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{dwarf2read.c} reads @sc{DWARF 2}, 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{somread.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 2 debugging info
2149 DWARF 2 is an improved but incompatible version of DWARF 1.
2151 The DWARF 2 reader is in @file{dwarf2read.c}.
2155 @cindex SOM debugging info
2156 Like COFF, the SOM definition includes debugging information.
2158 @section Adding a New Symbol Reader to @value{GDBN}
2160 @cindex adding debugging info reader
2161 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
2162 there is probably little to be done.
2164 If you need to add a new object file format, you must first add it to
2165 BFD. This is beyond the scope of this document.
2167 You must then arrange for the BFD code to provide access to the
2168 debugging symbols. Generally @value{GDBN} will have to call swapping routines
2169 from BFD and a few other BFD internal routines to locate the debugging
2170 information. As much as possible, @value{GDBN} should not depend on the BFD
2171 internal data structures.
2173 For some targets (e.g., COFF), there is a special transfer vector used
2174 to call swapping routines, since the external data structures on various
2175 platforms have different sizes and layouts. Specialized routines that
2176 will only ever be implemented by one object file format may be called
2177 directly. This interface should be described in a file
2178 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
2180 @section Memory Management for Symbol Files
2182 Most memory associated with a loaded symbol file is stored on
2183 its @code{objfile_obstack}. This includes symbols, types,
2184 namespace data, and other information produced by the symbol readers.
2186 Because this data lives on the objfile's obstack, it is automatically
2187 released when the objfile is unloaded or reloaded. Therefore one
2188 objfile must not reference symbol or type data from another objfile;
2189 they could be unloaded at different times.
2191 User convenience variables, et cetera, have associated types. Normally
2192 these types live in the associated objfile. However, when the objfile
2193 is unloaded, those types are deep copied to global memory, so that
2194 the values of the user variables and history items are not lost.
2197 @node Language Support
2199 @chapter Language Support
2201 @cindex language support
2202 @value{GDBN}'s language support is mainly driven by the symbol reader,
2203 although it is possible for the user to set the source language
2206 @value{GDBN} chooses the source language by looking at the extension
2207 of the file recorded in the debug info; @file{.c} means C, @file{.f}
2208 means Fortran, etc. It may also use a special-purpose language
2209 identifier if the debug format supports it, like with DWARF.
2211 @section Adding a Source Language to @value{GDBN}
2213 @cindex adding source language
2214 To add other languages to @value{GDBN}'s expression parser, follow the
2218 @item Create the expression parser.
2220 @cindex expression parser
2221 This should reside in a file @file{@var{lang}-exp.y}. Routines for
2222 building parsed expressions into a @code{union exp_element} list are in
2225 @cindex language parser
2226 Since we can't depend upon everyone having Bison, and YACC produces
2227 parsers that define a bunch of global names, the following lines
2228 @strong{must} be included at the top of the YACC parser, to prevent the
2229 various parsers from defining the same global names:
2232 #define yyparse @var{lang}_parse
2233 #define yylex @var{lang}_lex
2234 #define yyerror @var{lang}_error
2235 #define yylval @var{lang}_lval
2236 #define yychar @var{lang}_char
2237 #define yydebug @var{lang}_debug
2238 #define yypact @var{lang}_pact
2239 #define yyr1 @var{lang}_r1
2240 #define yyr2 @var{lang}_r2
2241 #define yydef @var{lang}_def
2242 #define yychk @var{lang}_chk
2243 #define yypgo @var{lang}_pgo
2244 #define yyact @var{lang}_act
2245 #define yyexca @var{lang}_exca
2246 #define yyerrflag @var{lang}_errflag
2247 #define yynerrs @var{lang}_nerrs
2250 At the bottom of your parser, define a @code{struct language_defn} and
2251 initialize it with the right values for your language. Define an
2252 @code{initialize_@var{lang}} routine and have it call
2253 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
2254 that your language exists. You'll need some other supporting variables
2255 and functions, which will be used via pointers from your
2256 @code{@var{lang}_language_defn}. See the declaration of @code{struct
2257 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
2258 for more information.
2260 @item Add any evaluation routines, if necessary
2262 @cindex expression evaluation routines
2263 @findex evaluate_subexp
2264 @findex prefixify_subexp
2265 @findex length_of_subexp
2266 If you need new opcodes (that represent the operations of the language),
2267 add them to the enumerated type in @file{expression.h}. Add support
2268 code for these operations in the @code{evaluate_subexp} function
2269 defined in the file @file{eval.c}. Add cases
2270 for new opcodes in two functions from @file{parse.c}:
2271 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
2272 the number of @code{exp_element}s that a given operation takes up.
2274 @item Update some existing code
2276 Add an enumerated identifier for your language to the enumerated type
2277 @code{enum language} in @file{defs.h}.
2279 Update the routines in @file{language.c} so your language is included.
2280 These routines include type predicates and such, which (in some cases)
2281 are language dependent. If your language does not appear in the switch
2282 statement, an error is reported.
2284 @vindex current_language
2285 Also included in @file{language.c} is the code that updates the variable
2286 @code{current_language}, and the routines that translate the
2287 @code{language_@var{lang}} enumerated identifier into a printable
2290 @findex _initialize_language
2291 Update the function @code{_initialize_language} to include your
2292 language. This function picks the default language upon startup, so is
2293 dependent upon which languages that @value{GDBN} is built for.
2295 @findex allocate_symtab
2296 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
2297 code so that the language of each symtab (source file) is set properly.
2298 This is used to determine the language to use at each stack frame level.
2299 Currently, the language is set based upon the extension of the source
2300 file. If the language can be better inferred from the symbol
2301 information, please set the language of the symtab in the symbol-reading
2304 @findex print_subexp
2305 @findex op_print_tab
2306 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
2307 expression opcodes you have added to @file{expression.h}. Also, add the
2308 printed representations of your operators to @code{op_print_tab}.
2310 @item Add a place of call
2313 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2314 @code{parse_exp_1} (defined in @file{parse.c}).
2316 @item Use macros to trim code
2318 @cindex trimming language-dependent code
2319 The user has the option of building @value{GDBN} for some or all of the
2320 languages. If the user decides to build @value{GDBN} for the language
2321 @var{lang}, then every file dependent on @file{language.h} will have the
2322 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2323 leave out large routines that the user won't need if he or she is not
2324 using your language.
2326 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2327 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2328 compiled form of your parser) is not linked into @value{GDBN} at all.
2330 See the file @file{configure.in} for how @value{GDBN} is configured
2331 for different languages.
2333 @item Edit @file{Makefile.in}
2335 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2336 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2337 not get linked in, or, worse yet, it may not get @code{tar}red into the
2342 @node Host Definition
2344 @chapter Host Definition
2346 With the advent of Autoconf, it's rarely necessary to have host
2347 definition machinery anymore. The following information is provided,
2348 mainly, as an historical reference.
2350 @section Adding a New Host
2352 @cindex adding a new host
2353 @cindex host, adding
2354 @value{GDBN}'s host configuration support normally happens via Autoconf.
2355 New host-specific definitions should not be needed. Older hosts
2356 @value{GDBN} still use the host-specific definitions and files listed
2357 below, but these mostly exist for historical reasons, and will
2358 eventually disappear.
2361 @item gdb/config/@var{arch}/@var{xyz}.mh
2362 This file once contained both host and native configuration information
2363 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2364 configuration information is now handed by Autoconf.
2366 Host configuration information included a definition of
2367 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2368 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2369 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2371 New host only configurations do not need this file.
2373 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2374 This file once contained definitions and includes required when hosting
2375 gdb on machine @var{xyz}. Those definitions and includes are now
2376 handled by Autoconf.
2378 New host and native configurations do not need this file.
2380 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2381 file to define the macros @var{HOST_FLOAT_FORMAT},
2382 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2383 also needs to be replaced with either an Autoconf or run-time test.}
2387 @subheading Generic Host Support Files
2389 @cindex generic host support
2390 There are some ``generic'' versions of routines that can be used by
2391 various systems. These can be customized in various ways by macros
2392 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2393 the @var{xyz} host, you can just include the generic file's name (with
2394 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2396 Otherwise, if your machine needs custom support routines, you will need
2397 to write routines that perform the same functions as the generic file.
2398 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2399 into @code{XDEPFILES}.
2402 @cindex remote debugging support
2403 @cindex serial line support
2405 This contains serial line support for Unix systems. This is always
2406 included, via the makefile variable @code{SER_HARDWIRE}; override this
2407 variable in the @file{.mh} file to avoid it.
2410 This contains serial line support for 32-bit programs running under DOS,
2411 using the DJGPP (a.k.a.@: GO32) execution environment.
2413 @cindex TCP remote support
2415 This contains generic TCP support using sockets.
2418 @section Host Conditionals
2420 When @value{GDBN} is configured and compiled, various macros are
2421 defined or left undefined, to control compilation based on the
2422 attributes of the host system. These macros and their meanings (or if
2423 the meaning is not documented here, then one of the source files where
2424 they are used is indicated) are:
2427 @item @value{GDBN}INIT_FILENAME
2428 The default name of @value{GDBN}'s initialization file (normally
2432 This macro is deprecated.
2434 @item SIGWINCH_HANDLER
2435 If your host defines @code{SIGWINCH}, you can define this to be the name
2436 of a function to be called if @code{SIGWINCH} is received.
2438 @item SIGWINCH_HANDLER_BODY
2439 Define this to expand into code that will define the function named by
2440 the expansion of @code{SIGWINCH_HANDLER}.
2442 @item ALIGN_STACK_ON_STARTUP
2443 @cindex stack alignment
2444 Define this if your system is of a sort that will crash in
2445 @code{tgetent} if the stack happens not to be longword-aligned when
2446 @code{main} is called. This is a rare situation, but is known to occur
2447 on several different types of systems.
2449 @item CRLF_SOURCE_FILES
2450 @cindex DOS text files
2451 Define this if host files use @code{\r\n} rather than @code{\n} as a
2452 line terminator. This will cause source file listings to omit @code{\r}
2453 characters when printing and it will allow @code{\r\n} line endings of files
2454 which are ``sourced'' by gdb. It must be possible to open files in binary
2455 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2457 @item DEFAULT_PROMPT
2459 The default value of the prompt string (normally @code{"(gdb) "}).
2462 @cindex terminal device
2463 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2466 Define this if binary files are opened the same way as text files.
2470 In some cases, use the system call @code{mmap} for reading symbol
2471 tables. For some machines this allows for sharing and quick updates.
2474 Define this if the host system has @code{termio.h}.
2481 Values for host-side constants.
2484 Substitute for isatty, if not available.
2487 This is the longest integer type available on the host. If not defined,
2488 it will default to @code{long long} or @code{long}, depending on
2489 @code{CC_HAS_LONG_LONG}.
2491 @item CC_HAS_LONG_LONG
2492 @cindex @code{long long} data type
2493 Define this if the host C compiler supports @code{long long}. This is set
2494 by the @code{configure} script.
2496 @item PRINTF_HAS_LONG_LONG
2497 Define this if the host can handle printing of long long integers via
2498 the printf format conversion specifier @code{ll}. This is set by the
2499 @code{configure} script.
2501 @item HAVE_LONG_DOUBLE
2502 Define this if the host C compiler supports @code{long double}. This is
2503 set by the @code{configure} script.
2505 @item PRINTF_HAS_LONG_DOUBLE
2506 Define this if the host can handle printing of long double float-point
2507 numbers via the printf format conversion specifier @code{Lg}. This is
2508 set by the @code{configure} script.
2510 @item SCANF_HAS_LONG_DOUBLE
2511 Define this if the host can handle the parsing of long double
2512 float-point numbers via the scanf format conversion specifier
2513 @code{Lg}. This is set by the @code{configure} script.
2515 @item LSEEK_NOT_LINEAR
2516 Define this if @code{lseek (n)} does not necessarily move to byte number
2517 @code{n} in the file. This is only used when reading source files. It
2518 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2521 This macro is used as the argument to @code{lseek} (or, most commonly,
2522 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2523 which is the POSIX equivalent.
2526 If defined, this should be one or more tokens, such as @code{volatile},
2527 that can be used in both the declaration and definition of functions to
2528 indicate that they never return. The default is already set correctly
2529 if compiling with GCC. This will almost never need to be defined.
2532 If defined, this should be one or more tokens, such as
2533 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2534 of functions to indicate that they never return. The default is already
2535 set correctly if compiling with GCC. This will almost never need to be
2540 Define these to appropriate value for the system @code{lseek}, if not already
2544 This is the signal for stopping @value{GDBN}. Defaults to
2545 @code{SIGTSTP}. (Only redefined for the Convex.)
2548 Means that System V (prior to SVR4) include files are in use. (FIXME:
2549 This symbol is abused in @file{infrun.c}, @file{regex.c}, and
2550 @file{utils.c} for other things, at the moment.)
2553 Define this to help placate @code{lint} in some situations.
2556 Define this to override the defaults of @code{__volatile__} or
2561 @node Target Architecture Definition
2563 @chapter Target Architecture Definition
2565 @cindex target architecture definition
2566 @value{GDBN}'s target architecture defines what sort of
2567 machine-language programs @value{GDBN} can work with, and how it works
2570 The target architecture object is implemented as the C structure
2571 @code{struct gdbarch *}. The structure, and its methods, are generated
2572 using the Bourne shell script @file{gdbarch.sh}.
2574 @section Operating System ABI Variant Handling
2575 @cindex OS ABI variants
2577 @value{GDBN} provides a mechanism for handling variations in OS
2578 ABIs. An OS ABI variant may have influence over any number of
2579 variables in the target architecture definition. There are two major
2580 components in the OS ABI mechanism: sniffers and handlers.
2582 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2583 (the architecture may be wildcarded) in an attempt to determine the
2584 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2585 to be @dfn{generic}, while sniffers for a specific architecture are
2586 considered to be @dfn{specific}. A match from a specific sniffer
2587 overrides a match from a generic sniffer. Multiple sniffers for an
2588 architecture/flavour may exist, in order to differentiate between two
2589 different operating systems which use the same basic file format. The
2590 OS ABI framework provides a generic sniffer for ELF-format files which
2591 examines the @code{EI_OSABI} field of the ELF header, as well as note
2592 sections known to be used by several operating systems.
2594 @cindex fine-tuning @code{gdbarch} structure
2595 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2596 selected OS ABI. There may be only one handler for a given OS ABI
2597 for each BFD architecture.
2599 The following OS ABI variants are defined in @file{defs.h}:
2603 @findex GDB_OSABI_UNINITIALIZED
2604 @item GDB_OSABI_UNINITIALIZED
2605 Used for struct gdbarch_info if ABI is still uninitialized.
2607 @findex GDB_OSABI_UNKNOWN
2608 @item GDB_OSABI_UNKNOWN
2609 The ABI of the inferior is unknown. The default @code{gdbarch}
2610 settings for the architecture will be used.
2612 @findex GDB_OSABI_SVR4
2613 @item GDB_OSABI_SVR4
2614 UNIX System V Release 4.
2616 @findex GDB_OSABI_HURD
2617 @item GDB_OSABI_HURD
2618 GNU using the Hurd kernel.
2620 @findex GDB_OSABI_SOLARIS
2621 @item GDB_OSABI_SOLARIS
2624 @findex GDB_OSABI_OSF1
2625 @item GDB_OSABI_OSF1
2626 OSF/1, including Digital UNIX and Compaq Tru64 UNIX.
2628 @findex GDB_OSABI_LINUX
2629 @item GDB_OSABI_LINUX
2630 GNU using the Linux kernel.
2632 @findex GDB_OSABI_FREEBSD_AOUT
2633 @item GDB_OSABI_FREEBSD_AOUT
2634 FreeBSD using the @code{a.out} executable format.
2636 @findex GDB_OSABI_FREEBSD_ELF
2637 @item GDB_OSABI_FREEBSD_ELF
2638 FreeBSD using the ELF executable format.
2640 @findex GDB_OSABI_NETBSD_AOUT
2641 @item GDB_OSABI_NETBSD_AOUT
2642 NetBSD using the @code{a.out} executable format.
2644 @findex GDB_OSABI_NETBSD_ELF
2645 @item GDB_OSABI_NETBSD_ELF
2646 NetBSD using the ELF executable format.
2648 @findex GDB_OSABI_OPENBSD_ELF
2649 @item GDB_OSABI_OPENBSD_ELF
2650 OpenBSD using the ELF executable format.
2652 @findex GDB_OSABI_WINCE
2653 @item GDB_OSABI_WINCE
2656 @findex GDB_OSABI_GO32
2657 @item GDB_OSABI_GO32
2660 @findex GDB_OSABI_IRIX
2661 @item GDB_OSABI_IRIX
2664 @findex GDB_OSABI_INTERIX
2665 @item GDB_OSABI_INTERIX
2666 Interix (Posix layer for MS-Windows systems).
2668 @findex GDB_OSABI_HPUX_ELF
2669 @item GDB_OSABI_HPUX_ELF
2670 HP/UX using the ELF executable format.
2672 @findex GDB_OSABI_HPUX_SOM
2673 @item GDB_OSABI_HPUX_SOM
2674 HP/UX using the SOM executable format.
2676 @findex GDB_OSABI_QNXNTO
2677 @item GDB_OSABI_QNXNTO
2680 @findex GDB_OSABI_CYGWIN
2681 @item GDB_OSABI_CYGWIN
2684 @findex GDB_OSABI_AIX
2690 Here are the functions that make up the OS ABI framework:
2692 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2693 Return the name of the OS ABI corresponding to @var{osabi}.
2696 @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}))
2697 Register the OS ABI handler specified by @var{init_osabi} for the
2698 architecture, machine type and OS ABI specified by @var{arch},
2699 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2700 machine type, which implies the architecture's default machine type,
2704 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2705 Register the OS ABI file sniffer specified by @var{sniffer} for the
2706 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2707 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2708 be generic, and is allowed to examine @var{flavour}-flavoured files for
2712 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2713 Examine the file described by @var{abfd} to determine its OS ABI.
2714 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2718 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2719 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2720 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2721 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2722 architecture, a warning will be issued and the debugging session will continue
2723 with the defaults already established for @var{gdbarch}.
2726 @deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj})
2727 Helper routine for ELF file sniffers. Examine the file described by
2728 @var{abfd} and look at ABI tag note sections to determine the OS ABI
2729 from the note. This function should be called via
2730 @code{bfd_map_over_sections}.
2733 @section Initializing a New Architecture
2735 Each @code{gdbarch} is associated with a single @sc{bfd} architecture,
2736 via a @code{bfd_arch_@var{arch}} constant. The @code{gdbarch} is
2737 registered by a call to @code{register_gdbarch_init}, usually from
2738 the file's @code{_initialize_@var{filename}} routine, which will
2739 be automatically called during @value{GDBN} startup. The arguments
2740 are a @sc{bfd} architecture constant and an initialization function.
2742 The initialization function has this type:
2745 static struct gdbarch *
2746 @var{arch}_gdbarch_init (struct gdbarch_info @var{info},
2747 struct gdbarch_list *@var{arches})
2750 The @var{info} argument contains parameters used to select the correct
2751 architecture, and @var{arches} is a list of architectures which
2752 have already been created with the same @code{bfd_arch_@var{arch}}
2755 The initialization function should first make sure that @var{info}
2756 is acceptable, and return @code{NULL} if it is not. Then, it should
2757 search through @var{arches} for an exact match to @var{info}, and
2758 return one if found. Lastly, if no exact match was found, it should
2759 create a new architecture based on @var{info} and return it.
2761 Only information in @var{info} should be used to choose the new
2762 architecture. Historically, @var{info} could be sparse, and
2763 defaults would be collected from the first element on @var{arches}.
2764 However, @value{GDBN} now fills in @var{info} more thoroughly,
2765 so new @code{gdbarch} initialization functions should not take
2766 defaults from @var{arches}.
2768 @section Registers and Memory
2770 @value{GDBN}'s model of the target machine is rather simple.
2771 @value{GDBN} assumes the machine includes a bank of registers and a
2772 block of memory. Each register may have a different size.
2774 @value{GDBN} does not have a magical way to match up with the
2775 compiler's idea of which registers are which; however, it is critical
2776 that they do match up accurately. The only way to make this work is
2777 to get accurate information about the order that the compiler uses,
2778 and to reflect that in the @code{REGISTER_NAME} and related macros.
2780 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2782 @section Pointers Are Not Always Addresses
2783 @cindex pointer representation
2784 @cindex address representation
2785 @cindex word-addressed machines
2786 @cindex separate data and code address spaces
2787 @cindex spaces, separate data and code address
2788 @cindex address spaces, separate data and code
2789 @cindex code pointers, word-addressed
2790 @cindex converting between pointers and addresses
2791 @cindex D10V addresses
2793 On almost all 32-bit architectures, the representation of a pointer is
2794 indistinguishable from the representation of some fixed-length number
2795 whose value is the byte address of the object pointed to. On such
2796 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2797 However, architectures with smaller word sizes are often cramped for
2798 address space, so they may choose a pointer representation that breaks this
2799 identity, and allows a larger code address space.
2801 For example, the Renesas D10V is a 16-bit VLIW processor whose
2802 instructions are 32 bits long@footnote{Some D10V instructions are
2803 actually pairs of 16-bit sub-instructions. However, since you can't
2804 jump into the middle of such a pair, code addresses can only refer to
2805 full 32 bit instructions, which is what matters in this explanation.}.
2806 If the D10V used ordinary byte addresses to refer to code locations,
2807 then the processor would only be able to address 64kb of instructions.
2808 However, since instructions must be aligned on four-byte boundaries, the
2809 low two bits of any valid instruction's byte address are always
2810 zero---byte addresses waste two bits. So instead of byte addresses,
2811 the D10V uses word addresses---byte addresses shifted right two bits---to
2812 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2815 However, this means that code pointers and data pointers have different
2816 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2817 @code{0xC020} when used as a data address, but refers to byte address
2818 @code{0x30080} when used as a code address.
2820 (The D10V also uses separate code and data address spaces, which also
2821 affects the correspondence between pointers and addresses, but we're
2822 going to ignore that here; this example is already too long.)
2824 To cope with architectures like this---the D10V is not the only
2825 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2826 byte numbers, and @dfn{pointers}, which are the target's representation
2827 of an address of a particular type of data. In the example above,
2828 @code{0xC020} is the pointer, which refers to one of the addresses
2829 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2830 @value{GDBN} provides functions for turning a pointer into an address
2831 and vice versa, in the appropriate way for the current architecture.
2833 Unfortunately, since addresses and pointers are identical on almost all
2834 processors, this distinction tends to bit-rot pretty quickly. Thus,
2835 each time you port @value{GDBN} to an architecture which does
2836 distinguish between pointers and addresses, you'll probably need to
2837 clean up some architecture-independent code.
2839 Here are functions which convert between pointers and addresses:
2841 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2842 Treat the bytes at @var{buf} as a pointer or reference of type
2843 @var{type}, and return the address it represents, in a manner
2844 appropriate for the current architecture. This yields an address
2845 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2846 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2849 For example, if the current architecture is the Intel x86, this function
2850 extracts a little-endian integer of the appropriate length from
2851 @var{buf} and returns it. However, if the current architecture is the
2852 D10V, this function will return a 16-bit integer extracted from
2853 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2855 If @var{type} is not a pointer or reference type, then this function
2856 will signal an internal error.
2859 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2860 Store the address @var{addr} in @var{buf}, in the proper format for a
2861 pointer of type @var{type} in the current architecture. Note that
2862 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2865 For example, if the current architecture is the Intel x86, this function
2866 stores @var{addr} unmodified as a little-endian integer of the
2867 appropriate length in @var{buf}. However, if the current architecture
2868 is the D10V, this function divides @var{addr} by four if @var{type} is
2869 a pointer to a function, and then stores it in @var{buf}.
2871 If @var{type} is not a pointer or reference type, then this function
2872 will signal an internal error.
2875 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2876 Assuming that @var{val} is a pointer, return the address it represents,
2877 as appropriate for the current architecture.
2879 This function actually works on integral values, as well as pointers.
2880 For pointers, it performs architecture-specific conversions as
2881 described above for @code{extract_typed_address}.
2884 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2885 Create and return a value representing a pointer of type @var{type} to
2886 the address @var{addr}, as appropriate for the current architecture.
2887 This function performs architecture-specific conversions as described
2888 above for @code{store_typed_address}.
2891 Here are some macros which architectures can define to indicate the
2892 relationship between pointers and addresses. These have default
2893 definitions, appropriate for architectures on which all pointers are
2894 simple unsigned byte addresses.
2896 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2897 Assume that @var{buf} holds a pointer of type @var{type}, in the
2898 appropriate format for the current architecture. Return the byte
2899 address the pointer refers to.
2901 This function may safely assume that @var{type} is either a pointer or a
2902 C@t{++} reference type.
2905 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2906 Store in @var{buf} a pointer of type @var{type} representing the address
2907 @var{addr}, in the appropriate format for the current architecture.
2909 This function may safely assume that @var{type} is either a pointer or a
2910 C@t{++} reference type.
2913 @section Address Classes
2914 @cindex address classes
2915 @cindex DW_AT_byte_size
2916 @cindex DW_AT_address_class
2918 Sometimes information about different kinds of addresses is available
2919 via the debug information. For example, some programming environments
2920 define addresses of several different sizes. If the debug information
2921 distinguishes these kinds of address classes through either the size
2922 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2923 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2924 following macros should be defined in order to disambiguate these
2925 types within @value{GDBN} as well as provide the added information to
2926 a @value{GDBN} user when printing type expressions.
2928 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2929 Returns the type flags needed to construct a pointer type whose size
2930 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2931 This function is normally called from within a symbol reader. See
2932 @file{dwarf2read.c}.
2935 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2936 Given the type flags representing an address class qualifier, return
2939 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2940 Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags
2941 for that address class qualifier.
2944 Since the need for address classes is rather rare, none of
2945 the address class macros defined by default. Predicate
2946 macros are provided to detect when they are defined.
2948 Consider a hypothetical architecture in which addresses are normally
2949 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2950 suppose that the @w{DWARF 2} information for this architecture simply
2951 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2952 of these "short" pointers. The following functions could be defined
2953 to implement the address class macros:
2956 somearch_address_class_type_flags (int byte_size,
2957 int dwarf2_addr_class)
2960 return TYPE_FLAG_ADDRESS_CLASS_1;
2966 somearch_address_class_type_flags_to_name (int type_flags)
2968 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
2975 somearch_address_class_name_to_type_flags (char *name,
2976 int *type_flags_ptr)
2978 if (strcmp (name, "short") == 0)
2980 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
2988 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
2989 to indicate the presence of one of these "short" pointers. E.g, if
2990 the debug information indicates that @code{short_ptr_var} is one of these
2991 short pointers, @value{GDBN} might show the following behavior:
2994 (gdb) ptype short_ptr_var
2995 type = int * @@short
2999 @section Raw and Virtual Register Representations
3000 @cindex raw register representation
3001 @cindex virtual register representation
3002 @cindex representations, raw and virtual registers
3004 @emph{Maintainer note: This section is pretty much obsolete. The
3005 functionality described here has largely been replaced by
3006 pseudo-registers and the mechanisms described in @ref{Target
3007 Architecture Definition, , Using Different Register and Memory Data
3008 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
3009 Bug Tracking Database} and
3010 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
3011 up-to-date information.}
3013 Some architectures use one representation for a value when it lives in a
3014 register, but use a different representation when it lives in memory.
3015 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
3016 the target registers, and the @dfn{virtual} representation is the one
3017 used in memory, and within @value{GDBN} @code{struct value} objects.
3019 @emph{Maintainer note: Notice that the same mechanism is being used to
3020 both convert a register to a @code{struct value} and alternative
3023 For almost all data types on almost all architectures, the virtual and
3024 raw representations are identical, and no special handling is needed.
3025 However, they do occasionally differ. For example:
3029 The x86 architecture supports an 80-bit @code{long double} type. However, when
3030 we store those values in memory, they occupy twelve bytes: the
3031 floating-point number occupies the first ten, and the final two bytes
3032 are unused. This keeps the values aligned on four-byte boundaries,
3033 allowing more efficient access. Thus, the x86 80-bit floating-point
3034 type is the raw representation, and the twelve-byte loosely-packed
3035 arrangement is the virtual representation.
3038 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
3039 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
3040 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
3041 raw representation, and the trimmed 32-bit representation is the
3042 virtual representation.
3045 In general, the raw representation is determined by the architecture, or
3046 @value{GDBN}'s interface to the architecture, while the virtual representation
3047 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
3048 @code{registers}, holds the register contents in raw format, and the
3049 @value{GDBN} remote protocol transmits register values in raw format.
3051 Your architecture may define the following macros to request
3052 conversions between the raw and virtual format:
3054 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
3055 Return non-zero if register number @var{reg}'s value needs different raw
3056 and virtual formats.
3058 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
3059 unless this macro returns a non-zero value for that register.
3062 @deftypefn {Target Macro} int DEPRECATED_REGISTER_RAW_SIZE (int @var{reg})
3063 The size of register number @var{reg}'s raw value. This is the number
3064 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
3065 remote protocol packet.
3068 @deftypefn {Target Macro} int DEPRECATED_REGISTER_VIRTUAL_SIZE (int @var{reg})
3069 The size of register number @var{reg}'s value, in its virtual format.
3070 This is the size a @code{struct value}'s buffer will have, holding that
3074 @deftypefn {Target Macro} struct type *DEPRECATED_REGISTER_VIRTUAL_TYPE (int @var{reg})
3075 This is the type of the virtual representation of register number
3076 @var{reg}. Note that there is no need for a macro giving a type for the
3077 register's raw form; once the register's value has been obtained, @value{GDBN}
3078 always uses the virtual form.
3081 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3082 Convert the value of register number @var{reg} to @var{type}, which
3083 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3084 at @var{from} holds the register's value in raw format; the macro should
3085 convert the value to virtual format, and place it at @var{to}.
3087 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
3088 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
3089 arguments in different orders.
3091 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
3092 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
3096 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3097 Convert the value of register number @var{reg} to @var{type}, which
3098 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3099 at @var{from} holds the register's value in raw format; the macro should
3100 convert the value to virtual format, and place it at @var{to}.
3102 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
3103 their @var{reg} and @var{type} arguments in different orders.
3107 @section Using Different Register and Memory Data Representations
3108 @cindex register representation
3109 @cindex memory representation
3110 @cindex representations, register and memory
3111 @cindex register data formats, converting
3112 @cindex @code{struct value}, converting register contents to
3114 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
3115 significant change. Many of the macros and functions referred to in this
3116 section are likely to be subject to further revision. See
3117 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
3118 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
3119 further information. cagney/2002-05-06.}
3121 Some architectures can represent a data object in a register using a
3122 form that is different to the objects more normal memory representation.
3128 The Alpha architecture can represent 32 bit integer values in
3129 floating-point registers.
3132 The x86 architecture supports 80-bit floating-point registers. The
3133 @code{long double} data type occupies 96 bits in memory but only 80 bits
3134 when stored in a register.
3138 In general, the register representation of a data type is determined by
3139 the architecture, or @value{GDBN}'s interface to the architecture, while
3140 the memory representation is determined by the Application Binary
3143 For almost all data types on almost all architectures, the two
3144 representations are identical, and no special handling is needed.
3145 However, they do occasionally differ. Your architecture may define the
3146 following macros to request conversions between the register and memory
3147 representations of a data type:
3149 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
3150 Return non-zero if the representation of a data value stored in this
3151 register may be different to the representation of that same data value
3152 when stored in memory.
3154 When non-zero, the macros @code{REGISTER_TO_VALUE} and
3155 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
3158 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3159 Convert the value of register number @var{reg} to a data object of type
3160 @var{type}. The buffer at @var{from} holds the register's value in raw
3161 format; the converted value should be placed in the buffer at @var{to}.
3163 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3164 their @var{reg} and @var{type} arguments in different orders.
3166 You should only use @code{REGISTER_TO_VALUE} with registers for which
3167 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3170 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3171 Convert a data value of type @var{type} to register number @var{reg}'
3174 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3175 their @var{reg} and @var{type} arguments in different orders.
3177 You should only use @code{VALUE_TO_REGISTER} with registers for which
3178 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3181 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
3182 See @file{mips-tdep.c}. It does not do what you want.
3186 @section Frame Interpretation
3188 @section Inferior Call Setup
3190 @section Compiler Characteristics
3192 @section Target Conditionals
3194 This section describes the macros that you can use to define the target
3199 @item ADDR_BITS_REMOVE (addr)
3200 @findex ADDR_BITS_REMOVE
3201 If a raw machine instruction address includes any bits that are not
3202 really part of the address, then define this macro to expand into an
3203 expression that zeroes those bits in @var{addr}. This is only used for
3204 addresses of instructions, and even then not in all contexts.
3206 For example, the two low-order bits of the PC on the Hewlett-Packard PA
3207 2.0 architecture contain the privilege level of the corresponding
3208 instruction. Since instructions must always be aligned on four-byte
3209 boundaries, the processor masks out these bits to generate the actual
3210 address of the instruction. ADDR_BITS_REMOVE should filter out these
3211 bits with an expression such as @code{((addr) & ~3)}.
3213 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
3214 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
3215 If @var{name} is a valid address class qualifier name, set the @code{int}
3216 referenced by @var{type_flags_ptr} to the mask representing the qualifier
3217 and return 1. If @var{name} is not a valid address class qualifier name,
3220 The value for @var{type_flags_ptr} should be one of
3221 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
3222 possibly some combination of these values or'd together.
3223 @xref{Target Architecture Definition, , Address Classes}.
3225 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
3226 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
3227 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
3230 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3231 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3232 Given a pointers byte size (as described by the debug information) and
3233 the possible @code{DW_AT_address_class} value, return the type flags
3234 used by @value{GDBN} to represent this address class. The value
3235 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
3236 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
3237 values or'd together.
3238 @xref{Target Architecture Definition, , Address Classes}.
3240 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
3241 @findex ADDRESS_CLASS_TYPE_FLAGS_P
3242 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
3245 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
3246 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
3247 Return the name of the address class qualifier associated with the type
3248 flags given by @var{type_flags}.
3250 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
3251 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
3252 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
3254 @xref{Target Architecture Definition, , Address Classes}.
3256 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
3257 @findex ADDRESS_TO_POINTER
3258 Store in @var{buf} a pointer of type @var{type} representing the address
3259 @var{addr}, in the appropriate format for the current architecture.
3260 This macro may safely assume that @var{type} is either a pointer or a
3261 C@t{++} reference type.
3262 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3264 @item BELIEVE_PCC_PROMOTION
3265 @findex BELIEVE_PCC_PROMOTION
3266 Define if the compiler promotes a @code{short} or @code{char}
3267 parameter to an @code{int}, but still reports the parameter as its
3268 original type, rather than the promoted type.
3270 @item BITS_BIG_ENDIAN
3271 @findex BITS_BIG_ENDIAN
3272 Define this if the numbering of bits in the targets does @strong{not} match the
3273 endianness of the target byte order. A value of 1 means that the bits
3274 are numbered in a big-endian bit order, 0 means little-endian.
3278 This is the character array initializer for the bit pattern to put into
3279 memory where a breakpoint is set. Although it's common to use a trap
3280 instruction for a breakpoint, it's not required; for instance, the bit
3281 pattern could be an invalid instruction. The breakpoint must be no
3282 longer than the shortest instruction of the architecture.
3284 @code{BREAKPOINT} has been deprecated in favor of
3285 @code{BREAKPOINT_FROM_PC}.
3287 @item BIG_BREAKPOINT
3288 @itemx LITTLE_BREAKPOINT
3289 @findex LITTLE_BREAKPOINT
3290 @findex BIG_BREAKPOINT
3291 Similar to BREAKPOINT, but used for bi-endian targets.
3293 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3294 favor of @code{BREAKPOINT_FROM_PC}.
3296 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3297 @findex BREAKPOINT_FROM_PC
3298 @anchor{BREAKPOINT_FROM_PC} Use the program counter to determine the
3299 contents and size of a breakpoint instruction. It returns a pointer to
3300 a string of bytes that encode a breakpoint instruction, stores the
3301 length of the string to @code{*@var{lenptr}}, and adjusts the program
3302 counter (if necessary) to point to the actual memory location where the
3303 breakpoint should be inserted.
3305 Although it is common to use a trap instruction for a breakpoint, it's
3306 not required; for instance, the bit pattern could be an invalid
3307 instruction. The breakpoint must be no longer than the shortest
3308 instruction of the architecture.
3310 Replaces all the other @var{BREAKPOINT} macros.
3312 @item MEMORY_INSERT_BREAKPOINT (@var{bp_tgt})
3313 @itemx MEMORY_REMOVE_BREAKPOINT (@var{bp_tgt})
3314 @findex MEMORY_REMOVE_BREAKPOINT
3315 @findex MEMORY_INSERT_BREAKPOINT
3316 Insert or remove memory based breakpoints. Reasonable defaults
3317 (@code{default_memory_insert_breakpoint} and
3318 @code{default_memory_remove_breakpoint} respectively) have been
3319 provided so that it is not necessary to define these for most
3320 architectures. Architectures which may want to define
3321 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3322 likely have instructions that are oddly sized or are not stored in a
3323 conventional manner.
3325 It may also be desirable (from an efficiency standpoint) to define
3326 custom breakpoint insertion and removal routines if
3327 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3330 @item ADJUST_BREAKPOINT_ADDRESS (@var{address})
3331 @findex ADJUST_BREAKPOINT_ADDRESS
3332 @cindex breakpoint address adjusted
3333 Given an address at which a breakpoint is desired, return a breakpoint
3334 address adjusted to account for architectural constraints on
3335 breakpoint placement. This method is not needed by most targets.
3337 The FR-V target (see @file{frv-tdep.c}) requires this method.
3338 The FR-V is a VLIW architecture in which a number of RISC-like
3339 instructions are grouped (packed) together into an aggregate
3340 instruction or instruction bundle. When the processor executes
3341 one of these bundles, the component instructions are executed
3344 In the course of optimization, the compiler may group instructions
3345 from distinct source statements into the same bundle. The line number
3346 information associated with one of the latter statements will likely
3347 refer to some instruction other than the first one in the bundle. So,
3348 if the user attempts to place a breakpoint on one of these latter
3349 statements, @value{GDBN} must be careful to @emph{not} place the break
3350 instruction on any instruction other than the first one in the bundle.
3351 (Remember though that the instructions within a bundle execute
3352 in parallel, so the @emph{first} instruction is the instruction
3353 at the lowest address and has nothing to do with execution order.)
3355 The FR-V's @code{ADJUST_BREAKPOINT_ADDRESS} method will adjust a
3356 breakpoint's address by scanning backwards for the beginning of
3357 the bundle, returning the address of the bundle.
3359 Since the adjustment of a breakpoint may significantly alter a user's
3360 expectation, @value{GDBN} prints a warning when an adjusted breakpoint
3361 is initially set and each time that that breakpoint is hit.
3363 @item CALL_DUMMY_LOCATION
3364 @findex CALL_DUMMY_LOCATION
3365 See the file @file{inferior.h}.
3367 This method has been replaced by @code{push_dummy_code}
3368 (@pxref{push_dummy_code}).
3370 @item CANNOT_FETCH_REGISTER (@var{regno})
3371 @findex CANNOT_FETCH_REGISTER
3372 A C expression that should be nonzero if @var{regno} cannot be fetched
3373 from an inferior process. This is only relevant if
3374 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3376 @item CANNOT_STORE_REGISTER (@var{regno})
3377 @findex CANNOT_STORE_REGISTER
3378 A C expression that should be nonzero if @var{regno} should not be
3379 written to the target. This is often the case for program counters,
3380 status words, and other special registers. If this is not defined,
3381 @value{GDBN} will assume that all registers may be written.
3383 @item int CONVERT_REGISTER_P(@var{regnum})
3384 @findex CONVERT_REGISTER_P
3385 Return non-zero if register @var{regnum} can represent data values in a
3387 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3389 @item DECR_PC_AFTER_BREAK
3390 @findex DECR_PC_AFTER_BREAK
3391 Define this to be the amount by which to decrement the PC after the
3392 program encounters a breakpoint. This is often the number of bytes in
3393 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3395 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3396 @findex DISABLE_UNSETTABLE_BREAK
3397 If defined, this should evaluate to 1 if @var{addr} is in a shared
3398 library in which breakpoints cannot be set and so should be disabled.
3400 @item PRINT_FLOAT_INFO()
3401 @findex PRINT_FLOAT_INFO
3402 If defined, then the @samp{info float} command will print information about
3403 the processor's floating point unit.
3405 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3406 @findex print_registers_info
3407 If defined, pretty print the value of the register @var{regnum} for the
3408 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3409 either all registers (@var{all} is non zero) or a select subset of
3410 registers (@var{all} is zero).
3412 The default method prints one register per line, and if @var{all} is
3413 zero omits floating-point registers.
3415 @item PRINT_VECTOR_INFO()
3416 @findex PRINT_VECTOR_INFO
3417 If defined, then the @samp{info vector} command will call this function
3418 to print information about the processor's vector unit.
3420 By default, the @samp{info vector} command will print all vector
3421 registers (the register's type having the vector attribute).
3423 @item DWARF_REG_TO_REGNUM
3424 @findex DWARF_REG_TO_REGNUM
3425 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3426 no conversion will be performed.
3428 @item DWARF2_REG_TO_REGNUM
3429 @findex DWARF2_REG_TO_REGNUM
3430 Convert DWARF2 register number into @value{GDBN} regnum. If not
3431 defined, no conversion will be performed.
3433 @item ECOFF_REG_TO_REGNUM
3434 @findex ECOFF_REG_TO_REGNUM
3435 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3436 no conversion will be performed.
3438 @item END_OF_TEXT_DEFAULT
3439 @findex END_OF_TEXT_DEFAULT
3440 This is an expression that should designate the end of the text section.
3443 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3444 @findex EXTRACT_RETURN_VALUE
3445 Define this to extract a function's return value of type @var{type} from
3446 the raw register state @var{regbuf} and copy that, in virtual format,
3449 This method has been deprecated in favour of @code{gdbarch_return_value}
3450 (@pxref{gdbarch_return_value}).
3452 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3453 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS
3454 @anchor{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}
3455 When defined, extract from the array @var{regbuf} (containing the raw
3456 register state) the @code{CORE_ADDR} at which a function should return
3457 its structure value.
3459 @xref{gdbarch_return_value}.
3461 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P()
3462 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P
3463 Predicate for @code{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}.
3465 @item DEPRECATED_FP_REGNUM
3466 @findex DEPRECATED_FP_REGNUM
3467 If the virtual frame pointer is kept in a register, then define this
3468 macro to be the number (greater than or equal to zero) of that register.
3470 This should only need to be defined if @code{DEPRECATED_TARGET_READ_FP}
3473 @item DEPRECATED_FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3474 @findex DEPRECATED_FRAMELESS_FUNCTION_INVOCATION
3475 Define this to an expression that returns 1 if the function invocation
3476 represented by @var{fi} does not have a stack frame associated with it.
3479 @item frame_align (@var{address})
3480 @anchor{frame_align}
3482 Define this to adjust @var{address} so that it meets the alignment
3483 requirements for the start of a new stack frame. A stack frame's
3484 alignment requirements are typically stronger than a target processors
3485 stack alignment requirements (@pxref{DEPRECATED_STACK_ALIGN}).
3487 This function is used to ensure that, when creating a dummy frame, both
3488 the initial stack pointer and (if needed) the address of the return
3489 value are correctly aligned.
3491 Unlike @code{DEPRECATED_STACK_ALIGN}, this function always adjusts the
3492 address in the direction of stack growth.
3494 By default, no frame based stack alignment is performed.
3496 @item int frame_red_zone_size
3498 The number of bytes, beyond the innermost-stack-address, reserved by the
3499 @sc{abi}. A function is permitted to use this scratch area (instead of
3500 allocating extra stack space).
3502 When performing an inferior function call, to ensure that it does not
3503 modify this area, @value{GDBN} adjusts the innermost-stack-address by
3504 @var{frame_red_zone_size} bytes before pushing parameters onto the
3507 By default, zero bytes are allocated. The value must be aligned
3508 (@pxref{frame_align}).
3510 The @sc{amd64} (nee x86-64) @sc{abi} documentation refers to the
3511 @emph{red zone} when describing this scratch area.
3514 @item DEPRECATED_FRAME_CHAIN(@var{frame})
3515 @findex DEPRECATED_FRAME_CHAIN
3516 Given @var{frame}, return a pointer to the calling frame.
3518 @item DEPRECATED_FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3519 @findex DEPRECATED_FRAME_CHAIN_VALID
3520 Define this to be an expression that returns zero if the given frame is an
3521 outermost frame, with no caller, and nonzero otherwise. Most normal
3522 situations can be handled without defining this macro, including @code{NULL}
3523 chain pointers, dummy frames, and frames whose PC values are inside the
3524 startup file (e.g.@: @file{crt0.o}), inside @code{main}, or inside
3527 @item DEPRECATED_FRAME_INIT_SAVED_REGS(@var{frame})
3528 @findex DEPRECATED_FRAME_INIT_SAVED_REGS
3529 See @file{frame.h}. Determines the address of all registers in the
3530 current stack frame storing each in @code{frame->saved_regs}. Space for
3531 @code{frame->saved_regs} shall be allocated by
3532 @code{DEPRECATED_FRAME_INIT_SAVED_REGS} using
3533 @code{frame_saved_regs_zalloc}.
3535 @code{FRAME_FIND_SAVED_REGS} is deprecated.
3537 @item FRAME_NUM_ARGS (@var{fi})
3538 @findex FRAME_NUM_ARGS
3539 For the frame described by @var{fi} return the number of arguments that
3540 are being passed. If the number of arguments is not known, return
3543 @item DEPRECATED_FRAME_SAVED_PC(@var{frame})
3544 @findex DEPRECATED_FRAME_SAVED_PC
3545 @anchor{DEPRECATED_FRAME_SAVED_PC} Given @var{frame}, return the pc
3546 saved there. This is the return address.
3548 This method is deprecated. @xref{unwind_pc}.
3550 @item CORE_ADDR unwind_pc (struct frame_info *@var{this_frame})
3552 @anchor{unwind_pc} Return the instruction address, in @var{this_frame}'s
3553 caller, at which execution will resume after @var{this_frame} returns.
3554 This is commonly referred to as the return address.
3556 The implementation, which must be frame agnostic (work with any frame),
3557 is typically no more than:
3561 frame_unwind_unsigned_register (this_frame, D10V_PC_REGNUM, &pc);
3562 return d10v_make_iaddr (pc);
3566 @xref{DEPRECATED_FRAME_SAVED_PC}, which this method replaces.
3568 @item CORE_ADDR unwind_sp (struct frame_info *@var{this_frame})
3570 @anchor{unwind_sp} Return the frame's inner most stack address. This is
3571 commonly referred to as the frame's @dfn{stack pointer}.
3573 The implementation, which must be frame agnostic (work with any frame),
3574 is typically no more than:
3578 frame_unwind_unsigned_register (this_frame, D10V_SP_REGNUM, &sp);
3579 return d10v_make_daddr (sp);
3583 @xref{TARGET_READ_SP}, which this method replaces.
3585 @item FUNCTION_EPILOGUE_SIZE
3586 @findex FUNCTION_EPILOGUE_SIZE
3587 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3588 function end symbol is 0. For such targets, you must define
3589 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3590 function's epilogue.
3592 @item DEPRECATED_FUNCTION_START_OFFSET
3593 @findex DEPRECATED_FUNCTION_START_OFFSET
3594 An integer, giving the offset in bytes from a function's address (as
3595 used in the values of symbols, function pointers, etc.), and the
3596 function's first genuine instruction.
3598 This is zero on almost all machines: the function's address is usually
3599 the address of its first instruction. However, on the VAX, for
3600 example, each function starts with two bytes containing a bitmask
3601 indicating which registers to save upon entry to the function. The
3602 VAX @code{call} instructions check this value, and save the
3603 appropriate registers automatically. Thus, since the offset from the
3604 function's address to its first instruction is two bytes,
3605 @code{DEPRECATED_FUNCTION_START_OFFSET} would be 2 on the VAX.
3607 @item GCC_COMPILED_FLAG_SYMBOL
3608 @itemx GCC2_COMPILED_FLAG_SYMBOL
3609 @findex GCC2_COMPILED_FLAG_SYMBOL
3610 @findex GCC_COMPILED_FLAG_SYMBOL
3611 If defined, these are the names of the symbols that @value{GDBN} will
3612 look for to detect that GCC compiled the file. The default symbols
3613 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3614 respectively. (Currently only defined for the Delta 68.)
3616 @item @value{GDBN}_MULTI_ARCH
3617 @findex @value{GDBN}_MULTI_ARCH
3618 If defined and non-zero, enables support for multiple architectures
3619 within @value{GDBN}.
3621 This support can be enabled at two levels. At level one, only
3622 definitions for previously undefined macros are provided; at level two,
3623 a multi-arch definition of all architecture dependent macros will be
3626 @item @value{GDBN}_TARGET_IS_HPPA
3627 @findex @value{GDBN}_TARGET_IS_HPPA
3628 This determines whether horrible kludge code in @file{dbxread.c} and
3629 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3630 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3633 @item GET_LONGJMP_TARGET
3634 @findex GET_LONGJMP_TARGET
3635 For most machines, this is a target-dependent parameter. On the
3636 DECstation and the Iris, this is a native-dependent parameter, since
3637 the header file @file{setjmp.h} is needed to define it.
3639 This macro determines the target PC address that @code{longjmp} will jump to,
3640 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3641 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3642 pointer. It examines the current state of the machine as needed.
3644 @item DEPRECATED_GET_SAVED_REGISTER
3645 @findex DEPRECATED_GET_SAVED_REGISTER
3646 Define this if you need to supply your own definition for the function
3647 @code{DEPRECATED_GET_SAVED_REGISTER}.
3649 @item DEPRECATED_IBM6000_TARGET
3650 @findex DEPRECATED_IBM6000_TARGET
3651 Shows that we are configured for an IBM RS/6000 system. This
3652 conditional should be eliminated (FIXME) and replaced by
3653 feature-specific macros. It was introduced in a haste and we are
3654 repenting at leisure.
3656 @item I386_USE_GENERIC_WATCHPOINTS
3657 An x86-based target can define this to use the generic x86 watchpoint
3658 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3660 @item SYMBOLS_CAN_START_WITH_DOLLAR
3661 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3662 Some systems have routines whose names start with @samp{$}. Giving this
3663 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3664 routines when parsing tokens that begin with @samp{$}.
3666 On HP-UX, certain system routines (millicode) have names beginning with
3667 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3668 routine that handles inter-space procedure calls on PA-RISC.
3670 @item DEPRECATED_INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3671 @findex DEPRECATED_INIT_EXTRA_FRAME_INFO
3672 If additional information about the frame is required this should be
3673 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3674 is allocated using @code{frame_extra_info_zalloc}.
3676 @item DEPRECATED_INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3677 @findex DEPRECATED_INIT_FRAME_PC
3678 This is a C statement that sets the pc of the frame pointed to by
3679 @var{prev}. [By default...]
3681 @item INNER_THAN (@var{lhs}, @var{rhs})
3683 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3684 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3685 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3688 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3689 @findex gdbarch_in_function_epilogue_p
3690 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3691 The epilogue of a function is defined as the part of a function where
3692 the stack frame of the function already has been destroyed up to the
3693 final `return from function call' instruction.
3695 @item DEPRECATED_SIGTRAMP_START (@var{pc})
3696 @findex DEPRECATED_SIGTRAMP_START
3697 @itemx DEPRECATED_SIGTRAMP_END (@var{pc})
3698 @findex DEPRECATED_SIGTRAMP_END
3699 Define these to be the start and end address of the @code{sigtramp} for the
3700 given @var{pc}. On machines where the address is just a compile time
3701 constant, the macro expansion will typically just ignore the supplied
3704 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3705 @findex IN_SOLIB_CALL_TRAMPOLINE
3706 Define this to evaluate to nonzero if the program is stopped in the
3707 trampoline that connects to a shared library.
3709 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3710 @findex IN_SOLIB_RETURN_TRAMPOLINE
3711 Define this to evaluate to nonzero if the program is stopped in the
3712 trampoline that returns from a shared library.
3714 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3715 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3716 Define this to evaluate to nonzero if the program is stopped in the
3719 @item SKIP_SOLIB_RESOLVER (@var{pc})
3720 @findex SKIP_SOLIB_RESOLVER
3721 Define this to evaluate to the (nonzero) address at which execution
3722 should continue to get past the dynamic linker's symbol resolution
3723 function. A zero value indicates that it is not important or necessary
3724 to set a breakpoint to get through the dynamic linker and that single
3725 stepping will suffice.
3727 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3728 @findex INTEGER_TO_ADDRESS
3729 @cindex converting integers to addresses
3730 Define this when the architecture needs to handle non-pointer to address
3731 conversions specially. Converts that value to an address according to
3732 the current architectures conventions.
3734 @emph{Pragmatics: When the user copies a well defined expression from
3735 their source code and passes it, as a parameter, to @value{GDBN}'s
3736 @code{print} command, they should get the same value as would have been
3737 computed by the target program. Any deviation from this rule can cause
3738 major confusion and annoyance, and needs to be justified carefully. In
3739 other words, @value{GDBN} doesn't really have the freedom to do these
3740 conversions in clever and useful ways. It has, however, been pointed
3741 out that users aren't complaining about how @value{GDBN} casts integers
3742 to pointers; they are complaining that they can't take an address from a
3743 disassembly listing and give it to @code{x/i}. Adding an architecture
3744 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3745 @value{GDBN} to ``get it right'' in all circumstances.}
3747 @xref{Target Architecture Definition, , Pointers Are Not Always
3750 @item NO_HIF_SUPPORT
3751 @findex NO_HIF_SUPPORT
3752 (Specific to the a29k.)
3754 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3755 @findex POINTER_TO_ADDRESS
3756 Assume that @var{buf} holds a pointer of type @var{type}, in the
3757 appropriate format for the current architecture. Return the byte
3758 address the pointer refers to.
3759 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3761 @item REGISTER_CONVERTIBLE (@var{reg})
3762 @findex REGISTER_CONVERTIBLE
3763 Return non-zero if @var{reg} uses different raw and virtual formats.
3764 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3766 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3767 @findex REGISTER_TO_VALUE
3768 Convert the raw contents of register @var{regnum} into a value of type
3770 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3772 @item DEPRECATED_REGISTER_RAW_SIZE (@var{reg})
3773 @findex DEPRECATED_REGISTER_RAW_SIZE
3774 Return the raw size of @var{reg}; defaults to the size of the register's
3776 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3778 @item register_reggroup_p (@var{gdbarch}, @var{regnum}, @var{reggroup})
3779 @findex register_reggroup_p
3780 @cindex register groups
3781 Return non-zero if register @var{regnum} is a member of the register
3782 group @var{reggroup}.
3784 By default, registers are grouped as follows:
3787 @item float_reggroup
3788 Any register with a valid name and a floating-point type.
3789 @item vector_reggroup
3790 Any register with a valid name and a vector type.
3791 @item general_reggroup
3792 Any register with a valid name and a type other than vector or
3793 floating-point. @samp{float_reggroup}.
3795 @itemx restore_reggroup
3797 Any register with a valid name.
3800 @item DEPRECATED_REGISTER_VIRTUAL_SIZE (@var{reg})
3801 @findex DEPRECATED_REGISTER_VIRTUAL_SIZE
3802 Return the virtual size of @var{reg}; defaults to the size of the
3803 register's virtual type.
3804 Return the virtual size of @var{reg}.
3805 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3807 @item DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})
3808 @findex REGISTER_VIRTUAL_TYPE
3809 Return the virtual type of @var{reg}.
3810 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3812 @item struct type *register_type (@var{gdbarch}, @var{reg})
3813 @findex register_type
3814 If defined, return the type of register @var{reg}. This function
3815 supersedes @code{DEPRECATED_REGISTER_VIRTUAL_TYPE}. @xref{Target Architecture
3816 Definition, , Raw and Virtual Register Representations}.
3818 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3819 @findex REGISTER_CONVERT_TO_VIRTUAL
3820 Convert the value of register @var{reg} from its raw form to its virtual
3822 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3824 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3825 @findex REGISTER_CONVERT_TO_RAW
3826 Convert the value of register @var{reg} from its virtual form to its raw
3828 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3830 @item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size})
3831 @findex regset_from_core_section
3832 Return the appropriate register set for a core file section with name
3833 @var{sect_name} and size @var{sect_size}.
3835 @item SOFTWARE_SINGLE_STEP_P()
3836 @findex SOFTWARE_SINGLE_STEP_P
3837 Define this as 1 if the target does not have a hardware single-step
3838 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3840 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p})
3841 @findex SOFTWARE_SINGLE_STEP
3842 A function that inserts or removes (depending on
3843 @var{insert_breakpoints_p}) breakpoints at each possible destinations of
3844 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3847 @item SOFUN_ADDRESS_MAYBE_MISSING
3848 @findex SOFUN_ADDRESS_MAYBE_MISSING
3849 Somebody clever observed that, the more actual addresses you have in the
3850 debug information, the more time the linker has to spend relocating
3851 them. So whenever there's some other way the debugger could find the
3852 address it needs, you should omit it from the debug info, to make
3855 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3856 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3857 entries in stabs-format debugging information. @code{N_SO} stabs mark
3858 the beginning and ending addresses of compilation units in the text
3859 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3861 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3865 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3866 addresses where the function starts by taking the function name from
3867 the stab, and then looking that up in the minsyms (the
3868 linker/assembler symbol table). In other words, the stab has the
3869 name, and the linker/assembler symbol table is the only place that carries
3873 @code{N_SO} stabs have an address of zero, too. You just look at the
3874 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3875 and guess the starting and ending addresses of the compilation unit from
3879 @item PC_LOAD_SEGMENT
3880 @findex PC_LOAD_SEGMENT
3881 If defined, print information about the load segment for the program
3882 counter. (Defined only for the RS/6000.)
3886 If the program counter is kept in a register, then define this macro to
3887 be the number (greater than or equal to zero) of that register.
3889 This should only need to be defined if @code{TARGET_READ_PC} and
3890 @code{TARGET_WRITE_PC} are not defined.
3893 @findex PARM_BOUNDARY
3894 If non-zero, round arguments to a boundary of this many bits before
3895 pushing them on the stack.
3897 @item stabs_argument_has_addr (@var{gdbarch}, @var{type})
3898 @findex stabs_argument_has_addr
3899 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3900 @anchor{stabs_argument_has_addr} Define this to return nonzero if a
3901 function argument of type @var{type} is passed by reference instead of
3904 This method replaces @code{DEPRECATED_REG_STRUCT_HAS_ADDR}
3905 (@pxref{DEPRECATED_REG_STRUCT_HAS_ADDR}).
3907 @item PROCESS_LINENUMBER_HOOK
3908 @findex PROCESS_LINENUMBER_HOOK
3909 A hook defined for XCOFF reading.
3911 @item PROLOGUE_FIRSTLINE_OVERLAP
3912 @findex PROLOGUE_FIRSTLINE_OVERLAP
3913 (Only used in unsupported Convex configuration.)
3917 If defined, this is the number of the processor status register. (This
3918 definition is only used in generic code when parsing "$ps".)
3920 @item DEPRECATED_POP_FRAME
3921 @findex DEPRECATED_POP_FRAME
3923 If defined, used by @code{frame_pop} to remove a stack frame. This
3924 method has been superseded by generic code.
3926 @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})
3927 @findex push_dummy_call
3928 @findex DEPRECATED_PUSH_ARGUMENTS.
3929 @anchor{push_dummy_call} Define this to push the dummy frame's call to
3930 the inferior function onto the stack. In addition to pushing
3931 @var{nargs}, the code should push @var{struct_addr} (when
3932 @var{struct_return}), and the return address (@var{bp_addr}).
3934 @var{function} is a pointer to a @code{struct value}; on architectures that use
3935 function descriptors, this contains the function descriptor value.
3937 Returns the updated top-of-stack pointer.
3939 This method replaces @code{DEPRECATED_PUSH_ARGUMENTS}.
3941 @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})
3942 @findex push_dummy_code
3943 @anchor{push_dummy_code} Given a stack based call dummy, push the
3944 instruction sequence (including space for a breakpoint) to which the
3945 called function should return.
3947 Set @var{bp_addr} to the address at which the breakpoint instruction
3948 should be inserted, @var{real_pc} to the resume address when starting
3949 the call sequence, and return the updated inner-most stack address.
3951 By default, the stack is grown sufficient to hold a frame-aligned
3952 (@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address
3953 reserved for that breakpoint, and @var{real_pc} set to @var{funaddr}.
3955 This method replaces @code{CALL_DUMMY_LOCATION},
3956 @code{DEPRECATED_REGISTER_SIZE}.
3958 @item REGISTER_NAME(@var{i})
3959 @findex REGISTER_NAME
3960 Return the name of register @var{i} as a string. May return @code{NULL}
3961 or @code{NUL} to indicate that register @var{i} is not valid.
3963 @item DEPRECATED_REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3964 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3965 @anchor{DEPRECATED_REG_STRUCT_HAS_ADDR}Define this to return 1 if the
3966 given type will be passed by pointer rather than directly.
3968 This method has been replaced by @code{stabs_argument_has_addr}
3969 (@pxref{stabs_argument_has_addr}).
3971 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3972 @findex SAVE_DUMMY_FRAME_TOS
3973 @anchor{SAVE_DUMMY_FRAME_TOS} Used in @samp{call_function_by_hand} to
3974 notify the target dependent code of the top-of-stack value that will be
3975 passed to the inferior code. This is the value of the @code{SP}
3976 after both the dummy frame and space for parameters/results have been
3977 allocated on the stack. @xref{unwind_dummy_id}.
3979 @item SDB_REG_TO_REGNUM
3980 @findex SDB_REG_TO_REGNUM
3981 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3982 defined, no conversion will be done.
3984 @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})
3985 @findex gdbarch_return_value
3986 @anchor{gdbarch_return_value} Given a function with a return-value of
3987 type @var{rettype}, return which return-value convention that function
3990 @value{GDBN} currently recognizes two function return-value conventions:
3991 @code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found
3992 in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return
3993 value is found in memory and the address of that memory location is
3994 passed in as the function's first parameter.
3996 If the register convention is being used, and @var{writebuf} is
3997 non-@code{NULL}, also copy the return-value in @var{writebuf} into
4000 If the register convention is being used, and @var{readbuf} is
4001 non-@code{NULL}, also copy the return value from @var{regcache} into
4002 @var{readbuf} (@var{regcache} contains a copy of the registers from the
4003 just returned function).
4005 @xref{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}, for a description of how
4006 return-values that use the struct convention are handled.
4008 @emph{Maintainer note: This method replaces separate predicate, extract,
4009 store methods. By having only one method, the logic needed to determine
4010 the return-value convention need only be implemented in one place. If
4011 @value{GDBN} were written in an @sc{oo} language, this method would
4012 instead return an object that knew how to perform the register
4013 return-value extract and store.}
4015 @emph{Maintainer note: This method does not take a @var{gcc_p}
4016 parameter, and such a parameter should not be added. If an architecture
4017 that requires per-compiler or per-function information be identified,
4018 then the replacement of @var{rettype} with @code{struct value}
4019 @var{function} should be pursued.}
4021 @emph{Maintainer note: The @var{regcache} parameter limits this methods
4022 to the inner most frame. While replacing @var{regcache} with a
4023 @code{struct frame_info} @var{frame} parameter would remove that
4024 limitation there has yet to be a demonstrated need for such a change.}
4026 @item SKIP_PERMANENT_BREAKPOINT
4027 @findex SKIP_PERMANENT_BREAKPOINT
4028 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
4029 steps over a breakpoint by removing it, stepping one instruction, and
4030 re-inserting the breakpoint. However, permanent breakpoints are
4031 hardwired into the inferior, and can't be removed, so this strategy
4032 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
4033 state so that execution will resume just after the breakpoint. This
4034 macro does the right thing even when the breakpoint is in the delay slot
4035 of a branch or jump.
4037 @item SKIP_PROLOGUE (@var{pc})
4038 @findex SKIP_PROLOGUE
4039 A C expression that returns the address of the ``real'' code beyond the
4040 function entry prologue found at @var{pc}.
4042 @item SKIP_TRAMPOLINE_CODE (@var{pc})
4043 @findex SKIP_TRAMPOLINE_CODE
4044 If the target machine has trampoline code that sits between callers and
4045 the functions being called, then define this macro to return a new PC
4046 that is at the start of the real function.
4050 If the stack-pointer is kept in a register, then define this macro to be
4051 the number (greater than or equal to zero) of that register, or -1 if
4052 there is no such register.
4054 @item STAB_REG_TO_REGNUM
4055 @findex STAB_REG_TO_REGNUM
4056 Define this to convert stab register numbers (as gotten from `r'
4057 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
4060 @item DEPRECATED_STACK_ALIGN (@var{addr})
4061 @anchor{DEPRECATED_STACK_ALIGN}
4062 @findex DEPRECATED_STACK_ALIGN
4063 Define this to increase @var{addr} so that it meets the alignment
4064 requirements for the processor's stack.
4066 Unlike @ref{frame_align}, this function always adjusts @var{addr}
4069 By default, no stack alignment is performed.
4071 @item STEP_SKIPS_DELAY (@var{addr})
4072 @findex STEP_SKIPS_DELAY
4073 Define this to return true if the address is of an instruction with a
4074 delay slot. If a breakpoint has been placed in the instruction's delay
4075 slot, @value{GDBN} will single-step over that instruction before resuming
4076 normally. Currently only defined for the Mips.
4078 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
4079 @findex STORE_RETURN_VALUE
4080 A C expression that writes the function return value, found in
4081 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
4082 value that is to be returned.
4084 This method has been deprecated in favour of @code{gdbarch_return_value}
4085 (@pxref{gdbarch_return_value}).
4087 @item SYMBOL_RELOADING_DEFAULT
4088 @findex SYMBOL_RELOADING_DEFAULT
4089 The default value of the ``symbol-reloading'' variable. (Never defined in
4092 @item TARGET_CHAR_BIT
4093 @findex TARGET_CHAR_BIT
4094 Number of bits in a char; defaults to 8.
4096 @item TARGET_CHAR_SIGNED
4097 @findex TARGET_CHAR_SIGNED
4098 Non-zero if @code{char} is normally signed on this architecture; zero if
4099 it should be unsigned.
4101 The ISO C standard requires the compiler to treat @code{char} as
4102 equivalent to either @code{signed char} or @code{unsigned char}; any
4103 character in the standard execution set is supposed to be positive.
4104 Most compilers treat @code{char} as signed, but @code{char} is unsigned
4105 on the IBM S/390, RS6000, and PowerPC targets.
4107 @item TARGET_COMPLEX_BIT
4108 @findex TARGET_COMPLEX_BIT
4109 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
4111 At present this macro is not used.
4113 @item TARGET_DOUBLE_BIT
4114 @findex TARGET_DOUBLE_BIT
4115 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
4117 @item TARGET_DOUBLE_COMPLEX_BIT
4118 @findex TARGET_DOUBLE_COMPLEX_BIT
4119 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
4121 At present this macro is not used.
4123 @item TARGET_FLOAT_BIT
4124 @findex TARGET_FLOAT_BIT
4125 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
4127 @item TARGET_INT_BIT
4128 @findex TARGET_INT_BIT
4129 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4131 @item TARGET_LONG_BIT
4132 @findex TARGET_LONG_BIT
4133 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4135 @item TARGET_LONG_DOUBLE_BIT
4136 @findex TARGET_LONG_DOUBLE_BIT
4137 Number of bits in a long double float;
4138 defaults to @code{2 * TARGET_DOUBLE_BIT}.
4140 @item TARGET_LONG_LONG_BIT
4141 @findex TARGET_LONG_LONG_BIT
4142 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
4144 @item TARGET_PTR_BIT
4145 @findex TARGET_PTR_BIT
4146 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
4148 @item TARGET_SHORT_BIT
4149 @findex TARGET_SHORT_BIT
4150 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
4152 @item TARGET_READ_PC
4153 @findex TARGET_READ_PC
4154 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
4155 @findex TARGET_WRITE_PC
4156 @anchor{TARGET_WRITE_PC}
4157 @itemx TARGET_READ_SP
4158 @findex TARGET_READ_SP
4159 @itemx TARGET_READ_FP
4160 @findex TARGET_READ_FP
4165 @anchor{TARGET_READ_SP} These change the behavior of @code{read_pc},
4166 @code{write_pc}, and @code{read_sp}. For most targets, these may be
4167 left undefined. @value{GDBN} will call the read and write register
4168 functions with the relevant @code{_REGNUM} argument.
4170 These macros are useful when a target keeps one of these registers in a
4171 hard to get at place; for example, part in a segment register and part
4172 in an ordinary register.
4174 @xref{unwind_sp}, which replaces @code{TARGET_READ_SP}.
4176 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
4177 @findex TARGET_VIRTUAL_FRAME_POINTER
4178 Returns a @code{(register, offset)} pair representing the virtual frame
4179 pointer in use at the code address @var{pc}. If virtual frame pointers
4180 are not used, a default definition simply returns
4181 @code{DEPRECATED_FP_REGNUM}, with an offset of zero.
4183 @item TARGET_HAS_HARDWARE_WATCHPOINTS
4184 If non-zero, the target has support for hardware-assisted
4185 watchpoints. @xref{Algorithms, watchpoints}, for more details and
4186 other related macros.
4188 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
4189 @findex TARGET_PRINT_INSN
4190 This is the function used by @value{GDBN} to print an assembly
4191 instruction. It prints the instruction at address @var{addr} in
4192 debugged memory and returns the length of the instruction, in bytes. If
4193 a target doesn't define its own printing routine, it defaults to an
4194 accessor function for the global pointer
4195 @code{deprecated_tm_print_insn}. This usually points to a function in
4196 the @code{opcodes} library (@pxref{Support Libraries, ,Opcodes}).
4197 @var{info} is a structure (of type @code{disassemble_info}) defined in
4198 @file{include/dis-asm.h} used to pass information to the instruction
4201 @item struct frame_id unwind_dummy_id (struct frame_info *@var{frame})
4202 @findex unwind_dummy_id
4203 @anchor{unwind_dummy_id} Given @var{frame} return a @code{struct
4204 frame_id} that uniquely identifies an inferior function call's dummy
4205 frame. The value returned must match the dummy frame stack value
4206 previously saved using @code{SAVE_DUMMY_FRAME_TOS}.
4207 @xref{SAVE_DUMMY_FRAME_TOS}.
4209 @item DEPRECATED_USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
4210 @findex DEPRECATED_USE_STRUCT_CONVENTION
4211 If defined, this must be an expression that is nonzero if a value of the
4212 given @var{type} being returned from a function must have space
4213 allocated for it on the stack. @var{gcc_p} is true if the function
4214 being considered is known to have been compiled by GCC; this is helpful
4215 for systems where GCC is known to use different calling convention than
4218 This method has been deprecated in favour of @code{gdbarch_return_value}
4219 (@pxref{gdbarch_return_value}).
4221 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
4222 @findex VALUE_TO_REGISTER
4223 Convert a value of type @var{type} into the raw contents of register
4225 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4227 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4228 @findex VARIABLES_INSIDE_BLOCK
4229 For dbx-style debugging information, if the compiler puts variable
4230 declarations inside LBRAC/RBRAC blocks, this should be defined to be
4231 nonzero. @var{desc} is the value of @code{n_desc} from the
4232 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
4233 presence of either the @code{GCC_COMPILED_SYMBOL} or the
4234 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
4236 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4237 @findex OS9K_VARIABLES_INSIDE_BLOCK
4238 Similarly, for OS/9000. Defaults to 1.
4241 Motorola M68K target conditionals.
4245 Define this to be the 4-bit location of the breakpoint trap vector. If
4246 not defined, it will default to @code{0xf}.
4248 @item REMOTE_BPT_VECTOR
4249 Defaults to @code{1}.
4251 @item NAME_OF_MALLOC
4252 @findex NAME_OF_MALLOC
4253 A string containing the name of the function to call in order to
4254 allocate some memory in the inferior. The default value is "malloc".
4258 @section Adding a New Target
4260 @cindex adding a target
4261 The following files add a target to @value{GDBN}:
4265 @item gdb/config/@var{arch}/@var{ttt}.mt
4266 Contains a Makefile fragment specific to this target. Specifies what
4267 object files are needed for target @var{ttt}, by defining
4268 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
4269 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
4272 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
4273 but these are now deprecated, replaced by autoconf, and may go away in
4274 future versions of @value{GDBN}.
4276 @item gdb/@var{ttt}-tdep.c
4277 Contains any miscellaneous code required for this target machine. On
4278 some machines it doesn't exist at all. Sometimes the macros in
4279 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
4280 as functions here instead, and the macro is simply defined to call the
4281 function. This is vastly preferable, since it is easier to understand
4284 @item gdb/@var{arch}-tdep.c
4285 @itemx gdb/@var{arch}-tdep.h
4286 This often exists to describe the basic layout of the target machine's
4287 processor chip (registers, stack, etc.). If used, it is included by
4288 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
4291 @item gdb/config/@var{arch}/tm-@var{ttt}.h
4292 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
4293 macro definitions about the target machine's registers, stack frame
4294 format and instructions.
4296 New targets do not need this file and should not create it.
4298 @item gdb/config/@var{arch}/tm-@var{arch}.h
4299 This often exists to describe the basic layout of the target machine's
4300 processor chip (registers, stack, etc.). If used, it is included by
4301 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
4304 New targets do not need this file and should not create it.
4308 If you are adding a new operating system for an existing CPU chip, add a
4309 @file{config/tm-@var{os}.h} file that describes the operating system
4310 facilities that are unusual (extra symbol table info; the breakpoint
4311 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
4312 that just @code{#include}s @file{tm-@var{arch}.h} and
4313 @file{config/tm-@var{os}.h}.
4316 @section Converting an existing Target Architecture to Multi-arch
4317 @cindex converting targets to multi-arch
4319 This section describes the current accepted best practice for converting
4320 an existing target architecture to the multi-arch framework.
4322 The process consists of generating, testing, posting and committing a
4323 sequence of patches. Each patch must contain a single change, for
4329 Directly convert a group of functions into macros (the conversion does
4330 not change the behavior of any of the functions).
4333 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4337 Enable multi-arch level one.
4340 Delete one or more files.
4345 There isn't a size limit on a patch, however, a developer is strongly
4346 encouraged to keep the patch size down.
4348 Since each patch is well defined, and since each change has been tested
4349 and shows no regressions, the patches are considered @emph{fairly}
4350 obvious. Such patches, when submitted by developers listed in the
4351 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4352 process may be more complicated and less clear. The developer is
4353 expected to use their judgment and is encouraged to seek advice as
4356 @subsection Preparation
4358 The first step is to establish control. Build (with @option{-Werror}
4359 enabled) and test the target so that there is a baseline against which
4360 the debugger can be compared.
4362 At no stage can the test results regress or @value{GDBN} stop compiling
4363 with @option{-Werror}.
4365 @subsection Add the multi-arch initialization code
4367 The objective of this step is to establish the basic multi-arch
4368 framework. It involves
4373 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4374 above is from the original example and uses K&R C. @value{GDBN}
4375 has since converted to ISO C but lets ignore that.} that creates
4378 static struct gdbarch *
4379 d10v_gdbarch_init (info, arches)
4380 struct gdbarch_info info;
4381 struct gdbarch_list *arches;
4383 struct gdbarch *gdbarch;
4384 /* there is only one d10v architecture */
4386 return arches->gdbarch;
4387 gdbarch = gdbarch_alloc (&info, NULL);
4395 A per-architecture dump function to print any architecture specific
4399 mips_dump_tdep (struct gdbarch *current_gdbarch,
4400 struct ui_file *file)
4402 @dots{} code to print architecture specific info @dots{}
4407 A change to @code{_initialize_@var{arch}_tdep} to register this new
4411 _initialize_mips_tdep (void)
4413 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4418 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4419 @file{config/@var{arch}/tm-@var{arch}.h}.
4423 @subsection Update multi-arch incompatible mechanisms
4425 Some mechanisms do not work with multi-arch. They include:
4428 @item FRAME_FIND_SAVED_REGS
4429 Replaced with @code{DEPRECATED_FRAME_INIT_SAVED_REGS}
4433 At this stage you could also consider converting the macros into
4436 @subsection Prepare for multi-arch level to one
4438 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4439 and then build and start @value{GDBN} (the change should not be
4440 committed). @value{GDBN} may not build, and once built, it may die with
4441 an internal error listing the architecture methods that must be
4444 Fix any build problems (patch(es)).
4446 Convert all the architecture methods listed, which are only macros, into
4447 functions (patch(es)).
4449 Update @code{@var{arch}_gdbarch_init} to set all the missing
4450 architecture methods and wrap the corresponding macros in @code{#if
4451 !GDB_MULTI_ARCH} (patch(es)).
4453 @subsection Set multi-arch level one
4455 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4458 Any problems with throwing ``the switch'' should have been fixed
4461 @subsection Convert remaining macros
4463 Suggest converting macros into functions (and setting the corresponding
4464 architecture method) in small batches.
4466 @subsection Set multi-arch level to two
4468 This should go smoothly.
4470 @subsection Delete the TM file
4472 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4473 @file{configure.in} updated.
4476 @node Target Descriptions
4477 @chapter Target Descriptions
4478 @cindex target descriptions
4480 The target architecture definition (@pxref{Target Architecture Definition})
4481 contains @value{GDBN}'s hard-coded knowledge about an architecture. For
4482 some platforms, it is handy to have more flexible knowledge about a specific
4483 instance of the architecture---for instance, a processor or development board.
4484 @dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN}
4485 more about what their target supports, or for the target to tell @value{GDBN}
4488 For details on writing, automatically supplying, and manually selecting
4489 target descriptions, see @ref{Target Descriptions, , , gdb,
4490 Debugging with @value{GDBN}}. This section will cover some related
4491 topics about the @value{GDBN} internals.
4494 * Target Descriptions Implementation::
4495 * Adding Target Described Register Support::
4498 @node Target Descriptions Implementation
4499 @section Target Descriptions Implementation
4500 @cindex target descriptions, implementation
4502 Before @value{GDBN} connects to a new target, or runs a new program on
4503 an existing target, it discards any existing target description and
4504 reverts to a default gdbarch. Then, after connecting, it looks for a
4505 new target description by calling @code{target_find_description}.
4507 A description may come from a user specified file (XML), the remote
4508 @samp{qXfer:features:read} packet (also XML), or from any custom
4509 @code{to_read_description} routine in the target vector. For instance,
4510 the remote target supports guessing whether a MIPS target is 32-bit or
4511 64-bit based on the size of the @samp{g} packet.
4513 If any target description is found, @value{GDBN} creates a new gdbarch
4514 incorporating the description by calling @code{gdbarch_update_p}. Any
4515 @samp{<architecture>} element is handled first, to determine which
4516 architecture's gdbarch initialization routine is called to create the
4517 new architecture. Then the initialization routine is called, and has
4518 a chance to adjust the constructed architecture based on the contents
4519 of the target description. For instance, it can recognize any
4520 properties set by a @code{to_read_description} routine. Also
4521 see @ref{Adding Target Described Register Support}.
4523 @node Adding Target Described Register Support
4524 @section Adding Target Described Register Support
4525 @cindex target descriptions, adding register support
4527 Target descriptions can report additional registers specific to an
4528 instance of the target. But it takes a little work in the architecture
4529 specific routines to support this.
4531 A target description must either have no registers or a complete
4532 set---this avoids complexity in trying to merge standard registers
4533 with the target defined registers. It is the architecture's
4534 responsibility to validate that a description with registers has
4535 everything it needs. To keep architecture code simple, the same
4536 mechanism is used to assign fixed internal register numbers to
4539 If @code{tdesc_has_registers} returns 1, the description contains
4540 registers. The architecture's @code{gdbarch_init} routine should:
4545 Call @code{tdesc_data_alloc} to allocate storage, early, before
4546 searching for a matching gdbarch or allocating a new one.
4549 Use @code{tdesc_find_feature} to locate standard features by name.
4552 Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices}
4553 to locate the expected registers in the standard features.
4556 Return @code{NULL} if a required feature is missing, or if any standard
4557 feature is missing expected registers. This will produce a warning that
4558 the description was incomplete.
4561 Free the allocated data before returning, unless @code{tdesc_use_registers}
4565 Call @code{set_gdbarch_num_regs} as usual, with a number higher than any
4566 fixed number passed to @code{tdesc_numbered_register}.
4569 Call @code{tdesc_use_registers} after creating a new gdbarch, before
4574 After @code{tdesc_use_registers} has been called, the architecture's
4575 @code{register_name}, @code{register_type}, and @code{register_reggroup_p}
4576 routines will not be called; that information will be taken from
4577 the target description. @code{num_regs} may be increased to account
4578 for any additional registers in the description.
4580 Pseudo-registers require some extra care:
4585 Using @code{tdesc_numbered_register} allows the architecture to give
4586 constant register numbers to standard architectural registers, e.g.@:
4587 as an @code{enum} in @file{@var{arch}-tdep.h}. But because
4588 pseudo-registers are always numbered above @code{num_regs},
4589 which may be increased by the description, constant numbers
4590 can not be used for pseudos. They must be numbered relative to
4591 @code{num_regs} instead.
4594 The description will not describe pseudo-registers, so the
4595 architecture must call @code{set_tdesc_pseudo_register_name},
4596 @code{set_tdesc_pseudo_register_type}, and
4597 @code{set_tdesc_pseudo_register_reggroup_p} to supply routines
4598 describing pseudo registers. These routines will be passed
4599 internal register numbers, so the same routines used for the
4600 gdbarch equivalents are usually suitable.
4605 @node Target Vector Definition
4607 @chapter Target Vector Definition
4608 @cindex target vector
4610 The target vector defines the interface between @value{GDBN}'s
4611 abstract handling of target systems, and the nitty-gritty code that
4612 actually exercises control over a process or a serial port.
4613 @value{GDBN} includes some 30-40 different target vectors; however,
4614 each configuration of @value{GDBN} includes only a few of them.
4617 * Managing Execution State::
4618 * Existing Targets::
4621 @node Managing Execution State
4622 @section Managing Execution State
4623 @cindex execution state
4625 A target vector can be completely inactive (not pushed on the target
4626 stack), active but not running (pushed, but not connected to a fully
4627 manifested inferior), or completely active (pushed, with an accessible
4628 inferior). Most targets are only completely inactive or completely
4629 active, but some support persistent connections to a target even
4630 when the target has exited or not yet started.
4632 For example, connecting to the simulator using @code{target sim} does
4633 not create a running program. Neither registers nor memory are
4634 accessible until @code{run}. Similarly, after @code{kill}, the
4635 program can not continue executing. But in both cases @value{GDBN}
4636 remains connected to the simulator, and target-specific commands
4637 are directed to the simulator.
4639 A target which only supports complete activation should push itself
4640 onto the stack in its @code{to_open} routine (by calling
4641 @code{push_target}), and unpush itself from the stack in its
4642 @code{to_mourn_inferior} routine (by calling @code{unpush_target}).
4644 A target which supports both partial and complete activation should
4645 still call @code{push_target} in @code{to_open}, but not call
4646 @code{unpush_target} in @code{to_mourn_inferior}. Instead, it should
4647 call either @code{target_mark_running} or @code{target_mark_exited}
4648 in its @code{to_open}, depending on whether the target is fully active
4649 after connection. It should also call @code{target_mark_running} any
4650 time the inferior becomes fully active (e.g.@: in
4651 @code{to_create_inferior} and @code{to_attach}), and
4652 @code{target_mark_exited} when the inferior becomes inactive (in
4653 @code{to_mourn_inferior}). The target should also make sure to call
4654 @code{target_mourn_inferior} from its @code{to_kill}, to return the
4655 target to inactive state.
4657 @node Existing Targets
4658 @section Existing Targets
4661 @subsection File Targets
4663 Both executables and core files have target vectors.
4665 @subsection Standard Protocol and Remote Stubs
4667 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4668 that runs in the target system. @value{GDBN} provides several sample
4669 @dfn{stubs} that can be integrated into target programs or operating
4670 systems for this purpose; they are named @file{*-stub.c}.
4672 The @value{GDBN} user's manual describes how to put such a stub into
4673 your target code. What follows is a discussion of integrating the
4674 SPARC stub into a complicated operating system (rather than a simple
4675 program), by Stu Grossman, the author of this stub.
4677 The trap handling code in the stub assumes the following upon entry to
4682 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4688 you are in the correct trap window.
4691 As long as your trap handler can guarantee those conditions, then there
4692 is no reason why you shouldn't be able to ``share'' traps with the stub.
4693 The stub has no requirement that it be jumped to directly from the
4694 hardware trap vector. That is why it calls @code{exceptionHandler()},
4695 which is provided by the external environment. For instance, this could
4696 set up the hardware traps to actually execute code which calls the stub
4697 first, and then transfers to its own trap handler.
4699 For the most point, there probably won't be much of an issue with
4700 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4701 and often indicate unrecoverable error conditions. Anyway, this is all
4702 controlled by a table, and is trivial to modify. The most important
4703 trap for us is for @code{ta 1}. Without that, we can't single step or
4704 do breakpoints. Everything else is unnecessary for the proper operation
4705 of the debugger/stub.
4707 From reading the stub, it's probably not obvious how breakpoints work.
4708 They are simply done by deposit/examine operations from @value{GDBN}.
4710 @subsection ROM Monitor Interface
4712 @subsection Custom Protocols
4714 @subsection Transport Layer
4716 @subsection Builtin Simulator
4719 @node Native Debugging
4721 @chapter Native Debugging
4722 @cindex native debugging
4724 Several files control @value{GDBN}'s configuration for native support:
4728 @item gdb/config/@var{arch}/@var{xyz}.mh
4729 Specifies Makefile fragments needed by a @emph{native} configuration on
4730 machine @var{xyz}. In particular, this lists the required
4731 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4732 Also specifies the header file which describes native support on
4733 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4734 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4735 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4737 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4738 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4739 on machine @var{xyz}. While the file is no longer used for this
4740 purpose, the @file{.mh} suffix remains. Perhaps someone will
4741 eventually rename these fragments so that they have a @file{.mn}
4744 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4745 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4746 macro definitions describing the native system environment, such as
4747 child process control and core file support.
4749 @item gdb/@var{xyz}-nat.c
4750 Contains any miscellaneous C code required for this native support of
4751 this machine. On some machines it doesn't exist at all.
4754 There are some ``generic'' versions of routines that can be used by
4755 various systems. These can be customized in various ways by macros
4756 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4757 the @var{xyz} host, you can just include the generic file's name (with
4758 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4760 Otherwise, if your machine needs custom support routines, you will need
4761 to write routines that perform the same functions as the generic file.
4762 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4763 into @code{NATDEPFILES}.
4767 This contains the @emph{target_ops vector} that supports Unix child
4768 processes on systems which use ptrace and wait to control the child.
4771 This contains the @emph{target_ops vector} that supports Unix child
4772 processes on systems which use /proc to control the child.
4775 This does the low-level grunge that uses Unix system calls to do a ``fork
4776 and exec'' to start up a child process.
4779 This is the low level interface to inferior processes for systems using
4780 the Unix @code{ptrace} call in a vanilla way.
4783 @section Native core file Support
4784 @cindex native core files
4787 @findex fetch_core_registers
4788 @item core-aout.c::fetch_core_registers()
4789 Support for reading registers out of a core file. This routine calls
4790 @code{register_addr()}, see below. Now that BFD is used to read core
4791 files, virtually all machines should use @code{core-aout.c}, and should
4792 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4793 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4795 @item core-aout.c::register_addr()
4796 If your @code{nm-@var{xyz}.h} file defines the macro
4797 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4798 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4799 register number @code{regno}. @code{blockend} is the offset within the
4800 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4801 @file{core-aout.c} will define the @code{register_addr()} function and
4802 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4803 you are using the standard @code{fetch_core_registers()}, you will need
4804 to define your own version of @code{register_addr()}, put it into your
4805 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4806 the @code{NATDEPFILES} list. If you have your own
4807 @code{fetch_core_registers()}, you may not need a separate
4808 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4809 implementations simply locate the registers themselves.@refill
4812 When making @value{GDBN} run native on a new operating system, to make it
4813 possible to debug core files, you will need to either write specific
4814 code for parsing your OS's core files, or customize
4815 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4816 machine uses to define the struct of registers that is accessible
4817 (possibly in the u-area) in a core file (rather than
4818 @file{machine/reg.h}), and an include file that defines whatever header
4819 exists on a core file (e.g., the u-area or a @code{struct core}). Then
4820 modify @code{trad_unix_core_file_p} to use these values to set up the
4821 section information for the data segment, stack segment, any other
4822 segments in the core file (perhaps shared library contents or control
4823 information), ``registers'' segment, and if there are two discontiguous
4824 sets of registers (e.g., integer and float), the ``reg2'' segment. This
4825 section information basically delimits areas in the core file in a
4826 standard way, which the section-reading routines in BFD know how to seek
4829 Then back in @value{GDBN}, you need a matching routine called
4830 @code{fetch_core_registers}. If you can use the generic one, it's in
4831 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4832 It will be passed a char pointer to the entire ``registers'' segment,
4833 its length, and a zero; or a char pointer to the entire ``regs2''
4834 segment, its length, and a 2. The routine should suck out the supplied
4835 register values and install them into @value{GDBN}'s ``registers'' array.
4837 If your system uses @file{/proc} to control processes, and uses ELF
4838 format core files, then you may be able to use the same routines for
4839 reading the registers out of processes and out of core files.
4847 @section shared libraries
4849 @section Native Conditionals
4850 @cindex native conditionals
4852 When @value{GDBN} is configured and compiled, various macros are
4853 defined or left undefined, to control compilation when the host and
4854 target systems are the same. These macros should be defined (or left
4855 undefined) in @file{nm-@var{system}.h}.
4859 @item CHILD_PREPARE_TO_STORE
4860 @findex CHILD_PREPARE_TO_STORE
4861 If the machine stores all registers at once in the child process, then
4862 define this to ensure that all values are correct. This usually entails
4863 a read from the child.
4865 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4868 @item FETCH_INFERIOR_REGISTERS
4869 @findex FETCH_INFERIOR_REGISTERS
4870 Define this if the native-dependent code will provide its own routines
4871 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4872 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4873 @file{infptrace.c} is included in this configuration, the default
4874 routines in @file{infptrace.c} are used for these functions.
4878 This macro is normally defined to be the number of the first floating
4879 point register, if the machine has such registers. As such, it would
4880 appear only in target-specific code. However, @file{/proc} support uses this
4881 to decide whether floats are in use on this target.
4883 @item GET_LONGJMP_TARGET
4884 @findex GET_LONGJMP_TARGET
4885 For most machines, this is a target-dependent parameter. On the
4886 DECstation and the Iris, this is a native-dependent parameter, since
4887 @file{setjmp.h} is needed to define it.
4889 This macro determines the target PC address that @code{longjmp} will jump to,
4890 assuming that we have just stopped at a longjmp breakpoint. It takes a
4891 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4892 pointer. It examines the current state of the machine as needed.
4894 @item I386_USE_GENERIC_WATCHPOINTS
4895 An x86-based machine can define this to use the generic x86 watchpoint
4896 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4899 @findex KERNEL_U_ADDR
4900 Define this to the address of the @code{u} structure (the ``user
4901 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4902 needs to know this so that it can subtract this address from absolute
4903 addresses in the upage, that are obtained via ptrace or from core files.
4904 On systems that don't need this value, set it to zero.
4906 @item KERNEL_U_ADDR_HPUX
4907 @findex KERNEL_U_ADDR_HPUX
4908 Define this to cause @value{GDBN} to determine the address of @code{u} at
4909 runtime, by using HP-style @code{nlist} on the kernel's image in the
4912 @item ONE_PROCESS_WRITETEXT
4913 @findex ONE_PROCESS_WRITETEXT
4914 Define this to be able to, when a breakpoint insertion fails, warn the
4915 user that another process may be running with the same executable.
4918 @findex PROC_NAME_FMT
4919 Defines the format for the name of a @file{/proc} device. Should be
4920 defined in @file{nm.h} @emph{only} in order to override the default
4921 definition in @file{procfs.c}.
4923 @item REGISTER_U_ADDR
4924 @findex REGISTER_U_ADDR
4925 Defines the offset of the registers in the ``u area''.
4927 @item SHELL_COMMAND_CONCAT
4928 @findex SHELL_COMMAND_CONCAT
4929 If defined, is a string to prefix on the shell command used to start the
4934 If defined, this is the name of the shell to use to run the inferior.
4935 Defaults to @code{"/bin/sh"}.
4937 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4939 Define this to expand into an expression that will cause the symbols in
4940 @var{filename} to be added to @value{GDBN}'s symbol table. If
4941 @var{readsyms} is zero symbols are not read but any necessary low level
4942 processing for @var{filename} is still done.
4944 @item SOLIB_CREATE_INFERIOR_HOOK
4945 @findex SOLIB_CREATE_INFERIOR_HOOK
4946 Define this to expand into any shared-library-relocation code that you
4947 want to be run just after the child process has been forked.
4949 @item START_INFERIOR_TRAPS_EXPECTED
4950 @findex START_INFERIOR_TRAPS_EXPECTED
4951 When starting an inferior, @value{GDBN} normally expects to trap
4953 the shell execs, and once when the program itself execs. If the actual
4954 number of traps is something other than 2, then define this macro to
4955 expand into the number expected.
4959 This determines whether small routines in @file{*-tdep.c}, which
4960 translate register values between @value{GDBN}'s internal
4961 representation and the @file{/proc} representation, are compiled.
4964 @findex U_REGS_OFFSET
4965 This is the offset of the registers in the upage. It need only be
4966 defined if the generic ptrace register access routines in
4967 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4968 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4969 the default value from @file{infptrace.c} is good enough, leave it
4972 The default value means that u.u_ar0 @emph{points to} the location of
4973 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4974 that @code{u.u_ar0} @emph{is} the location of the registers.
4978 See @file{objfiles.c}.
4981 @findex DEBUG_PTRACE
4982 Define this to debug @code{ptrace} calls.
4986 @node Support Libraries
4988 @chapter Support Libraries
4993 BFD provides support for @value{GDBN} in several ways:
4996 @item identifying executable and core files
4997 BFD will identify a variety of file types, including a.out, coff, and
4998 several variants thereof, as well as several kinds of core files.
5000 @item access to sections of files
5001 BFD parses the file headers to determine the names, virtual addresses,
5002 sizes, and file locations of all the various named sections in files
5003 (such as the text section or the data section). @value{GDBN} simply
5004 calls BFD to read or write section @var{x} at byte offset @var{y} for
5007 @item specialized core file support
5008 BFD provides routines to determine the failing command name stored in a
5009 core file, the signal with which the program failed, and whether a core
5010 file matches (i.e.@: could be a core dump of) a particular executable
5013 @item locating the symbol information
5014 @value{GDBN} uses an internal interface of BFD to determine where to find the
5015 symbol information in an executable file or symbol-file. @value{GDBN} itself
5016 handles the reading of symbols, since BFD does not ``understand'' debug
5017 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
5022 @cindex opcodes library
5024 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
5025 library because it's also used in binutils, for @file{objdump}).
5028 @cindex readline library
5029 The @code{readline} library provides a set of functions for use by applications
5030 that allow users to edit command lines as they are typed in.
5033 @cindex @code{libiberty} library
5035 The @code{libiberty} library provides a set of functions and features
5036 that integrate and improve on functionality found in modern operating
5037 systems. Broadly speaking, such features can be divided into three
5038 groups: supplemental functions (functions that may be missing in some
5039 environments and operating systems), replacement functions (providing
5040 a uniform and easier to use interface for commonly used standard
5041 functions), and extensions (which provide additional functionality
5042 beyond standard functions).
5044 @value{GDBN} uses various features provided by the @code{libiberty}
5045 library, for instance the C@t{++} demangler, the @acronym{IEEE}
5046 floating format support functions, the input options parser
5047 @samp{getopt}, the @samp{obstack} extension, and other functions.
5049 @subsection @code{obstacks} in @value{GDBN}
5050 @cindex @code{obstacks}
5052 The obstack mechanism provides a convenient way to allocate and free
5053 chunks of memory. Each obstack is a pool of memory that is managed
5054 like a stack. Objects (of any nature, size and alignment) are
5055 allocated and freed in a @acronym{LIFO} fashion on an obstack (see
5056 @code{libiberty}'s documentation for a more detailed explanation of
5059 The most noticeable use of the @code{obstacks} in @value{GDBN} is in
5060 object files. There is an obstack associated with each internal
5061 representation of an object file. Lots of things get allocated on
5062 these @code{obstacks}: dictionary entries, blocks, blockvectors,
5063 symbols, minimal symbols, types, vectors of fundamental types, class
5064 fields of types, object files section lists, object files section
5065 offset lists, line tables, symbol tables, partial symbol tables,
5066 string tables, symbol table private data, macros tables, debug
5067 information sections and entries, import and export lists (som),
5068 unwind information (hppa), dwarf2 location expressions data. Plus
5069 various strings such as directory names strings, debug format strings,
5072 An essential and convenient property of all data on @code{obstacks} is
5073 that memory for it gets allocated (with @code{obstack_alloc}) at
5074 various times during a debugging session, but it is released all at
5075 once using the @code{obstack_free} function. The @code{obstack_free}
5076 function takes a pointer to where in the stack it must start the
5077 deletion from (much like the cleanup chains have a pointer to where to
5078 start the cleanups). Because of the stack like structure of the
5079 @code{obstacks}, this allows to free only a top portion of the
5080 obstack. There are a few instances in @value{GDBN} where such thing
5081 happens. Calls to @code{obstack_free} are done after some local data
5082 is allocated to the obstack. Only the local data is deleted from the
5083 obstack. Of course this assumes that nothing between the
5084 @code{obstack_alloc} and the @code{obstack_free} allocates anything
5085 else on the same obstack. For this reason it is best and safest to
5086 use temporary @code{obstacks}.
5088 Releasing the whole obstack is also not safe per se. It is safe only
5089 under the condition that we know the @code{obstacks} memory is no
5090 longer needed. In @value{GDBN} we get rid of the @code{obstacks} only
5091 when we get rid of the whole objfile(s), for instance upon reading a
5095 @cindex regular expressions library
5106 @item SIGN_EXTEND_CHAR
5108 @item SWITCH_ENUM_BUG
5117 @section Array Containers
5118 @cindex Array Containers
5121 Often it is necessary to manipulate a dynamic array of a set of
5122 objects. C forces some bookkeeping on this, which can get cumbersome
5123 and repetitive. The @file{vec.h} file contains macros for defining
5124 and using a typesafe vector type. The functions defined will be
5125 inlined when compiling, and so the abstraction cost should be zero.
5126 Domain checks are added to detect programming errors.
5128 An example use would be an array of symbols or section information.
5129 The array can be grown as symbols are read in (or preallocated), and
5130 the accessor macros provided keep care of all the necessary
5131 bookkeeping. Because the arrays are type safe, there is no danger of
5132 accidentally mixing up the contents. Think of these as C++ templates,
5133 but implemented in C.
5135 Because of the different behavior of structure objects, scalar objects
5136 and of pointers, there are three flavors of vector, one for each of
5137 these variants. Both the structure object and pointer variants pass
5138 pointers to objects around --- in the former case the pointers are
5139 stored into the vector and in the latter case the pointers are
5140 dereferenced and the objects copied into the vector. The scalar
5141 object variant is suitable for @code{int}-like objects, and the vector
5142 elements are returned by value.
5144 There are both @code{index} and @code{iterate} accessors. The iterator
5145 returns a boolean iteration condition and updates the iteration
5146 variable passed by reference. Because the iterator will be inlined,
5147 the address-of can be optimized away.
5149 The vectors are implemented using the trailing array idiom, thus they
5150 are not resizeable without changing the address of the vector object
5151 itself. This means you cannot have variables or fields of vector type
5152 --- always use a pointer to a vector. The one exception is the final
5153 field of a structure, which could be a vector type. You will have to
5154 use the @code{embedded_size} & @code{embedded_init} calls to create
5155 such objects, and they will probably not be resizeable (so don't use
5156 the @dfn{safe} allocation variants). The trailing array idiom is used
5157 (rather than a pointer to an array of data), because, if we allow
5158 @code{NULL} to also represent an empty vector, empty vectors occupy
5159 minimal space in the structure containing them.
5161 Each operation that increases the number of active elements is
5162 available in @dfn{quick} and @dfn{safe} variants. The former presumes
5163 that there is sufficient allocated space for the operation to succeed
5164 (it dies if there is not). The latter will reallocate the vector, if
5165 needed. Reallocation causes an exponential increase in vector size.
5166 If you know you will be adding N elements, it would be more efficient
5167 to use the reserve operation before adding the elements with the
5168 @dfn{quick} operation. This will ensure there are at least as many
5169 elements as you ask for, it will exponentially increase if there are
5170 too few spare slots. If you want reserve a specific number of slots,
5171 but do not want the exponential increase (for instance, you know this
5172 is the last allocation), use a negative number for reservation. You
5173 can also create a vector of a specific size from the get go.
5175 You should prefer the push and pop operations, as they append and
5176 remove from the end of the vector. If you need to remove several items
5177 in one go, use the truncate operation. The insert and remove
5178 operations allow you to change elements in the middle of the vector.
5179 There are two remove operations, one which preserves the element
5180 ordering @code{ordered_remove}, and one which does not
5181 @code{unordered_remove}. The latter function copies the end element
5182 into the removed slot, rather than invoke a memmove operation. The
5183 @code{lower_bound} function will determine where to place an item in
5184 the array using insert that will maintain sorted order.
5186 If you need to directly manipulate a vector, then the @code{address}
5187 accessor will return the address of the start of the vector. Also the
5188 @code{space} predicate will tell you whether there is spare capacity in the
5189 vector. You will not normally need to use these two functions.
5191 Vector types are defined using a
5192 @code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector
5193 type are declared using a @code{VEC(@var{typename})} macro. The
5194 characters @code{O}, @code{P} and @code{I} indicate whether
5195 @var{typename} is an object (@code{O}), pointer (@code{P}) or integral
5196 (@code{I}) type. Be careful to pick the correct one, as you'll get an
5197 awkward and inefficient API if you use the wrong one. There is a
5198 check, which results in a compile-time warning, for the @code{P} and
5199 @code{I} versions, but there is no check for the @code{O} versions, as
5200 that is not possible in plain C.
5202 An example of their use would be,
5205 DEF_VEC_P(tree); // non-managed tree vector.
5208 VEC(tree) *v; // A (pointer to) a vector of tree pointers.
5211 struct my_struct *s;
5213 if (VEC_length(tree, s->v)) @{ we have some contents @}
5214 VEC_safe_push(tree, s->v, decl); // append some decl onto the end
5215 for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
5216 @{ do something with elt @}
5220 The @file{vec.h} file provides details on how to invoke the various
5221 accessors provided. They are enumerated here:
5225 Return the number of items in the array,
5228 Return true if the array has no elements.
5232 Return the last or arbitrary item in the array.
5235 Access an array element and indicate whether the array has been
5240 Create and destroy an array.
5242 @item VEC_embedded_size
5243 @itemx VEC_embedded_init
5244 Helpers for embedding an array as the final element of another struct.
5250 Return the amount of free space in an array.
5253 Ensure a certain amount of free space.
5255 @item VEC_quick_push
5256 @itemx VEC_safe_push
5257 Append to an array, either assuming the space is available, or making
5261 Remove the last item from an array.
5264 Remove several items from the end of an array.
5267 Add several items to the end of an array.
5270 Overwrite an item in the array.
5272 @item VEC_quick_insert
5273 @itemx VEC_safe_insert
5274 Insert an item into the middle of the array. Either the space must
5275 already exist, or the space is created.
5277 @item VEC_ordered_remove
5278 @itemx VEC_unordered_remove
5279 Remove an item from the array, preserving order or not.
5281 @item VEC_block_remove
5282 Remove a set of items from the array.
5285 Provide the address of the first element.
5287 @item VEC_lower_bound
5288 Binary search the array.
5298 This chapter covers topics that are lower-level than the major
5299 algorithms of @value{GDBN}.
5304 Cleanups are a structured way to deal with things that need to be done
5307 When your code does something (e.g., @code{xmalloc} some memory, or
5308 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
5309 the memory or @code{close} the file), it can make a cleanup. The
5310 cleanup will be done at some future point: when the command is finished
5311 and control returns to the top level; when an error occurs and the stack
5312 is unwound; or when your code decides it's time to explicitly perform
5313 cleanups. Alternatively you can elect to discard the cleanups you
5319 @item struct cleanup *@var{old_chain};
5320 Declare a variable which will hold a cleanup chain handle.
5322 @findex make_cleanup
5323 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
5324 Make a cleanup which will cause @var{function} to be called with
5325 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
5326 handle that can later be passed to @code{do_cleanups} or
5327 @code{discard_cleanups}. Unless you are going to call
5328 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
5329 from @code{make_cleanup}.
5332 @item do_cleanups (@var{old_chain});
5333 Do all cleanups added to the chain since the corresponding
5334 @code{make_cleanup} call was made.
5336 @findex discard_cleanups
5337 @item discard_cleanups (@var{old_chain});
5338 Same as @code{do_cleanups} except that it just removes the cleanups from
5339 the chain and does not call the specified functions.
5342 Cleanups are implemented as a chain. The handle returned by
5343 @code{make_cleanups} includes the cleanup passed to the call and any
5344 later cleanups appended to the chain (but not yet discarded or
5348 make_cleanup (a, 0);
5350 struct cleanup *old = make_cleanup (b, 0);
5358 will call @code{c()} and @code{b()} but will not call @code{a()}. The
5359 cleanup that calls @code{a()} will remain in the cleanup chain, and will
5360 be done later unless otherwise discarded.@refill
5362 Your function should explicitly do or discard the cleanups it creates.
5363 Failing to do this leads to non-deterministic behavior since the caller
5364 will arbitrarily do or discard your functions cleanups. This need leads
5365 to two common cleanup styles.
5367 The first style is try/finally. Before it exits, your code-block calls
5368 @code{do_cleanups} with the old cleanup chain and thus ensures that your
5369 code-block's cleanups are always performed. For instance, the following
5370 code-segment avoids a memory leak problem (even when @code{error} is
5371 called and a forced stack unwind occurs) by ensuring that the
5372 @code{xfree} will always be called:
5375 struct cleanup *old = make_cleanup (null_cleanup, 0);
5376 data = xmalloc (sizeof blah);
5377 make_cleanup (xfree, data);
5382 The second style is try/except. Before it exits, your code-block calls
5383 @code{discard_cleanups} with the old cleanup chain and thus ensures that
5384 any created cleanups are not performed. For instance, the following
5385 code segment, ensures that the file will be closed but only if there is
5389 FILE *file = fopen ("afile", "r");
5390 struct cleanup *old = make_cleanup (close_file, file);
5392 discard_cleanups (old);
5396 Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify
5397 that they ``should not be called when cleanups are not in place''. This
5398 means that any actions you need to reverse in the case of an error or
5399 interruption must be on the cleanup chain before you call these
5400 functions, since they might never return to your code (they
5401 @samp{longjmp} instead).
5403 @section Per-architecture module data
5404 @cindex per-architecture module data
5405 @cindex multi-arch data
5406 @cindex data-pointer, per-architecture/per-module
5408 The multi-arch framework includes a mechanism for adding module
5409 specific per-architecture data-pointers to the @code{struct gdbarch}
5410 architecture object.
5412 A module registers one or more per-architecture data-pointers using:
5414 @deftypefun struct gdbarch_data *gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init})
5415 @var{pre_init} is used to, on-demand, allocate an initial value for a
5416 per-architecture data-pointer using the architecture's obstack (passed
5417 in as a parameter). Since @var{pre_init} can be called during
5418 architecture creation, it is not parameterized with the architecture.
5419 and must not call modules that use per-architecture data.
5422 @deftypefun struct gdbarch_data *gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init})
5423 @var{post_init} is used to obtain an initial value for a
5424 per-architecture data-pointer @emph{after}. Since @var{post_init} is
5425 always called after architecture creation, it both receives the fully
5426 initialized architecture and is free to call modules that use
5427 per-architecture data (care needs to be taken to ensure that those
5428 other modules do not try to call back to this module as that will
5429 create in cycles in the initialization call graph).
5432 These functions return a @code{struct gdbarch_data} that is used to
5433 identify the per-architecture data-pointer added for that module.
5435 The per-architecture data-pointer is accessed using the function:
5437 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
5438 Given the architecture @var{arch} and module data handle
5439 @var{data_handle} (returned by @code{gdbarch_data_register_pre_init}
5440 or @code{gdbarch_data_register_post_init}), this function returns the
5441 current value of the per-architecture data-pointer. If the data
5442 pointer is @code{NULL}, it is first initialized by calling the
5443 corresponding @var{pre_init} or @var{post_init} method.
5446 The examples below assume the following definitions:
5449 struct nozel @{ int total; @};
5450 static struct gdbarch_data *nozel_handle;
5453 A module can extend the architecture vector, adding additional
5454 per-architecture data, using the @var{pre_init} method. The module's
5455 per-architecture data is then initialized during architecture
5458 In the below, the module's per-architecture @emph{nozel} is added. An
5459 architecture can specify its nozel by calling @code{set_gdbarch_nozel}
5460 from @code{gdbarch_init}.
5464 nozel_pre_init (struct obstack *obstack)
5466 struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
5473 set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
5475 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5476 data->total = nozel;
5480 A module can on-demand create architecture dependant data structures
5481 using @code{post_init}.
5483 In the below, the nozel's total is computed on-demand by
5484 @code{nozel_post_init} using information obtained from the
5489 nozel_post_init (struct gdbarch *gdbarch)
5491 struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
5492 nozel->total = gdbarch@dots{} (gdbarch);
5499 nozel_total (struct gdbarch *gdbarch)
5501 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5506 @section Wrapping Output Lines
5507 @cindex line wrap in output
5510 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
5511 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
5512 added in places that would be good breaking points. The utility
5513 routines will take care of actually wrapping if the line width is
5516 The argument to @code{wrap_here} is an indentation string which is
5517 printed @emph{only} if the line breaks there. This argument is saved
5518 away and used later. It must remain valid until the next call to
5519 @code{wrap_here} or until a newline has been printed through the
5520 @code{*_filtered} functions. Don't pass in a local variable and then
5523 It is usually best to call @code{wrap_here} after printing a comma or
5524 space. If you call it before printing a space, make sure that your
5525 indentation properly accounts for the leading space that will print if
5526 the line wraps there.
5528 Any function or set of functions that produce filtered output must
5529 finish by printing a newline, to flush the wrap buffer, before switching
5530 to unfiltered (@code{printf}) output. Symbol reading routines that
5531 print warnings are a good example.
5533 @section @value{GDBN} Coding Standards
5534 @cindex coding standards
5536 @value{GDBN} follows the GNU coding standards, as described in
5537 @file{etc/standards.texi}. This file is also available for anonymous
5538 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
5539 of the standard; in general, when the GNU standard recommends a practice
5540 but does not require it, @value{GDBN} requires it.
5542 @value{GDBN} follows an additional set of coding standards specific to
5543 @value{GDBN}, as described in the following sections.
5548 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
5551 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
5554 @subsection Memory Management
5556 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
5557 @code{calloc}, @code{free} and @code{asprintf}.
5559 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
5560 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
5561 these functions do not return when the memory pool is empty. Instead,
5562 they unwind the stack using cleanups. These functions return
5563 @code{NULL} when requested to allocate a chunk of memory of size zero.
5565 @emph{Pragmatics: By using these functions, the need to check every
5566 memory allocation is removed. These functions provide portable
5569 @value{GDBN} does not use the function @code{free}.
5571 @value{GDBN} uses the function @code{xfree} to return memory to the
5572 memory pool. Consistent with ISO-C, this function ignores a request to
5573 free a @code{NULL} pointer.
5575 @emph{Pragmatics: On some systems @code{free} fails when passed a
5576 @code{NULL} pointer.}
5578 @value{GDBN} can use the non-portable function @code{alloca} for the
5579 allocation of small temporary values (such as strings).
5581 @emph{Pragmatics: This function is very non-portable. Some systems
5582 restrict the memory being allocated to no more than a few kilobytes.}
5584 @value{GDBN} uses the string function @code{xstrdup} and the print
5585 function @code{xstrprintf}.
5587 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
5588 functions such as @code{sprintf} are very prone to buffer overflow
5592 @subsection Compiler Warnings
5593 @cindex compiler warnings
5595 With few exceptions, developers should avoid the configuration option
5596 @samp{--disable-werror} when building @value{GDBN}. The exceptions
5597 are listed in the file @file{gdb/MAINTAINERS}. The default, when
5598 building with @sc{gcc}, is @samp{--enable-werror}.
5600 This option causes @value{GDBN} (when built using GCC) to be compiled
5601 with a carefully selected list of compiler warning flags. Any warnings
5602 from those flags are treated as errors.
5604 The current list of warning flags includes:
5608 Recommended @sc{gcc} warnings.
5610 @item -Wdeclaration-after-statement
5612 @sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
5613 code, but @sc{gcc} 2.x and @sc{c89} do not.
5615 @item -Wpointer-arith
5617 @item -Wformat-nonliteral
5618 Non-literal format strings, with a few exceptions, are bugs - they
5619 might contain unintended user-supplied format specifiers.
5620 Since @value{GDBN} uses the @code{format printf} attribute on all
5621 @code{printf} like functions this checks not just @code{printf} calls
5622 but also calls to functions such as @code{fprintf_unfiltered}.
5624 @item -Wno-pointer-sign
5625 In version 4.0, GCC began warning about pointer argument passing or
5626 assignment even when the source and destination differed only in
5627 signedness. However, most @value{GDBN} code doesn't distinguish
5628 carefully between @code{char} and @code{unsigned char}. In early 2006
5629 the @value{GDBN} developers decided correcting these warnings wasn't
5630 worth the time it would take.
5632 @item -Wno-unused-parameter
5633 Due to the way that @value{GDBN} is implemented many functions have
5634 unused parameters. Consequently this warning is avoided. The macro
5635 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
5636 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
5641 These are warnings which might be useful for @value{GDBN}, but are
5642 currently too noisy to enable with @samp{-Werror}.
5646 @subsection Formatting
5648 @cindex source code formatting
5649 The standard GNU recommendations for formatting must be followed
5652 A function declaration should not have its name in column zero. A
5653 function definition should have its name in column zero.
5657 static void foo (void);
5665 @emph{Pragmatics: This simplifies scripting. Function definitions can
5666 be found using @samp{^function-name}.}
5668 There must be a space between a function or macro name and the opening
5669 parenthesis of its argument list (except for macro definitions, as
5670 required by C). There must not be a space after an open paren/bracket
5671 or before a close paren/bracket.
5673 While additional whitespace is generally helpful for reading, do not use
5674 more than one blank line to separate blocks, and avoid adding whitespace
5675 after the end of a program line (as of 1/99, some 600 lines had
5676 whitespace after the semicolon). Excess whitespace causes difficulties
5677 for @code{diff} and @code{patch} utilities.
5679 Pointers are declared using the traditional K&R C style:
5693 @subsection Comments
5695 @cindex comment formatting
5696 The standard GNU requirements on comments must be followed strictly.
5698 Block comments must appear in the following form, with no @code{/*}- or
5699 @code{*/}-only lines, and no leading @code{*}:
5702 /* Wait for control to return from inferior to debugger. If inferior
5703 gets a signal, we may decide to start it up again instead of
5704 returning. That is why there is a loop in this function. When
5705 this function actually returns it means the inferior should be left
5706 stopped and @value{GDBN} should read more commands. */
5709 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5710 comment works correctly, and @kbd{M-q} fills the block consistently.)
5712 Put a blank line between the block comments preceding function or
5713 variable definitions, and the definition itself.
5715 In general, put function-body comments on lines by themselves, rather
5716 than trying to fit them into the 20 characters left at the end of a
5717 line, since either the comment or the code will inevitably get longer
5718 than will fit, and then somebody will have to move it anyhow.
5722 @cindex C data types
5723 Code must not depend on the sizes of C data types, the format of the
5724 host's floating point numbers, the alignment of anything, or the order
5725 of evaluation of expressions.
5727 @cindex function usage
5728 Use functions freely. There are only a handful of compute-bound areas
5729 in @value{GDBN} that might be affected by the overhead of a function
5730 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5731 limited by the target interface (whether serial line or system call).
5733 However, use functions with moderation. A thousand one-line functions
5734 are just as hard to understand as a single thousand-line function.
5736 @emph{Macros are bad, M'kay.}
5737 (But if you have to use a macro, make sure that the macro arguments are
5738 protected with parentheses.)
5742 Declarations like @samp{struct foo *} should be used in preference to
5743 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5746 @subsection Function Prototypes
5747 @cindex function prototypes
5749 Prototypes must be used when both @emph{declaring} and @emph{defining}
5750 a function. Prototypes for @value{GDBN} functions must include both the
5751 argument type and name, with the name matching that used in the actual
5752 function definition.
5754 All external functions should have a declaration in a header file that
5755 callers include, except for @code{_initialize_*} functions, which must
5756 be external so that @file{init.c} construction works, but shouldn't be
5757 visible to random source files.
5759 Where a source file needs a forward declaration of a static function,
5760 that declaration must appear in a block near the top of the source file.
5763 @subsection Internal Error Recovery
5765 During its execution, @value{GDBN} can encounter two types of errors.
5766 User errors and internal errors. User errors include not only a user
5767 entering an incorrect command but also problems arising from corrupt
5768 object files and system errors when interacting with the target.
5769 Internal errors include situations where @value{GDBN} has detected, at
5770 run time, a corrupt or erroneous situation.
5772 When reporting an internal error, @value{GDBN} uses
5773 @code{internal_error} and @code{gdb_assert}.
5775 @value{GDBN} must not call @code{abort} or @code{assert}.
5777 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5778 the code detected a user error, recovered from it and issued a
5779 @code{warning} or the code failed to correctly recover from the user
5780 error and issued an @code{internal_error}.}
5782 @subsection File Names
5784 Any file used when building the core of @value{GDBN} must be in lower
5785 case. Any file used when building the core of @value{GDBN} must be 8.3
5786 unique. These requirements apply to both source and generated files.
5788 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5789 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5790 is introduced to the build process both @file{Makefile.in} and
5791 @file{configure.in} need to be modified accordingly. Compare the
5792 convoluted conversion process needed to transform @file{COPYING} into
5793 @file{copying.c} with the conversion needed to transform
5794 @file{version.in} into @file{version.c}.}
5796 Any file non 8.3 compliant file (that is not used when building the core
5797 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5799 @emph{Pragmatics: This is clearly a compromise.}
5801 When @value{GDBN} has a local version of a system header file (ex
5802 @file{string.h}) the file name based on the POSIX header prefixed with
5803 @file{gdb_} (@file{gdb_string.h}). These headers should be relatively
5804 independent: they should use only macros defined by @file{configure},
5805 the compiler, or the host; they should include only system headers; they
5806 should refer only to system types. They may be shared between multiple
5807 programs, e.g.@: @value{GDBN} and @sc{gdbserver}.
5809 For other files @samp{-} is used as the separator.
5812 @subsection Include Files
5814 A @file{.c} file should include @file{defs.h} first.
5816 A @file{.c} file should directly include the @code{.h} file of every
5817 declaration and/or definition it directly refers to. It cannot rely on
5820 A @file{.h} file should directly include the @code{.h} file of every
5821 declaration and/or definition it directly refers to. It cannot rely on
5822 indirect inclusion. Exception: The file @file{defs.h} does not need to
5823 be directly included.
5825 An external declaration should only appear in one include file.
5827 An external declaration should never appear in a @code{.c} file.
5828 Exception: a declaration for the @code{_initialize} function that
5829 pacifies @option{-Wmissing-declaration}.
5831 A @code{typedef} definition should only appear in one include file.
5833 An opaque @code{struct} declaration can appear in multiple @file{.h}
5834 files. Where possible, a @file{.h} file should use an opaque
5835 @code{struct} declaration instead of an include.
5837 All @file{.h} files should be wrapped in:
5840 #ifndef INCLUDE_FILE_NAME_H
5841 #define INCLUDE_FILE_NAME_H
5847 @subsection Clean Design and Portable Implementation
5850 In addition to getting the syntax right, there's the little question of
5851 semantics. Some things are done in certain ways in @value{GDBN} because long
5852 experience has shown that the more obvious ways caused various kinds of
5855 @cindex assumptions about targets
5856 You can't assume the byte order of anything that comes from a target
5857 (including @var{value}s, object files, and instructions). Such things
5858 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5859 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5860 such as @code{bfd_get_32}.
5862 You can't assume that you know what interface is being used to talk to
5863 the target system. All references to the target must go through the
5864 current @code{target_ops} vector.
5866 You can't assume that the host and target machines are the same machine
5867 (except in the ``native'' support modules). In particular, you can't
5868 assume that the target machine's header files will be available on the
5869 host machine. Target code must bring along its own header files --
5870 written from scratch or explicitly donated by their owner, to avoid
5874 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5875 to write the code portably than to conditionalize it for various
5878 @cindex system dependencies
5879 New @code{#ifdef}'s which test for specific compilers or manufacturers
5880 or operating systems are unacceptable. All @code{#ifdef}'s should test
5881 for features. The information about which configurations contain which
5882 features should be segregated into the configuration files. Experience
5883 has proven far too often that a feature unique to one particular system
5884 often creeps into other systems; and that a conditional based on some
5885 predefined macro for your current system will become worthless over
5886 time, as new versions of your system come out that behave differently
5887 with regard to this feature.
5889 Adding code that handles specific architectures, operating systems,
5890 target interfaces, or hosts, is not acceptable in generic code.
5892 @cindex portable file name handling
5893 @cindex file names, portability
5894 One particularly notorious area where system dependencies tend to
5895 creep in is handling of file names. The mainline @value{GDBN} code
5896 assumes Posix semantics of file names: absolute file names begin with
5897 a forward slash @file{/}, slashes are used to separate leading
5898 directories, case-sensitive file names. These assumptions are not
5899 necessarily true on non-Posix systems such as MS-Windows. To avoid
5900 system-dependent code where you need to take apart or construct a file
5901 name, use the following portable macros:
5904 @findex HAVE_DOS_BASED_FILE_SYSTEM
5905 @item HAVE_DOS_BASED_FILE_SYSTEM
5906 This preprocessing symbol is defined to a non-zero value on hosts
5907 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5908 symbol to write conditional code which should only be compiled for
5911 @findex IS_DIR_SEPARATOR
5912 @item IS_DIR_SEPARATOR (@var{c})
5913 Evaluates to a non-zero value if @var{c} is a directory separator
5914 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5915 such a character, but on Windows, both @file{/} and @file{\} will
5918 @findex IS_ABSOLUTE_PATH
5919 @item IS_ABSOLUTE_PATH (@var{file})
5920 Evaluates to a non-zero value if @var{file} is an absolute file name.
5921 For Unix and GNU/Linux hosts, a name which begins with a slash
5922 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5923 @file{x:\bar} are also absolute file names.
5925 @findex FILENAME_CMP
5926 @item FILENAME_CMP (@var{f1}, @var{f2})
5927 Calls a function which compares file names @var{f1} and @var{f2} as
5928 appropriate for the underlying host filesystem. For Posix systems,
5929 this simply calls @code{strcmp}; on case-insensitive filesystems it
5930 will call @code{strcasecmp} instead.
5932 @findex DIRNAME_SEPARATOR
5933 @item DIRNAME_SEPARATOR
5934 Evaluates to a character which separates directories in
5935 @code{PATH}-style lists, typically held in environment variables.
5936 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5938 @findex SLASH_STRING
5940 This evaluates to a constant string you should use to produce an
5941 absolute filename from leading directories and the file's basename.
5942 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5943 @code{"\\"} for some Windows-based ports.
5946 In addition to using these macros, be sure to use portable library
5947 functions whenever possible. For example, to extract a directory or a
5948 basename part from a file name, use the @code{dirname} and
5949 @code{basename} library functions (available in @code{libiberty} for
5950 platforms which don't provide them), instead of searching for a slash
5951 with @code{strrchr}.
5953 Another way to generalize @value{GDBN} along a particular interface is with an
5954 attribute struct. For example, @value{GDBN} has been generalized to handle
5955 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5956 by defining the @code{target_ops} structure and having a current target (as
5957 well as a stack of targets below it, for memory references). Whenever
5958 something needs to be done that depends on which remote interface we are
5959 using, a flag in the current target_ops structure is tested (e.g.,
5960 @code{target_has_stack}), or a function is called through a pointer in the
5961 current target_ops structure. In this way, when a new remote interface
5962 is added, only one module needs to be touched---the one that actually
5963 implements the new remote interface. Other examples of
5964 attribute-structs are BFD access to multiple kinds of object file
5965 formats, or @value{GDBN}'s access to multiple source languages.
5967 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5968 the code interfacing between @code{ptrace} and the rest of
5969 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5970 something was very painful. In @value{GDBN} 4.x, these have all been
5971 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5972 with variations between systems the same way any system-independent
5973 file would (hooks, @code{#if defined}, etc.), and machines which are
5974 radically different don't need to use @file{infptrace.c} at all.
5976 All debugging code must be controllable using the @samp{set debug
5977 @var{module}} command. Do not use @code{printf} to print trace
5978 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5979 @code{#ifdef DEBUG}.
5984 @chapter Porting @value{GDBN}
5985 @cindex porting to new machines
5987 Most of the work in making @value{GDBN} compile on a new machine is in
5988 specifying the configuration of the machine. This is done in a
5989 dizzying variety of header files and configuration scripts, which we
5990 hope to make more sensible soon. Let's say your new host is called an
5991 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
5992 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
5993 @samp{sparc-sun-sunos4}). In particular:
5997 In the top level directory, edit @file{config.sub} and add @var{arch},
5998 @var{xvend}, and @var{xos} to the lists of supported architectures,
5999 vendors, and operating systems near the bottom of the file. Also, add
6000 @var{xyz} as an alias that maps to
6001 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
6005 ./config.sub @var{xyz}
6012 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
6016 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
6017 and no error messages.
6020 You need to port BFD, if that hasn't been done already. Porting BFD is
6021 beyond the scope of this manual.
6024 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
6025 your system and set @code{gdb_host} to @var{xyz}, and (unless your
6026 desired target is already available) also edit @file{gdb/configure.tgt},
6027 setting @code{gdb_target} to something appropriate (for instance,
6030 @emph{Maintainer's note: Work in progress. The file
6031 @file{gdb/configure.host} originally needed to be modified when either a
6032 new native target or a new host machine was being added to @value{GDBN}.
6033 Recent changes have removed this requirement. The file now only needs
6034 to be modified when adding a new native configuration. This will likely
6035 changed again in the future.}
6038 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
6039 target-dependent @file{.h} and @file{.c} files used for your
6043 @node Versions and Branches
6044 @chapter Versions and Branches
6048 @value{GDBN}'s version is determined by the file
6049 @file{gdb/version.in} and takes one of the following forms:
6052 @item @var{major}.@var{minor}
6053 @itemx @var{major}.@var{minor}.@var{patchlevel}
6054 an official release (e.g., 6.2 or 6.2.1)
6055 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}
6056 a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g.,
6057 6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308)
6058 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs
6059 a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g.,
6060 6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
6061 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor})
6062 a vendor specific release of @value{GDBN}, that while based on@*
6063 @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD},
6064 may include additional changes
6067 @value{GDBN}'s mainline uses the @var{major} and @var{minor} version
6068 numbers from the most recent release branch, with a @var{patchlevel}
6069 of 50. At the time each new release branch is created, the mainline's
6070 @var{major} and @var{minor} version numbers are updated.
6072 @value{GDBN}'s release branch is similar. When the branch is cut, the
6073 @var{patchlevel} is changed from 50 to 90. As draft releases are
6074 drawn from the branch, the @var{patchlevel} is incremented. Once the
6075 first release (@var{major}.@var{minor}) has been made, the
6076 @var{patchlevel} is set to 0 and updates have an incremented
6079 For snapshots, and @sc{cvs} check outs, it is also possible to
6080 identify the @sc{cvs} origin:
6083 @item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD}
6084 drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302)
6085 @item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD}
6086 @itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{}
6087 drawn from a release branch prior to the release (e.g.,
6089 @item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD}
6090 @itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{}
6091 drawn from a release branch after the release (e.g., 6.2.0.20020308)
6094 If the previous @value{GDBN} version is 6.1 and the current version is
6095 6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor},
6096 here's an illustration of a typical sequence:
6103 +--------------------------.
6106 6.2.50.20020303-cvs 6.1.90 (draft #1)
6108 6.2.50.20020304-cvs 6.1.90.20020304-cvs
6110 6.2.50.20020305-cvs 6.1.91 (draft #2)
6112 6.2.50.20020306-cvs 6.1.91.20020306-cvs
6114 6.2.50.20020307-cvs 6.2 (release)
6116 6.2.50.20020308-cvs 6.2.0.20020308-cvs
6118 6.2.50.20020309-cvs 6.2.1 (update)
6120 6.2.50.20020310-cvs <branch closed>
6124 +--------------------------.
6127 6.3.50.20020312-cvs 6.2.90 (draft #1)
6131 @section Release Branches
6132 @cindex Release Branches
6134 @value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a
6135 single release branch, and identifies that branch using the @sc{cvs}
6139 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint
6140 gdb_@var{major}_@var{minor}-branch
6141 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release
6144 @emph{Pragmatics: To help identify the date at which a branch or
6145 release is made, both the branchpoint and release tags include the
6146 date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The
6147 branch tag, denoting the head of the branch, does not need this.}
6149 @section Vendor Branches
6150 @cindex vendor branches
6152 To avoid version conflicts, vendors are expected to modify the file
6153 @file{gdb/version.in} to include a vendor unique alphabetic identifier
6154 (an official @value{GDBN} release never uses alphabetic characters in
6155 its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit
6158 @section Experimental Branches
6159 @cindex experimental branches
6161 @subsection Guidelines
6163 @value{GDBN} permits the creation of branches, cut from the @sc{cvs}
6164 repository, for experimental development. Branches make it possible
6165 for developers to share preliminary work, and maintainers to examine
6166 significant new developments.
6168 The following are a set of guidelines for creating such branches:
6172 @item a branch has an owner
6173 The owner can set further policy for a branch, but may not change the
6174 ground rules. In particular, they can set a policy for commits (be it
6175 adding more reviewers or deciding who can commit).
6177 @item all commits are posted
6178 All changes committed to a branch shall also be posted to
6179 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} patches
6180 mailing list}. While commentary on such changes are encouraged, people
6181 should remember that the changes only apply to a branch.
6183 @item all commits are covered by an assignment
6184 This ensures that all changes belong to the Free Software Foundation,
6185 and avoids the possibility that the branch may become contaminated.
6187 @item a branch is focused
6188 A focused branch has a single objective or goal, and does not contain
6189 unnecessary or irrelevant changes. Cleanups, where identified, being
6190 be pushed into the mainline as soon as possible.
6192 @item a branch tracks mainline
6193 This keeps the level of divergence under control. It also keeps the
6194 pressure on developers to push cleanups and other stuff into the
6197 @item a branch shall contain the entire @value{GDBN} module
6198 The @value{GDBN} module @code{gdb} should be specified when creating a
6199 branch (branches of individual files should be avoided). @xref{Tags}.
6201 @item a branch shall be branded using @file{version.in}
6202 The file @file{gdb/version.in} shall be modified so that it identifies
6203 the branch @var{owner} and branch @var{name}, e.g.,
6204 @samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}.
6211 To simplify the identification of @value{GDBN} branches, the following
6212 branch tagging convention is strongly recommended:
6216 @item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6217 @itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch
6218 The branch point and corresponding branch tag. @var{YYYYMMDD} is the
6219 date that the branch was created. A branch is created using the
6220 sequence: @anchor{experimental branch tags}
6222 cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb
6223 cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \
6224 @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb
6227 @item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6228 The tagged point, on the mainline, that was used when merging the branch
6229 on @var{yyyymmdd}. To merge in all changes since the branch was cut,
6230 use a command sequence like:
6232 cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb
6234 -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6235 -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6238 Similar sequences can be used to just merge in changes since the last
6244 For further information on @sc{cvs}, see
6245 @uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}.
6247 @node Start of New Year Procedure
6248 @chapter Start of New Year Procedure
6249 @cindex new year procedure
6251 At the start of each new year, the following actions should be performed:
6255 Rotate the ChangeLog file
6257 The current @file{ChangeLog} file should be renamed into
6258 @file{ChangeLog-YYYY} where YYYY is the year that has just passed.
6259 A new @file{ChangeLog} file should be created, and its contents should
6260 contain a reference to the previous ChangeLog. The following should
6261 also be preserved at the end of the new ChangeLog, in order to provide
6262 the appropriate settings when editing this file with Emacs:
6268 version-control: never
6273 Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY})
6274 in @file{gdb/config/djgpp/fnchange.lst}.
6277 Update the copyright year in the startup message
6279 Update the copyright year in file @file{top.c}, function
6280 @code{print_gdb_version}.
6285 @chapter Releasing @value{GDBN}
6286 @cindex making a new release of gdb
6288 @section Branch Commit Policy
6290 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
6291 5.1 and 5.2 all used the below:
6295 The @file{gdb/MAINTAINERS} file still holds.
6297 Don't fix something on the branch unless/until it is also fixed in the
6298 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
6299 file is better than committing a hack.
6301 When considering a patch for the branch, suggested criteria include:
6302 Does it fix a build? Does it fix the sequence @kbd{break main; run}
6303 when debugging a static binary?
6305 The further a change is from the core of @value{GDBN}, the less likely
6306 the change will worry anyone (e.g., target specific code).
6308 Only post a proposal to change the core of @value{GDBN} after you've
6309 sent individual bribes to all the people listed in the
6310 @file{MAINTAINERS} file @t{;-)}
6313 @emph{Pragmatics: Provided updates are restricted to non-core
6314 functionality there is little chance that a broken change will be fatal.
6315 This means that changes such as adding a new architectures or (within
6316 reason) support for a new host are considered acceptable.}
6319 @section Obsoleting code
6321 Before anything else, poke the other developers (and around the source
6322 code) to see if there is anything that can be removed from @value{GDBN}
6323 (an old target, an unused file).
6325 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
6326 line. Doing this means that it is easy to identify something that has
6327 been obsoleted when greping through the sources.
6329 The process is done in stages --- this is mainly to ensure that the
6330 wider @value{GDBN} community has a reasonable opportunity to respond.
6331 Remember, everything on the Internet takes a week.
6335 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
6336 list} Creating a bug report to track the task's state, is also highly
6341 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
6342 Announcement mailing list}.
6346 Go through and edit all relevant files and lines so that they are
6347 prefixed with the word @code{OBSOLETE}.
6349 Wait until the next GDB version, containing this obsolete code, has been
6352 Remove the obsolete code.
6356 @emph{Maintainer note: While removing old code is regrettable it is
6357 hopefully better for @value{GDBN}'s long term development. Firstly it
6358 helps the developers by removing code that is either no longer relevant
6359 or simply wrong. Secondly since it removes any history associated with
6360 the file (effectively clearing the slate) the developer has a much freer
6361 hand when it comes to fixing broken files.}
6365 @section Before the Branch
6367 The most important objective at this stage is to find and fix simple
6368 changes that become a pain to track once the branch is created. For
6369 instance, configuration problems that stop @value{GDBN} from even
6370 building. If you can't get the problem fixed, document it in the
6371 @file{gdb/PROBLEMS} file.
6373 @subheading Prompt for @file{gdb/NEWS}
6375 People always forget. Send a post reminding them but also if you know
6376 something interesting happened add it yourself. The @code{schedule}
6377 script will mention this in its e-mail.
6379 @subheading Review @file{gdb/README}
6381 Grab one of the nightly snapshots and then walk through the
6382 @file{gdb/README} looking for anything that can be improved. The
6383 @code{schedule} script will mention this in its e-mail.
6385 @subheading Refresh any imported files.
6387 A number of files are taken from external repositories. They include:
6391 @file{texinfo/texinfo.tex}
6393 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
6396 @file{etc/standards.texi}, @file{etc/make-stds.texi}
6399 @subheading Check the ARI
6401 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
6402 (Awk Regression Index ;-) that checks for a number of errors and coding
6403 conventions. The checks include things like using @code{malloc} instead
6404 of @code{xmalloc} and file naming problems. There shouldn't be any
6407 @subsection Review the bug data base
6409 Close anything obviously fixed.
6411 @subsection Check all cross targets build
6413 The targets are listed in @file{gdb/MAINTAINERS}.
6416 @section Cut the Branch
6418 @subheading Create the branch
6423 $ V=`echo $v | sed 's/\./_/g'`
6424 $ D=`date -u +%Y-%m-%d`
6427 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6428 -D $D-gmt gdb_$V-$D-branchpoint insight
6429 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
6430 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight
6433 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6434 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
6435 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6436 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
6444 By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact
6447 The trunk is first tagged so that the branch point can easily be found.
6449 Insight, which includes @value{GDBN}, is tagged at the same time.
6451 @file{version.in} gets bumped to avoid version number conflicts.
6453 The reading of @file{.cvsrc} is disabled using @file{-f}.
6456 @subheading Update @file{version.in}
6461 $ V=`echo $v | sed 's/\./_/g'`
6465 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
6466 -r gdb_$V-branch src/gdb/version.in
6467 cvs -f -d :ext:sources.redhat.com:/cvs/src co
6468 -r gdb_5_2-branch src/gdb/version.in
6470 U src/gdb/version.in
6472 $ echo $u.90-0000-00-00-cvs > version.in
6474 5.1.90-0000-00-00-cvs
6475 $ cvs -f commit version.in
6480 @file{0000-00-00} is used as a date to pump prime the version.in update
6483 @file{.90} and the previous branch version are used as fairly arbitrary
6484 initial branch version number.
6488 @subheading Update the web and news pages
6492 @subheading Tweak cron to track the new branch
6494 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
6495 This file needs to be updated so that:
6499 A daily timestamp is added to the file @file{version.in}.
6501 The new branch is included in the snapshot process.
6505 See the file @file{gdbadmin/cron/README} for how to install the updated
6508 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
6509 any changes. That file is copied to both the branch/ and current/
6510 snapshot directories.
6513 @subheading Update the NEWS and README files
6515 The @file{NEWS} file needs to be updated so that on the branch it refers
6516 to @emph{changes in the current release} while on the trunk it also
6517 refers to @emph{changes since the current release}.
6519 The @file{README} file needs to be updated so that it refers to the
6522 @subheading Post the branch info
6524 Send an announcement to the mailing lists:
6528 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6530 @email{gdb@@sources.redhat.com, GDB Discussion mailing list} and
6531 @email{gdb-testers@@sources.redhat.com, GDB Testers mailing list}
6534 @emph{Pragmatics: The branch creation is sent to the announce list to
6535 ensure that people people not subscribed to the higher volume discussion
6538 The announcement should include:
6544 How to check out the branch using CVS.
6546 The date/number of weeks until the release.
6548 The branch commit policy still holds.
6551 @section Stabilize the branch
6553 Something goes here.
6555 @section Create a Release
6557 The process of creating and then making available a release is broken
6558 down into a number of stages. The first part addresses the technical
6559 process of creating a releasable tar ball. The later stages address the
6560 process of releasing that tar ball.
6562 When making a release candidate just the first section is needed.
6564 @subsection Create a release candidate
6566 The objective at this stage is to create a set of tar balls that can be
6567 made available as a formal release (or as a less formal release
6570 @subsubheading Freeze the branch
6572 Send out an e-mail notifying everyone that the branch is frozen to
6573 @email{gdb-patches@@sources.redhat.com}.
6575 @subsubheading Establish a few defaults.
6580 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
6582 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6586 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6588 /home/gdbadmin/bin/autoconf
6597 Check the @code{autoconf} version carefully. You want to be using the
6598 version taken from the @file{binutils} snapshot directory, which can be
6599 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
6600 unlikely that a system installed version of @code{autoconf} (e.g.,
6601 @file{/usr/bin/autoconf}) is correct.
6604 @subsubheading Check out the relevant modules:
6607 $ for m in gdb insight
6609 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
6619 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
6620 any confusion between what is written here and what your local
6621 @code{cvs} really does.
6624 @subsubheading Update relevant files.
6630 Major releases get their comments added as part of the mainline. Minor
6631 releases should probably mention any significant bugs that were fixed.
6633 Don't forget to include the @file{ChangeLog} entry.
6636 $ emacs gdb/src/gdb/NEWS
6641 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
6642 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6647 You'll need to update:
6659 $ emacs gdb/src/gdb/README
6664 $ cp gdb/src/gdb/README insight/src/gdb/README
6665 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6668 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
6669 before the initial branch was cut so just a simple substitute is needed
6672 @emph{Maintainer note: Other projects generate @file{README} and
6673 @file{INSTALL} from the core documentation. This might be worth
6676 @item gdb/version.in
6679 $ echo $v > gdb/src/gdb/version.in
6680 $ cat gdb/src/gdb/version.in
6682 $ emacs gdb/src/gdb/version.in
6685 ... Bump to version ...
6687 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
6688 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6693 @subsubheading Do the dirty work
6695 This is identical to the process used to create the daily snapshot.
6698 $ for m in gdb insight
6700 ( cd $m/src && gmake -f src-release $m.tar )
6704 If the top level source directory does not have @file{src-release}
6705 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
6708 $ for m in gdb insight
6710 ( cd $m/src && gmake -f Makefile.in $m.tar )
6714 @subsubheading Check the source files
6716 You're looking for files that have mysteriously disappeared.
6717 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
6718 for the @file{version.in} update @kbd{cronjob}.
6721 $ ( cd gdb/src && cvs -f -q -n update )
6725 @dots{} lots of generated files @dots{}
6730 @dots{} lots of generated files @dots{}
6735 @emph{Don't worry about the @file{gdb.info-??} or
6736 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
6737 was also generated only something strange with CVS means that they
6738 didn't get suppressed). Fixing it would be nice though.}
6740 @subsubheading Create compressed versions of the release
6746 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
6747 $ for m in gdb insight
6749 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
6750 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
6760 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
6761 in that mode, @code{gzip} does not know the name of the file and, hence,
6762 can not include it in the compressed file. This is also why the release
6763 process runs @code{tar} and @code{bzip2} as separate passes.
6766 @subsection Sanity check the tar ball
6768 Pick a popular machine (Solaris/PPC?) and try the build on that.
6771 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
6776 $ ./gdb/gdb ./gdb/gdb
6780 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6782 Starting program: /tmp/gdb-5.2/gdb/gdb
6784 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6785 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6787 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6791 @subsection Make a release candidate available
6793 If this is a release candidate then the only remaining steps are:
6797 Commit @file{version.in} and @file{ChangeLog}
6799 Tweak @file{version.in} (and @file{ChangeLog} to read
6800 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6801 process can restart.
6803 Make the release candidate available in
6804 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6806 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6807 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6810 @subsection Make a formal release available
6812 (And you thought all that was required was to post an e-mail.)
6814 @subsubheading Install on sware
6816 Copy the new files to both the release and the old release directory:
6819 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6820 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6824 Clean up the releases directory so that only the most recent releases
6825 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6828 $ cd ~ftp/pub/gdb/releases
6833 Update the file @file{README} and @file{.message} in the releases
6840 $ ln README .message
6843 @subsubheading Update the web pages.
6847 @item htdocs/download/ANNOUNCEMENT
6848 This file, which is posted as the official announcement, includes:
6851 General announcement.
6853 News. If making an @var{M}.@var{N}.1 release, retain the news from
6854 earlier @var{M}.@var{N} release.
6859 @item htdocs/index.html
6860 @itemx htdocs/news/index.html
6861 @itemx htdocs/download/index.html
6862 These files include:
6865 Announcement of the most recent release.
6867 News entry (remember to update both the top level and the news directory).
6869 These pages also need to be regenerate using @code{index.sh}.
6871 @item download/onlinedocs/
6872 You need to find the magic command that is used to generate the online
6873 docs from the @file{.tar.bz2}. The best way is to look in the output
6874 from one of the nightly @code{cron} jobs and then just edit accordingly.
6878 $ ~/ss/update-web-docs \
6879 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6881 /www/sourceware/htdocs/gdb/download/onlinedocs \
6886 Just like the online documentation. Something like:
6889 $ /bin/sh ~/ss/update-web-ari \
6890 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6892 /www/sourceware/htdocs/gdb/download/ari \
6898 @subsubheading Shadow the pages onto gnu
6900 Something goes here.
6903 @subsubheading Install the @value{GDBN} tar ball on GNU
6905 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6906 @file{~ftp/gnu/gdb}.
6908 @subsubheading Make the @file{ANNOUNCEMENT}
6910 Post the @file{ANNOUNCEMENT} file you created above to:
6914 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6916 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6917 day or so to let things get out)
6919 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6924 The release is out but you're still not finished.
6926 @subsubheading Commit outstanding changes
6928 In particular you'll need to commit any changes to:
6932 @file{gdb/ChangeLog}
6934 @file{gdb/version.in}
6941 @subsubheading Tag the release
6946 $ d=`date -u +%Y-%m-%d`
6949 $ ( cd insight/src/gdb && cvs -f -q update )
6950 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6953 Insight is used since that contains more of the release than
6956 @subsubheading Mention the release on the trunk
6958 Just put something in the @file{ChangeLog} so that the trunk also
6959 indicates when the release was made.
6961 @subsubheading Restart @file{gdb/version.in}
6963 If @file{gdb/version.in} does not contain an ISO date such as
6964 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6965 committed all the release changes it can be set to
6966 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6967 is important - it affects the snapshot process).
6969 Don't forget the @file{ChangeLog}.
6971 @subsubheading Merge into trunk
6973 The files committed to the branch may also need changes merged into the
6976 @subsubheading Revise the release schedule
6978 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
6979 Discussion List} with an updated announcement. The schedule can be
6980 generated by running:
6983 $ ~/ss/schedule `date +%s` schedule
6987 The first parameter is approximate date/time in seconds (from the epoch)
6988 of the most recent release.
6990 Also update the schedule @code{cronjob}.
6992 @section Post release
6994 Remove any @code{OBSOLETE} code.
7001 The testsuite is an important component of the @value{GDBN} package.
7002 While it is always worthwhile to encourage user testing, in practice
7003 this is rarely sufficient; users typically use only a small subset of
7004 the available commands, and it has proven all too common for a change
7005 to cause a significant regression that went unnoticed for some time.
7007 The @value{GDBN} testsuite uses the DejaGNU testing framework. The
7008 tests themselves are calls to various @code{Tcl} procs; the framework
7009 runs all the procs and summarizes the passes and fails.
7011 @section Using the Testsuite
7013 @cindex running the test suite
7014 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
7015 testsuite's objdir) and type @code{make check}. This just sets up some
7016 environment variables and invokes DejaGNU's @code{runtest} script. While
7017 the testsuite is running, you'll get mentions of which test file is in use,
7018 and a mention of any unexpected passes or fails. When the testsuite is
7019 finished, you'll get a summary that looks like this:
7024 # of expected passes 6016
7025 # of unexpected failures 58
7026 # of unexpected successes 5
7027 # of expected failures 183
7028 # of unresolved testcases 3
7029 # of untested testcases 5
7032 To run a specific test script, type:
7034 make check RUNTESTFLAGS='@var{tests}'
7036 where @var{tests} is a list of test script file names, separated by
7039 The ideal test run consists of expected passes only; however, reality
7040 conspires to keep us from this ideal. Unexpected failures indicate
7041 real problems, whether in @value{GDBN} or in the testsuite. Expected
7042 failures are still failures, but ones which have been decided are too
7043 hard to deal with at the time; for instance, a test case might work
7044 everywhere except on AIX, and there is no prospect of the AIX case
7045 being fixed in the near future. Expected failures should not be added
7046 lightly, since you may be masking serious bugs in @value{GDBN}.
7047 Unexpected successes are expected fails that are passing for some
7048 reason, while unresolved and untested cases often indicate some minor
7049 catastrophe, such as the compiler being unable to deal with a test
7052 When making any significant change to @value{GDBN}, you should run the
7053 testsuite before and after the change, to confirm that there are no
7054 regressions. Note that truly complete testing would require that you
7055 run the testsuite with all supported configurations and a variety of
7056 compilers; however this is more than really necessary. In many cases
7057 testing with a single configuration is sufficient. Other useful
7058 options are to test one big-endian (Sparc) and one little-endian (x86)
7059 host, a cross config with a builtin simulator (powerpc-eabi,
7060 mips-elf), or a 64-bit host (Alpha).
7062 If you add new functionality to @value{GDBN}, please consider adding
7063 tests for it as well; this way future @value{GDBN} hackers can detect
7064 and fix their changes that break the functionality you added.
7065 Similarly, if you fix a bug that was not previously reported as a test
7066 failure, please add a test case for it. Some cases are extremely
7067 difficult to test, such as code that handles host OS failures or bugs
7068 in particular versions of compilers, and it's OK not to try to write
7069 tests for all of those.
7071 DejaGNU supports separate build, host, and target machines. However,
7072 some @value{GDBN} test scripts do not work if the build machine and
7073 the host machine are not the same. In such an environment, these scripts
7074 will give a result of ``UNRESOLVED'', like this:
7077 UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
7080 @section Testsuite Organization
7082 @cindex test suite organization
7083 The testsuite is entirely contained in @file{gdb/testsuite}. While the
7084 testsuite includes some makefiles and configury, these are very minimal,
7085 and used for little besides cleaning up, since the tests themselves
7086 handle the compilation of the programs that @value{GDBN} will run. The file
7087 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
7088 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
7089 configuration-specific files, typically used for special-purpose
7090 definitions of procs like @code{gdb_load} and @code{gdb_start}.
7092 The tests themselves are to be found in @file{testsuite/gdb.*} and
7093 subdirectories of those. The names of the test files must always end
7094 with @file{.exp}. DejaGNU collects the test files by wildcarding
7095 in the test directories, so both subdirectories and individual files
7096 get chosen and run in alphabetical order.
7098 The following table lists the main types of subdirectories and what they
7099 are for. Since DejaGNU finds test files no matter where they are
7100 located, and since each test file sets up its own compilation and
7101 execution environment, this organization is simply for convenience and
7106 This is the base testsuite. The tests in it should apply to all
7107 configurations of @value{GDBN} (but generic native-only tests may live here).
7108 The test programs should be in the subset of C that is valid K&R,
7109 ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance
7112 @item gdb.@var{lang}
7113 Language-specific tests for any language @var{lang} besides C. Examples are
7114 @file{gdb.cp} and @file{gdb.java}.
7116 @item gdb.@var{platform}
7117 Non-portable tests. The tests are specific to a specific configuration
7118 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
7121 @item gdb.@var{compiler}
7122 Tests specific to a particular compiler. As of this writing (June
7123 1999), there aren't currently any groups of tests in this category that
7124 couldn't just as sensibly be made platform-specific, but one could
7125 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
7128 @item gdb.@var{subsystem}
7129 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
7130 instance, @file{gdb.disasm} exercises various disassemblers, while
7131 @file{gdb.stabs} tests pathways through the stabs symbol reader.
7134 @section Writing Tests
7135 @cindex writing tests
7137 In many areas, the @value{GDBN} tests are already quite comprehensive; you
7138 should be able to copy existing tests to handle new cases.
7140 You should try to use @code{gdb_test} whenever possible, since it
7141 includes cases to handle all the unexpected errors that might happen.
7142 However, it doesn't cost anything to add new test procedures; for
7143 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
7144 calls @code{gdb_test} multiple times.
7146 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
7147 necessary. Even if @value{GDBN} has several valid responses to
7148 a command, you can use @code{gdb_test_multiple}. Like @code{gdb_test},
7149 @code{gdb_test_multiple} recognizes internal errors and unexpected
7152 Do not write tests which expect a literal tab character from @value{GDBN}.
7153 On some operating systems (e.g.@: OpenBSD) the TTY layer expands tabs to
7154 spaces, so by the time @value{GDBN}'s output reaches expect the tab is gone.
7156 The source language programs do @emph{not} need to be in a consistent
7157 style. Since @value{GDBN} is used to debug programs written in many different
7158 styles, it's worth having a mix of styles in the testsuite; for
7159 instance, some @value{GDBN} bugs involving the display of source lines would
7160 never manifest themselves if the programs used GNU coding style
7167 Check the @file{README} file, it often has useful information that does not
7168 appear anywhere else in the directory.
7171 * Getting Started:: Getting started working on @value{GDBN}
7172 * Debugging GDB:: Debugging @value{GDBN} with itself
7175 @node Getting Started,,, Hints
7177 @section Getting Started
7179 @value{GDBN} is a large and complicated program, and if you first starting to
7180 work on it, it can be hard to know where to start. Fortunately, if you
7181 know how to go about it, there are ways to figure out what is going on.
7183 This manual, the @value{GDBN} Internals manual, has information which applies
7184 generally to many parts of @value{GDBN}.
7186 Information about particular functions or data structures are located in
7187 comments with those functions or data structures. If you run across a
7188 function or a global variable which does not have a comment correctly
7189 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
7190 free to submit a bug report, with a suggested comment if you can figure
7191 out what the comment should say. If you find a comment which is
7192 actually wrong, be especially sure to report that.
7194 Comments explaining the function of macros defined in host, target, or
7195 native dependent files can be in several places. Sometimes they are
7196 repeated every place the macro is defined. Sometimes they are where the
7197 macro is used. Sometimes there is a header file which supplies a
7198 default definition of the macro, and the comment is there. This manual
7199 also documents all the available macros.
7200 @c (@pxref{Host Conditionals}, @pxref{Target
7201 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
7204 Start with the header files. Once you have some idea of how
7205 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
7206 @file{gdbtypes.h}), you will find it much easier to understand the
7207 code which uses and creates those symbol tables.
7209 You may wish to process the information you are getting somehow, to
7210 enhance your understanding of it. Summarize it, translate it to another
7211 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
7212 the code to predict what a test case would do and write the test case
7213 and verify your prediction, etc. If you are reading code and your eyes
7214 are starting to glaze over, this is a sign you need to use a more active
7217 Once you have a part of @value{GDBN} to start with, you can find more
7218 specifically the part you are looking for by stepping through each
7219 function with the @code{next} command. Do not use @code{step} or you
7220 will quickly get distracted; when the function you are stepping through
7221 calls another function try only to get a big-picture understanding
7222 (perhaps using the comment at the beginning of the function being
7223 called) of what it does. This way you can identify which of the
7224 functions being called by the function you are stepping through is the
7225 one which you are interested in. You may need to examine the data
7226 structures generated at each stage, with reference to the comments in
7227 the header files explaining what the data structures are supposed to
7230 Of course, this same technique can be used if you are just reading the
7231 code, rather than actually stepping through it. The same general
7232 principle applies---when the code you are looking at calls something
7233 else, just try to understand generally what the code being called does,
7234 rather than worrying about all its details.
7236 @cindex command implementation
7237 A good place to start when tracking down some particular area is with
7238 a command which invokes that feature. Suppose you want to know how
7239 single-stepping works. As a @value{GDBN} user, you know that the
7240 @code{step} command invokes single-stepping. The command is invoked
7241 via command tables (see @file{command.h}); by convention the function
7242 which actually performs the command is formed by taking the name of
7243 the command and adding @samp{_command}, or in the case of an
7244 @code{info} subcommand, @samp{_info}. For example, the @code{step}
7245 command invokes the @code{step_command} function and the @code{info
7246 display} command invokes @code{display_info}. When this convention is
7247 not followed, you might have to use @code{grep} or @kbd{M-x
7248 tags-search} in emacs, or run @value{GDBN} on itself and set a
7249 breakpoint in @code{execute_command}.
7251 @cindex @code{bug-gdb} mailing list
7252 If all of the above fail, it may be appropriate to ask for information
7253 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
7254 wondering if anyone could give me some tips about understanding
7255 @value{GDBN}''---if we had some magic secret we would put it in this manual.
7256 Suggestions for improving the manual are always welcome, of course.
7258 @node Debugging GDB,,,Hints
7260 @section Debugging @value{GDBN} with itself
7261 @cindex debugging @value{GDBN}
7263 If @value{GDBN} is limping on your machine, this is the preferred way to get it
7264 fully functional. Be warned that in some ancient Unix systems, like
7265 Ultrix 4.2, a program can't be running in one process while it is being
7266 debugged in another. Rather than typing the command @kbd{@w{./gdb
7267 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
7268 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
7270 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
7271 @file{.gdbinit} file that sets up some simple things to make debugging
7272 gdb easier. The @code{info} command, when executed without a subcommand
7273 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
7274 gdb. See @file{.gdbinit} for details.
7276 If you use emacs, you will probably want to do a @code{make TAGS} after
7277 you configure your distribution; this will put the machine dependent
7278 routines for your local machine where they will be accessed first by
7281 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
7282 have run @code{fixincludes} if you are compiling with gcc.
7284 @section Submitting Patches
7286 @cindex submitting patches
7287 Thanks for thinking of offering your changes back to the community of
7288 @value{GDBN} users. In general we like to get well designed enhancements.
7289 Thanks also for checking in advance about the best way to transfer the
7292 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
7293 This manual summarizes what we believe to be clean design for @value{GDBN}.
7295 If the maintainers don't have time to put the patch in when it arrives,
7296 or if there is any question about a patch, it goes into a large queue
7297 with everyone else's patches and bug reports.
7299 @cindex legal papers for code contributions
7300 The legal issue is that to incorporate substantial changes requires a
7301 copyright assignment from you and/or your employer, granting ownership
7302 of the changes to the Free Software Foundation. You can get the
7303 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
7304 and asking for it. We recommend that people write in "All programs
7305 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
7306 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
7308 contributed with only one piece of legalese pushed through the
7309 bureaucracy and filed with the FSF. We can't start merging changes until
7310 this paperwork is received by the FSF (their rules, which we follow
7311 since we maintain it for them).
7313 Technically, the easiest way to receive changes is to receive each
7314 feature as a small context diff or unidiff, suitable for @code{patch}.
7315 Each message sent to me should include the changes to C code and
7316 header files for a single feature, plus @file{ChangeLog} entries for
7317 each directory where files were modified, and diffs for any changes
7318 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
7319 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
7320 single feature, they can be split down into multiple messages.
7322 In this way, if we read and like the feature, we can add it to the
7323 sources with a single patch command, do some testing, and check it in.
7324 If you leave out the @file{ChangeLog}, we have to write one. If you leave
7325 out the doc, we have to puzzle out what needs documenting. Etc., etc.
7327 The reason to send each change in a separate message is that we will not
7328 install some of the changes. They'll be returned to you with questions
7329 or comments. If we're doing our job correctly, the message back to you
7330 will say what you have to fix in order to make the change acceptable.
7331 The reason to have separate messages for separate features is so that
7332 the acceptable changes can be installed while one or more changes are
7333 being reworked. If multiple features are sent in a single message, we
7334 tend to not put in the effort to sort out the acceptable changes from
7335 the unacceptable, so none of the features get installed until all are
7338 If this sounds painful or authoritarian, well, it is. But we get a lot
7339 of bug reports and a lot of patches, and many of them don't get
7340 installed because we don't have the time to finish the job that the bug
7341 reporter or the contributor could have done. Patches that arrive
7342 complete, working, and well designed, tend to get installed on the day
7343 they arrive. The others go into a queue and get installed as time
7344 permits, which, since the maintainers have many demands to meet, may not
7345 be for quite some time.
7347 Please send patches directly to
7348 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
7350 @section Obsolete Conditionals
7351 @cindex obsolete code
7353 Fragments of old code in @value{GDBN} sometimes reference or set the following
7354 configuration macros. They should not be used by new code, and old uses
7355 should be removed as those parts of the debugger are otherwise touched.
7358 @item STACK_END_ADDR
7359 This macro used to define where the end of the stack appeared, for use
7360 in interpreting core file formats that don't record this address in the
7361 core file itself. This information is now configured in BFD, and @value{GDBN}
7362 gets the info portably from there. The values in @value{GDBN}'s configuration
7363 files should be moved into BFD configuration files (if needed there),
7364 and deleted from all of @value{GDBN}'s config files.
7366 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
7367 is so old that it has never been converted to use BFD. Now that's old!
7371 @include observer.texi