are ``sourced'' by gdb. It must be possible to open files in binary
2469 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2471 @item DEFAULT_PROMPT
2473 The default value of the prompt string (normally @code{"(gdb) "}).
2476 @cindex terminal device
2477 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2480 Define this if binary files are opened the same way as text files.
2484 In some cases, use the system call @code{mmap} for reading symbol
2485 tables. For some machines this allows for sharing and quick updates.
2488 Define this if the host system has @code{termio.h}.
2495 Values for host-side constants.
2498 Substitute for isatty, if not available.
2501 This is the longest integer type available on the host. If not defined,
2502 it will default to @code{long long} or @code{long}, depending on
2503 @code{CC_HAS_LONG_LONG}.
2505 @item CC_HAS_LONG_LONG
2506 @cindex @code{long long} data type
2507 Define this if the host C compiler supports @code{long long}. This is set
2508 by the @code{configure} script.
2510 @item PRINTF_HAS_LONG_LONG
2511 Define this if the host can handle printing of long long integers via
2512 the printf format conversion specifier @code{ll}. This is set by the
2513 @code{configure} script.
2515 @item HAVE_LONG_DOUBLE
2516 Define this if the host C compiler supports @code{long double}. This is
2517 set by the @code{configure} script.
2519 @item PRINTF_HAS_LONG_DOUBLE
2520 Define this if the host can handle printing of long double float-point
2521 numbers via the printf format conversion specifier @code{Lg}. This is
2522 set by the @code{configure} script.
2524 @item SCANF_HAS_LONG_DOUBLE
2525 Define this if the host can handle the parsing of long double
2526 float-point numbers via the scanf format conversion specifier
2527 @code{Lg}. This is set by the @code{configure} script.
2529 @item LSEEK_NOT_LINEAR
2530 Define this if @code{lseek (n)} does not necessarily move to byte number
2531 @code{n} in the file. This is only used when reading source files. It
2532 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2535 This macro is used as the argument to @code{lseek} (or, most commonly,
2536 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2537 which is the POSIX equivalent.
2540 If defined, this should be one or more tokens, such as @code{volatile},
2541 that can be used in both the declaration and definition of functions to
2542 indicate that they never return. The default is already set correctly
2543 if compiling with GCC. This will almost never need to be defined.
2546 If defined, this should be one or more tokens, such as
2547 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2548 of functions to indicate that they never return. The default is already
2549 set correctly if compiling with GCC. This will almost never need to be
2554 Define these to appropriate value for the system @code{lseek}, if not already
2558 This is the signal for stopping @value{GDBN}. Defaults to
2559 @code{SIGTSTP}. (Only redefined for the Convex.)
2562 Means that System V (prior to SVR4) include files are in use. (FIXME:
2563 This symbol is abused in @file{infrun.c}, @file{regex.c}, and
2564 @file{utils.c} for other things, at the moment.)
2567 Define this to help placate @code{lint} in some situations.
2570 Define this to override the defaults of @code{__volatile__} or
2575 @node Target Architecture Definition
2577 @chapter Target Architecture Definition
2579 @cindex target architecture definition
2580 @value{GDBN}'s target architecture defines what sort of
2581 machine-language programs @value{GDBN} can work with, and how it works
2584 The target architecture object is implemented as the C structure
2585 @code{struct gdbarch *}. The structure, and its methods, are generated
2586 using the Bourne shell script @file{gdbarch.sh}.
2588 @section Operating System ABI Variant Handling
2589 @cindex OS ABI variants
2591 @value{GDBN} provides a mechanism for handling variations in OS
2592 ABIs. An OS ABI variant may have influence over any number of
2593 variables in the target architecture definition. There are two major
2594 components in the OS ABI mechanism: sniffers and handlers.
2596 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2597 (the architecture may be wildcarded) in an attempt to determine the
2598 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2599 to be @dfn{generic}, while sniffers for a specific architecture are
2600 considered to be @dfn{specific}. A match from a specific sniffer
2601 overrides a match from a generic sniffer. Multiple sniffers for an
2602 architecture/flavour may exist, in order to differentiate between two
2603 different operating systems which use the same basic file format. The
2604 OS ABI framework provides a generic sniffer for ELF-format files which
2605 examines the @code{EI_OSABI} field of the ELF header, as well as note
2606 sections known to be used by several operating systems.
2608 @cindex fine-tuning @code{gdbarch} structure
2609 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2610 selected OS ABI. There may be only one handler for a given OS ABI
2611 for each BFD architecture.
2613 The following OS ABI variants are defined in @file{defs.h}:
2617 @findex GDB_OSABI_UNINITIALIZED
2618 @item GDB_OSABI_UNINITIALIZED
2619 Used for struct gdbarch_info if ABI is still uninitialized.
2621 @findex GDB_OSABI_UNKNOWN
2622 @item GDB_OSABI_UNKNOWN
2623 The ABI of the inferior is unknown. The default @code{gdbarch}
2624 settings for the architecture will be used.
2626 @findex GDB_OSABI_SVR4
2627 @item GDB_OSABI_SVR4
2628 UNIX System V Release 4.
2630 @findex GDB_OSABI_HURD
2631 @item GDB_OSABI_HURD
2632 GNU using the Hurd kernel.
2634 @findex GDB_OSABI_SOLARIS
2635 @item GDB_OSABI_SOLARIS
2638 @findex GDB_OSABI_OSF1
2639 @item GDB_OSABI_OSF1
2640 OSF/1, including Digital UNIX and Compaq Tru64 UNIX.
2642 @findex GDB_OSABI_LINUX
2643 @item GDB_OSABI_LINUX
2644 GNU using the Linux kernel.
2646 @findex GDB_OSABI_FREEBSD_AOUT
2647 @item GDB_OSABI_FREEBSD_AOUT
2648 FreeBSD using the @code{a.out} executable format.
2650 @findex GDB_OSABI_FREEBSD_ELF
2651 @item GDB_OSABI_FREEBSD_ELF
2652 FreeBSD using the ELF executable format.
2654 @findex GDB_OSABI_NETBSD_AOUT
2655 @item GDB_OSABI_NETBSD_AOUT
2656 NetBSD using the @code{a.out} executable format.
2658 @findex GDB_OSABI_NETBSD_ELF
2659 @item GDB_OSABI_NETBSD_ELF
2660 NetBSD using the ELF executable format.
2662 @findex GDB_OSABI_OPENBSD_ELF
2663 @item GDB_OSABI_OPENBSD_ELF
2664 OpenBSD using the ELF executable format.
2666 @findex GDB_OSABI_WINCE
2667 @item GDB_OSABI_WINCE
2670 @findex GDB_OSABI_GO32
2671 @item GDB_OSABI_GO32
2674 @findex GDB_OSABI_IRIX
2675 @item GDB_OSABI_IRIX
2678 @findex GDB_OSABI_INTERIX
2679 @item GDB_OSABI_INTERIX
2680 Interix (Posix layer for MS-Windows systems).
2682 @findex GDB_OSABI_HPUX_ELF
2683 @item GDB_OSABI_HPUX_ELF
2684 HP/UX using the ELF executable format.
2686 @findex GDB_OSABI_HPUX_SOM
2687 @item GDB_OSABI_HPUX_SOM
2688 HP/UX using the SOM executable format.
2690 @findex GDB_OSABI_QNXNTO
2691 @item GDB_OSABI_QNXNTO
2694 @findex GDB_OSABI_CYGWIN
2695 @item GDB_OSABI_CYGWIN
2698 @findex GDB_OSABI_AIX
2704 Here are the functions that make up the OS ABI framework:
2706 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2707 Return the name of the OS ABI corresponding to @var{osabi}.
2710 @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}))
2711 Register the OS ABI handler specified by @var{init_osabi} for the
2712 architecture, machine type and OS ABI specified by @var{arch},
2713 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2714 machine type, which implies the architecture's default machine type,
2718 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2719 Register the OS ABI file sniffer specified by @var{sniffer} for the
2720 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2721 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2722 be generic, and is allowed to examine @var{flavour}-flavoured files for
2726 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2727 Examine the file described by @var{abfd} to determine its OS ABI.
2728 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2732 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2733 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2734 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2735 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2736 architecture, a warning will be issued and the debugging session will continue
2737 with the defaults already established for @var{gdbarch}.
2740 @deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj})
2741 Helper routine for ELF file sniffers. Examine the file described by
2742 @var{abfd} and look at ABI tag note sections to determine the OS ABI
2743 from the note. This function should be called via
2744 @code{bfd_map_over_sections}.
2747 @section Initializing a New Architecture
2749 Each @code{gdbarch} is associated with a single @sc{bfd} architecture,
2750 via a @code{bfd_arch_@var{arch}} constant. The @code{gdbarch} is
2751 registered by a call to @code{register_gdbarch_init}, usually from
2752 the file's @code{_initialize_@var{filename}} routine, which will
2753 be automatically called during @value{GDBN} startup. The arguments
2754 are a @sc{bfd} architecture constant and an initialization function.
2756 The initialization function has this type:
2759 static struct gdbarch *
2760 @var{arch}_gdbarch_init (struct gdbarch_info @var{info},
2761 struct gdbarch_list *@var{arches})
2764 The @var{info} argument contains parameters used to select the correct
2765 architecture, and @var{arches} is a list of architectures which
2766 have already been created with the same @code{bfd_arch_@var{arch}}
2769 The initialization function should first make sure that @var{info}
2770 is acceptable, and return @code{NULL} if it is not. Then, it should
2771 search through @var{arches} for an exact match to @var{info}, and
2772 return one if found. Lastly, if no exact match was found, it should
2773 create a new architecture based on @var{info} and return it.
2775 Only information in @var{info} should be used to choose the new
2776 architecture. Historically, @var{info} could be sparse, and
2777 defaults would be collected from the first element on @var{arches}.
2778 However, @value{GDBN} now fills in @var{info} more thoroughly,
2779 so new @code{gdbarch} initialization functions should not take
2780 defaults from @var{arches}.
2782 @section Registers and Memory
2784 @value{GDBN}'s model of the target machine is rather simple.
2785 @value{GDBN} assumes the machine includes a bank of registers and a
2786 block of memory. Each register may have a different size.
2788 @value{GDBN} does not have a magical way to match up with the
2789 compiler's idea of which registers are which; however, it is critical
2790 that they do match up accurately. The only way to make this work is
2791 to get accurate information about the order that the compiler uses,
2792 and to reflect that in the @code{REGISTER_NAME} and related macros.
2794 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2796 @section Pointers Are Not Always Addresses
2797 @cindex pointer representation
2798 @cindex address representation
2799 @cindex word-addressed machines
2800 @cindex separate data and code address spaces
2801 @cindex spaces, separate data and code address
2802 @cindex address spaces, separate data and code
2803 @cindex code pointers, word-addressed
2804 @cindex converting between pointers and addresses
2805 @cindex D10V addresses
2807 On almost all 32-bit architectures, the representation of a pointer is
2808 indistinguishable from the representation of some fixed-length number
2809 whose value is the byte address of the object pointed to. On such
2810 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2811 However, architectures with smaller word sizes are often cramped for
2812 address space, so they may choose a pointer representation that breaks this
2813 identity, and allows a larger code address space.
2815 For example, the Renesas D10V is a 16-bit VLIW processor whose
2816 instructions are 32 bits long@footnote{Some D10V instructions are
2817 actually pairs of 16-bit sub-instructions. However, since you can't
2818 jump into the middle of such a pair, code addresses can only refer to
2819 full 32 bit instructions, which is what matters in this explanation.}.
2820 If the D10V used ordinary byte addresses to refer to code locations,
2821 then the processor would only be able to address 64kb of instructions.
2822 However, since instructions must be aligned on four-byte boundaries, the
2823 low two bits of any valid instruction's byte address are always
2824 zero---byte addresses waste two bits. So instead of byte addresses,
2825 the D10V uses word addresses---byte addresses shifted right two bits---to
2826 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2829 However, this means that code pointers and data pointers have different
2830 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2831 @code{0xC020} when used as a data address, but refers to byte address
2832 @code{0x30080} when used as a code address.
2834 (The D10V also uses separate code and data address spaces, which also
2835 affects the correspondence between pointers and addresses, but we're
2836 going to ignore that here; this example is already too long.)
2838 To cope with architectures like this---the D10V is not the only
2839 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2840 byte numbers, and @dfn{pointers}, which are the target's representation
2841 of an address of a particular type of data. In the example above,
2842 @code{0xC020} is the pointer, which refers to one of the addresses
2843 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2844 @value{GDBN} provides functions for turning a pointer into an address
2845 and vice versa, in the appropriate way for the current architecture.
2847 Unfortunately, since addresses and pointers are identical on almost all
2848 processors, this distinction tends to bit-rot pretty quickly. Thus,
2849 each time you port @value{GDBN} to an architecture which does
2850 distinguish between pointers and addresses, you'll probably need to
2851 clean up some architecture-independent code.
2853 Here are functions which convert between pointers and addresses:
2855 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2856 Treat the bytes at @var{buf} as a pointer or reference of type
2857 @var{type}, and return the address it represents, in a manner
2858 appropriate for the current architecture. This yields an address
2859 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2860 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2863 For example, if the current architecture is the Intel x86, this function
2864 extracts a little-endian integer of the appropriate length from
2865 @var{buf} and returns it. However, if the current architecture is the
2866 D10V, this function will return a 16-bit integer extracted from
2867 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2869 If @var{type} is not a pointer or reference type, then this function
2870 will signal an internal error.
2873 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2874 Store the address @var{addr} in @var{buf}, in the proper format for a
2875 pointer of type @var{type} in the current architecture. Note that
2876 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2879 For example, if the current architecture is the Intel x86, this function
2880 stores @var{addr} unmodified as a little-endian integer of the
2881 appropriate length in @var{buf}. However, if the current architecture
2882 is the D10V, this function divides @var{addr} by four if @var{type} is
2883 a pointer to a function, and then stores it in @var{buf}.
2885 If @var{type} is not a pointer or reference type, then this function
2886 will signal an internal error.
2889 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2890 Assuming that @var{val} is a pointer, return the address it represents,
2891 as appropriate for the current architecture.
2893 This function actually works on integral values, as well as pointers.
2894 For pointers, it performs architecture-specific conversions as
2895 described above for @code{extract_typed_address}.
2898 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2899 Create and return a value representing a pointer of type @var{type} to
2900 the address @var{addr}, as appropriate for the current architecture.
2901 This function performs architecture-specific conversions as described
2902 above for @code{store_typed_address}.
2905 Here are some macros which architectures can define to indicate the
2906 relationship between pointers and addresses. These have default
2907 definitions, appropriate for architectures on which all pointers are
2908 simple unsigned byte addresses.
2910 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2911 Assume that @var{buf} holds a pointer of type @var{type}, in the
2912 appropriate format for the current architecture. Return the byte
2913 address the pointer refers to.
2915 This function may safely assume that @var{type} is either a pointer or a
2916 C@t{++} reference type.
2919 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2920 Store in @var{buf} a pointer of type @var{type} representing the address
2921 @var{addr}, in the appropriate format for the current architecture.
2923 This function may safely assume that @var{type} is either a pointer or a
2924 C@t{++} reference type.
2927 @section Address Classes
2928 @cindex address classes
2929 @cindex DW_AT_byte_size
2930 @cindex DW_AT_address_class
2932 Sometimes information about different kinds of addresses is available
2933 via the debug information. For example, some programming environments
2934 define addresses of several different sizes. If the debug information
2935 distinguishes these kinds of address classes through either the size
2936 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2937 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2938 following macros should be defined in order to disambiguate these
2939 types within @value{GDBN} as well as provide the added information to
2940 a @value{GDBN} user when printing type expressions.
2942 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2943 Returns the type flags needed to construct a pointer type whose size
2944 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2945 This function is normally called from within a symbol reader. See
2946 @file{dwarf2read.c}.
2949 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2950 Given the type flags representing an address class qualifier, return
2953 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2954 Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags
2955 for that address class qualifier.
2958 Since the need for address classes is rather rare, none of
2959 the address class macros defined by default. Predicate
2960 macros are provided to detect when they are defined.
2962 Consider a hypothetical architecture in which addresses are normally
2963 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2964 suppose that the @w{DWARF 2} information for this architecture simply
2965 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2966 of these "short" pointers. The following functions could be defined
2967 to implement the address class macros:
2970 somearch_address_class_type_flags (int byte_size,
2971 int dwarf2_addr_class)
2974 return TYPE_FLAG_ADDRESS_CLASS_1;
2980 somearch_address_class_type_flags_to_name (int type_flags)
2982 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
2989 somearch_address_class_name_to_type_flags (char *name,
2990 int *type_flags_ptr)
2992 if (strcmp (name, "short") == 0)
2994 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
3002 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
3003 to indicate the presence of one of these "short" pointers. E.g, if
3004 the debug information indicates that @code{short_ptr_var} is one of these
3005 short pointers, @value{GDBN} might show the following behavior:
3008 (gdb) ptype short_ptr_var
3009 type = int * @@short
3013 @section Raw and Virtual Register Representations
3014 @cindex raw register representation
3015 @cindex virtual register representation
3016 @cindex representations, raw and virtual registers
3018 @emph{Maintainer note: This section is pretty much obsolete. The
3019 functionality described here has largely been replaced by
3020 pseudo-registers and the mechanisms described in @ref{Target
3021 Architecture Definition, , Using Different Register and Memory Data
3022 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
3023 Bug Tracking Database} and
3024 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
3025 up-to-date information.}
3027 Some architectures use one representation for a value when it lives in a
3028 register, but use a different representation when it lives in memory.
3029 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
3030 the target registers, and the @dfn{virtual} representation is the one
3031 used in memory, and within @value{GDBN} @code{struct value} objects.
3033 @emph{Maintainer note: Notice that the same mechanism is being used to
3034 both convert a register to a @code{struct value} and alternative
3037 For almost all data types on almost all architectures, the virtual and
3038 raw representations are identical, and no special handling is needed.
3039 However, they do occasionally differ. For example:
3043 The x86 architecture supports an 80-bit @code{long double} type. However, when
3044 we store those values in memory, they occupy twelve bytes: the
3045 floating-point number occupies the first ten, and the final two bytes
3046 are unused. This keeps the values aligned on four-byte boundaries,
3047 allowing more efficient access. Thus, the x86 80-bit floating-point
3048 type is the raw representation, and the twelve-byte loosely-packed
3049 arrangement is the virtual representation.
3052 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
3053 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
3054 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
3055 raw representation, and the trimmed 32-bit representation is the
3056 virtual representation.
3059 In general, the raw representation is determined by the architecture, or
3060 @value{GDBN}'s interface to the architecture, while the virtual representation
3061 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
3062 @code{registers}, holds the register contents in raw format, and the
3063 @value{GDBN} remote protocol transmits register values in raw format.
3065 Your architecture may define the following macros to request
3066 conversions between the raw and virtual format:
3068 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
3069 Return non-zero if register number @var{reg}'s value needs different raw
3070 and virtual formats.
3072 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
3073 unless this macro returns a non-zero value for that register.
3076 @deftypefn {Target Macro} int DEPRECATED_REGISTER_RAW_SIZE (int @var{reg})
3077 The size of register number @var{reg}'s raw value. This is the number
3078 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
3079 remote protocol packet.
3082 @deftypefn {Target Macro} int DEPRECATED_REGISTER_VIRTUAL_SIZE (int @var{reg})
3083 The size of register number @var{reg}'s value, in its virtual format.
3084 This is the size a @code{struct value}'s buffer will have, holding that
3088 @deftypefn {Target Macro} struct type *DEPRECATED_REGISTER_VIRTUAL_TYPE (int @var{reg})
3089 This is the type of the virtual representation of register number
3090 @var{reg}. Note that there is no need for a macro giving a type for the
3091 register's raw form; once the register's value has been obtained, @value{GDBN}
3092 always uses the virtual form.
3095 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3096 Convert the value of register number @var{reg} to @var{type}, which
3097 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3098 at @var{from} holds the register's value in raw format; the macro should
3099 convert the value to virtual format, and place it at @var{to}.
3101 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
3102 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
3103 arguments in different orders.
3105 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
3106 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
3110 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3111 Convert the value of register number @var{reg} to @var{type}, which
3112 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3113 at @var{from} holds the register's value in raw format; the macro should
3114 convert the value to virtual format, and place it at @var{to}.
3116 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
3117 their @var{reg} and @var{type} arguments in different orders.
3121 @section Using Different Register and Memory Data Representations
3122 @cindex register representation
3123 @cindex memory representation
3124 @cindex representations, register and memory
3125 @cindex register data formats, converting
3126 @cindex @code{struct value}, converting register contents to
3128 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
3129 significant change. Many of the macros and functions referred to in this
3130 section are likely to be subject to further revision. See
3131 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
3132 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
3133 further information. cagney/2002-05-06.}
3135 Some architectures can represent a data object in a register using a
3136 form that is different to the objects more normal memory representation.
3142 The Alpha architecture can represent 32 bit integer values in
3143 floating-point registers.
3146 The x86 architecture supports 80-bit floating-point registers. The
3147 @code{long double} data type occupies 96 bits in memory but only 80 bits
3148 when stored in a register.
3152 In general, the register representation of a data type is determined by
3153 the architecture, or @value{GDBN}'s interface to the architecture, while
3154 the memory representation is determined by the Application Binary
3157 For almost all data types on almost all architectures, the two
3158 representations are identical, and no special handling is needed.
3159 However, they do occasionally differ. Your architecture may define the
3160 following macros to request conversions between the register and memory
3161 representations of a data type:
3163 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
3164 Return non-zero if the representation of a data value stored in this
3165 register may be different to the representation of that same data value
3166 when stored in memory.
3168 When non-zero, the macros @code{REGISTER_TO_VALUE} and
3169 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
3172 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3173 Convert the value of register number @var{reg} to a data object of type
3174 @var{type}. The buffer at @var{from} holds the register's value in raw
3175 format; the converted value should be placed in the buffer at @var{to}.
3177 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3178 their @var{reg} and @var{type} arguments in different orders.
3180 You should only use @code{REGISTER_TO_VALUE} with registers for which
3181 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3184 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3185 Convert a data value of type @var{type} to register number @var{reg}'
3188 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3189 their @var{reg} and @var{type} arguments in different orders.
3191 You should only use @code{VALUE_TO_REGISTER} with registers for which
3192 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3195 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
3196 See @file{mips-tdep.c}. It does not do what you want.
3200 @section Frame Interpretation
3202 @section Inferior Call Setup
3204 @section Compiler Characteristics
3206 @section Target Conditionals
3208 This section describes the macros that you can use to define the target
3213 @item ADDR_BITS_REMOVE (addr)
3214 @findex ADDR_BITS_REMOVE
3215 If a raw machine instruction address includes any bits that are not
3216 really part of the address, then define this macro to expand into an
3217 expression that zeroes those bits in @var{addr}. This is only used for
3218 addresses of instructions, and even then not in all contexts.
3220 For example, the two low-order bits of the PC on the Hewlett-Packard PA
3221 2.0 architecture contain the privilege level of the corresponding
3222 instruction. Since instructions must always be aligned on four-byte
3223 boundaries, the processor masks out these bits to generate the actual
3224 address of the instruction. ADDR_BITS_REMOVE should filter out these
3225 bits with an expression such as @code{((addr) & ~3)}.
3227 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
3228 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
3229 If @var{name} is a valid address class qualifier name, set the @code{int}
3230 referenced by @var{type_flags_ptr} to the mask representing the qualifier
3231 and return 1. If @var{name} is not a valid address class qualifier name,
3234 The value for @var{type_flags_ptr} should be one of
3235 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
3236 possibly some combination of these values or'd together.
3237 @xref{Target Architecture Definition, , Address Classes}.
3239 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
3240 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
3241 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
3244 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3245 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3246 Given a pointers byte size (as described by the debug information) and
3247 the possible @code{DW_AT_address_class} value, return the type flags
3248 used by @value{GDBN} to represent this address class. The value
3249 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
3250 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
3251 values or'd together.
3252 @xref{Target Architecture Definition, , Address Classes}.
3254 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
3255 @findex ADDRESS_CLASS_TYPE_FLAGS_P
3256 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
3259 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
3260 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
3261 Return the name of the address class qualifier associated with the type
3262 flags given by @var{type_flags}.
3264 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
3265 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
3266 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
3268 @xref{Target Architecture Definition, , Address Classes}.
3270 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
3271 @findex ADDRESS_TO_POINTER
3272 Store in @var{buf} a pointer of type @var{type} representing the address
3273 @var{addr}, in the appropriate format for the current architecture.
3274 This macro may safely assume that @var{type} is either a pointer or a
3275 C@t{++} reference type.
3276 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3278 @item BELIEVE_PCC_PROMOTION
3279 @findex BELIEVE_PCC_PROMOTION
3280 Define if the compiler promotes a @code{short} or @code{char}
3281 parameter to an @code{int}, but still reports the parameter as its
3282 original type, rather than the promoted type.
3284 @item BITS_BIG_ENDIAN
3285 @findex BITS_BIG_ENDIAN
3286 Define this if the numbering of bits in the targets does @strong{not} match the
3287 endianness of the target byte order. A value of 1 means that the bits
3288 are numbered in a big-endian bit order, 0 means little-endian.
3292 This is the character array initializer for the bit pattern to put into
3293 memory where a breakpoint is set. Although it's common to use a trap
3294 instruction for a breakpoint, it's not required; for instance, the bit
3295 pattern could be an invalid instruction. The breakpoint must be no
3296 longer than the shortest instruction of the architecture.
3298 @code{BREAKPOINT} has been deprecated in favor of
3299 @code{BREAKPOINT_FROM_PC}.
3301 @item BIG_BREAKPOINT
3302 @itemx LITTLE_BREAKPOINT
3303 @findex LITTLE_BREAKPOINT
3304 @findex BIG_BREAKPOINT
3305 Similar to BREAKPOINT, but used for bi-endian targets.
3307 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3308 favor of @code{BREAKPOINT_FROM_PC}.
3310 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3311 @findex BREAKPOINT_FROM_PC
3312 @anchor{BREAKPOINT_FROM_PC} Use the program counter to determine the
3313 contents and size of a breakpoint instruction. It returns a pointer to
3314 a string of bytes that encode a breakpoint instruction, stores the
3315 length of the string to @code{*@var{lenptr}}, and adjusts the program
3316 counter (if necessary) to point to the actual memory location where the
3317 breakpoint should be inserted.
3319 Although it is common to use a trap instruction for a breakpoint, it's
3320 not required; for instance, the bit pattern could be an invalid
3321 instruction. The breakpoint must be no longer than the shortest
3322 instruction of the architecture.
3324 Replaces all the other @var{BREAKPOINT} macros.
3326 @item MEMORY_INSERT_BREAKPOINT (@var{bp_tgt})
3327 @itemx MEMORY_REMOVE_BREAKPOINT (@var{bp_tgt})
3328 @findex MEMORY_REMOVE_BREAKPOINT
3329 @findex MEMORY_INSERT_BREAKPOINT
3330 Insert or remove memory based breakpoints. Reasonable defaults
3331 (@code{default_memory_insert_breakpoint} and
3332 @code{default_memory_remove_breakpoint} respectively) have been
3333 provided so that it is not necessary to define these for most
3334 architectures. Architectures which may want to define
3335 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3336 likely have instructions that are oddly sized or are not stored in a
3337 conventional manner.
3339 It may also be desirable (from an efficiency standpoint) to define
3340 custom breakpoint insertion and removal routines if
3341 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3344 @item ADJUST_BREAKPOINT_ADDRESS (@var{address})
3345 @findex ADJUST_BREAKPOINT_ADDRESS
3346 @cindex breakpoint address adjusted
3347 Given an address at which a breakpoint is desired, return a breakpoint
3348 address adjusted to account for architectural constraints on
3349 breakpoint placement. This method is not needed by most targets.
3351 The FR-V target (see @file{frv-tdep.c}) requires this method.
3352 The FR-V is a VLIW architecture in which a number of RISC-like
3353 instructions are grouped (packed) together into an aggregate
3354 instruction or instruction bundle. When the processor executes
3355 one of these bundles, the component instructions are executed
3358 In the course of optimization, the compiler may group instructions
3359 from distinct source statements into the same bundle. The line number
3360 information associated with one of the latter statements will likely
3361 refer to some instruction other than the first one in the bundle. So,
3362 if the user attempts to place a breakpoint on one of these latter
3363 statements, @value{GDBN} must be careful to @emph{not} place the break
3364 instruction on any instruction other than the first one in the bundle.
3365 (Remember though that the instructions within a bundle execute
3366 in parallel, so the @emph{first} instruction is the instruction
3367 at the lowest address and has nothing to do with execution order.)
3369 The FR-V's @code{ADJUST_BREAKPOINT_ADDRESS} method will adjust a
3370 breakpoint's address by scanning backwards for the beginning of
3371 the bundle, returning the address of the bundle.
3373 Since the adjustment of a breakpoint may significantly alter a user's
3374 expectation, @value{GDBN} prints a warning when an adjusted breakpoint
3375 is initially set and each time that that breakpoint is hit.
3377 @item CALL_DUMMY_LOCATION
3378 @findex CALL_DUMMY_LOCATION
3379 See the file @file{inferior.h}.
3381 This method has been replaced by @code{push_dummy_code}
3382 (@pxref{push_dummy_code}).
3384 @item CANNOT_FETCH_REGISTER (@var{regno})
3385 @findex CANNOT_FETCH_REGISTER
3386 A C expression that should be nonzero if @var{regno} cannot be fetched
3387 from an inferior process. This is only relevant if
3388 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3390 @item CANNOT_STORE_REGISTER (@var{regno})
3391 @findex CANNOT_STORE_REGISTER
3392 A C expression that should be nonzero if @var{regno} should not be
3393 written to the target. This is often the case for program counters,
3394 status words, and other special registers. If this is not defined,
3395 @value{GDBN} will assume that all registers may be written.
3397 @item int CONVERT_REGISTER_P(@var{regnum})
3398 @findex CONVERT_REGISTER_P
3399 Return non-zero if register @var{regnum} can represent data values in a
3401 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3403 @item DECR_PC_AFTER_BREAK
3404 @findex DECR_PC_AFTER_BREAK
3405 Define this to be the amount by which to decrement the PC after the
3406 program encounters a breakpoint. This is often the number of bytes in
3407 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3409 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3410 @findex DISABLE_UNSETTABLE_BREAK
3411 If defined, this should evaluate to 1 if @var{addr} is in a shared
3412 library in which breakpoints cannot be set and so should be disabled.
3414 @item PRINT_FLOAT_INFO()
3415 @findex PRINT_FLOAT_INFO
3416 If defined, then the @samp{info float} command will print information about
3417 the processor's floating point unit.
3419 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3420 @findex print_registers_info
3421 If defined, pretty print the value of the register @var{regnum} for the
3422 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3423 either all registers (@var{all} is non zero) or a select subset of
3424 registers (@var{all} is zero).
3426 The default method prints one register per line, and if @var{all} is
3427 zero omits floating-point registers.
3429 @item PRINT_VECTOR_INFO()
3430 @findex PRINT_VECTOR_INFO
3431 If defined, then the @samp{info vector} command will call this function
3432 to print information about the processor's vector unit.
3434 By default, the @samp{info vector} command will print all vector
3435 registers (the register's type having the vector attribute).
3437 @item DWARF_REG_TO_REGNUM
3438 @findex DWARF_REG_TO_REGNUM
3439 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3440 no conversion will be performed.
3442 @item DWARF2_REG_TO_REGNUM
3443 @findex DWARF2_REG_TO_REGNUM
3444 Convert DWARF2 register number into @value{GDBN} regnum. If not
3445 defined, no conversion will be performed.
3447 @item ECOFF_REG_TO_REGNUM
3448 @findex ECOFF_REG_TO_REGNUM
3449 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3450 no conversion will be performed.
3452 @item END_OF_TEXT_DEFAULT
3453 @findex END_OF_TEXT_DEFAULT
3454 This is an expression that should designate the end of the text section.
3457 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3458 @findex EXTRACT_RETURN_VALUE
3459 Define this to extract a function's return value of type @var{type} from
3460 the raw register state @var{regbuf} and copy that, in virtual format,
3463 This method has been deprecated in favour of @code{gdbarch_return_value}
3464 (@pxref{gdbarch_return_value}).
3466 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3467 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS
3468 @anchor{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}
3469 When defined, extract from the array @var{regbuf} (containing the raw
3470 register state) the @code{CORE_ADDR} at which a function should return
3471 its structure value.
3473 @xref{gdbarch_return_value}.
3475 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P()
3476 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P
3477 Predicate for @code{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}.
3479 @item DEPRECATED_FP_REGNUM
3480 @findex DEPRECATED_FP_REGNUM
3481 If the virtual frame pointer is kept in a register, then define this
3482 macro to be the number (greater than or equal to zero) of that register.
3484 This should only need to be defined if @code{DEPRECATED_TARGET_READ_FP}
3487 @item DEPRECATED_FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3488 @findex DEPRECATED_FRAMELESS_FUNCTION_INVOCATION
3489 Define this to an expression that returns 1 if the function invocation
3490 represented by @var{fi} does not have a stack frame associated with it.
3493 @item frame_align (@var{address})
3494 @anchor{frame_align}
3496 Define this to adjust @var{address} so that it meets the alignment
3497 requirements for the start of a new stack frame. A stack frame's
3498 alignment requirements are typically stronger than a target processors
3499 stack alignment requirements (@pxref{DEPRECATED_STACK_ALIGN}).
3501 This function is used to ensure that, when creating a dummy frame, both
3502 the initial stack pointer and (if needed) the address of the return
3503 value are correctly aligned.
3505 Unlike @code{DEPRECATED_STACK_ALIGN}, this function always adjusts the
3506 address in the direction of stack growth.
3508 By default, no frame based stack alignment is performed.
3510 @item int frame_red_zone_size
3512 The number of bytes, beyond the innermost-stack-address, reserved by the
3513 @sc{abi}. A function is permitted to use this scratch area (instead of
3514 allocating extra stack space).
3516 When performing an inferior function call, to ensure that it does not
3517 modify this area, @value{GDBN} adjusts the innermost-stack-address by
3518 @var{frame_red_zone_size} bytes before pushing parameters onto the
3521 By default, zero bytes are allocated. The value must be aligned
3522 (@pxref{frame_align}).
3524 The @sc{amd64} (nee x86-64) @sc{abi} documentation refers to the
3525 @emph{red zone} when describing this scratch area.
3528 @item DEPRECATED_FRAME_CHAIN(@var{frame})
3529 @findex DEPRECATED_FRAME_CHAIN
3530 Given @var{frame}, return a pointer to the calling frame.
3532 @item DEPRECATED_FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3533 @findex DEPRECATED_FRAME_CHAIN_VALID
3534 Define this to be an expression that returns zero if the given frame is an
3535 outermost frame, with no caller, and nonzero otherwise. Most normal
3536 situations can be handled without defining this macro, including @code{NULL}
3537 chain pointers, dummy frames, and frames whose PC values are inside the
3538 startup file (e.g.@: @file{crt0.o}), inside @code{main}, or inside
3541 @item DEPRECATED_FRAME_INIT_SAVED_REGS(@var{frame})
3542 @findex DEPRECATED_FRAME_INIT_SAVED_REGS
3543 See @file{frame.h}. Determines the address of all registers in the
3544 current stack frame storing each in @code{frame->saved_regs}. Space for
3545 @code{frame->saved_regs} shall be allocated by
3546 @code{DEPRECATED_FRAME_INIT_SAVED_REGS} using
3547 @code{frame_saved_regs_zalloc}.
3549 @code{FRAME_FIND_SAVED_REGS} is deprecated.
3551 @item FRAME_NUM_ARGS (@var{fi})
3552 @findex FRAME_NUM_ARGS
3553 For the frame described by @var{fi} return the number of arguments that
3554 are being passed. If the number of arguments is not known, return
3557 @item DEPRECATED_FRAME_SAVED_PC(@var{frame})
3558 @findex DEPRECATED_FRAME_SAVED_PC
3559 @anchor{DEPRECATED_FRAME_SAVED_PC} Given @var{frame}, return the pc
3560 saved there. This is the return address.
3562 This method is deprecated. @xref{unwind_pc}.
3564 @item CORE_ADDR unwind_pc (struct frame_info *@var{this_frame})
3566 @anchor{unwind_pc} Return the instruction address, in @var{this_frame}'s
3567 caller, at which execution will resume after @var{this_frame} returns.
3568 This is commonly referred to as the return address.
3570 The implementation, which must be frame agnostic (work with any frame),
3571 is typically no more than:
3575 frame_unwind_unsigned_register (this_frame, D10V_PC_REGNUM, &pc);
3576 return d10v_make_iaddr (pc);
3580 @xref{DEPRECATED_FRAME_SAVED_PC}, which this method replaces.
3582 @item CORE_ADDR unwind_sp (struct frame_info *@var{this_frame})
3584 @anchor{unwind_sp} Return the frame's inner most stack address. This is
3585 commonly referred to as the frame's @dfn{stack pointer}.
3587 The implementation, which must be frame agnostic (work with any frame),
3588 is typically no more than:
3592 frame_unwind_unsigned_register (this_frame, D10V_SP_REGNUM, &sp);
3593 return d10v_make_daddr (sp);
3597 @xref{TARGET_READ_SP}, which this method replaces.
3599 @item FUNCTION_EPILOGUE_SIZE
3600 @findex FUNCTION_EPILOGUE_SIZE
3601 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3602 function end symbol is 0. For such targets, you must define
3603 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3604 function's epilogue.
3606 @item DEPRECATED_FUNCTION_START_OFFSET
3607 @findex DEPRECATED_FUNCTION_START_OFFSET
3608 An integer, giving the offset in bytes from a function's address (as
3609 used in the values of symbols, function pointers, etc.), and the
3610 function's first genuine instruction.
3612 This is zero on almost all machines: the function's address is usually
3613 the address of its first instruction. However, on the VAX, for
3614 example, each function starts with two bytes containing a bitmask
3615 indicating which registers to save upon entry to the function. The
3616 VAX @code{call} instructions check this value, and save the
3617 appropriate registers automatically. Thus, since the offset from the
3618 function's address to its first instruction is two bytes,
3619 @code{DEPRECATED_FUNCTION_START_OFFSET} would be 2 on the VAX.
3621 @item GCC_COMPILED_FLAG_SYMBOL
3622 @itemx GCC2_COMPILED_FLAG_SYMBOL
3623 @findex GCC2_COMPILED_FLAG_SYMBOL
3624 @findex GCC_COMPILED_FLAG_SYMBOL
3625 If defined, these are the names of the symbols that @value{GDBN} will
3626 look for to detect that GCC compiled the file. The default symbols
3627 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3628 respectively. (Currently only defined for the Delta 68.)
3630 @item @value{GDBN}_MULTI_ARCH
3631 @findex @value{GDBN}_MULTI_ARCH
3632 If defined and non-zero, enables support for multiple architectures
3633 within @value{GDBN}.
3635 This support can be enabled at two levels. At level one, only
3636 definitions for previously undefined macros are provided; at level two,
3637 a multi-arch definition of all architecture dependent macros will be
3640 @item @value{GDBN}_TARGET_IS_HPPA
3641 @findex @value{GDBN}_TARGET_IS_HPPA
3642 This determines whether horrible kludge code in @file{dbxread.c} and
3643 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3644 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3647 @item GET_LONGJMP_TARGET
3648 @findex GET_LONGJMP_TARGET
3649 For most machines, this is a target-dependent parameter. On the
3650 DECstation and the Iris, this is a native-dependent parameter, since
3651 the header file @file{setjmp.h} is needed to define it.
3653 This macro determines the target PC address that @code{longjmp} will jump to,
3654 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3655 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3656 pointer. It examines the current state of the machine as needed.
3658 @item DEPRECATED_GET_SAVED_REGISTER
3659 @findex DEPRECATED_GET_SAVED_REGISTER
3660 Define this if you need to supply your own definition for the function
3661 @code{DEPRECATED_GET_SAVED_REGISTER}.
3663 @item DEPRECATED_IBM6000_TARGET
3664 @findex DEPRECATED_IBM6000_TARGET
3665 Shows that we are configured for an IBM RS/6000 system. This
3666 conditional should be eliminated (FIXME) and replaced by
3667 feature-specific macros. It was introduced in a haste and we are
3668 repenting at leisure.
3670 @item I386_USE_GENERIC_WATCHPOINTS
3671 An x86-based target can define this to use the generic x86 watchpoint
3672 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3674 @item SYMBOLS_CAN_START_WITH_DOLLAR
3675 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3676 Some systems have routines whose names start with @samp{$}. Giving this
3677 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3678 routines when parsing tokens that begin with @samp{$}.
3680 On HP-UX, certain system routines (millicode) have names beginning with
3681 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3682 routine that handles inter-space procedure calls on PA-RISC.
3684 @item DEPRECATED_INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3685 @findex DEPRECATED_INIT_EXTRA_FRAME_INFO
3686 If additional information about the frame is required this should be
3687 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3688 is allocated using @code{frame_extra_info_zalloc}.
3690 @item DEPRECATED_INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3691 @findex DEPRECATED_INIT_FRAME_PC
3692 This is a C statement that sets the pc of the frame pointed to by
3693 @var{prev}. [By default...]
3695 @item INNER_THAN (@var{lhs}, @var{rhs})
3697 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3698 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3699 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3702 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3703 @findex gdbarch_in_function_epilogue_p
3704 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3705 The epilogue of a function is defined as the part of a function where
3706 the stack frame of the function already has been destroyed up to the
3707 final `return from function call' instruction.
3709 @item DEPRECATED_SIGTRAMP_START (@var{pc})
3710 @findex DEPRECATED_SIGTRAMP_START
3711 @itemx DEPRECATED_SIGTRAMP_END (@var{pc})
3712 @findex DEPRECATED_SIGTRAMP_END
3713 Define these to be the start and end address of the @code{sigtramp} for the
3714 given @var{pc}. On machines where the address is just a compile time
3715 constant, the macro expansion will typically just ignore the supplied
3718 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3719 @findex IN_SOLIB_CALL_TRAMPOLINE
3720 Define this to evaluate to nonzero if the program is stopped in the
3721 trampoline that connects to a shared library.
3723 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3724 @findex IN_SOLIB_RETURN_TRAMPOLINE
3725 Define this to evaluate to nonzero if the program is stopped in the
3726 trampoline that returns from a shared library.
3728 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3729 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3730 Define this to evaluate to nonzero if the program is stopped in the
3733 @item SKIP_SOLIB_RESOLVER (@var{pc})
3734 @findex SKIP_SOLIB_RESOLVER
3735 Define this to evaluate to the (nonzero) address at which execution
3736 should continue to get past the dynamic linker's symbol resolution
3737 function. A zero value indicates that it is not important or necessary
3738 to set a breakpoint to get through the dynamic linker and that single
3739 stepping will suffice.
3741 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3742 @findex INTEGER_TO_ADDRESS
3743 @cindex converting integers to addresses
3744 Define this when the architecture needs to handle non-pointer to address
3745 conversions specially. Converts that value to an address according to
3746 the current architectures conventions.
3748 @emph{Pragmatics: When the user copies a well defined expression from
3749 their source code and passes it, as a parameter, to @value{GDBN}'s
3750 @code{print} command, they should get the same value as would have been
3751 computed by the target program. Any deviation from this rule can cause
3752 major confusion and annoyance, and needs to be justified carefully. In
3753 other words, @value{GDBN} doesn't really have the freedom to do these
3754 conversions in clever and useful ways. It has, however, been pointed
3755 out that users aren't complaining about how @value{GDBN} casts integers
3756 to pointers; they are complaining that they can't take an address from a
3757 disassembly listing and give it to @code{x/i}. Adding an architecture
3758 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3759 @value{GDBN} to ``get it right'' in all circumstances.}
3761 @xref{Target Architecture Definition, , Pointers Are Not Always
3764 @item NO_HIF_SUPPORT
3765 @findex NO_HIF_SUPPORT
3766 (Specific to the a29k.)
3768 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3769 @findex POINTER_TO_ADDRESS
3770 Assume that @var{buf} holds a pointer of type @var{type}, in the
3771 appropriate format for the current architecture. Return the byte
3772 address the pointer refers to.
3773 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3775 @item REGISTER_CONVERTIBLE (@var{reg})
3776 @findex REGISTER_CONVERTIBLE
3777 Return non-zero if @var{reg} uses different raw and virtual formats.
3778 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3780 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3781 @findex REGISTER_TO_VALUE
3782 Convert the raw contents of register @var{regnum} into a value of type
3784 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3786 @item DEPRECATED_REGISTER_RAW_SIZE (@var{reg})
3787 @findex DEPRECATED_REGISTER_RAW_SIZE
3788 Return the raw size of @var{reg}; defaults to the size of the register's
3790 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3792 @item register_reggroup_p (@var{gdbarch}, @var{regnum}, @var{reggroup})
3793 @findex register_reggroup_p
3794 @cindex register groups
3795 Return non-zero if register @var{regnum} is a member of the register
3796 group @var{reggroup}.
3798 By default, registers are grouped as follows:
3801 @item float_reggroup
3802 Any register with a valid name and a floating-point type.
3803 @item vector_reggroup
3804 Any register with a valid name and a vector type.
3805 @item general_reggroup
3806 Any register with a valid name and a type other than vector or
3807 floating-point. @samp{float_reggroup}.
3809 @itemx restore_reggroup
3811 Any register with a valid name.
3814 @item DEPRECATED_REGISTER_VIRTUAL_SIZE (@var{reg})
3815 @findex DEPRECATED_REGISTER_VIRTUAL_SIZE
3816 Return the virtual size of @var{reg}; defaults to the size of the
3817 register's virtual type.
3818 Return the virtual size of @var{reg}.
3819 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3821 @item DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})
3822 @findex REGISTER_VIRTUAL_TYPE
3823 Return the virtual type of @var{reg}.
3824 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3826 @item struct type *register_type (@var{gdbarch}, @var{reg})
3827 @findex register_type
3828 If defined, return the type of register @var{reg}. This function
3829 supersedes @code{DEPRECATED_REGISTER_VIRTUAL_TYPE}. @xref{Target Architecture
3830 Definition, , Raw and Virtual Register Representations}.
3832 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3833 @findex REGISTER_CONVERT_TO_VIRTUAL
3834 Convert the value of register @var{reg} from its raw form to its virtual
3836 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3838 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3839 @findex REGISTER_CONVERT_TO_RAW
3840 Convert the value of register @var{reg} from its virtual form to its raw
3842 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3844 @item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size})
3845 @findex regset_from_core_section
3846 Return the appropriate register set for a core file section with name
3847 @var{sect_name} and size @var{sect_size}.
3849 @item SOFTWARE_SINGLE_STEP_P()
3850 @findex SOFTWARE_SINGLE_STEP_P
3851 Define this as 1 if the target does not have a hardware single-step
3852 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3854 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p})
3855 @findex SOFTWARE_SINGLE_STEP
3856 A function that inserts or removes (depending on
3857 @var{insert_breakpoints_p}) breakpoints at each possible destinations of
3858 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3861 @item SOFUN_ADDRESS_MAYBE_MISSING
3862 @findex SOFUN_ADDRESS_MAYBE_MISSING
3863 Somebody clever observed that, the more actual addresses you have in the
3864 debug information, the more time the linker has to spend relocating
3865 them. So whenever there's some other way the debugger could find the
3866 address it needs, you should omit it from the debug info, to make
3869 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3870 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3871 entries in stabs-format debugging information. @code{N_SO} stabs mark
3872 the beginning and ending addresses of compilation units in the text
3873 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3875 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3879 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3880 addresses where the function starts by taking the function name from
3881 the stab, and then looking that up in the minsyms (the
3882 linker/assembler symbol table). In other words, the stab has the
3883 name, and the linker/assembler symbol table is the only place that carries
3887 @code{N_SO} stabs have an address of zero, too. You just look at the
3888 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3889 and guess the starting and ending addresses of the compilation unit from
3893 @item PC_LOAD_SEGMENT
3894 @findex PC_LOAD_SEGMENT
3895 If defined, print information about the load segment for the program
3896 counter. (Defined only for the RS/6000.)
3900 If the program counter is kept in a register, then define this macro to
3901 be the number (greater than or equal to zero) of that register.
3903 This should only need to be defined if @code{TARGET_READ_PC} and
3904 @code{TARGET_WRITE_PC} are not defined.
3907 @findex PARM_BOUNDARY
3908 If non-zero, round arguments to a boundary of this many bits before
3909 pushing them on the stack.
3911 @item stabs_argument_has_addr (@var{gdbarch}, @var{type})
3912 @findex stabs_argument_has_addr
3913 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3914 @anchor{stabs_argument_has_addr} Define this to return nonzero if a
3915 function argument of type @var{type} is passed by reference instead of
3918 This method replaces @code{DEPRECATED_REG_STRUCT_HAS_ADDR}
3919 (@pxref{DEPRECATED_REG_STRUCT_HAS_ADDR}).
3921 @item PROCESS_LINENUMBER_HOOK
3922 @findex PROCESS_LINENUMBER_HOOK
3923 A hook defined for XCOFF reading.
3925 @item PROLOGUE_FIRSTLINE_OVERLAP
3926 @findex PROLOGUE_FIRSTLINE_OVERLAP
3927 (Only used in unsupported Convex configuration.)
3931 If defined, this is the number of the processor status register. (This
3932 definition is only used in generic code when parsing "$ps".)
3934 @item DEPRECATED_POP_FRAME
3935 @findex DEPRECATED_POP_FRAME
3937 If defined, used by @code{frame_pop} to remove a stack frame. This
3938 method has been superseded by generic code.
3940 @item push_dummy_call (@var{gdbarch}, @var{function}, @var{regcache}, @var{pc_addr}, @var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
3941 @findex push_dummy_call
3942 @findex DEPRECATED_PUSH_ARGUMENTS.
3943 @anchor{push_dummy_call} Define this to push the dummy frame's call to
3944 the inferior function onto the stack. In addition to pushing
3945 @var{nargs}, the code should push @var{struct_addr} (when
3946 @var{struct_return}), and the return address (@var{bp_addr}).
3948 @var{function} is a pointer to a @code{struct value}; on architectures that use
3949 function descriptors, this contains the function descriptor value.
3951 Returns the updated top-of-stack pointer.
3953 This method replaces @code{DEPRECATED_PUSH_ARGUMENTS}.
3955 @item CORE_ADDR 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})
3956 @findex push_dummy_code
3957 @anchor{push_dummy_code} Given a stack based call dummy, push the
3958 instruction sequence (including space for a breakpoint) to which the
3959 called function should return.
3961 Set @var{bp_addr} to the address at which the breakpoint instruction
3962 should be inserted, @var{real_pc} to the resume address when starting
3963 the call sequence, and return the updated inner-most stack address.
3965 By default, the stack is grown sufficient to hold a frame-aligned
3966 (@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address
3967 reserved for that breakpoint, and @var{real_pc} set to @var{funaddr}.
3969 This method replaces @code{CALL_DUMMY_LOCATION},
3970 @code{DEPRECATED_REGISTER_SIZE}.
3972 @item REGISTER_NAME(@var{i})
3973 @findex REGISTER_NAME
3974 Return the name of register @var{i} as a string. May return @code{NULL}
3975 or @code{NUL} to indicate that register @var{i} is not valid.
3977 @item DEPRECATED_REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3978 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3979 @anchor{DEPRECATED_REG_STRUCT_HAS_ADDR}Define this to return 1 if the
3980 given type will be passed by pointer rather than directly.
3982 This method has been replaced by @code{stabs_argument_has_addr}
3983 (@pxref{stabs_argument_has_addr}).
3985 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3986 @findex SAVE_DUMMY_FRAME_TOS
3987 @anchor{SAVE_DUMMY_FRAME_TOS} Used in @samp{call_function_by_hand} to
3988 notify the target dependent code of the top-of-stack value that will be
3989 passed to the inferior code. This is the value of the @code{SP}
3990 after both the dummy frame and space for parameters/results have been
3991 allocated on the stack. @xref{unwind_dummy_id}.
3993 @item SDB_REG_TO_REGNUM
3994 @findex SDB_REG_TO_REGNUM
3995 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3996 defined, no conversion will be done.
3998 @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})
3999 @findex gdbarch_return_value
4000 @anchor{gdbarch_return_value} Given a function with a return-value of
4001 type @var{rettype}, return which return-value convention that function
4004 @value{GDBN} currently recognizes two function return-value conventions:
4005 @code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found
4006 in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return
4007 value is found in memory and the address of that memory location is
4008 passed in as the function's first parameter.
4010 If the register convention is being used, and @var{writebuf} is
4011 non-@code{NULL}, also copy the return-value in @var{writebuf} into
4014 If the register convention is being used, and @var{readbuf} is
4015 non-@code{NULL}, also copy the return value from @var{regcache} into
4016 @var{readbuf} (@var{regcache} contains a copy of the registers from the
4017 just returned function).
4019 @xref{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}, for a description of how
4020 return-values that use the struct convention are handled.
4022 @emph{Maintainer note: This method replaces separate predicate, extract,
4023 store methods. By having only one method, the logic needed to determine
4024 the return-value convention need only be implemented in one place. If
4025 @value{GDBN} were written in an @sc{oo} language, this method would
4026 instead return an object that knew how to perform the register
4027 return-value extract and store.}
4029 @emph{Maintainer note: This method does not take a @var{gcc_p}
4030 parameter, and such a parameter should not be added. If an architecture
4031 that requires per-compiler or per-function information be identified,
4032 then the replacement of @var{rettype} with @code{struct value}
4033 @var{function} should be pursued.}
4035 @emph{Maintainer note: The @var{regcache} parameter limits this methods
4036 to the inner most frame. While replacing @var{regcache} with a
4037 @code{struct frame_info} @var{frame} parameter would remove that
4038 limitation there has yet to be a demonstrated need for such a change.}
4040 @item SKIP_PERMANENT_BREAKPOINT
4041 @findex SKIP_PERMANENT_BREAKPOINT
4042 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
4043 steps over a breakpoint by removing it, stepping one instruction, and
4044 re-inserting the breakpoint. However, permanent breakpoints are
4045 hardwired into the inferior, and can't be removed, so this strategy
4046 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
4047 state so that execution will resume just after the breakpoint. This
4048 macro does the right thing even when the breakpoint is in the delay slot
4049 of a branch or jump.
4051 @item SKIP_PROLOGUE (@var{pc})
4052 @findex SKIP_PROLOGUE
4053 A C expression that returns the address of the ``real'' code beyond the
4054 function entry prologue found at @var{pc}.
4056 @item SKIP_TRAMPOLINE_CODE (@var{pc})
4057 @findex SKIP_TRAMPOLINE_CODE
4058 If the target machine has trampoline code that sits between callers and
4059 the functions being called, then define this macro to return a new PC
4060 that is at the start of the real function.
4064 If the stack-pointer is kept in a register, then define this macro to be
4065 the number (greater than or equal to zero) of that register, or -1 if
4066 there is no such register.
4068 @item STAB_REG_TO_REGNUM
4069 @findex STAB_REG_TO_REGNUM
4070 Define this to convert stab register numbers (as gotten from `r'
4071 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
4074 @item DEPRECATED_STACK_ALIGN (@var{addr})
4075 @anchor{DEPRECATED_STACK_ALIGN}
4076 @findex DEPRECATED_STACK_ALIGN
4077 Define this to increase @var{addr} so that it meets the alignment
4078 requirements for the processor's stack.
4080 Unlike @ref{frame_align}, this function always adjusts @var{addr}
4083 By default, no stack alignment is performed.
4085 @item STEP_SKIPS_DELAY (@var{addr})
4086 @findex STEP_SKIPS_DELAY
4087 Define this to return true if the address is of an instruction with a
4088 delay slot. If a breakpoint has been placed in the instruction's delay
4089 slot, @value{GDBN} will single-step over that instruction before resuming
4090 normally. Currently only defined for the Mips.
4092 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
4093 @findex STORE_RETURN_VALUE
4094 A C expression that writes the function return value, found in
4095 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
4096 value that is to be returned.
4098 This method has been deprecated in favour of @code{gdbarch_return_value}
4099 (@pxref{gdbarch_return_value}).
4101 @item SYMBOL_RELOADING_DEFAULT
4102 @findex SYMBOL_RELOADING_DEFAULT
4103 The default value of the ``symbol-reloading'' variable. (Never defined in
4106 @item TARGET_CHAR_BIT
4107 @findex TARGET_CHAR_BIT
4108 Number of bits in a char; defaults to 8.
4110 @item TARGET_CHAR_SIGNED
4111 @findex TARGET_CHAR_SIGNED
4112 Non-zero if @code{char} is normally signed on this architecture; zero if
4113 it should be unsigned.
4115 The ISO C standard requires the compiler to treat @code{char} as
4116 equivalent to either @code{signed char} or @code{unsigned char}; any
4117 character in the standard execution set is supposed to be positive.
4118 Most compilers treat @code{char} as signed, but @code{char} is unsigned
4119 on the IBM S/390, RS6000, and PowerPC targets.
4121 @item TARGET_COMPLEX_BIT
4122 @findex TARGET_COMPLEX_BIT
4123 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
4125 At present this macro is not used.
4127 @item TARGET_DOUBLE_BIT
4128 @findex TARGET_DOUBLE_BIT
4129 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
4131 @item TARGET_DOUBLE_COMPLEX_BIT
4132 @findex TARGET_DOUBLE_COMPLEX_BIT
4133 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
4135 At present this macro is not used.
4137 @item TARGET_FLOAT_BIT
4138 @findex TARGET_FLOAT_BIT
4139 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
4141 @item TARGET_INT_BIT
4142 @findex TARGET_INT_BIT
4143 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4145 @item TARGET_LONG_BIT
4146 @findex TARGET_LONG_BIT
4147 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4149 @item TARGET_LONG_DOUBLE_BIT
4150 @findex TARGET_LONG_DOUBLE_BIT
4151 Number of bits in a long double float;
4152 defaults to @code{2 * TARGET_DOUBLE_BIT}.
4154 @item TARGET_LONG_LONG_BIT
4155 @findex TARGET_LONG_LONG_BIT
4156 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
4158 @item TARGET_PTR_BIT
4159 @findex TARGET_PTR_BIT
4160 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
4162 @item TARGET_SHORT_BIT
4163 @findex TARGET_SHORT_BIT
4164 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
4166 @item TARGET_READ_PC
4167 @findex TARGET_READ_PC
4168 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
4169 @findex TARGET_WRITE_PC
4170 @anchor{TARGET_WRITE_PC}
4171 @itemx TARGET_READ_SP
4172 @findex TARGET_READ_SP
4173 @itemx TARGET_READ_FP
4174 @findex TARGET_READ_FP
4179 @anchor{TARGET_READ_SP} These change the behavior of @code{read_pc},
4180 @code{write_pc}, and @code{read_sp}. For most targets, these may be
4181 left undefined. @value{GDBN} will call the read and write register
4182 functions with the relevant @code{_REGNUM} argument.
4184 These macros are useful when a target keeps one of these registers in a
4185 hard to get at place; for example, part in a segment register and part
4186 in an ordinary register.
4188 @xref{unwind_sp}, which replaces @code{TARGET_READ_SP}.
4190 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
4191 @findex TARGET_VIRTUAL_FRAME_POINTER
4192 Returns a @code{(register, offset)} pair representing the virtual frame
4193 pointer in use at the code address @var{pc}. If virtual frame pointers
4194 are not used, a default definition simply returns
4195 @code{DEPRECATED_FP_REGNUM}, with an offset of zero.
4197 @item TARGET_HAS_HARDWARE_WATCHPOINTS
4198 If non-zero, the target has support for hardware-assisted
4199 watchpoints. @xref{Algorithms, watchpoints}, for more details and
4200 other related macros.
4202 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
4203 @findex TARGET_PRINT_INSN
4204 This is the function used by @value{GDBN} to print an assembly
4205 instruction. It prints the instruction at address @var{addr} in
4206 debugged memory and returns the length of the instruction, in bytes. If
4207 a target doesn't define its own printing routine, it defaults to an
4208 accessor function for the global pointer
4209 @code{deprecated_tm_print_insn}. This usually points to a function in
4210 the @code{opcodes} library (@pxref{Support Libraries, ,Opcodes}).
4211 @var{info} is a structure (of type @code{disassemble_info}) defined in
4212 @file{include/dis-asm.h} used to pass information to the instruction
4215 @item struct frame_id unwind_dummy_id (struct frame_info *@var{frame})
4216 @findex unwind_dummy_id
4217 @anchor{unwind_dummy_id} Given @var{frame} return a @code{struct
4218 frame_id} that uniquely identifies an inferior function call's dummy
4219 frame. The value returned must match the dummy frame stack value
4220 previously saved using @code{SAVE_DUMMY_FRAME_TOS}.
4221 @xref{SAVE_DUMMY_FRAME_TOS}.
4223 @item DEPRECATED_USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
4224 @findex DEPRECATED_USE_STRUCT_CONVENTION
4225 If defined, this must be an expression that is nonzero if a value of the
4226 given @var{type} being returned from a function must have space
4227 allocated for it on the stack. @var{gcc_p} is true if the function
4228 being considered is known to have been compiled by GCC; this is helpful
4229 for systems where GCC is known to use different calling convention than
4232 This method has been deprecated in favour of @code{gdbarch_return_value}
4233 (@pxref{gdbarch_return_value}).
4235 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
4236 @findex VALUE_TO_REGISTER
4237 Convert a value of type @var{type} into the raw contents of register
4239 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4241 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4242 @findex VARIABLES_INSIDE_BLOCK
4243 For dbx-style debugging information, if the compiler puts variable
4244 declarations inside LBRAC/RBRAC blocks, this should be defined to be
4245 nonzero. @var{desc} is the value of @code{n_desc} from the
4246 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
4247 presence of either the @code{GCC_COMPILED_SYMBOL} or the
4248 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
4250 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4251 @findex OS9K_VARIABLES_INSIDE_BLOCK
4252 Similarly, for OS/9000. Defaults to 1.
4255 Motorola M68K target conditionals.
4259 Define this to be the 4-bit location of the breakpoint trap vector. If
4260 not defined, it will default to @code{0xf}.
4262 @item REMOTE_BPT_VECTOR
4263 Defaults to @code{1}.
4265 @item NAME_OF_MALLOC
4266 @findex NAME_OF_MALLOC
4267 A string containing the name of the function to call in order to
4268 allocate some memory in the inferior. The default value is "malloc".
4272 @section Adding a New Target
4274 @cindex adding a target
4275 The following files add a target to @value{GDBN}:
4279 @item gdb/config/@var{arch}/@var{ttt}.mt
4280 Contains a Makefile fragment specific to this target. Specifies what
4281 object files are needed for target @var{ttt}, by defining
4282 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
4283 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
4286 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
4287 but these are now deprecated, replaced by autoconf, and may go away in
4288 future versions of @value{GDBN}.
4290 @item gdb/@var{ttt}-tdep.c
4291 Contains any miscellaneous code required for this target machine. On
4292 some machines it doesn't exist at all. Sometimes the macros in
4293 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
4294 as functions here instead, and the macro is simply defined to call the
4295 function. This is vastly preferable, since it is easier to understand
4298 @item gdb/@var{arch}-tdep.c
4299 @itemx gdb/@var{arch}-tdep.h
4300 This often exists to describe the basic layout of the target machine's
4301 processor chip (registers, stack, etc.). If used, it is included by
4302 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
4305 @item gdb/config/@var{arch}/tm-@var{ttt}.h
4306 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
4307 macro definitions about the target machine's registers, stack frame
4308 format and instructions.
4310 New targets do not need this file and should not create it.
4312 @item gdb/config/@var{arch}/tm-@var{arch}.h
4313 This often exists to describe the basic layout of the target machine's
4314 processor chip (registers, stack, etc.). If used, it is included by
4315 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
4318 New targets do not need this file and should not create it.
4322 If you are adding a new operating system for an existing CPU chip, add a
4323 @file{config/tm-@var{os}.h} file that describes the operating system
4324 facilities that are unusual (extra symbol table info; the breakpoint
4325 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
4326 that just @code{#include}s @file{tm-@var{arch}.h} and
4327 @file{config/tm-@var{os}.h}.
4330 @section Converting an existing Target Architecture to Multi-arch
4331 @cindex converting targets to multi-arch
4333 This section describes the current accepted best practice for converting
4334 an existing target architecture to the multi-arch framework.
4336 The process consists of generating, testing, posting and committing a
4337 sequence of patches. Each patch must contain a single change, for
4343 Directly convert a group of functions into macros (the conversion does
4344 not change the behavior of any of the functions).
4347 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4351 Enable multi-arch level one.
4354 Delete one or more files.
4359 There isn't a size limit on a patch, however, a developer is strongly
4360 encouraged to keep the patch size down.
4362 Since each patch is well defined, and since each change has been tested
4363 and shows no regressions, the patches are considered @emph{fairly}
4364 obvious. Such patches, when submitted by developers listed in the
4365 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4366 process may be more complicated and less clear. The developer is
4367 expected to use their judgment and is encouraged to seek advice as
4370 @subsection Preparation
4372 The first step is to establish control. Build (with @option{-Werror}
4373 enabled) and test the target so that there is a baseline against which
4374 the debugger can be compared.
4376 At no stage can the test results regress or @value{GDBN} stop compiling
4377 with @option{-Werror}.
4379 @subsection Add the multi-arch initialization code
4381 The objective of this step is to establish the basic multi-arch
4382 framework. It involves
4387 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4388 above is from the original example and uses K&R C. @value{GDBN}
4389 has since converted to ISO C but lets ignore that.} that creates
4392 static struct gdbarch *
4393 d10v_gdbarch_init (info, arches)
4394 struct gdbarch_info info;
4395 struct gdbarch_list *arches;
4397 struct gdbarch *gdbarch;
4398 /* there is only one d10v architecture */
4400 return arches->gdbarch;
4401 gdbarch = gdbarch_alloc (&info, NULL);
4409 A per-architecture dump function to print any architecture specific
4413 mips_dump_tdep (struct gdbarch *current_gdbarch,
4414 struct ui_file *file)
4416 @dots{} code to print architecture specific info @dots{}
4421 A change to @code{_initialize_@var{arch}_tdep} to register this new
4425 _initialize_mips_tdep (void)
4427 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4432 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4433 @file{config/@var{arch}/tm-@var{arch}.h}.
4437 @subsection Update multi-arch incompatible mechanisms
4439 Some mechanisms do not work with multi-arch. They include:
4442 @item FRAME_FIND_SAVED_REGS
4443 Replaced with @code{DEPRECATED_FRAME_INIT_SAVED_REGS}
4447 At this stage you could also consider converting the macros into
4450 @subsection Prepare for multi-arch level to one
4452 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4453 and then build and start @value{GDBN} (the change should not be
4454 committed). @value{GDBN} may not build, and once built, it may die with
4455 an internal error listing the architecture methods that must be
4458 Fix any build problems (patch(es)).
4460 Convert all the architecture methods listed, which are only macros, into
4461 functions (patch(es)).
4463 Update @code{@var{arch}_gdbarch_init} to set all the missing
4464 architecture methods and wrap the corresponding macros in @code{#if
4465 !GDB_MULTI_ARCH} (patch(es)).
4467 @subsection Set multi-arch level one
4469 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4472 Any problems with throwing ``the switch'' should have been fixed
4475 @subsection Convert remaining macros
4477 Suggest converting macros into functions (and setting the corresponding
4478 architecture method) in small batches.
4480 @subsection Set multi-arch level to two
4482 This should go smoothly.
4484 @subsection Delete the TM file
4486 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4487 @file{configure.in} updated.
4490 @node Target Descriptions
4491 @chapter Target Descriptions
4492 @cindex target descriptions
4494 The target architecture definition (@pxref{Target Architecture Definition})
4495 contains @value{GDBN}'s hard-coded knowledge about an architecture. For
4496 some platforms, it is handy to have more flexible knowledge about a specific
4497 instance of the architecture---for instance, a processor or development board.
4498 @dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN}
4499 more about what their target supports, or for the target to tell @value{GDBN}
4502 For details on writing, automatically supplying, and manually selecting
4503 target descriptions, see @ref{Target Descriptions, , , gdb,
4504 Debugging with @value{GDBN}}. This section will cover some related
4505 topics about the @value{GDBN} internals.
4508 * Target Descriptions Implementation::
4509 * Adding Target Described Register Support::
4512 @node Target Descriptions Implementation
4513 @section Target Descriptions Implementation
4514 @cindex target descriptions, implementation
4516 Before @value{GDBN} connects to a new target, or runs a new program on
4517 an existing target, it discards any existing target description and
4518 reverts to a default gdbarch. Then, after connecting, it looks for a
4519 new target description by calling @code{target_find_description}.
4521 A description may come from a user specified file (XML), the remote
4522 @samp{qXfer:features:read} packet (also XML), or from any custom
4523 @code{to_read_description} routine in the target vector. For instance,
4524 the remote target supports guessing whether a MIPS target is 32-bit or
4525 64-bit based on the size of the @samp{g} packet.
4527 If any target description is found, @value{GDBN} creates a new gdbarch
4528 incorporating the description by calling @code{gdbarch_update_p}. Any
4529 @samp{<architecture>} element is handled first, to determine which
4530 architecture's gdbarch initialization routine is called to create the
4531 new architecture. Then the initialization routine is called, and has
4532 a chance to adjust the constructed architecture based on the contents
4533 of the target description. For instance, it can recognize any
4534 properties set by a @code{to_read_description} routine. Also
4535 see @ref{Adding Target Described Register Support}.
4537 @node Adding Target Described Register Support
4538 @section Adding Target Described Register Support
4539 @cindex target descriptions, adding register support
4541 Target descriptions can report additional registers specific to an
4542 instance of the target. But it takes a little work in the architecture
4543 specific routines to support this.
4545 A target description must either have no registers or a complete
4546 set---this avoids complexity in trying to merge standard registers
4547 with the target defined registers. It is the architecture's
4548 responsibility to validate that a description with registers has
4549 everything it needs. To keep architecture code simple, the same
4550 mechanism is used to assign fixed internal register numbers to
4553 If @code{tdesc_has_registers} returns 1, the description contains
4554 registers. The architecture's @code{gdbarch_init} routine should:
4559 Call @code{tdesc_data_alloc} to allocate storage, early, before
4560 searching for a matching gdbarch or allocating a new one.
4563 Use @code{tdesc_find_feature} to locate standard features by name.
4566 Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices}
4567 to locate the expected registers in the standard features.
4570 Return @code{NULL} if a required feature is missing, or if any standard
4571 feature is missing expected registers. This will produce a warning that
4572 the description was incomplete.
4575 Free the allocated data before returning, unless @code{tdesc_use_registers}
4579 Call @code{set_gdbarch_num_regs} as usual, with a number higher than any
4580 fixed number passed to @code{tdesc_numbered_register}.
4583 Call @code{tdesc_use_registers} after creating a new gdbarch, before
4588 After @code{tdesc_use_registers} has been called, the architecture's
4589 @code{register_name}, @code{register_type}, and @code{register_reggroup_p}
4590 routines will not be called; that information will be taken from
4591 the target description. @code{num_regs} may be increased to account
4592 for any additional registers in the description.
4594 Pseudo-registers require some extra care:
4599 Using @code{tdesc_numbered_register} allows the architecture to give
4600 constant register numbers to standard architectural registers, e.g.@:
4601 as an @code{enum} in @file{@var{arch}-tdep.h}. But because
4602 pseudo-registers are always numbered above @code{num_regs},
4603 which may be increased by the description, constant numbers
4604 can not be used for pseudos. They must be numbered relative to
4605 @code{num_regs} instead.
4608 The description will not describe pseudo-registers, so the
4609 architecture must call @code{set_tdesc_pseudo_register_name},
4610 @code{set_tdesc_pseudo_register_type}, and
4611 @code{set_tdesc_pseudo_register_reggroup_p} to supply routines
4612 describing pseudo registers. These routines will be passed
4613 internal register numbers, so the same routines used for the
4614 gdbarch equivalents are usually suitable.
4619 @node Target Vector Definition
4621 @chapter Target Vector Definition
4622 @cindex target vector
4624 The target vector defines the interface between @value{GDBN}'s
4625 abstract handling of target systems, and the nitty-gritty code that
4626 actually exercises control over a process or a serial port.
4627 @value{GDBN} includes some 30-40 different target vectors; however,
4628 each configuration of @value{GDBN} includes only a few of them.
4631 * Managing Execution State::
4632 * Existing Targets::
4635 @node Managing Execution State
4636 @section Managing Execution State
4637 @cindex execution state
4639 A target vector can be completely inactive (not pushed on the target
4640 stack), active but not running (pushed, but not connected to a fully
4641 manifested inferior), or completely active (pushed, with an accessible
4642 inferior). Most targets are only completely inactive or completely
4643 active, but some support persistent connections to a target even
4644 when the target has exited or not yet started.
4646 For example, connecting to the simulator using @code{target sim} does
4647 not create a running program. Neither registers nor memory are
4648 accessible until @code{run}. Similarly, after @code{kill}, the
4649 program can not continue executing. But in both cases @value{GDBN}
4650 remains connected to the simulator, and target-specific commands
4651 are directed to the simulator.
4653 A target which only supports complete activation should push itself
4654 onto the stack in its @code{to_open} routine (by calling
4655 @code{push_target}), and unpush itself from the stack in its
4656 @code{to_mourn_inferior} routine (by calling @code{unpush_target}).
4658 A target which supports both partial and complete activation should
4659 still call @code{push_target} in @code{to_open}, but not call
4660 @code{unpush_target} in @code{to_mourn_inferior}. Instead, it should
4661 call either @code{target_mark_running} or @code{target_mark_exited}
4662 in its @code{to_open}, depending on whether the target is fully active
4663 after connection. It should also call @code{target_mark_running} any
4664 time the inferior becomes fully active (e.g.@: in
4665 @code{to_create_inferior} and @code{to_attach}), and
4666 @code{target_mark_exited} when the inferior becomes inactive (in
4667 @code{to_mourn_inferior}). The target should also make sure to call
4668 @code{target_mourn_inferior} from its @code{to_kill}, to return the
4669 target to inactive state.
4671 @node Existing Targets
4672 @section Existing Targets
4675 @subsection File Targets
4677 Both executables and core files have target vectors.
4679 @subsection Standard Protocol and Remote Stubs
4681 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4682 that runs in the target system. @value{GDBN} provides several sample
4683 @dfn{stubs} that can be integrated into target programs or operating
4684 systems for this purpose; they are named @file{*-stub.c}.
4686 The @value{GDBN} user's manual describes how to put such a stub into
4687 your target code. What follows is a discussion of integrating the
4688 SPARC stub into a complicated operating system (rather than a simple
4689 program), by Stu Grossman, the author of this stub.
4691 The trap handling code in the stub assumes the following upon entry to
4696 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4702 you are in the correct trap window.
4705 As long as your trap handler can guarantee those conditions, then there
4706 is no reason why you shouldn't be able to ``share'' traps with the stub.
4707 The stub has no requirement that it be jumped to directly from the
4708 hardware trap vector. That is why it calls @code{exceptionHandler()},
4709 which is provided by the external environment. For instance, this could
4710 set up the hardware traps to actually execute code which calls the stub
4711 first, and then transfers to its own trap handler.
4713 For the most point, there probably won't be much of an issue with
4714 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4715 and often indicate unrecoverable error conditions. Anyway, this is all
4716 controlled by a table, and is trivial to modify. The most important
4717 trap for us is for @code{ta 1}. Without that, we can't single step or
4718 do breakpoints. Everything else is unnecessary for the proper operation
4719 of the debugger/stub.
4721 From reading the stub, it's probably not obvious how breakpoints work.
4722 They are simply done by deposit/examine operations from @value{GDBN}.
4724 @subsection ROM Monitor Interface
4726 @subsection Custom Protocols
4728 @subsection Transport Layer
4730 @subsection Builtin Simulator
4733 @node Native Debugging
4735 @chapter Native Debugging
4736 @cindex native debugging
4738 Several files control @value{GDBN}'s configuration for native support:
4742 @item gdb/config/@var{arch}/@var{xyz}.mh
4743 Specifies Makefile fragments needed by a @emph{native} configuration on
4744 machine @var{xyz}. In particular, this lists the required
4745 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4746 Also specifies the header file which describes native support on
4747 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4748 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4749 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4751 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4752 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4753 on machine @var{xyz}. While the file is no longer used for this
4754 purpose, the @file{.mh} suffix remains. Perhaps someone will
4755 eventually rename these fragments so that they have a @file{.mn}
4758 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4759 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4760 macro definitions describing the native system environment, such as
4761 child process control and core file support.
4763 @item gdb/@var{xyz}-nat.c
4764 Contains any miscellaneous C code required for this native support of
4765 this machine. On some machines it doesn't exist at all.
4768 There are some ``generic'' versions of routines that can be used by
4769 various systems. These can be customized in various ways by macros
4770 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4771 the @var{xyz} host, you can just include the generic file's name (with
4772 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4774 Otherwise, if your machine needs custom support routines, you will need
4775 to write routines that perform the same functions as the generic file.
4776 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4777 into @code{NATDEPFILES}.
4781 This contains the @emph{target_ops vector} that supports Unix child
4782 processes on systems which use ptrace and wait to control the child.
4785 This contains the @emph{target_ops vector} that supports Unix child
4786 processes on systems which use /proc to control the child.
4789 This does the low-level grunge that uses Unix system calls to do a ``fork
4790 and exec'' to start up a child process.
4793 This is the low level interface to inferior processes for systems using
4794 the Unix @code{ptrace} call in a vanilla way.
4797 @section Native core file Support
4798 @cindex native core files
4801 @findex fetch_core_registers
4802 @item core-aout.c::fetch_core_registers()
4803 Support for reading registers out of a core file. This routine calls
4804 @code{register_addr()}, see below. Now that BFD is used to read core
4805 files, virtually all machines should use @code{core-aout.c}, and should
4806 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4807 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4809 @item core-aout.c::register_addr()
4810 If your @code{nm-@var{xyz}.h} file defines the macro
4811 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4812 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4813 register number @code{regno}. @code{blockend} is the offset within the
4814 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4815 @file{core-aout.c} will define the @code{register_addr()} function and
4816 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4817 you are using the standard @code{fetch_core_registers()}, you will need
4818 to define your own version of @code{register_addr()}, put it into your
4819 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4820 the @code{NATDEPFILES} list. If you have your own
4821 @code{fetch_core_registers()}, you may not need a separate
4822 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4823 implementations simply locate the registers themselves.@refill
4826 When making @value{GDBN} run native on a new operating system, to make it
4827 possible to debug core files, you will need to either write specific
4828 code for parsing your OS's core files, or customize
4829 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4830 machine uses to define the struct of registers that is accessible
4831 (possibly in the u-area) in a core file (rather than
4832 @file{machine/reg.h}), and an include file that defines whatever header
4833 exists on a core file (e.g., the u-area or a @code{struct core}). Then
4834 modify @code{trad_unix_core_file_p} to use these values to set up the
4835 section information for the data segment, stack segment, any other
4836 segments in the core file (perhaps shared library contents or control
4837 information), ``registers'' segment, and if there are two discontiguous
4838 sets of registers (e.g., integer and float), the ``reg2'' segment. This
4839 section information basically delimits areas in the core file in a
4840 standard way, which the section-reading routines in BFD know how to seek
4843 Then back in @value{GDBN}, you need a matching routine called
4844 @code{fetch_core_registers}. If you can use the generic one, it's in
4845 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4846 It will be passed a char pointer to the entire ``registers'' segment,
4847 its length, and a zero; or a char pointer to the entire ``regs2''
4848 segment, its length, and a 2. The routine should suck out the supplied
4849 register values and install them into @value{GDBN}'s ``registers'' array.
4851 If your system uses @file{/proc} to control processes, and uses ELF
4852 format core files, then you may be able to use the same routines for
4853 reading the registers out of processes and out of core files.
4861 @section shared libraries
4863 @section Native Conditionals
4864 @cindex native conditionals
4866 When @value{GDBN} is configured and compiled, various macros are
4867 defined or left undefined, to control compilation when the host and
4868 target systems are the same. These macros should be defined (or left
4869 undefined) in @file{nm-@var{system}.h}.
4873 @item CHILD_PREPARE_TO_STORE
4874 @findex CHILD_PREPARE_TO_STORE
4875 If the machine stores all registers at once in the child process, then
4876 define this to ensure that all values are correct. This usually entails
4877 a read from the child.
4879 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4882 @item FETCH_INFERIOR_REGISTERS
4883 @findex FETCH_INFERIOR_REGISTERS
4884 Define this if the native-dependent code will provide its own routines
4885 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4886 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4887 @file{infptrace.c} is included in this configuration, the default
4888 routines in @file{infptrace.c} are used for these functions.
4892 This macro is normally defined to be the number of the first floating
4893 point register, if the machine has such registers. As such, it would
4894 appear only in target-specific code. However, @file{/proc} support uses this
4895 to decide whether floats are in use on this target.
4897 @item GET_LONGJMP_TARGET
4898 @findex GET_LONGJMP_TARGET
4899 For most machines, this is a target-dependent parameter. On the
4900 DECstation and the Iris, this is a native-dependent parameter, since
4901 @file{setjmp.h} is needed to define it.
4903 This macro determines the target PC address that @code{longjmp} will jump to,
4904 assuming that we have just stopped at a longjmp breakpoint. It takes a
4905 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4906 pointer. It examines the current state of the machine as needed.
4908 @item I386_USE_GENERIC_WATCHPOINTS
4909 An x86-based machine can define this to use the generic x86 watchpoint
4910 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4913 @findex KERNEL_U_ADDR
4914 Define this to the address of the @code{u} structure (the ``user
4915 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4916 needs to know this so that it can subtract this address from absolute
4917 addresses in the upage, that are obtained via ptrace or from core files.
4918 On systems that don't need this value, set it to zero.
4920 @item KERNEL_U_ADDR_HPUX
4921 @findex KERNEL_U_ADDR_HPUX
4922 Define this to cause @value{GDBN} to determine the address of @code{u} at
4923 runtime, by using HP-style @code{nlist} on the kernel's image in the
4926 @item ONE_PROCESS_WRITETEXT
4927 @findex ONE_PROCESS_WRITETEXT
4928 Define this to be able to, when a breakpoint insertion fails, warn the
4929 user that another process may be running with the same executable.
4932 @findex PROC_NAME_FMT
4933 Defines the format for the name of a @file{/proc} device. Should be
4934 defined in @file{nm.h} @emph{only} in order to override the default
4935 definition in @file{procfs.c}.
4937 @item REGISTER_U_ADDR
4938 @findex REGISTER_U_ADDR
4939 Defines the offset of the registers in the ``u area''.
4941 @item SHELL_COMMAND_CONCAT
4942 @findex SHELL_COMMAND_CONCAT
4943 If defined, is a string to prefix on the shell command used to start the
4948 If defined, this is the name of the shell to use to run the inferior.
4949 Defaults to @code{"/bin/sh"}.
4951 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4953 Define this to expand into an expression that will cause the symbols in
4954 @var{filename} to be added to @value{GDBN}'s symbol table. If
4955 @var{readsyms} is zero symbols are not read but any necessary low level
4956 processing for @var{filename} is still done.
4958 @item SOLIB_CREATE_INFERIOR_HOOK
4959 @findex SOLIB_CREATE_INFERIOR_HOOK
4960 Define this to expand into any shared-library-relocation code that you
4961 want to be run just after the child process has been forked.
4963 @item START_INFERIOR_TRAPS_EXPECTED
4964 @findex START_INFERIOR_TRAPS_EXPECTED
4965 When starting an inferior, @value{GDBN} normally expects to trap
4967 the shell execs, and once when the program itself execs. If the actual
4968 number of traps is something other than 2, then define this macro to
4969 expand into the number expected.
4973 This determines whether small routines in @file{*-tdep.c}, which
4974 translate register values between @value{GDBN}'s internal
4975 representation and the @file{/proc} representation, are compiled.
4978 @findex U_REGS_OFFSET
4979 This is the offset of the registers in the upage. It need only be
4980 defined if the generic ptrace register access routines in
4981 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4982 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4983 the default value from @file{infptrace.c} is good enough, leave it
4986 The default value means that u.u_ar0 @emph{points to} the location of
4987 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4988 that @code{u.u_ar0} @emph{is} the location of the registers.
4992 See @file{objfiles.c}.
4995 @findex DEBUG_PTRACE
4996 Define this to debug @code{ptrace} calls.
5000 @node Support Libraries
5002 @chapter Support Libraries
5007 BFD provides support for @value{GDBN} in several ways:
5010 @item identifying executable and core files
5011 BFD will identify a variety of file types, including a.out, coff, and
5012 several variants thereof, as well as several kinds of core files.
5014 @item access to sections of files
5015 BFD parses the file headers to determine the names, virtual addresses,
5016 sizes, and file locations of all the various named sections in files
5017 (such as the text section or the data section). @value{GDBN} simply
5018 calls BFD to read or write section @var{x} at byte offset @var{y} for
5021 @item specialized core file support
5022 BFD provides routines to determine the failing command name stored in a
5023 core file, the signal with which the program failed, and whether a core
5024 file matches (i.e.@: could be a core dump of) a particular executable
5027 @item locating the symbol information
5028 @value{GDBN} uses an internal interface of BFD to determine where to find the
5029 symbol information in an executable file or symbol-file. @value{GDBN} itself
5030 handles the reading of symbols, since BFD does not ``understand'' debug
5031 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
5036 @cindex opcodes library
5038 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
5039 library because it's also used in binutils, for @file{objdump}).
5042 @cindex readline library
5043 The @code{readline} library provides a set of functions for use by applications
5044 that allow users to edit command lines as they are typed in.
5047 @cindex @code{libiberty} library
5049 The @code{libiberty} library provides a set of functions and features
5050 that integrate and improve on functionality found in modern operating
5051 systems. Broadly speaking, such features can be divided into three
5052 groups: supplemental functions (functions that may be missing in some
5053 environments and operating systems), replacement functions (providing
5054 a uniform and easier to use interface for commonly used standard
5055 functions), and extensions (which provide additional functionality
5056 beyond standard functions).
5058 @value{GDBN} uses various features provided by the @code{libiberty}
5059 library, for instance the C@t{++} demangler, the @acronym{IEEE}
5060 floating format support functions, the input options parser
5061 @samp{getopt}, the @samp{obstack} extension, and other functions.
5063 @subsection @code{obstacks} in @value{GDBN}
5064 @cindex @code{obstacks}
5066 The obstack mechanism provides a convenient way to allocate and free
5067 chunks of memory. Each obstack is a pool of memory that is managed
5068 like a stack. Objects (of any nature, size and alignment) are
5069 allocated and freed in a @acronym{LIFO} fashion on an obstack (see
5070 @code{libiberty}'s documentation for a more detailed explanation of
5073 The most noticeable use of the @code{obstacks} in @value{GDBN} is in
5074 object files. There is an obstack associated with each internal
5075 representation of an object file. Lots of things get allocated on
5076 these @code{obstacks}: dictionary entries, blocks, blockvectors,
5077 symbols, minimal symbols, types, vectors of fundamental types, class
5078 fields of types, object files section lists, object files section
5079 offset lists, line tables, symbol tables, partial symbol tables,
5080 string tables, symbol table private data, macros tables, debug
5081 information sections and entries, import and export lists (som),
5082 unwind information (hppa), dwarf2 location expressions data. Plus
5083 various strings such as directory names strings, debug format strings,
5086 An essential and convenient property of all data on @code{obstacks} is
5087 that memory for it gets allocated (with @code{obstack_alloc}) at
5088 various times during a debugging session, but it is released all at
5089 once using the @code{obstack_free} function. The @code{obstack_free}
5090 function takes a pointer to where in the stack it must start the
5091 deletion from (much like the cleanup chains have a pointer to where to
5092 start the cleanups). Because of the stack like structure of the
5093 @code{obstacks}, this allows to free only a top portion of the
5094 obstack. There are a few instances in @value{GDBN} where such thing
5095 happens. Calls to @code{obstack_free} are done after some local data
5096 is allocated to the obstack. Only the local data is deleted from the
5097 obstack. Of course this assumes that nothing between the
5098 @code{obstack_alloc} and the @code{obstack_free} allocates anything
5099 else on the same obstack. For this reason it is best and safest to
5100 use temporary @code{obstacks}.
5102 Releasing the whole obstack is also not safe per se. It is safe only
5103 under the condition that we know the @code{obstacks} memory is no
5104 longer needed. In @value{GDBN} we get rid of the @code{obstacks} only
5105 when we get rid of the whole objfile(s), for instance upon reading a
5109 @cindex regular expressions library
5120 @item SIGN_EXTEND_CHAR
5122 @item SWITCH_ENUM_BUG
5131 @section Array Containers
5132 @cindex Array Containers
5135 Often it is necessary to manipulate a dynamic array of a set of
5136 objects. C forces some bookkeeping on this, which can get cumbersome
5137 and repetitive. The @file{vec.h} file contains macros for defining
5138 and using a typesafe vector type. The functions defined will be
5139 inlined when compiling, and so the abstraction cost should be zero.
5140 Domain checks are added to detect programming errors.
5142 An example use would be an array of symbols or section information.
5143 The array can be grown as symbols are read in (or preallocated), and
5144 the accessor macros provided keep care of all the necessary
5145 bookkeeping. Because the arrays are type safe, there is no danger of
5146 accidentally mixing up the contents. Think of these as C++ templates,
5147 but implemented in C.
5149 Because of the different behavior of structure objects, scalar objects
5150 and of pointers, there are three flavors of vector, one for each of
5151 these variants. Both the structure object and pointer variants pass
5152 pointers to objects around --- in the former case the pointers are
5153 stored into the vector and in the latter case the pointers are
5154 dereferenced and the objects copied into the vector. The scalar
5155 object variant is suitable for @code{int}-like objects, and the vector
5156 elements are returned by value.
5158 There are both @code{index} and @code{iterate} accessors. The iterator
5159 returns a boolean iteration condition and updates the iteration
5160 variable passed by reference. Because the iterator will be inlined,
5161 the address-of can be optimized away.
5163 The vectors are implemented using the trailing array idiom, thus they
5164 are not resizeable without changing the address of the vector object
5165 itself. This means you cannot have variables or fields of vector type
5166 --- always use a pointer to a vector. The one exception is the final
5167 field of a structure, which could be a vector type. You will have to
5168 use the @code{embedded_size} & @code{embedded_init} calls to create
5169 such objects, and they will probably not be resizeable (so don't use
5170 the @dfn{safe} allocation variants). The trailing array idiom is used
5171 (rather than a pointer to an array of data), because, if we allow
5172 @code{NULL} to also represent an empty vector, empty vectors occupy
5173 minimal space in the structure containing them.
5175 Each operation that increases the number of active elements is
5176 available in @dfn{quick} and @dfn{safe} variants. The former presumes
5177 that there is sufficient allocated space for the operation to succeed
5178 (it dies if there is not). The latter will reallocate the vector, if
5179 needed. Reallocation causes an exponential increase in vector size.
5180 If you know you will be adding N elements, it would be more efficient
5181 to use the reserve operation before adding the elements with the
5182 @dfn{quick} operation. This will ensure there are at least as many
5183 elements as you ask for, it will exponentially increase if there are
5184 too few spare slots. If you want reserve a specific number of slots,
5185 but do not want the exponential increase (for instance, you know this
5186 is the last allocation), use a negative number for reservation. You
5187 can also create a vector of a specific size from the get go.
5189 You should prefer the push and pop operations, as they append and
5190 remove from the end of the vector. If you need to remove several items
5191 in one go, use the truncate operation. The insert and remove
5192 operations allow you to change elements in the middle of the vector.
5193 There are two remove operations, one which preserves the element
5194 ordering @code{ordered_remove}, and one which does not
5195 @code{unordered_remove}. The latter function copies the end element
5196 into the removed slot, rather than invoke a memmove operation. The
5197 @code{lower_bound} function will determine where to place an item in
5198 the array using insert that will maintain sorted order.
5200 If you need to directly manipulate a vector, then the @code{address}
5201 accessor will return the address of the start of the vector. Also the
5202 @code{space} predicate will tell you whether there is spare capacity in the
5203 vector. You will not normally need to use these two functions.
5205 Vector types are defined using a
5206 @code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector
5207 type are declared using a @code{VEC(@var{typename})} macro. The
5208 characters @code{O}, @code{P} and @code{I} indicate whether
5209 @var{typename} is an object (@code{O}), pointer (@code{P}) or integral
5210 (@code{I}) type. Be careful to pick the correct one, as you'll get an
5211 awkward and inefficient API if you use the wrong one. There is a
5212 check, which results in a compile-time warning, for the @code{P} and
5213 @code{I} versions, but there is no check for the @code{O} versions, as
5214 that is not possible in plain C.
5216 An example of their use would be,
5219 DEF_VEC_P(tree); // non-managed tree vector.
5222 VEC(tree) *v; // A (pointer to) a vector of tree pointers.
5225 struct my_struct *s;
5227 if (VEC_length(tree, s->v)) @{ we have some contents @}
5228 VEC_safe_push(tree, s->v, decl); // append some decl onto the end
5229 for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
5230 @{ do something with elt @}
5234 The @file{vec.h} file provides details on how to invoke the various
5235 accessors provided. They are enumerated here:
5239 Return the number of items in the array,
5242 Return true if the array has no elements.
5246 Return the last or arbitrary item in the array.
5249 Access an array element and indicate whether the array has been
5254 Create and destroy an array.
5256 @item VEC_embedded_size
5257 @itemx VEC_embedded_init
5258 Helpers for embedding an array as the final element of another struct.
5264 Return the amount of free space in an array.
5267 Ensure a certain amount of free space.
5269 @item VEC_quick_push
5270 @itemx VEC_safe_push
5271 Append to an array, either assuming the space is available, or making
5275 Remove the last item from an array.
5278 Remove several items from the end of an array.
5281 Add several items to the end of an array.
5284 Overwrite an item in the array.
5286 @item VEC_quick_insert
5287 @itemx VEC_safe_insert
5288 Insert an item into the middle of the array. Either the space must
5289 already exist, or the space is created.
5291 @item VEC_ordered_remove
5292 @itemx VEC_unordered_remove
5293 Remove an item from the array, preserving order or not.
5295 @item VEC_block_remove
5296 Remove a set of items from the array.
5299 Provide the address of the first element.
5301 @item VEC_lower_bound
5302 Binary search the array.
5312 This chapter covers topics that are lower-level than the major
5313 algorithms of @value{GDBN}.
5318 Cleanups are a structured way to deal with things that need to be done
5321 When your code does something (e.g., @code{xmalloc} some memory, or
5322 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
5323 the memory or @code{close} the file), it can make a cleanup. The
5324 cleanup will be done at some future point: when the command is finished
5325 and control returns to the top level; when an error occurs and the stack
5326 is unwound; or when your code decides it's time to explicitly perform
5327 cleanups. Alternatively you can elect to discard the cleanups you
5333 @item struct cleanup *@var{old_chain};
5334 Declare a variable which will hold a cleanup chain handle.
5336 @findex make_cleanup
5337 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
5338 Make a cleanup which will cause @var{function} to be called with
5339 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
5340 handle that can later be passed to @code{do_cleanups} or
5341 @code{discard_cleanups}. Unless you are going to call
5342 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
5343 from @code{make_cleanup}.
5346 @item do_cleanups (@var{old_chain});
5347 Do all cleanups added to the chain since the corresponding
5348 @code{make_cleanup} call was made.
5350 @findex discard_cleanups
5351 @item discard_cleanups (@var{old_chain});
5352 Same as @code{do_cleanups} except that it just removes the cleanups from
5353 the chain and does not call the specified functions.
5356 Cleanups are implemented as a chain. The handle returned by
5357 @code{make_cleanups} includes the cleanup passed to the call and any
5358 later cleanups appended to the chain (but not yet discarded or
5362 make_cleanup (a, 0);
5364 struct cleanup *old = make_cleanup (b, 0);
5372 will call @code{c()} and @code{b()} but will not call @code{a()}. The
5373 cleanup that calls @code{a()} will remain in the cleanup chain, and will
5374 be done later unless otherwise discarded.@refill
5376 Your function should explicitly do or discard the cleanups it creates.
5377 Failing to do this leads to non-deterministic behavior since the caller
5378 will arbitrarily do or discard your functions cleanups. This need leads
5379 to two common cleanup styles.
5381 The first style is try/finally. Before it exits, your code-block calls
5382 @code{do_cleanups} with the old cleanup chain and thus ensures that your
5383 code-block's cleanups are always performed. For instance, the following
5384 code-segment avoids a memory leak problem (even when @code{error} is
5385 called and a forced stack unwind occurs) by ensuring that the
5386 @code{xfree} will always be called:
5389 struct cleanup *old = make_cleanup (null_cleanup, 0);
5390 data = xmalloc (sizeof blah);
5391 make_cleanup (xfree, data);
5396 The second style is try/except. Before it exits, your code-block calls
5397 @code{discard_cleanups} with the old cleanup chain and thus ensures that
5398 any created cleanups are not performed. For instance, the following
5399 code segment, ensures that the file will be closed but only if there is
5403 FILE *file = fopen ("afile", "r");
5404 struct cleanup *old = make_cleanup (close_file, file);
5406 discard_cleanups (old);
5410 Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify
5411 that they ``should not be called when cleanups are not in place''. This
5412 means that any actions you need to reverse in the case of an error or
5413 interruption must be on the cleanup chain before you call these
5414 functions, since they might never return to your code (they
5415 @samp{longjmp} instead).
5417 @section Per-architecture module data
5418 @cindex per-architecture module data
5419 @cindex multi-arch data
5420 @cindex data-pointer, per-architecture/per-module
5422 The multi-arch framework includes a mechanism for adding module
5423 specific per-architecture data-pointers to the @code{struct gdbarch}
5424 architecture object.
5426 A module registers one or more per-architecture data-pointers using:
5428 @deftypefun struct gdbarch_data *gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init})
5429 @var{pre_init} is used to, on-demand, allocate an initial value for a
5430 per-architecture data-pointer using the architecture's obstack (passed
5431 in as a parameter). Since @var{pre_init} can be called during
5432 architecture creation, it is not parameterized with the architecture.
5433 and must not call modules that use per-architecture data.
5436 @deftypefun struct gdbarch_data *gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init})
5437 @var{post_init} is used to obtain an initial value for a
5438 per-architecture data-pointer @emph{after}. Since @var{post_init} is
5439 always called after architecture creation, it both receives the fully
5440 initialized architecture and is free to call modules that use
5441 per-architecture data (care needs to be taken to ensure that those
5442 other modules do not try to call back to this module as that will
5443 create in cycles in the initialization call graph).
5446 These functions return a @code{struct gdbarch_data} that is used to
5447 identify the per-architecture data-pointer added for that module.
5449 The per-architecture data-pointer is accessed using the function:
5451 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
5452 Given the architecture @var{arch} and module data handle
5453 @var{data_handle} (returned by @code{gdbarch_data_register_pre_init}
5454 or @code{gdbarch_data_register_post_init}), this function returns the
5455 current value of the per-architecture data-pointer. If the data
5456 pointer is @code{NULL}, it is first initialized by calling the
5457 corresponding @var{pre_init} or @var{post_init} method.
5460 The examples below assume the following definitions:
5463 struct nozel @{ int total; @};
5464 static struct gdbarch_data *nozel_handle;
5467 A module can extend the architecture vector, adding additional
5468 per-architecture data, using the @var{pre_init} method. The module's
5469 per-architecture data is then initialized during architecture
5472 In the below, the module's per-architecture @emph{nozel} is added. An
5473 architecture can specify its nozel by calling @code{set_gdbarch_nozel}
5474 from @code{gdbarch_init}.
5478 nozel_pre_init (struct obstack *obstack)
5480 struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
5487 set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
5489 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5490 data->total = nozel;
5494 A module can on-demand create architecture dependant data structures
5495 using @code{post_init}.
5497 In the below, the nozel's total is computed on-demand by
5498 @code{nozel_post_init} using information obtained from the
5503 nozel_post_init (struct gdbarch *gdbarch)
5505 struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
5506 nozel->total = gdbarch@dots{} (gdbarch);
5513 nozel_total (struct gdbarch *gdbarch)
5515 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5520 @section Wrapping Output Lines
5521 @cindex line wrap in output
5524 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
5525 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
5526 added in places that would be good breaking points. The utility
5527 routines will take care of actually wrapping if the line width is
5530 The argument to @code{wrap_here} is an indentation string which is
5531 printed @emph{only} if the line breaks there. This argument is saved
5532 away and used later. It must remain valid until the next call to
5533 @code{wrap_here} or until a newline has been printed through the
5534 @code{*_filtered} functions. Don't pass in a local variable and then
5537 It is usually best to call @code{wrap_here} after printing a comma or
5538 space. If you call it before printing a space, make sure that your
5539 indentation properly accounts for the leading space that will print if
5540 the line wraps there.
5542 Any function or set of functions that produce filtered output must
5543 finish by printing a newline, to flush the wrap buffer, before switching
5544 to unfiltered (@code{printf}) output. Symbol reading routines that
5545 print warnings are a good example.
5547 @section @value{GDBN} Coding Standards
5548 @cindex coding standards
5550 @value{GDBN} follows the GNU coding standards, as described in
5551 @file{etc/standards.texi}. This file is also available for anonymous
5552 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
5553 of the standard; in general, when the GNU standard recommends a practice
5554 but does not require it, @value{GDBN} requires it.
5556 @value{GDBN} follows an additional set of coding standards specific to
5557 @value{GDBN}, as described in the following sections.
5562 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
5565 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
5568 @subsection Memory Management
5570 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
5571 @code{calloc}, @code{free} and @code{asprintf}.
5573 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
5574 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
5575 these functions do not return when the memory pool is empty. Instead,
5576 they unwind the stack using cleanups. These functions return
5577 @code{NULL} when requested to allocate a chunk of memory of size zero.
5579 @emph{Pragmatics: By using these functions, the need to check every
5580 memory allocation is removed. These functions provide portable
5583 @value{GDBN} does not use the function @code{free}.
5585 @value{GDBN} uses the function @code{xfree} to return memory to the
5586 memory pool. Consistent with ISO-C, this function ignores a request to
5587 free a @code{NULL} pointer.
5589 @emph{Pragmatics: On some systems @code{free} fails when passed a
5590 @code{NULL} pointer.}
5592 @value{GDBN} can use the non-portable function @code{alloca} for the
5593 allocation of small temporary values (such as strings).
5595 @emph{Pragmatics: This function is very non-portable. Some systems
5596 restrict the memory being allocated to no more than a few kilobytes.}
5598 @value{GDBN} uses the string function @code{xstrdup} and the print
5599 function @code{xstrprintf}.
5601 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
5602 functions such as @code{sprintf} are very prone to buffer overflow
5606 @subsection Compiler Warnings
5607 @cindex compiler warnings
5609 With few exceptions, developers should avoid the configuration option
5610 @samp{--disable-werror} when building @value{GDBN}. The exceptions
5611 are listed in the file @file{gdb/MAINTAINERS}. The default, when
5612 building with @sc{gcc}, is @samp{--enable-werror}.
5614 This option causes @value{GDBN} (when built using GCC) to be compiled
5615 with a carefully selected list of compiler warning flags. Any warnings
5616 from those flags are treated as errors.
5618 The current list of warning flags includes:
5622 Recommended @sc{gcc} warnings.
5624 @item -Wdeclaration-after-statement
5626 @sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
5627 code, but @sc{gcc} 2.x and @sc{c89} do not.
5629 @item -Wpointer-arith
5631 @item -Wformat-nonliteral
5632 Non-literal format strings, with a few exceptions, are bugs - they
5633 might contain unintended user-supplied format specifiers.
5634 Since @value{GDBN} uses the @code{format printf} attribute on all
5635 @code{printf} like functions this checks not just @code{printf} calls
5636 but also calls to functions such as @code{fprintf_unfiltered}.
5638 @item -Wno-pointer-sign
5639 In version 4.0, GCC began warning about pointer argument passing or
5640 assignment even when the source and destination differed only in
5641 signedness. However, most @value{GDBN} code doesn't distinguish
5642 carefully between @code{char} and @code{unsigned char}. In early 2006
5643 the @value{GDBN} developers decided correcting these warnings wasn't
5644 worth the time it would take.
5646 @item -Wno-unused-parameter
5647 Due to the way that @value{GDBN} is implemented many functions have
5648 unused parameters. Consequently this warning is avoided. The macro
5649 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
5650 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
5655 These are warnings which might be useful for @value{GDBN}, but are
5656 currently too noisy to enable with @samp{-Werror}.
5660 @subsection Formatting
5662 @cindex source code formatting
5663 The standard GNU recommendations for formatting must be followed
5666 A function declaration should not have its name in column zero. A
5667 function definition should have its name in column zero.
5671 static void foo (void);
5679 @emph{Pragmatics: This simplifies scripting. Function definitions can
5680 be found using @samp{^function-name}.}
5682 There must be a space between a function or macro name and the opening
5683 parenthesis of its argument list (except for macro definitions, as
5684 required by C). There must not be a space after an open paren/bracket
5685 or before a close paren/bracket.
5687 While additional whitespace is generally helpful for reading, do not use
5688 more than one blank line to separate blocks, and avoid adding whitespace
5689 after the end of a program line (as of 1/99, some 600 lines had
5690 whitespace after the semicolon). Excess whitespace causes difficulties
5691 for @code{diff} and @code{patch} utilities.
5693 Pointers are declared using the traditional K&R C style:
5707 @subsection Comments
5709 @cindex comment formatting
5710 The standard GNU requirements on comments must be followed strictly.
5712 Block comments must appear in the following form, with no @code{/*}- or
5713 @code{*/}-only lines, and no leading @code{*}:
5716 /* Wait for control to return from inferior to debugger. If inferior
5717 gets a signal, we may decide to start it up again instead of
5718 returning. That is why there is a loop in this function. When
5719 this function actually returns it means the inferior should be left
5720 stopped and @value{GDBN} should read more commands. */
5723 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5724 comment works correctly, and @kbd{M-q} fills the block consistently.)
5726 Put a blank line between the block comments preceding function or
5727 variable definitions, and the definition itself.
5729 In general, put function-body comments on lines by themselves, rather
5730 than trying to fit them into the 20 characters left at the end of a
5731 line, since either the comment or the code will inevitably get longer
5732 than will fit, and then somebody will have to move it anyhow.
5736 @cindex C data types
5737 Code must not depend on the sizes of C data types, the format of the
5738 host's floating point numbers, the alignment of anything, or the order
5739 of evaluation of expressions.
5741 @cindex function usage
5742 Use functions freely. There are only a handful of compute-bound areas
5743 in @value{GDBN} that might be affected by the overhead of a function
5744 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5745 limited by the target interface (whether serial line or system call).
5747 However, use functions with moderation. A thousand one-line functions
5748 are just as hard to understand as a single thousand-line function.
5750 @emph{Macros are bad, M'kay.}
5751 (But if you have to use a macro, make sure that the macro arguments are
5752 protected with parentheses.)
5756 Declarations like @samp{struct foo *} should be used in preference to
5757 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5760 @subsection Function Prototypes
5761 @cindex function prototypes
5763 Prototypes must be used when both @emph{declaring} and @emph{defining}
5764 a function. Prototypes for @value{GDBN} functions must include both the
5765 argument type and name, with the name matching that used in the actual
5766 function definition.
5768 All external functions should have a declaration in a header file that
5769 callers include, except for @code{_initialize_*} functions, which must
5770 be external so that @file{init.c} construction works, but shouldn't be
5771 visible to random source files.
5773 Where a source file needs a forward declaration of a static function,
5774 that declaration must appear in a block near the top of the source file.
5777 @subsection Internal Error Recovery
5779 During its execution, @value{GDBN} can encounter two types of errors.
5780 User errors and internal errors. User errors include not only a user
5781 entering an incorrect command but also problems arising from corrupt
5782 object files and system errors when interacting with the target.
5783 Internal errors include situations where @value{GDBN} has detected, at
5784 run time, a corrupt or erroneous situation.
5786 When reporting an internal error, @value{GDBN} uses
5787 @code{internal_error} and @code{gdb_assert}.
5789 @value{GDBN} must not call @code{abort} or @code{assert}.
5791 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5792 the code detected a user error, recovered from it and issued a
5793 @code{warning} or the code failed to correctly recover from the user
5794 error and issued an @code{internal_error}.}
5796 @subsection File Names
5798 Any file used when building the core of @value{GDBN} must be in lower
5799 case. Any file used when building the core of @value{GDBN} must be 8.3
5800 unique. These requirements apply to both source and generated files.
5802 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5803 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5804 is introduced to the build process both @file{Makefile.in} and
5805 @file{configure.in} need to be modified accordingly. Compare the
5806 convoluted conversion process needed to transform @file{COPYING} into
5807 @file{copying.c} with the conversion needed to transform
5808 @file{version.in} into @file{version.c}.}
5810 Any file non 8.3 compliant file (that is not used when building the core
5811 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5813 @emph{Pragmatics: This is clearly a compromise.}
5815 When @value{GDBN} has a local version of a system header file (ex
5816 @file{string.h}) the file name based on the POSIX header prefixed with
5817 @file{gdb_} (@file{gdb_string.h}). These headers should be relatively
5818 independent: they should use only macros defined by @file{configure},
5819 the compiler, or the host; they should include only system headers; they
5820 should refer only to system types. They may be shared between multiple
5821 programs, e.g.@: @value{GDBN} and @sc{gdbserver}.
5823 For other files @samp{-} is used as the separator.
5826 @subsection Include Files
5828 A @file{.c} file should include @file{defs.h} first.
5830 A @file{.c} file should directly include the @code{.h} file of every
5831 declaration and/or definition it directly refers to. It cannot rely on
5834 A @file{.h} file should directly include the @code{.h} file of every
5835 declaration and/or definition it directly refers to. It cannot rely on
5836 indirect inclusion. Exception: The file @file{defs.h} does not need to
5837 be directly included.
5839 An external declaration should only appear in one include file.
5841 An external declaration should never appear in a @code{.c} file.
5842 Exception: a declaration for the @code{_initialize} function that
5843 pacifies @option{-Wmissing-declaration}.
5845 A @code{typedef} definition should only appear in one include file.
5847 An opaque @code{struct} declaration can appear in multiple @file{.h}
5848 files. Where possible, a @file{.h} file should use an opaque
5849 @code{struct} declaration instead of an include.
5851 All @file{.h} files should be wrapped in:
5854 #ifndef INCLUDE_FILE_NAME_H
5855 #define INCLUDE_FILE_NAME_H
5861 @subsection Clean Design and Portable Implementation
5864 In addition to getting the syntax right, there's the little question of
5865 semantics. Some things are done in certain ways in @value{GDBN} because long
5866 experience has shown that the more obvious ways caused various kinds of
5869 @cindex assumptions about targets
5870 You can't assume the byte order of anything that comes from a target
5871 (including @var{value}s, object files, and instructions). Such things
5872 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5873 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5874 such as @code{bfd_get_32}.
5876 You can't assume that you know what interface is being used to talk to
5877 the target system. All references to the target must go through the
5878 current @code{target_ops} vector.
5880 You can't assume that the host and target machines are the same machine
5881 (except in the ``native'' support modules). In particular, you can't
5882 assume that the target machine's header files will be available on the
5883 host machine. Target code must bring along its own header files --
5884 written from scratch or explicitly donated by their owner, to avoid
5888 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5889 to write the code portably than to conditionalize it for various
5892 @cindex system dependencies
5893 New @code{#ifdef}'s which test for specific compilers or manufacturers
5894 or operating systems are unacceptable. All @code{#ifdef}'s should test
5895 for features. The information about which configurations contain which
5896 features should be segregated into the configuration files. Experience
5897 has proven far too often that a feature unique to one particular system
5898 often creeps into other systems; and that a conditional based on some
5899 predefined macro for your current system will become worthless over
5900 time, as new versions of your system come out that behave differently
5901 with regard to this feature.
5903 Adding code that handles specific architectures, operating systems,
5904 target interfaces, or hosts, is not acceptable in generic code.
5906 @cindex portable file name handling
5907 @cindex file names, portability
5908 One particularly notorious area where system dependencies tend to
5909 creep in is handling of file names. The mainline @value{GDBN} code
5910 assumes Posix semantics of file names: absolute file names begin with
5911 a forward slash @file{/}, slashes are used to separate leading
5912 directories, case-sensitive file names. These assumptions are not
5913 necessarily true on non-Posix systems such as MS-Windows. To avoid
5914 system-dependent code where you need to take apart or construct a file
5915 name, use the following portable macros:
5918 @findex HAVE_DOS_BASED_FILE_SYSTEM
5919 @item HAVE_DOS_BASED_FILE_SYSTEM
5920 This preprocessing symbol is defined to a non-zero value on hosts
5921 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5922 symbol to write conditional code which should only be compiled for
5925 @findex IS_DIR_SEPARATOR
5926 @item IS_DIR_SEPARATOR (@var{c})
5927 Evaluates to a non-zero value if @var{c} is a directory separator
5928 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5929 such a character, but on Windows, both @file{/} and @file{\} will
5932 @findex IS_ABSOLUTE_PATH
5933 @item IS_ABSOLUTE_PATH (@var{file})
5934 Evaluates to a non-zero value if @var{file} is an absolute file name.
5935 For Unix and GNU/Linux hosts, a name which begins with a slash
5936 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5937 @file{x:\bar} are also absolute file names.
5939 @findex FILENAME_CMP
5940 @item FILENAME_CMP (@var{f1}, @var{f2})
5941 Calls a function which compares file names @var{f1} and @var{f2} as
5942 appropriate for the underlying host filesystem. For Posix systems,
5943 this simply calls @code{strcmp}; on case-insensitive filesystems it
5944 will call @code{strcasecmp} instead.
5946 @findex DIRNAME_SEPARATOR
5947 @item DIRNAME_SEPARATOR
5948 Evaluates to a character which separates directories in
5949 @code{PATH}-style lists, typically held in environment variables.
5950 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5952 @findex SLASH_STRING
5954 This evaluates to a constant string you should use to produce an
5955 absolute filename from leading directories and the file's basename.
5956 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5957 @code{"\\"} for some Windows-based ports.
5960 In addition to using these macros, be sure to use portable library
5961 functions whenever possible. For example, to extract a directory or a
5962 basename part from a file name, use the @code{dirname} and
5963 @code{basename} library functions (available in @code{libiberty} for
5964 platforms which don't provide them), instead of searching for a slash
5965 with @code{strrchr}.
5967 Another way to generalize @value{GDBN} along a particular interface is with an
5968 attribute struct. For example, @value{GDBN} has been generalized to handle
5969 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5970 by defining the @code{target_ops} structure and having a current target (as
5971 well as a stack of targets below it, for memory references). Whenever
5972 something needs to be done that depends on which remote interface we are
5973 using, a flag in the current target_ops structure is tested (e.g.,
5974 @code{target_has_stack}), or a function is called through a pointer in the
5975 current target_ops structure. In this way, when a new remote interface
5976 is added, only one module needs to be touched---the one that actually
5977 implements the new remote interface. Other examples of
5978 attribute-structs are BFD access to multiple kinds of object file
5979 formats, or @value{GDBN}'s access to multiple source languages.
5981 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5982 the code interfacing between @code{ptrace} and the rest of
5983 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5984 something was very painful. In @value{GDBN} 4.x, these have all been
5985 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5986 with variations between systems the same way any system-independent
5987 file would (hooks, @code{#if defined}, etc.), and machines which are
5988 radically different don't need to use @file{infptrace.c} at all.
5990 All debugging code must be controllable using the @samp{set debug
5991 @var{module}} command. Do not use @code{printf} to print trace
5992 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5993 @code{#ifdef DEBUG}.
5998 @chapter Porting @value{GDBN}
5999 @cindex porting to new machines
6001 Most of the work in making @value{GDBN} compile on a new machine is in
6002 specifying the configuration of the machine. This is done in a
6003 dizzying variety of header files and configuration scripts, which we
6004 hope to make more sensible soon. Let's say your new host is called an
6005 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
6006 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
6007 @samp{sparc-sun-sunos4}). In particular:
6011 In the top level directory, edit @file{config.sub} and add @var{arch},
6012 @var{xvend}, and @var{xos} to the lists of supported architectures,
6013 vendors, and operating systems near the bottom of the file. Also, add
6014 @var{xyz} as an alias that maps to
6015 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
6019 ./config.sub @var{xyz}
6026 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
6030 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
6031 and no error messages.
6034 You need to port BFD, if that hasn't been done already. Porting BFD is
6035 beyond the scope of this manual.
6038 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
6039 your system and set @code{gdb_host} to @var{xyz}, and (unless your
6040 desired target is already available) also edit @file{gdb/configure.tgt},
6041 setting @code{gdb_target} to something appropriate (for instance,
6044 @emph{Maintainer's note: Work in progress. The file
6045 @file{gdb/configure.host} originally needed to be modified when either a
6046 new native target or a new host machine was being added to @value{GDBN}.
6047 Recent changes have removed this requirement. The file now only needs
6048 to be modified when adding a new native configuration. This will likely
6049 changed again in the future.}
6052 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
6053 target-dependent @file{.h} and @file{.c} files used for your
6057 @node Versions and Branches
6058 @chapter Versions and Branches
6062 @value{GDBN}'s version is determined by the file
6063 @file{gdb/version.in} and takes one of the following forms:
6066 @item @var{major}.@var{minor}
6067 @itemx @var{major}.@var{minor}.@var{patchlevel}
6068 an official release (e.g., 6.2 or 6.2.1)
6069 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}
6070 a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g.,
6071 6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308)
6072 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs
6073 a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g.,
6074 6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
6075 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor})
6076 a vendor specific release of @value{GDBN}, that while based on@*
6077 @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD},
6078 may include additional changes
6081 @value{GDBN}'s mainline uses the @var{major} and @var{minor} version
6082 numbers from the most recent release branch, with a @var{patchlevel}
6083 of 50. At the time each new release branch is created, the mainline's
6084 @var{major} and @var{minor} version numbers are updated.
6086 @value{GDBN}'s release branch is similar. When the branch is cut, the
6087 @var{patchlevel} is changed from 50 to 90. As draft releases are
6088 drawn from the branch, the @var{patchlevel} is incremented. Once the
6089 first release (@var{major}.@var{minor}) has been made, the
6090 @var{patchlevel} is set to 0 and updates have an incremented
6093 For snapshots, and @sc{cvs} check outs, it is also possible to
6094 identify the @sc{cvs} origin:
6097 @item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD}
6098 drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302)
6099 @item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD}
6100 @itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{}
6101 drawn from a release branch prior to the release (e.g.,
6103 @item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD}
6104 @itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{}
6105 drawn from a release branch after the release (e.g., 6.2.0.20020308)
6108 If the previous @value{GDBN} version is 6.1 and the current version is
6109 6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor},
6110 here's an illustration of a typical sequence:
6117 +--------------------------.
6120 6.2.50.20020303-cvs 6.1.90 (draft #1)
6122 6.2.50.20020304-cvs 6.1.90.20020304-cvs
6124 6.2.50.20020305-cvs 6.1.91 (draft #2)
6126 6.2.50.20020306-cvs 6.1.91.20020306-cvs
6128 6.2.50.20020307-cvs 6.2 (release)
6130 6.2.50.20020308-cvs 6.2.0.20020308-cvs
6132 6.2.50.20020309-cvs 6.2.1 (update)
6134 6.2.50.20020310-cvs <branch closed>
6138 +--------------------------.
6141 6.3.50.20020312-cvs 6.2.90 (draft #1)
6145 @section Release Branches
6146 @cindex Release Branches
6148 @value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a
6149 single release branch, and identifies that branch using the @sc{cvs}
6153 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint
6154 gdb_@var{major}_@var{minor}-branch
6155 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release
6158 @emph{Pragmatics: To help identify the date at which a branch or
6159 release is made, both the branchpoint and release tags include the
6160 date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The
6161 branch tag, denoting the head of the branch, does not need this.}
6163 @section Vendor Branches
6164 @cindex vendor branches
6166 To avoid version conflicts, vendors are expected to modify the file
6167 @file{gdb/version.in} to include a vendor unique alphabetic identifier
6168 (an official @value{GDBN} release never uses alphabetic characters in
6169 its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit
6172 @section Experimental Branches
6173 @cindex experimental branches
6175 @subsection Guidelines
6177 @value{GDBN} permits the creation of branches, cut from the @sc{cvs}
6178 repository, for experimental development. Branches make it possible
6179 for developers to share preliminary work, and maintainers to examine
6180 significant new developments.
6182 The following are a set of guidelines for creating such branches:
6186 @item a branch has an owner
6187 The owner can set further policy for a branch, but may not change the
6188 ground rules. In particular, they can set a policy for commits (be it
6189 adding more reviewers or deciding who can commit).
6191 @item all commits are posted
6192 All changes committed to a branch shall also be posted to
6193 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} patches
6194 mailing list}. While commentary on such changes are encouraged, people
6195 should remember that the changes only apply to a branch.
6197 @item all commits are covered by an assignment
6198 This ensures that all changes belong to the Free Software Foundation,
6199 and avoids the possibility that the branch may become contaminated.
6201 @item a branch is focused
6202 A focused branch has a single objective or goal, and does not contain
6203 unnecessary or irrelevant changes. Cleanups, where identified, being
6204 be pushed into the mainline as soon as possible.
6206 @item a branch tracks mainline
6207 This keeps the level of divergence under control. It also keeps the
6208 pressure on developers to push cleanups and other stuff into the
6211 @item a branch shall contain the entire @value{GDBN} module
6212 The @value{GDBN} module @code{gdb} should be specified when creating a
6213 branch (branches of individual files should be avoided). @xref{Tags}.
6215 @item a branch shall be branded using @file{version.in}
6216 The file @file{gdb/version.in} shall be modified so that it identifies
6217 the branch @var{owner} and branch @var{name}, e.g.,
6218 @samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}.
6225 To simplify the identification of @value{GDBN} branches, the following
6226 branch tagging convention is strongly recommended:
6230 @item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6231 @itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch
6232 The branch point and corresponding branch tag. @var{YYYYMMDD} is the
6233 date that the branch was created. A branch is created using the
6234 sequence: @anchor{experimental branch tags}
6236 cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb
6237 cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \
6238 @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb
6241 @item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6242 The tagged point, on the mainline, that was used when merging the branch
6243 on @var{yyyymmdd}. To merge in all changes since the branch was cut,
6244 use a command sequence like:
6246 cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb
6248 -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6249 -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6252 Similar sequences can be used to just merge in changes since the last
6258 For further information on @sc{cvs}, see
6259 @uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}.
6261 @node Start of New Year Procedure
6262 @chapter Start of New Year Procedure
6263 @cindex new year procedure
6265 At the start of each new year, the following actions should be performed:
6269 Rotate the ChangeLog file
6271 The current @file{ChangeLog} file should be renamed into
6272 @file{ChangeLog-YYYY} where YYYY is the year that has just passed.
6273 A new @file{ChangeLog} file should be created, and its contents should
6274 contain a reference to the previous ChangeLog. The following should
6275 also be preserved at the end of the new ChangeLog, in order to provide
6276 the appropriate settings when editing this file with Emacs:
6282 version-control: never
6287 Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY})
6288 in @file{gdb/config/djgpp/fnchange.lst}.
6291 Update the copyright year in the startup message
6293 Update the copyright year in file @file{top.c}, function
6294 @code{print_gdb_version}.
6299 @chapter Releasing @value{GDBN}
6300 @cindex making a new release of gdb
6302 @section Branch Commit Policy
6304 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
6305 5.1 and 5.2 all used the below:
6309 The @file{gdb/MAINTAINERS} file still holds.
6311 Don't fix something on the branch unless/until it is also fixed in the
6312 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
6313 file is better than committing a hack.
6315 When considering a patch for the branch, suggested criteria include:
6316 Does it fix a build? Does it fix the sequence @kbd{break main; run}
6317 when debugging a static binary?
6319 The further a change is from the core of @value{GDBN}, the less likely
6320 the change will worry anyone (e.g., target specific code).
6322 Only post a proposal to change the core of @value{GDBN} after you've
6323 sent individual bribes to all the people listed in the
6324 @file{MAINTAINERS} file @t{;-)}
6327 @emph{Pragmatics: Provided updates are restricted to non-core
6328 functionality there is little chance that a broken change will be fatal.
6329 This means that changes such as adding a new architectures or (within
6330 reason) support for a new host are considered acceptable.}
6333 @section Obsoleting code
6335 Before anything else, poke the other developers (and around the source
6336 code) to see if there is anything that can be removed from @value{GDBN}
6337 (an old target, an unused file).
6339 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
6340 line. Doing this means that it is easy to identify something that has
6341 been obsoleted when greping through the sources.
6343 The process is done in stages --- this is mainly to ensure that the
6344 wider @value{GDBN} community has a reasonable opportunity to respond.
6345 Remember, everything on the Internet takes a week.
6349 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
6350 list} Creating a bug report to track the task's state, is also highly
6355 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
6356 Announcement mailing list}.
6360 Go through and edit all relevant files and lines so that they are
6361 prefixed with the word @code{OBSOLETE}.
6363 Wait until the next GDB version, containing this obsolete code, has been
6366 Remove the obsolete code.
6370 @emph{Maintainer note: While removing old code is regrettable it is
6371 hopefully better for @value{GDBN}'s long term development. Firstly it
6372 helps the developers by removing code that is either no longer relevant
6373 or simply wrong. Secondly since it removes any history associated with
6374 the file (effectively clearing the slate) the developer has a much freer
6375 hand when it comes to fixing broken files.}
6379 @section Before the Branch
6381 The most important objective at this stage is to find and fix simple
6382 changes that become a pain to track once the branch is created. For
6383 instance, configuration problems that stop @value{GDBN} from even
6384 building. If you can't get the problem fixed, document it in the
6385 @file{gdb/PROBLEMS} file.
6387 @subheading Prompt for @file{gdb/NEWS}
6389 People always forget. Send a post reminding them but also if you know
6390 something interesting happened add it yourself. The @code{schedule}
6391 script will mention this in its e-mail.
6393 @subheading Review @file{gdb/README}
6395 Grab one of the nightly snapshots and then walk through the
6396 @file{gdb/README} looking for anything that can be improved. The
6397 @code{schedule} script will mention this in its e-mail.
6399 @subheading Refresh any imported files.
6401 A number of files are taken from external repositories. They include:
6405 @file{texinfo/texinfo.tex}
6407 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
6410 @file{etc/standards.texi}, @file{etc/make-stds.texi}
6413 @subheading Check the ARI
6415 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
6416 (Awk Regression Index ;-) that checks for a number of errors and coding
6417 conventions. The checks include things like using @code{malloc} instead
6418 of @code{xmalloc} and file naming problems. There shouldn't be any
6421 @subsection Review the bug data base
6423 Close anything obviously fixed.
6425 @subsection Check all cross targets build
6427 The targets are listed in @file{gdb/MAINTAINERS}.
6430 @section Cut the Branch
6432 @subheading Create the branch
6437 $ V=`echo $v | sed 's/\./_/g'`
6438 $ D=`date -u +%Y-%m-%d`
6441 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6442 -D $D-gmt gdb_$V-$D-branchpoint insight
6443 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
6444 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight
6447 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6448 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
6449 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6450 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
6458 By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact
6461 The trunk is first tagged so that the branch point can easily be found.
6463 Insight, which includes @value{GDBN}, is tagged at the same time.
6465 @file{version.in} gets bumped to avoid version number conflicts.
6467 The reading of @file{.cvsrc} is disabled using @file{-f}.
6470 @subheading Update @file{version.in}
6475 $ V=`echo $v | sed 's/\./_/g'`
6479 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
6480 -r gdb_$V-branch src/gdb/version.in
6481 cvs -f -d :ext:sources.redhat.com:/cvs/src co
6482 -r gdb_5_2-branch src/gdb/version.in
6484 U src/gdb/version.in
6486 $ echo $u.90-0000-00-00-cvs > version.in
6488 5.1.90-0000-00-00-cvs
6489 $ cvs -f commit version.in
6494 @file{0000-00-00} is used as a date to pump prime the version.in update
6497 @file{.90} and the previous branch version are used as fairly arbitrary
6498 initial branch version number.
6502 @subheading Update the web and news pages
6506 @subheading Tweak cron to track the new branch
6508 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
6509 This file needs to be updated so that:
6513 A daily timestamp is added to the file @file{version.in}.
6515 The new branch is included in the snapshot process.
6519 See the file @file{gdbadmin/cron/README} for how to install the updated
6522 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
6523 any changes. That file is copied to both the branch/ and current/
6524 snapshot directories.
6527 @subheading Update the NEWS and README files
6529 The @file{NEWS} file needs to be updated so that on the branch it refers
6530 to @emph{changes in the current release} while on the trunk it also
6531 refers to @emph{changes since the current release}.
6533 The @file{README} file needs to be updated so that it refers to the
6536 @subheading Post the branch info
6538 Send an announcement to the mailing lists:
6542 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6544 @email{gdb@@sources.redhat.com, GDB Discussion mailing list} and
6545 @email{gdb-testers@@sources.redhat.com, GDB Testers mailing list}
6548 @emph{Pragmatics: The branch creation is sent to the announce list to
6549 ensure that people people not subscribed to the higher volume discussion
6552 The announcement should include:
6558 How to check out the branch using CVS.
6560 The date/number of weeks until the release.
6562 The branch commit policy still holds.
6565 @section Stabilize the branch
6567 Something goes here.
6569 @section Create a Release
6571 The process of creating and then making available a release is broken
6572 down into a number of stages. The first part addresses the technical
6573 process of creating a releasable tar ball. The later stages address the
6574 process of releasing that tar ball.
6576 When making a release candidate just the first section is needed.
6578 @subsection Create a release candidate
6580 The objective at this stage is to create a set of tar balls that can be
6581 made available as a formal release (or as a less formal release
6584 @subsubheading Freeze the branch
6586 Send out an e-mail notifying everyone that the branch is frozen to
6587 @email{gdb-patches@@sources.redhat.com}.
6589 @subsubheading Establish a few defaults.
6594 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
6596 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6600 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6602 /home/gdbadmin/bin/autoconf
6611 Check the @code{autoconf} version carefully. You want to be using the
6612 version taken from the @file{binutils} snapshot directory, which can be
6613 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
6614 unlikely that a system installed version of @code{autoconf} (e.g.,
6615 @file{/usr/bin/autoconf}) is correct.
6618 @subsubheading Check out the relevant modules:
6621 $ for m in gdb insight
6623 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
6633 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
6634 any confusion between what is written here and what your local
6635 @code{cvs} really does.
6638 @subsubheading Update relevant files.
6644 Major releases get their comments added as part of the mainline. Minor
6645 releases should probably mention any significant bugs that were fixed.
6647 Don't forget to include the @file{ChangeLog} entry.
6650 $ emacs gdb/src/gdb/NEWS
6655 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
6656 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6661 You'll need to update:
6673 $ emacs gdb/src/gdb/README
6678 $ cp gdb/src/gdb/README insight/src/gdb/README
6679 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6682 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
6683 before the initial branch was cut so just a simple substitute is needed
6686 @emph{Maintainer note: Other projects generate @file{README} and
6687 @file{INSTALL} from the core documentation. This might be worth
6690 @item gdb/version.in
6693 $ echo $v > gdb/src/gdb/version.in
6694 $ cat gdb/src/gdb/version.in
6696 $ emacs gdb/src/gdb/version.in
6699 ... Bump to version ...
6701 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
6702 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6707 @subsubheading Do the dirty work
6709 This is identical to the process used to create the daily snapshot.
6712 $ for m in gdb insight
6714 ( cd $m/src && gmake -f src-release $m.tar )
6718 If the top level source directory does not have @file{src-release}
6719 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
6722 $ for m in gdb insight
6724 ( cd $m/src && gmake -f Makefile.in $m.tar )
6728 @subsubheading Check the source files
6730 You're looking for files that have mysteriously disappeared.
6731 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
6732 for the @file{version.in} update @kbd{cronjob}.
6735 $ ( cd gdb/src && cvs -f -q -n update )
6739 @dots{} lots of generated files @dots{}
6744 @dots{} lots of generated files @dots{}
6749 @emph{Don't worry about the @file{gdb.info-??} or
6750 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
6751 was also generated only something strange with CVS means that they
6752 didn't get suppressed). Fixing it would be nice though.}
6754 @subsubheading Create compressed versions of the release
6760 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
6761 $ for m in gdb insight
6763 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
6764 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
6774 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
6775 in that mode, @code{gzip} does not know the name of the file and, hence,
6776 can not include it in the compressed file. This is also why the release
6777 process runs @code{tar} and @code{bzip2} as separate passes.
6780 @subsection Sanity check the tar ball
6782 Pick a popular machine (Solaris/PPC?) and try the build on that.
6785 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
6790 $ ./gdb/gdb ./gdb/gdb
6794 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6796 Starting program: /tmp/gdb-5.2/gdb/gdb
6798 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6799 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6801 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6805 @subsection Make a release candidate available
6807 If this is a release candidate then the only remaining steps are:
6811 Commit @file{version.in} and @file{ChangeLog}
6813 Tweak @file{version.in} (and @file{ChangeLog} to read
6814 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6815 process can restart.
6817 Make the release candidate available in
6818 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6820 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6821 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6824 @subsection Make a formal release available
6826 (And you thought all that was required was to post an e-mail.)
6828 @subsubheading Install on sware
6830 Copy the new files to both the release and the old release directory:
6833 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6834 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6838 Clean up the releases directory so that only the most recent releases
6839 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6842 $ cd ~ftp/pub/gdb/releases
6847 Update the file @file{README} and @file{.message} in the releases
6854 $ ln README .message
6857 @subsubheading Update the web pages.
6861 @item htdocs/download/ANNOUNCEMENT
6862 This file, which is posted as the official announcement, includes:
6865 General announcement.
6867 News. If making an @var{M}.@var{N}.1 release, retain the news from
6868 earlier @var{M}.@var{N} release.
6873 @item htdocs/index.html
6874 @itemx htdocs/news/index.html
6875 @itemx htdocs/download/index.html
6876 These files include:
6879 Announcement of the most recent release.
6881 News entry (remember to update both the top level and the news directory).
6883 These pages also need to be regenerate using @code{index.sh}.
6885 @item download/onlinedocs/
6886 You need to find the magic command that is used to generate the online
6887 docs from the @file{.tar.bz2}. The best way is to look in the output
6888 from one of the nightly @code{cron} jobs and then just edit accordingly.
6892 $ ~/ss/update-web-docs \
6893 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6895 /www/sourceware/htdocs/gdb/download/onlinedocs \
6900 Just like the online documentation. Something like:
6903 $ /bin/sh ~/ss/update-web-ari \
6904 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6906 /www/sourceware/htdocs/gdb/download/ari \
6912 @subsubheading Shadow the pages onto gnu
6914 Something goes here.
6917 @subsubheading Install the @value{GDBN} tar ball on GNU
6919 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6920 @file{~ftp/gnu/gdb}.
6922 @subsubheading Make the @file{ANNOUNCEMENT}
6924 Post the @file{ANNOUNCEMENT} file you created above to:
6928 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6930 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6931 day or so to let things get out)
6933 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6938 The release is out but you're still not finished.
6940 @subsubheading Commit outstanding changes
6942 In particular you'll need to commit any changes to:
6946 @file{gdb/ChangeLog}
6948 @file{gdb/version.in}
6955 @subsubheading Tag the release
6960 $ d=`date -u +%Y-%m-%d`
6963 $ ( cd insight/src/gdb && cvs -f -q update )
6964 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6967 Insight is used since that contains more of the release than
6970 @subsubheading Mention the release on the trunk
6972 Just put something in the @file{ChangeLog} so that the trunk also
6973 indicates when the release was made.
6975 @subsubheading Restart @file{gdb/version.in}
6977 If @file{gdb/version.in} does not contain an ISO date such as
6978 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6979 committed all the release changes it can be set to
6980 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6981 is important - it affects the snapshot process).
6983 Don't forget the @file{ChangeLog}.
6985 @subsubheading Merge into trunk
6987 The files committed to the branch may also need changes merged into the
6990 @subsubheading Revise the release schedule
6992 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
6993 Discussion List} with an updated announcement. The schedule can be
6994 generated by running:
6997 $ ~/ss/schedule `date +%s` schedule
7001 The first parameter is approximate date/time in seconds (from the epoch)
7002 of the most recent release.
7004 Also update the schedule @code{cronjob}.
7006 @section Post release
7008 Remove any @code{OBSOLETE} code.
7015 The testsuite is an important component of the @value{GDBN} package.
7016 While it is always worthwhile to encourage user testing, in practice
7017 this is rarely sufficient; users typically use only a small subset of
7018 the available commands, and it has proven all too common for a change
7019 to cause a significant regression that went unnoticed for some time.
7021 The @value{GDBN} testsuite uses the DejaGNU testing framework. The
7022 tests themselves are calls to various @code{Tcl} procs; the framework
7023 runs all the procs and summarizes the passes and fails.
7025 @section Using the Testsuite
7027 @cindex running the test suite
7028 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
7029 testsuite's objdir) and type @code{make check}. This just sets up some
7030 environment variables and invokes DejaGNU's @code{runtest} script. While
7031 the testsuite is running, you'll get mentions of which test file is in use,
7032 and a mention of any unexpected passes or fails. When the testsuite is
7033 finished, you'll get a summary that looks like this:
7038 # of expected passes 6016
7039 # of unexpected failures 58
7040 # of unexpected successes 5
7041 # of expected failures 183
7042 # of unresolved testcases 3
7043 # of untested testcases 5
7046 To run a specific test script, type:
7048 make check RUNTESTFLAGS='@var{tests}'
7050 where @var{tests} is a list of test script file names, separated by
7053 The ideal test run consists of expected passes only; however, reality
7054 conspires to keep us from this ideal. Unexpected failures indicate
7055 real problems, whether in @value{GDBN} or in the testsuite. Expected
7056 failures are still failures, but ones which have been decided are too
7057 hard to deal with at the time; for instance, a test case might work
7058 everywhere except on AIX, and there is no prospect of the AIX case
7059 being fixed in the near future. Expected failures should not be added
7060 lightly, since you may be masking serious bugs in @value{GDBN}.
7061 Unexpected successes are expected fails that are passing for some
7062 reason, while unresolved and untested cases often indicate some minor
7063 catastrophe, such as the compiler being unable to deal with a test
7066 When making any significant change to @value{GDBN}, you should run the
7067 testsuite before and after the change, to confirm that there are no
7068 regressions. Note that truly complete testing would require that you
7069 run the testsuite with all supported configurations and a variety of
7070 compilers; however this is more than really necessary. In many cases
7071 testing with a single configuration is sufficient. Other useful
7072 options are to test one big-endian (Sparc) and one little-endian (x86)
7073 host, a cross config with a builtin simulator (powerpc-eabi,
7074 mips-elf), or a 64-bit host (Alpha).
7076 If you add new functionality to @value{GDBN}, please consider adding
7077 tests for it as well; this way future @value{GDBN} hackers can detect
7078 and fix their changes that break the functionality you added.
7079 Similarly, if you fix a bug that was not previously reported as a test
7080 failure, please add a test case for it. Some cases are extremely
7081 difficult to test, such as code that handles host OS failures or bugs
7082 in particular versions of compilers, and it's OK not to try to write
7083 tests for all of those.
7085 DejaGNU supports separate build, host, and target machines. However,
7086 some @value{GDBN} test scripts do not work if the build machine and
7087 the host machine are not the same. In such an environment, these scripts
7088 will give a result of ``UNRESOLVED'', like this:
7091 UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
7094 @section Testsuite Organization
7096 @cindex test suite organization
7097 The testsuite is entirely contained in @file{gdb/testsuite}. While the
7098 testsuite includes some makefiles and configury, these are very minimal,
7099 and used for little besides cleaning up, since the tests themselves
7100 handle the compilation of the programs that @value{GDBN} will run. The file
7101 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
7102 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
7103 configuration-specific files, typically used for special-purpose
7104 definitions of procs like @code{gdb_load} and @code{gdb_start}.
7106 The tests themselves are to be found in @file{testsuite/gdb.*} and
7107 subdirectories of those. The names of the test files must always end
7108 with @file{.exp}. DejaGNU collects the test files by wildcarding
7109 in the test directories, so both subdirectories and individual files
7110 get chosen and run in alphabetical order.
7112 The following table lists the main types of subdirectories and what they
7113 are for. Since DejaGNU finds test files no matter where they are
7114 located, and since each test file sets up its own compilation and
7115 execution environment, this organization is simply for convenience and
7120 This is the base testsuite. The tests in it should apply to all
7121 configurations of @value{GDBN} (but generic native-only tests may live here).
7122 The test programs should be in the subset of C that is valid K&R,
7123 ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance
7126 @item gdb.@var{lang}
7127 Language-specific tests for any language @var{lang} besides C. Examples are
7128 @file{gdb.cp} and @file{gdb.java}.
7130 @item gdb.@var{platform}
7131 Non-portable tests. The tests are specific to a specific configuration
7132 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
7135 @item gdb.@var{compiler}
7136 Tests specific to a particular compiler. As of this writing (June
7137 1999), there aren't currently any groups of tests in this category that
7138 couldn't just as sensibly be made platform-specific, but one could
7139 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
7142 @item gdb.@var{subsystem}
7143 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
7144 instance, @file{gdb.disasm} exercises various disassemblers, while
7145 @file{gdb.stabs} tests pathways through the stabs symbol reader.
7148 @section Writing Tests
7149 @cindex writing tests
7151 In many areas, the @value{GDBN} tests are already quite comprehensive; you
7152 should be able to copy existing tests to handle new cases.
7154 You should try to use @code{gdb_test} whenever possible, since it
7155 includes cases to handle all the unexpected errors that might happen.
7156 However, it doesn't cost anything to add new test procedures; for
7157 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
7158 calls @code{gdb_test} multiple times.
7160 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
7161 necessary, such as when @value{GDBN} has several valid responses to a command.
7163 The source language programs do @emph{not} need to be in a consistent
7164 style. Since @value{GDBN} is used to debug programs written in many different
7165 styles, it's worth having a mix of styles in the testsuite; for
7166 instance, some @value{GDBN} bugs involving the display of source lines would
7167 never manifest themselves if the programs used GNU coding style
7174 Check the @file{README} file, it often has useful information that does not
7175 appear anywhere else in the directory.
7178 * Getting Started:: Getting started working on @value{GDBN}
7179 * Debugging GDB:: Debugging @value{GDBN} with itself
7182 @node Getting Started,,, Hints
7184 @section Getting Started
7186 @value{GDBN} is a large and complicated program, and if you first starting to
7187 work on it, it can be hard to know where to start. Fortunately, if you
7188 know how to go about it, there are ways to figure out what is going on.
7190 This manual, the @value{GDBN} Internals manual, has information which applies
7191 generally to many parts of @value{GDBN}.
7193 Information about particular functions or data structures are located in
7194 comments with those functions or data structures. If you run across a
7195 function or a global variable which does not have a comment correctly
7196 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
7197 free to submit a bug report, with a suggested comment if you can figure
7198 out what the comment should say. If you find a comment which is
7199 actually wrong, be especially sure to report that.
7201 Comments explaining the function of macros defined in host, target, or
7202 native dependent files can be in several places. Sometimes they are
7203 repeated every place the macro is defined. Sometimes they are where the
7204 macro is used. Sometimes there is a header file which supplies a
7205 default definition of the macro, and the comment is there. This manual
7206 also documents all the available macros.
7207 @c (@pxref{Host Conditionals}, @pxref{Target
7208 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
7211 Start with the header files. Once you have some idea of how
7212 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
7213 @file{gdbtypes.h}), you will find it much easier to understand the
7214 code which uses and creates those symbol tables.
7216 You may wish to process the information you are getting somehow, to
7217 enhance your understanding of it. Summarize it, translate it to another
7218 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
7219 the code to predict what a test case would do and write the test case
7220 and verify your prediction, etc. If you are reading code and your eyes
7221 are starting to glaze over, this is a sign you need to use a more active
7224 Once you have a part of @value{GDBN} to start with, you can find more
7225 specifically the part you are looking for by stepping through each
7226 function with the @code{next} command. Do not use @code{step} or you
7227 will quickly get distracted; when the function you are stepping through
7228 calls another function try only to get a big-picture understanding
7229 (perhaps using the comment at the beginning of the function being
7230 called) of what it does. This way you can identify which of the
7231 functions being called by the function you are stepping through is the
7232 one which you are interested in. You may need to examine the data
7233 structures generated at each stage, with reference to the comments in
7234 the header files explaining what the data structures are supposed to
7237 Of course, this same technique can be used if you are just reading the
7238 code, rather than actually stepping through it. The same general
7239 principle applies---when the code you are looking at calls something
7240 else, just try to understand generally what the code being called does,
7241 rather than worrying about all its details.
7243 @cindex command implementation
7244 A good place to start when tracking down some particular area is with
7245 a command which invokes that feature. Suppose you want to know how
7246 single-stepping works. As a @value{GDBN} user, you know that the
7247 @code{step} command invokes single-stepping. The command is invoked
7248 via command tables (see @file{command.h}); by convention the function
7249 which actually performs the command is formed by taking the name of
7250 the command and adding @samp{_command}, or in the case of an
7251 @code{info} subcommand, @samp{_info}. For example, the @code{step}
7252 command invokes the @code{step_command} function and the @code{info
7253 display} command invokes @code{display_info}. When this convention is
7254 not followed, you might have to use @code{grep} or @kbd{M-x
7255 tags-search} in emacs, or run @value{GDBN} on itself and set a
7256 breakpoint in @code{execute_command}.
7258 @cindex @code{bug-gdb} mailing list
7259 If all of the above fail, it may be appropriate to ask for information
7260 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
7261 wondering if anyone could give me some tips about understanding
7262 @value{GDBN}''---if we had some magic secret we would put it in this manual.
7263 Suggestions for improving the manual are always welcome, of course.
7265 @node Debugging GDB,,,Hints
7267 @section Debugging @value{GDBN} with itself
7268 @cindex debugging @value{GDBN}
7270 If @value{GDBN} is limping on your machine, this is the preferred way to get it
7271 fully functional. Be warned that in some ancient Unix systems, like
7272 Ultrix 4.2, a program can't be running in one process while it is being
7273 debugged in another. Rather than typing the command @kbd{@w{./gdb
7274 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
7275 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
7277 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
7278 @file{.gdbinit} file that sets up some simple things to make debugging
7279 gdb easier. The @code{info} command, when executed without a subcommand
7280 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
7281 gdb. See @file{.gdbinit} for details.
7283 If you use emacs, you will probably want to do a @code{make TAGS} after
7284 you configure your distribution; this will put the machine dependent
7285 routines for your local machine where they will be accessed first by
7288 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
7289 have run @code{fixincludes} if you are compiling with gcc.
7291 @section Submitting Patches
7293 @cindex submitting patches
7294 Thanks for thinking of offering your changes back to the community of
7295 @value{GDBN} users. In general we like to get well designed enhancements.
7296 Thanks also for checking in advance about the best way to transfer the
7299 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
7300 This manual summarizes what we believe to be clean design for @value{GDBN}.
7302 If the maintainers don't have time to put the patch in when it arrives,
7303 or if there is any question about a patch, it goes into a large queue
7304 with everyone else's patches and bug reports.
7306 @cindex legal papers for code contributions
7307 The legal issue is that to incorporate substantial changes requires a
7308 copyright assignment from you and/or your employer, granting ownership
7309 of the changes to the Free Software Foundation. You can get the
7310 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
7311 and asking for it. We recommend that people write in "All programs
7312 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
7313 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
7315 contributed with only one piece of legalese pushed through the
7316 bureaucracy and filed with the FSF. We can't start merging changes until
7317 this paperwork is received by the FSF (their rules, which we follow
7318 since we maintain it for them).
7320 Technically, the easiest way to receive changes is to receive each
7321 feature as a small context diff or unidiff, suitable for @code{patch}.
7322 Each message sent to me should include the changes to C code and
7323 header files for a single feature, plus @file{ChangeLog} entries for
7324 each directory where files were modified, and diffs for any changes
7325 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
7326 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
7327 single feature, they can be split down into multiple messages.
7329 In this way, if we read and like the feature, we can add it to the
7330 sources with a single patch command, do some testing, and check it in.
7331 If you leave out the @file{ChangeLog}, we have to write one. If you leave
7332 out the doc, we have to puzzle out what needs documenting. Etc., etc.
7334 The reason to send each change in a separate message is that we will not
7335 install some of the changes. They'll be returned to you with questions
7336 or comments. If we're doing our job correctly, the message back to you
7337 will say what you have to fix in order to make the change acceptable.
7338 The reason to have separate messages for separate features is so that
7339 the acceptable changes can be installed while one or more changes are
7340 being reworked. If multiple features are sent in a single message, we
7341 tend to not put in the effort to sort out the acceptable changes from
7342 the unacceptable, so none of the features get installed until all are
7345 If this sounds painful or authoritarian, well, it is. But we get a lot
7346 of bug reports and a lot of patches, and many of them don't get
7347 installed because we don't have the time to finish the job that the bug
7348 reporter or the contributor could have done. Patches that arrive
7349 complete, working, and well designed, tend to get installed on the day
7350 they arrive. The others go into a queue and get installed as time
7351 permits, which, since the maintainers have many demands to meet, may not
7352 be for quite some time.
7354 Please send patches directly to
7355 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
7357 @section Obsolete Conditionals
7358 @cindex obsolete code
7360 Fragments of old code in @value{GDBN} sometimes reference or set the following
7361 configuration macros. They should not be used by new code, and old uses
7362 should be removed as those parts of the debugger are otherwise touched.
7365 @item STACK_END_ADDR
7366 This macro used to define where the end of the stack appeared, for use
7367 in interpreting core file formats that don't record this address in the
7368 core file itself. This information is now configured in BFD, and @value{GDBN}
7369 gets the info portably from there. The values in @value{GDBN}'s configuration
7370 files should be moved into BFD configuration files (if needed there),
7371 and deleted from all of @value{GDBN}'s config files.
7373 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
7374 is so old that it has never been converted to use BFD. Now that's old!
7378 @include observer.texi