1 \input texinfo @c -*- texinfo -*-
2 @setfilename gdbint.info
4 @dircategory Software development
6 * Gdb-Internals: (gdbint). The GNU debugger's internals.
10 This file documents the internals of the GNU debugger @value{GDBN}.
11 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1996, 1998, 1999, 2000, 2001,
12 2002, 2003, 2004, 2005, 2006
13 Free Software Foundation, Inc.
14 Contributed by Cygnus Solutions. Written by John Gilmore.
15 Second Edition by Stan Shebs.
17 Permission is granted to copy, distribute and/or modify this document
18 under the terms of the GNU Free Documentation License, Version 1.1 or
19 any later version published by the Free Software Foundation; with no
20 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
21 Texts. A copy of the license is included in the section entitled ``GNU
22 Free Documentation License''.
25 @setchapternewpage off
26 @settitle @value{GDBN} Internals
32 @title @value{GDBN} Internals
33 @subtitle{A guide to the internals of the GNU debugger}
35 @author Cygnus Solutions
36 @author Second Edition:
38 @author Cygnus Solutions
41 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
42 \xdef\manvers{\$Revision$} % For use in headers, footers too
44 \hfill Cygnus Solutions\par
46 \hfill \TeX{}info \texinfoversion\par
50 @vskip 0pt plus 1filll
51 Copyright @copyright{} 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001,
52 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.1 or
56 any later version published by the Free Software Foundation; with no
57 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
58 Texts. A copy of the license is included in the section entitled ``GNU
59 Free Documentation License''.
65 @c Perhaps this should be the title of the document (but only for info,
66 @c not for TeX). Existing GNU manuals seem inconsistent on this point.
67 @top Scope of this Document
69 This document documents the internals of the GNU debugger, @value{GDBN}. It
70 includes description of @value{GDBN}'s key algorithms and operations, as well
71 as the mechanisms that adapt @value{GDBN} to specific hosts and targets.
82 * Target Architecture Definition::
83 * Target Descriptions::
84 * Target Vector Definition::
89 * Versions and Branches::
90 * Start of New Year Procedure::
95 * GDB Observers:: @value{GDBN} Currently available observers
96 * GNU Free Documentation License:: The license for this documentation
102 @chapter Requirements
103 @cindex requirements for @value{GDBN}
105 Before diving into the internals, you should understand the formal
106 requirements and other expectations for @value{GDBN}. Although some
107 of these may seem obvious, there have been proposals for @value{GDBN}
108 that have run counter to these requirements.
110 First of all, @value{GDBN} is a debugger. It's not designed to be a
111 front panel for embedded systems. It's not a text editor. It's not a
112 shell. It's not a programming environment.
114 @value{GDBN} is an interactive tool. Although a batch mode is
115 available, @value{GDBN}'s primary role is to interact with a human
118 @value{GDBN} should be responsive to the user. A programmer hot on
119 the trail of a nasty bug, and operating under a looming deadline, is
120 going to be very impatient of everything, including the response time
121 to debugger commands.
123 @value{GDBN} should be relatively permissive, such as for expressions.
124 While the compiler should be picky (or have the option to be made
125 picky), since source code lives for a long time usually, the
126 programmer doing debugging shouldn't be spending time figuring out to
127 mollify the debugger.
129 @value{GDBN} will be called upon to deal with really large programs.
130 Executable sizes of 50 to 100 megabytes occur regularly, and we've
131 heard reports of programs approaching 1 gigabyte in size.
133 @value{GDBN} should be able to run everywhere. No other debugger is
134 available for even half as many configurations as @value{GDBN}
138 @node Overall Structure
140 @chapter Overall Structure
142 @value{GDBN} consists of three major subsystems: user interface,
143 symbol handling (the @dfn{symbol side}), and target system handling (the
146 The user interface consists of several actual interfaces, plus
149 The symbol side consists of object file readers, debugging info
150 interpreters, symbol table management, source language expression
151 parsing, type and value printing.
153 The target side consists of execution control, stack frame analysis, and
154 physical target manipulation.
156 The target side/symbol side division is not formal, and there are a
157 number of exceptions. For instance, core file support involves symbolic
158 elements (the basic core file reader is in BFD) and target elements (it
159 supplies the contents of memory and the values of registers). Instead,
160 this division is useful for understanding how the minor subsystems
163 @section The Symbol Side
165 The symbolic side of @value{GDBN} can be thought of as ``everything
166 you can do in @value{GDBN} without having a live program running''.
167 For instance, you can look at the types of variables, and evaluate
168 many kinds of expressions.
170 @section The Target Side
172 The target side of @value{GDBN} is the ``bits and bytes manipulator''.
173 Although it may make reference to symbolic info here and there, most
174 of the target side will run with only a stripped executable
175 available---or even no executable at all, in remote debugging cases.
177 Operations such as disassembly, stack frame crawls, and register
178 display, are able to work with no symbolic info at all. In some cases,
179 such as disassembly, @value{GDBN} will use symbolic info to present addresses
180 relative to symbols rather than as raw numbers, but it will work either
183 @section Configurations
187 @dfn{Host} refers to attributes of the system where @value{GDBN} runs.
188 @dfn{Target} refers to the system where the program being debugged
189 executes. In most cases they are the same machine, in which case a
190 third type of @dfn{Native} attributes come into play.
192 Defines and include files needed to build on the host are host support.
193 Examples are tty support, system defined types, host byte order, host
196 Defines and information needed to handle the target format are target
197 dependent. Examples are the stack frame format, instruction set,
198 breakpoint instruction, registers, and how to set up and tear down the stack
201 Information that is only needed when the host and target are the same,
202 is native dependent. One example is Unix child process support; if the
203 host and target are not the same, doing a fork to start the target
204 process is a bad idea. The various macros needed for finding the
205 registers in the @code{upage}, running @code{ptrace}, and such are all
206 in the native-dependent files.
208 Another example of native-dependent code is support for features that
209 are really part of the target environment, but which require
210 @code{#include} files that are only available on the host system. Core
211 file handling and @code{setjmp} handling are two common cases.
213 When you want to make @value{GDBN} work ``native'' on a particular machine, you
214 have to include all three kinds of information.
216 @section Source Tree Structure
217 @cindex @value{GDBN} source tree structure
219 The @value{GDBN} source directory has a mostly flat structure---there
220 are only a few subdirectories. A file's name usually gives a hint as
221 to what it does; for example, @file{stabsread.c} reads stabs,
222 @file{dwarfread.c} reads DWARF, etc.
224 Files that are related to some common task have names that share
225 common substrings. For example, @file{*-thread.c} files deal with
226 debugging threads on various platforms; @file{*read.c} files deal with
227 reading various kinds of symbol and object files; @file{inf*.c} files
228 deal with direct control of the @dfn{inferior program} (@value{GDBN}
229 parlance for the program being debugged).
231 There are several dozens of files in the @file{*-tdep.c} family.
232 @samp{tdep} stands for @dfn{target-dependent code}---each of these
233 files implements debug support for a specific target architecture
234 (sparc, mips, etc). Usually, only one of these will be used in a
235 specific @value{GDBN} configuration (sometimes two, closely related).
237 Similarly, there are many @file{*-nat.c} files, each one for native
238 debugging on a specific system (e.g., @file{sparc-linux-nat.c} is for
239 native debugging of Sparc machines running the Linux kernel).
241 The few subdirectories of the source tree are:
245 Code that implements @dfn{CLI}, the @value{GDBN} Command-Line
246 Interpreter. @xref{User Interface, Command Interpreter}.
249 Code for the @value{GDBN} remote server.
252 Code for Insight, the @value{GDBN} TK-based GUI front-end.
255 The @dfn{GDB/MI}, the @value{GDBN} Machine Interface interpreter.
258 Target signal translation code.
261 Code for @dfn{TUI}, the @value{GDBN} Text-mode full-screen User
262 Interface. @xref{User Interface, TUI}.
270 @value{GDBN} uses a number of debugging-specific algorithms. They are
271 often not very complicated, but get lost in the thicket of special
272 cases and real-world issues. This chapter describes the basic
273 algorithms and mentions some of the specific target definitions that
279 @cindex call stack frame
280 A frame is a construct that @value{GDBN} uses to keep track of calling
281 and called functions.
283 @cindex frame, unwind
284 @value{GDBN}'s frame model, a fresh design, was implemented with the
285 need to support @sc{dwarf}'s Call Frame Information in mind. In fact,
286 the term ``unwind'' is taken directly from that specification.
287 Developers wishing to learn more about unwinders, are encouraged to
288 read the @sc{dwarf} specification.
290 @findex frame_register_unwind
291 @findex get_frame_register
292 @value{GDBN}'s model is that you find a frame's registers by
293 ``unwinding'' them from the next younger frame. That is,
294 @samp{get_frame_register} which returns the value of a register in
295 frame #1 (the next-to-youngest frame), is implemented by calling frame
296 #0's @code{frame_register_unwind} (the youngest frame). But then the
297 obvious question is: how do you access the registers of the youngest
300 @cindex sentinel frame
301 @findex get_frame_type
302 @vindex SENTINEL_FRAME
303 To answer this question, GDB has the @dfn{sentinel} frame, the
304 ``-1st'' frame. Unwinding registers from the sentinel frame gives you
305 the current values of the youngest real frame's registers. If @var{f}
306 is a sentinel frame, then @code{get_frame_type (@var{f}) ==
309 @section Prologue Analysis
311 @cindex prologue analysis
312 @cindex call frame information
313 @cindex CFI (call frame information)
314 To produce a backtrace and allow the user to manipulate older frames'
315 variables and arguments, @value{GDBN} needs to find the base addresses
316 of older frames, and discover where those frames' registers have been
317 saved. Since a frame's ``callee-saves'' registers get saved by
318 younger frames if and when they're reused, a frame's registers may be
319 scattered unpredictably across younger frames. This means that
320 changing the value of a register-allocated variable in an older frame
321 may actually entail writing to a save slot in some younger frame.
323 Modern versions of GCC emit Dwarf call frame information (``CFI''),
324 which describes how to find frame base addresses and saved registers.
325 But CFI is not always available, so as a fallback @value{GDBN} uses a
326 technique called @dfn{prologue analysis} to find frame sizes and saved
327 registers. A prologue analyzer disassembles the function's machine
328 code starting from its entry point, and looks for instructions that
329 allocate frame space, save the stack pointer in a frame pointer
330 register, save registers, and so on. Obviously, this can't be done
331 accurately in general, but it's tractable to do well enough to be very
332 helpful. Prologue analysis predates the GNU toolchain's support for
333 CFI; at one time, prologue analysis was the only mechanism
334 @value{GDBN} used for stack unwinding at all, when the function
335 calling conventions didn't specify a fixed frame layout.
337 In the olden days, function prologues were generated by hand-written,
338 target-specific code in GCC, and treated as opaque and untouchable by
339 optimizers. Looking at this code, it was usually straightforward to
340 write a prologue analyzer for @value{GDBN} that would accurately
341 understand all the prologues GCC would generate. However, over time
342 GCC became more aggressive about instruction scheduling, and began to
343 understand more about the semantics of the prologue instructions
344 themselves; in response, @value{GDBN}'s analyzers became more complex
345 and fragile. Keeping the prologue analyzers working as GCC (and the
346 instruction sets themselves) evolved became a substantial task.
348 @cindex @file{prologue-value.c}
349 @cindex abstract interpretation of function prologues
350 @cindex pseudo-evaluation of function prologues
351 To try to address this problem, the code in @file{prologue-value.h}
352 and @file{prologue-value.c} provides a general framework for writing
353 prologue analyzers that are simpler and more robust than ad-hoc
354 analyzers. When we analyze a prologue using the prologue-value
355 framework, we're really doing ``abstract interpretation'' or
356 ``pseudo-evaluation'': running the function's code in simulation, but
357 using conservative approximations of the values registers and memory
358 would hold when the code actually runs. For example, if our function
359 starts with the instruction:
362 addi r1, 42 # add 42 to r1
365 we don't know exactly what value will be in @code{r1} after executing
366 this instruction, but we do know it'll be 42 greater than its original
369 If we then see an instruction like:
372 addi r1, 22 # add 22 to r1
375 we still don't know what @code{r1's} value is, but again, we can say
376 it is now 64 greater than its original value.
378 If the next instruction were:
381 mov r2, r1 # set r2 to r1's value
384 then we can say that @code{r2's} value is now the original value of
387 It's common for prologues to save registers on the stack, so we'll
388 need to track the values of stack frame slots, as well as the
389 registers. So after an instruction like this:
395 then we'd know that the stack slot four bytes above the frame pointer
396 holds the original value of @code{r1} plus 64.
400 Of course, this can only go so far before it gets unreasonable. If we
401 wanted to be able to say anything about the value of @code{r1} after
405 xor r1, r3 # exclusive-or r1 and r3, place result in r1
408 then things would get pretty complex. But remember, we're just doing
409 a conservative approximation; if exclusive-or instructions aren't
410 relevant to prologues, we can just say @code{r1}'s value is now
411 ``unknown''. We can ignore things that are too complex, if that loss of
412 information is acceptable for our application.
414 So when we say ``conservative approximation'' here, what we mean is an
415 approximation that is either accurate, or marked ``unknown'', but
418 Using this framework, a prologue analyzer is simply an interpreter for
419 machine code, but one that uses conservative approximations for the
420 contents of registers and memory instead of actual values. Starting
421 from the function's entry point, you simulate instructions up to the
422 current PC, or an instruction that you don't know how to simulate.
423 Now you can examine the state of the registers and stack slots you've
429 To see how large your stack frame is, just check the value of the
430 stack pointer register; if it's the original value of the SP
431 minus a constant, then that constant is the stack frame's size.
432 If the SP's value has been marked as ``unknown'', then that means
433 the prologue has done something too complex for us to track, and
434 we don't know the frame size.
437 To see where we've saved the previous frame's registers, we just
438 search the values we've tracked --- stack slots, usually, but
439 registers, too, if you want --- for something equal to the register's
440 original value. If the calling conventions suggest a standard place
441 to save a given register, then we can check there first, but really,
442 anything that will get us back the original value will probably work.
445 This does take some work. But prologue analyzers aren't
446 quick-and-simple pattern patching to recognize a few fixed prologue
447 forms any more; they're big, hairy functions. Along with inferior
448 function calls, prologue analysis accounts for a substantial portion
449 of the time needed to stabilize a @value{GDBN} port. So it's
450 worthwhile to look for an approach that will be easier to understand
451 and maintain. In the approach described above:
456 It's easier to see that the analyzer is correct: you just see
457 whether the analyzer properly (albeit conservatively) simulates
458 the effect of each instruction.
461 It's easier to extend the analyzer: you can add support for new
462 instructions, and know that you haven't broken anything that
463 wasn't already broken before.
466 It's orthogonal: to gather new information, you don't need to
467 complicate the code for each instruction. As long as your domain
468 of conservative values is already detailed enough to tell you
469 what you need, then all the existing instruction simulations are
470 already gathering the right data for you.
474 The file @file{prologue-value.h} contains detailed comments explaining
475 the framework and how to use it.
478 @section Breakpoint Handling
481 In general, a breakpoint is a user-designated location in the program
482 where the user wants to regain control if program execution ever reaches
485 There are two main ways to implement breakpoints; either as ``hardware''
486 breakpoints or as ``software'' breakpoints.
488 @cindex hardware breakpoints
489 @cindex program counter
490 Hardware breakpoints are sometimes available as a builtin debugging
491 features with some chips. Typically these work by having dedicated
492 register into which the breakpoint address may be stored. If the PC
493 (shorthand for @dfn{program counter})
494 ever matches a value in a breakpoint registers, the CPU raises an
495 exception and reports it to @value{GDBN}.
497 Another possibility is when an emulator is in use; many emulators
498 include circuitry that watches the address lines coming out from the
499 processor, and force it to stop if the address matches a breakpoint's
502 A third possibility is that the target already has the ability to do
503 breakpoints somehow; for instance, a ROM monitor may do its own
504 software breakpoints. So although these are not literally ``hardware
505 breakpoints'', from @value{GDBN}'s point of view they work the same;
506 @value{GDBN} need not do anything more than set the breakpoint and wait
507 for something to happen.
509 Since they depend on hardware resources, hardware breakpoints may be
510 limited in number; when the user asks for more, @value{GDBN} will
511 start trying to set software breakpoints. (On some architectures,
512 notably the 32-bit x86 platforms, @value{GDBN} cannot always know
513 whether there's enough hardware resources to insert all the hardware
514 breakpoints and watchpoints. On those platforms, @value{GDBN} prints
515 an error message only when the program being debugged is continued.)
517 @cindex software breakpoints
518 Software breakpoints require @value{GDBN} to do somewhat more work.
519 The basic theory is that @value{GDBN} will replace a program
520 instruction with a trap, illegal divide, or some other instruction
521 that will cause an exception, and then when it's encountered,
522 @value{GDBN} will take the exception and stop the program. When the
523 user says to continue, @value{GDBN} will restore the original
524 instruction, single-step, re-insert the trap, and continue on.
526 Since it literally overwrites the program being tested, the program area
527 must be writable, so this technique won't work on programs in ROM. It
528 can also distort the behavior of programs that examine themselves,
529 although such a situation would be highly unusual.
531 Also, the software breakpoint instruction should be the smallest size of
532 instruction, so it doesn't overwrite an instruction that might be a jump
533 target, and cause disaster when the program jumps into the middle of the
534 breakpoint instruction. (Strictly speaking, the breakpoint must be no
535 larger than the smallest interval between instructions that may be jump
536 targets; perhaps there is an architecture where only even-numbered
537 instructions may jumped to.) Note that it's possible for an instruction
538 set not to have any instructions usable for a software breakpoint,
539 although in practice only the ARC has failed to define such an
543 The basic definition of the software breakpoint is the macro
546 Basic breakpoint object handling is in @file{breakpoint.c}. However,
547 much of the interesting breakpoint action is in @file{infrun.c}.
550 @cindex insert or remove software breakpoint
551 @findex target_remove_breakpoint
552 @findex target_insert_breakpoint
553 @item target_remove_breakpoint (@var{bp_tgt})
554 @itemx target_insert_breakpoint (@var{bp_tgt})
555 Insert or remove a software breakpoint at address
556 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
557 non-zero for failure. On input, @var{bp_tgt} contains the address of the
558 breakpoint, and is otherwise initialized to zero. The fields of the
559 @code{struct bp_target_info} pointed to by @var{bp_tgt} are updated
560 to contain other information about the breakpoint on output. The field
561 @code{placed_address} may be updated if the breakpoint was placed at a
562 related address; the field @code{shadow_contents} contains the real
563 contents of the bytes where the breakpoint has been inserted,
564 if reading memory would return the breakpoint instead of the
565 underlying memory; the field @code{shadow_len} is the length of
566 memory cached in @code{shadow_contents}, if any; and the field
567 @code{placed_size} is optionally set and used by the target, if
568 it could differ from @code{shadow_len}.
570 For example, the remote target @samp{Z0} packet does not require
571 shadowing memory, so @code{shadow_len} is left at zero. However,
572 the length reported by @code{BREAKPOINT_FROM_PC} is cached in
573 @code{placed_size}, so that a matching @samp{z0} packet can be
574 used to remove the breakpoint.
576 @cindex insert or remove hardware breakpoint
577 @findex target_remove_hw_breakpoint
578 @findex target_insert_hw_breakpoint
579 @item target_remove_hw_breakpoint (@var{bp_tgt})
580 @itemx target_insert_hw_breakpoint (@var{bp_tgt})
581 Insert or remove a hardware-assisted breakpoint at address
582 @code{@var{bp_tgt}->placed_address}. Returns zero for success,
583 non-zero for failure. See @code{target_insert_breakpoint} for
584 a description of the @code{struct bp_target_info} pointed to by
585 @var{bp_tgt}; the @code{shadow_contents} and
586 @code{shadow_len} members are not used for hardware breakpoints,
587 but @code{placed_size} may be.
590 @section Single Stepping
592 @section Signal Handling
594 @section Thread Handling
596 @section Inferior Function Calls
598 @section Longjmp Support
600 @cindex @code{longjmp} debugging
601 @value{GDBN} has support for figuring out that the target is doing a
602 @code{longjmp} and for stopping at the target of the jump, if we are
603 stepping. This is done with a few specialized internal breakpoints,
604 which are visible in the output of the @samp{maint info breakpoint}
607 @findex GET_LONGJMP_TARGET
608 To make this work, you need to define a macro called
609 @code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
610 structure and extract the longjmp target address. Since @code{jmp_buf}
611 is target specific, you will need to define it in the appropriate
612 @file{tm-@var{target}.h} file. Look in @file{tm-sun4os4.h} and
613 @file{sparc-tdep.c} for examples of how to do this.
618 Watchpoints are a special kind of breakpoints (@pxref{Algorithms,
619 breakpoints}) which break when data is accessed rather than when some
620 instruction is executed. When you have data which changes without
621 your knowing what code does that, watchpoints are the silver bullet to
622 hunt down and kill such bugs.
624 @cindex hardware watchpoints
625 @cindex software watchpoints
626 Watchpoints can be either hardware-assisted or not; the latter type is
627 known as ``software watchpoints.'' @value{GDBN} always uses
628 hardware-assisted watchpoints if they are available, and falls back on
629 software watchpoints otherwise. Typical situations where @value{GDBN}
630 will use software watchpoints are:
634 The watched memory region is too large for the underlying hardware
635 watchpoint support. For example, each x86 debug register can watch up
636 to 4 bytes of memory, so trying to watch data structures whose size is
637 more than 16 bytes will cause @value{GDBN} to use software
641 The value of the expression to be watched depends on data held in
642 registers (as opposed to memory).
645 Too many different watchpoints requested. (On some architectures,
646 this situation is impossible to detect until the debugged program is
647 resumed.) Note that x86 debug registers are used both for hardware
648 breakpoints and for watchpoints, so setting too many hardware
649 breakpoints might cause watchpoint insertion to fail.
652 No hardware-assisted watchpoints provided by the target
656 Software watchpoints are very slow, since @value{GDBN} needs to
657 single-step the program being debugged and test the value of the
658 watched expression(s) after each instruction. The rest of this
659 section is mostly irrelevant for software watchpoints.
661 When the inferior stops, @value{GDBN} tries to establish, among other
662 possible reasons, whether it stopped due to a watchpoint being hit.
663 For a data-write watchpoint, it does so by evaluating, for each
664 watchpoint, the expression whose value is being watched, and testing
665 whether the watched value has changed. For data-read and data-access
666 watchpoints, @value{GDBN} needs the target to supply a primitive that
667 returns the address of the data that was accessed or read (see the
668 description of @code{target_stopped_data_address} below): if this
669 primitive returns a valid address, @value{GDBN} infers that a
670 watchpoint triggered if it watches an expression whose evaluation uses
673 @value{GDBN} uses several macros and primitives to support hardware
677 @findex TARGET_HAS_HARDWARE_WATCHPOINTS
678 @item TARGET_HAS_HARDWARE_WATCHPOINTS
679 If defined, the target supports hardware watchpoints.
681 @findex TARGET_CAN_USE_HARDWARE_WATCHPOINT
682 @item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other})
683 Return the number of hardware watchpoints of type @var{type} that are
684 possible to be set. The value is positive if @var{count} watchpoints
685 of this type can be set, zero if setting watchpoints of this type is
686 not supported, and negative if @var{count} is more than the maximum
687 number of watchpoints of type @var{type} that can be set. @var{other}
688 is non-zero if other types of watchpoints are currently enabled (there
689 are architectures which cannot set watchpoints of different types at
692 @findex TARGET_REGION_OK_FOR_HW_WATCHPOINT
693 @item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len})
694 Return non-zero if hardware watchpoints can be used to watch a region
695 whose address is @var{addr} and whose length in bytes is @var{len}.
697 @cindex insert or remove hardware watchpoint
698 @findex target_insert_watchpoint
699 @findex target_remove_watchpoint
700 @item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
701 @itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type})
702 Insert or remove a hardware watchpoint starting at @var{addr}, for
703 @var{len} bytes. @var{type} is the watchpoint type, one of the
704 possible values of the enumerated data type @code{target_hw_bp_type},
705 defined by @file{breakpoint.h} as follows:
708 enum target_hw_bp_type
710 hw_write = 0, /* Common (write) HW watchpoint */
711 hw_read = 1, /* Read HW watchpoint */
712 hw_access = 2, /* Access (read or write) HW watchpoint */
713 hw_execute = 3 /* Execute HW breakpoint */
718 These two macros should return 0 for success, non-zero for failure.
720 @findex target_stopped_data_address
721 @item target_stopped_data_address (@var{addr_p})
722 If the inferior has some watchpoint that triggered, place the address
723 associated with the watchpoint at the location pointed to by
724 @var{addr_p} and return non-zero. Otherwise, return zero. Note that
725 this primitive is used by @value{GDBN} only on targets that support
726 data-read or data-access type watchpoints, so targets that have
727 support only for data-write watchpoints need not implement these
730 @findex HAVE_STEPPABLE_WATCHPOINT
731 @item HAVE_STEPPABLE_WATCHPOINT
732 If defined to a non-zero value, it is not necessary to disable a
733 watchpoint to step over it.
735 @findex HAVE_NONSTEPPABLE_WATCHPOINT
736 @item HAVE_NONSTEPPABLE_WATCHPOINT
737 If defined to a non-zero value, @value{GDBN} should disable a
738 watchpoint to step the inferior over it.
740 @findex HAVE_CONTINUABLE_WATCHPOINT
741 @item HAVE_CONTINUABLE_WATCHPOINT
742 If defined to a non-zero value, it is possible to continue the
743 inferior after a watchpoint has been hit.
745 @findex CANNOT_STEP_HW_WATCHPOINTS
746 @item CANNOT_STEP_HW_WATCHPOINTS
747 If this is defined to a non-zero value, @value{GDBN} will remove all
748 watchpoints before stepping the inferior.
750 @findex STOPPED_BY_WATCHPOINT
751 @item STOPPED_BY_WATCHPOINT (@var{wait_status})
752 Return non-zero if stopped by a watchpoint. @var{wait_status} is of
753 the type @code{struct target_waitstatus}, defined by @file{target.h}.
754 Normally, this macro is defined to invoke the function pointed to by
755 the @code{to_stopped_by_watchpoint} member of the structure (of the
756 type @code{target_ops}, defined on @file{target.h}) that describes the
757 target-specific operations; @code{to_stopped_by_watchpoint} ignores
758 the @var{wait_status} argument.
760 @value{GDBN} does not require the non-zero value returned by
761 @code{STOPPED_BY_WATCHPOINT} to be 100% correct, so if a target cannot
762 determine for sure whether the inferior stopped due to a watchpoint,
763 it could return non-zero ``just in case''.
766 @subsection x86 Watchpoints
767 @cindex x86 debug registers
768 @cindex watchpoints, on x86
770 The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug
771 registers designed to facilitate debugging. @value{GDBN} provides a
772 generic library of functions that x86-based ports can use to implement
773 support for watchpoints and hardware-assisted breakpoints. This
774 subsection documents the x86 watchpoint facilities in @value{GDBN}.
776 To use the generic x86 watchpoint support, a port should do the
780 @findex I386_USE_GENERIC_WATCHPOINTS
782 Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the
783 target-dependent headers.
786 Include the @file{config/i386/nm-i386.h} header file @emph{after}
787 defining @code{I386_USE_GENERIC_WATCHPOINTS}.
790 Add @file{i386-nat.o} to the value of the Make variable
791 @code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}) or
792 @code{TDEPFILES} (@pxref{Target Architecture Definition, TDEPFILES}).
795 Provide implementations for the @code{I386_DR_LOW_*} macros described
796 below. Typically, each macro should call a target-specific function
797 which does the real work.
800 The x86 watchpoint support works by maintaining mirror images of the
801 debug registers. Values are copied between the mirror images and the
802 real debug registers via a set of macros which each target needs to
806 @findex I386_DR_LOW_SET_CONTROL
807 @item I386_DR_LOW_SET_CONTROL (@var{val})
808 Set the Debug Control (DR7) register to the value @var{val}.
810 @findex I386_DR_LOW_SET_ADDR
811 @item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr})
812 Put the address @var{addr} into the debug register number @var{idx}.
814 @findex I386_DR_LOW_RESET_ADDR
815 @item I386_DR_LOW_RESET_ADDR (@var{idx})
816 Reset (i.e.@: zero out) the address stored in the debug register
819 @findex I386_DR_LOW_GET_STATUS
820 @item I386_DR_LOW_GET_STATUS
821 Return the value of the Debug Status (DR6) register. This value is
822 used immediately after it is returned by
823 @code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status
827 For each one of the 4 debug registers (whose indices are from 0 to 3)
828 that store addresses, a reference count is maintained by @value{GDBN},
829 to allow sharing of debug registers by several watchpoints. This
830 allows users to define several watchpoints that watch the same
831 expression, but with different conditions and/or commands, without
832 wasting debug registers which are in short supply. @value{GDBN}
833 maintains the reference counts internally, targets don't have to do
834 anything to use this feature.
836 The x86 debug registers can each watch a region that is 1, 2, or 4
837 bytes long. The ia32 architecture requires that each watched region
838 be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte
839 region on 4-byte boundary. However, the x86 watchpoint support in
840 @value{GDBN} can watch unaligned regions and regions larger than 4
841 bytes (up to 16 bytes) by allocating several debug registers to watch
842 a single region. This allocation of several registers per a watched
843 region is also done automatically without target code intervention.
845 The generic x86 watchpoint support provides the following API for the
846 @value{GDBN}'s application code:
849 @findex i386_region_ok_for_watchpoint
850 @item i386_region_ok_for_watchpoint (@var{addr}, @var{len})
851 The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call
852 this function. It counts the number of debug registers required to
853 watch a given region, and returns a non-zero value if that number is
854 less than 4, the number of debug registers available to x86
857 @findex i386_stopped_data_address
858 @item i386_stopped_data_address (@var{addr_p})
860 @code{target_stopped_data_address} is set to call this function.
862 function examines the breakpoint condition bits in the DR6 Debug
863 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
864 macro, and returns the address associated with the first bit that is
867 @findex i386_stopped_by_watchpoint
868 @item i386_stopped_by_watchpoint (void)
869 The macro @code{STOPPED_BY_WATCHPOINT}
870 is set to call this function. The
871 argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This
872 function examines the breakpoint condition bits in the DR6 Debug
873 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
874 macro, and returns true if any bit is set. Otherwise, false is
877 @findex i386_insert_watchpoint
878 @findex i386_remove_watchpoint
879 @item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type})
880 @itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type})
881 Insert or remove a watchpoint. The macros
882 @code{target_insert_watchpoint} and @code{target_remove_watchpoint}
883 are set to call these functions. @code{i386_insert_watchpoint} first
884 looks for a debug register which is already set to watch the same
885 region for the same access types; if found, it just increments the
886 reference count of that debug register, thus implementing debug
887 register sharing between watchpoints. If no such register is found,
888 the function looks for a vacant debug register, sets its mirrored
889 value to @var{addr}, sets the mirrored value of DR7 Debug Control
890 register as appropriate for the @var{len} and @var{type} parameters,
891 and then passes the new values of the debug register and DR7 to the
892 inferior by calling @code{I386_DR_LOW_SET_ADDR} and
893 @code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is
894 required to cover the given region, the above process is repeated for
897 @code{i386_remove_watchpoint} does the opposite: it resets the address
898 in the mirrored value of the debug register and its read/write and
899 length bits in the mirrored value of DR7, then passes these new
900 values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and
901 @code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several
902 watchpoints, each time a @code{i386_remove_watchpoint} is called, it
903 decrements the reference count, and only calls
904 @code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when
905 the count goes to zero.
907 @findex i386_insert_hw_breakpoint
908 @findex i386_remove_hw_breakpoint
909 @item i386_insert_hw_breakpoint (@var{bp_tgt})
910 @itemx i386_remove_hw_breakpoint (@var{bp_tgt})
911 These functions insert and remove hardware-assisted breakpoints. The
912 macros @code{target_insert_hw_breakpoint} and
913 @code{target_remove_hw_breakpoint} are set to call these functions.
914 The argument is a @code{struct bp_target_info *}, as described in
915 the documentation for @code{target_insert_breakpoint}.
916 These functions work like @code{i386_insert_watchpoint} and
917 @code{i386_remove_watchpoint}, respectively, except that they set up
918 the debug registers to watch instruction execution, and each
919 hardware-assisted breakpoint always requires exactly one debug
922 @findex i386_stopped_by_hwbp
923 @item i386_stopped_by_hwbp (void)
924 This function returns non-zero if the inferior has some watchpoint or
925 hardware breakpoint that triggered. It works like
926 @code{i386_stopped_data_address}, except that it doesn't record the
927 address whose watchpoint triggered.
929 @findex i386_cleanup_dregs
930 @item i386_cleanup_dregs (void)
931 This function clears all the reference counts, addresses, and control
932 bits in the mirror images of the debug registers. It doesn't affect
933 the actual debug registers in the inferior process.
940 x86 processors support setting watchpoints on I/O reads or writes.
941 However, since no target supports this (as of March 2001), and since
942 @code{enum target_hw_bp_type} doesn't even have an enumeration for I/O
943 watchpoints, this feature is not yet available to @value{GDBN} running
947 x86 processors can enable watchpoints locally, for the current task
948 only, or globally, for all the tasks. For each debug register,
949 there's a bit in the DR7 Debug Control register that determines
950 whether the associated address is watched locally or globally. The
951 current implementation of x86 watchpoint support in @value{GDBN}
952 always sets watchpoints to be locally enabled, since global
953 watchpoints might interfere with the underlying OS and are probably
954 unavailable in many platforms.
960 In the abstract, a checkpoint is a point in the execution history of
961 the program, which the user may wish to return to at some later time.
963 Internally, a checkpoint is a saved copy of the program state, including
964 whatever information is required in order to restore the program to that
965 state at a later time. This can be expected to include the state of
966 registers and memory, and may include external state such as the state
967 of open files and devices.
969 There are a number of ways in which checkpoints may be implemented
970 in gdb, e.g.@: as corefiles, as forked processes, and as some opaque
971 method implemented on the target side.
973 A corefile can be used to save an image of target memory and register
974 state, which can in principle be restored later --- but corefiles do
975 not typically include information about external entities such as
976 open files. Currently this method is not implemented in gdb.
978 A forked process can save the state of user memory and registers,
979 as well as some subset of external (kernel) state. This method
980 is used to implement checkpoints on Linux, and in principle might
981 be used on other systems.
983 Some targets, e.g.@: simulators, might have their own built-in
984 method for saving checkpoints, and gdb might be able to take
985 advantage of that capability without necessarily knowing any
986 details of how it is done.
989 @section Observing changes in @value{GDBN} internals
990 @cindex observer pattern interface
991 @cindex notifications about changes in internals
993 In order to function properly, several modules need to be notified when
994 some changes occur in the @value{GDBN} internals. Traditionally, these
995 modules have relied on several paradigms, the most common ones being
996 hooks and gdb-events. Unfortunately, none of these paradigms was
997 versatile enough to become the standard notification mechanism in
998 @value{GDBN}. The fact that they only supported one ``client'' was also
1001 A new paradigm, based on the Observer pattern of the @cite{Design
1002 Patterns} book, has therefore been implemented. The goal was to provide
1003 a new interface overcoming the issues with the notification mechanisms
1004 previously available. This new interface needed to be strongly typed,
1005 easy to extend, and versatile enough to be used as the standard
1006 interface when adding new notifications.
1008 See @ref{GDB Observers} for a brief description of the observers
1009 currently implemented in GDB. The rationale for the current
1010 implementation is also briefly discussed.
1012 @node User Interface
1014 @chapter User Interface
1016 @value{GDBN} has several user interfaces. Although the command-line interface
1017 is the most common and most familiar, there are others.
1019 @section Command Interpreter
1021 @cindex command interpreter
1023 The command interpreter in @value{GDBN} is fairly simple. It is designed to
1024 allow for the set of commands to be augmented dynamically, and also
1025 has a recursive subcommand capability, where the first argument to
1026 a command may itself direct a lookup on a different command list.
1028 For instance, the @samp{set} command just starts a lookup on the
1029 @code{setlist} command list, while @samp{set thread} recurses
1030 to the @code{set_thread_cmd_list}.
1034 To add commands in general, use @code{add_cmd}. @code{add_com} adds to
1035 the main command list, and should be used for those commands. The usual
1036 place to add commands is in the @code{_initialize_@var{xyz}} routines at
1037 the ends of most source files.
1039 @findex add_setshow_cmd
1040 @findex add_setshow_cmd_full
1041 To add paired @samp{set} and @samp{show} commands, use
1042 @code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is
1043 a slightly simpler interface which is useful when you don't need to
1044 further modify the new command structures, while the latter returns
1045 the new command structures for manipulation.
1047 @cindex deprecating commands
1048 @findex deprecate_cmd
1049 Before removing commands from the command set it is a good idea to
1050 deprecate them for some time. Use @code{deprecate_cmd} on commands or
1051 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
1052 @code{struct cmd_list_element} as it's first argument. You can use the
1053 return value from @code{add_com} or @code{add_cmd} to deprecate the
1054 command immediately after it is created.
1056 The first time a command is used the user will be warned and offered a
1057 replacement (if one exists). Note that the replacement string passed to
1058 @code{deprecate_cmd} should be the full name of the command, i.e., the
1059 entire string the user should type at the command line.
1061 @section UI-Independent Output---the @code{ui_out} Functions
1062 @c This section is based on the documentation written by Fernando
1063 @c Nasser <fnasser@redhat.com>.
1065 @cindex @code{ui_out} functions
1066 The @code{ui_out} functions present an abstraction level for the
1067 @value{GDBN} output code. They hide the specifics of different user
1068 interfaces supported by @value{GDBN}, and thus free the programmer
1069 from the need to write several versions of the same code, one each for
1070 every UI, to produce output.
1072 @subsection Overview and Terminology
1074 In general, execution of each @value{GDBN} command produces some sort
1075 of output, and can even generate an input request.
1077 Output can be generated for the following purposes:
1081 to display a @emph{result} of an operation;
1084 to convey @emph{info} or produce side-effects of a requested
1088 to provide a @emph{notification} of an asynchronous event (including
1089 progress indication of a prolonged asynchronous operation);
1092 to display @emph{error messages} (including warnings);
1095 to show @emph{debug data};
1098 to @emph{query} or prompt a user for input (a special case).
1102 This section mainly concentrates on how to build result output,
1103 although some of it also applies to other kinds of output.
1105 Generation of output that displays the results of an operation
1106 involves one or more of the following:
1110 output of the actual data
1113 formatting the output as appropriate for console output, to make it
1114 easily readable by humans
1117 machine oriented formatting--a more terse formatting to allow for easy
1118 parsing by programs which read @value{GDBN}'s output
1121 annotation, whose purpose is to help legacy GUIs to identify interesting
1125 The @code{ui_out} routines take care of the first three aspects.
1126 Annotations are provided by separate annotation routines. Note that use
1127 of annotations for an interface between a GUI and @value{GDBN} is
1130 Output can be in the form of a single item, which we call a @dfn{field};
1131 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
1132 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
1133 header and a body. In a BNF-like form:
1136 @item <table> @expansion{}
1137 @code{<header> <body>}
1138 @item <header> @expansion{}
1139 @code{@{ <column> @}}
1140 @item <column> @expansion{}
1141 @code{<width> <alignment> <title>}
1142 @item <body> @expansion{}
1147 @subsection General Conventions
1149 Most @code{ui_out} routines are of type @code{void}, the exceptions are
1150 @code{ui_out_stream_new} (which returns a pointer to the newly created
1151 object) and the @code{make_cleanup} routines.
1153 The first parameter is always the @code{ui_out} vector object, a pointer
1154 to a @code{struct ui_out}.
1156 The @var{format} parameter is like in @code{printf} family of functions.
1157 When it is present, there must also be a variable list of arguments
1158 sufficient used to satisfy the @code{%} specifiers in the supplied
1161 When a character string argument is not used in a @code{ui_out} function
1162 call, a @code{NULL} pointer has to be supplied instead.
1165 @subsection Table, Tuple and List Functions
1167 @cindex list output functions
1168 @cindex table output functions
1169 @cindex tuple output functions
1170 This section introduces @code{ui_out} routines for building lists,
1171 tuples and tables. The routines to output the actual data items
1172 (fields) are presented in the next section.
1174 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
1175 containing information about an object; a @dfn{list} is a sequence of
1176 fields where each field describes an identical object.
1178 Use the @dfn{table} functions when your output consists of a list of
1179 rows (tuples) and the console output should include a heading. Use this
1180 even when you are listing just one object but you still want the header.
1182 @cindex nesting level in @code{ui_out} functions
1183 Tables can not be nested. Tuples and lists can be nested up to a
1184 maximum of five levels.
1186 The overall structure of the table output code is something like this:
1201 Here is the description of table-, tuple- and list-related @code{ui_out}
1204 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
1205 The function @code{ui_out_table_begin} marks the beginning of the output
1206 of a table. It should always be called before any other @code{ui_out}
1207 function for a given table. @var{nbrofcols} is the number of columns in
1208 the table. @var{nr_rows} is the number of rows in the table.
1209 @var{tblid} is an optional string identifying the table. The string
1210 pointed to by @var{tblid} is copied by the implementation of
1211 @code{ui_out_table_begin}, so the application can free the string if it
1212 was @code{malloc}ed.
1214 The companion function @code{ui_out_table_end}, described below, marks
1215 the end of the table's output.
1218 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
1219 @code{ui_out_table_header} provides the header information for a single
1220 table column. You call this function several times, one each for every
1221 column of the table, after @code{ui_out_table_begin}, but before
1222 @code{ui_out_table_body}.
1224 The value of @var{width} gives the column width in characters. The
1225 value of @var{alignment} is one of @code{left}, @code{center}, and
1226 @code{right}, and it specifies how to align the header: left-justify,
1227 center, or right-justify it. @var{colhdr} points to a string that
1228 specifies the column header; the implementation copies that string, so
1229 column header strings in @code{malloc}ed storage can be freed after the
1233 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
1234 This function delimits the table header from the table body.
1237 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
1238 This function signals the end of a table's output. It should be called
1239 after the table body has been produced by the list and field output
1242 There should be exactly one call to @code{ui_out_table_end} for each
1243 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
1244 will signal an internal error.
1247 The output of the tuples that represent the table rows must follow the
1248 call to @code{ui_out_table_body} and precede the call to
1249 @code{ui_out_table_end}. You build a tuple by calling
1250 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
1251 calls to functions which actually output fields between them.
1253 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
1254 This function marks the beginning of a tuple output. @var{id} points
1255 to an optional string that identifies the tuple; it is copied by the
1256 implementation, and so strings in @code{malloc}ed storage can be freed
1260 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
1261 This function signals an end of a tuple output. There should be exactly
1262 one call to @code{ui_out_tuple_end} for each call to
1263 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
1267 @deftypefun struct cleanup *make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1268 This function first opens the tuple and then establishes a cleanup
1269 (@pxref{Coding, Cleanups}) to close the tuple. It provides a convenient
1270 and correct implementation of the non-portable@footnote{The function
1271 cast is not portable ISO C.} code sequence:
1273 struct cleanup *old_cleanup;
1274 ui_out_tuple_begin (uiout, "...");
1275 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
1280 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
1281 This function marks the beginning of a list output. @var{id} points to
1282 an optional string that identifies the list; it is copied by the
1283 implementation, and so strings in @code{malloc}ed storage can be freed
1287 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
1288 This function signals an end of a list output. There should be exactly
1289 one call to @code{ui_out_list_end} for each call to
1290 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
1294 @deftypefun struct cleanup *make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1295 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
1296 opens a list and then establishes cleanup (@pxref{Coding, Cleanups})
1297 that will close the list.list.
1300 @subsection Item Output Functions
1302 @cindex item output functions
1303 @cindex field output functions
1305 The functions described below produce output for the actual data
1306 items, or fields, which contain information about the object.
1308 Choose the appropriate function accordingly to your particular needs.
1310 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
1311 This is the most general output function. It produces the
1312 representation of the data in the variable-length argument list
1313 according to formatting specifications in @var{format}, a
1314 @code{printf}-like format string. The optional argument @var{fldname}
1315 supplies the name of the field. The data items themselves are
1316 supplied as additional arguments after @var{format}.
1318 This generic function should be used only when it is not possible to
1319 use one of the specialized versions (see below).
1322 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1323 This function outputs a value of an @code{int} variable. It uses the
1324 @code{"%d"} output conversion specification. @var{fldname} specifies
1325 the name of the field.
1328 @deftypefun void ui_out_field_fmt_int (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{fldname}, int @var{value})
1329 This function outputs a value of an @code{int} variable. It differs from
1330 @code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output.
1331 @var{fldname} specifies
1332 the name of the field.
1335 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, CORE_ADDR @var{address})
1336 This function outputs an address.
1339 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1340 This function outputs a string using the @code{"%s"} conversion
1344 Sometimes, there's a need to compose your output piece by piece using
1345 functions that operate on a stream, such as @code{value_print} or
1346 @code{fprintf_symbol_filtered}. These functions accept an argument of
1347 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1348 used to store the data stream used for the output. When you use one
1349 of these functions, you need a way to pass their results stored in a
1350 @code{ui_file} object to the @code{ui_out} functions. To this end,
1351 you first create a @code{ui_stream} object by calling
1352 @code{ui_out_stream_new}, pass the @code{stream} member of that
1353 @code{ui_stream} object to @code{value_print} and similar functions,
1354 and finally call @code{ui_out_field_stream} to output the field you
1355 constructed. When the @code{ui_stream} object is no longer needed,
1356 you should destroy it and free its memory by calling
1357 @code{ui_out_stream_delete}.
1359 @deftypefun struct ui_stream *ui_out_stream_new (struct ui_out *@var{uiout})
1360 This function creates a new @code{ui_stream} object which uses the
1361 same output methods as the @code{ui_out} object whose pointer is
1362 passed in @var{uiout}. It returns a pointer to the newly created
1363 @code{ui_stream} object.
1366 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1367 This functions destroys a @code{ui_stream} object specified by
1371 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1372 This function consumes all the data accumulated in
1373 @code{streambuf->stream} and outputs it like
1374 @code{ui_out_field_string} does. After a call to
1375 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1376 the stream is still valid and may be used for producing more fields.
1379 @strong{Important:} If there is any chance that your code could bail
1380 out before completing output generation and reaching the point where
1381 @code{ui_out_stream_delete} is called, it is necessary to set up a
1382 cleanup, to avoid leaking memory and other resources. Here's a
1383 skeleton code to do that:
1386 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1387 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1392 If the function already has the old cleanup chain set (for other kinds
1393 of cleanups), you just have to add your cleanup to it:
1396 mybuf = ui_out_stream_new (uiout);
1397 make_cleanup (ui_out_stream_delete, mybuf);
1400 Note that with cleanups in place, you should not call
1401 @code{ui_out_stream_delete} directly, or you would attempt to free the
1404 @subsection Utility Output Functions
1406 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1407 This function skips a field in a table. Use it if you have to leave
1408 an empty field without disrupting the table alignment. The argument
1409 @var{fldname} specifies a name for the (missing) filed.
1412 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1413 This function outputs the text in @var{string} in a way that makes it
1414 easy to be read by humans. For example, the console implementation of
1415 this method filters the text through a built-in pager, to prevent it
1416 from scrolling off the visible portion of the screen.
1418 Use this function for printing relatively long chunks of text around
1419 the actual field data: the text it produces is not aligned according
1420 to the table's format. Use @code{ui_out_field_string} to output a
1421 string field, and use @code{ui_out_message}, described below, to
1422 output short messages.
1425 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1426 This function outputs @var{nspaces} spaces. It is handy to align the
1427 text produced by @code{ui_out_text} with the rest of the table or
1431 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1432 This function produces a formatted message, provided that the current
1433 verbosity level is at least as large as given by @var{verbosity}. The
1434 current verbosity level is specified by the user with the @samp{set
1435 verbositylevel} command.@footnote{As of this writing (April 2001),
1436 setting verbosity level is not yet implemented, and is always returned
1437 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1438 argument more than zero will cause the message to never be printed.}
1441 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1442 This function gives the console output filter (a paging filter) a hint
1443 of where to break lines which are too long. Ignored for all other
1444 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1445 be printed to indent the wrapped text on the next line; it must remain
1446 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1447 explicit newline is produced by one of the other functions. If
1448 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1451 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1452 This function flushes whatever output has been accumulated so far, if
1453 the UI buffers output.
1457 @subsection Examples of Use of @code{ui_out} functions
1459 @cindex using @code{ui_out} functions
1460 @cindex @code{ui_out} functions, usage examples
1461 This section gives some practical examples of using the @code{ui_out}
1462 functions to generalize the old console-oriented code in
1463 @value{GDBN}. The examples all come from functions defined on the
1464 @file{breakpoints.c} file.
1466 This example, from the @code{breakpoint_1} function, shows how to
1469 The original code was:
1472 if (!found_a_breakpoint++)
1474 annotate_breakpoints_headers ();
1477 printf_filtered ("Num ");
1479 printf_filtered ("Type ");
1481 printf_filtered ("Disp ");
1483 printf_filtered ("Enb ");
1487 printf_filtered ("Address ");
1490 printf_filtered ("What\n");
1492 annotate_breakpoints_table ();
1496 Here's the new version:
1499 nr_printable_breakpoints = @dots{};
1502 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1504 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1506 if (nr_printable_breakpoints > 0)
1507 annotate_breakpoints_headers ();
1508 if (nr_printable_breakpoints > 0)
1510 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1511 if (nr_printable_breakpoints > 0)
1513 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1514 if (nr_printable_breakpoints > 0)
1516 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1517 if (nr_printable_breakpoints > 0)
1519 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1522 if (nr_printable_breakpoints > 0)
1524 if (TARGET_ADDR_BIT <= 32)
1525 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1527 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1529 if (nr_printable_breakpoints > 0)
1531 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1532 ui_out_table_body (uiout);
1533 if (nr_printable_breakpoints > 0)
1534 annotate_breakpoints_table ();
1537 This example, from the @code{print_one_breakpoint} function, shows how
1538 to produce the actual data for the table whose structure was defined
1539 in the above example. The original code was:
1544 printf_filtered ("%-3d ", b->number);
1546 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1547 || ((int) b->type != bptypes[(int) b->type].type))
1548 internal_error ("bptypes table does not describe type #%d.",
1550 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1552 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1554 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1558 This is the new version:
1562 ui_out_tuple_begin (uiout, "bkpt");
1564 ui_out_field_int (uiout, "number", b->number);
1566 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1567 || ((int) b->type != bptypes[(int) b->type].type))
1568 internal_error ("bptypes table does not describe type #%d.",
1570 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1572 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1574 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1578 This example, also from @code{print_one_breakpoint}, shows how to
1579 produce a complicated output field using the @code{print_expression}
1580 functions which requires a stream to be passed. It also shows how to
1581 automate stream destruction with cleanups. The original code was:
1585 print_expression (b->exp, gdb_stdout);
1591 struct ui_stream *stb = ui_out_stream_new (uiout);
1592 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1595 print_expression (b->exp, stb->stream);
1596 ui_out_field_stream (uiout, "what", local_stream);
1599 This example, also from @code{print_one_breakpoint}, shows how to use
1600 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1605 if (b->dll_pathname == NULL)
1606 printf_filtered ("<any library> ");
1608 printf_filtered ("library \"%s\" ", b->dll_pathname);
1615 if (b->dll_pathname == NULL)
1617 ui_out_field_string (uiout, "what", "<any library>");
1618 ui_out_spaces (uiout, 1);
1622 ui_out_text (uiout, "library \"");
1623 ui_out_field_string (uiout, "what", b->dll_pathname);
1624 ui_out_text (uiout, "\" ");
1628 The following example from @code{print_one_breakpoint} shows how to
1629 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1634 if (b->forked_inferior_pid != 0)
1635 printf_filtered ("process %d ", b->forked_inferior_pid);
1642 if (b->forked_inferior_pid != 0)
1644 ui_out_text (uiout, "process ");
1645 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1646 ui_out_spaces (uiout, 1);
1650 Here's an example of using @code{ui_out_field_string}. The original
1655 if (b->exec_pathname != NULL)
1656 printf_filtered ("program \"%s\" ", b->exec_pathname);
1663 if (b->exec_pathname != NULL)
1665 ui_out_text (uiout, "program \"");
1666 ui_out_field_string (uiout, "what", b->exec_pathname);
1667 ui_out_text (uiout, "\" ");
1671 Finally, here's an example of printing an address. The original code:
1675 printf_filtered ("%s ",
1676 hex_string_custom ((unsigned long) b->address, 8));
1683 ui_out_field_core_addr (uiout, "Address", b->address);
1687 @section Console Printing
1696 @cindex @code{libgdb}
1697 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1698 to provide an API to @value{GDBN}'s functionality.
1701 @cindex @code{libgdb}
1702 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1703 better able to support graphical and other environments.
1705 Since @code{libgdb} development is on-going, its architecture is still
1706 evolving. The following components have so far been identified:
1710 Observer - @file{gdb-events.h}.
1712 Builder - @file{ui-out.h}
1714 Event Loop - @file{event-loop.h}
1716 Library - @file{gdb.h}
1719 The model that ties these components together is described below.
1721 @section The @code{libgdb} Model
1723 A client of @code{libgdb} interacts with the library in two ways.
1727 As an observer (using @file{gdb-events}) receiving notifications from
1728 @code{libgdb} of any internal state changes (break point changes, run
1731 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1732 obtain various status values from @value{GDBN}.
1735 Since @code{libgdb} could have multiple clients (e.g., a GUI supporting
1736 the existing @value{GDBN} CLI), those clients must co-operate when
1737 controlling @code{libgdb}. In particular, a client must ensure that
1738 @code{libgdb} is idle (i.e. no other client is using @code{libgdb})
1739 before responding to a @file{gdb-event} by making a query.
1741 @section CLI support
1743 At present @value{GDBN}'s CLI is very much entangled in with the core of
1744 @code{libgdb}. Consequently, a client wishing to include the CLI in
1745 their interface needs to carefully co-ordinate its own and the CLI's
1748 It is suggested that the client set @code{libgdb} up to be bi-modal
1749 (alternate between CLI and client query modes). The notes below sketch
1754 The client registers itself as an observer of @code{libgdb}.
1756 The client create and install @code{cli-out} builder using its own
1757 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1758 @code{gdb_stdout} streams.
1760 The client creates a separate custom @code{ui-out} builder that is only
1761 used while making direct queries to @code{libgdb}.
1764 When the client receives input intended for the CLI, it simply passes it
1765 along. Since the @code{cli-out} builder is installed by default, all
1766 the CLI output in response to that command is routed (pronounced rooted)
1767 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1768 At the same time, the client is kept abreast of internal changes by
1769 virtue of being a @code{libgdb} observer.
1771 The only restriction on the client is that it must wait until
1772 @code{libgdb} becomes idle before initiating any queries (using the
1773 client's custom builder).
1775 @section @code{libgdb} components
1777 @subheading Observer - @file{gdb-events.h}
1778 @file{gdb-events} provides the client with a very raw mechanism that can
1779 be used to implement an observer. At present it only allows for one
1780 observer and that observer must, internally, handle the need to delay
1781 the processing of any event notifications until after @code{libgdb} has
1782 finished the current command.
1784 @subheading Builder - @file{ui-out.h}
1785 @file{ui-out} provides the infrastructure necessary for a client to
1786 create a builder. That builder is then passed down to @code{libgdb}
1787 when doing any queries.
1789 @subheading Event Loop - @file{event-loop.h}
1790 @c There could be an entire section on the event-loop
1791 @file{event-loop}, currently non-re-entrant, provides a simple event
1792 loop. A client would need to either plug its self into this loop or,
1793 implement a new event-loop that GDB would use.
1795 The event-loop will eventually be made re-entrant. This is so that
1796 @value{GDBN} can better handle the problem of some commands blocking
1797 instead of returning.
1799 @subheading Library - @file{gdb.h}
1800 @file{libgdb} is the most obvious component of this system. It provides
1801 the query interface. Each function is parameterized by a @code{ui-out}
1802 builder. The result of the query is constructed using that builder
1803 before the query function returns.
1805 @node Symbol Handling
1807 @chapter Symbol Handling
1809 Symbols are a key part of @value{GDBN}'s operation. Symbols include variables,
1810 functions, and types.
1812 @section Symbol Reading
1814 @cindex symbol reading
1815 @cindex reading of symbols
1816 @cindex symbol files
1817 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
1818 file is the file containing the program which @value{GDBN} is
1819 debugging. @value{GDBN} can be directed to use a different file for
1820 symbols (with the @samp{symbol-file} command), and it can also read
1821 more symbols via the @samp{add-file} and @samp{load} commands, or while
1822 reading symbols from shared libraries.
1824 @findex find_sym_fns
1825 Symbol files are initially opened by code in @file{symfile.c} using
1826 the BFD library (@pxref{Support Libraries}). BFD identifies the type
1827 of the file by examining its header. @code{find_sym_fns} then uses
1828 this identification to locate a set of symbol-reading functions.
1830 @findex add_symtab_fns
1831 @cindex @code{sym_fns} structure
1832 @cindex adding a symbol-reading module
1833 Symbol-reading modules identify themselves to @value{GDBN} by calling
1834 @code{add_symtab_fns} during their module initialization. The argument
1835 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
1836 name (or name prefix) of the symbol format, the length of the prefix,
1837 and pointers to four functions. These functions are called at various
1838 times to process symbol files whose identification matches the specified
1841 The functions supplied by each module are:
1844 @item @var{xyz}_symfile_init(struct sym_fns *sf)
1846 @cindex secondary symbol file
1847 Called from @code{symbol_file_add} when we are about to read a new
1848 symbol file. This function should clean up any internal state (possibly
1849 resulting from half-read previous files, for example) and prepare to
1850 read a new symbol file. Note that the symbol file which we are reading
1851 might be a new ``main'' symbol file, or might be a secondary symbol file
1852 whose symbols are being added to the existing symbol table.
1854 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
1855 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
1856 new symbol file being read. Its @code{private} field has been zeroed,
1857 and can be modified as desired. Typically, a struct of private
1858 information will be @code{malloc}'d, and a pointer to it will be placed
1859 in the @code{private} field.
1861 There is no result from @code{@var{xyz}_symfile_init}, but it can call
1862 @code{error} if it detects an unavoidable problem.
1864 @item @var{xyz}_new_init()
1866 Called from @code{symbol_file_add} when discarding existing symbols.
1867 This function needs only handle the symbol-reading module's internal
1868 state; the symbol table data structures visible to the rest of
1869 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
1870 arguments and no result. It may be called after
1871 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
1872 may be called alone if all symbols are simply being discarded.
1874 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
1876 Called from @code{symbol_file_add} to actually read the symbols from a
1877 symbol-file into a set of psymtabs or symtabs.
1879 @code{sf} points to the @code{struct sym_fns} originally passed to
1880 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
1881 the offset between the file's specified start address and its true
1882 address in memory. @code{mainline} is 1 if this is the main symbol
1883 table being read, and 0 if a secondary symbol file (e.g., shared library
1884 or dynamically loaded file) is being read.@refill
1887 In addition, if a symbol-reading module creates psymtabs when
1888 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
1889 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
1890 from any point in the @value{GDBN} symbol-handling code.
1893 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
1895 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
1896 the psymtab has not already been read in and had its @code{pst->symtab}
1897 pointer set. The argument is the psymtab to be fleshed-out into a
1898 symtab. Upon return, @code{pst->readin} should have been set to 1, and
1899 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
1900 zero if there were no symbols in that part of the symbol file.
1903 @section Partial Symbol Tables
1905 @value{GDBN} has three types of symbol tables:
1908 @cindex full symbol table
1911 Full symbol tables (@dfn{symtabs}). These contain the main
1912 information about symbols and addresses.
1916 Partial symbol tables (@dfn{psymtabs}). These contain enough
1917 information to know when to read the corresponding part of the full
1920 @cindex minimal symbol table
1923 Minimal symbol tables (@dfn{msymtabs}). These contain information
1924 gleaned from non-debugging symbols.
1927 @cindex partial symbol table
1928 This section describes partial symbol tables.
1930 A psymtab is constructed by doing a very quick pass over an executable
1931 file's debugging information. Small amounts of information are
1932 extracted---enough to identify which parts of the symbol table will
1933 need to be re-read and fully digested later, when the user needs the
1934 information. The speed of this pass causes @value{GDBN} to start up very
1935 quickly. Later, as the detailed rereading occurs, it occurs in small
1936 pieces, at various times, and the delay therefrom is mostly invisible to
1938 @c (@xref{Symbol Reading}.)
1940 The symbols that show up in a file's psymtab should be, roughly, those
1941 visible to the debugger's user when the program is not running code from
1942 that file. These include external symbols and types, static symbols and
1943 types, and @code{enum} values declared at file scope.
1945 The psymtab also contains the range of instruction addresses that the
1946 full symbol table would represent.
1948 @cindex finding a symbol
1949 @cindex symbol lookup
1950 The idea is that there are only two ways for the user (or much of the
1951 code in the debugger) to reference a symbol:
1954 @findex find_pc_function
1955 @findex find_pc_line
1957 By its address (e.g., execution stops at some address which is inside a
1958 function in this file). The address will be noticed to be in the
1959 range of this psymtab, and the full symtab will be read in.
1960 @code{find_pc_function}, @code{find_pc_line}, and other
1961 @code{find_pc_@dots{}} functions handle this.
1963 @cindex lookup_symbol
1966 (e.g., the user asks to print a variable, or set a breakpoint on a
1967 function). Global names and file-scope names will be found in the
1968 psymtab, which will cause the symtab to be pulled in. Local names will
1969 have to be qualified by a global name, or a file-scope name, in which
1970 case we will have already read in the symtab as we evaluated the
1971 qualifier. Or, a local symbol can be referenced when we are ``in'' a
1972 local scope, in which case the first case applies. @code{lookup_symbol}
1973 does most of the work here.
1976 The only reason that psymtabs exist is to cause a symtab to be read in
1977 at the right moment. Any symbol that can be elided from a psymtab,
1978 while still causing that to happen, should not appear in it. Since
1979 psymtabs don't have the idea of scope, you can't put local symbols in
1980 them anyway. Psymtabs don't have the idea of the type of a symbol,
1981 either, so types need not appear, unless they will be referenced by
1984 It is a bug for @value{GDBN} to behave one way when only a psymtab has
1985 been read, and another way if the corresponding symtab has been read
1986 in. Such bugs are typically caused by a psymtab that does not contain
1987 all the visible symbols, or which has the wrong instruction address
1990 The psymtab for a particular section of a symbol file (objfile) could be
1991 thrown away after the symtab has been read in. The symtab should always
1992 be searched before the psymtab, so the psymtab will never be used (in a
1993 bug-free environment). Currently, psymtabs are allocated on an obstack,
1994 and all the psymbols themselves are allocated in a pair of large arrays
1995 on an obstack, so there is little to be gained by trying to free them
1996 unless you want to do a lot more work.
2000 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
2002 @cindex fundamental types
2003 These are the fundamental types that @value{GDBN} uses internally. Fundamental
2004 types from the various debugging formats (stabs, ELF, etc) are mapped
2005 into one of these. They are basically a union of all fundamental types
2006 that @value{GDBN} knows about for all the languages that @value{GDBN}
2009 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
2012 Each time @value{GDBN} builds an internal type, it marks it with one
2013 of these types. The type may be a fundamental type, such as
2014 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
2015 which is a pointer to another type. Typically, several @code{FT_*}
2016 types map to one @code{TYPE_CODE_*} type, and are distinguished by
2017 other members of the type struct, such as whether the type is signed
2018 or unsigned, and how many bits it uses.
2020 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
2022 These are instances of type structs that roughly correspond to
2023 fundamental types and are created as global types for @value{GDBN} to
2024 use for various ugly historical reasons. We eventually want to
2025 eliminate these. Note for example that @code{builtin_type_int}
2026 initialized in @file{gdbtypes.c} is basically the same as a
2027 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
2028 an @code{FT_INTEGER} fundamental type. The difference is that the
2029 @code{builtin_type} is not associated with any particular objfile, and
2030 only one instance exists, while @file{c-lang.c} builds as many
2031 @code{TYPE_CODE_INT} types as needed, with each one associated with
2032 some particular objfile.
2034 @section Object File Formats
2035 @cindex object file formats
2039 @cindex @code{a.out} format
2040 The @code{a.out} format is the original file format for Unix. It
2041 consists of three sections: @code{text}, @code{data}, and @code{bss},
2042 which are for program code, initialized data, and uninitialized data,
2045 The @code{a.out} format is so simple that it doesn't have any reserved
2046 place for debugging information. (Hey, the original Unix hackers used
2047 @samp{adb}, which is a machine-language debugger!) The only debugging
2048 format for @code{a.out} is stabs, which is encoded as a set of normal
2049 symbols with distinctive attributes.
2051 The basic @code{a.out} reader is in @file{dbxread.c}.
2056 The COFF format was introduced with System V Release 3 (SVR3) Unix.
2057 COFF files may have multiple sections, each prefixed by a header. The
2058 number of sections is limited.
2060 The COFF specification includes support for debugging. Although this
2061 was a step forward, the debugging information was woefully limited. For
2062 instance, it was not possible to represent code that came from an
2065 The COFF reader is in @file{coffread.c}.
2069 @cindex ECOFF format
2070 ECOFF is an extended COFF originally introduced for Mips and Alpha
2073 The basic ECOFF reader is in @file{mipsread.c}.
2077 @cindex XCOFF format
2078 The IBM RS/6000 running AIX uses an object file format called XCOFF.
2079 The COFF sections, symbols, and line numbers are used, but debugging
2080 symbols are @code{dbx}-style stabs whose strings are located in the
2081 @code{.debug} section (rather than the string table). For more
2082 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
2084 The shared library scheme has a clean interface for figuring out what
2085 shared libraries are in use, but the catch is that everything which
2086 refers to addresses (symbol tables and breakpoints at least) needs to be
2087 relocated for both shared libraries and the main executable. At least
2088 using the standard mechanism this can only be done once the program has
2089 been run (or the core file has been read).
2093 @cindex PE-COFF format
2094 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
2095 executables. PE is basically COFF with additional headers.
2097 While BFD includes special PE support, @value{GDBN} needs only the basic
2103 The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
2104 to COFF in being organized into a number of sections, but it removes
2105 many of COFF's limitations.
2107 The basic ELF reader is in @file{elfread.c}.
2112 SOM is HP's object file and debug format (not to be confused with IBM's
2113 SOM, which is a cross-language ABI).
2115 The SOM reader is in @file{hpread.c}.
2117 @subsection Other File Formats
2119 @cindex Netware Loadable Module format
2120 Other file formats that have been supported by @value{GDBN} include Netware
2121 Loadable Modules (@file{nlmread.c}).
2123 @section Debugging File Formats
2125 This section describes characteristics of debugging information that
2126 are independent of the object file format.
2130 @cindex stabs debugging info
2131 @code{stabs} started out as special symbols within the @code{a.out}
2132 format. Since then, it has been encapsulated into other file
2133 formats, such as COFF and ELF.
2135 While @file{dbxread.c} does some of the basic stab processing,
2136 including for encapsulated versions, @file{stabsread.c} does
2141 @cindex COFF debugging info
2142 The basic COFF definition includes debugging information. The level
2143 of support is minimal and non-extensible, and is not often used.
2145 @subsection Mips debug (Third Eye)
2147 @cindex ECOFF debugging info
2148 ECOFF includes a definition of a special debug format.
2150 The file @file{mdebugread.c} implements reading for this format.
2154 @cindex DWARF 1 debugging info
2155 DWARF 1 is a debugging format that was originally designed to be
2156 used with ELF in SVR4 systems.
2161 @c If defined, these are the producer strings in a DWARF 1 file. All of
2162 @c these have reasonable defaults already.
2164 The DWARF 1 reader is in @file{dwarfread.c}.
2168 @cindex DWARF 2 debugging info
2169 DWARF 2 is an improved but incompatible version of DWARF 1.
2171 The DWARF 2 reader is in @file{dwarf2read.c}.
2175 @cindex SOM debugging info
2176 Like COFF, the SOM definition includes debugging information.
2178 @section Adding a New Symbol Reader to @value{GDBN}
2180 @cindex adding debugging info reader
2181 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
2182 there is probably little to be done.
2184 If you need to add a new object file format, you must first add it to
2185 BFD. This is beyond the scope of this document.
2187 You must then arrange for the BFD code to provide access to the
2188 debugging symbols. Generally @value{GDBN} will have to call swapping routines
2189 from BFD and a few other BFD internal routines to locate the debugging
2190 information. As much as possible, @value{GDBN} should not depend on the BFD
2191 internal data structures.
2193 For some targets (e.g., COFF), there is a special transfer vector used
2194 to call swapping routines, since the external data structures on various
2195 platforms have different sizes and layouts. Specialized routines that
2196 will only ever be implemented by one object file format may be called
2197 directly. This interface should be described in a file
2198 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
2200 @section Memory Management for Symbol Files
2202 Most memory associated with a loaded symbol file is stored on
2203 its @code{objfile_obstack}. This includes symbols, types,
2204 namespace data, and other information produced by the symbol readers.
2206 Because this data lives on the objfile's obstack, it is automatically
2207 released when the objfile is unloaded or reloaded. Therefore one
2208 objfile must not reference symbol or type data from another objfile;
2209 they could be unloaded at different times.
2211 User convenience variables, et cetera, have associated types. Normally
2212 these types live in the associated objfile. However, when the objfile
2213 is unloaded, those types are deep copied to global memory, so that
2214 the values of the user variables and history items are not lost.
2217 @node Language Support
2219 @chapter Language Support
2221 @cindex language support
2222 @value{GDBN}'s language support is mainly driven by the symbol reader,
2223 although it is possible for the user to set the source language
2226 @value{GDBN} chooses the source language by looking at the extension
2227 of the file recorded in the debug info; @file{.c} means C, @file{.f}
2228 means Fortran, etc. It may also use a special-purpose language
2229 identifier if the debug format supports it, like with DWARF.
2231 @section Adding a Source Language to @value{GDBN}
2233 @cindex adding source language
2234 To add other languages to @value{GDBN}'s expression parser, follow the
2238 @item Create the expression parser.
2240 @cindex expression parser
2241 This should reside in a file @file{@var{lang}-exp.y}. Routines for
2242 building parsed expressions into a @code{union exp_element} list are in
2245 @cindex language parser
2246 Since we can't depend upon everyone having Bison, and YACC produces
2247 parsers that define a bunch of global names, the following lines
2248 @strong{must} be included at the top of the YACC parser, to prevent the
2249 various parsers from defining the same global names:
2252 #define yyparse @var{lang}_parse
2253 #define yylex @var{lang}_lex
2254 #define yyerror @var{lang}_error
2255 #define yylval @var{lang}_lval
2256 #define yychar @var{lang}_char
2257 #define yydebug @var{lang}_debug
2258 #define yypact @var{lang}_pact
2259 #define yyr1 @var{lang}_r1
2260 #define yyr2 @var{lang}_r2
2261 #define yydef @var{lang}_def
2262 #define yychk @var{lang}_chk
2263 #define yypgo @var{lang}_pgo
2264 #define yyact @var{lang}_act
2265 #define yyexca @var{lang}_exca
2266 #define yyerrflag @var{lang}_errflag
2267 #define yynerrs @var{lang}_nerrs
2270 At the bottom of your parser, define a @code{struct language_defn} and
2271 initialize it with the right values for your language. Define an
2272 @code{initialize_@var{lang}} routine and have it call
2273 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
2274 that your language exists. You'll need some other supporting variables
2275 and functions, which will be used via pointers from your
2276 @code{@var{lang}_language_defn}. See the declaration of @code{struct
2277 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
2278 for more information.
2280 @item Add any evaluation routines, if necessary
2282 @cindex expression evaluation routines
2283 @findex evaluate_subexp
2284 @findex prefixify_subexp
2285 @findex length_of_subexp
2286 If you need new opcodes (that represent the operations of the language),
2287 add them to the enumerated type in @file{expression.h}. Add support
2288 code for these operations in the @code{evaluate_subexp} function
2289 defined in the file @file{eval.c}. Add cases
2290 for new opcodes in two functions from @file{parse.c}:
2291 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
2292 the number of @code{exp_element}s that a given operation takes up.
2294 @item Update some existing code
2296 Add an enumerated identifier for your language to the enumerated type
2297 @code{enum language} in @file{defs.h}.
2299 Update the routines in @file{language.c} so your language is included.
2300 These routines include type predicates and such, which (in some cases)
2301 are language dependent. If your language does not appear in the switch
2302 statement, an error is reported.
2304 @vindex current_language
2305 Also included in @file{language.c} is the code that updates the variable
2306 @code{current_language}, and the routines that translate the
2307 @code{language_@var{lang}} enumerated identifier into a printable
2310 @findex _initialize_language
2311 Update the function @code{_initialize_language} to include your
2312 language. This function picks the default language upon startup, so is
2313 dependent upon which languages that @value{GDBN} is built for.
2315 @findex allocate_symtab
2316 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
2317 code so that the language of each symtab (source file) is set properly.
2318 This is used to determine the language to use at each stack frame level.
2319 Currently, the language is set based upon the extension of the source
2320 file. If the language can be better inferred from the symbol
2321 information, please set the language of the symtab in the symbol-reading
2324 @findex print_subexp
2325 @findex op_print_tab
2326 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
2327 expression opcodes you have added to @file{expression.h}. Also, add the
2328 printed representations of your operators to @code{op_print_tab}.
2330 @item Add a place of call
2333 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2334 @code{parse_exp_1} (defined in @file{parse.c}).
2336 @item Use macros to trim code
2338 @cindex trimming language-dependent code
2339 The user has the option of building @value{GDBN} for some or all of the
2340 languages. If the user decides to build @value{GDBN} for the language
2341 @var{lang}, then every file dependent on @file{language.h} will have the
2342 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2343 leave out large routines that the user won't need if he or she is not
2344 using your language.
2346 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2347 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2348 compiled form of your parser) is not linked into @value{GDBN} at all.
2350 See the file @file{configure.in} for how @value{GDBN} is configured
2351 for different languages.
2353 @item Edit @file{Makefile.in}
2355 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2356 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2357 not get linked in, or, worse yet, it may not get @code{tar}red into the
2362 @node Host Definition
2364 @chapter Host Definition
2366 With the advent of Autoconf, it's rarely necessary to have host
2367 definition machinery anymore. The following information is provided,
2368 mainly, as an historical reference.
2370 @section Adding a New Host
2372 @cindex adding a new host
2373 @cindex host, adding
2374 @value{GDBN}'s host configuration support normally happens via Autoconf.
2375 New host-specific definitions should not be needed. Older hosts
2376 @value{GDBN} still use the host-specific definitions and files listed
2377 below, but these mostly exist for historical reasons, and will
2378 eventually disappear.
2381 @item gdb/config/@var{arch}/@var{xyz}.mh
2382 This file once contained both host and native configuration information
2383 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2384 configuration information is now handed by Autoconf.
2386 Host configuration information included a definition of
2387 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2388 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2389 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2391 New host only configurations do not need this file.
2393 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2394 This file once contained definitions and includes required when hosting
2395 gdb on machine @var{xyz}. Those definitions and includes are now
2396 handled by Autoconf.
2398 New host and native configurations do not need this file.
2400 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2401 file to define the macros @var{HOST_FLOAT_FORMAT},
2402 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2403 also needs to be replaced with either an Autoconf or run-time test.}
2407 @subheading Generic Host Support Files
2409 @cindex generic host support
2410 There are some ``generic'' versions of routines that can be used by
2411 various systems. These can be customized in various ways by macros
2412 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2413 the @var{xyz} host, you can just include the generic file's name (with
2414 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2416 Otherwise, if your machine needs custom support routines, you will need
2417 to write routines that perform the same functions as the generic file.
2418 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2419 into @code{XDEPFILES}.
2422 @cindex remote debugging support
2423 @cindex serial line support
2425 This contains serial line support for Unix systems. This is always
2426 included, via the makefile variable @code{SER_HARDWIRE}; override this
2427 variable in the @file{.mh} file to avoid it.
2430 This contains serial line support for 32-bit programs running under DOS,
2431 using the DJGPP (a.k.a.@: GO32) execution environment.
2433 @cindex TCP remote support
2435 This contains generic TCP support using sockets.
2438 @section Host Conditionals
2440 When @value{GDBN} is configured and compiled, various macros are
2441 defined or left undefined, to control compilation based on the
2442 attributes of the host system. These macros and their meanings (or if
2443 the meaning is not documented here, then one of the source files where
2444 they are used is indicated) are:
2447 @item @value{GDBN}INIT_FILENAME
2448 The default name of @value{GDBN}'s initialization file (normally
2452 This macro is deprecated.
2454 @item SIGWINCH_HANDLER
2455 If your host defines @code{SIGWINCH}, you can define this to be the name
2456 of a function to be called if @code{SIGWINCH} is received.
2458 @item SIGWINCH_HANDLER_BODY
2459 Define this to expand into code that will define the function named by
2460 the expansion of @code{SIGWINCH_HANDLER}.
2462 @item ALIGN_STACK_ON_STARTUP
2463 @cindex stack alignment
2464 Define this if your system is of a sort that will crash in
2465 @code{tgetent} if the stack happens not to be longword-aligned when
2466 @code{main} is called. This is a rare situation, but is known to occur
2467 on several different types of systems.
2469 @item CRLF_SOURCE_FILES
2470 @cindex DOS text files
2471 Define this if host files use @code{\r\n} rather than @code{\n} as a
2472 line terminator. This will cause source file listings to omit @code{\r}
2473 characters when printing and it will allow @code{\r\n} line endings of files
2474 which are ``sourced'' by gdb. It must be possible to open files in binary
2475 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2477 @item DEFAULT_PROMPT
2479 The default value of the prompt string (normally @code{"(gdb) "}).
2482 @cindex terminal device
2483 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2486 Define this if binary files are opened the same way as text files.
2490 In some cases, use the system call @code{mmap} for reading symbol
2491 tables. For some machines this allows for sharing and quick updates.
2494 Define this if the host system has @code{termio.h}.
2501 Values for host-side constants.
2504 Substitute for isatty, if not available.
2507 This is the longest integer type available on the host. If not defined,
2508 it will default to @code{long long} or @code{long}, depending on
2509 @code{CC_HAS_LONG_LONG}.
2511 @item CC_HAS_LONG_LONG
2512 @cindex @code{long long} data type
2513 Define this if the host C compiler supports @code{long long}. This is set
2514 by the @code{configure} script.
2516 @item PRINTF_HAS_LONG_LONG
2517 Define this if the host can handle printing of long long integers via
2518 the printf format conversion specifier @code{ll}. This is set by the
2519 @code{configure} script.
2521 @item HAVE_LONG_DOUBLE
2522 Define this if the host C compiler supports @code{long double}. This is
2523 set by the @code{configure} script.
2525 @item PRINTF_HAS_LONG_DOUBLE
2526 Define this if the host can handle printing of long double float-point
2527 numbers via the printf format conversion specifier @code{Lg}. This is
2528 set by the @code{configure} script.
2530 @item SCANF_HAS_LONG_DOUBLE
2531 Define this if the host can handle the parsing of long double
2532 float-point numbers via the scanf format conversion specifier
2533 @code{Lg}. This is set by the @code{configure} script.
2535 @item LSEEK_NOT_LINEAR
2536 Define this if @code{lseek (n)} does not necessarily move to byte number
2537 @code{n} in the file. This is only used when reading source files. It
2538 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2541 This macro is used as the argument to @code{lseek} (or, most commonly,
2542 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2543 which is the POSIX equivalent.
2546 If defined, this should be one or more tokens, such as @code{volatile},
2547 that can be used in both the declaration and definition of functions to
2548 indicate that they never return. The default is already set correctly
2549 if compiling with GCC. This will almost never need to be defined.
2552 If defined, this should be one or more tokens, such as
2553 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2554 of functions to indicate that they never return. The default is already
2555 set correctly if compiling with GCC. This will almost never need to be
2560 Define these to appropriate value for the system @code{lseek}, if not already
2564 This is the signal for stopping @value{GDBN}. Defaults to
2565 @code{SIGTSTP}. (Only redefined for the Convex.)
2568 Means that System V (prior to SVR4) include files are in use. (FIXME:
2569 This symbol is abused in @file{infrun.c}, @file{regex.c}, and
2570 @file{utils.c} for other things, at the moment.)
2573 Define this to help placate @code{lint} in some situations.
2576 Define this to override the defaults of @code{__volatile__} or
2581 @node Target Architecture Definition
2583 @chapter Target Architecture Definition
2585 @cindex target architecture definition
2586 @value{GDBN}'s target architecture defines what sort of
2587 machine-language programs @value{GDBN} can work with, and how it works
2590 The target architecture object is implemented as the C structure
2591 @code{struct gdbarch *}. The structure, and its methods, are generated
2592 using the Bourne shell script @file{gdbarch.sh}.
2594 @section Operating System ABI Variant Handling
2595 @cindex OS ABI variants
2597 @value{GDBN} provides a mechanism for handling variations in OS
2598 ABIs. An OS ABI variant may have influence over any number of
2599 variables in the target architecture definition. There are two major
2600 components in the OS ABI mechanism: sniffers and handlers.
2602 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2603 (the architecture may be wildcarded) in an attempt to determine the
2604 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2605 to be @dfn{generic}, while sniffers for a specific architecture are
2606 considered to be @dfn{specific}. A match from a specific sniffer
2607 overrides a match from a generic sniffer. Multiple sniffers for an
2608 architecture/flavour may exist, in order to differentiate between two
2609 different operating systems which use the same basic file format. The
2610 OS ABI framework provides a generic sniffer for ELF-format files which
2611 examines the @code{EI_OSABI} field of the ELF header, as well as note
2612 sections known to be used by several operating systems.
2614 @cindex fine-tuning @code{gdbarch} structure
2615 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2616 selected OS ABI. There may be only one handler for a given OS ABI
2617 for each BFD architecture.
2619 The following OS ABI variants are defined in @file{defs.h}:
2623 @findex GDB_OSABI_UNINITIALIZED
2624 @item GDB_OSABI_UNINITIALIZED
2625 Used for struct gdbarch_info if ABI is still uninitialized.
2627 @findex GDB_OSABI_UNKNOWN
2628 @item GDB_OSABI_UNKNOWN
2629 The ABI of the inferior is unknown. The default @code{gdbarch}
2630 settings for the architecture will be used.
2632 @findex GDB_OSABI_SVR4
2633 @item GDB_OSABI_SVR4
2634 UNIX System V Release 4.
2636 @findex GDB_OSABI_HURD
2637 @item GDB_OSABI_HURD
2638 GNU using the Hurd kernel.
2640 @findex GDB_OSABI_SOLARIS
2641 @item GDB_OSABI_SOLARIS
2644 @findex GDB_OSABI_OSF1
2645 @item GDB_OSABI_OSF1
2646 OSF/1, including Digital UNIX and Compaq Tru64 UNIX.
2648 @findex GDB_OSABI_LINUX
2649 @item GDB_OSABI_LINUX
2650 GNU using the Linux kernel.
2652 @findex GDB_OSABI_FREEBSD_AOUT
2653 @item GDB_OSABI_FREEBSD_AOUT
2654 FreeBSD using the @code{a.out} executable format.
2656 @findex GDB_OSABI_FREEBSD_ELF
2657 @item GDB_OSABI_FREEBSD_ELF
2658 FreeBSD using the ELF executable format.
2660 @findex GDB_OSABI_NETBSD_AOUT
2661 @item GDB_OSABI_NETBSD_AOUT
2662 NetBSD using the @code{a.out} executable format.
2664 @findex GDB_OSABI_NETBSD_ELF
2665 @item GDB_OSABI_NETBSD_ELF
2666 NetBSD using the ELF executable format.
2668 @findex GDB_OSABI_OPENBSD_ELF
2669 @item GDB_OSABI_OPENBSD_ELF
2670 OpenBSD using the ELF executable format.
2672 @findex GDB_OSABI_WINCE
2673 @item GDB_OSABI_WINCE
2676 @findex GDB_OSABI_GO32
2677 @item GDB_OSABI_GO32
2680 @findex GDB_OSABI_NETWARE
2681 @item GDB_OSABI_NETWARE
2684 @findex GDB_OSABI_IRIX
2685 @item GDB_OSABI_IRIX
2688 @findex GDB_OSABI_LYNXOS
2689 @item GDB_OSABI_LYNXOS
2692 @findex GDB_OSABI_INTERIX
2693 @item GDB_OSABI_INTERIX
2694 Interix (Posix layer for MS-Windows systems).
2696 @findex GDB_OSABI_HPUX_ELF
2697 @item GDB_OSABI_HPUX_ELF
2698 HP/UX using the ELF executable format.
2700 @findex GDB_OSABI_HPUX_SOM
2701 @item GDB_OSABI_HPUX_SOM
2702 HP/UX using the SOM executable format.
2704 @findex GDB_OSABI_QNXNTO
2705 @item GDB_OSABI_QNXNTO
2708 @findex GDB_OSABI_CYGWIN
2709 @item GDB_OSABI_CYGWIN
2712 @findex GDB_OSABI_AIX
2718 Here are the functions that make up the OS ABI framework:
2720 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2721 Return the name of the OS ABI corresponding to @var{osabi}.
2724 @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}))
2725 Register the OS ABI handler specified by @var{init_osabi} for the
2726 architecture, machine type and OS ABI specified by @var{arch},
2727 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2728 machine type, which implies the architecture's default machine type,
2732 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2733 Register the OS ABI file sniffer specified by @var{sniffer} for the
2734 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2735 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2736 be generic, and is allowed to examine @var{flavour}-flavoured files for
2740 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2741 Examine the file described by @var{abfd} to determine its OS ABI.
2742 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2746 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2747 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2748 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2749 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2750 architecture, a warning will be issued and the debugging session will continue
2751 with the defaults already established for @var{gdbarch}.
2754 @deftypefun void generic_elf_osabi_sniff_abi_tag_sections (bfd *@var{abfd}, asection *@var{sect}, void *@var{obj})
2755 Helper routine for ELF file sniffers. Examine the file described by
2756 @var{abfd} and look at ABI tag note sections to determine the OS ABI
2757 from the note. This function should be called via
2758 @code{bfd_map_over_sections}.
2761 @section Initializing a New Architecture
2763 Each @code{gdbarch} is associated with a single @sc{bfd} architecture,
2764 via a @code{bfd_arch_@var{arch}} constant. The @code{gdbarch} is
2765 registered by a call to @code{register_gdbarch_init}, usually from
2766 the file's @code{_initialize_@var{filename}} routine, which will
2767 be automatically called during @value{GDBN} startup. The arguments
2768 are a @sc{bfd} architecture constant and an initialization function.
2770 The initialization function has this type:
2773 static struct gdbarch *
2774 @var{arch}_gdbarch_init (struct gdbarch_info @var{info},
2775 struct gdbarch_list *@var{arches})
2778 The @var{info} argument contains parameters used to select the correct
2779 architecture, and @var{arches} is a list of architectures which
2780 have already been created with the same @code{bfd_arch_@var{arch}}
2783 The initialization function should first make sure that @var{info}
2784 is acceptable, and return @code{NULL} if it is not. Then, it should
2785 search through @var{arches} for an exact match to @var{info}, and
2786 return one if found. Lastly, if no exact match was found, it should
2787 create a new architecture based on @var{info} and return it.
2789 Only information in @var{info} should be used to choose the new
2790 architecture. Historically, @var{info} could be sparse, and
2791 defaults would be collected from the first element on @var{arches}.
2792 However, @value{GDBN} now fills in @var{info} more thoroughly,
2793 so new @code{gdbarch} initialization functions should not take
2794 defaults from @var{arches}.
2796 @section Registers and Memory
2798 @value{GDBN}'s model of the target machine is rather simple.
2799 @value{GDBN} assumes the machine includes a bank of registers and a
2800 block of memory. Each register may have a different size.
2802 @value{GDBN} does not have a magical way to match up with the
2803 compiler's idea of which registers are which; however, it is critical
2804 that they do match up accurately. The only way to make this work is
2805 to get accurate information about the order that the compiler uses,
2806 and to reflect that in the @code{REGISTER_NAME} and related macros.
2808 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2810 @section Pointers Are Not Always Addresses
2811 @cindex pointer representation
2812 @cindex address representation
2813 @cindex word-addressed machines
2814 @cindex separate data and code address spaces
2815 @cindex spaces, separate data and code address
2816 @cindex address spaces, separate data and code
2817 @cindex code pointers, word-addressed
2818 @cindex converting between pointers and addresses
2819 @cindex D10V addresses
2821 On almost all 32-bit architectures, the representation of a pointer is
2822 indistinguishable from the representation of some fixed-length number
2823 whose value is the byte address of the object pointed to. On such
2824 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2825 However, architectures with smaller word sizes are often cramped for
2826 address space, so they may choose a pointer representation that breaks this
2827 identity, and allows a larger code address space.
2829 For example, the Renesas D10V is a 16-bit VLIW processor whose
2830 instructions are 32 bits long@footnote{Some D10V instructions are
2831 actually pairs of 16-bit sub-instructions. However, since you can't
2832 jump into the middle of such a pair, code addresses can only refer to
2833 full 32 bit instructions, which is what matters in this explanation.}.
2834 If the D10V used ordinary byte addresses to refer to code locations,
2835 then the processor would only be able to address 64kb of instructions.
2836 However, since instructions must be aligned on four-byte boundaries, the
2837 low two bits of any valid instruction's byte address are always
2838 zero---byte addresses waste two bits. So instead of byte addresses,
2839 the D10V uses word addresses---byte addresses shifted right two bits---to
2840 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2843 However, this means that code pointers and data pointers have different
2844 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2845 @code{0xC020} when used as a data address, but refers to byte address
2846 @code{0x30080} when used as a code address.
2848 (The D10V also uses separate code and data address spaces, which also
2849 affects the correspondence between pointers and addresses, but we're
2850 going to ignore that here; this example is already too long.)
2852 To cope with architectures like this---the D10V is not the only
2853 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2854 byte numbers, and @dfn{pointers}, which are the target's representation
2855 of an address of a particular type of data. In the example above,
2856 @code{0xC020} is the pointer, which refers to one of the addresses
2857 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2858 @value{GDBN} provides functions for turning a pointer into an address
2859 and vice versa, in the appropriate way for the current architecture.
2861 Unfortunately, since addresses and pointers are identical on almost all
2862 processors, this distinction tends to bit-rot pretty quickly. Thus,
2863 each time you port @value{GDBN} to an architecture which does
2864 distinguish between pointers and addresses, you'll probably need to
2865 clean up some architecture-independent code.
2867 Here are functions which convert between pointers and addresses:
2869 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2870 Treat the bytes at @var{buf} as a pointer or reference of type
2871 @var{type}, and return the address it represents, in a manner
2872 appropriate for the current architecture. This yields an address
2873 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2874 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2877 For example, if the current architecture is the Intel x86, this function
2878 extracts a little-endian integer of the appropriate length from
2879 @var{buf} and returns it. However, if the current architecture is the
2880 D10V, this function will return a 16-bit integer extracted from
2881 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2883 If @var{type} is not a pointer or reference type, then this function
2884 will signal an internal error.
2887 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2888 Store the address @var{addr} in @var{buf}, in the proper format for a
2889 pointer of type @var{type} in the current architecture. Note that
2890 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2893 For example, if the current architecture is the Intel x86, this function
2894 stores @var{addr} unmodified as a little-endian integer of the
2895 appropriate length in @var{buf}. However, if the current architecture
2896 is the D10V, this function divides @var{addr} by four if @var{type} is
2897 a pointer to a function, and then stores it in @var{buf}.
2899 If @var{type} is not a pointer or reference type, then this function
2900 will signal an internal error.
2903 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2904 Assuming that @var{val} is a pointer, return the address it represents,
2905 as appropriate for the current architecture.
2907 This function actually works on integral values, as well as pointers.
2908 For pointers, it performs architecture-specific conversions as
2909 described above for @code{extract_typed_address}.
2912 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2913 Create and return a value representing a pointer of type @var{type} to
2914 the address @var{addr}, as appropriate for the current architecture.
2915 This function performs architecture-specific conversions as described
2916 above for @code{store_typed_address}.
2919 Here are some macros which architectures can define to indicate the
2920 relationship between pointers and addresses. These have default
2921 definitions, appropriate for architectures on which all pointers are
2922 simple unsigned byte addresses.
2924 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2925 Assume that @var{buf} holds a pointer of type @var{type}, in the
2926 appropriate format for the current architecture. Return the byte
2927 address the pointer refers to.
2929 This function may safely assume that @var{type} is either a pointer or a
2930 C@t{++} reference type.
2933 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2934 Store in @var{buf} a pointer of type @var{type} representing the address
2935 @var{addr}, in the appropriate format for the current architecture.
2937 This function may safely assume that @var{type} is either a pointer or a
2938 C@t{++} reference type.
2941 @section Address Classes
2942 @cindex address classes
2943 @cindex DW_AT_byte_size
2944 @cindex DW_AT_address_class
2946 Sometimes information about different kinds of addresses is available
2947 via the debug information. For example, some programming environments
2948 define addresses of several different sizes. If the debug information
2949 distinguishes these kinds of address classes through either the size
2950 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2951 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2952 following macros should be defined in order to disambiguate these
2953 types within @value{GDBN} as well as provide the added information to
2954 a @value{GDBN} user when printing type expressions.
2956 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2957 Returns the type flags needed to construct a pointer type whose size
2958 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2959 This function is normally called from within a symbol reader. See
2960 @file{dwarf2read.c}.
2963 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2964 Given the type flags representing an address class qualifier, return
2967 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2968 Given an address qualifier name, set the @code{int} referenced by @var{type_flags_ptr} to the type flags
2969 for that address class qualifier.
2972 Since the need for address classes is rather rare, none of
2973 the address class macros defined by default. Predicate
2974 macros are provided to detect when they are defined.
2976 Consider a hypothetical architecture in which addresses are normally
2977 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2978 suppose that the @w{DWARF 2} information for this architecture simply
2979 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2980 of these "short" pointers. The following functions could be defined
2981 to implement the address class macros:
2984 somearch_address_class_type_flags (int byte_size,
2985 int dwarf2_addr_class)
2988 return TYPE_FLAG_ADDRESS_CLASS_1;
2994 somearch_address_class_type_flags_to_name (int type_flags)
2996 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
3003 somearch_address_class_name_to_type_flags (char *name,
3004 int *type_flags_ptr)
3006 if (strcmp (name, "short") == 0)
3008 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
3016 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
3017 to indicate the presence of one of these "short" pointers. E.g, if
3018 the debug information indicates that @code{short_ptr_var} is one of these
3019 short pointers, @value{GDBN} might show the following behavior:
3022 (gdb) ptype short_ptr_var
3023 type = int * @@short
3027 @section Raw and Virtual Register Representations
3028 @cindex raw register representation
3029 @cindex virtual register representation
3030 @cindex representations, raw and virtual registers
3032 @emph{Maintainer note: This section is pretty much obsolete. The
3033 functionality described here has largely been replaced by
3034 pseudo-registers and the mechanisms described in @ref{Target
3035 Architecture Definition, , Using Different Register and Memory Data
3036 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
3037 Bug Tracking Database} and
3038 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
3039 up-to-date information.}
3041 Some architectures use one representation for a value when it lives in a
3042 register, but use a different representation when it lives in memory.
3043 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
3044 the target registers, and the @dfn{virtual} representation is the one
3045 used in memory, and within @value{GDBN} @code{struct value} objects.
3047 @emph{Maintainer note: Notice that the same mechanism is being used to
3048 both convert a register to a @code{struct value} and alternative
3051 For almost all data types on almost all architectures, the virtual and
3052 raw representations are identical, and no special handling is needed.
3053 However, they do occasionally differ. For example:
3057 The x86 architecture supports an 80-bit @code{long double} type. However, when
3058 we store those values in memory, they occupy twelve bytes: the
3059 floating-point number occupies the first ten, and the final two bytes
3060 are unused. This keeps the values aligned on four-byte boundaries,
3061 allowing more efficient access. Thus, the x86 80-bit floating-point
3062 type is the raw representation, and the twelve-byte loosely-packed
3063 arrangement is the virtual representation.
3066 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
3067 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
3068 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
3069 raw representation, and the trimmed 32-bit representation is the
3070 virtual representation.
3073 In general, the raw representation is determined by the architecture, or
3074 @value{GDBN}'s interface to the architecture, while the virtual representation
3075 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
3076 @code{registers}, holds the register contents in raw format, and the
3077 @value{GDBN} remote protocol transmits register values in raw format.
3079 Your architecture may define the following macros to request
3080 conversions between the raw and virtual format:
3082 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
3083 Return non-zero if register number @var{reg}'s value needs different raw
3084 and virtual formats.
3086 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
3087 unless this macro returns a non-zero value for that register.
3090 @deftypefn {Target Macro} int DEPRECATED_REGISTER_RAW_SIZE (int @var{reg})
3091 The size of register number @var{reg}'s raw value. This is the number
3092 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
3093 remote protocol packet.
3096 @deftypefn {Target Macro} int DEPRECATED_REGISTER_VIRTUAL_SIZE (int @var{reg})
3097 The size of register number @var{reg}'s value, in its virtual format.
3098 This is the size a @code{struct value}'s buffer will have, holding that
3102 @deftypefn {Target Macro} struct type *DEPRECATED_REGISTER_VIRTUAL_TYPE (int @var{reg})
3103 This is the type of the virtual representation of register number
3104 @var{reg}. Note that there is no need for a macro giving a type for the
3105 register's raw form; once the register's value has been obtained, @value{GDBN}
3106 always uses the virtual form.
3109 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3110 Convert the value of register number @var{reg} to @var{type}, which
3111 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3112 at @var{from} holds the register's value in raw format; the macro should
3113 convert the value to virtual format, and place it at @var{to}.
3115 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
3116 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
3117 arguments in different orders.
3119 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
3120 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
3124 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3125 Convert the value of register number @var{reg} to @var{type}, which
3126 should always be @code{DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
3127 at @var{from} holds the register's value in raw format; the macro should
3128 convert the value to virtual format, and place it at @var{to}.
3130 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
3131 their @var{reg} and @var{type} arguments in different orders.
3135 @section Using Different Register and Memory Data Representations
3136 @cindex register representation
3137 @cindex memory representation
3138 @cindex representations, register and memory
3139 @cindex register data formats, converting
3140 @cindex @code{struct value}, converting register contents to
3142 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
3143 significant change. Many of the macros and functions referred to in this
3144 section are likely to be subject to further revision. See
3145 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
3146 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
3147 further information. cagney/2002-05-06.}
3149 Some architectures can represent a data object in a register using a
3150 form that is different to the objects more normal memory representation.
3156 The Alpha architecture can represent 32 bit integer values in
3157 floating-point registers.
3160 The x86 architecture supports 80-bit floating-point registers. The
3161 @code{long double} data type occupies 96 bits in memory but only 80 bits
3162 when stored in a register.
3166 In general, the register representation of a data type is determined by
3167 the architecture, or @value{GDBN}'s interface to the architecture, while
3168 the memory representation is determined by the Application Binary
3171 For almost all data types on almost all architectures, the two
3172 representations are identical, and no special handling is needed.
3173 However, they do occasionally differ. Your architecture may define the
3174 following macros to request conversions between the register and memory
3175 representations of a data type:
3177 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
3178 Return non-zero if the representation of a data value stored in this
3179 register may be different to the representation of that same data value
3180 when stored in memory.
3182 When non-zero, the macros @code{REGISTER_TO_VALUE} and
3183 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
3186 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
3187 Convert the value of register number @var{reg} to a data object of type
3188 @var{type}. The buffer at @var{from} holds the register's value in raw
3189 format; the converted value should be placed in the buffer at @var{to}.
3191 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3192 their @var{reg} and @var{type} arguments in different orders.
3194 You should only use @code{REGISTER_TO_VALUE} with registers for which
3195 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3198 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
3199 Convert a data value of type @var{type} to register number @var{reg}'
3202 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
3203 their @var{reg} and @var{type} arguments in different orders.
3205 You should only use @code{VALUE_TO_REGISTER} with registers for which
3206 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
3209 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
3210 See @file{mips-tdep.c}. It does not do what you want.
3214 @section Frame Interpretation
3216 @section Inferior Call Setup
3218 @section Compiler Characteristics
3220 @section Target Conditionals
3222 This section describes the macros that you can use to define the target
3227 @item ADDR_BITS_REMOVE (addr)
3228 @findex ADDR_BITS_REMOVE
3229 If a raw machine instruction address includes any bits that are not
3230 really part of the address, then define this macro to expand into an
3231 expression that zeroes those bits in @var{addr}. This is only used for
3232 addresses of instructions, and even then not in all contexts.
3234 For example, the two low-order bits of the PC on the Hewlett-Packard PA
3235 2.0 architecture contain the privilege level of the corresponding
3236 instruction. Since instructions must always be aligned on four-byte
3237 boundaries, the processor masks out these bits to generate the actual
3238 address of the instruction. ADDR_BITS_REMOVE should filter out these
3239 bits with an expression such as @code{((addr) & ~3)}.
3241 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
3242 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
3243 If @var{name} is a valid address class qualifier name, set the @code{int}
3244 referenced by @var{type_flags_ptr} to the mask representing the qualifier
3245 and return 1. If @var{name} is not a valid address class qualifier name,
3248 The value for @var{type_flags_ptr} should be one of
3249 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
3250 possibly some combination of these values or'd together.
3251 @xref{Target Architecture Definition, , Address Classes}.
3253 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
3254 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
3255 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
3258 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3259 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
3260 Given a pointers byte size (as described by the debug information) and
3261 the possible @code{DW_AT_address_class} value, return the type flags
3262 used by @value{GDBN} to represent this address class. The value
3263 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
3264 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
3265 values or'd together.
3266 @xref{Target Architecture Definition, , Address Classes}.
3268 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
3269 @findex ADDRESS_CLASS_TYPE_FLAGS_P
3270 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
3273 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
3274 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
3275 Return the name of the address class qualifier associated with the type
3276 flags given by @var{type_flags}.
3278 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
3279 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
3280 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
3282 @xref{Target Architecture Definition, , Address Classes}.
3284 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
3285 @findex ADDRESS_TO_POINTER
3286 Store in @var{buf} a pointer of type @var{type} representing the address
3287 @var{addr}, in the appropriate format for the current architecture.
3288 This macro may safely assume that @var{type} is either a pointer or a
3289 C@t{++} reference type.
3290 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3292 @item BELIEVE_PCC_PROMOTION
3293 @findex BELIEVE_PCC_PROMOTION
3294 Define if the compiler promotes a @code{short} or @code{char}
3295 parameter to an @code{int}, but still reports the parameter as its
3296 original type, rather than the promoted type.
3298 @item BITS_BIG_ENDIAN
3299 @findex BITS_BIG_ENDIAN
3300 Define this if the numbering of bits in the targets does @strong{not} match the
3301 endianness of the target byte order. A value of 1 means that the bits
3302 are numbered in a big-endian bit order, 0 means little-endian.
3306 This is the character array initializer for the bit pattern to put into
3307 memory where a breakpoint is set. Although it's common to use a trap
3308 instruction for a breakpoint, it's not required; for instance, the bit
3309 pattern could be an invalid instruction. The breakpoint must be no
3310 longer than the shortest instruction of the architecture.
3312 @code{BREAKPOINT} has been deprecated in favor of
3313 @code{BREAKPOINT_FROM_PC}.
3315 @item BIG_BREAKPOINT
3316 @itemx LITTLE_BREAKPOINT
3317 @findex LITTLE_BREAKPOINT
3318 @findex BIG_BREAKPOINT
3319 Similar to BREAKPOINT, but used for bi-endian targets.
3321 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3322 favor of @code{BREAKPOINT_FROM_PC}.
3324 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3325 @findex BREAKPOINT_FROM_PC
3326 @anchor{BREAKPOINT_FROM_PC} Use the program counter to determine the
3327 contents and size of a breakpoint instruction. It returns a pointer to
3328 a string of bytes that encode a breakpoint instruction, stores the
3329 length of the string to @code{*@var{lenptr}}, and adjusts the program
3330 counter (if necessary) to point to the actual memory location where the
3331 breakpoint should be inserted.
3333 Although it is common to use a trap instruction for a breakpoint, it's
3334 not required; for instance, the bit pattern could be an invalid
3335 instruction. The breakpoint must be no longer than the shortest
3336 instruction of the architecture.
3338 Replaces all the other @var{BREAKPOINT} macros.
3340 @item MEMORY_INSERT_BREAKPOINT (@var{bp_tgt})
3341 @itemx MEMORY_REMOVE_BREAKPOINT (@var{bp_tgt})
3342 @findex MEMORY_REMOVE_BREAKPOINT
3343 @findex MEMORY_INSERT_BREAKPOINT
3344 Insert or remove memory based breakpoints. Reasonable defaults
3345 (@code{default_memory_insert_breakpoint} and
3346 @code{default_memory_remove_breakpoint} respectively) have been
3347 provided so that it is not necessary to define these for most
3348 architectures. Architectures which may want to define
3349 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3350 likely have instructions that are oddly sized or are not stored in a
3351 conventional manner.
3353 It may also be desirable (from an efficiency standpoint) to define
3354 custom breakpoint insertion and removal routines if
3355 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3358 @item ADJUST_BREAKPOINT_ADDRESS (@var{address})
3359 @findex ADJUST_BREAKPOINT_ADDRESS
3360 @cindex breakpoint address adjusted
3361 Given an address at which a breakpoint is desired, return a breakpoint
3362 address adjusted to account for architectural constraints on
3363 breakpoint placement. This method is not needed by most targets.
3365 The FR-V target (see @file{frv-tdep.c}) requires this method.
3366 The FR-V is a VLIW architecture in which a number of RISC-like
3367 instructions are grouped (packed) together into an aggregate
3368 instruction or instruction bundle. When the processor executes
3369 one of these bundles, the component instructions are executed
3372 In the course of optimization, the compiler may group instructions
3373 from distinct source statements into the same bundle. The line number
3374 information associated with one of the latter statements will likely
3375 refer to some instruction other than the first one in the bundle. So,
3376 if the user attempts to place a breakpoint on one of these latter
3377 statements, @value{GDBN} must be careful to @emph{not} place the break
3378 instruction on any instruction other than the first one in the bundle.
3379 (Remember though that the instructions within a bundle execute
3380 in parallel, so the @emph{first} instruction is the instruction
3381 at the lowest address and has nothing to do with execution order.)
3383 The FR-V's @code{ADJUST_BREAKPOINT_ADDRESS} method will adjust a
3384 breakpoint's address by scanning backwards for the beginning of
3385 the bundle, returning the address of the bundle.
3387 Since the adjustment of a breakpoint may significantly alter a user's
3388 expectation, @value{GDBN} prints a warning when an adjusted breakpoint
3389 is initially set and each time that that breakpoint is hit.
3391 @item CALL_DUMMY_LOCATION
3392 @findex CALL_DUMMY_LOCATION
3393 See the file @file{inferior.h}.
3395 This method has been replaced by @code{push_dummy_code}
3396 (@pxref{push_dummy_code}).
3398 @item CANNOT_FETCH_REGISTER (@var{regno})
3399 @findex CANNOT_FETCH_REGISTER
3400 A C expression that should be nonzero if @var{regno} cannot be fetched
3401 from an inferior process. This is only relevant if
3402 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3404 @item CANNOT_STORE_REGISTER (@var{regno})
3405 @findex CANNOT_STORE_REGISTER
3406 A C expression that should be nonzero if @var{regno} should not be
3407 written to the target. This is often the case for program counters,
3408 status words, and other special registers. If this is not defined,
3409 @value{GDBN} will assume that all registers may be written.
3411 @item int CONVERT_REGISTER_P(@var{regnum})
3412 @findex CONVERT_REGISTER_P
3413 Return non-zero if register @var{regnum} can represent data values in a
3415 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3417 @item DECR_PC_AFTER_BREAK
3418 @findex DECR_PC_AFTER_BREAK
3419 Define this to be the amount by which to decrement the PC after the
3420 program encounters a breakpoint. This is often the number of bytes in
3421 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3423 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3424 @findex DISABLE_UNSETTABLE_BREAK
3425 If defined, this should evaluate to 1 if @var{addr} is in a shared
3426 library in which breakpoints cannot be set and so should be disabled.
3428 @item PRINT_FLOAT_INFO()
3429 @findex PRINT_FLOAT_INFO
3430 If defined, then the @samp{info float} command will print information about
3431 the processor's floating point unit.
3433 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3434 @findex print_registers_info
3435 If defined, pretty print the value of the register @var{regnum} for the
3436 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3437 either all registers (@var{all} is non zero) or a select subset of
3438 registers (@var{all} is zero).
3440 The default method prints one register per line, and if @var{all} is
3441 zero omits floating-point registers.
3443 @item PRINT_VECTOR_INFO()
3444 @findex PRINT_VECTOR_INFO
3445 If defined, then the @samp{info vector} command will call this function
3446 to print information about the processor's vector unit.
3448 By default, the @samp{info vector} command will print all vector
3449 registers (the register's type having the vector attribute).
3451 @item DWARF_REG_TO_REGNUM
3452 @findex DWARF_REG_TO_REGNUM
3453 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3454 no conversion will be performed.
3456 @item DWARF2_REG_TO_REGNUM
3457 @findex DWARF2_REG_TO_REGNUM
3458 Convert DWARF2 register number into @value{GDBN} regnum. If not
3459 defined, no conversion will be performed.
3461 @item ECOFF_REG_TO_REGNUM
3462 @findex ECOFF_REG_TO_REGNUM
3463 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3464 no conversion will be performed.
3466 @item END_OF_TEXT_DEFAULT
3467 @findex END_OF_TEXT_DEFAULT
3468 This is an expression that should designate the end of the text section.
3471 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3472 @findex EXTRACT_RETURN_VALUE
3473 Define this to extract a function's return value of type @var{type} from
3474 the raw register state @var{regbuf} and copy that, in virtual format,
3477 This method has been deprecated in favour of @code{gdbarch_return_value}
3478 (@pxref{gdbarch_return_value}).
3480 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3481 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS
3482 @anchor{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}
3483 When defined, extract from the array @var{regbuf} (containing the raw
3484 register state) the @code{CORE_ADDR} at which a function should return
3485 its structure value.
3487 @xref{gdbarch_return_value}.
3489 @item DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P()
3490 @findex DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS_P
3491 Predicate for @code{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}.
3493 @item DEPRECATED_FP_REGNUM
3494 @findex DEPRECATED_FP_REGNUM
3495 If the virtual frame pointer is kept in a register, then define this
3496 macro to be the number (greater than or equal to zero) of that register.
3498 This should only need to be defined if @code{DEPRECATED_TARGET_READ_FP}
3501 @item DEPRECATED_FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3502 @findex DEPRECATED_FRAMELESS_FUNCTION_INVOCATION
3503 Define this to an expression that returns 1 if the function invocation
3504 represented by @var{fi} does not have a stack frame associated with it.
3507 @item frame_align (@var{address})
3508 @anchor{frame_align}
3510 Define this to adjust @var{address} so that it meets the alignment
3511 requirements for the start of a new stack frame. A stack frame's
3512 alignment requirements are typically stronger than a target processors
3513 stack alignment requirements (@pxref{DEPRECATED_STACK_ALIGN}).
3515 This function is used to ensure that, when creating a dummy frame, both
3516 the initial stack pointer and (if needed) the address of the return
3517 value are correctly aligned.
3519 Unlike @code{DEPRECATED_STACK_ALIGN}, this function always adjusts the
3520 address in the direction of stack growth.
3522 By default, no frame based stack alignment is performed.
3524 @item int frame_red_zone_size
3526 The number of bytes, beyond the innermost-stack-address, reserved by the
3527 @sc{abi}. A function is permitted to use this scratch area (instead of
3528 allocating extra stack space).
3530 When performing an inferior function call, to ensure that it does not
3531 modify this area, @value{GDBN} adjusts the innermost-stack-address by
3532 @var{frame_red_zone_size} bytes before pushing parameters onto the
3535 By default, zero bytes are allocated. The value must be aligned
3536 (@pxref{frame_align}).
3538 The @sc{amd64} (nee x86-64) @sc{abi} documentation refers to the
3539 @emph{red zone} when describing this scratch area.
3542 @item DEPRECATED_FRAME_CHAIN(@var{frame})
3543 @findex DEPRECATED_FRAME_CHAIN
3544 Given @var{frame}, return a pointer to the calling frame.
3546 @item DEPRECATED_FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3547 @findex DEPRECATED_FRAME_CHAIN_VALID
3548 Define this to be an expression that returns zero if the given frame is an
3549 outermost frame, with no caller, and nonzero otherwise. Most normal
3550 situations can be handled without defining this macro, including @code{NULL}
3551 chain pointers, dummy frames, and frames whose PC values are inside the
3552 startup file (e.g.@: @file{crt0.o}), inside @code{main}, or inside
3555 @item DEPRECATED_FRAME_INIT_SAVED_REGS(@var{frame})
3556 @findex DEPRECATED_FRAME_INIT_SAVED_REGS
3557 See @file{frame.h}. Determines the address of all registers in the
3558 current stack frame storing each in @code{frame->saved_regs}. Space for
3559 @code{frame->saved_regs} shall be allocated by
3560 @code{DEPRECATED_FRAME_INIT_SAVED_REGS} using
3561 @code{frame_saved_regs_zalloc}.
3563 @code{FRAME_FIND_SAVED_REGS} is deprecated.
3565 @item FRAME_NUM_ARGS (@var{fi})
3566 @findex FRAME_NUM_ARGS
3567 For the frame described by @var{fi} return the number of arguments that
3568 are being passed. If the number of arguments is not known, return
3571 @item DEPRECATED_FRAME_SAVED_PC(@var{frame})
3572 @findex DEPRECATED_FRAME_SAVED_PC
3573 @anchor{DEPRECATED_FRAME_SAVED_PC} Given @var{frame}, return the pc
3574 saved there. This is the return address.
3576 This method is deprecated. @xref{unwind_pc}.
3578 @item CORE_ADDR unwind_pc (struct frame_info *@var{this_frame})
3580 @anchor{unwind_pc} Return the instruction address, in @var{this_frame}'s
3581 caller, at which execution will resume after @var{this_frame} returns.
3582 This is commonly referred to as the return address.
3584 The implementation, which must be frame agnostic (work with any frame),
3585 is typically no more than:
3589 frame_unwind_unsigned_register (this_frame, D10V_PC_REGNUM, &pc);
3590 return d10v_make_iaddr (pc);
3594 @xref{DEPRECATED_FRAME_SAVED_PC}, which this method replaces.
3596 @item CORE_ADDR unwind_sp (struct frame_info *@var{this_frame})
3598 @anchor{unwind_sp} Return the frame's inner most stack address. This is
3599 commonly referred to as the frame's @dfn{stack pointer}.
3601 The implementation, which must be frame agnostic (work with any frame),
3602 is typically no more than:
3606 frame_unwind_unsigned_register (this_frame, D10V_SP_REGNUM, &sp);
3607 return d10v_make_daddr (sp);
3611 @xref{TARGET_READ_SP}, which this method replaces.
3613 @item FUNCTION_EPILOGUE_SIZE
3614 @findex FUNCTION_EPILOGUE_SIZE
3615 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3616 function end symbol is 0. For such targets, you must define
3617 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3618 function's epilogue.
3620 @item DEPRECATED_FUNCTION_START_OFFSET
3621 @findex DEPRECATED_FUNCTION_START_OFFSET
3622 An integer, giving the offset in bytes from a function's address (as
3623 used in the values of symbols, function pointers, etc.), and the
3624 function's first genuine instruction.
3626 This is zero on almost all machines: the function's address is usually
3627 the address of its first instruction. However, on the VAX, for
3628 example, each function starts with two bytes containing a bitmask
3629 indicating which registers to save upon entry to the function. The
3630 VAX @code{call} instructions check this value, and save the
3631 appropriate registers automatically. Thus, since the offset from the
3632 function's address to its first instruction is two bytes,
3633 @code{DEPRECATED_FUNCTION_START_OFFSET} would be 2 on the VAX.
3635 @item GCC_COMPILED_FLAG_SYMBOL
3636 @itemx GCC2_COMPILED_FLAG_SYMBOL
3637 @findex GCC2_COMPILED_FLAG_SYMBOL
3638 @findex GCC_COMPILED_FLAG_SYMBOL
3639 If defined, these are the names of the symbols that @value{GDBN} will
3640 look for to detect that GCC compiled the file. The default symbols
3641 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3642 respectively. (Currently only defined for the Delta 68.)
3644 @item @value{GDBN}_MULTI_ARCH
3645 @findex @value{GDBN}_MULTI_ARCH
3646 If defined and non-zero, enables support for multiple architectures
3647 within @value{GDBN}.
3649 This support can be enabled at two levels. At level one, only
3650 definitions for previously undefined macros are provided; at level two,
3651 a multi-arch definition of all architecture dependent macros will be
3654 @item @value{GDBN}_TARGET_IS_HPPA
3655 @findex @value{GDBN}_TARGET_IS_HPPA
3656 This determines whether horrible kludge code in @file{dbxread.c} and
3657 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3658 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3661 @item GET_LONGJMP_TARGET
3662 @findex GET_LONGJMP_TARGET
3663 For most machines, this is a target-dependent parameter. On the
3664 DECstation and the Iris, this is a native-dependent parameter, since
3665 the header file @file{setjmp.h} is needed to define it.
3667 This macro determines the target PC address that @code{longjmp} will jump to,
3668 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3669 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3670 pointer. It examines the current state of the machine as needed.
3672 @item DEPRECATED_GET_SAVED_REGISTER
3673 @findex DEPRECATED_GET_SAVED_REGISTER
3674 Define this if you need to supply your own definition for the function
3675 @code{DEPRECATED_GET_SAVED_REGISTER}.
3677 @item DEPRECATED_IBM6000_TARGET
3678 @findex DEPRECATED_IBM6000_TARGET
3679 Shows that we are configured for an IBM RS/6000 system. This
3680 conditional should be eliminated (FIXME) and replaced by
3681 feature-specific macros. It was introduced in a haste and we are
3682 repenting at leisure.
3684 @item I386_USE_GENERIC_WATCHPOINTS
3685 An x86-based target can define this to use the generic x86 watchpoint
3686 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3688 @item SYMBOLS_CAN_START_WITH_DOLLAR
3689 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3690 Some systems have routines whose names start with @samp{$}. Giving this
3691 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3692 routines when parsing tokens that begin with @samp{$}.
3694 On HP-UX, certain system routines (millicode) have names beginning with
3695 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3696 routine that handles inter-space procedure calls on PA-RISC.
3698 @item DEPRECATED_INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3699 @findex DEPRECATED_INIT_EXTRA_FRAME_INFO
3700 If additional information about the frame is required this should be
3701 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3702 is allocated using @code{frame_extra_info_zalloc}.
3704 @item DEPRECATED_INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3705 @findex DEPRECATED_INIT_FRAME_PC
3706 This is a C statement that sets the pc of the frame pointed to by
3707 @var{prev}. [By default...]
3709 @item INNER_THAN (@var{lhs}, @var{rhs})
3711 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3712 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3713 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3716 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3717 @findex gdbarch_in_function_epilogue_p
3718 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3719 The epilogue of a function is defined as the part of a function where
3720 the stack frame of the function already has been destroyed up to the
3721 final `return from function call' instruction.
3723 @item DEPRECATED_SIGTRAMP_START (@var{pc})
3724 @findex DEPRECATED_SIGTRAMP_START
3725 @itemx DEPRECATED_SIGTRAMP_END (@var{pc})
3726 @findex DEPRECATED_SIGTRAMP_END
3727 Define these to be the start and end address of the @code{sigtramp} for the
3728 given @var{pc}. On machines where the address is just a compile time
3729 constant, the macro expansion will typically just ignore the supplied
3732 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3733 @findex IN_SOLIB_CALL_TRAMPOLINE
3734 Define this to evaluate to nonzero if the program is stopped in the
3735 trampoline that connects to a shared library.
3737 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3738 @findex IN_SOLIB_RETURN_TRAMPOLINE
3739 Define this to evaluate to nonzero if the program is stopped in the
3740 trampoline that returns from a shared library.
3742 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3743 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3744 Define this to evaluate to nonzero if the program is stopped in the
3747 @item SKIP_SOLIB_RESOLVER (@var{pc})
3748 @findex SKIP_SOLIB_RESOLVER
3749 Define this to evaluate to the (nonzero) address at which execution
3750 should continue to get past the dynamic linker's symbol resolution
3751 function. A zero value indicates that it is not important or necessary
3752 to set a breakpoint to get through the dynamic linker and that single
3753 stepping will suffice.
3755 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3756 @findex INTEGER_TO_ADDRESS
3757 @cindex converting integers to addresses
3758 Define this when the architecture needs to handle non-pointer to address
3759 conversions specially. Converts that value to an address according to
3760 the current architectures conventions.
3762 @emph{Pragmatics: When the user copies a well defined expression from
3763 their source code and passes it, as a parameter, to @value{GDBN}'s
3764 @code{print} command, they should get the same value as would have been
3765 computed by the target program. Any deviation from this rule can cause
3766 major confusion and annoyance, and needs to be justified carefully. In
3767 other words, @value{GDBN} doesn't really have the freedom to do these
3768 conversions in clever and useful ways. It has, however, been pointed
3769 out that users aren't complaining about how @value{GDBN} casts integers
3770 to pointers; they are complaining that they can't take an address from a
3771 disassembly listing and give it to @code{x/i}. Adding an architecture
3772 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3773 @value{GDBN} to ``get it right'' in all circumstances.}
3775 @xref{Target Architecture Definition, , Pointers Are Not Always
3778 @item NO_HIF_SUPPORT
3779 @findex NO_HIF_SUPPORT
3780 (Specific to the a29k.)
3782 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3783 @findex POINTER_TO_ADDRESS
3784 Assume that @var{buf} holds a pointer of type @var{type}, in the
3785 appropriate format for the current architecture. Return the byte
3786 address the pointer refers to.
3787 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3789 @item REGISTER_CONVERTIBLE (@var{reg})
3790 @findex REGISTER_CONVERTIBLE
3791 Return non-zero if @var{reg} uses different raw and virtual formats.
3792 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3794 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3795 @findex REGISTER_TO_VALUE
3796 Convert the raw contents of register @var{regnum} into a value of type
3798 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3800 @item DEPRECATED_REGISTER_RAW_SIZE (@var{reg})
3801 @findex DEPRECATED_REGISTER_RAW_SIZE
3802 Return the raw size of @var{reg}; defaults to the size of the register's
3804 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3806 @item register_reggroup_p (@var{gdbarch}, @var{regnum}, @var{reggroup})
3807 @findex register_reggroup_p
3808 @cindex register groups
3809 Return non-zero if register @var{regnum} is a member of the register
3810 group @var{reggroup}.
3812 By default, registers are grouped as follows:
3815 @item float_reggroup
3816 Any register with a valid name and a floating-point type.
3817 @item vector_reggroup
3818 Any register with a valid name and a vector type.
3819 @item general_reggroup
3820 Any register with a valid name and a type other than vector or
3821 floating-point. @samp{float_reggroup}.
3823 @itemx restore_reggroup
3825 Any register with a valid name.
3828 @item DEPRECATED_REGISTER_VIRTUAL_SIZE (@var{reg})
3829 @findex DEPRECATED_REGISTER_VIRTUAL_SIZE
3830 Return the virtual size of @var{reg}; defaults to the size of the
3831 register's virtual type.
3832 Return the virtual size of @var{reg}.
3833 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3835 @item DEPRECATED_REGISTER_VIRTUAL_TYPE (@var{reg})
3836 @findex REGISTER_VIRTUAL_TYPE
3837 Return the virtual type of @var{reg}.
3838 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3840 @item struct type *register_type (@var{gdbarch}, @var{reg})
3841 @findex register_type
3842 If defined, return the type of register @var{reg}. This function
3843 supersedes @code{DEPRECATED_REGISTER_VIRTUAL_TYPE}. @xref{Target Architecture
3844 Definition, , Raw and Virtual Register Representations}.
3846 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3847 @findex REGISTER_CONVERT_TO_VIRTUAL
3848 Convert the value of register @var{reg} from its raw form to its virtual
3850 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3852 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3853 @findex REGISTER_CONVERT_TO_RAW
3854 Convert the value of register @var{reg} from its virtual form to its raw
3856 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3858 @item const struct regset *regset_from_core_section (struct gdbarch * @var{gdbarch}, const char * @var{sect_name}, size_t @var{sect_size})
3859 @findex regset_from_core_section
3860 Return the appropriate register set for a core file section with name
3861 @var{sect_name} and size @var{sect_size}.
3863 @item SOFTWARE_SINGLE_STEP_P()
3864 @findex SOFTWARE_SINGLE_STEP_P
3865 Define this as 1 if the target does not have a hardware single-step
3866 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3868 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breakpoints_p})
3869 @findex SOFTWARE_SINGLE_STEP
3870 A function that inserts or removes (depending on
3871 @var{insert_breakpoints_p}) breakpoints at each possible destinations of
3872 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3875 @item SOFUN_ADDRESS_MAYBE_MISSING
3876 @findex SOFUN_ADDRESS_MAYBE_MISSING
3877 Somebody clever observed that, the more actual addresses you have in the
3878 debug information, the more time the linker has to spend relocating
3879 them. So whenever there's some other way the debugger could find the
3880 address it needs, you should omit it from the debug info, to make
3883 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3884 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3885 entries in stabs-format debugging information. @code{N_SO} stabs mark
3886 the beginning and ending addresses of compilation units in the text
3887 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3889 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3893 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3894 addresses where the function starts by taking the function name from
3895 the stab, and then looking that up in the minsyms (the
3896 linker/assembler symbol table). In other words, the stab has the
3897 name, and the linker/assembler symbol table is the only place that carries
3901 @code{N_SO} stabs have an address of zero, too. You just look at the
3902 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3903 and guess the starting and ending addresses of the compilation unit from
3907 @item PC_LOAD_SEGMENT
3908 @findex PC_LOAD_SEGMENT
3909 If defined, print information about the load segment for the program
3910 counter. (Defined only for the RS/6000.)
3914 If the program counter is kept in a register, then define this macro to
3915 be the number (greater than or equal to zero) of that register.
3917 This should only need to be defined if @code{TARGET_READ_PC} and
3918 @code{TARGET_WRITE_PC} are not defined.
3921 @findex PARM_BOUNDARY
3922 If non-zero, round arguments to a boundary of this many bits before
3923 pushing them on the stack.
3925 @item stabs_argument_has_addr (@var{gdbarch}, @var{type})
3926 @findex stabs_argument_has_addr
3927 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3928 @anchor{stabs_argument_has_addr} Define this to return nonzero if a
3929 function argument of type @var{type} is passed by reference instead of
3932 This method replaces @code{DEPRECATED_REG_STRUCT_HAS_ADDR}
3933 (@pxref{DEPRECATED_REG_STRUCT_HAS_ADDR}).
3935 @item PROCESS_LINENUMBER_HOOK
3936 @findex PROCESS_LINENUMBER_HOOK
3937 A hook defined for XCOFF reading.
3939 @item PROLOGUE_FIRSTLINE_OVERLAP
3940 @findex PROLOGUE_FIRSTLINE_OVERLAP
3941 (Only used in unsupported Convex configuration.)
3945 If defined, this is the number of the processor status register. (This
3946 definition is only used in generic code when parsing "$ps".)
3948 @item DEPRECATED_POP_FRAME
3949 @findex DEPRECATED_POP_FRAME
3951 If defined, used by @code{frame_pop} to remove a stack frame. This
3952 method has been superseded by generic code.
3954 @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})
3955 @findex push_dummy_call
3956 @findex DEPRECATED_PUSH_ARGUMENTS.
3957 @anchor{push_dummy_call} Define this to push the dummy frame's call to
3958 the inferior function onto the stack. In addition to pushing
3959 @var{nargs}, the code should push @var{struct_addr} (when
3960 @var{struct_return}), and the return address (@var{bp_addr}).
3962 @var{function} is a pointer to a @code{struct value}; on architectures that use
3963 function descriptors, this contains the function descriptor value.
3965 Returns the updated top-of-stack pointer.
3967 This method replaces @code{DEPRECATED_PUSH_ARGUMENTS}.
3969 @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})
3970 @findex push_dummy_code
3971 @anchor{push_dummy_code} Given a stack based call dummy, push the
3972 instruction sequence (including space for a breakpoint) to which the
3973 called function should return.
3975 Set @var{bp_addr} to the address at which the breakpoint instruction
3976 should be inserted, @var{real_pc} to the resume address when starting
3977 the call sequence, and return the updated inner-most stack address.
3979 By default, the stack is grown sufficient to hold a frame-aligned
3980 (@pxref{frame_align}) breakpoint, @var{bp_addr} is set to the address
3981 reserved for that breakpoint, and @var{real_pc} set to @var{funaddr}.
3983 This method replaces @code{CALL_DUMMY_LOCATION},
3984 @code{DEPRECATED_REGISTER_SIZE}.
3986 @item REGISTER_NAME(@var{i})
3987 @findex REGISTER_NAME
3988 Return the name of register @var{i} as a string. May return @code{NULL}
3989 or @code{NUL} to indicate that register @var{i} is not valid.
3991 @item DEPRECATED_REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3992 @findex DEPRECATED_REG_STRUCT_HAS_ADDR
3993 @anchor{DEPRECATED_REG_STRUCT_HAS_ADDR}Define this to return 1 if the
3994 given type will be passed by pointer rather than directly.
3996 This method has been replaced by @code{stabs_argument_has_addr}
3997 (@pxref{stabs_argument_has_addr}).
3999 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
4000 @findex SAVE_DUMMY_FRAME_TOS
4001 @anchor{SAVE_DUMMY_FRAME_TOS} Used in @samp{call_function_by_hand} to
4002 notify the target dependent code of the top-of-stack value that will be
4003 passed to the inferior code. This is the value of the @code{SP}
4004 after both the dummy frame and space for parameters/results have been
4005 allocated on the stack. @xref{unwind_dummy_id}.
4007 @item SDB_REG_TO_REGNUM
4008 @findex SDB_REG_TO_REGNUM
4009 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
4010 defined, no conversion will be done.
4012 @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})
4013 @findex gdbarch_return_value
4014 @anchor{gdbarch_return_value} Given a function with a return-value of
4015 type @var{rettype}, return which return-value convention that function
4018 @value{GDBN} currently recognizes two function return-value conventions:
4019 @code{RETURN_VALUE_REGISTER_CONVENTION} where the return value is found
4020 in registers; and @code{RETURN_VALUE_STRUCT_CONVENTION} where the return
4021 value is found in memory and the address of that memory location is
4022 passed in as the function's first parameter.
4024 If the register convention is being used, and @var{writebuf} is
4025 non-@code{NULL}, also copy the return-value in @var{writebuf} into
4028 If the register convention is being used, and @var{readbuf} is
4029 non-@code{NULL}, also copy the return value from @var{regcache} into
4030 @var{readbuf} (@var{regcache} contains a copy of the registers from the
4031 just returned function).
4033 @xref{DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS}, for a description of how
4034 return-values that use the struct convention are handled.
4036 @emph{Maintainer note: This method replaces separate predicate, extract,
4037 store methods. By having only one method, the logic needed to determine
4038 the return-value convention need only be implemented in one place. If
4039 @value{GDBN} were written in an @sc{oo} language, this method would
4040 instead return an object that knew how to perform the register
4041 return-value extract and store.}
4043 @emph{Maintainer note: This method does not take a @var{gcc_p}
4044 parameter, and such a parameter should not be added. If an architecture
4045 that requires per-compiler or per-function information be identified,
4046 then the replacement of @var{rettype} with @code{struct value}
4047 @var{function} should be pursued.}
4049 @emph{Maintainer note: The @var{regcache} parameter limits this methods
4050 to the inner most frame. While replacing @var{regcache} with a
4051 @code{struct frame_info} @var{frame} parameter would remove that
4052 limitation there has yet to be a demonstrated need for such a change.}
4054 @item SKIP_PERMANENT_BREAKPOINT
4055 @findex SKIP_PERMANENT_BREAKPOINT
4056 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
4057 steps over a breakpoint by removing it, stepping one instruction, and
4058 re-inserting the breakpoint. However, permanent breakpoints are
4059 hardwired into the inferior, and can't be removed, so this strategy
4060 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
4061 state so that execution will resume just after the breakpoint. This
4062 macro does the right thing even when the breakpoint is in the delay slot
4063 of a branch or jump.
4065 @item SKIP_PROLOGUE (@var{pc})
4066 @findex SKIP_PROLOGUE
4067 A C expression that returns the address of the ``real'' code beyond the
4068 function entry prologue found at @var{pc}.
4070 @item SKIP_TRAMPOLINE_CODE (@var{pc})
4071 @findex SKIP_TRAMPOLINE_CODE
4072 If the target machine has trampoline code that sits between callers and
4073 the functions being called, then define this macro to return a new PC
4074 that is at the start of the real function.
4078 If the stack-pointer is kept in a register, then define this macro to be
4079 the number (greater than or equal to zero) of that register, or -1 if
4080 there is no such register.
4082 @item STAB_REG_TO_REGNUM
4083 @findex STAB_REG_TO_REGNUM
4084 Define this to convert stab register numbers (as gotten from `r'
4085 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
4088 @item DEPRECATED_STACK_ALIGN (@var{addr})
4089 @anchor{DEPRECATED_STACK_ALIGN}
4090 @findex DEPRECATED_STACK_ALIGN
4091 Define this to increase @var{addr} so that it meets the alignment
4092 requirements for the processor's stack.
4094 Unlike @ref{frame_align}, this function always adjusts @var{addr}
4097 By default, no stack alignment is performed.
4099 @item STEP_SKIPS_DELAY (@var{addr})
4100 @findex STEP_SKIPS_DELAY
4101 Define this to return true if the address is of an instruction with a
4102 delay slot. If a breakpoint has been placed in the instruction's delay
4103 slot, @value{GDBN} will single-step over that instruction before resuming
4104 normally. Currently only defined for the Mips.
4106 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
4107 @findex STORE_RETURN_VALUE
4108 A C expression that writes the function return value, found in
4109 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
4110 value that is to be returned.
4112 This method has been deprecated in favour of @code{gdbarch_return_value}
4113 (@pxref{gdbarch_return_value}).
4115 @item SYMBOL_RELOADING_DEFAULT
4116 @findex SYMBOL_RELOADING_DEFAULT
4117 The default value of the ``symbol-reloading'' variable. (Never defined in
4120 @item TARGET_CHAR_BIT
4121 @findex TARGET_CHAR_BIT
4122 Number of bits in a char; defaults to 8.
4124 @item TARGET_CHAR_SIGNED
4125 @findex TARGET_CHAR_SIGNED
4126 Non-zero if @code{char} is normally signed on this architecture; zero if
4127 it should be unsigned.
4129 The ISO C standard requires the compiler to treat @code{char} as
4130 equivalent to either @code{signed char} or @code{unsigned char}; any
4131 character in the standard execution set is supposed to be positive.
4132 Most compilers treat @code{char} as signed, but @code{char} is unsigned
4133 on the IBM S/390, RS6000, and PowerPC targets.
4135 @item TARGET_COMPLEX_BIT
4136 @findex TARGET_COMPLEX_BIT
4137 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
4139 At present this macro is not used.
4141 @item TARGET_DOUBLE_BIT
4142 @findex TARGET_DOUBLE_BIT
4143 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
4145 @item TARGET_DOUBLE_COMPLEX_BIT
4146 @findex TARGET_DOUBLE_COMPLEX_BIT
4147 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
4149 At present this macro is not used.
4151 @item TARGET_FLOAT_BIT
4152 @findex TARGET_FLOAT_BIT
4153 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
4155 @item TARGET_INT_BIT
4156 @findex TARGET_INT_BIT
4157 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4159 @item TARGET_LONG_BIT
4160 @findex TARGET_LONG_BIT
4161 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
4163 @item TARGET_LONG_DOUBLE_BIT
4164 @findex TARGET_LONG_DOUBLE_BIT
4165 Number of bits in a long double float;
4166 defaults to @code{2 * TARGET_DOUBLE_BIT}.
4168 @item TARGET_LONG_LONG_BIT
4169 @findex TARGET_LONG_LONG_BIT
4170 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
4172 @item TARGET_PTR_BIT
4173 @findex TARGET_PTR_BIT
4174 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
4176 @item TARGET_SHORT_BIT
4177 @findex TARGET_SHORT_BIT
4178 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
4180 @item TARGET_READ_PC
4181 @findex TARGET_READ_PC
4182 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
4183 @findex TARGET_WRITE_PC
4184 @anchor{TARGET_WRITE_PC}
4185 @itemx TARGET_READ_SP
4186 @findex TARGET_READ_SP
4187 @itemx TARGET_READ_FP
4188 @findex TARGET_READ_FP
4193 @anchor{TARGET_READ_SP} These change the behavior of @code{read_pc},
4194 @code{write_pc}, and @code{read_sp}. For most targets, these may be
4195 left undefined. @value{GDBN} will call the read and write register
4196 functions with the relevant @code{_REGNUM} argument.
4198 These macros are useful when a target keeps one of these registers in a
4199 hard to get at place; for example, part in a segment register and part
4200 in an ordinary register.
4202 @xref{unwind_sp}, which replaces @code{TARGET_READ_SP}.
4204 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
4205 @findex TARGET_VIRTUAL_FRAME_POINTER
4206 Returns a @code{(register, offset)} pair representing the virtual frame
4207 pointer in use at the code address @var{pc}. If virtual frame pointers
4208 are not used, a default definition simply returns
4209 @code{DEPRECATED_FP_REGNUM}, with an offset of zero.
4211 @item TARGET_HAS_HARDWARE_WATCHPOINTS
4212 If non-zero, the target has support for hardware-assisted
4213 watchpoints. @xref{Algorithms, watchpoints}, for more details and
4214 other related macros.
4216 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
4217 @findex TARGET_PRINT_INSN
4218 This is the function used by @value{GDBN} to print an assembly
4219 instruction. It prints the instruction at address @var{addr} in
4220 debugged memory and returns the length of the instruction, in bytes. If
4221 a target doesn't define its own printing routine, it defaults to an
4222 accessor function for the global pointer
4223 @code{deprecated_tm_print_insn}. This usually points to a function in
4224 the @code{opcodes} library (@pxref{Support Libraries, ,Opcodes}).
4225 @var{info} is a structure (of type @code{disassemble_info}) defined in
4226 @file{include/dis-asm.h} used to pass information to the instruction
4229 @item struct frame_id unwind_dummy_id (struct frame_info *@var{frame})
4230 @findex unwind_dummy_id
4231 @anchor{unwind_dummy_id} Given @var{frame} return a @code{struct
4232 frame_id} that uniquely identifies an inferior function call's dummy
4233 frame. The value returned must match the dummy frame stack value
4234 previously saved using @code{SAVE_DUMMY_FRAME_TOS}.
4235 @xref{SAVE_DUMMY_FRAME_TOS}.
4237 @item DEPRECATED_USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
4238 @findex DEPRECATED_USE_STRUCT_CONVENTION
4239 If defined, this must be an expression that is nonzero if a value of the
4240 given @var{type} being returned from a function must have space
4241 allocated for it on the stack. @var{gcc_p} is true if the function
4242 being considered is known to have been compiled by GCC; this is helpful
4243 for systems where GCC is known to use different calling convention than
4246 This method has been deprecated in favour of @code{gdbarch_return_value}
4247 (@pxref{gdbarch_return_value}).
4249 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
4250 @findex VALUE_TO_REGISTER
4251 Convert a value of type @var{type} into the raw contents of register
4253 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
4255 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4256 @findex VARIABLES_INSIDE_BLOCK
4257 For dbx-style debugging information, if the compiler puts variable
4258 declarations inside LBRAC/RBRAC blocks, this should be defined to be
4259 nonzero. @var{desc} is the value of @code{n_desc} from the
4260 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
4261 presence of either the @code{GCC_COMPILED_SYMBOL} or the
4262 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
4264 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4265 @findex OS9K_VARIABLES_INSIDE_BLOCK
4266 Similarly, for OS/9000. Defaults to 1.
4269 Motorola M68K target conditionals.
4273 Define this to be the 4-bit location of the breakpoint trap vector. If
4274 not defined, it will default to @code{0xf}.
4276 @item REMOTE_BPT_VECTOR
4277 Defaults to @code{1}.
4279 @item NAME_OF_MALLOC
4280 @findex NAME_OF_MALLOC
4281 A string containing the name of the function to call in order to
4282 allocate some memory in the inferior. The default value is "malloc".
4286 @section Adding a New Target
4288 @cindex adding a target
4289 The following files add a target to @value{GDBN}:
4293 @item gdb/config/@var{arch}/@var{ttt}.mt
4294 Contains a Makefile fragment specific to this target. Specifies what
4295 object files are needed for target @var{ttt}, by defining
4296 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
4297 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
4300 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
4301 but these are now deprecated, replaced by autoconf, and may go away in
4302 future versions of @value{GDBN}.
4304 @item gdb/@var{ttt}-tdep.c
4305 Contains any miscellaneous code required for this target machine. On
4306 some machines it doesn't exist at all. Sometimes the macros in
4307 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
4308 as functions here instead, and the macro is simply defined to call the
4309 function. This is vastly preferable, since it is easier to understand
4312 @item gdb/@var{arch}-tdep.c
4313 @itemx gdb/@var{arch}-tdep.h
4314 This often exists to describe the basic layout of the target machine's
4315 processor chip (registers, stack, etc.). If used, it is included by
4316 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
4319 @item gdb/config/@var{arch}/tm-@var{ttt}.h
4320 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
4321 macro definitions about the target machine's registers, stack frame
4322 format and instructions.
4324 New targets do not need this file and should not create it.
4326 @item gdb/config/@var{arch}/tm-@var{arch}.h
4327 This often exists to describe the basic layout of the target machine's
4328 processor chip (registers, stack, etc.). If used, it is included by
4329 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
4332 New targets do not need this file and should not create it.
4336 If you are adding a new operating system for an existing CPU chip, add a
4337 @file{config/tm-@var{os}.h} file that describes the operating system
4338 facilities that are unusual (extra symbol table info; the breakpoint
4339 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
4340 that just @code{#include}s @file{tm-@var{arch}.h} and
4341 @file{config/tm-@var{os}.h}.
4344 @section Converting an existing Target Architecture to Multi-arch
4345 @cindex converting targets to multi-arch
4347 This section describes the current accepted best practice for converting
4348 an existing target architecture to the multi-arch framework.
4350 The process consists of generating, testing, posting and committing a
4351 sequence of patches. Each patch must contain a single change, for
4357 Directly convert a group of functions into macros (the conversion does
4358 not change the behavior of any of the functions).
4361 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4365 Enable multi-arch level one.
4368 Delete one or more files.
4373 There isn't a size limit on a patch, however, a developer is strongly
4374 encouraged to keep the patch size down.
4376 Since each patch is well defined, and since each change has been tested
4377 and shows no regressions, the patches are considered @emph{fairly}
4378 obvious. Such patches, when submitted by developers listed in the
4379 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4380 process may be more complicated and less clear. The developer is
4381 expected to use their judgment and is encouraged to seek advice as
4384 @subsection Preparation
4386 The first step is to establish control. Build (with @option{-Werror}
4387 enabled) and test the target so that there is a baseline against which
4388 the debugger can be compared.
4390 At no stage can the test results regress or @value{GDBN} stop compiling
4391 with @option{-Werror}.
4393 @subsection Add the multi-arch initialization code
4395 The objective of this step is to establish the basic multi-arch
4396 framework. It involves
4401 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4402 above is from the original example and uses K&R C. @value{GDBN}
4403 has since converted to ISO C but lets ignore that.} that creates
4406 static struct gdbarch *
4407 d10v_gdbarch_init (info, arches)
4408 struct gdbarch_info info;
4409 struct gdbarch_list *arches;
4411 struct gdbarch *gdbarch;
4412 /* there is only one d10v architecture */
4414 return arches->gdbarch;
4415 gdbarch = gdbarch_alloc (&info, NULL);
4423 A per-architecture dump function to print any architecture specific
4427 mips_dump_tdep (struct gdbarch *current_gdbarch,
4428 struct ui_file *file)
4430 @dots{} code to print architecture specific info @dots{}
4435 A change to @code{_initialize_@var{arch}_tdep} to register this new
4439 _initialize_mips_tdep (void)
4441 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4446 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4447 @file{config/@var{arch}/tm-@var{arch}.h}.
4451 @subsection Update multi-arch incompatible mechanisms
4453 Some mechanisms do not work with multi-arch. They include:
4456 @item FRAME_FIND_SAVED_REGS
4457 Replaced with @code{DEPRECATED_FRAME_INIT_SAVED_REGS}
4461 At this stage you could also consider converting the macros into
4464 @subsection Prepare for multi-arch level to one
4466 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4467 and then build and start @value{GDBN} (the change should not be
4468 committed). @value{GDBN} may not build, and once built, it may die with
4469 an internal error listing the architecture methods that must be
4472 Fix any build problems (patch(es)).
4474 Convert all the architecture methods listed, which are only macros, into
4475 functions (patch(es)).
4477 Update @code{@var{arch}_gdbarch_init} to set all the missing
4478 architecture methods and wrap the corresponding macros in @code{#if
4479 !GDB_MULTI_ARCH} (patch(es)).
4481 @subsection Set multi-arch level one
4483 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4486 Any problems with throwing ``the switch'' should have been fixed
4489 @subsection Convert remaining macros
4491 Suggest converting macros into functions (and setting the corresponding
4492 architecture method) in small batches.
4494 @subsection Set multi-arch level to two
4496 This should go smoothly.
4498 @subsection Delete the TM file
4500 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4501 @file{configure.in} updated.
4504 @node Target Descriptions
4505 @chapter Target Descriptions
4506 @cindex target descriptions
4508 The target architecture definition (@pxref{Target Architecture Definition})
4509 contains @value{GDBN}'s hard-coded knowledge about an architecture. For
4510 some platforms, it is handy to have more flexible knowledge about a specific
4511 instance of the architecture---for instance, a processor or development board.
4512 @dfn{Target descriptions} provide a mechanism for the user to tell @value{GDBN}
4513 more about what their target supports, or for the target to tell @value{GDBN}
4516 For details on writing, automatically supplying, and manually selecting
4517 target descriptions, see @ref{Target Descriptions, , , gdb,
4518 Debugging with @value{GDBN}}. This section will cover some related
4519 topics about the @value{GDBN} internals.
4522 * Target Descriptions Implementation::
4523 * Adding Target Described Register Support::
4526 @node Target Descriptions Implementation
4527 @section Target Descriptions Implementation
4528 @cindex target descriptions, implementation
4530 Before @value{GDBN} connects to a new target, or runs a new program on
4531 an existing target, it discards any existing target description and
4532 reverts to a default gdbarch. Then, after connecting, it looks for a
4533 new target description by calling @code{target_find_description}.
4535 A description may come from a user specified file (XML), the remote
4536 @samp{qXfer:features:read} packet (also XML), or from any custom
4537 @code{to_read_description} routine in the target vector. For instance,
4538 the remote target supports guessing whether a MIPS target is 32-bit or
4539 64-bit based on the size of the @samp{g} packet.
4541 If any target description is found, @value{GDBN} creates a new gdbarch
4542 incorporating the description by calling @code{gdbarch_update_p}. Any
4543 @samp{<architecture>} element is handled first, to determine which
4544 architecture's gdbarch initialization routine is called to create the
4545 new architecture. Then the initialization routine is called, and has
4546 a chance to adjust the constructed architecture based on the contents
4547 of the target description. For instance, it can recognize any
4548 properties set by a @code{to_read_description} routine. Also
4549 see @ref{Adding Target Described Register Support}.
4551 @node Adding Target Described Register Support
4552 @section Adding Target Described Register Support
4553 @cindex target descriptions, adding register support
4555 Target descriptions can report additional registers specific to an
4556 instance of the target. But it takes a little work in the architecture
4557 specific routines to support this.
4559 A target description must either have no registers or a complete
4560 set---this avoids complexity in trying to merge standard registers
4561 with the target defined registers. It is the architecture's
4562 responsibility to validate that a description with registers has
4563 everything it needs. To keep architecture code simple, the same
4564 mechanism is used to assign fixed internal register numbers to
4567 If @code{tdesc_has_registers} returns 1, the description contains
4568 registers. The architecture's @code{gdbarch_init} routine should:
4573 Call @code{tdesc_data_alloc} to allocate storage, early, before
4574 searching for a matching gdbarch or allocating a new one.
4577 Use @code{tdesc_find_feature} to locate standard features by name.
4580 Use @code{tdesc_numbered_register} and @code{tdesc_numbered_register_choices}
4581 to locate the expected registers in the standard features.
4584 Return @code{NULL} if a required feature is missing, or if any standard
4585 feature is missing expected registers. This will produce a warning that
4586 the description was incomplete.
4589 Free the allocated data before returning, unless @code{tdesc_use_registers}
4593 Call @code{set_gdbarch_num_regs} as usual, with a number higher than any
4594 fixed number passed to @code{tdesc_numbered_register}.
4597 Call @code{tdesc_use_registers} after creating a new gdbarch, before
4602 After @code{tdesc_use_registers} has been called, the architecture's
4603 @code{register_name}, @code{register_type}, and @code{register_reggroup_p}
4604 routines will not be called; that information will be taken from
4605 the target description. @code{num_regs} may be increased to account
4606 for any additional registers in the description.
4608 Pseudo-registers require some extra care:
4613 Using @code{tdesc_numbered_register} allows the architecture to give
4614 constant register numbers to standard architectural registers, e.g.@:
4615 as an @code{enum} in @file{@var{arch}-tdep.h}. But because
4616 pseudo-registers are always numbered above @code{num_regs},
4617 which may be increased by the description, constant numbers
4618 can not be used for pseudos. They must be numbered relative to
4619 @code{num_regs} instead.
4622 The description will not describe pseudo-registers, so the
4623 architecture must call @code{set_tdesc_pseudo_register_name},
4624 @code{set_tdesc_pseudo_register_type}, and
4625 @code{set_tdesc_pseudo_register_reggroup_p} to supply routines
4626 describing pseudo registers. These routines will be passed
4627 internal register numbers, so the same routines used for the
4628 gdbarch equivalents are usually suitable.
4633 @node Target Vector Definition
4635 @chapter Target Vector Definition
4636 @cindex target vector
4638 The target vector defines the interface between @value{GDBN}'s
4639 abstract handling of target systems, and the nitty-gritty code that
4640 actually exercises control over a process or a serial port.
4641 @value{GDBN} includes some 30-40 different target vectors; however,
4642 each configuration of @value{GDBN} includes only a few of them.
4645 * Managing Execution State::
4646 * Existing Targets::
4649 @node Managing Execution State
4650 @section Managing Execution State
4651 @cindex execution state
4653 A target vector can be completely inactive (not pushed on the target
4654 stack), active but not running (pushed, but not connected to a fully
4655 manifested inferior), or completely active (pushed, with an accessible
4656 inferior). Most targets are only completely inactive or completely
4657 active, but some support persistent connections to a target even
4658 when the target has exited or not yet started.
4660 For example, connecting to the simulator using @code{target sim} does
4661 not create a running program. Neither registers nor memory are
4662 accessible until @code{run}. Similarly, after @code{kill}, the
4663 program can not continue executing. But in both cases @value{GDBN}
4664 remains connected to the simulator, and target-specific commands
4665 are directed to the simulator.
4667 A target which only supports complete activation should push itself
4668 onto the stack in its @code{to_open} routine (by calling
4669 @code{push_target}), and unpush itself from the stack in its
4670 @code{to_mourn_inferior} routine (by calling @code{unpush_target}).
4672 A target which supports both partial and complete activation should
4673 still call @code{push_target} in @code{to_open}, but not call
4674 @code{unpush_target} in @code{to_mourn_inferior}. Instead, it should
4675 call either @code{target_mark_running} or @code{target_mark_exited}
4676 in its @code{to_open}, depending on whether the target is fully active
4677 after connection. It should also call @code{target_mark_running} any
4678 time the inferior becomes fully active (e.g.@: in
4679 @code{to_create_inferior} and @code{to_attach}), and
4680 @code{target_mark_exited} when the inferior becomes inactive (in
4681 @code{to_mourn_inferior}). The target should also make sure to call
4682 @code{target_mourn_inferior} from its @code{to_kill}, to return the
4683 target to inactive state.
4685 @node Existing Targets
4686 @section Existing Targets
4689 @subsection File Targets
4691 Both executables and core files have target vectors.
4693 @subsection Standard Protocol and Remote Stubs
4695 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4696 that runs in the target system. @value{GDBN} provides several sample
4697 @dfn{stubs} that can be integrated into target programs or operating
4698 systems for this purpose; they are named @file{*-stub.c}.
4700 The @value{GDBN} user's manual describes how to put such a stub into
4701 your target code. What follows is a discussion of integrating the
4702 SPARC stub into a complicated operating system (rather than a simple
4703 program), by Stu Grossman, the author of this stub.
4705 The trap handling code in the stub assumes the following upon entry to
4710 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4716 you are in the correct trap window.
4719 As long as your trap handler can guarantee those conditions, then there
4720 is no reason why you shouldn't be able to ``share'' traps with the stub.
4721 The stub has no requirement that it be jumped to directly from the
4722 hardware trap vector. That is why it calls @code{exceptionHandler()},
4723 which is provided by the external environment. For instance, this could
4724 set up the hardware traps to actually execute code which calls the stub
4725 first, and then transfers to its own trap handler.
4727 For the most point, there probably won't be much of an issue with
4728 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4729 and often indicate unrecoverable error conditions. Anyway, this is all
4730 controlled by a table, and is trivial to modify. The most important
4731 trap for us is for @code{ta 1}. Without that, we can't single step or
4732 do breakpoints. Everything else is unnecessary for the proper operation
4733 of the debugger/stub.
4735 From reading the stub, it's probably not obvious how breakpoints work.
4736 They are simply done by deposit/examine operations from @value{GDBN}.
4738 @subsection ROM Monitor Interface
4740 @subsection Custom Protocols
4742 @subsection Transport Layer
4744 @subsection Builtin Simulator
4747 @node Native Debugging
4749 @chapter Native Debugging
4750 @cindex native debugging
4752 Several files control @value{GDBN}'s configuration for native support:
4756 @item gdb/config/@var{arch}/@var{xyz}.mh
4757 Specifies Makefile fragments needed by a @emph{native} configuration on
4758 machine @var{xyz}. In particular, this lists the required
4759 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4760 Also specifies the header file which describes native support on
4761 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4762 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4763 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4765 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4766 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4767 on machine @var{xyz}. While the file is no longer used for this
4768 purpose, the @file{.mh} suffix remains. Perhaps someone will
4769 eventually rename these fragments so that they have a @file{.mn}
4772 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4773 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4774 macro definitions describing the native system environment, such as
4775 child process control and core file support.
4777 @item gdb/@var{xyz}-nat.c
4778 Contains any miscellaneous C code required for this native support of
4779 this machine. On some machines it doesn't exist at all.
4782 There are some ``generic'' versions of routines that can be used by
4783 various systems. These can be customized in various ways by macros
4784 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4785 the @var{xyz} host, you can just include the generic file's name (with
4786 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4788 Otherwise, if your machine needs custom support routines, you will need
4789 to write routines that perform the same functions as the generic file.
4790 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4791 into @code{NATDEPFILES}.
4795 This contains the @emph{target_ops vector} that supports Unix child
4796 processes on systems which use ptrace and wait to control the child.
4799 This contains the @emph{target_ops vector} that supports Unix child
4800 processes on systems which use /proc to control the child.
4803 This does the low-level grunge that uses Unix system calls to do a ``fork
4804 and exec'' to start up a child process.
4807 This is the low level interface to inferior processes for systems using
4808 the Unix @code{ptrace} call in a vanilla way.
4811 @section Native core file Support
4812 @cindex native core files
4815 @findex fetch_core_registers
4816 @item core-aout.c::fetch_core_registers()
4817 Support for reading registers out of a core file. This routine calls
4818 @code{register_addr()}, see below. Now that BFD is used to read core
4819 files, virtually all machines should use @code{core-aout.c}, and should
4820 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4821 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4823 @item core-aout.c::register_addr()
4824 If your @code{nm-@var{xyz}.h} file defines the macro
4825 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4826 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4827 register number @code{regno}. @code{blockend} is the offset within the
4828 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4829 @file{core-aout.c} will define the @code{register_addr()} function and
4830 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4831 you are using the standard @code{fetch_core_registers()}, you will need
4832 to define your own version of @code{register_addr()}, put it into your
4833 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4834 the @code{NATDEPFILES} list. If you have your own
4835 @code{fetch_core_registers()}, you may not need a separate
4836 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4837 implementations simply locate the registers themselves.@refill
4840 When making @value{GDBN} run native on a new operating system, to make it
4841 possible to debug core files, you will need to either write specific
4842 code for parsing your OS's core files, or customize
4843 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4844 machine uses to define the struct of registers that is accessible
4845 (possibly in the u-area) in a core file (rather than
4846 @file{machine/reg.h}), and an include file that defines whatever header
4847 exists on a core file (e.g., the u-area or a @code{struct core}). Then
4848 modify @code{trad_unix_core_file_p} to use these values to set up the
4849 section information for the data segment, stack segment, any other
4850 segments in the core file (perhaps shared library contents or control
4851 information), ``registers'' segment, and if there are two discontiguous
4852 sets of registers (e.g., integer and float), the ``reg2'' segment. This
4853 section information basically delimits areas in the core file in a
4854 standard way, which the section-reading routines in BFD know how to seek
4857 Then back in @value{GDBN}, you need a matching routine called
4858 @code{fetch_core_registers}. If you can use the generic one, it's in
4859 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4860 It will be passed a char pointer to the entire ``registers'' segment,
4861 its length, and a zero; or a char pointer to the entire ``regs2''
4862 segment, its length, and a 2. The routine should suck out the supplied
4863 register values and install them into @value{GDBN}'s ``registers'' array.
4865 If your system uses @file{/proc} to control processes, and uses ELF
4866 format core files, then you may be able to use the same routines for
4867 reading the registers out of processes and out of core files.
4875 @section shared libraries
4877 @section Native Conditionals
4878 @cindex native conditionals
4880 When @value{GDBN} is configured and compiled, various macros are
4881 defined or left undefined, to control compilation when the host and
4882 target systems are the same. These macros should be defined (or left
4883 undefined) in @file{nm-@var{system}.h}.
4887 @item CHILD_PREPARE_TO_STORE
4888 @findex CHILD_PREPARE_TO_STORE
4889 If the machine stores all registers at once in the child process, then
4890 define this to ensure that all values are correct. This usually entails
4891 a read from the child.
4893 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4896 @item FETCH_INFERIOR_REGISTERS
4897 @findex FETCH_INFERIOR_REGISTERS
4898 Define this if the native-dependent code will provide its own routines
4899 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4900 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4901 @file{infptrace.c} is included in this configuration, the default
4902 routines in @file{infptrace.c} are used for these functions.
4906 This macro is normally defined to be the number of the first floating
4907 point register, if the machine has such registers. As such, it would
4908 appear only in target-specific code. However, @file{/proc} support uses this
4909 to decide whether floats are in use on this target.
4911 @item GET_LONGJMP_TARGET
4912 @findex GET_LONGJMP_TARGET
4913 For most machines, this is a target-dependent parameter. On the
4914 DECstation and the Iris, this is a native-dependent parameter, since
4915 @file{setjmp.h} is needed to define it.
4917 This macro determines the target PC address that @code{longjmp} will jump to,
4918 assuming that we have just stopped at a longjmp breakpoint. It takes a
4919 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4920 pointer. It examines the current state of the machine as needed.
4922 @item I386_USE_GENERIC_WATCHPOINTS
4923 An x86-based machine can define this to use the generic x86 watchpoint
4924 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4927 @findex KERNEL_U_ADDR
4928 Define this to the address of the @code{u} structure (the ``user
4929 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4930 needs to know this so that it can subtract this address from absolute
4931 addresses in the upage, that are obtained via ptrace or from core files.
4932 On systems that don't need this value, set it to zero.
4934 @item KERNEL_U_ADDR_HPUX
4935 @findex KERNEL_U_ADDR_HPUX
4936 Define this to cause @value{GDBN} to determine the address of @code{u} at
4937 runtime, by using HP-style @code{nlist} on the kernel's image in the
4940 @item ONE_PROCESS_WRITETEXT
4941 @findex ONE_PROCESS_WRITETEXT
4942 Define this to be able to, when a breakpoint insertion fails, warn the
4943 user that another process may be running with the same executable.
4946 @findex PROC_NAME_FMT
4947 Defines the format for the name of a @file{/proc} device. Should be
4948 defined in @file{nm.h} @emph{only} in order to override the default
4949 definition in @file{procfs.c}.
4951 @item REGISTER_U_ADDR
4952 @findex REGISTER_U_ADDR
4953 Defines the offset of the registers in the ``u area''.
4955 @item SHELL_COMMAND_CONCAT
4956 @findex SHELL_COMMAND_CONCAT
4957 If defined, is a string to prefix on the shell command used to start the
4962 If defined, this is the name of the shell to use to run the inferior.
4963 Defaults to @code{"/bin/sh"}.
4965 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4967 Define this to expand into an expression that will cause the symbols in
4968 @var{filename} to be added to @value{GDBN}'s symbol table. If
4969 @var{readsyms} is zero symbols are not read but any necessary low level
4970 processing for @var{filename} is still done.
4972 @item SOLIB_CREATE_INFERIOR_HOOK
4973 @findex SOLIB_CREATE_INFERIOR_HOOK
4974 Define this to expand into any shared-library-relocation code that you
4975 want to be run just after the child process has been forked.
4977 @item START_INFERIOR_TRAPS_EXPECTED
4978 @findex START_INFERIOR_TRAPS_EXPECTED
4979 When starting an inferior, @value{GDBN} normally expects to trap
4981 the shell execs, and once when the program itself execs. If the actual
4982 number of traps is something other than 2, then define this macro to
4983 expand into the number expected.
4987 This determines whether small routines in @file{*-tdep.c}, which
4988 translate register values between @value{GDBN}'s internal
4989 representation and the @file{/proc} representation, are compiled.
4992 @findex U_REGS_OFFSET
4993 This is the offset of the registers in the upage. It need only be
4994 defined if the generic ptrace register access routines in
4995 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4996 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4997 the default value from @file{infptrace.c} is good enough, leave it
5000 The default value means that u.u_ar0 @emph{points to} the location of
5001 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
5002 that @code{u.u_ar0} @emph{is} the location of the registers.
5006 See @file{objfiles.c}.
5009 @findex DEBUG_PTRACE
5010 Define this to debug @code{ptrace} calls.
5014 @node Support Libraries
5016 @chapter Support Libraries
5021 BFD provides support for @value{GDBN} in several ways:
5024 @item identifying executable and core files
5025 BFD will identify a variety of file types, including a.out, coff, and
5026 several variants thereof, as well as several kinds of core files.
5028 @item access to sections of files
5029 BFD parses the file headers to determine the names, virtual addresses,
5030 sizes, and file locations of all the various named sections in files
5031 (such as the text section or the data section). @value{GDBN} simply
5032 calls BFD to read or write section @var{x} at byte offset @var{y} for
5035 @item specialized core file support
5036 BFD provides routines to determine the failing command name stored in a
5037 core file, the signal with which the program failed, and whether a core
5038 file matches (i.e.@: could be a core dump of) a particular executable
5041 @item locating the symbol information
5042 @value{GDBN} uses an internal interface of BFD to determine where to find the
5043 symbol information in an executable file or symbol-file. @value{GDBN} itself
5044 handles the reading of symbols, since BFD does not ``understand'' debug
5045 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
5050 @cindex opcodes library
5052 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
5053 library because it's also used in binutils, for @file{objdump}).
5056 @cindex readline library
5057 The @code{readline} library provides a set of functions for use by applications
5058 that allow users to edit command lines as they are typed in.
5061 @cindex @code{libiberty} library
5063 The @code{libiberty} library provides a set of functions and features
5064 that integrate and improve on functionality found in modern operating
5065 systems. Broadly speaking, such features can be divided into three
5066 groups: supplemental functions (functions that may be missing in some
5067 environments and operating systems), replacement functions (providing
5068 a uniform and easier to use interface for commonly used standard
5069 functions), and extensions (which provide additional functionality
5070 beyond standard functions).
5072 @value{GDBN} uses various features provided by the @code{libiberty}
5073 library, for instance the C@t{++} demangler, the @acronym{IEEE}
5074 floating format support functions, the input options parser
5075 @samp{getopt}, the @samp{obstack} extension, and other functions.
5077 @subsection @code{obstacks} in @value{GDBN}
5078 @cindex @code{obstacks}
5080 The obstack mechanism provides a convenient way to allocate and free
5081 chunks of memory. Each obstack is a pool of memory that is managed
5082 like a stack. Objects (of any nature, size and alignment) are
5083 allocated and freed in a @acronym{LIFO} fashion on an obstack (see
5084 @code{libiberty}'s documentation for a more detailed explanation of
5087 The most noticeable use of the @code{obstacks} in @value{GDBN} is in
5088 object files. There is an obstack associated with each internal
5089 representation of an object file. Lots of things get allocated on
5090 these @code{obstacks}: dictionary entries, blocks, blockvectors,
5091 symbols, minimal symbols, types, vectors of fundamental types, class
5092 fields of types, object files section lists, object files section
5093 offset lists, line tables, symbol tables, partial symbol tables,
5094 string tables, symbol table private data, macros tables, debug
5095 information sections and entries, import and export lists (som),
5096 unwind information (hppa), dwarf2 location expressions data. Plus
5097 various strings such as directory names strings, debug format strings,
5100 An essential and convenient property of all data on @code{obstacks} is
5101 that memory for it gets allocated (with @code{obstack_alloc}) at
5102 various times during a debugging session, but it is released all at
5103 once using the @code{obstack_free} function. The @code{obstack_free}
5104 function takes a pointer to where in the stack it must start the
5105 deletion from (much like the cleanup chains have a pointer to where to
5106 start the cleanups). Because of the stack like structure of the
5107 @code{obstacks}, this allows to free only a top portion of the
5108 obstack. There are a few instances in @value{GDBN} where such thing
5109 happens. Calls to @code{obstack_free} are done after some local data
5110 is allocated to the obstack. Only the local data is deleted from the
5111 obstack. Of course this assumes that nothing between the
5112 @code{obstack_alloc} and the @code{obstack_free} allocates anything
5113 else on the same obstack. For this reason it is best and safest to
5114 use temporary @code{obstacks}.
5116 Releasing the whole obstack is also not safe per se. It is safe only
5117 under the condition that we know the @code{obstacks} memory is no
5118 longer needed. In @value{GDBN} we get rid of the @code{obstacks} only
5119 when we get rid of the whole objfile(s), for instance upon reading a
5123 @cindex regular expressions library
5134 @item SIGN_EXTEND_CHAR
5136 @item SWITCH_ENUM_BUG
5145 @section Array Containers
5146 @cindex Array Containers
5149 Often it is necessary to manipulate a dynamic array of a set of
5150 objects. C forces some bookkeeping on this, which can get cumbersome
5151 and repetitive. The @file{vec.h} file contains macros for defining
5152 and using a typesafe vector type. The functions defined will be
5153 inlined when compiling, and so the abstraction cost should be zero.
5154 Domain checks are added to detect programming errors.
5156 An example use would be an array of symbols or section information.
5157 The array can be grown as symbols are read in (or preallocated), and
5158 the accessor macros provided keep care of all the necessary
5159 bookkeeping. Because the arrays are type safe, there is no danger of
5160 accidentally mixing up the contents. Think of these as C++ templates,
5161 but implemented in C.
5163 Because of the different behavior of structure objects, scalar objects
5164 and of pointers, there are three flavors of vector, one for each of
5165 these variants. Both the structure object and pointer variants pass
5166 pointers to objects around --- in the former case the pointers are
5167 stored into the vector and in the latter case the pointers are
5168 dereferenced and the objects copied into the vector. The scalar
5169 object variant is suitable for @code{int}-like objects, and the vector
5170 elements are returned by value.
5172 There are both @code{index} and @code{iterate} accessors. The iterator
5173 returns a boolean iteration condition and updates the iteration
5174 variable passed by reference. Because the iterator will be inlined,
5175 the address-of can be optimized away.
5177 The vectors are implemented using the trailing array idiom, thus they
5178 are not resizeable without changing the address of the vector object
5179 itself. This means you cannot have variables or fields of vector type
5180 --- always use a pointer to a vector. The one exception is the final
5181 field of a structure, which could be a vector type. You will have to
5182 use the @code{embedded_size} & @code{embedded_init} calls to create
5183 such objects, and they will probably not be resizeable (so don't use
5184 the @dfn{safe} allocation variants). The trailing array idiom is used
5185 (rather than a pointer to an array of data), because, if we allow
5186 @code{NULL} to also represent an empty vector, empty vectors occupy
5187 minimal space in the structure containing them.
5189 Each operation that increases the number of active elements is
5190 available in @dfn{quick} and @dfn{safe} variants. The former presumes
5191 that there is sufficient allocated space for the operation to succeed
5192 (it dies if there is not). The latter will reallocate the vector, if
5193 needed. Reallocation causes an exponential increase in vector size.
5194 If you know you will be adding N elements, it would be more efficient
5195 to use the reserve operation before adding the elements with the
5196 @dfn{quick} operation. This will ensure there are at least as many
5197 elements as you ask for, it will exponentially increase if there are
5198 too few spare slots. If you want reserve a specific number of slots,
5199 but do not want the exponential increase (for instance, you know this
5200 is the last allocation), use a negative number for reservation. You
5201 can also create a vector of a specific size from the get go.
5203 You should prefer the push and pop operations, as they append and
5204 remove from the end of the vector. If you need to remove several items
5205 in one go, use the truncate operation. The insert and remove
5206 operations allow you to change elements in the middle of the vector.
5207 There are two remove operations, one which preserves the element
5208 ordering @code{ordered_remove}, and one which does not
5209 @code{unordered_remove}. The latter function copies the end element
5210 into the removed slot, rather than invoke a memmove operation. The
5211 @code{lower_bound} function will determine where to place an item in
5212 the array using insert that will maintain sorted order.
5214 If you need to directly manipulate a vector, then the @code{address}
5215 accessor will return the address of the start of the vector. Also the
5216 @code{space} predicate will tell you whether there is spare capacity in the
5217 vector. You will not normally need to use these two functions.
5219 Vector types are defined using a
5220 @code{DEF_VEC_@{O,P,I@}(@var{typename})} macro. Variables of vector
5221 type are declared using a @code{VEC(@var{typename})} macro. The
5222 characters @code{O}, @code{P} and @code{I} indicate whether
5223 @var{typename} is an object (@code{O}), pointer (@code{P}) or integral
5224 (@code{I}) type. Be careful to pick the correct one, as you'll get an
5225 awkward and inefficient API if you use the wrong one. There is a
5226 check, which results in a compile-time warning, for the @code{P} and
5227 @code{I} versions, but there is no check for the @code{O} versions, as
5228 that is not possible in plain C.
5230 An example of their use would be,
5233 DEF_VEC_P(tree); // non-managed tree vector.
5236 VEC(tree) *v; // A (pointer to) a vector of tree pointers.
5239 struct my_struct *s;
5241 if (VEC_length(tree, s->v)) @{ we have some contents @}
5242 VEC_safe_push(tree, s->v, decl); // append some decl onto the end
5243 for (ix = 0; VEC_iterate(tree, s->v, ix, elt); ix++)
5244 @{ do something with elt @}
5248 The @file{vec.h} file provides details on how to invoke the various
5249 accessors provided. They are enumerated here:
5253 Return the number of items in the array,
5256 Return true if the array has no elements.
5260 Return the last or arbitrary item in the array.
5263 Access an array element and indicate whether the array has been
5268 Create and destroy an array.
5270 @item VEC_embedded_size
5271 @itemx VEC_embedded_init
5272 Helpers for embedding an array as the final element of another struct.
5278 Return the amount of free space in an array.
5281 Ensure a certain amount of free space.
5283 @item VEC_quick_push
5284 @itemx VEC_safe_push
5285 Append to an array, either assuming the space is available, or making
5289 Remove the last item from an array.
5292 Remove several items from the end of an array.
5295 Add several items to the end of an array.
5298 Overwrite an item in the array.
5300 @item VEC_quick_insert
5301 @itemx VEC_safe_insert
5302 Insert an item into the middle of the array. Either the space must
5303 already exist, or the space is created.
5305 @item VEC_ordered_remove
5306 @itemx VEC_unordered_remove
5307 Remove an item from the array, preserving order or not.
5309 @item VEC_block_remove
5310 Remove a set of items from the array.
5313 Provide the address of the first element.
5315 @item VEC_lower_bound
5316 Binary search the array.
5326 This chapter covers topics that are lower-level than the major
5327 algorithms of @value{GDBN}.
5332 Cleanups are a structured way to deal with things that need to be done
5335 When your code does something (e.g., @code{xmalloc} some memory, or
5336 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
5337 the memory or @code{close} the file), it can make a cleanup. The
5338 cleanup will be done at some future point: when the command is finished
5339 and control returns to the top level; when an error occurs and the stack
5340 is unwound; or when your code decides it's time to explicitly perform
5341 cleanups. Alternatively you can elect to discard the cleanups you
5347 @item struct cleanup *@var{old_chain};
5348 Declare a variable which will hold a cleanup chain handle.
5350 @findex make_cleanup
5351 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
5352 Make a cleanup which will cause @var{function} to be called with
5353 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
5354 handle that can later be passed to @code{do_cleanups} or
5355 @code{discard_cleanups}. Unless you are going to call
5356 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
5357 from @code{make_cleanup}.
5360 @item do_cleanups (@var{old_chain});
5361 Do all cleanups added to the chain since the corresponding
5362 @code{make_cleanup} call was made.
5364 @findex discard_cleanups
5365 @item discard_cleanups (@var{old_chain});
5366 Same as @code{do_cleanups} except that it just removes the cleanups from
5367 the chain and does not call the specified functions.
5370 Cleanups are implemented as a chain. The handle returned by
5371 @code{make_cleanups} includes the cleanup passed to the call and any
5372 later cleanups appended to the chain (but not yet discarded or
5376 make_cleanup (a, 0);
5378 struct cleanup *old = make_cleanup (b, 0);
5386 will call @code{c()} and @code{b()} but will not call @code{a()}. The
5387 cleanup that calls @code{a()} will remain in the cleanup chain, and will
5388 be done later unless otherwise discarded.@refill
5390 Your function should explicitly do or discard the cleanups it creates.
5391 Failing to do this leads to non-deterministic behavior since the caller
5392 will arbitrarily do or discard your functions cleanups. This need leads
5393 to two common cleanup styles.
5395 The first style is try/finally. Before it exits, your code-block calls
5396 @code{do_cleanups} with the old cleanup chain and thus ensures that your
5397 code-block's cleanups are always performed. For instance, the following
5398 code-segment avoids a memory leak problem (even when @code{error} is
5399 called and a forced stack unwind occurs) by ensuring that the
5400 @code{xfree} will always be called:
5403 struct cleanup *old = make_cleanup (null_cleanup, 0);
5404 data = xmalloc (sizeof blah);
5405 make_cleanup (xfree, data);
5410 The second style is try/except. Before it exits, your code-block calls
5411 @code{discard_cleanups} with the old cleanup chain and thus ensures that
5412 any created cleanups are not performed. For instance, the following
5413 code segment, ensures that the file will be closed but only if there is
5417 FILE *file = fopen ("afile", "r");
5418 struct cleanup *old = make_cleanup (close_file, file);
5420 discard_cleanups (old);
5424 Some functions, e.g., @code{fputs_filtered()} or @code{error()}, specify
5425 that they ``should not be called when cleanups are not in place''. This
5426 means that any actions you need to reverse in the case of an error or
5427 interruption must be on the cleanup chain before you call these
5428 functions, since they might never return to your code (they
5429 @samp{longjmp} instead).
5431 @section Per-architecture module data
5432 @cindex per-architecture module data
5433 @cindex multi-arch data
5434 @cindex data-pointer, per-architecture/per-module
5436 The multi-arch framework includes a mechanism for adding module
5437 specific per-architecture data-pointers to the @code{struct gdbarch}
5438 architecture object.
5440 A module registers one or more per-architecture data-pointers using:
5442 @deftypefun struct gdbarch_data *gdbarch_data_register_pre_init (gdbarch_data_pre_init_ftype *@var{pre_init})
5443 @var{pre_init} is used to, on-demand, allocate an initial value for a
5444 per-architecture data-pointer using the architecture's obstack (passed
5445 in as a parameter). Since @var{pre_init} can be called during
5446 architecture creation, it is not parameterized with the architecture.
5447 and must not call modules that use per-architecture data.
5450 @deftypefun struct gdbarch_data *gdbarch_data_register_post_init (gdbarch_data_post_init_ftype *@var{post_init})
5451 @var{post_init} is used to obtain an initial value for a
5452 per-architecture data-pointer @emph{after}. Since @var{post_init} is
5453 always called after architecture creation, it both receives the fully
5454 initialized architecture and is free to call modules that use
5455 per-architecture data (care needs to be taken to ensure that those
5456 other modules do not try to call back to this module as that will
5457 create in cycles in the initialization call graph).
5460 These functions return a @code{struct gdbarch_data} that is used to
5461 identify the per-architecture data-pointer added for that module.
5463 The per-architecture data-pointer is accessed using the function:
5465 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
5466 Given the architecture @var{arch} and module data handle
5467 @var{data_handle} (returned by @code{gdbarch_data_register_pre_init}
5468 or @code{gdbarch_data_register_post_init}), this function returns the
5469 current value of the per-architecture data-pointer. If the data
5470 pointer is @code{NULL}, it is first initialized by calling the
5471 corresponding @var{pre_init} or @var{post_init} method.
5474 The examples below assume the following definitions:
5477 struct nozel @{ int total; @};
5478 static struct gdbarch_data *nozel_handle;
5481 A module can extend the architecture vector, adding additional
5482 per-architecture data, using the @var{pre_init} method. The module's
5483 per-architecture data is then initialized during architecture
5486 In the below, the module's per-architecture @emph{nozel} is added. An
5487 architecture can specify its nozel by calling @code{set_gdbarch_nozel}
5488 from @code{gdbarch_init}.
5492 nozel_pre_init (struct obstack *obstack)
5494 struct nozel *data = OBSTACK_ZALLOC (obstack, struct nozel);
5501 set_gdbarch_nozel (struct gdbarch *gdbarch, int total)
5503 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5504 data->total = nozel;
5508 A module can on-demand create architecture dependant data structures
5509 using @code{post_init}.
5511 In the below, the nozel's total is computed on-demand by
5512 @code{nozel_post_init} using information obtained from the
5517 nozel_post_init (struct gdbarch *gdbarch)
5519 struct nozel *data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct nozel);
5520 nozel->total = gdbarch@dots{} (gdbarch);
5527 nozel_total (struct gdbarch *gdbarch)
5529 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
5534 @section Wrapping Output Lines
5535 @cindex line wrap in output
5538 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
5539 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
5540 added in places that would be good breaking points. The utility
5541 routines will take care of actually wrapping if the line width is
5544 The argument to @code{wrap_here} is an indentation string which is
5545 printed @emph{only} if the line breaks there. This argument is saved
5546 away and used later. It must remain valid until the next call to
5547 @code{wrap_here} or until a newline has been printed through the
5548 @code{*_filtered} functions. Don't pass in a local variable and then
5551 It is usually best to call @code{wrap_here} after printing a comma or
5552 space. If you call it before printing a space, make sure that your
5553 indentation properly accounts for the leading space that will print if
5554 the line wraps there.
5556 Any function or set of functions that produce filtered output must
5557 finish by printing a newline, to flush the wrap buffer, before switching
5558 to unfiltered (@code{printf}) output. Symbol reading routines that
5559 print warnings are a good example.
5561 @section @value{GDBN} Coding Standards
5562 @cindex coding standards
5564 @value{GDBN} follows the GNU coding standards, as described in
5565 @file{etc/standards.texi}. This file is also available for anonymous
5566 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
5567 of the standard; in general, when the GNU standard recommends a practice
5568 but does not require it, @value{GDBN} requires it.
5570 @value{GDBN} follows an additional set of coding standards specific to
5571 @value{GDBN}, as described in the following sections.
5576 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
5579 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
5582 @subsection Memory Management
5584 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
5585 @code{calloc}, @code{free} and @code{asprintf}.
5587 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
5588 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
5589 these functions do not return when the memory pool is empty. Instead,
5590 they unwind the stack using cleanups. These functions return
5591 @code{NULL} when requested to allocate a chunk of memory of size zero.
5593 @emph{Pragmatics: By using these functions, the need to check every
5594 memory allocation is removed. These functions provide portable
5597 @value{GDBN} does not use the function @code{free}.
5599 @value{GDBN} uses the function @code{xfree} to return memory to the
5600 memory pool. Consistent with ISO-C, this function ignores a request to
5601 free a @code{NULL} pointer.
5603 @emph{Pragmatics: On some systems @code{free} fails when passed a
5604 @code{NULL} pointer.}
5606 @value{GDBN} can use the non-portable function @code{alloca} for the
5607 allocation of small temporary values (such as strings).
5609 @emph{Pragmatics: This function is very non-portable. Some systems
5610 restrict the memory being allocated to no more than a few kilobytes.}
5612 @value{GDBN} uses the string function @code{xstrdup} and the print
5613 function @code{xstrprintf}.
5615 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
5616 functions such as @code{sprintf} are very prone to buffer overflow
5620 @subsection Compiler Warnings
5621 @cindex compiler warnings
5623 With few exceptions, developers should avoid the configuration option
5624 @samp{--disable-werror} when building @value{GDBN}. The exceptions
5625 are listed in the file @file{gdb/MAINTAINERS}. The default, when
5626 building with @sc{gcc}, is @samp{--enable-werror}.
5628 This option causes @value{GDBN} (when built using GCC) to be compiled
5629 with a carefully selected list of compiler warning flags. Any warnings
5630 from those flags are treated as errors.
5632 The current list of warning flags includes:
5636 Recommended @sc{gcc} warnings.
5638 @item -Wdeclaration-after-statement
5640 @sc{gcc} 3.x (and later) and @sc{c99} allow declarations mixed with
5641 code, but @sc{gcc} 2.x and @sc{c89} do not.
5643 @item -Wpointer-arith
5645 @item -Wformat-nonliteral
5646 Non-literal format strings, with a few exceptions, are bugs - they
5647 might contain unintended user-supplied format specifiers.
5648 Since @value{GDBN} uses the @code{format printf} attribute on all
5649 @code{printf} like functions this checks not just @code{printf} calls
5650 but also calls to functions such as @code{fprintf_unfiltered}.
5652 @item -Wno-pointer-sign
5653 In version 4.0, GCC began warning about pointer argument passing or
5654 assignment even when the source and destination differed only in
5655 signedness. However, most @value{GDBN} code doesn't distinguish
5656 carefully between @code{char} and @code{unsigned char}. In early 2006
5657 the @value{GDBN} developers decided correcting these warnings wasn't
5658 worth the time it would take.
5660 @item -Wno-unused-parameter
5661 Due to the way that @value{GDBN} is implemented many functions have
5662 unused parameters. Consequently this warning is avoided. The macro
5663 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
5664 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
5669 These are warnings which might be useful for @value{GDBN}, but are
5670 currently too noisy to enable with @samp{-Werror}.
5674 @subsection Formatting
5676 @cindex source code formatting
5677 The standard GNU recommendations for formatting must be followed
5680 A function declaration should not have its name in column zero. A
5681 function definition should have its name in column zero.
5685 static void foo (void);
5693 @emph{Pragmatics: This simplifies scripting. Function definitions can
5694 be found using @samp{^function-name}.}
5696 There must be a space between a function or macro name and the opening
5697 parenthesis of its argument list (except for macro definitions, as
5698 required by C). There must not be a space after an open paren/bracket
5699 or before a close paren/bracket.
5701 While additional whitespace is generally helpful for reading, do not use
5702 more than one blank line to separate blocks, and avoid adding whitespace
5703 after the end of a program line (as of 1/99, some 600 lines had
5704 whitespace after the semicolon). Excess whitespace causes difficulties
5705 for @code{diff} and @code{patch} utilities.
5707 Pointers are declared using the traditional K&R C style:
5721 @subsection Comments
5723 @cindex comment formatting
5724 The standard GNU requirements on comments must be followed strictly.
5726 Block comments must appear in the following form, with no @code{/*}- or
5727 @code{*/}-only lines, and no leading @code{*}:
5730 /* Wait for control to return from inferior to debugger. If inferior
5731 gets a signal, we may decide to start it up again instead of
5732 returning. That is why there is a loop in this function. When
5733 this function actually returns it means the inferior should be left
5734 stopped and @value{GDBN} should read more commands. */
5737 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5738 comment works correctly, and @kbd{M-q} fills the block consistently.)
5740 Put a blank line between the block comments preceding function or
5741 variable definitions, and the definition itself.
5743 In general, put function-body comments on lines by themselves, rather
5744 than trying to fit them into the 20 characters left at the end of a
5745 line, since either the comment or the code will inevitably get longer
5746 than will fit, and then somebody will have to move it anyhow.
5750 @cindex C data types
5751 Code must not depend on the sizes of C data types, the format of the
5752 host's floating point numbers, the alignment of anything, or the order
5753 of evaluation of expressions.
5755 @cindex function usage
5756 Use functions freely. There are only a handful of compute-bound areas
5757 in @value{GDBN} that might be affected by the overhead of a function
5758 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5759 limited by the target interface (whether serial line or system call).
5761 However, use functions with moderation. A thousand one-line functions
5762 are just as hard to understand as a single thousand-line function.
5764 @emph{Macros are bad, M'kay.}
5765 (But if you have to use a macro, make sure that the macro arguments are
5766 protected with parentheses.)
5770 Declarations like @samp{struct foo *} should be used in preference to
5771 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5774 @subsection Function Prototypes
5775 @cindex function prototypes
5777 Prototypes must be used when both @emph{declaring} and @emph{defining}
5778 a function. Prototypes for @value{GDBN} functions must include both the
5779 argument type and name, with the name matching that used in the actual
5780 function definition.
5782 All external functions should have a declaration in a header file that
5783 callers include, except for @code{_initialize_*} functions, which must
5784 be external so that @file{init.c} construction works, but shouldn't be
5785 visible to random source files.
5787 Where a source file needs a forward declaration of a static function,
5788 that declaration must appear in a block near the top of the source file.
5791 @subsection Internal Error Recovery
5793 During its execution, @value{GDBN} can encounter two types of errors.
5794 User errors and internal errors. User errors include not only a user
5795 entering an incorrect command but also problems arising from corrupt
5796 object files and system errors when interacting with the target.
5797 Internal errors include situations where @value{GDBN} has detected, at
5798 run time, a corrupt or erroneous situation.
5800 When reporting an internal error, @value{GDBN} uses
5801 @code{internal_error} and @code{gdb_assert}.
5803 @value{GDBN} must not call @code{abort} or @code{assert}.
5805 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5806 the code detected a user error, recovered from it and issued a
5807 @code{warning} or the code failed to correctly recover from the user
5808 error and issued an @code{internal_error}.}
5810 @subsection File Names
5812 Any file used when building the core of @value{GDBN} must be in lower
5813 case. Any file used when building the core of @value{GDBN} must be 8.3
5814 unique. These requirements apply to both source and generated files.
5816 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5817 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5818 is introduced to the build process both @file{Makefile.in} and
5819 @file{configure.in} need to be modified accordingly. Compare the
5820 convoluted conversion process needed to transform @file{COPYING} into
5821 @file{copying.c} with the conversion needed to transform
5822 @file{version.in} into @file{version.c}.}
5824 Any file non 8.3 compliant file (that is not used when building the core
5825 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5827 @emph{Pragmatics: This is clearly a compromise.}
5829 When @value{GDBN} has a local version of a system header file (ex
5830 @file{string.h}) the file name based on the POSIX header prefixed with
5831 @file{gdb_} (@file{gdb_string.h}). These headers should be relatively
5832 independent: they should use only macros defined by @file{configure},
5833 the compiler, or the host; they should include only system headers; they
5834 should refer only to system types. They may be shared between multiple
5835 programs, e.g.@: @value{GDBN} and @sc{gdbserver}.
5837 For other files @samp{-} is used as the separator.
5840 @subsection Include Files
5842 A @file{.c} file should include @file{defs.h} first.
5844 A @file{.c} file should directly include the @code{.h} file of every
5845 declaration and/or definition it directly refers to. It cannot rely on
5848 A @file{.h} file should directly include the @code{.h} file of every
5849 declaration and/or definition it directly refers to. It cannot rely on
5850 indirect inclusion. Exception: The file @file{defs.h} does not need to
5851 be directly included.
5853 An external declaration should only appear in one include file.
5855 An external declaration should never appear in a @code{.c} file.
5856 Exception: a declaration for the @code{_initialize} function that
5857 pacifies @option{-Wmissing-declaration}.
5859 A @code{typedef} definition should only appear in one include file.
5861 An opaque @code{struct} declaration can appear in multiple @file{.h}
5862 files. Where possible, a @file{.h} file should use an opaque
5863 @code{struct} declaration instead of an include.
5865 All @file{.h} files should be wrapped in:
5868 #ifndef INCLUDE_FILE_NAME_H
5869 #define INCLUDE_FILE_NAME_H
5875 @subsection Clean Design and Portable Implementation
5878 In addition to getting the syntax right, there's the little question of
5879 semantics. Some things are done in certain ways in @value{GDBN} because long
5880 experience has shown that the more obvious ways caused various kinds of
5883 @cindex assumptions about targets
5884 You can't assume the byte order of anything that comes from a target
5885 (including @var{value}s, object files, and instructions). Such things
5886 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5887 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5888 such as @code{bfd_get_32}.
5890 You can't assume that you know what interface is being used to talk to
5891 the target system. All references to the target must go through the
5892 current @code{target_ops} vector.
5894 You can't assume that the host and target machines are the same machine
5895 (except in the ``native'' support modules). In particular, you can't
5896 assume that the target machine's header files will be available on the
5897 host machine. Target code must bring along its own header files --
5898 written from scratch or explicitly donated by their owner, to avoid
5902 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5903 to write the code portably than to conditionalize it for various
5906 @cindex system dependencies
5907 New @code{#ifdef}'s which test for specific compilers or manufacturers
5908 or operating systems are unacceptable. All @code{#ifdef}'s should test
5909 for features. The information about which configurations contain which
5910 features should be segregated into the configuration files. Experience
5911 has proven far too often that a feature unique to one particular system
5912 often creeps into other systems; and that a conditional based on some
5913 predefined macro for your current system will become worthless over
5914 time, as new versions of your system come out that behave differently
5915 with regard to this feature.
5917 Adding code that handles specific architectures, operating systems,
5918 target interfaces, or hosts, is not acceptable in generic code.
5920 @cindex portable file name handling
5921 @cindex file names, portability
5922 One particularly notorious area where system dependencies tend to
5923 creep in is handling of file names. The mainline @value{GDBN} code
5924 assumes Posix semantics of file names: absolute file names begin with
5925 a forward slash @file{/}, slashes are used to separate leading
5926 directories, case-sensitive file names. These assumptions are not
5927 necessarily true on non-Posix systems such as MS-Windows. To avoid
5928 system-dependent code where you need to take apart or construct a file
5929 name, use the following portable macros:
5932 @findex HAVE_DOS_BASED_FILE_SYSTEM
5933 @item HAVE_DOS_BASED_FILE_SYSTEM
5934 This preprocessing symbol is defined to a non-zero value on hosts
5935 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5936 symbol to write conditional code which should only be compiled for
5939 @findex IS_DIR_SEPARATOR
5940 @item IS_DIR_SEPARATOR (@var{c})
5941 Evaluates to a non-zero value if @var{c} is a directory separator
5942 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5943 such a character, but on Windows, both @file{/} and @file{\} will
5946 @findex IS_ABSOLUTE_PATH
5947 @item IS_ABSOLUTE_PATH (@var{file})
5948 Evaluates to a non-zero value if @var{file} is an absolute file name.
5949 For Unix and GNU/Linux hosts, a name which begins with a slash
5950 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5951 @file{x:\bar} are also absolute file names.
5953 @findex FILENAME_CMP
5954 @item FILENAME_CMP (@var{f1}, @var{f2})
5955 Calls a function which compares file names @var{f1} and @var{f2} as
5956 appropriate for the underlying host filesystem. For Posix systems,
5957 this simply calls @code{strcmp}; on case-insensitive filesystems it
5958 will call @code{strcasecmp} instead.
5960 @findex DIRNAME_SEPARATOR
5961 @item DIRNAME_SEPARATOR
5962 Evaluates to a character which separates directories in
5963 @code{PATH}-style lists, typically held in environment variables.
5964 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5966 @findex SLASH_STRING
5968 This evaluates to a constant string you should use to produce an
5969 absolute filename from leading directories and the file's basename.
5970 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5971 @code{"\\"} for some Windows-based ports.
5974 In addition to using these macros, be sure to use portable library
5975 functions whenever possible. For example, to extract a directory or a
5976 basename part from a file name, use the @code{dirname} and
5977 @code{basename} library functions (available in @code{libiberty} for
5978 platforms which don't provide them), instead of searching for a slash
5979 with @code{strrchr}.
5981 Another way to generalize @value{GDBN} along a particular interface is with an
5982 attribute struct. For example, @value{GDBN} has been generalized to handle
5983 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5984 by defining the @code{target_ops} structure and having a current target (as
5985 well as a stack of targets below it, for memory references). Whenever
5986 something needs to be done that depends on which remote interface we are
5987 using, a flag in the current target_ops structure is tested (e.g.,
5988 @code{target_has_stack}), or a function is called through a pointer in the
5989 current target_ops structure. In this way, when a new remote interface
5990 is added, only one module needs to be touched---the one that actually
5991 implements the new remote interface. Other examples of
5992 attribute-structs are BFD access to multiple kinds of object file
5993 formats, or @value{GDBN}'s access to multiple source languages.
5995 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5996 the code interfacing between @code{ptrace} and the rest of
5997 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5998 something was very painful. In @value{GDBN} 4.x, these have all been
5999 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
6000 with variations between systems the same way any system-independent
6001 file would (hooks, @code{#if defined}, etc.), and machines which are
6002 radically different don't need to use @file{infptrace.c} at all.
6004 All debugging code must be controllable using the @samp{set debug
6005 @var{module}} command. Do not use @code{printf} to print trace
6006 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
6007 @code{#ifdef DEBUG}.
6012 @chapter Porting @value{GDBN}
6013 @cindex porting to new machines
6015 Most of the work in making @value{GDBN} compile on a new machine is in
6016 specifying the configuration of the machine. This is done in a
6017 dizzying variety of header files and configuration scripts, which we
6018 hope to make more sensible soon. Let's say your new host is called an
6019 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
6020 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
6021 @samp{sparc-sun-sunos4}). In particular:
6025 In the top level directory, edit @file{config.sub} and add @var{arch},
6026 @var{xvend}, and @var{xos} to the lists of supported architectures,
6027 vendors, and operating systems near the bottom of the file. Also, add
6028 @var{xyz} as an alias that maps to
6029 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
6033 ./config.sub @var{xyz}
6040 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
6044 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
6045 and no error messages.
6048 You need to port BFD, if that hasn't been done already. Porting BFD is
6049 beyond the scope of this manual.
6052 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
6053 your system and set @code{gdb_host} to @var{xyz}, and (unless your
6054 desired target is already available) also edit @file{gdb/configure.tgt},
6055 setting @code{gdb_target} to something appropriate (for instance,
6058 @emph{Maintainer's note: Work in progress. The file
6059 @file{gdb/configure.host} originally needed to be modified when either a
6060 new native target or a new host machine was being added to @value{GDBN}.
6061 Recent changes have removed this requirement. The file now only needs
6062 to be modified when adding a new native configuration. This will likely
6063 changed again in the future.}
6066 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
6067 target-dependent @file{.h} and @file{.c} files used for your
6071 @node Versions and Branches
6072 @chapter Versions and Branches
6076 @value{GDBN}'s version is determined by the file
6077 @file{gdb/version.in} and takes one of the following forms:
6080 @item @var{major}.@var{minor}
6081 @itemx @var{major}.@var{minor}.@var{patchlevel}
6082 an official release (e.g., 6.2 or 6.2.1)
6083 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}
6084 a snapshot taken at @var{YYYY}-@var{MM}-@var{DD}-gmt (e.g.,
6085 6.1.50.20020302, 6.1.90.20020304, or 6.1.0.20020308)
6086 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD}-cvs
6087 a @sc{cvs} check out drawn on @var{YYYY}-@var{MM}-@var{DD} (e.g.,
6088 6.1.50.20020302-cvs, 6.1.90.20020304-cvs, or 6.1.0.20020308-cvs)
6089 @item @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD} (@var{vendor})
6090 a vendor specific release of @value{GDBN}, that while based on@*
6091 @var{major}.@var{minor}.@var{patchlevel}.@var{YYYY}@var{MM}@var{DD},
6092 may include additional changes
6095 @value{GDBN}'s mainline uses the @var{major} and @var{minor} version
6096 numbers from the most recent release branch, with a @var{patchlevel}
6097 of 50. At the time each new release branch is created, the mainline's
6098 @var{major} and @var{minor} version numbers are updated.
6100 @value{GDBN}'s release branch is similar. When the branch is cut, the
6101 @var{patchlevel} is changed from 50 to 90. As draft releases are
6102 drawn from the branch, the @var{patchlevel} is incremented. Once the
6103 first release (@var{major}.@var{minor}) has been made, the
6104 @var{patchlevel} is set to 0 and updates have an incremented
6107 For snapshots, and @sc{cvs} check outs, it is also possible to
6108 identify the @sc{cvs} origin:
6111 @item @var{major}.@var{minor}.50.@var{YYYY}@var{MM}@var{DD}
6112 drawn from the @sc{head} of mainline @sc{cvs} (e.g., 6.1.50.20020302)
6113 @item @var{major}.@var{minor}.90.@var{YYYY}@var{MM}@var{DD}
6114 @itemx @var{major}.@var{minor}.91.@var{YYYY}@var{MM}@var{DD} @dots{}
6115 drawn from a release branch prior to the release (e.g.,
6117 @item @var{major}.@var{minor}.0.@var{YYYY}@var{MM}@var{DD}
6118 @itemx @var{major}.@var{minor}.1.@var{YYYY}@var{MM}@var{DD} @dots{}
6119 drawn from a release branch after the release (e.g., 6.2.0.20020308)
6122 If the previous @value{GDBN} version is 6.1 and the current version is
6123 6.2, then, substituting 6 for @var{major} and 1 or 2 for @var{minor},
6124 here's an illustration of a typical sequence:
6131 +--------------------------.
6134 6.2.50.20020303-cvs 6.1.90 (draft #1)
6136 6.2.50.20020304-cvs 6.1.90.20020304-cvs
6138 6.2.50.20020305-cvs 6.1.91 (draft #2)
6140 6.2.50.20020306-cvs 6.1.91.20020306-cvs
6142 6.2.50.20020307-cvs 6.2 (release)
6144 6.2.50.20020308-cvs 6.2.0.20020308-cvs
6146 6.2.50.20020309-cvs 6.2.1 (update)
6148 6.2.50.20020310-cvs <branch closed>
6152 +--------------------------.
6155 6.3.50.20020312-cvs 6.2.90 (draft #1)
6159 @section Release Branches
6160 @cindex Release Branches
6162 @value{GDBN} draws a release series (6.2, 6.2.1, @dots{}) from a
6163 single release branch, and identifies that branch using the @sc{cvs}
6167 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-branchpoint
6168 gdb_@var{major}_@var{minor}-branch
6169 gdb_@var{major}_@var{minor}-@var{YYYY}@var{MM}@var{DD}-release
6172 @emph{Pragmatics: To help identify the date at which a branch or
6173 release is made, both the branchpoint and release tags include the
6174 date that they are cut (@var{YYYY}@var{MM}@var{DD}) in the tag. The
6175 branch tag, denoting the head of the branch, does not need this.}
6177 @section Vendor Branches
6178 @cindex vendor branches
6180 To avoid version conflicts, vendors are expected to modify the file
6181 @file{gdb/version.in} to include a vendor unique alphabetic identifier
6182 (an official @value{GDBN} release never uses alphabetic characters in
6183 its version identifier). E.g., @samp{6.2widgit2}, or @samp{6.2 (Widgit
6186 @section Experimental Branches
6187 @cindex experimental branches
6189 @subsection Guidelines
6191 @value{GDBN} permits the creation of branches, cut from the @sc{cvs}
6192 repository, for experimental development. Branches make it possible
6193 for developers to share preliminary work, and maintainers to examine
6194 significant new developments.
6196 The following are a set of guidelines for creating such branches:
6200 @item a branch has an owner
6201 The owner can set further policy for a branch, but may not change the
6202 ground rules. In particular, they can set a policy for commits (be it
6203 adding more reviewers or deciding who can commit).
6205 @item all commits are posted
6206 All changes committed to a branch shall also be posted to
6207 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} patches
6208 mailing list}. While commentary on such changes are encouraged, people
6209 should remember that the changes only apply to a branch.
6211 @item all commits are covered by an assignment
6212 This ensures that all changes belong to the Free Software Foundation,
6213 and avoids the possibility that the branch may become contaminated.
6215 @item a branch is focused
6216 A focused branch has a single objective or goal, and does not contain
6217 unnecessary or irrelevant changes. Cleanups, where identified, being
6218 be pushed into the mainline as soon as possible.
6220 @item a branch tracks mainline
6221 This keeps the level of divergence under control. It also keeps the
6222 pressure on developers to push cleanups and other stuff into the
6225 @item a branch shall contain the entire @value{GDBN} module
6226 The @value{GDBN} module @code{gdb} should be specified when creating a
6227 branch (branches of individual files should be avoided). @xref{Tags}.
6229 @item a branch shall be branded using @file{version.in}
6230 The file @file{gdb/version.in} shall be modified so that it identifies
6231 the branch @var{owner} and branch @var{name}, e.g.,
6232 @samp{6.2.50.20030303_owner_name} or @samp{6.2 (Owner Name)}.
6239 To simplify the identification of @value{GDBN} branches, the following
6240 branch tagging convention is strongly recommended:
6244 @item @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6245 @itemx @var{owner}_@var{name}-@var{YYYYMMDD}-branch
6246 The branch point and corresponding branch tag. @var{YYYYMMDD} is the
6247 date that the branch was created. A branch is created using the
6248 sequence: @anchor{experimental branch tags}
6250 cvs rtag @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint gdb
6251 cvs rtag -b -r @var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint \
6252 @var{owner}_@var{name}-@var{YYYYMMDD}-branch gdb
6255 @item @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6256 The tagged point, on the mainline, that was used when merging the branch
6257 on @var{yyyymmdd}. To merge in all changes since the branch was cut,
6258 use a command sequence like:
6260 cvs rtag @var{owner}_@var{name}-@var{yyyymmdd}-mergepoint gdb
6262 -j@var{owner}_@var{name}-@var{YYYYMMDD}-branchpoint
6263 -j@var{owner}_@var{name}-@var{yyyymmdd}-mergepoint
6266 Similar sequences can be used to just merge in changes since the last
6272 For further information on @sc{cvs}, see
6273 @uref{http://www.gnu.org/software/cvs/, Concurrent Versions System}.
6275 @node Start of New Year Procedure
6276 @chapter Start of New Year Procedure
6277 @cindex new year procedure
6279 At the start of each new year, the following actions should be performed:
6283 Rotate the ChangeLog file
6285 The current @file{ChangeLog} file should be renamed into
6286 @file{ChangeLog-YYYY} where YYYY is the year that has just passed.
6287 A new @file{ChangeLog} file should be created, and its contents should
6288 contain a reference to the previous ChangeLog. The following should
6289 also be preserved at the end of the new ChangeLog, in order to provide
6290 the appropriate settings when editing this file with Emacs:
6296 version-control: never
6301 Add an entry for the newly created ChangeLog file (@file{ChangeLog-YYYY})
6302 in @file{gdb/config/djgpp/fnchange.lst}.
6305 Update the copyright year in the startup message
6307 Update the copyright year in file @file{top.c}, function
6308 @code{print_gdb_version}.
6313 @chapter Releasing @value{GDBN}
6314 @cindex making a new release of gdb
6316 @section Branch Commit Policy
6318 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
6319 5.1 and 5.2 all used the below:
6323 The @file{gdb/MAINTAINERS} file still holds.
6325 Don't fix something on the branch unless/until it is also fixed in the
6326 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
6327 file is better than committing a hack.
6329 When considering a patch for the branch, suggested criteria include:
6330 Does it fix a build? Does it fix the sequence @kbd{break main; run}
6331 when debugging a static binary?
6333 The further a change is from the core of @value{GDBN}, the less likely
6334 the change will worry anyone (e.g., target specific code).
6336 Only post a proposal to change the core of @value{GDBN} after you've
6337 sent individual bribes to all the people listed in the
6338 @file{MAINTAINERS} file @t{;-)}
6341 @emph{Pragmatics: Provided updates are restricted to non-core
6342 functionality there is little chance that a broken change will be fatal.
6343 This means that changes such as adding a new architectures or (within
6344 reason) support for a new host are considered acceptable.}
6347 @section Obsoleting code
6349 Before anything else, poke the other developers (and around the source
6350 code) to see if there is anything that can be removed from @value{GDBN}
6351 (an old target, an unused file).
6353 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
6354 line. Doing this means that it is easy to identify something that has
6355 been obsoleted when greping through the sources.
6357 The process is done in stages --- this is mainly to ensure that the
6358 wider @value{GDBN} community has a reasonable opportunity to respond.
6359 Remember, everything on the Internet takes a week.
6363 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
6364 list} Creating a bug report to track the task's state, is also highly
6369 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
6370 Announcement mailing list}.
6374 Go through and edit all relevant files and lines so that they are
6375 prefixed with the word @code{OBSOLETE}.
6377 Wait until the next GDB version, containing this obsolete code, has been
6380 Remove the obsolete code.
6384 @emph{Maintainer note: While removing old code is regrettable it is
6385 hopefully better for @value{GDBN}'s long term development. Firstly it
6386 helps the developers by removing code that is either no longer relevant
6387 or simply wrong. Secondly since it removes any history associated with
6388 the file (effectively clearing the slate) the developer has a much freer
6389 hand when it comes to fixing broken files.}
6393 @section Before the Branch
6395 The most important objective at this stage is to find and fix simple
6396 changes that become a pain to track once the branch is created. For
6397 instance, configuration problems that stop @value{GDBN} from even
6398 building. If you can't get the problem fixed, document it in the
6399 @file{gdb/PROBLEMS} file.
6401 @subheading Prompt for @file{gdb/NEWS}
6403 People always forget. Send a post reminding them but also if you know
6404 something interesting happened add it yourself. The @code{schedule}
6405 script will mention this in its e-mail.
6407 @subheading Review @file{gdb/README}
6409 Grab one of the nightly snapshots and then walk through the
6410 @file{gdb/README} looking for anything that can be improved. The
6411 @code{schedule} script will mention this in its e-mail.
6413 @subheading Refresh any imported files.
6415 A number of files are taken from external repositories. They include:
6419 @file{texinfo/texinfo.tex}
6421 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
6424 @file{etc/standards.texi}, @file{etc/make-stds.texi}
6427 @subheading Check the ARI
6429 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
6430 (Awk Regression Index ;-) that checks for a number of errors and coding
6431 conventions. The checks include things like using @code{malloc} instead
6432 of @code{xmalloc} and file naming problems. There shouldn't be any
6435 @subsection Review the bug data base
6437 Close anything obviously fixed.
6439 @subsection Check all cross targets build
6441 The targets are listed in @file{gdb/MAINTAINERS}.
6444 @section Cut the Branch
6446 @subheading Create the branch
6451 $ V=`echo $v | sed 's/\./_/g'`
6452 $ D=`date -u +%Y-%m-%d`
6455 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6456 -D $D-gmt gdb_$V-$D-branchpoint insight
6457 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
6458 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight
6461 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6462 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight
6463 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
6464 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight
6472 By using @kbd{-D YYYY-MM-DD-gmt}, the branch is forced to an exact
6475 The trunk is first tagged so that the branch point can easily be found.
6477 Insight, which includes @value{GDBN}, is tagged at the same time.
6479 @file{version.in} gets bumped to avoid version number conflicts.
6481 The reading of @file{.cvsrc} is disabled using @file{-f}.
6484 @subheading Update @file{version.in}
6489 $ V=`echo $v | sed 's/\./_/g'`
6493 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
6494 -r gdb_$V-branch src/gdb/version.in
6495 cvs -f -d :ext:sources.redhat.com:/cvs/src co
6496 -r gdb_5_2-branch src/gdb/version.in
6498 U src/gdb/version.in
6500 $ echo $u.90-0000-00-00-cvs > version.in
6502 5.1.90-0000-00-00-cvs
6503 $ cvs -f commit version.in
6508 @file{0000-00-00} is used as a date to pump prime the version.in update
6511 @file{.90} and the previous branch version are used as fairly arbitrary
6512 initial branch version number.
6516 @subheading Update the web and news pages
6520 @subheading Tweak cron to track the new branch
6522 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
6523 This file needs to be updated so that:
6527 A daily timestamp is added to the file @file{version.in}.
6529 The new branch is included in the snapshot process.
6533 See the file @file{gdbadmin/cron/README} for how to install the updated
6536 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
6537 any changes. That file is copied to both the branch/ and current/
6538 snapshot directories.
6541 @subheading Update the NEWS and README files
6543 The @file{NEWS} file needs to be updated so that on the branch it refers
6544 to @emph{changes in the current release} while on the trunk it also
6545 refers to @emph{changes since the current release}.
6547 The @file{README} file needs to be updated so that it refers to the
6550 @subheading Post the branch info
6552 Send an announcement to the mailing lists:
6556 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6558 @email{gdb@@sources.redhat.com, GDB Discussion mailing list} and
6559 @email{gdb-testers@@sources.redhat.com, GDB Testers mailing list}
6562 @emph{Pragmatics: The branch creation is sent to the announce list to
6563 ensure that people people not subscribed to the higher volume discussion
6566 The announcement should include:
6572 How to check out the branch using CVS.
6574 The date/number of weeks until the release.
6576 The branch commit policy still holds.
6579 @section Stabilize the branch
6581 Something goes here.
6583 @section Create a Release
6585 The process of creating and then making available a release is broken
6586 down into a number of stages. The first part addresses the technical
6587 process of creating a releasable tar ball. The later stages address the
6588 process of releasing that tar ball.
6590 When making a release candidate just the first section is needed.
6592 @subsection Create a release candidate
6594 The objective at this stage is to create a set of tar balls that can be
6595 made available as a formal release (or as a less formal release
6598 @subsubheading Freeze the branch
6600 Send out an e-mail notifying everyone that the branch is frozen to
6601 @email{gdb-patches@@sources.redhat.com}.
6603 @subsubheading Establish a few defaults.
6608 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
6610 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6614 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
6616 /home/gdbadmin/bin/autoconf
6625 Check the @code{autoconf} version carefully. You want to be using the
6626 version taken from the @file{binutils} snapshot directory, which can be
6627 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
6628 unlikely that a system installed version of @code{autoconf} (e.g.,
6629 @file{/usr/bin/autoconf}) is correct.
6632 @subsubheading Check out the relevant modules:
6635 $ for m in gdb insight
6637 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
6647 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
6648 any confusion between what is written here and what your local
6649 @code{cvs} really does.
6652 @subsubheading Update relevant files.
6658 Major releases get their comments added as part of the mainline. Minor
6659 releases should probably mention any significant bugs that were fixed.
6661 Don't forget to include the @file{ChangeLog} entry.
6664 $ emacs gdb/src/gdb/NEWS
6669 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
6670 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6675 You'll need to update:
6687 $ emacs gdb/src/gdb/README
6692 $ cp gdb/src/gdb/README insight/src/gdb/README
6693 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6696 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
6697 before the initial branch was cut so just a simple substitute is needed
6700 @emph{Maintainer note: Other projects generate @file{README} and
6701 @file{INSTALL} from the core documentation. This might be worth
6704 @item gdb/version.in
6707 $ echo $v > gdb/src/gdb/version.in
6708 $ cat gdb/src/gdb/version.in
6710 $ emacs gdb/src/gdb/version.in
6713 ... Bump to version ...
6715 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
6716 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6721 @subsubheading Do the dirty work
6723 This is identical to the process used to create the daily snapshot.
6726 $ for m in gdb insight
6728 ( cd $m/src && gmake -f src-release $m.tar )
6732 If the top level source directory does not have @file{src-release}
6733 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
6736 $ for m in gdb insight
6738 ( cd $m/src && gmake -f Makefile.in $m.tar )
6742 @subsubheading Check the source files
6744 You're looking for files that have mysteriously disappeared.
6745 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
6746 for the @file{version.in} update @kbd{cronjob}.
6749 $ ( cd gdb/src && cvs -f -q -n update )
6753 @dots{} lots of generated files @dots{}
6758 @dots{} lots of generated files @dots{}
6763 @emph{Don't worry about the @file{gdb.info-??} or
6764 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
6765 was also generated only something strange with CVS means that they
6766 didn't get suppressed). Fixing it would be nice though.}
6768 @subsubheading Create compressed versions of the release
6774 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
6775 $ for m in gdb insight
6777 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
6778 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
6788 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
6789 in that mode, @code{gzip} does not know the name of the file and, hence,
6790 can not include it in the compressed file. This is also why the release
6791 process runs @code{tar} and @code{bzip2} as separate passes.
6794 @subsection Sanity check the tar ball
6796 Pick a popular machine (Solaris/PPC?) and try the build on that.
6799 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
6804 $ ./gdb/gdb ./gdb/gdb
6808 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6810 Starting program: /tmp/gdb-5.2/gdb/gdb
6812 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6813 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6815 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6819 @subsection Make a release candidate available
6821 If this is a release candidate then the only remaining steps are:
6825 Commit @file{version.in} and @file{ChangeLog}
6827 Tweak @file{version.in} (and @file{ChangeLog} to read
6828 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6829 process can restart.
6831 Make the release candidate available in
6832 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6834 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6835 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6838 @subsection Make a formal release available
6840 (And you thought all that was required was to post an e-mail.)
6842 @subsubheading Install on sware
6844 Copy the new files to both the release and the old release directory:
6847 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6848 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6852 Clean up the releases directory so that only the most recent releases
6853 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6856 $ cd ~ftp/pub/gdb/releases
6861 Update the file @file{README} and @file{.message} in the releases
6868 $ ln README .message
6871 @subsubheading Update the web pages.
6875 @item htdocs/download/ANNOUNCEMENT
6876 This file, which is posted as the official announcement, includes:
6879 General announcement.
6881 News. If making an @var{M}.@var{N}.1 release, retain the news from
6882 earlier @var{M}.@var{N} release.
6887 @item htdocs/index.html
6888 @itemx htdocs/news/index.html
6889 @itemx htdocs/download/index.html
6890 These files include:
6893 Announcement of the most recent release.
6895 News entry (remember to update both the top level and the news directory).
6897 These pages also need to be regenerate using @code{index.sh}.
6899 @item download/onlinedocs/
6900 You need to find the magic command that is used to generate the online
6901 docs from the @file{.tar.bz2}. The best way is to look in the output
6902 from one of the nightly @code{cron} jobs and then just edit accordingly.
6906 $ ~/ss/update-web-docs \
6907 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6909 /www/sourceware/htdocs/gdb/download/onlinedocs \
6914 Just like the online documentation. Something like:
6917 $ /bin/sh ~/ss/update-web-ari \
6918 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6920 /www/sourceware/htdocs/gdb/download/ari \
6926 @subsubheading Shadow the pages onto gnu
6928 Something goes here.
6931 @subsubheading Install the @value{GDBN} tar ball on GNU
6933 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6934 @file{~ftp/gnu/gdb}.
6936 @subsubheading Make the @file{ANNOUNCEMENT}
6938 Post the @file{ANNOUNCEMENT} file you created above to:
6942 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6944 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6945 day or so to let things get out)
6947 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6952 The release is out but you're still not finished.
6954 @subsubheading Commit outstanding changes
6956 In particular you'll need to commit any changes to:
6960 @file{gdb/ChangeLog}
6962 @file{gdb/version.in}
6969 @subsubheading Tag the release
6974 $ d=`date -u +%Y-%m-%d`
6977 $ ( cd insight/src/gdb && cvs -f -q update )
6978 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6981 Insight is used since that contains more of the release than
6984 @subsubheading Mention the release on the trunk
6986 Just put something in the @file{ChangeLog} so that the trunk also
6987 indicates when the release was made.
6989 @subsubheading Restart @file{gdb/version.in}
6991 If @file{gdb/version.in} does not contain an ISO date such as
6992 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6993 committed all the release changes it can be set to
6994 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6995 is important - it affects the snapshot process).
6997 Don't forget the @file{ChangeLog}.
6999 @subsubheading Merge into trunk
7001 The files committed to the branch may also need changes merged into the
7004 @subsubheading Revise the release schedule
7006 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
7007 Discussion List} with an updated announcement. The schedule can be
7008 generated by running:
7011 $ ~/ss/schedule `date +%s` schedule
7015 The first parameter is approximate date/time in seconds (from the epoch)
7016 of the most recent release.
7018 Also update the schedule @code{cronjob}.
7020 @section Post release
7022 Remove any @code{OBSOLETE} code.
7029 The testsuite is an important component of the @value{GDBN} package.
7030 While it is always worthwhile to encourage user testing, in practice
7031 this is rarely sufficient; users typically use only a small subset of
7032 the available commands, and it has proven all too common for a change
7033 to cause a significant regression that went unnoticed for some time.
7035 The @value{GDBN} testsuite uses the DejaGNU testing framework. The
7036 tests themselves are calls to various @code{Tcl} procs; the framework
7037 runs all the procs and summarizes the passes and fails.
7039 @section Using the Testsuite
7041 @cindex running the test suite
7042 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
7043 testsuite's objdir) and type @code{make check}. This just sets up some
7044 environment variables and invokes DejaGNU's @code{runtest} script. While
7045 the testsuite is running, you'll get mentions of which test file is in use,
7046 and a mention of any unexpected passes or fails. When the testsuite is
7047 finished, you'll get a summary that looks like this:
7052 # of expected passes 6016
7053 # of unexpected failures 58
7054 # of unexpected successes 5
7055 # of expected failures 183
7056 # of unresolved testcases 3
7057 # of untested testcases 5
7060 To run a specific test script, type:
7062 make check RUNTESTFLAGS='@var{tests}'
7064 where @var{tests} is a list of test script file names, separated by
7067 The ideal test run consists of expected passes only; however, reality
7068 conspires to keep us from this ideal. Unexpected failures indicate
7069 real problems, whether in @value{GDBN} or in the testsuite. Expected
7070 failures are still failures, but ones which have been decided are too
7071 hard to deal with at the time; for instance, a test case might work
7072 everywhere except on AIX, and there is no prospect of the AIX case
7073 being fixed in the near future. Expected failures should not be added
7074 lightly, since you may be masking serious bugs in @value{GDBN}.
7075 Unexpected successes are expected fails that are passing for some
7076 reason, while unresolved and untested cases often indicate some minor
7077 catastrophe, such as the compiler being unable to deal with a test
7080 When making any significant change to @value{GDBN}, you should run the
7081 testsuite before and after the change, to confirm that there are no
7082 regressions. Note that truly complete testing would require that you
7083 run the testsuite with all supported configurations and a variety of
7084 compilers; however this is more than really necessary. In many cases
7085 testing with a single configuration is sufficient. Other useful
7086 options are to test one big-endian (Sparc) and one little-endian (x86)
7087 host, a cross config with a builtin simulator (powerpc-eabi,
7088 mips-elf), or a 64-bit host (Alpha).
7090 If you add new functionality to @value{GDBN}, please consider adding
7091 tests for it as well; this way future @value{GDBN} hackers can detect
7092 and fix their changes that break the functionality you added.
7093 Similarly, if you fix a bug that was not previously reported as a test
7094 failure, please add a test case for it. Some cases are extremely
7095 difficult to test, such as code that handles host OS failures or bugs
7096 in particular versions of compilers, and it's OK not to try to write
7097 tests for all of those.
7099 DejaGNU supports separate build, host, and target machines. However,
7100 some @value{GDBN} test scripts do not work if the build machine and
7101 the host machine are not the same. In such an environment, these scripts
7102 will give a result of ``UNRESOLVED'', like this:
7105 UNRESOLVED: gdb.base/example.exp: This test script does not work on a remote host.
7108 @section Testsuite Organization
7110 @cindex test suite organization
7111 The testsuite is entirely contained in @file{gdb/testsuite}. While the
7112 testsuite includes some makefiles and configury, these are very minimal,
7113 and used for little besides cleaning up, since the tests themselves
7114 handle the compilation of the programs that @value{GDBN} will run. The file
7115 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
7116 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
7117 configuration-specific files, typically used for special-purpose
7118 definitions of procs like @code{gdb_load} and @code{gdb_start}.
7120 The tests themselves are to be found in @file{testsuite/gdb.*} and
7121 subdirectories of those. The names of the test files must always end
7122 with @file{.exp}. DejaGNU collects the test files by wildcarding
7123 in the test directories, so both subdirectories and individual files
7124 get chosen and run in alphabetical order.
7126 The following table lists the main types of subdirectories and what they
7127 are for. Since DejaGNU finds test files no matter where they are
7128 located, and since each test file sets up its own compilation and
7129 execution environment, this organization is simply for convenience and
7134 This is the base testsuite. The tests in it should apply to all
7135 configurations of @value{GDBN} (but generic native-only tests may live here).
7136 The test programs should be in the subset of C that is valid K&R,
7137 ANSI/ISO, and C@t{++} (@code{#ifdef}s are allowed if necessary, for instance
7140 @item gdb.@var{lang}
7141 Language-specific tests for any language @var{lang} besides C. Examples are
7142 @file{gdb.cp} and @file{gdb.java}.
7144 @item gdb.@var{platform}
7145 Non-portable tests. The tests are specific to a specific configuration
7146 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
7149 @item gdb.@var{compiler}
7150 Tests specific to a particular compiler. As of this writing (June
7151 1999), there aren't currently any groups of tests in this category that
7152 couldn't just as sensibly be made platform-specific, but one could
7153 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
7156 @item gdb.@var{subsystem}
7157 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
7158 instance, @file{gdb.disasm} exercises various disassemblers, while
7159 @file{gdb.stabs} tests pathways through the stabs symbol reader.
7162 @section Writing Tests
7163 @cindex writing tests
7165 In many areas, the @value{GDBN} tests are already quite comprehensive; you
7166 should be able to copy existing tests to handle new cases.
7168 You should try to use @code{gdb_test} whenever possible, since it
7169 includes cases to handle all the unexpected errors that might happen.
7170 However, it doesn't cost anything to add new test procedures; for
7171 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
7172 calls @code{gdb_test} multiple times.
7174 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
7175 necessary, such as when @value{GDBN} has several valid responses to a command.
7177 The source language programs do @emph{not} need to be in a consistent
7178 style. Since @value{GDBN} is used to debug programs written in many different
7179 styles, it's worth having a mix of styles in the testsuite; for
7180 instance, some @value{GDBN} bugs involving the display of source lines would
7181 never manifest themselves if the programs used GNU coding style
7188 Check the @file{README} file, it often has useful information that does not
7189 appear anywhere else in the directory.
7192 * Getting Started:: Getting started working on @value{GDBN}
7193 * Debugging GDB:: Debugging @value{GDBN} with itself
7196 @node Getting Started,,, Hints
7198 @section Getting Started
7200 @value{GDBN} is a large and complicated program, and if you first starting to
7201 work on it, it can be hard to know where to start. Fortunately, if you
7202 know how to go about it, there are ways to figure out what is going on.
7204 This manual, the @value{GDBN} Internals manual, has information which applies
7205 generally to many parts of @value{GDBN}.
7207 Information about particular functions or data structures are located in
7208 comments with those functions or data structures. If you run across a
7209 function or a global variable which does not have a comment correctly
7210 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
7211 free to submit a bug report, with a suggested comment if you can figure
7212 out what the comment should say. If you find a comment which is
7213 actually wrong, be especially sure to report that.
7215 Comments explaining the function of macros defined in host, target, or
7216 native dependent files can be in several places. Sometimes they are
7217 repeated every place the macro is defined. Sometimes they are where the
7218 macro is used. Sometimes there is a header file which supplies a
7219 default definition of the macro, and the comment is there. This manual
7220 also documents all the available macros.
7221 @c (@pxref{Host Conditionals}, @pxref{Target
7222 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
7225 Start with the header files. Once you have some idea of how
7226 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
7227 @file{gdbtypes.h}), you will find it much easier to understand the
7228 code which uses and creates those symbol tables.
7230 You may wish to process the information you are getting somehow, to
7231 enhance your understanding of it. Summarize it, translate it to another
7232 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
7233 the code to predict what a test case would do and write the test case
7234 and verify your prediction, etc. If you are reading code and your eyes
7235 are starting to glaze over, this is a sign you need to use a more active
7238 Once you have a part of @value{GDBN} to start with, you can find more
7239 specifically the part you are looking for by stepping through each
7240 function with the @code{next} command. Do not use @code{step} or you
7241 will quickly get distracted; when the function you are stepping through
7242 calls another function try only to get a big-picture understanding
7243 (perhaps using the comment at the beginning of the function being
7244 called) of what it does. This way you can identify which of the
7245 functions being called by the function you are stepping through is the
7246 one which you are interested in. You may need to examine the data
7247 structures generated at each stage, with reference to the comments in
7248 the header files explaining what the data structures are supposed to
7251 Of course, this same technique can be used if you are just reading the
7252 code, rather than actually stepping through it. The same general
7253 principle applies---when the code you are looking at calls something
7254 else, just try to understand generally what the code being called does,
7255 rather than worrying about all its details.
7257 @cindex command implementation
7258 A good place to start when tracking down some particular area is with
7259 a command which invokes that feature. Suppose you want to know how
7260 single-stepping works. As a @value{GDBN} user, you know that the
7261 @code{step} command invokes single-stepping. The command is invoked
7262 via command tables (see @file{command.h}); by convention the function
7263 which actually performs the command is formed by taking the name of
7264 the command and adding @samp{_command}, or in the case of an
7265 @code{info} subcommand, @samp{_info}. For example, the @code{step}
7266 command invokes the @code{step_command} function and the @code{info
7267 display} command invokes @code{display_info}. When this convention is
7268 not followed, you might have to use @code{grep} or @kbd{M-x
7269 tags-search} in emacs, or run @value{GDBN} on itself and set a
7270 breakpoint in @code{execute_command}.
7272 @cindex @code{bug-gdb} mailing list
7273 If all of the above fail, it may be appropriate to ask for information
7274 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
7275 wondering if anyone could give me some tips about understanding
7276 @value{GDBN}''---if we had some magic secret we would put it in this manual.
7277 Suggestions for improving the manual are always welcome, of course.
7279 @node Debugging GDB,,,Hints
7281 @section Debugging @value{GDBN} with itself
7282 @cindex debugging @value{GDBN}
7284 If @value{GDBN} is limping on your machine, this is the preferred way to get it
7285 fully functional. Be warned that in some ancient Unix systems, like
7286 Ultrix 4.2, a program can't be running in one process while it is being
7287 debugged in another. Rather than typing the command @kbd{@w{./gdb
7288 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
7289 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
7291 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
7292 @file{.gdbinit} file that sets up some simple things to make debugging
7293 gdb easier. The @code{info} command, when executed without a subcommand
7294 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
7295 gdb. See @file{.gdbinit} for details.
7297 If you use emacs, you will probably want to do a @code{make TAGS} after
7298 you configure your distribution; this will put the machine dependent
7299 routines for your local machine where they will be accessed first by
7302 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
7303 have run @code{fixincludes} if you are compiling with gcc.
7305 @section Submitting Patches
7307 @cindex submitting patches
7308 Thanks for thinking of offering your changes back to the community of
7309 @value{GDBN} users. In general we like to get well designed enhancements.
7310 Thanks also for checking in advance about the best way to transfer the
7313 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
7314 This manual summarizes what we believe to be clean design for @value{GDBN}.
7316 If the maintainers don't have time to put the patch in when it arrives,
7317 or if there is any question about a patch, it goes into a large queue
7318 with everyone else's patches and bug reports.
7320 @cindex legal papers for code contributions
7321 The legal issue is that to incorporate substantial changes requires a
7322 copyright assignment from you and/or your employer, granting ownership
7323 of the changes to the Free Software Foundation. You can get the
7324 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
7325 and asking for it. We recommend that people write in "All programs
7326 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
7327 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
7329 contributed with only one piece of legalese pushed through the
7330 bureaucracy and filed with the FSF. We can't start merging changes until
7331 this paperwork is received by the FSF (their rules, which we follow
7332 since we maintain it for them).
7334 Technically, the easiest way to receive changes is to receive each
7335 feature as a small context diff or unidiff, suitable for @code{patch}.
7336 Each message sent to me should include the changes to C code and
7337 header files for a single feature, plus @file{ChangeLog} entries for
7338 each directory where files were modified, and diffs for any changes
7339 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
7340 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
7341 single feature, they can be split down into multiple messages.
7343 In this way, if we read and like the feature, we can add it to the
7344 sources with a single patch command, do some testing, and check it in.
7345 If you leave out the @file{ChangeLog}, we have to write one. If you leave
7346 out the doc, we have to puzzle out what needs documenting. Etc., etc.
7348 The reason to send each change in a separate message is that we will not
7349 install some of the changes. They'll be returned to you with questions
7350 or comments. If we're doing our job correctly, the message back to you
7351 will say what you have to fix in order to make the change acceptable.
7352 The reason to have separate messages for separate features is so that
7353 the acceptable changes can be installed while one or more changes are
7354 being reworked. If multiple features are sent in a single message, we
7355 tend to not put in the effort to sort out the acceptable changes from
7356 the unacceptable, so none of the features get installed until all are
7359 If this sounds painful or authoritarian, well, it is. But we get a lot
7360 of bug reports and a lot of patches, and many of them don't get
7361 installed because we don't have the time to finish the job that the bug
7362 reporter or the contributor could have done. Patches that arrive
7363 complete, working, and well designed, tend to get installed on the day
7364 they arrive. The others go into a queue and get installed as time
7365 permits, which, since the maintainers have many demands to meet, may not
7366 be for quite some time.
7368 Please send patches directly to
7369 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
7371 @section Obsolete Conditionals
7372 @cindex obsolete code
7374 Fragments of old code in @value{GDBN} sometimes reference or set the following
7375 configuration macros. They should not be used by new code, and old uses
7376 should be removed as those parts of the debugger are otherwise touched.
7379 @item STACK_END_ADDR
7380 This macro used to define where the end of the stack appeared, for use
7381 in interpreting core file formats that don't record this address in the
7382 core file itself. This information is now configured in BFD, and @value{GDBN}
7383 gets the info portably from there. The values in @value{GDBN}'s configuration
7384 files should be moved into BFD configuration files (if needed there),
7385 and deleted from all of @value{GDBN}'s config files.
7387 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
7388 is so old that it has never been converted to use BFD. Now that's old!
7392 @include observer.texi