1 \input texinfo @c -*- texinfo -*-
2 @setfilename gdbint.info
4 @dircategory Programming & development tools.
6 * Gdb-Internals: (gdbint). The GNU debugger's internals.
10 This file documents the internals of the GNU debugger @value{GDBN}.
11 Copyright 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001,2002
12 Free Software Foundation, Inc.
13 Contributed by Cygnus Solutions. Written by John Gilmore.
14 Second Edition by Stan Shebs.
16 Permission is granted to copy, distribute and/or modify this document
17 under the terms of the GNU Free Documentation License, Version 1.1 or
18 any later version published by the Free Software Foundation; with no
19 Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
20 and with the Back-Cover Texts as in (a) below.
22 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
23 this GNU Manual, like GNU software. Copies published by the Free
24 Software Foundation raise funds for GNU development.''
27 @setchapternewpage off
28 @settitle @value{GDBN} Internals
34 @title @value{GDBN} Internals
35 @subtitle{A guide to the internals of the GNU debugger}
37 @author Cygnus Solutions
38 @author Second Edition:
40 @author Cygnus Solutions
43 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
44 \xdef\manvers{\$Revision$} % For use in headers, footers too
46 \hfill Cygnus Solutions\par
48 \hfill \TeX{}info \texinfoversion\par
52 @vskip 0pt plus 1filll
53 Copyright @copyright{} 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001
54 Free Software Foundation, Inc.
56 Permission is granted to copy, distribute and/or modify this document
57 under the terms of the GNU Free Documentation License, Version 1.1 or
58 any later version published by the Free Software Foundation; with no
59 Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
63 this GNU Manual, like GNU software. Copies published by the Free
64 Software Foundation raise funds for GNU development.''
70 @c Perhaps this should be the title of the document (but only for info,
71 @c not for TeX). Existing GNU manuals seem inconsistent on this point.
72 @top Scope of this Document
74 This document documents the internals of the GNU debugger, @value{GDBN}. It
75 includes description of @value{GDBN}'s key algorithms and operations, as well
76 as the mechanisms that adapt @value{GDBN} to specific hosts and targets.
87 * Target Architecture Definition::
88 * Target Vector Definition::
97 * GNU Free Documentation License:: The license for this documentation
103 @chapter Requirements
104 @cindex requirements for @value{GDBN}
106 Before diving into the internals, you should understand the formal
107 requirements and other expectations for @value{GDBN}. Although some
108 of these may seem obvious, there have been proposals for @value{GDBN}
109 that have run counter to these requirements.
111 First of all, @value{GDBN} is a debugger. It's not designed to be a
112 front panel for embedded systems. It's not a text editor. It's not a
113 shell. It's not a programming environment.
115 @value{GDBN} is an interactive tool. Although a batch mode is
116 available, @value{GDBN}'s primary role is to interact with a human
119 @value{GDBN} should be responsive to the user. A programmer hot on
120 the trail of a nasty bug, and operating under a looming deadline, is
121 going to be very impatient of everything, including the response time
122 to debugger commands.
124 @value{GDBN} should be relatively permissive, such as for expressions.
125 While the compiler should be picky (or have the option to be made
126 picky), since source code lives for a long time usually, the
127 programmer doing debugging shouldn't be spending time figuring out to
128 mollify the debugger.
130 @value{GDBN} will be called upon to deal with really large programs.
131 Executable sizes of 50 to 100 megabytes occur regularly, and we've
132 heard reports of programs approaching 1 gigabyte in size.
134 @value{GDBN} should be able to run everywhere. No other debugger is
135 available for even half as many configurations as @value{GDBN}
139 @node Overall Structure
141 @chapter Overall Structure
143 @value{GDBN} consists of three major subsystems: user interface,
144 symbol handling (the @dfn{symbol side}), and target system handling (the
147 The user interface consists of several actual interfaces, plus
150 The symbol side consists of object file readers, debugging info
151 interpreters, symbol table management, source language expression
152 parsing, type and value printing.
154 The target side consists of execution control, stack frame analysis, and
155 physical target manipulation.
157 The target side/symbol side division is not formal, and there are a
158 number of exceptions. For instance, core file support involves symbolic
159 elements (the basic core file reader is in BFD) and target elements (it
160 supplies the contents of memory and the values of registers). Instead,
161 this division is useful for understanding how the minor subsystems
164 @section The Symbol Side
166 The symbolic side of @value{GDBN} can be thought of as ``everything
167 you can do in @value{GDBN} without having a live program running''.
168 For instance, you can look at the types of variables, and evaluate
169 many kinds of expressions.
171 @section The Target Side
173 The target side of @value{GDBN} is the ``bits and bytes manipulator''.
174 Although it may make reference to symbolic info here and there, most
175 of the target side will run with only a stripped executable
176 available---or even no executable at all, in remote debugging cases.
178 Operations such as disassembly, stack frame crawls, and register
179 display, are able to work with no symbolic info at all. In some cases,
180 such as disassembly, @value{GDBN} will use symbolic info to present addresses
181 relative to symbols rather than as raw numbers, but it will work either
184 @section Configurations
188 @dfn{Host} refers to attributes of the system where @value{GDBN} runs.
189 @dfn{Target} refers to the system where the program being debugged
190 executes. In most cases they are the same machine, in which case a
191 third type of @dfn{Native} attributes come into play.
193 Defines and include files needed to build on the host are host support.
194 Examples are tty support, system defined types, host byte order, host
197 Defines and information needed to handle the target format are target
198 dependent. Examples are the stack frame format, instruction set,
199 breakpoint instruction, registers, and how to set up and tear down the stack
202 Information that is only needed when the host and target are the same,
203 is native dependent. One example is Unix child process support; if the
204 host and target are not the same, doing a fork to start the target
205 process is a bad idea. The various macros needed for finding the
206 registers in the @code{upage}, running @code{ptrace}, and such are all
207 in the native-dependent files.
209 Another example of native-dependent code is support for features that
210 are really part of the target environment, but which require
211 @code{#include} files that are only available on the host system. Core
212 file handling and @code{setjmp} handling are two common cases.
214 When you want to make @value{GDBN} work ``native'' on a particular machine, you
215 have to include all three kinds of information.
223 @value{GDBN} uses a number of debugging-specific algorithms. They are
224 often not very complicated, but get lost in the thicket of special
225 cases and real-world issues. This chapter describes the basic
226 algorithms and mentions some of the specific target definitions that
232 @cindex call stack frame
233 A frame is a construct that @value{GDBN} uses to keep track of calling
234 and called functions.
236 @findex create_new_frame
238 @code{FRAME_FP} in the machine description has no meaning to the
239 machine-independent part of @value{GDBN}, except that it is used when
240 setting up a new frame from scratch, as follows:
243 create_new_frame (read_register (FP_REGNUM), read_pc ()));
246 @cindex frame pointer register
247 Other than that, all the meaning imparted to @code{FP_REGNUM} is
248 imparted by the machine-dependent code. So, @code{FP_REGNUM} can have
249 any value that is convenient for the code that creates new frames.
250 (@code{create_new_frame} calls @code{INIT_EXTRA_FRAME_INFO} if it is
251 defined; that is where you should use the @code{FP_REGNUM} value, if
252 your frames are nonstandard.)
255 Given a @value{GDBN} frame, define @code{FRAME_CHAIN} to determine the
256 address of the calling function's frame. This will be used to create
257 a new @value{GDBN} frame struct, and then @code{INIT_EXTRA_FRAME_INFO}
258 and @code{INIT_FRAME_PC} will be called for the new frame.
260 @section Breakpoint Handling
263 In general, a breakpoint is a user-designated location in the program
264 where the user wants to regain control if program execution ever reaches
267 There are two main ways to implement breakpoints; either as ``hardware''
268 breakpoints or as ``software'' breakpoints.
270 @cindex hardware breakpoints
271 @cindex program counter
272 Hardware breakpoints are sometimes available as a builtin debugging
273 features with some chips. Typically these work by having dedicated
274 register into which the breakpoint address may be stored. If the PC
275 (shorthand for @dfn{program counter})
276 ever matches a value in a breakpoint registers, the CPU raises an
277 exception and reports it to @value{GDBN}.
279 Another possibility is when an emulator is in use; many emulators
280 include circuitry that watches the address lines coming out from the
281 processor, and force it to stop if the address matches a breakpoint's
284 A third possibility is that the target already has the ability to do
285 breakpoints somehow; for instance, a ROM monitor may do its own
286 software breakpoints. So although these are not literally ``hardware
287 breakpoints'', from @value{GDBN}'s point of view they work the same;
288 @value{GDBN} need not do nothing more than set the breakpoint and wait
289 for something to happen.
291 Since they depend on hardware resources, hardware breakpoints may be
292 limited in number; when the user asks for more, @value{GDBN} will
293 start trying to set software breakpoints. (On some architectures,
294 notably the 32-bit x86 platforms, @value{GDBN} cannot always know
295 whether there's enough hardware resources to insert all the hardware
296 breakpoints and watchpoints. On those platforms, @value{GDBN} prints
297 an error message only when the program being debugged is continued.)
299 @cindex software breakpoints
300 Software breakpoints require @value{GDBN} to do somewhat more work.
301 The basic theory is that @value{GDBN} will replace a program
302 instruction with a trap, illegal divide, or some other instruction
303 that will cause an exception, and then when it's encountered,
304 @value{GDBN} will take the exception and stop the program. When the
305 user says to continue, @value{GDBN} will restore the original
306 instruction, single-step, re-insert the trap, and continue on.
308 Since it literally overwrites the program being tested, the program area
309 must be writable, so this technique won't work on programs in ROM. It
310 can also distort the behavior of programs that examine themselves,
311 although such a situation would be highly unusual.
313 Also, the software breakpoint instruction should be the smallest size of
314 instruction, so it doesn't overwrite an instruction that might be a jump
315 target, and cause disaster when the program jumps into the middle of the
316 breakpoint instruction. (Strictly speaking, the breakpoint must be no
317 larger than the smallest interval between instructions that may be jump
318 targets; perhaps there is an architecture where only even-numbered
319 instructions may jumped to.) Note that it's possible for an instruction
320 set not to have any instructions usable for a software breakpoint,
321 although in practice only the ARC has failed to define such an
325 The basic definition of the software breakpoint is the macro
328 Basic breakpoint object handling is in @file{breakpoint.c}. However,
329 much of the interesting breakpoint action is in @file{infrun.c}.
331 @section Single Stepping
333 @section Signal Handling
335 @section Thread Handling
337 @section Inferior Function Calls
339 @section Longjmp Support
341 @cindex @code{longjmp} debugging
342 @value{GDBN} has support for figuring out that the target is doing a
343 @code{longjmp} and for stopping at the target of the jump, if we are
344 stepping. This is done with a few specialized internal breakpoints,
345 which are visible in the output of the @samp{maint info breakpoint}
348 @findex GET_LONGJMP_TARGET
349 To make this work, you need to define a macro called
350 @code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
351 structure and extract the longjmp target address. Since @code{jmp_buf}
352 is target specific, you will need to define it in the appropriate
353 @file{tm-@var{target}.h} file. Look in @file{tm-sun4os4.h} and
354 @file{sparc-tdep.c} for examples of how to do this.
359 Watchpoints are a special kind of breakpoints (@pxref{Algorithms,
360 breakpoints}) which break when data is accessed rather than when some
361 instruction is executed. When you have data which changes without
362 your knowing what code does that, watchpoints are the silver bullet to
363 hunt down and kill such bugs.
365 @cindex hardware watchpoints
366 @cindex software watchpoints
367 Watchpoints can be either hardware-assisted or not; the latter type is
368 known as ``software watchpoints.'' @value{GDBN} always uses
369 hardware-assisted watchpoints if they are available, and falls back on
370 software watchpoints otherwise. Typical situations where @value{GDBN}
371 will use software watchpoints are:
375 The watched memory region is too large for the underlying hardware
376 watchpoint support. For example, each x86 debug register can watch up
377 to 4 bytes of memory, so trying to watch data structures whose size is
378 more than 16 bytes will cause @value{GDBN} to use software
382 The value of the expression to be watched depends on data held in
383 registers (as opposed to memory).
386 Too many different watchpoints requested. (On some architectures,
387 this situation is impossible to detect until the debugged program is
388 resumed.) Note that x86 debug registers are used both for hardware
389 breakpoints and for watchpoints, so setting too many hardware
390 breakpoints might cause watchpoint insertion to fail.
393 No hardware-assisted watchpoints provided by the target
397 Software watchpoints are very slow, since @value{GDBN} needs to
398 single-step the program being debugged and test the value of the
399 watched expression(s) after each instruction. The rest of this
400 section is mostly irrelevant for software watchpoints.
402 @value{GDBN} uses several macros and primitives to support hardware
406 @findex TARGET_HAS_HARDWARE_WATCHPOINTS
407 @item TARGET_HAS_HARDWARE_WATCHPOINTS
408 If defined, the target supports hardware watchpoints.
410 @findex TARGET_CAN_USE_HARDWARE_WATCHPOINT
411 @item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other})
412 Return the number of hardware watchpoints of type @var{type} that are
413 possible to be set. The value is positive if @var{count} watchpoints
414 of this type can be set, zero if setting watchpoints of this type is
415 not supported, and negative if @var{count} is more than the maximum
416 number of watchpoints of type @var{type} that can be set. @var{other}
417 is non-zero if other types of watchpoints are currently enabled (there
418 are architectures which cannot set watchpoints of different types at
421 @findex TARGET_REGION_OK_FOR_HW_WATCHPOINT
422 @item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len})
423 Return non-zero if hardware watchpoints can be used to watch a region
424 whose address is @var{addr} and whose length in bytes is @var{len}.
426 @findex TARGET_REGION_SIZE_OK_FOR_HW_WATCHPOINT
427 @item TARGET_REGION_SIZE_OK_FOR_HW_WATCHPOINT (@var{size})
428 Return non-zero if hardware watchpoints can be used to watch a region
429 whose size is @var{size}. @value{GDBN} only uses this macro as a
430 fall-back, in case @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is not
433 @findex TARGET_DISABLE_HW_WATCHPOINTS
434 @item TARGET_DISABLE_HW_WATCHPOINTS (@var{pid})
435 Disables watchpoints in the process identified by @var{pid}. This is
436 used, e.g., on HP-UX which provides operations to disable and enable
437 the page-level memory protection that implements hardware watchpoints
440 @findex TARGET_ENABLE_HW_WATCHPOINTS
441 @item TARGET_ENABLE_HW_WATCHPOINTS (@var{pid})
442 Enables watchpoints in the process identified by @var{pid}. This is
443 used, e.g., on HP-UX which provides operations to disable and enable
444 the page-level memory protection that implements hardware watchpoints
447 @findex target_insert_watchpoint
448 @findex target_remove_watchpoint
449 @item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
450 @itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type})
451 Insert or remove a hardware watchpoint starting at @var{addr}, for
452 @var{len} bytes. @var{type} is the watchpoint type, one of the
453 possible values of the enumerated data type @code{target_hw_bp_type},
454 defined by @file{breakpoint.h} as follows:
457 enum target_hw_bp_type
459 hw_write = 0, /* Common (write) HW watchpoint */
460 hw_read = 1, /* Read HW watchpoint */
461 hw_access = 2, /* Access (read or write) HW watchpoint */
462 hw_execute = 3 /* Execute HW breakpoint */
467 These two macros should return 0 for success, non-zero for failure.
469 @cindex insert or remove hardware breakpoint
470 @findex target_remove_hw_breakpoint
471 @findex target_insert_hw_breakpoint
472 @item target_remove_hw_breakpoint (@var{addr}, @var{shadow})
473 @itemx target_insert_hw_breakpoint (@var{addr}, @var{shadow})
474 Insert or remove a hardware-assisted breakpoint at address @var{addr}.
475 Returns zero for success, non-zero for failure. @var{shadow} is the
476 real contents of the byte where the breakpoint has been inserted; it
477 is generally not valid when hardware breakpoints are used, but since
478 no other code touches these values, the implementations of the above
479 two macros can use them for their internal purposes.
481 @findex target_stopped_data_address
482 @item target_stopped_data_address ()
483 If the inferior has some watchpoint that triggered, return the address
484 associated with that watchpoint. Otherwise, return zero.
486 @findex DECR_PC_AFTER_HW_BREAK
487 @item DECR_PC_AFTER_HW_BREAK
488 If defined, @value{GDBN} decrements the program counter by the value
489 of @code{DECR_PC_AFTER_HW_BREAK} after a hardware break-point. This
490 overrides the value of @code{DECR_PC_AFTER_BREAK} when a breakpoint
491 that breaks is a hardware-assisted breakpoint.
493 @findex HAVE_STEPPABLE_WATCHPOINT
494 @item HAVE_STEPPABLE_WATCHPOINT
495 If defined to a non-zero value, it is not necessary to disable a
496 watchpoint to step over it.
498 @findex HAVE_NONSTEPPABLE_WATCHPOINT
499 @item HAVE_NONSTEPPABLE_WATCHPOINT
500 If defined to a non-zero value, @value{GDBN} should disable a
501 watchpoint to step the inferior over it.
503 @findex HAVE_CONTINUABLE_WATCHPOINT
504 @item HAVE_CONTINUABLE_WATCHPOINT
505 If defined to a non-zero value, it is possible to continue the
506 inferior after a watchpoint has been hit.
508 @findex CANNOT_STEP_HW_WATCHPOINTS
509 @item CANNOT_STEP_HW_WATCHPOINTS
510 If this is defined to a non-zero value, @value{GDBN} will remove all
511 watchpoints before stepping the inferior.
513 @findex STOPPED_BY_WATCHPOINT
514 @item STOPPED_BY_WATCHPOINT (@var{wait_status})
515 Return non-zero if stopped by a watchpoint. @var{wait_status} is of
516 the type @code{struct target_waitstatus}, defined by @file{target.h}.
519 @subsection x86 Watchpoints
520 @cindex x86 debug registers
521 @cindex watchpoints, on x86
523 The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug
524 registers designed to facilitate debugging. @value{GDBN} provides a
525 generic library of functions that x86-based ports can use to implement
526 support for watchpoints and hardware-assisted breakpoints. This
527 subsection documents the x86 watchpoint facilities in @value{GDBN}.
529 To use the generic x86 watchpoint support, a port should do the
533 @findex I386_USE_GENERIC_WATCHPOINTS
535 Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the
536 target-dependent headers.
539 Include the @file{config/i386/nm-i386.h} header file @emph{after}
540 defining @code{I386_USE_GENERIC_WATCHPOINTS}.
543 Add @file{i386-nat.o} to the value of the Make variable
544 @code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}) or
545 @code{TDEPFILES} (@pxref{Target Architecture Definition, TDEPFILES}).
548 Provide implementations for the @code{I386_DR_LOW_*} macros described
549 below. Typically, each macro should call a target-specific function
550 which does the real work.
553 The x86 watchpoint support works by maintaining mirror images of the
554 debug registers. Values are copied between the mirror images and the
555 real debug registers via a set of macros which each target needs to
559 @findex I386_DR_LOW_SET_CONTROL
560 @item I386_DR_LOW_SET_CONTROL (@var{val})
561 Set the Debug Control (DR7) register to the value @var{val}.
563 @findex I386_DR_LOW_SET_ADDR
564 @item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr})
565 Put the address @var{addr} into the debug register number @var{idx}.
567 @findex I386_DR_LOW_RESET_ADDR
568 @item I386_DR_LOW_RESET_ADDR (@var{idx})
569 Reset (i.e.@: zero out) the address stored in the debug register
572 @findex I386_DR_LOW_GET_STATUS
573 @item I386_DR_LOW_GET_STATUS
574 Return the value of the Debug Status (DR6) register. This value is
575 used immediately after it is returned by
576 @code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status
580 For each one of the 4 debug registers (whose indices are from 0 to 3)
581 that store addresses, a reference count is maintained by @value{GDBN},
582 to allow sharing of debug registers by several watchpoints. This
583 allows users to define several watchpoints that watch the same
584 expression, but with different conditions and/or commands, without
585 wasting debug registers which are in short supply. @value{GDBN}
586 maintains the reference counts internally, targets don't have to do
587 anything to use this feature.
589 The x86 debug registers can each watch a region that is 1, 2, or 4
590 bytes long. The ia32 architecture requires that each watched region
591 be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte
592 region on 4-byte boundary. However, the x86 watchpoint support in
593 @value{GDBN} can watch unaligned regions and regions larger than 4
594 bytes (up to 16 bytes) by allocating several debug registers to watch
595 a single region. This allocation of several registers per a watched
596 region is also done automatically without target code intervention.
598 The generic x86 watchpoint support provides the following API for the
599 @value{GDBN}'s application code:
602 @findex i386_region_ok_for_watchpoint
603 @item i386_region_ok_for_watchpoint (@var{addr}, @var{len})
604 The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call
605 this function. It counts the number of debug registers required to
606 watch a given region, and returns a non-zero value if that number is
607 less than 4, the number of debug registers available to x86
610 @findex i386_stopped_data_address
611 @item i386_stopped_data_address (void)
612 The macros @code{STOPPED_BY_WATCHPOINT} and
613 @code{target_stopped_data_address} are set to call this function. The
614 argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This
615 function examines the breakpoint condition bits in the DR6 Debug
616 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
617 macro, and returns the address associated with the first bit that is
620 @findex i386_insert_watchpoint
621 @findex i386_remove_watchpoint
622 @item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type})
623 @itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type})
624 Insert or remove a watchpoint. The macros
625 @code{target_insert_watchpoint} and @code{target_remove_watchpoint}
626 are set to call these functions. @code{i386_insert_watchpoint} first
627 looks for a debug register which is already set to watch the same
628 region for the same access types; if found, it just increments the
629 reference count of that debug register, thus implementing debug
630 register sharing between watchpoints. If no such register is found,
631 the function looks for a vacant debug register, sets its mirrored
632 value to @var{addr}, sets the mirrored value of DR7 Debug Control
633 register as appropriate for the @var{len} and @var{type} parameters,
634 and then passes the new values of the debug register and DR7 to the
635 inferior by calling @code{I386_DR_LOW_SET_ADDR} and
636 @code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is
637 required to cover the given region, the above process is repeated for
640 @code{i386_remove_watchpoint} does the opposite: it resets the address
641 in the mirrored value of the debug register and its read/write and
642 length bits in the mirrored value of DR7, then passes these new
643 values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and
644 @code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several
645 watchpoints, each time a @code{i386_remove_watchpoint} is called, it
646 decrements the reference count, and only calls
647 @code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when
648 the count goes to zero.
650 @findex i386_insert_hw_breakpoint
651 @findex i386_remove_hw_breakpoint
652 @item i386_insert_hw_breakpoint (@var{addr}, @var{shadow}
653 @itemx i386_remove_hw_breakpoint (@var{addr}, @var{shadow})
654 These functions insert and remove hardware-assisted breakpoints. The
655 macros @code{target_insert_hw_breakpoint} and
656 @code{target_remove_hw_breakpoint} are set to call these functions.
657 These functions work like @code{i386_insert_watchpoint} and
658 @code{i386_remove_watchpoint}, respectively, except that they set up
659 the debug registers to watch instruction execution, and each
660 hardware-assisted breakpoint always requires exactly one debug
663 @findex i386_stopped_by_hwbp
664 @item i386_stopped_by_hwbp (void)
665 This function returns non-zero if the inferior has some watchpoint or
666 hardware breakpoint that triggered. It works like
667 @code{i386_stopped_data_address}, except that it doesn't return the
668 address whose watchpoint triggered.
670 @findex i386_cleanup_dregs
671 @item i386_cleanup_dregs (void)
672 This function clears all the reference counts, addresses, and control
673 bits in the mirror images of the debug registers. It doesn't affect
674 the actual debug registers in the inferior process.
681 x86 processors support setting watchpoints on I/O reads or writes.
682 However, since no target supports this (as of March 2001), and since
683 @code{enum target_hw_bp_type} doesn't even have an enumeration for I/O
684 watchpoints, this feature is not yet available to @value{GDBN} running
688 x86 processors can enable watchpoints locally, for the current task
689 only, or globally, for all the tasks. For each debug register,
690 there's a bit in the DR7 Debug Control register that determines
691 whether the associated address is watched locally or globally. The
692 current implementation of x86 watchpoint support in @value{GDBN}
693 always sets watchpoints to be locally enabled, since global
694 watchpoints might interfere with the underlying OS and are probably
695 unavailable in many platforms.
700 @chapter User Interface
702 @value{GDBN} has several user interfaces. Although the command-line interface
703 is the most common and most familiar, there are others.
705 @section Command Interpreter
707 @cindex command interpreter
709 The command interpreter in @value{GDBN} is fairly simple. It is designed to
710 allow for the set of commands to be augmented dynamically, and also
711 has a recursive subcommand capability, where the first argument to
712 a command may itself direct a lookup on a different command list.
714 For instance, the @samp{set} command just starts a lookup on the
715 @code{setlist} command list, while @samp{set thread} recurses
716 to the @code{set_thread_cmd_list}.
720 To add commands in general, use @code{add_cmd}. @code{add_com} adds to
721 the main command list, and should be used for those commands. The usual
722 place to add commands is in the @code{_initialize_@var{xyz}} routines at
723 the ends of most source files.
725 @cindex deprecating commands
726 @findex deprecate_cmd
727 Before removing commands from the command set it is a good idea to
728 deprecate them for some time. Use @code{deprecate_cmd} on commands or
729 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
730 @code{struct cmd_list_element} as it's first argument. You can use the
731 return value from @code{add_com} or @code{add_cmd} to deprecate the
732 command immediately after it is created.
734 The first time a command is used the user will be warned and offered a
735 replacement (if one exists). Note that the replacement string passed to
736 @code{deprecate_cmd} should be the full name of the command, i.e. the
737 entire string the user should type at the command line.
739 @section UI-Independent Output---the @code{ui_out} Functions
740 @c This section is based on the documentation written by Fernando
741 @c Nasser <fnasser@redhat.com>.
743 @cindex @code{ui_out} functions
744 The @code{ui_out} functions present an abstraction level for the
745 @value{GDBN} output code. They hide the specifics of different user
746 interfaces supported by @value{GDBN}, and thus free the programmer
747 from the need to write several versions of the same code, one each for
748 every UI, to produce output.
750 @subsection Overview and Terminology
752 In general, execution of each @value{GDBN} command produces some sort
753 of output, and can even generate an input request.
755 Output can be generated for the following purposes:
759 to display a @emph{result} of an operation;
762 to convey @emph{info} or produce side-effects of a requested
766 to provide a @emph{notification} of an asynchronous event (including
767 progress indication of a prolonged asynchronous operation);
770 to display @emph{error messages} (including warnings);
773 to show @emph{debug data};
776 to @emph{query} or prompt a user for input (a special case).
780 This section mainly concentrates on how to build result output,
781 although some of it also applies to other kinds of output.
783 Generation of output that displays the results of an operation
784 involves one or more of the following:
788 output of the actual data
791 formatting the output as appropriate for console output, to make it
792 easily readable by humans
795 machine oriented formatting--a more terse formatting to allow for easy
796 parsing by programs which read @value{GDBN}'s output
799 annotation, whose purpose is to help legacy GUIs to identify interesting
803 The @code{ui_out} routines take care of the first three aspects.
804 Annotations are provided by separate annotation routines. Note that use
805 of annotations for an interface between a GUI and @value{GDBN} is
808 Output can be in the form of a single item, which we call a @dfn{field};
809 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
810 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
811 header and a body. In a BNF-like form:
814 @item <table> @expansion{}
815 @code{<header> <body>}
816 @item <header> @expansion{}
817 @code{@{ <column> @}}
818 @item <column> @expansion{}
819 @code{<width> <alignment> <title>}
820 @item <body> @expansion{}
825 @subsection General Conventions
827 Most @code{ui_out} routines are of type @code{void}, the exceptions are
828 @code{ui_out_stream_new} (which returns a pointer to the newly created
829 object) and the @code{make_cleanup} routines.
831 The first parameter is always the @code{ui_out} vector object, a pointer
832 to a @code{struct ui_out}.
834 The @var{format} parameter is like in @code{printf} family of functions.
835 When it is present, there must also be a variable list of arguments
836 sufficient used to satisfy the @code{%} specifiers in the supplied
839 When a character string argument is not used in a @code{ui_out} function
840 call, a @code{NULL} pointer has to be supplied instead.
843 @subsection Table, Tuple and List Functions
845 @cindex list output functions
846 @cindex table output functions
847 @cindex tuple output functions
848 This section introduces @code{ui_out} routines for building lists,
849 tuples and tables. The routines to output the actual data items
850 (fields) are presented in the next section.
852 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
853 containing information about an object; a @dfn{list} is a sequence of
854 fields where each field describes an identical object.
856 Use the @dfn{table} functions when your output consists of a list of
857 rows (tuples) and the console output should include a heading. Use this
858 even when you are listing just one object but you still want the header.
860 @cindex nesting level in @code{ui_out} functions
861 Tables can not be nested. Tuples and lists can be nested up to a
862 maximum of five levels.
864 The overall structure of the table output code is something like this:
879 Here is the description of table-, tuple- and list-related @code{ui_out}
882 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
883 The function @code{ui_out_table_begin} marks the beginning of the output
884 of a table. It should always be called before any other @code{ui_out}
885 function for a given table. @var{nbrofcols} is the number of columns in
886 the table. @var{nr_rows} is the number of rows in the table.
887 @var{tblid} is an optional string identifying the table. The string
888 pointed to by @var{tblid} is copied by the implementation of
889 @code{ui_out_table_begin}, so the application can free the string if it
892 The companion function @code{ui_out_table_end}, described below, marks
893 the end of the table's output.
896 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
897 @code{ui_out_table_header} provides the header information for a single
898 table column. You call this function several times, one each for every
899 column of the table, after @code{ui_out_table_begin}, but before
900 @code{ui_out_table_body}.
902 The value of @var{width} gives the column width in characters. The
903 value of @var{alignment} is one of @code{left}, @code{center}, and
904 @code{right}, and it specifies how to align the header: left-justify,
905 center, or right-justify it. @var{colhdr} points to a string that
906 specifies the column header; the implementation copies that string, so
907 column header strings in @code{malloc}ed storage can be freed after the
911 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
912 This function delimits the table header from the table body.
915 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
916 This function signals the end of a table's output. It should be called
917 after the table body has been produced by the list and field output
920 There should be exactly one call to @code{ui_out_table_end} for each
921 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
922 will signal an internal error.
925 The output of the tuples that represent the table rows must follow the
926 call to @code{ui_out_table_body} and precede the call to
927 @code{ui_out_table_end}. You build a tuple by calling
928 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
929 calls to functions which actually output fields between them.
931 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
932 This function marks the beginning of a tuple output. @var{id} points
933 to an optional string that identifies the tuple; it is copied by the
934 implementation, and so strings in @code{malloc}ed storage can be freed
938 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
939 This function signals an end of a tuple output. There should be exactly
940 one call to @code{ui_out_tuple_end} for each call to
941 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
945 @deftypefun struct cleanup *make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
946 This function first opens the tuple and then establishes a cleanup
947 (@pxref{Coding, Cleanups}) to close the tuple. It provides a convenient
948 and correct implementation of the non-portable@footnote{The function
949 cast is not portable ISO-C.} code sequence:
951 struct cleanup *old_cleanup;
952 ui_out_tuple_begin (uiout, "...");
953 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
958 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
959 This function marks the beginning of a list output. @var{id} points to
960 an optional string that identifies the list; it is copied by the
961 implementation, and so strings in @code{malloc}ed storage can be freed
965 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
966 This function signals an end of a list output. There should be exactly
967 one call to @code{ui_out_list_end} for each call to
968 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
972 @deftypefun struct cleanup *make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
973 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
974 opens a list and then establishes cleanup (@pxref{Coding, Cleanups})
975 that will close the list.list.
978 @subsection Item Output Functions
980 @cindex item output functions
981 @cindex field output functions
983 The functions described below produce output for the actual data
984 items, or fields, which contain information about the object.
986 Choose the appropriate function accordingly to your particular needs.
988 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
989 This is the most general output function. It produces the
990 representation of the data in the variable-length argument list
991 according to formatting specifications in @var{format}, a
992 @code{printf}-like format string. The optional argument @var{fldname}
993 supplies the name of the field. The data items themselves are
994 supplied as additional arguments after @var{format}.
996 This generic function should be used only when it is not possible to
997 use one of the specialized versions (see below).
1000 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1001 This function outputs a value of an @code{int} variable. It uses the
1002 @code{"%d"} output conversion specification. @var{fldname} specifies
1003 the name of the field.
1006 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, CORE_ADDR @var{address})
1007 This function outputs an address.
1010 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1011 This function outputs a string using the @code{"%s"} conversion
1015 Sometimes, there's a need to compose your output piece by piece using
1016 functions that operate on a stream, such as @code{value_print} or
1017 @code{fprintf_symbol_filtered}. These functions accept an argument of
1018 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1019 used to store the data stream used for the output. When you use one
1020 of these functions, you need a way to pass their results stored in a
1021 @code{ui_file} object to the @code{ui_out} functions. To this end,
1022 you first create a @code{ui_stream} object by calling
1023 @code{ui_out_stream_new}, pass the @code{stream} member of that
1024 @code{ui_stream} object to @code{value_print} and similar functions,
1025 and finally call @code{ui_out_field_stream} to output the field you
1026 constructed. When the @code{ui_stream} object is no longer needed,
1027 you should destroy it and free its memory by calling
1028 @code{ui_out_stream_delete}.
1030 @deftypefun struct ui_stream *ui_out_stream_new (struct ui_out *@var{uiout})
1031 This function creates a new @code{ui_stream} object which uses the
1032 same output methods as the @code{ui_out} object whose pointer is
1033 passed in @var{uiout}. It returns a pointer to the newly created
1034 @code{ui_stream} object.
1037 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1038 This functions destroys a @code{ui_stream} object specified by
1042 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1043 This function consumes all the data accumulated in
1044 @code{streambuf->stream} and outputs it like
1045 @code{ui_out_field_string} does. After a call to
1046 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1047 the stream is still valid and may be used for producing more fields.
1050 @strong{Important:} If there is any chance that your code could bail
1051 out before completing output generation and reaching the point where
1052 @code{ui_out_stream_delete} is called, it is necessary to set up a
1053 cleanup, to avoid leaking memory and other resources. Here's a
1054 skeleton code to do that:
1057 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1058 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1063 If the function already has the old cleanup chain set (for other kinds
1064 of cleanups), you just have to add your cleanup to it:
1067 mybuf = ui_out_stream_new (uiout);
1068 make_cleanup (ui_out_stream_delete, mybuf);
1071 Note that with cleanups in place, you should not call
1072 @code{ui_out_stream_delete} directly, or you would attempt to free the
1075 @subsection Utility Output Functions
1077 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1078 This function skips a field in a table. Use it if you have to leave
1079 an empty field without disrupting the table alignment. The argument
1080 @var{fldname} specifies a name for the (missing) filed.
1083 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1084 This function outputs the text in @var{string} in a way that makes it
1085 easy to be read by humans. For example, the console implementation of
1086 this method filters the text through a built-in pager, to prevent it
1087 from scrolling off the visible portion of the screen.
1089 Use this function for printing relatively long chunks of text around
1090 the actual field data: the text it produces is not aligned according
1091 to the table's format. Use @code{ui_out_field_string} to output a
1092 string field, and use @code{ui_out_message}, described below, to
1093 output short messages.
1096 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1097 This function outputs @var{nspaces} spaces. It is handy to align the
1098 text produced by @code{ui_out_text} with the rest of the table or
1102 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1103 This function produces a formatted message, provided that the current
1104 verbosity level is at least as large as given by @var{verbosity}. The
1105 current verbosity level is specified by the user with the @samp{set
1106 verbositylevel} command.@footnote{As of this writing (April 2001),
1107 setting verbosity level is not yet implemented, and is always returned
1108 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1109 argument more than zero will cause the message to never be printed.}
1112 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1113 This function gives the console output filter (a paging filter) a hint
1114 of where to break lines which are too long. Ignored for all other
1115 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1116 be printed to indent the wrapped text on the next line; it must remain
1117 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1118 explicit newline is produced by one of the other functions. If
1119 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1122 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1123 This function flushes whatever output has been accumulated so far, if
1124 the UI buffers output.
1128 @subsection Examples of Use of @code{ui_out} functions
1130 @cindex using @code{ui_out} functions
1131 @cindex @code{ui_out} functions, usage examples
1132 This section gives some practical examples of using the @code{ui_out}
1133 functions to generalize the old console-oriented code in
1134 @value{GDBN}. The examples all come from functions defined on the
1135 @file{breakpoints.c} file.
1137 This example, from the @code{breakpoint_1} function, shows how to
1140 The original code was:
1143 if (!found_a_breakpoint++)
1145 annotate_breakpoints_headers ();
1148 printf_filtered ("Num ");
1150 printf_filtered ("Type ");
1152 printf_filtered ("Disp ");
1154 printf_filtered ("Enb ");
1158 printf_filtered ("Address ");
1161 printf_filtered ("What\n");
1163 annotate_breakpoints_table ();
1167 Here's the new version:
1170 nr_printable_breakpoints = @dots{};
1173 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1175 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1177 if (nr_printable_breakpoints > 0)
1178 annotate_breakpoints_headers ();
1179 if (nr_printable_breakpoints > 0)
1181 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1182 if (nr_printable_breakpoints > 0)
1184 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1185 if (nr_printable_breakpoints > 0)
1187 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1188 if (nr_printable_breakpoints > 0)
1190 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1193 if (nr_printable_breakpoints > 0)
1195 if (TARGET_ADDR_BIT <= 32)
1196 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1198 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1200 if (nr_printable_breakpoints > 0)
1202 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1203 ui_out_table_body (uiout);
1204 if (nr_printable_breakpoints > 0)
1205 annotate_breakpoints_table ();
1208 This example, from the @code{print_one_breakpoint} function, shows how
1209 to produce the actual data for the table whose structure was defined
1210 in the above example. The original code was:
1215 printf_filtered ("%-3d ", b->number);
1217 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1218 || ((int) b->type != bptypes[(int) b->type].type))
1219 internal_error ("bptypes table does not describe type #%d.",
1221 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1223 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1225 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1229 This is the new version:
1233 ui_out_tuple_begin (uiout, "bkpt");
1235 ui_out_field_int (uiout, "number", b->number);
1237 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1238 || ((int) b->type != bptypes[(int) b->type].type))
1239 internal_error ("bptypes table does not describe type #%d.",
1241 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1243 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1245 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1249 This example, also from @code{print_one_breakpoint}, shows how to
1250 produce a complicated output field using the @code{print_expression}
1251 functions which requires a stream to be passed. It also shows how to
1252 automate stream destruction with cleanups. The original code was:
1256 print_expression (b->exp, gdb_stdout);
1262 struct ui_stream *stb = ui_out_stream_new (uiout);
1263 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1266 print_expression (b->exp, stb->stream);
1267 ui_out_field_stream (uiout, "what", local_stream);
1270 This example, also from @code{print_one_breakpoint}, shows how to use
1271 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1276 if (b->dll_pathname == NULL)
1277 printf_filtered ("<any library> ");
1279 printf_filtered ("library \"%s\" ", b->dll_pathname);
1286 if (b->dll_pathname == NULL)
1288 ui_out_field_string (uiout, "what", "<any library>");
1289 ui_out_spaces (uiout, 1);
1293 ui_out_text (uiout, "library \"");
1294 ui_out_field_string (uiout, "what", b->dll_pathname);
1295 ui_out_text (uiout, "\" ");
1299 The following example from @code{print_one_breakpoint} shows how to
1300 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1305 if (b->forked_inferior_pid != 0)
1306 printf_filtered ("process %d ", b->forked_inferior_pid);
1313 if (b->forked_inferior_pid != 0)
1315 ui_out_text (uiout, "process ");
1316 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1317 ui_out_spaces (uiout, 1);
1321 Here's an example of using @code{ui_out_field_string}. The original
1326 if (b->exec_pathname != NULL)
1327 printf_filtered ("program \"%s\" ", b->exec_pathname);
1334 if (b->exec_pathname != NULL)
1336 ui_out_text (uiout, "program \"");
1337 ui_out_field_string (uiout, "what", b->exec_pathname);
1338 ui_out_text (uiout, "\" ");
1342 Finally, here's an example of printing an address. The original code:
1346 printf_filtered ("%s ",
1347 local_hex_string_custom ((unsigned long) b->address, "08l"));
1354 ui_out_field_core_addr (uiout, "Address", b->address);
1358 @section Console Printing
1367 @cindex @code{libgdb}
1368 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1369 to provide an API to @value{GDBN}'s functionality.
1372 @cindex @code{libgdb}
1373 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1374 better able to support graphical and other environments.
1376 Since @code{libgdb} development is on-going, its architecture is still
1377 evolving. The following components have so far been identified:
1381 Observer - @file{gdb-events.h}.
1383 Builder - @file{ui-out.h}
1385 Event Loop - @file{event-loop.h}
1387 Library - @file{gdb.h}
1390 The model that ties these components together is described below.
1392 @section The @code{libgdb} Model
1394 A client of @code{libgdb} interacts with the library in two ways.
1398 As an observer (using @file{gdb-events}) receiving notifications from
1399 @code{libgdb} of any internal state changes (break point changes, run
1402 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1403 obtain various status values from @value{GDBN}.
1406 Since @code{libgdb} could have multiple clients (e.g. a GUI supporting
1407 the existing @value{GDBN} CLI), those clients must co-operate when
1408 controlling @code{libgdb}. In particular, a client must ensure that
1409 @code{libgdb} is idle (i.e. no other client is using @code{libgdb})
1410 before responding to a @file{gdb-event} by making a query.
1412 @section CLI support
1414 At present @value{GDBN}'s CLI is very much entangled in with the core of
1415 @code{libgdb}. Consequently, a client wishing to include the CLI in
1416 their interface needs to carefully co-ordinate its own and the CLI's
1419 It is suggested that the client set @code{libgdb} up to be bi-modal
1420 (alternate between CLI and client query modes). The notes below sketch
1425 The client registers itself as an observer of @code{libgdb}.
1427 The client create and install @code{cli-out} builder using its own
1428 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1429 @code{gdb_stdout} streams.
1431 The client creates a separate custom @code{ui-out} builder that is only
1432 used while making direct queries to @code{libgdb}.
1435 When the client receives input intended for the CLI, it simply passes it
1436 along. Since the @code{cli-out} builder is installed by default, all
1437 the CLI output in response to that command is routed (pronounced rooted)
1438 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1439 At the same time, the client is kept abreast of internal changes by
1440 virtue of being a @code{libgdb} observer.
1442 The only restriction on the client is that it must wait until
1443 @code{libgdb} becomes idle before initiating any queries (using the
1444 client's custom builder).
1446 @section @code{libgdb} components
1448 @subheading Observer - @file{gdb-events.h}
1449 @file{gdb-events} provides the client with a very raw mechanism that can
1450 be used to implement an observer. At present it only allows for one
1451 observer and that observer must, internally, handle the need to delay
1452 the processing of any event notifications until after @code{libgdb} has
1453 finished the current command.
1455 @subheading Builder - @file{ui-out.h}
1456 @file{ui-out} provides the infrastructure necessary for a client to
1457 create a builder. That builder is then passed down to @code{libgdb}
1458 when doing any queries.
1460 @subheading Event Loop - @file{event-loop.h}
1461 @c There could be an entire section on the event-loop
1462 @file{event-loop}, currently non-re-entrant, provides a simple event
1463 loop. A client would need to either plug its self into this loop or,
1464 implement a new event-loop that GDB would use.
1466 The event-loop will eventually be made re-entrant. This is so that
1467 @value{GDB} can better handle the problem of some commands blocking
1468 instead of returning.
1470 @subheading Library - @file{gdb.h}
1471 @file{libgdb} is the most obvious component of this system. It provides
1472 the query interface. Each function is parameterized by a @code{ui-out}
1473 builder. The result of the query is constructed using that builder
1474 before the query function returns.
1476 @node Symbol Handling
1478 @chapter Symbol Handling
1480 Symbols are a key part of @value{GDBN}'s operation. Symbols include variables,
1481 functions, and types.
1483 @section Symbol Reading
1485 @cindex symbol reading
1486 @cindex reading of symbols
1487 @cindex symbol files
1488 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
1489 file is the file containing the program which @value{GDBN} is
1490 debugging. @value{GDBN} can be directed to use a different file for
1491 symbols (with the @samp{symbol-file} command), and it can also read
1492 more symbols via the @samp{add-file} and @samp{load} commands, or while
1493 reading symbols from shared libraries.
1495 @findex find_sym_fns
1496 Symbol files are initially opened by code in @file{symfile.c} using
1497 the BFD library (@pxref{Support Libraries}). BFD identifies the type
1498 of the file by examining its header. @code{find_sym_fns} then uses
1499 this identification to locate a set of symbol-reading functions.
1501 @findex add_symtab_fns
1502 @cindex @code{sym_fns} structure
1503 @cindex adding a symbol-reading module
1504 Symbol-reading modules identify themselves to @value{GDBN} by calling
1505 @code{add_symtab_fns} during their module initialization. The argument
1506 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
1507 name (or name prefix) of the symbol format, the length of the prefix,
1508 and pointers to four functions. These functions are called at various
1509 times to process symbol files whose identification matches the specified
1512 The functions supplied by each module are:
1515 @item @var{xyz}_symfile_init(struct sym_fns *sf)
1517 @cindex secondary symbol file
1518 Called from @code{symbol_file_add} when we are about to read a new
1519 symbol file. This function should clean up any internal state (possibly
1520 resulting from half-read previous files, for example) and prepare to
1521 read a new symbol file. Note that the symbol file which we are reading
1522 might be a new ``main'' symbol file, or might be a secondary symbol file
1523 whose symbols are being added to the existing symbol table.
1525 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
1526 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
1527 new symbol file being read. Its @code{private} field has been zeroed,
1528 and can be modified as desired. Typically, a struct of private
1529 information will be @code{malloc}'d, and a pointer to it will be placed
1530 in the @code{private} field.
1532 There is no result from @code{@var{xyz}_symfile_init}, but it can call
1533 @code{error} if it detects an unavoidable problem.
1535 @item @var{xyz}_new_init()
1537 Called from @code{symbol_file_add} when discarding existing symbols.
1538 This function needs only handle the symbol-reading module's internal
1539 state; the symbol table data structures visible to the rest of
1540 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
1541 arguments and no result. It may be called after
1542 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
1543 may be called alone if all symbols are simply being discarded.
1545 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
1547 Called from @code{symbol_file_add} to actually read the symbols from a
1548 symbol-file into a set of psymtabs or symtabs.
1550 @code{sf} points to the @code{struct sym_fns} originally passed to
1551 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
1552 the offset between the file's specified start address and its true
1553 address in memory. @code{mainline} is 1 if this is the main symbol
1554 table being read, and 0 if a secondary symbol file (e.g. shared library
1555 or dynamically loaded file) is being read.@refill
1558 In addition, if a symbol-reading module creates psymtabs when
1559 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
1560 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
1561 from any point in the @value{GDBN} symbol-handling code.
1564 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
1566 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
1567 the psymtab has not already been read in and had its @code{pst->symtab}
1568 pointer set. The argument is the psymtab to be fleshed-out into a
1569 symtab. Upon return, @code{pst->readin} should have been set to 1, and
1570 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
1571 zero if there were no symbols in that part of the symbol file.
1574 @section Partial Symbol Tables
1576 @value{GDBN} has three types of symbol tables:
1579 @cindex full symbol table
1582 Full symbol tables (@dfn{symtabs}). These contain the main
1583 information about symbols and addresses.
1587 Partial symbol tables (@dfn{psymtabs}). These contain enough
1588 information to know when to read the corresponding part of the full
1591 @cindex minimal symbol table
1594 Minimal symbol tables (@dfn{msymtabs}). These contain information
1595 gleaned from non-debugging symbols.
1598 @cindex partial symbol table
1599 This section describes partial symbol tables.
1601 A psymtab is constructed by doing a very quick pass over an executable
1602 file's debugging information. Small amounts of information are
1603 extracted---enough to identify which parts of the symbol table will
1604 need to be re-read and fully digested later, when the user needs the
1605 information. The speed of this pass causes @value{GDBN} to start up very
1606 quickly. Later, as the detailed rereading occurs, it occurs in small
1607 pieces, at various times, and the delay therefrom is mostly invisible to
1609 @c (@xref{Symbol Reading}.)
1611 The symbols that show up in a file's psymtab should be, roughly, those
1612 visible to the debugger's user when the program is not running code from
1613 that file. These include external symbols and types, static symbols and
1614 types, and @code{enum} values declared at file scope.
1616 The psymtab also contains the range of instruction addresses that the
1617 full symbol table would represent.
1619 @cindex finding a symbol
1620 @cindex symbol lookup
1621 The idea is that there are only two ways for the user (or much of the
1622 code in the debugger) to reference a symbol:
1625 @findex find_pc_function
1626 @findex find_pc_line
1628 By its address (e.g. execution stops at some address which is inside a
1629 function in this file). The address will be noticed to be in the
1630 range of this psymtab, and the full symtab will be read in.
1631 @code{find_pc_function}, @code{find_pc_line}, and other
1632 @code{find_pc_@dots{}} functions handle this.
1634 @cindex lookup_symbol
1637 (e.g. the user asks to print a variable, or set a breakpoint on a
1638 function). Global names and file-scope names will be found in the
1639 psymtab, which will cause the symtab to be pulled in. Local names will
1640 have to be qualified by a global name, or a file-scope name, in which
1641 case we will have already read in the symtab as we evaluated the
1642 qualifier. Or, a local symbol can be referenced when we are ``in'' a
1643 local scope, in which case the first case applies. @code{lookup_symbol}
1644 does most of the work here.
1647 The only reason that psymtabs exist is to cause a symtab to be read in
1648 at the right moment. Any symbol that can be elided from a psymtab,
1649 while still causing that to happen, should not appear in it. Since
1650 psymtabs don't have the idea of scope, you can't put local symbols in
1651 them anyway. Psymtabs don't have the idea of the type of a symbol,
1652 either, so types need not appear, unless they will be referenced by
1655 It is a bug for @value{GDBN} to behave one way when only a psymtab has
1656 been read, and another way if the corresponding symtab has been read
1657 in. Such bugs are typically caused by a psymtab that does not contain
1658 all the visible symbols, or which has the wrong instruction address
1661 The psymtab for a particular section of a symbol file (objfile) could be
1662 thrown away after the symtab has been read in. The symtab should always
1663 be searched before the psymtab, so the psymtab will never be used (in a
1664 bug-free environment). Currently, psymtabs are allocated on an obstack,
1665 and all the psymbols themselves are allocated in a pair of large arrays
1666 on an obstack, so there is little to be gained by trying to free them
1667 unless you want to do a lot more work.
1671 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
1673 @cindex fundamental types
1674 These are the fundamental types that @value{GDBN} uses internally. Fundamental
1675 types from the various debugging formats (stabs, ELF, etc) are mapped
1676 into one of these. They are basically a union of all fundamental types
1677 that @value{GDBN} knows about for all the languages that @value{GDBN}
1680 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
1683 Each time @value{GDBN} builds an internal type, it marks it with one
1684 of these types. The type may be a fundamental type, such as
1685 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
1686 which is a pointer to another type. Typically, several @code{FT_*}
1687 types map to one @code{TYPE_CODE_*} type, and are distinguished by
1688 other members of the type struct, such as whether the type is signed
1689 or unsigned, and how many bits it uses.
1691 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
1693 These are instances of type structs that roughly correspond to
1694 fundamental types and are created as global types for @value{GDBN} to
1695 use for various ugly historical reasons. We eventually want to
1696 eliminate these. Note for example that @code{builtin_type_int}
1697 initialized in @file{gdbtypes.c} is basically the same as a
1698 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
1699 an @code{FT_INTEGER} fundamental type. The difference is that the
1700 @code{builtin_type} is not associated with any particular objfile, and
1701 only one instance exists, while @file{c-lang.c} builds as many
1702 @code{TYPE_CODE_INT} types as needed, with each one associated with
1703 some particular objfile.
1705 @section Object File Formats
1706 @cindex object file formats
1710 @cindex @code{a.out} format
1711 The @code{a.out} format is the original file format for Unix. It
1712 consists of three sections: @code{text}, @code{data}, and @code{bss},
1713 which are for program code, initialized data, and uninitialized data,
1716 The @code{a.out} format is so simple that it doesn't have any reserved
1717 place for debugging information. (Hey, the original Unix hackers used
1718 @samp{adb}, which is a machine-language debugger!) The only debugging
1719 format for @code{a.out} is stabs, which is encoded as a set of normal
1720 symbols with distinctive attributes.
1722 The basic @code{a.out} reader is in @file{dbxread.c}.
1727 The COFF format was introduced with System V Release 3 (SVR3) Unix.
1728 COFF files may have multiple sections, each prefixed by a header. The
1729 number of sections is limited.
1731 The COFF specification includes support for debugging. Although this
1732 was a step forward, the debugging information was woefully limited. For
1733 instance, it was not possible to represent code that came from an
1736 The COFF reader is in @file{coffread.c}.
1740 @cindex ECOFF format
1741 ECOFF is an extended COFF originally introduced for Mips and Alpha
1744 The basic ECOFF reader is in @file{mipsread.c}.
1748 @cindex XCOFF format
1749 The IBM RS/6000 running AIX uses an object file format called XCOFF.
1750 The COFF sections, symbols, and line numbers are used, but debugging
1751 symbols are @code{dbx}-style stabs whose strings are located in the
1752 @code{.debug} section (rather than the string table). For more
1753 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
1755 The shared library scheme has a clean interface for figuring out what
1756 shared libraries are in use, but the catch is that everything which
1757 refers to addresses (symbol tables and breakpoints at least) needs to be
1758 relocated for both shared libraries and the main executable. At least
1759 using the standard mechanism this can only be done once the program has
1760 been run (or the core file has been read).
1764 @cindex PE-COFF format
1765 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
1766 executables. PE is basically COFF with additional headers.
1768 While BFD includes special PE support, @value{GDBN} needs only the basic
1774 The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
1775 to COFF in being organized into a number of sections, but it removes
1776 many of COFF's limitations.
1778 The basic ELF reader is in @file{elfread.c}.
1783 SOM is HP's object file and debug format (not to be confused with IBM's
1784 SOM, which is a cross-language ABI).
1786 The SOM reader is in @file{hpread.c}.
1788 @subsection Other File Formats
1790 @cindex Netware Loadable Module format
1791 Other file formats that have been supported by @value{GDBN} include Netware
1792 Loadable Modules (@file{nlmread.c}).
1794 @section Debugging File Formats
1796 This section describes characteristics of debugging information that
1797 are independent of the object file format.
1801 @cindex stabs debugging info
1802 @code{stabs} started out as special symbols within the @code{a.out}
1803 format. Since then, it has been encapsulated into other file
1804 formats, such as COFF and ELF.
1806 While @file{dbxread.c} does some of the basic stab processing,
1807 including for encapsulated versions, @file{stabsread.c} does
1812 @cindex COFF debugging info
1813 The basic COFF definition includes debugging information. The level
1814 of support is minimal and non-extensible, and is not often used.
1816 @subsection Mips debug (Third Eye)
1818 @cindex ECOFF debugging info
1819 ECOFF includes a definition of a special debug format.
1821 The file @file{mdebugread.c} implements reading for this format.
1825 @cindex DWARF 1 debugging info
1826 DWARF 1 is a debugging format that was originally designed to be
1827 used with ELF in SVR4 systems.
1833 @c If defined, these are the producer strings in a DWARF 1 file. All of
1834 @c these have reasonable defaults already.
1836 The DWARF 1 reader is in @file{dwarfread.c}.
1840 @cindex DWARF 2 debugging info
1841 DWARF 2 is an improved but incompatible version of DWARF 1.
1843 The DWARF 2 reader is in @file{dwarf2read.c}.
1847 @cindex SOM debugging info
1848 Like COFF, the SOM definition includes debugging information.
1850 @section Adding a New Symbol Reader to @value{GDBN}
1852 @cindex adding debugging info reader
1853 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
1854 there is probably little to be done.
1856 If you need to add a new object file format, you must first add it to
1857 BFD. This is beyond the scope of this document.
1859 You must then arrange for the BFD code to provide access to the
1860 debugging symbols. Generally @value{GDBN} will have to call swapping routines
1861 from BFD and a few other BFD internal routines to locate the debugging
1862 information. As much as possible, @value{GDBN} should not depend on the BFD
1863 internal data structures.
1865 For some targets (e.g., COFF), there is a special transfer vector used
1866 to call swapping routines, since the external data structures on various
1867 platforms have different sizes and layouts. Specialized routines that
1868 will only ever be implemented by one object file format may be called
1869 directly. This interface should be described in a file
1870 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
1873 @node Language Support
1875 @chapter Language Support
1877 @cindex language support
1878 @value{GDBN}'s language support is mainly driven by the symbol reader,
1879 although it is possible for the user to set the source language
1882 @value{GDBN} chooses the source language by looking at the extension
1883 of the file recorded in the debug info; @file{.c} means C, @file{.f}
1884 means Fortran, etc. It may also use a special-purpose language
1885 identifier if the debug format supports it, like with DWARF.
1887 @section Adding a Source Language to @value{GDBN}
1889 @cindex adding source language
1890 To add other languages to @value{GDBN}'s expression parser, follow the
1894 @item Create the expression parser.
1896 @cindex expression parser
1897 This should reside in a file @file{@var{lang}-exp.y}. Routines for
1898 building parsed expressions into a @code{union exp_element} list are in
1901 @cindex language parser
1902 Since we can't depend upon everyone having Bison, and YACC produces
1903 parsers that define a bunch of global names, the following lines
1904 @strong{must} be included at the top of the YACC parser, to prevent the
1905 various parsers from defining the same global names:
1908 #define yyparse @var{lang}_parse
1909 #define yylex @var{lang}_lex
1910 #define yyerror @var{lang}_error
1911 #define yylval @var{lang}_lval
1912 #define yychar @var{lang}_char
1913 #define yydebug @var{lang}_debug
1914 #define yypact @var{lang}_pact
1915 #define yyr1 @var{lang}_r1
1916 #define yyr2 @var{lang}_r2
1917 #define yydef @var{lang}_def
1918 #define yychk @var{lang}_chk
1919 #define yypgo @var{lang}_pgo
1920 #define yyact @var{lang}_act
1921 #define yyexca @var{lang}_exca
1922 #define yyerrflag @var{lang}_errflag
1923 #define yynerrs @var{lang}_nerrs
1926 At the bottom of your parser, define a @code{struct language_defn} and
1927 initialize it with the right values for your language. Define an
1928 @code{initialize_@var{lang}} routine and have it call
1929 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
1930 that your language exists. You'll need some other supporting variables
1931 and functions, which will be used via pointers from your
1932 @code{@var{lang}_language_defn}. See the declaration of @code{struct
1933 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
1934 for more information.
1936 @item Add any evaluation routines, if necessary
1938 @cindex expression evaluation routines
1939 @findex evaluate_subexp
1940 @findex prefixify_subexp
1941 @findex length_of_subexp
1942 If you need new opcodes (that represent the operations of the language),
1943 add them to the enumerated type in @file{expression.h}. Add support
1944 code for these operations in the @code{evaluate_subexp} function
1945 defined in the file @file{eval.c}. Add cases
1946 for new opcodes in two functions from @file{parse.c}:
1947 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
1948 the number of @code{exp_element}s that a given operation takes up.
1950 @item Update some existing code
1952 Add an enumerated identifier for your language to the enumerated type
1953 @code{enum language} in @file{defs.h}.
1955 Update the routines in @file{language.c} so your language is included.
1956 These routines include type predicates and such, which (in some cases)
1957 are language dependent. If your language does not appear in the switch
1958 statement, an error is reported.
1960 @vindex current_language
1961 Also included in @file{language.c} is the code that updates the variable
1962 @code{current_language}, and the routines that translate the
1963 @code{language_@var{lang}} enumerated identifier into a printable
1966 @findex _initialize_language
1967 Update the function @code{_initialize_language} to include your
1968 language. This function picks the default language upon startup, so is
1969 dependent upon which languages that @value{GDBN} is built for.
1971 @findex allocate_symtab
1972 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
1973 code so that the language of each symtab (source file) is set properly.
1974 This is used to determine the language to use at each stack frame level.
1975 Currently, the language is set based upon the extension of the source
1976 file. If the language can be better inferred from the symbol
1977 information, please set the language of the symtab in the symbol-reading
1980 @findex print_subexp
1981 @findex op_print_tab
1982 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
1983 expression opcodes you have added to @file{expression.h}. Also, add the
1984 printed representations of your operators to @code{op_print_tab}.
1986 @item Add a place of call
1989 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
1990 @code{parse_exp_1} (defined in @file{parse.c}).
1992 @item Use macros to trim code
1994 @cindex trimming language-dependent code
1995 The user has the option of building @value{GDBN} for some or all of the
1996 languages. If the user decides to build @value{GDBN} for the language
1997 @var{lang}, then every file dependent on @file{language.h} will have the
1998 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
1999 leave out large routines that the user won't need if he or she is not
2000 using your language.
2002 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2003 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2004 compiled form of your parser) is not linked into @value{GDBN} at all.
2006 See the file @file{configure.in} for how @value{GDBN} is configured
2007 for different languages.
2009 @item Edit @file{Makefile.in}
2011 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2012 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2013 not get linked in, or, worse yet, it may not get @code{tar}red into the
2018 @node Host Definition
2020 @chapter Host Definition
2022 With the advent of Autoconf, it's rarely necessary to have host
2023 definition machinery anymore. The following information is provided,
2024 mainly, as an historical reference.
2026 @section Adding a New Host
2028 @cindex adding a new host
2029 @cindex host, adding
2030 @value{GDBN}'s host configuration support normally happens via Autoconf.
2031 New host-specific definitions should not be needed. Older hosts
2032 @value{GDBN} still use the host-specific definitions and files listed
2033 below, but these mostly exist for historical reasons, and will
2034 eventually disappear.
2037 @item gdb/config/@var{arch}/@var{xyz}.mh
2038 This file once contained both host and native configuration information
2039 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2040 configuration information is now handed by Autoconf.
2042 Host configuration information included a definition of
2043 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2044 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2045 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2047 New host only configurations do not need this file.
2049 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2050 This file once contained definitions and includes required when hosting
2051 gdb on machine @var{xyz}. Those definitions and includes are now
2052 handled by Autoconf.
2054 New host and native configurations do not need this file.
2056 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2057 file to define the macros @var{HOST_FLOAT_FORMAT},
2058 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2059 also needs to be replaced with either an Autoconf or run-time test.}
2063 @subheading Generic Host Support Files
2065 @cindex generic host support
2066 There are some ``generic'' versions of routines that can be used by
2067 various systems. These can be customized in various ways by macros
2068 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2069 the @var{xyz} host, you can just include the generic file's name (with
2070 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2072 Otherwise, if your machine needs custom support routines, you will need
2073 to write routines that perform the same functions as the generic file.
2074 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2075 into @code{XDEPFILES}.
2078 @cindex remote debugging support
2079 @cindex serial line support
2081 This contains serial line support for Unix systems. This is always
2082 included, via the makefile variable @code{SER_HARDWIRE}; override this
2083 variable in the @file{.mh} file to avoid it.
2086 This contains serial line support for 32-bit programs running under DOS,
2087 using the DJGPP (a.k.a.@: GO32) execution environment.
2089 @cindex TCP remote support
2091 This contains generic TCP support using sockets.
2094 @section Host Conditionals
2096 When @value{GDBN} is configured and compiled, various macros are
2097 defined or left undefined, to control compilation based on the
2098 attributes of the host system. These macros and their meanings (or if
2099 the meaning is not documented here, then one of the source files where
2100 they are used is indicated) are:
2103 @item @value{GDBN}INIT_FILENAME
2104 The default name of @value{GDBN}'s initialization file (normally
2108 This macro is deprecated.
2111 Define this if your system does not have a @code{<sys/file.h>}.
2113 @item SIGWINCH_HANDLER
2114 If your host defines @code{SIGWINCH}, you can define this to be the name
2115 of a function to be called if @code{SIGWINCH} is received.
2117 @item SIGWINCH_HANDLER_BODY
2118 Define this to expand into code that will define the function named by
2119 the expansion of @code{SIGWINCH_HANDLER}.
2121 @item ALIGN_STACK_ON_STARTUP
2122 @cindex stack alignment
2123 Define this if your system is of a sort that will crash in
2124 @code{tgetent} if the stack happens not to be longword-aligned when
2125 @code{main} is called. This is a rare situation, but is known to occur
2126 on several different types of systems.
2128 @item CRLF_SOURCE_FILES
2129 @cindex DOS text files
2130 Define this if host files use @code{\r\n} rather than @code{\n} as a
2131 line terminator. This will cause source file listings to omit @code{\r}
2132 characters when printing and it will allow @code{\r\n} line endings of files
2133 which are ``sourced'' by gdb. It must be possible to open files in binary
2134 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2136 @item DEFAULT_PROMPT
2138 The default value of the prompt string (normally @code{"(gdb) "}).
2141 @cindex terminal device
2142 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2144 @item FCLOSE_PROVIDED
2145 Define this if the system declares @code{fclose} in the headers included
2146 in @code{defs.h}. This isn't needed unless your compiler is unusually
2150 Define this if binary files are opened the same way as text files.
2152 @item GETENV_PROVIDED
2153 Define this if the system declares @code{getenv} in its headers included
2154 in @code{defs.h}. This isn't needed unless your compiler is unusually
2159 In some cases, use the system call @code{mmap} for reading symbol
2160 tables. For some machines this allows for sharing and quick updates.
2163 Define this if the host system has @code{termio.h}.
2170 Values for host-side constants.
2173 Substitute for isatty, if not available.
2176 This is the longest integer type available on the host. If not defined,
2177 it will default to @code{long long} or @code{long}, depending on
2178 @code{CC_HAS_LONG_LONG}.
2180 @item CC_HAS_LONG_LONG
2181 @cindex @code{long long} data type
2182 Define this if the host C compiler supports @code{long long}. This is set
2183 by the @code{configure} script.
2185 @item PRINTF_HAS_LONG_LONG
2186 Define this if the host can handle printing of long long integers via
2187 the printf format conversion specifier @code{ll}. This is set by the
2188 @code{configure} script.
2190 @item HAVE_LONG_DOUBLE
2191 Define this if the host C compiler supports @code{long double}. This is
2192 set by the @code{configure} script.
2194 @item PRINTF_HAS_LONG_DOUBLE
2195 Define this if the host can handle printing of long double float-point
2196 numbers via the printf format conversion specifier @code{Lg}. This is
2197 set by the @code{configure} script.
2199 @item SCANF_HAS_LONG_DOUBLE
2200 Define this if the host can handle the parsing of long double
2201 float-point numbers via the scanf format conversion specifier
2202 @code{Lg}. This is set by the @code{configure} script.
2204 @item LSEEK_NOT_LINEAR
2205 Define this if @code{lseek (n)} does not necessarily move to byte number
2206 @code{n} in the file. This is only used when reading source files. It
2207 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2210 This macro is used as the argument to @code{lseek} (or, most commonly,
2211 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2212 which is the POSIX equivalent.
2214 @item MMAP_BASE_ADDRESS
2215 When using HAVE_MMAP, the first mapping should go at this address.
2217 @item MMAP_INCREMENT
2218 when using HAVE_MMAP, this is the increment between mappings.
2221 If defined, this should be one or more tokens, such as @code{volatile},
2222 that can be used in both the declaration and definition of functions to
2223 indicate that they never return. The default is already set correctly
2224 if compiling with GCC. This will almost never need to be defined.
2227 If defined, this should be one or more tokens, such as
2228 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2229 of functions to indicate that they never return. The default is already
2230 set correctly if compiling with GCC. This will almost never need to be
2233 @item USE_GENERIC_DUMMY_FRAMES
2234 @cindex generic dummy frames
2235 Define this to 1 if the target is using the generic inferior function
2236 call code. See @code{blockframe.c} for more information.
2240 @value{GDBN} will use the @code{mmalloc} library for memory allocation
2241 for symbol reading if this symbol is defined. Be careful defining it
2242 since there are systems on which @code{mmalloc} does not work for some
2243 reason. One example is the DECstation, where its RPC library can't
2244 cope with our redefinition of @code{malloc} to call @code{mmalloc}.
2245 When defining @code{USE_MMALLOC}, you will also have to set
2246 @code{MMALLOC} in the Makefile, to point to the @code{mmalloc} library. This
2247 define is set when you configure with @samp{--with-mmalloc}.
2251 Define this if you are using @code{mmalloc}, but don't want the overhead
2252 of checking the heap with @code{mmcheck}. Note that on some systems,
2253 the C runtime makes calls to @code{malloc} prior to calling @code{main}, and if
2254 @code{free} is ever called with these pointers after calling
2255 @code{mmcheck} to enable checking, a memory corruption abort is certain
2256 to occur. These systems can still use @code{mmalloc}, but must define
2260 Define this to 1 if the C runtime allocates memory prior to
2261 @code{mmcheck} being called, but that memory is never freed so we don't
2262 have to worry about it triggering a memory corruption abort. The
2263 default is 0, which means that @code{mmcheck} will only install the heap
2264 checking functions if there has not yet been any memory allocation
2265 calls, and if it fails to install the functions, @value{GDBN} will issue a
2266 warning. This is currently defined if you configure using
2267 @samp{--with-mmalloc}.
2269 @item NO_SIGINTERRUPT
2270 @findex siginterrupt
2271 Define this to indicate that @code{siginterrupt} is not available.
2275 Define these to appropriate value for the system @code{lseek}, if not already
2279 This is the signal for stopping @value{GDBN}. Defaults to
2280 @code{SIGTSTP}. (Only redefined for the Convex.)
2283 Define this if the interior's tty should be opened with the @code{O_NOCTTY}
2284 flag. (FIXME: This should be a native-only flag, but @file{inflow.c} is
2288 Means that System V (prior to SVR4) include files are in use. (FIXME:
2289 This symbol is abused in @file{infrun.c}, @file{regex.c},
2290 @file{remote-nindy.c}, and @file{utils.c} for other things, at the
2294 Define this to help placate @code{lint} in some situations.
2297 Define this to override the defaults of @code{__volatile__} or
2302 @node Target Architecture Definition
2304 @chapter Target Architecture Definition
2306 @cindex target architecture definition
2307 @value{GDBN}'s target architecture defines what sort of
2308 machine-language programs @value{GDBN} can work with, and how it works
2311 The target architecture object is implemented as the C structure
2312 @code{struct gdbarch *}. The structure, and its methods, are generated
2313 using the Bourne shell script @file{gdbarch.sh}.
2315 @section Operating System ABI Variant Handling
2316 @cindex OS ABI variants
2318 @value{GDBN} provides a mechanism for handling variations in OS
2319 ABIs. An OS ABI variant may have influence over any number of
2320 variables in the target architecture definition. There are two major
2321 components in the OS ABI mechanism: sniffers and handlers.
2323 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2324 (the architecture may be wildcarded) in an attempt to determine the
2325 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2326 to be @dfn{generic}, while sniffers for a specific architecture are
2327 considered to be @dfn{specific}. A match from a specific sniffer
2328 overrides a match from a generic sniffer. Multiple sniffers for an
2329 architecture/flavour may exist, in order to differentiate between two
2330 different operating systems which use the same basic file format. The
2331 OS ABI framework provides a generic sniffer for ELF-format files which
2332 examines the @code{EI_OSABI} field of the ELF header, as well as note
2333 sections known to be used by several operating systems.
2335 @cindex fine-tuning @code{gdbarch} structure
2336 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2337 selected OS ABI. There may be only one handler for a given OS ABI
2338 for each BFD architecture.
2340 The following OS ABI variants are defined in @file{osabi.h}:
2344 @findex GDB_OSABI_UNKNOWN
2345 @item GDB_OSABI_UNKNOWN
2346 The ABI of the inferior is unknown. The default @code{gdbarch}
2347 settings for the architecture will be used.
2349 @findex GDB_OSABI_SVR4
2350 @item GDB_OSABI_SVR4
2351 UNIX System V Release 4
2353 @findex GDB_OSABI_HURD
2354 @item GDB_OSABI_HURD
2355 GNU using the Hurd kernel
2357 @findex GDB_OSABI_SOLARIS
2358 @item GDB_OSABI_SOLARIS
2361 @findex GDB_OSABI_OSF1
2362 @item GDB_OSABI_OSF1
2363 OSF/1, including Digital UNIX and Compaq Tru64 UNIX
2365 @findex GDB_OSABI_LINUX
2366 @item GDB_OSABI_LINUX
2367 GNU using the Linux kernel
2369 @findex GDB_OSABI_FREEBSD_AOUT
2370 @item GDB_OSABI_FREEBSD_AOUT
2371 FreeBSD using the a.out executable format
2373 @findex GDB_OSABI_FREEBSD_ELF
2374 @item GDB_OSABI_FREEBSD_ELF
2375 FreeBSD using the ELF executable format
2377 @findex GDB_OSABI_NETBSD_AOUT
2378 @item GDB_OSABI_NETBSD_AOUT
2379 NetBSD using the a.out executable format
2381 @findex GDB_OSABI_NETBSD_ELF
2382 @item GDB_OSABI_NETBSD_ELF
2383 NetBSD using the ELF executable format
2385 @findex GDB_OSABI_WINCE
2386 @item GDB_OSABI_WINCE
2389 @findex GDB_OSABI_ARM_EABI_V1
2390 @item GDB_OSABI_ARM_EABI_V1
2391 ARM Embedded ABI version 1
2393 @findex GDB_OSABI_ARM_EABI_V2
2394 @item GDB_OSABI_ARM_EABI_V2
2395 ARM Embedded ABI version 2
2397 @findex GDB_OSABI_ARM_APCS
2398 @item GDB_OSABI_ARM_APCS
2399 Generic ARM Procedure Call Standard
2403 Here are the functions that make up the OS ABI framework:
2405 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2406 Return the name of the OS ABI corresponding to @var{osabi}.
2409 @deftypefun void gdbarch_register_osabi (enum bfd_architecture @var{arch}, enum gdb_osabi @var{osabi}, void (*@var{init_osabi})(struct gdbarch_info @var{info}, struct gdbarch *@var{gdbarch}))
2410 Register the OS ABI handler specified by @var{init_osabi} for the
2411 architecture/OS ABI pair specified by @var{arch} and @var{osabi}.
2414 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2415 Register the OS ABI file sniffer specified by @var{sniffer} for the
2416 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2417 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2418 be generic, and is allowed to examine @var{flavour}-flavoured files for
2422 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2423 Examine the file described by @var{abfd} to determine its OS ABI.
2424 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2428 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2429 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2430 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2431 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2432 architecture, a warning will be issued and the debugging session will continue
2433 with the defaults already established for @var{gdbarch}.
2436 @section Registers and Memory
2438 @value{GDBN}'s model of the target machine is rather simple.
2439 @value{GDBN} assumes the machine includes a bank of registers and a
2440 block of memory. Each register may have a different size.
2442 @value{GDBN} does not have a magical way to match up with the
2443 compiler's idea of which registers are which; however, it is critical
2444 that they do match up accurately. The only way to make this work is
2445 to get accurate information about the order that the compiler uses,
2446 and to reflect that in the @code{REGISTER_NAME} and related macros.
2448 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2450 @section Pointers Are Not Always Addresses
2451 @cindex pointer representation
2452 @cindex address representation
2453 @cindex word-addressed machines
2454 @cindex separate data and code address spaces
2455 @cindex spaces, separate data and code address
2456 @cindex address spaces, separate data and code
2457 @cindex code pointers, word-addressed
2458 @cindex converting between pointers and addresses
2459 @cindex D10V addresses
2461 On almost all 32-bit architectures, the representation of a pointer is
2462 indistinguishable from the representation of some fixed-length number
2463 whose value is the byte address of the object pointed to. On such
2464 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2465 However, architectures with smaller word sizes are often cramped for
2466 address space, so they may choose a pointer representation that breaks this
2467 identity, and allows a larger code address space.
2469 For example, the Mitsubishi D10V is a 16-bit VLIW processor whose
2470 instructions are 32 bits long@footnote{Some D10V instructions are
2471 actually pairs of 16-bit sub-instructions. However, since you can't
2472 jump into the middle of such a pair, code addresses can only refer to
2473 full 32 bit instructions, which is what matters in this explanation.}.
2474 If the D10V used ordinary byte addresses to refer to code locations,
2475 then the processor would only be able to address 64kb of instructions.
2476 However, since instructions must be aligned on four-byte boundaries, the
2477 low two bits of any valid instruction's byte address are always
2478 zero---byte addresses waste two bits. So instead of byte addresses,
2479 the D10V uses word addresses---byte addresses shifted right two bits---to
2480 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2483 However, this means that code pointers and data pointers have different
2484 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2485 @code{0xC020} when used as a data address, but refers to byte address
2486 @code{0x30080} when used as a code address.
2488 (The D10V also uses separate code and data address spaces, which also
2489 affects the correspondence between pointers and addresses, but we're
2490 going to ignore that here; this example is already too long.)
2492 To cope with architectures like this---the D10V is not the only
2493 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2494 byte numbers, and @dfn{pointers}, which are the target's representation
2495 of an address of a particular type of data. In the example above,
2496 @code{0xC020} is the pointer, which refers to one of the addresses
2497 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2498 @value{GDBN} provides functions for turning a pointer into an address
2499 and vice versa, in the appropriate way for the current architecture.
2501 Unfortunately, since addresses and pointers are identical on almost all
2502 processors, this distinction tends to bit-rot pretty quickly. Thus,
2503 each time you port @value{GDBN} to an architecture which does
2504 distinguish between pointers and addresses, you'll probably need to
2505 clean up some architecture-independent code.
2507 Here are functions which convert between pointers and addresses:
2509 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2510 Treat the bytes at @var{buf} as a pointer or reference of type
2511 @var{type}, and return the address it represents, in a manner
2512 appropriate for the current architecture. This yields an address
2513 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2514 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2517 For example, if the current architecture is the Intel x86, this function
2518 extracts a little-endian integer of the appropriate length from
2519 @var{buf} and returns it. However, if the current architecture is the
2520 D10V, this function will return a 16-bit integer extracted from
2521 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2523 If @var{type} is not a pointer or reference type, then this function
2524 will signal an internal error.
2527 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2528 Store the address @var{addr} in @var{buf}, in the proper format for a
2529 pointer of type @var{type} in the current architecture. Note that
2530 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2533 For example, if the current architecture is the Intel x86, this function
2534 stores @var{addr} unmodified as a little-endian integer of the
2535 appropriate length in @var{buf}. However, if the current architecture
2536 is the D10V, this function divides @var{addr} by four if @var{type} is
2537 a pointer to a function, and then stores it in @var{buf}.
2539 If @var{type} is not a pointer or reference type, then this function
2540 will signal an internal error.
2543 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2544 Assuming that @var{val} is a pointer, return the address it represents,
2545 as appropriate for the current architecture.
2547 This function actually works on integral values, as well as pointers.
2548 For pointers, it performs architecture-specific conversions as
2549 described above for @code{extract_typed_address}.
2552 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2553 Create and return a value representing a pointer of type @var{type} to
2554 the address @var{addr}, as appropriate for the current architecture.
2555 This function performs architecture-specific conversions as described
2556 above for @code{store_typed_address}.
2560 @value{GDBN} also provides functions that do the same tasks, but assume
2561 that pointers are simply byte addresses; they aren't sensitive to the
2562 current architecture, beyond knowing the appropriate endianness.
2564 @deftypefun CORE_ADDR extract_address (void *@var{addr}, int len)
2565 Extract a @var{len}-byte number from @var{addr} in the appropriate
2566 endianness for the current architecture, and return it. Note that
2567 @var{addr} refers to @value{GDBN}'s memory, not the inferior's.
2569 This function should only be used in architecture-specific code; it
2570 doesn't have enough information to turn bits into a true address in the
2571 appropriate way for the current architecture. If you can, use
2572 @code{extract_typed_address} instead.
2575 @deftypefun void store_address (void *@var{addr}, int @var{len}, LONGEST @var{val})
2576 Store @var{val} at @var{addr} as a @var{len}-byte integer, in the
2577 appropriate endianness for the current architecture. Note that
2578 @var{addr} refers to a buffer in @value{GDBN}'s memory, not the
2581 This function should only be used in architecture-specific code; it
2582 doesn't have enough information to turn a true address into bits in the
2583 appropriate way for the current architecture. If you can, use
2584 @code{store_typed_address} instead.
2588 Here are some macros which architectures can define to indicate the
2589 relationship between pointers and addresses. These have default
2590 definitions, appropriate for architectures on which all pointers are
2591 simple unsigned byte addresses.
2593 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2594 Assume that @var{buf} holds a pointer of type @var{type}, in the
2595 appropriate format for the current architecture. Return the byte
2596 address the pointer refers to.
2598 This function may safely assume that @var{type} is either a pointer or a
2599 C@t{++} reference type.
2602 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2603 Store in @var{buf} a pointer of type @var{type} representing the address
2604 @var{addr}, in the appropriate format for the current architecture.
2606 This function may safely assume that @var{type} is either a pointer or a
2607 C@t{++} reference type.
2611 @section Raw and Virtual Register Representations
2612 @cindex raw register representation
2613 @cindex virtual register representation
2614 @cindex representations, raw and virtual registers
2616 @emph{Maintainer note: This section is pretty much obsolete. The
2617 functionality described here has largely been replaced by
2618 pseudo-registers and the mechanisms described in @ref{Target
2619 Architecture Definition, , Using Different Register and Memory Data
2620 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
2621 Bug Tracking Database} and
2622 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
2623 up-to-date information.}
2625 Some architectures use one representation for a value when it lives in a
2626 register, but use a different representation when it lives in memory.
2627 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
2628 the target registers, and the @dfn{virtual} representation is the one
2629 used in memory, and within @value{GDBN} @code{struct value} objects.
2631 @emph{Maintainer note: Notice that the same mechanism is being used to
2632 both convert a register to a @code{struct value} and alternative
2635 For almost all data types on almost all architectures, the virtual and
2636 raw representations are identical, and no special handling is needed.
2637 However, they do occasionally differ. For example:
2641 The x86 architecture supports an 80-bit @code{long double} type. However, when
2642 we store those values in memory, they occupy twelve bytes: the
2643 floating-point number occupies the first ten, and the final two bytes
2644 are unused. This keeps the values aligned on four-byte boundaries,
2645 allowing more efficient access. Thus, the x86 80-bit floating-point
2646 type is the raw representation, and the twelve-byte loosely-packed
2647 arrangement is the virtual representation.
2650 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
2651 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
2652 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
2653 raw representation, and the trimmed 32-bit representation is the
2654 virtual representation.
2657 In general, the raw representation is determined by the architecture, or
2658 @value{GDBN}'s interface to the architecture, while the virtual representation
2659 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
2660 @code{registers}, holds the register contents in raw format, and the
2661 @value{GDBN} remote protocol transmits register values in raw format.
2663 Your architecture may define the following macros to request
2664 conversions between the raw and virtual format:
2666 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
2667 Return non-zero if register number @var{reg}'s value needs different raw
2668 and virtual formats.
2670 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
2671 unless this macro returns a non-zero value for that register.
2674 @deftypefn {Target Macro} int REGISTER_RAW_SIZE (int @var{reg})
2675 The size of register number @var{reg}'s raw value. This is the number
2676 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
2677 remote protocol packet.
2680 @deftypefn {Target Macro} int REGISTER_VIRTUAL_SIZE (int @var{reg})
2681 The size of register number @var{reg}'s value, in its virtual format.
2682 This is the size a @code{struct value}'s buffer will have, holding that
2686 @deftypefn {Target Macro} struct type *REGISTER_VIRTUAL_TYPE (int @var{reg})
2687 This is the type of the virtual representation of register number
2688 @var{reg}. Note that there is no need for a macro giving a type for the
2689 register's raw form; once the register's value has been obtained, @value{GDBN}
2690 always uses the virtual form.
2693 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2694 Convert the value of register number @var{reg} to @var{type}, which
2695 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2696 at @var{from} holds the register's value in raw format; the macro should
2697 convert the value to virtual format, and place it at @var{to}.
2699 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
2700 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
2701 arguments in different orders.
2703 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
2704 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
2708 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2709 Convert the value of register number @var{reg} to @var{type}, which
2710 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2711 at @var{from} holds the register's value in raw format; the macro should
2712 convert the value to virtual format, and place it at @var{to}.
2714 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
2715 their @var{reg} and @var{type} arguments in different orders.
2719 @section Using Different Register and Memory Data Representations
2720 @cindex register representation
2721 @cindex memory representation
2722 @cindex representations, register and memory
2723 @cindex register data formats, converting
2724 @cindex @code{struct value}, converting register contents to
2726 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
2727 significant change. Many of the macros and functions refered to in this
2728 section are likely to be subject to further revision. See
2729 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
2730 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
2731 further information. cagney/2002-05-06.}
2733 Some architectures can represent a data object in a register using a
2734 form that is different to the objects more normal memory representation.
2740 The Alpha architecture can represent 32 bit integer values in
2741 floating-point registers.
2744 The x86 architecture supports 80-bit floating-point registers. The
2745 @code{long double} data type occupies 96 bits in memory but only 80 bits
2746 when stored in a register.
2750 In general, the register representation of a data type is determined by
2751 the architecture, or @value{GDBN}'s interface to the architecture, while
2752 the memory representation is determined by the Application Binary
2755 For almost all data types on almost all architectures, the two
2756 representations are identical, and no special handling is needed.
2757 However, they do occasionally differ. Your architecture may define the
2758 following macros to request conversions between the register and memory
2759 representations of a data type:
2761 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
2762 Return non-zero if the representation of a data value stored in this
2763 register may be different to the representation of that same data value
2764 when stored in memory.
2766 When non-zero, the macros @code{REGISTER_TO_VALUE} and
2767 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
2770 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2771 Convert the value of register number @var{reg} to a data object of type
2772 @var{type}. The buffer at @var{from} holds the register's value in raw
2773 format; the converted value should be placed in the buffer at @var{to}.
2775 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2776 their @var{reg} and @var{type} arguments in different orders.
2778 You should only use @code{REGISTER_TO_VALUE} with registers for which
2779 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2782 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2783 Convert a data value of type @var{type} to register number @var{reg}'
2786 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2787 their @var{reg} and @var{type} arguments in different orders.
2789 You should only use @code{VALUE_TO_REGISTER} with registers for which
2790 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2793 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
2794 See @file{mips-tdep.c}. It does not do what you want.
2798 @section Frame Interpretation
2800 @section Inferior Call Setup
2802 @section Compiler Characteristics
2804 @section Target Conditionals
2806 This section describes the macros that you can use to define the target
2811 @item ADDITIONAL_OPTIONS
2812 @itemx ADDITIONAL_OPTION_CASES
2813 @itemx ADDITIONAL_OPTION_HANDLER
2814 @itemx ADDITIONAL_OPTION_HELP
2815 @findex ADDITIONAL_OPTION_HELP
2816 @findex ADDITIONAL_OPTION_HANDLER
2817 @findex ADDITIONAL_OPTION_CASES
2818 @findex ADDITIONAL_OPTIONS
2819 These are a set of macros that allow the addition of additional command
2820 line options to @value{GDBN}. They are currently used only for the unsupported
2821 i960 Nindy target, and should not be used in any other configuration.
2823 @item ADDR_BITS_REMOVE (addr)
2824 @findex ADDR_BITS_REMOVE
2825 If a raw machine instruction address includes any bits that are not
2826 really part of the address, then define this macro to expand into an
2827 expression that zeroes those bits in @var{addr}. This is only used for
2828 addresses of instructions, and even then not in all contexts.
2830 For example, the two low-order bits of the PC on the Hewlett-Packard PA
2831 2.0 architecture contain the privilege level of the corresponding
2832 instruction. Since instructions must always be aligned on four-byte
2833 boundaries, the processor masks out these bits to generate the actual
2834 address of the instruction. ADDR_BITS_REMOVE should filter out these
2835 bits with an expression such as @code{((addr) & ~3)}.
2837 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
2838 @findex ADDRESS_TO_POINTER
2839 Store in @var{buf} a pointer of type @var{type} representing the address
2840 @var{addr}, in the appropriate format for the current architecture.
2841 This macro may safely assume that @var{type} is either a pointer or a
2842 C@t{++} reference type.
2843 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
2845 @item BEFORE_MAIN_LOOP_HOOK
2846 @findex BEFORE_MAIN_LOOP_HOOK
2847 Define this to expand into any code that you want to execute before the
2848 main loop starts. Although this is not, strictly speaking, a target
2849 conditional, that is how it is currently being used. Note that if a
2850 configuration were to define it one way for a host and a different way
2851 for the target, @value{GDBN} will probably not compile, let alone run
2852 correctly. This macro is currently used only for the unsupported i960 Nindy
2853 target, and should not be used in any other configuration.
2855 @item BELIEVE_PCC_PROMOTION
2856 @findex BELIEVE_PCC_PROMOTION
2857 Define if the compiler promotes a @code{short} or @code{char}
2858 parameter to an @code{int}, but still reports the parameter as its
2859 original type, rather than the promoted type.
2861 @item BELIEVE_PCC_PROMOTION_TYPE
2862 @findex BELIEVE_PCC_PROMOTION_TYPE
2863 Define this if @value{GDBN} should believe the type of a @code{short}
2864 argument when compiled by @code{pcc}, but look within a full int space to get
2865 its value. Only defined for Sun-3 at present.
2867 @item BITS_BIG_ENDIAN
2868 @findex BITS_BIG_ENDIAN
2869 Define this if the numbering of bits in the targets does @strong{not} match the
2870 endianness of the target byte order. A value of 1 means that the bits
2871 are numbered in a big-endian bit order, 0 means little-endian.
2875 This is the character array initializer for the bit pattern to put into
2876 memory where a breakpoint is set. Although it's common to use a trap
2877 instruction for a breakpoint, it's not required; for instance, the bit
2878 pattern could be an invalid instruction. The breakpoint must be no
2879 longer than the shortest instruction of the architecture.
2881 @code{BREAKPOINT} has been deprecated in favor of
2882 @code{BREAKPOINT_FROM_PC}.
2884 @item BIG_BREAKPOINT
2885 @itemx LITTLE_BREAKPOINT
2886 @findex LITTLE_BREAKPOINT
2887 @findex BIG_BREAKPOINT
2888 Similar to BREAKPOINT, but used for bi-endian targets.
2890 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
2891 favor of @code{BREAKPOINT_FROM_PC}.
2893 @item REMOTE_BREAKPOINT
2894 @itemx LITTLE_REMOTE_BREAKPOINT
2895 @itemx BIG_REMOTE_BREAKPOINT
2896 @findex BIG_REMOTE_BREAKPOINT
2897 @findex LITTLE_REMOTE_BREAKPOINT
2898 @findex REMOTE_BREAKPOINT
2899 Similar to BREAKPOINT, but used for remote targets.
2901 @code{BIG_REMOTE_BREAKPOINT} and @code{LITTLE_REMOTE_BREAKPOINT} have been
2902 deprecated in favor of @code{BREAKPOINT_FROM_PC}.
2904 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
2905 @findex BREAKPOINT_FROM_PC
2906 Use the program counter to determine the contents and size of a
2907 breakpoint instruction. It returns a pointer to a string of bytes
2908 that encode a breakpoint instruction, stores the length of the string
2909 to *@var{lenptr}, and adjusts pc (if necessary) to point to the actual
2910 memory location where the breakpoint should be inserted.
2912 Although it is common to use a trap instruction for a breakpoint, it's
2913 not required; for instance, the bit pattern could be an invalid
2914 instruction. The breakpoint must be no longer than the shortest
2915 instruction of the architecture.
2917 Replaces all the other @var{BREAKPOINT} macros.
2919 @item MEMORY_INSERT_BREAKPOINT (@var{addr}, @var{contents_cache})
2920 @itemx MEMORY_REMOVE_BREAKPOINT (@var{addr}, @var{contents_cache})
2921 @findex MEMORY_REMOVE_BREAKPOINT
2922 @findex MEMORY_INSERT_BREAKPOINT
2923 Insert or remove memory based breakpoints. Reasonable defaults
2924 (@code{default_memory_insert_breakpoint} and
2925 @code{default_memory_remove_breakpoint} respectively) have been
2926 provided so that it is not necessary to define these for most
2927 architectures. Architectures which may want to define
2928 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
2929 likely have instructions that are oddly sized or are not stored in a
2930 conventional manner.
2932 It may also be desirable (from an efficiency standpoint) to define
2933 custom breakpoint insertion and removal routines if
2934 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
2938 @findex CALL_DUMMY_P
2939 A C expression that is non-zero when the target supports inferior function
2942 @item CALL_DUMMY_WORDS
2943 @findex CALL_DUMMY_WORDS
2944 Pointer to an array of @code{LONGEST} words of data containing
2945 host-byte-ordered @code{REGISTER_BYTES} sized values that partially
2946 specify the sequence of instructions needed for an inferior function
2949 Should be deprecated in favor of a macro that uses target-byte-ordered
2952 @item SIZEOF_CALL_DUMMY_WORDS
2953 @findex SIZEOF_CALL_DUMMY_WORDS
2954 The size of @code{CALL_DUMMY_WORDS}. When @code{CALL_DUMMY_P} this must
2955 return a positive value. See also @code{CALL_DUMMY_LENGTH}.
2959 A static initializer for @code{CALL_DUMMY_WORDS}. Deprecated.
2961 @item CALL_DUMMY_LOCATION
2962 @findex CALL_DUMMY_LOCATION
2963 See the file @file{inferior.h}.
2965 @item CALL_DUMMY_STACK_ADJUST
2966 @findex CALL_DUMMY_STACK_ADJUST
2967 Stack adjustment needed when performing an inferior function call.
2969 Should be deprecated in favor of something like @code{STACK_ALIGN}.
2971 @item CALL_DUMMY_STACK_ADJUST_P
2972 @findex CALL_DUMMY_STACK_ADJUST_P
2973 Predicate for use of @code{CALL_DUMMY_STACK_ADJUST}.
2975 Should be deprecated in favor of something like @code{STACK_ALIGN}.
2977 @item CANNOT_FETCH_REGISTER (@var{regno})
2978 @findex CANNOT_FETCH_REGISTER
2979 A C expression that should be nonzero if @var{regno} cannot be fetched
2980 from an inferior process. This is only relevant if
2981 @code{FETCH_INFERIOR_REGISTERS} is not defined.
2983 @item CANNOT_STORE_REGISTER (@var{regno})
2984 @findex CANNOT_STORE_REGISTER
2985 A C expression that should be nonzero if @var{regno} should not be
2986 written to the target. This is often the case for program counters,
2987 status words, and other special registers. If this is not defined,
2988 @value{GDBN} will assume that all registers may be written.
2990 @item DO_DEFERRED_STORES
2991 @itemx CLEAR_DEFERRED_STORES
2992 @findex CLEAR_DEFERRED_STORES
2993 @findex DO_DEFERRED_STORES
2994 Define this to execute any deferred stores of registers into the inferior,
2995 and to cancel any deferred stores.
2997 Currently only implemented correctly for native Sparc configurations?
2999 @item COERCE_FLOAT_TO_DOUBLE (@var{formal}, @var{actual})
3000 @findex COERCE_FLOAT_TO_DOUBLE
3001 @cindex promotion to @code{double}
3002 @cindex @code{float} arguments
3003 @cindex prototyped functions, passing arguments to
3004 @cindex passing arguments to prototyped functions
3005 Return non-zero if GDB should promote @code{float} values to
3006 @code{double} when calling a non-prototyped function. The argument
3007 @var{actual} is the type of the value we want to pass to the function.
3008 The argument @var{formal} is the type of this argument, as it appears in
3009 the function's definition. Note that @var{formal} may be zero if we
3010 have no debugging information for the function, or if we're passing more
3011 arguments than are officially declared (for example, varargs). This
3012 macro is never invoked if the function definitely has a prototype.
3014 How you should pass arguments to a function depends on whether it was
3015 defined in K&R style or prototype style. If you define a function using
3016 the K&R syntax that takes a @code{float} argument, then callers must
3017 pass that argument as a @code{double}. If you define the function using
3018 the prototype syntax, then you must pass the argument as a @code{float},
3021 Unfortunately, on certain older platforms, the debug info doesn't
3022 indicate reliably how each function was defined. A function type's
3023 @code{TYPE_FLAG_PROTOTYPED} flag may be unset, even if the function was
3024 defined in prototype style. When calling a function whose
3025 @code{TYPE_FLAG_PROTOTYPED} flag is unset, GDB consults the
3026 @code{COERCE_FLOAT_TO_DOUBLE} macro to decide what to do.
3028 @findex standard_coerce_float_to_double
3029 For modern targets, it is proper to assume that, if the prototype flag
3030 is unset, that can be trusted: @code{float} arguments should be promoted
3031 to @code{double}. You should use the function
3032 @code{standard_coerce_float_to_double} to get this behavior.
3034 @findex default_coerce_float_to_double
3035 For some older targets, if the prototype flag is unset, that doesn't
3036 tell us anything. So we guess that, if we don't have a type for the
3037 formal parameter (@i{i.e.}, the first argument to
3038 @code{COERCE_FLOAT_TO_DOUBLE} is null), then we should promote it;
3039 otherwise, we should leave it alone. The function
3040 @code{default_coerce_float_to_double} provides this behavior; it is the
3041 default value, for compatibility with older configurations.
3043 @item int CONVERT_REGISTER_P(@var{regnum})
3044 @findex CONVERT_REGISTER_P
3045 Return non-zero if register @var{regnum} can represent data values in a
3047 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3050 @findex CPLUS_MARKERz
3051 Define this to expand into the character that G@t{++} uses to distinguish
3052 compiler-generated identifiers from programmer-specified identifiers.
3053 By default, this expands into @code{'$'}. Most System V targets should
3054 define this to @code{'.'}.
3056 @item DBX_PARM_SYMBOL_CLASS
3057 @findex DBX_PARM_SYMBOL_CLASS
3058 Hook for the @code{SYMBOL_CLASS} of a parameter when decoding DBX symbol
3059 information. In the i960, parameters can be stored as locals or as
3060 args, depending on the type of the debug record.
3062 @item DECR_PC_AFTER_BREAK
3063 @findex DECR_PC_AFTER_BREAK
3064 Define this to be the amount by which to decrement the PC after the
3065 program encounters a breakpoint. This is often the number of bytes in
3066 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3068 @item DECR_PC_AFTER_HW_BREAK
3069 @findex DECR_PC_AFTER_HW_BREAK
3070 Similarly, for hardware breakpoints.
3072 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3073 @findex DISABLE_UNSETTABLE_BREAK
3074 If defined, this should evaluate to 1 if @var{addr} is in a shared
3075 library in which breakpoints cannot be set and so should be disabled.
3077 @item DO_REGISTERS_INFO
3078 @findex DO_REGISTERS_INFO
3079 If defined, use this to print the value of a register or all registers.
3081 @item PRINT_FLOAT_INFO()
3082 #findex PRINT_FLOAT_INFO
3083 If defined, then the @samp{info float} command will print information about
3084 the processor's floating point unit.
3086 @item DWARF_REG_TO_REGNUM
3087 @findex DWARF_REG_TO_REGNUM
3088 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3089 no conversion will be performed.
3091 @item DWARF2_REG_TO_REGNUM
3092 @findex DWARF2_REG_TO_REGNUM
3093 Convert DWARF2 register number into @value{GDBN} regnum. If not
3094 defined, no conversion will be performed.
3096 @item ECOFF_REG_TO_REGNUM
3097 @findex ECOFF_REG_TO_REGNUM
3098 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3099 no conversion will be performed.
3101 @item END_OF_TEXT_DEFAULT
3102 @findex END_OF_TEXT_DEFAULT
3103 This is an expression that should designate the end of the text section.
3106 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3107 @findex EXTRACT_RETURN_VALUE
3108 Define this to extract a function's return value of type @var{type} from
3109 the raw register state @var{regbuf} and copy that, in virtual format,
3112 @item EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3113 @findex EXTRACT_STRUCT_VALUE_ADDRESS
3114 When defined, extract from the array @var{regbuf} (containing the raw
3115 register state) the @code{CORE_ADDR} at which a function should return
3116 its structure value.
3118 If not defined, @code{EXTRACT_RETURN_VALUE} is used.
3120 @item EXTRACT_STRUCT_VALUE_ADDRESS_P()
3121 @findex EXTRACT_STRUCT_VALUE_ADDRESS_P
3122 Predicate for @code{EXTRACT_STRUCT_VALUE_ADDRESS}.
3126 Deprecated in favor of @code{PRINT_FLOAT_INFO}.
3130 If the virtual frame pointer is kept in a register, then define this
3131 macro to be the number (greater than or equal to zero) of that register.
3133 This should only need to be defined if @code{TARGET_READ_FP} is not
3136 @item FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3137 @findex FRAMELESS_FUNCTION_INVOCATION
3138 Define this to an expression that returns 1 if the function invocation
3139 represented by @var{fi} does not have a stack frame associated with it.
3142 @item FRAME_ARGS_ADDRESS_CORRECT
3143 @findex FRAME_ARGS_ADDRESS_CORRECT
3146 @item FRAME_CHAIN(@var{frame})
3148 Given @var{frame}, return a pointer to the calling frame.
3150 @item FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3151 @findex FRAME_CHAIN_VALID
3152 Define this to be an expression that returns zero if the given frame is
3153 an outermost frame, with no caller, and nonzero otherwise. Several
3154 common definitions are available:
3158 @code{file_frame_chain_valid} is nonzero if the chain pointer is nonzero
3159 and given frame's PC is not inside the startup file (such as
3163 @code{func_frame_chain_valid} is nonzero if the chain
3164 pointer is nonzero and the given frame's PC is not in @code{main} or a
3165 known entry point function (such as @code{_start}).
3168 @code{generic_file_frame_chain_valid} and
3169 @code{generic_func_frame_chain_valid} are equivalent implementations for
3170 targets using generic dummy frames.
3173 @item FRAME_INIT_SAVED_REGS(@var{frame})
3174 @findex FRAME_INIT_SAVED_REGS
3175 See @file{frame.h}. Determines the address of all registers in the
3176 current stack frame storing each in @code{frame->saved_regs}. Space for
3177 @code{frame->saved_regs} shall be allocated by
3178 @code{FRAME_INIT_SAVED_REGS} using either
3179 @code{frame_saved_regs_zalloc} or @code{frame_obstack_alloc}.
3181 @code{FRAME_FIND_SAVED_REGS} and @code{EXTRA_FRAME_INFO} are deprecated.
3183 @item FRAME_NUM_ARGS (@var{fi})
3184 @findex FRAME_NUM_ARGS
3185 For the frame described by @var{fi} return the number of arguments that
3186 are being passed. If the number of arguments is not known, return
3189 @item FRAME_SAVED_PC(@var{frame})
3190 @findex FRAME_SAVED_PC
3191 Given @var{frame}, return the pc saved there. This is the return
3194 @item FUNCTION_EPILOGUE_SIZE
3195 @findex FUNCTION_EPILOGUE_SIZE
3196 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3197 function end symbol is 0. For such targets, you must define
3198 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3199 function's epilogue.
3201 @item FUNCTION_START_OFFSET
3202 @findex FUNCTION_START_OFFSET
3203 An integer, giving the offset in bytes from a function's address (as
3204 used in the values of symbols, function pointers, etc.), and the
3205 function's first genuine instruction.
3207 This is zero on almost all machines: the function's address is usually
3208 the address of its first instruction. However, on the VAX, for example,
3209 each function starts with two bytes containing a bitmask indicating
3210 which registers to save upon entry to the function. The VAX @code{call}
3211 instructions check this value, and save the appropriate registers
3212 automatically. Thus, since the offset from the function's address to
3213 its first instruction is two bytes, @code{FUNCTION_START_OFFSET} would
3216 @item GCC_COMPILED_FLAG_SYMBOL
3217 @itemx GCC2_COMPILED_FLAG_SYMBOL
3218 @findex GCC2_COMPILED_FLAG_SYMBOL
3219 @findex GCC_COMPILED_FLAG_SYMBOL
3220 If defined, these are the names of the symbols that @value{GDBN} will
3221 look for to detect that GCC compiled the file. The default symbols
3222 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3223 respectively. (Currently only defined for the Delta 68.)
3225 @item @value{GDBN}_MULTI_ARCH
3226 @findex @value{GDBN}_MULTI_ARCH
3227 If defined and non-zero, enables support for multiple architectures
3228 within @value{GDBN}.
3230 This support can be enabled at two levels. At level one, only
3231 definitions for previously undefined macros are provided; at level two,
3232 a multi-arch definition of all architecture dependent macros will be
3235 @item @value{GDBN}_TARGET_IS_HPPA
3236 @findex @value{GDBN}_TARGET_IS_HPPA
3237 This determines whether horrible kludge code in @file{dbxread.c} and
3238 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3239 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3242 @item GET_LONGJMP_TARGET
3243 @findex GET_LONGJMP_TARGET
3244 For most machines, this is a target-dependent parameter. On the
3245 DECstation and the Iris, this is a native-dependent parameter, since
3246 the header file @file{setjmp.h} is needed to define it.
3248 This macro determines the target PC address that @code{longjmp} will jump to,
3249 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3250 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3251 pointer. It examines the current state of the machine as needed.
3253 @item GET_SAVED_REGISTER
3254 @findex GET_SAVED_REGISTER
3255 @findex get_saved_register
3256 Define this if you need to supply your own definition for the function
3257 @code{get_saved_register}.
3259 @item IBM6000_TARGET
3260 @findex IBM6000_TARGET
3261 Shows that we are configured for an IBM RS/6000 target. This
3262 conditional should be eliminated (FIXME) and replaced by
3263 feature-specific macros. It was introduced in a haste and we are
3264 repenting at leisure.
3266 @item I386_USE_GENERIC_WATCHPOINTS
3267 An x86-based target can define this to use the generic x86 watchpoint
3268 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3270 @item SYMBOLS_CAN_START_WITH_DOLLAR
3271 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3272 Some systems have routines whose names start with @samp{$}. Giving this
3273 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3274 routines when parsing tokens that begin with @samp{$}.
3276 On HP-UX, certain system routines (millicode) have names beginning with
3277 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3278 routine that handles inter-space procedure calls on PA-RISC.
3280 @item INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3281 @findex INIT_EXTRA_FRAME_INFO
3282 If additional information about the frame is required this should be
3283 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3284 is allocated using @code{frame_obstack_alloc}.
3286 @item INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3287 @findex INIT_FRAME_PC
3288 This is a C statement that sets the pc of the frame pointed to by
3289 @var{prev}. [By default...]
3291 @item INNER_THAN (@var{lhs}, @var{rhs})
3293 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3294 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3295 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3298 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3299 @findex gdbarch_in_function_epilogue_p
3300 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3301 The epilogue of a function is defined as the part of a function where
3302 the stack frame of the function already has been destroyed up to the
3303 final `return from function call' instruction.
3305 @item SIGTRAMP_START (@var{pc})
3306 @findex SIGTRAMP_START
3307 @itemx SIGTRAMP_END (@var{pc})
3308 @findex SIGTRAMP_END
3309 Define these to be the start and end address of the @code{sigtramp} for the
3310 given @var{pc}. On machines where the address is just a compile time
3311 constant, the macro expansion will typically just ignore the supplied
3314 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3315 @findex IN_SOLIB_CALL_TRAMPOLINE
3316 Define this to evaluate to nonzero if the program is stopped in the
3317 trampoline that connects to a shared library.
3319 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3320 @findex IN_SOLIB_RETURN_TRAMPOLINE
3321 Define this to evaluate to nonzero if the program is stopped in the
3322 trampoline that returns from a shared library.
3324 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3325 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3326 Define this to evaluate to nonzero if the program is stopped in the
3329 @item SKIP_SOLIB_RESOLVER (@var{pc})
3330 @findex SKIP_SOLIB_RESOLVER
3331 Define this to evaluate to the (nonzero) address at which execution
3332 should continue to get past the dynamic linker's symbol resolution
3333 function. A zero value indicates that it is not important or necessary
3334 to set a breakpoint to get through the dynamic linker and that single
3335 stepping will suffice.
3337 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3338 @findex INTEGER_TO_ADDRESS
3339 @cindex converting integers to addresses
3340 Define this when the architecture needs to handle non-pointer to address
3341 conversions specially. Converts that value to an address according to
3342 the current architectures conventions.
3344 @emph{Pragmatics: When the user copies a well defined expression from
3345 their source code and passes it, as a parameter, to @value{GDBN}'s
3346 @code{print} command, they should get the same value as would have been
3347 computed by the target program. Any deviation from this rule can cause
3348 major confusion and annoyance, and needs to be justified carefully. In
3349 other words, @value{GDBN} doesn't really have the freedom to do these
3350 conversions in clever and useful ways. It has, however, been pointed
3351 out that users aren't complaining about how @value{GDBN} casts integers
3352 to pointers; they are complaining that they can't take an address from a
3353 disassembly listing and give it to @code{x/i}. Adding an architecture
3354 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3355 @value{GDBN} to ``get it right'' in all circumstances.}
3357 @xref{Target Architecture Definition, , Pointers Are Not Always
3360 @item IS_TRAPPED_INTERNALVAR (@var{name})
3361 @findex IS_TRAPPED_INTERNALVAR
3362 This is an ugly hook to allow the specification of special actions that
3363 should occur as a side-effect of setting the value of a variable
3364 internal to @value{GDBN}. Currently only used by the h8500. Note that this
3365 could be either a host or target conditional.
3367 @item NEED_TEXT_START_END
3368 @findex NEED_TEXT_START_END
3369 Define this if @value{GDBN} should determine the start and end addresses of the
3370 text section. (Seems dubious.)
3372 @item NO_HIF_SUPPORT
3373 @findex NO_HIF_SUPPORT
3374 (Specific to the a29k.)
3376 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3377 @findex POINTER_TO_ADDRESS
3378 Assume that @var{buf} holds a pointer of type @var{type}, in the
3379 appropriate format for the current architecture. Return the byte
3380 address the pointer refers to.
3381 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3383 @item REGISTER_CONVERTIBLE (@var{reg})
3384 @findex REGISTER_CONVERTIBLE
3385 Return non-zero if @var{reg} uses different raw and virtual formats.
3386 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3388 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3389 @findex REGISTER_TO_VALUE
3390 Convert the raw contents of register @var{regnum} into a value of type
3392 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3394 @item REGISTER_RAW_SIZE (@var{reg})
3395 @findex REGISTER_RAW_SIZE
3396 Return the raw size of @var{reg}; defaults to the size of the register's
3398 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3400 @item REGISTER_VIRTUAL_SIZE (@var{reg})
3401 @findex REGISTER_VIRTUAL_SIZE
3402 Return the virtual size of @var{reg}; defaults to the size of the
3403 register's virtual type.
3404 Return the virtual size of @var{reg}.
3405 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3407 @item REGISTER_VIRTUAL_TYPE (@var{reg})
3408 @findex REGISTER_VIRTUAL_TYPE
3409 Return the virtual type of @var{reg}.
3410 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3412 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3413 @findex REGISTER_CONVERT_TO_VIRTUAL
3414 Convert the value of register @var{reg} from its raw form to its virtual
3416 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3418 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3419 @findex REGISTER_CONVERT_TO_RAW
3420 Convert the value of register @var{reg} from its virtual form to its raw
3422 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3424 @item RETURN_VALUE_ON_STACK(@var{type})
3425 @findex RETURN_VALUE_ON_STACK
3426 @cindex returning structures by value
3427 @cindex structures, returning by value
3429 Return non-zero if values of type TYPE are returned on the stack, using
3430 the ``struct convention'' (i.e., the caller provides a pointer to a
3431 buffer in which the callee should store the return value). This
3432 controls how the @samp{finish} command finds a function's return value,
3433 and whether an inferior function call reserves space on the stack for
3436 The full logic @value{GDBN} uses here is kind of odd.
3440 If the type being returned by value is not a structure, union, or array,
3441 and @code{RETURN_VALUE_ON_STACK} returns zero, then @value{GDBN}
3442 concludes the value is not returned using the struct convention.
3445 Otherwise, @value{GDBN} calls @code{USE_STRUCT_CONVENTION} (see below).
3446 If that returns non-zero, @value{GDBN} assumes the struct convention is
3450 In other words, to indicate that a given type is returned by value using
3451 the struct convention, that type must be either a struct, union, array,
3452 or something @code{RETURN_VALUE_ON_STACK} likes, @emph{and} something
3453 that @code{USE_STRUCT_CONVENTION} likes.
3455 Note that, in C and C@t{++}, arrays are never returned by value. In those
3456 languages, these predicates will always see a pointer type, never an
3457 array type. All the references above to arrays being returned by value
3458 apply only to other languages.
3460 @item SOFTWARE_SINGLE_STEP_P()
3461 @findex SOFTWARE_SINGLE_STEP_P
3462 Define this as 1 if the target does not have a hardware single-step
3463 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3465 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breapoints_p})
3466 @findex SOFTWARE_SINGLE_STEP
3467 A function that inserts or removes (depending on
3468 @var{insert_breapoints_p}) breakpoints at each possible destinations of
3469 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3472 @item SOFUN_ADDRESS_MAYBE_MISSING
3473 @findex SOFUN_ADDRESS_MAYBE_MISSING
3474 Somebody clever observed that, the more actual addresses you have in the
3475 debug information, the more time the linker has to spend relocating
3476 them. So whenever there's some other way the debugger could find the
3477 address it needs, you should omit it from the debug info, to make
3480 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3481 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3482 entries in stabs-format debugging information. @code{N_SO} stabs mark
3483 the beginning and ending addresses of compilation units in the text
3484 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3486 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3490 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3491 addresses where the function starts by taking the function name from
3492 the stab, and then looking that up in the minsyms (the
3493 linker/assembler symbol table). In other words, the stab has the
3494 name, and the linker/assembler symbol table is the only place that carries
3498 @code{N_SO} stabs have an address of zero, too. You just look at the
3499 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3500 and guess the starting and ending addresses of the compilation unit from
3504 @item PCC_SOL_BROKEN
3505 @findex PCC_SOL_BROKEN
3506 (Used only in the Convex target.)
3508 @item PC_IN_CALL_DUMMY
3509 @findex PC_IN_CALL_DUMMY
3510 See @file{inferior.h}.
3512 @item PC_IN_SIGTRAMP (@var{pc}, @var{name})
3513 @findex PC_IN_SIGTRAMP
3515 The @dfn{sigtramp} is a routine that the kernel calls (which then calls
3516 the signal handler). On most machines it is a library routine that is
3517 linked into the executable.
3519 This function, given a program counter value in @var{pc} and the
3520 (possibly NULL) name of the function in which that @var{pc} resides,
3521 returns nonzero if the @var{pc} and/or @var{name} show that we are in
3524 @item PC_LOAD_SEGMENT
3525 @findex PC_LOAD_SEGMENT
3526 If defined, print information about the load segment for the program
3527 counter. (Defined only for the RS/6000.)
3531 If the program counter is kept in a register, then define this macro to
3532 be the number (greater than or equal to zero) of that register.
3534 This should only need to be defined if @code{TARGET_READ_PC} and
3535 @code{TARGET_WRITE_PC} are not defined.
3539 The number of the ``next program counter'' register, if defined.
3542 @findex PARM_BOUNDARY
3543 If non-zero, round arguments to a boundary of this many bits before
3544 pushing them on the stack.
3546 @item PRINT_REGISTER_HOOK (@var{regno})
3547 @findex PRINT_REGISTER_HOOK
3548 If defined, this must be a function that prints the contents of the
3549 given register to standard output.
3551 @item PRINT_TYPELESS_INTEGER
3552 @findex PRINT_TYPELESS_INTEGER
3553 This is an obscure substitute for @code{print_longest} that seems to
3554 have been defined for the Convex target.
3556 @item PROCESS_LINENUMBER_HOOK
3557 @findex PROCESS_LINENUMBER_HOOK
3558 A hook defined for XCOFF reading.
3560 @item PROLOGUE_FIRSTLINE_OVERLAP
3561 @findex PROLOGUE_FIRSTLINE_OVERLAP
3562 (Only used in unsupported Convex configuration.)
3566 If defined, this is the number of the processor status register. (This
3567 definition is only used in generic code when parsing "$ps".)
3571 @findex call_function_by_hand
3572 @findex return_command
3573 Used in @samp{call_function_by_hand} to remove an artificial stack
3574 frame and in @samp{return_command} to remove a real stack frame.
3576 @item PUSH_ARGUMENTS (@var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
3577 @findex PUSH_ARGUMENTS
3578 Define this to push arguments onto the stack for inferior function
3579 call. Returns the updated stack pointer value.
3581 @item PUSH_DUMMY_FRAME
3582 @findex PUSH_DUMMY_FRAME
3583 Used in @samp{call_function_by_hand} to create an artificial stack frame.
3585 @item REGISTER_BYTES
3586 @findex REGISTER_BYTES
3587 The total amount of space needed to store @value{GDBN}'s copy of the machine's
3590 @item REGISTER_NAME(@var{i})
3591 @findex REGISTER_NAME
3592 Return the name of register @var{i} as a string. May return @code{NULL}
3593 or @code{NUL} to indicate that register @var{i} is not valid.
3595 @item REGISTER_NAMES
3596 @findex REGISTER_NAMES
3597 Deprecated in favor of @code{REGISTER_NAME}.
3599 @item REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3600 @findex REG_STRUCT_HAS_ADDR
3601 Define this to return 1 if the given type will be passed by pointer
3602 rather than directly.
3604 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3605 @findex SAVE_DUMMY_FRAME_TOS
3606 Used in @samp{call_function_by_hand} to notify the target dependent code
3607 of the top-of-stack value that will be passed to the the inferior code.
3608 This is the value of the @code{SP} after both the dummy frame and space
3609 for parameters/results have been allocated on the stack.
3611 @item SDB_REG_TO_REGNUM
3612 @findex SDB_REG_TO_REGNUM
3613 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3614 defined, no conversion will be done.
3616 @item SHIFT_INST_REGS
3617 @findex SHIFT_INST_REGS
3618 (Only used for m88k targets.)
3620 @item SKIP_PERMANENT_BREAKPOINT
3621 @findex SKIP_PERMANENT_BREAKPOINT
3622 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
3623 steps over a breakpoint by removing it, stepping one instruction, and
3624 re-inserting the breakpoint. However, permanent breakpoints are
3625 hardwired into the inferior, and can't be removed, so this strategy
3626 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
3627 state so that execution will resume just after the breakpoint. This
3628 macro does the right thing even when the breakpoint is in the delay slot
3629 of a branch or jump.
3631 @item SKIP_PROLOGUE (@var{pc})
3632 @findex SKIP_PROLOGUE
3633 A C expression that returns the address of the ``real'' code beyond the
3634 function entry prologue found at @var{pc}.
3636 @item SKIP_TRAMPOLINE_CODE (@var{pc})
3637 @findex SKIP_TRAMPOLINE_CODE
3638 If the target machine has trampoline code that sits between callers and
3639 the functions being called, then define this macro to return a new PC
3640 that is at the start of the real function.
3644 If the stack-pointer is kept in a register, then define this macro to be
3645 the number (greater than or equal to zero) of that register.
3647 This should only need to be defined if @code{TARGET_WRITE_SP} and
3648 @code{TARGET_WRITE_SP} are not defined.
3650 @item STAB_REG_TO_REGNUM
3651 @findex STAB_REG_TO_REGNUM
3652 Define this to convert stab register numbers (as gotten from `r'
3653 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
3656 @item STACK_ALIGN (@var{addr})
3658 Define this to adjust the address to the alignment required for the
3661 @item STEP_SKIPS_DELAY (@var{addr})
3662 @findex STEP_SKIPS_DELAY
3663 Define this to return true if the address is of an instruction with a
3664 delay slot. If a breakpoint has been placed in the instruction's delay
3665 slot, @value{GDBN} will single-step over that instruction before resuming
3666 normally. Currently only defined for the Mips.
3668 @item STORE_RETURN_VALUE (@var{type}, @var{valbuf})
3669 @findex STORE_RETURN_VALUE
3670 A C expression that stores a function return value of type @var{type},
3671 where @var{valbuf} is the address of the value to be stored.
3673 @item SUN_FIXED_LBRAC_BUG
3674 @findex SUN_FIXED_LBRAC_BUG
3675 (Used only for Sun-3 and Sun-4 targets.)
3677 @item SYMBOL_RELOADING_DEFAULT
3678 @findex SYMBOL_RELOADING_DEFAULT
3679 The default value of the ``symbol-reloading'' variable. (Never defined in
3682 @item TARGET_CHAR_BIT
3683 @findex TARGET_CHAR_BIT
3684 Number of bits in a char; defaults to 8.
3686 @item TARGET_CHAR_SIGNED
3687 @findex TARGET_CHAR_SIGNED
3688 Non-zero if @code{char} is normally signed on this architecture; zero if
3689 it should be unsigned.
3691 The ISO C standard requires the compiler to treat @code{char} as
3692 equivalent to either @code{signed char} or @code{unsigned char}; any
3693 character in the standard execution set is supposed to be positive.
3694 Most compilers treat @code{char} as signed, but @code{char} is unsigned
3695 on the IBM S/390, RS6000, and PowerPC targets.
3697 @item TARGET_COMPLEX_BIT
3698 @findex TARGET_COMPLEX_BIT
3699 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
3701 At present this macro is not used.
3703 @item TARGET_DOUBLE_BIT
3704 @findex TARGET_DOUBLE_BIT
3705 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
3707 @item TARGET_DOUBLE_COMPLEX_BIT
3708 @findex TARGET_DOUBLE_COMPLEX_BIT
3709 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
3711 At present this macro is not used.
3713 @item TARGET_FLOAT_BIT
3714 @findex TARGET_FLOAT_BIT
3715 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
3717 @item TARGET_INT_BIT
3718 @findex TARGET_INT_BIT
3719 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3721 @item TARGET_LONG_BIT
3722 @findex TARGET_LONG_BIT
3723 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3725 @item TARGET_LONG_DOUBLE_BIT
3726 @findex TARGET_LONG_DOUBLE_BIT
3727 Number of bits in a long double float;
3728 defaults to @code{2 * TARGET_DOUBLE_BIT}.
3730 @item TARGET_LONG_LONG_BIT
3731 @findex TARGET_LONG_LONG_BIT
3732 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
3734 @item TARGET_PTR_BIT
3735 @findex TARGET_PTR_BIT
3736 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
3738 @item TARGET_SHORT_BIT
3739 @findex TARGET_SHORT_BIT
3740 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
3742 @item TARGET_READ_PC
3743 @findex TARGET_READ_PC
3744 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
3745 @findex TARGET_WRITE_PC
3746 @itemx TARGET_READ_SP
3747 @findex TARGET_READ_SP
3748 @itemx TARGET_WRITE_SP
3749 @findex TARGET_WRITE_SP
3750 @itemx TARGET_READ_FP
3751 @findex TARGET_READ_FP
3757 These change the behavior of @code{read_pc}, @code{write_pc},
3758 @code{read_sp}, @code{write_sp} and @code{read_fp}. For most targets,
3759 these may be left undefined. @value{GDBN} will call the read and write
3760 register functions with the relevant @code{_REGNUM} argument.
3762 These macros are useful when a target keeps one of these registers in a
3763 hard to get at place; for example, part in a segment register and part
3764 in an ordinary register.
3766 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
3767 @findex TARGET_VIRTUAL_FRAME_POINTER
3768 Returns a @code{(register, offset)} pair representing the virtual
3769 frame pointer in use at the code address @var{pc}. If virtual
3770 frame pointers are not used, a default definition simply returns
3771 @code{FP_REGNUM}, with an offset of zero.
3773 @item TARGET_HAS_HARDWARE_WATCHPOINTS
3774 If non-zero, the target has support for hardware-assisted
3775 watchpoints. @xref{Algorithms, watchpoints}, for more details and
3776 other related macros.
3778 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
3779 @findex TARGET_PRINT_INSN
3780 This is the function used by @value{GDBN} to print an assembly
3781 instruction. It prints the instruction at address @var{addr} in
3782 debugged memory and returns the length of the instruction, in bytes. If
3783 a target doesn't define its own printing routine, it defaults to an
3784 accessor function for the global pointer @code{tm_print_insn}. This
3785 usually points to a function in the @code{opcodes} library (@pxref{Support
3786 Libraries, ,Opcodes}). @var{info} is a structure (of type
3787 @code{disassemble_info}) defined in @file{include/dis-asm.h} used to
3788 pass information to the instruction decoding routine.
3790 @item USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
3791 @findex USE_STRUCT_CONVENTION
3792 If defined, this must be an expression that is nonzero if a value of the
3793 given @var{type} being returned from a function must have space
3794 allocated for it on the stack. @var{gcc_p} is true if the function
3795 being considered is known to have been compiled by GCC; this is helpful
3796 for systems where GCC is known to use different calling convention than
3799 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
3800 @findex VALUE_TO_REGISTER
3801 Convert a value of type @var{type} into the raw contents of register
3803 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3805 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3806 @findex VARIABLES_INSIDE_BLOCK
3807 For dbx-style debugging information, if the compiler puts variable
3808 declarations inside LBRAC/RBRAC blocks, this should be defined to be
3809 nonzero. @var{desc} is the value of @code{n_desc} from the
3810 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
3811 presence of either the @code{GCC_COMPILED_SYMBOL} or the
3812 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
3814 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3815 @findex OS9K_VARIABLES_INSIDE_BLOCK
3816 Similarly, for OS/9000. Defaults to 1.
3819 Motorola M68K target conditionals.
3823 Define this to be the 4-bit location of the breakpoint trap vector. If
3824 not defined, it will default to @code{0xf}.
3826 @item REMOTE_BPT_VECTOR
3827 Defaults to @code{1}.
3830 @section Adding a New Target
3832 @cindex adding a target
3833 The following files add a target to @value{GDBN}:
3837 @item gdb/config/@var{arch}/@var{ttt}.mt
3838 Contains a Makefile fragment specific to this target. Specifies what
3839 object files are needed for target @var{ttt}, by defining
3840 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
3841 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
3844 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
3845 but these are now deprecated, replaced by autoconf, and may go away in
3846 future versions of @value{GDBN}.
3848 @item gdb/@var{ttt}-tdep.c
3849 Contains any miscellaneous code required for this target machine. On
3850 some machines it doesn't exist at all. Sometimes the macros in
3851 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
3852 as functions here instead, and the macro is simply defined to call the
3853 function. This is vastly preferable, since it is easier to understand
3856 @item gdb/@var{arch}-tdep.c
3857 @itemx gdb/@var{arch}-tdep.h
3858 This often exists to describe the basic layout of the target machine's
3859 processor chip (registers, stack, etc.). If used, it is included by
3860 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
3863 @item gdb/config/@var{arch}/tm-@var{ttt}.h
3864 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
3865 macro definitions about the target machine's registers, stack frame
3866 format and instructions.
3868 New targets do not need this file and should not create it.
3870 @item gdb/config/@var{arch}/tm-@var{arch}.h
3871 This often exists to describe the basic layout of the target machine's
3872 processor chip (registers, stack, etc.). If used, it is included by
3873 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
3876 New targets do not need this file and should not create it.
3880 If you are adding a new operating system for an existing CPU chip, add a
3881 @file{config/tm-@var{os}.h} file that describes the operating system
3882 facilities that are unusual (extra symbol table info; the breakpoint
3883 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
3884 that just @code{#include}s @file{tm-@var{arch}.h} and
3885 @file{config/tm-@var{os}.h}.
3888 @section Converting an existing Target Architecture to Multi-arch
3889 @cindex converting targets to multi-arch
3891 This section describes the current accepted best practice for converting
3892 an existing target architecture to the multi-arch framework.
3894 The process consists of generating, testing, posting and committing a
3895 sequence of patches. Each patch must contain a single change, for
3901 Directly convert a group of functions into macros (the conversion does
3902 not change the behavior of any of the functions).
3905 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
3909 Enable multi-arch level one.
3912 Delete one or more files.
3917 There isn't a size limit on a patch, however, a developer is strongly
3918 encouraged to keep the patch size down.
3920 Since each patch is well defined, and since each change has been tested
3921 and shows no regressions, the patches are considered @emph{fairly}
3922 obvious. Such patches, when submitted by developers listed in the
3923 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
3924 process may be more complicated and less clear. The developer is
3925 expected to use their judgment and is encouraged to seek advice as
3928 @subsection Preparation
3930 The first step is to establish control. Build (with @option{-Werror}
3931 enabled) and test the target so that there is a baseline against which
3932 the debugger can be compared.
3934 At no stage can the test results regress or @value{GDBN} stop compiling
3935 with @option{-Werror}.
3937 @subsection Add the multi-arch initialization code
3939 The objective of this step is to establish the basic multi-arch
3940 framework. It involves
3945 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
3946 above is from the original example and uses K&R C. @value{GDBN}
3947 has since converted to ISO C but lets ignore that.} that creates
3950 static struct gdbarch *
3951 d10v_gdbarch_init (info, arches)
3952 struct gdbarch_info info;
3953 struct gdbarch_list *arches;
3955 struct gdbarch *gdbarch;
3956 /* there is only one d10v architecture */
3958 return arches->gdbarch;
3959 gdbarch = gdbarch_alloc (&info, NULL);
3967 A per-architecture dump function to print any architecture specific
3971 mips_dump_tdep (struct gdbarch *current_gdbarch,
3972 struct ui_file *file)
3974 @dots{} code to print architecture specific info @dots{}
3979 A change to @code{_initialize_@var{arch}_tdep} to register this new
3983 _initialize_mips_tdep (void)
3985 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
3990 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
3991 @file{config/@var{arch}/tm-@var{arch}.h}.
3995 @subsection Update multi-arch incompatible mechanisms
3997 Some mechanisms do not work with multi-arch. They include:
4000 @item EXTRA_FRAME_INFO
4002 @item FRAME_FIND_SAVED_REGS
4003 Replaced with @code{FRAME_INIT_SAVED_REGS}
4007 At this stage you could also consider converting the macros into
4010 @subsection Prepare for multi-arch level to one
4012 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4013 and then build and start @value{GDBN} (the change should not be
4014 committed). @value{GDBN} may not build, and once built, it may die with
4015 an internal error listing the architecture methods that must be
4018 Fix any build problems (patch(es)).
4020 Convert all the architecture methods listed, which are only macros, into
4021 functions (patch(es)).
4023 Update @code{@var{arch}_gdbarch_init} to set all the missing
4024 architecture methods and wrap the corresponding macros in @code{#if
4025 !GDB_MULTI_ARCH} (patch(es)).
4027 @subsection Set multi-arch level one
4029 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4032 Any problems with throwing ``the switch'' should have been fixed
4035 @subsection Convert remaining macros
4037 Suggest converting macros into functions (and setting the corresponding
4038 architecture method) in small batches.
4040 @subsection Set multi-arch level to two
4042 This should go smoothly.
4044 @subsection Delete the TM file
4046 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4047 @file{configure.in} updated.
4050 @node Target Vector Definition
4052 @chapter Target Vector Definition
4053 @cindex target vector
4055 The target vector defines the interface between @value{GDBN}'s
4056 abstract handling of target systems, and the nitty-gritty code that
4057 actually exercises control over a process or a serial port.
4058 @value{GDBN} includes some 30-40 different target vectors; however,
4059 each configuration of @value{GDBN} includes only a few of them.
4061 @section File Targets
4063 Both executables and core files have target vectors.
4065 @section Standard Protocol and Remote Stubs
4067 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4068 that runs in the target system. @value{GDBN} provides several sample
4069 @dfn{stubs} that can be integrated into target programs or operating
4070 systems for this purpose; they are named @file{*-stub.c}.
4072 The @value{GDBN} user's manual describes how to put such a stub into
4073 your target code. What follows is a discussion of integrating the
4074 SPARC stub into a complicated operating system (rather than a simple
4075 program), by Stu Grossman, the author of this stub.
4077 The trap handling code in the stub assumes the following upon entry to
4082 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4088 you are in the correct trap window.
4091 As long as your trap handler can guarantee those conditions, then there
4092 is no reason why you shouldn't be able to ``share'' traps with the stub.
4093 The stub has no requirement that it be jumped to directly from the
4094 hardware trap vector. That is why it calls @code{exceptionHandler()},
4095 which is provided by the external environment. For instance, this could
4096 set up the hardware traps to actually execute code which calls the stub
4097 first, and then transfers to its own trap handler.
4099 For the most point, there probably won't be much of an issue with
4100 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4101 and often indicate unrecoverable error conditions. Anyway, this is all
4102 controlled by a table, and is trivial to modify. The most important
4103 trap for us is for @code{ta 1}. Without that, we can't single step or
4104 do breakpoints. Everything else is unnecessary for the proper operation
4105 of the debugger/stub.
4107 From reading the stub, it's probably not obvious how breakpoints work.
4108 They are simply done by deposit/examine operations from @value{GDBN}.
4110 @section ROM Monitor Interface
4112 @section Custom Protocols
4114 @section Transport Layer
4116 @section Builtin Simulator
4119 @node Native Debugging
4121 @chapter Native Debugging
4122 @cindex native debugging
4124 Several files control @value{GDBN}'s configuration for native support:
4128 @item gdb/config/@var{arch}/@var{xyz}.mh
4129 Specifies Makefile fragments needed by a @emph{native} configuration on
4130 machine @var{xyz}. In particular, this lists the required
4131 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4132 Also specifies the header file which describes native support on
4133 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4134 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4135 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4137 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4138 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4139 on machine @var{xyz}. While the file is no longer used for this
4140 purpose, the @file{.mh} suffix remains. Perhaps someone will
4141 eventually rename these fragments so that they have a @file{.mn}
4144 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4145 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4146 macro definitions describing the native system environment, such as
4147 child process control and core file support.
4149 @item gdb/@var{xyz}-nat.c
4150 Contains any miscellaneous C code required for this native support of
4151 this machine. On some machines it doesn't exist at all.
4154 There are some ``generic'' versions of routines that can be used by
4155 various systems. These can be customized in various ways by macros
4156 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4157 the @var{xyz} host, you can just include the generic file's name (with
4158 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4160 Otherwise, if your machine needs custom support routines, you will need
4161 to write routines that perform the same functions as the generic file.
4162 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4163 into @code{NATDEPFILES}.
4167 This contains the @emph{target_ops vector} that supports Unix child
4168 processes on systems which use ptrace and wait to control the child.
4171 This contains the @emph{target_ops vector} that supports Unix child
4172 processes on systems which use /proc to control the child.
4175 This does the low-level grunge that uses Unix system calls to do a ``fork
4176 and exec'' to start up a child process.
4179 This is the low level interface to inferior processes for systems using
4180 the Unix @code{ptrace} call in a vanilla way.
4183 @section Native core file Support
4184 @cindex native core files
4187 @findex fetch_core_registers
4188 @item core-aout.c::fetch_core_registers()
4189 Support for reading registers out of a core file. This routine calls
4190 @code{register_addr()}, see below. Now that BFD is used to read core
4191 files, virtually all machines should use @code{core-aout.c}, and should
4192 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4193 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4195 @item core-aout.c::register_addr()
4196 If your @code{nm-@var{xyz}.h} file defines the macro
4197 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4198 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4199 register number @code{regno}. @code{blockend} is the offset within the
4200 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4201 @file{core-aout.c} will define the @code{register_addr()} function and
4202 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4203 you are using the standard @code{fetch_core_registers()}, you will need
4204 to define your own version of @code{register_addr()}, put it into your
4205 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4206 the @code{NATDEPFILES} list. If you have your own
4207 @code{fetch_core_registers()}, you may not need a separate
4208 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4209 implementations simply locate the registers themselves.@refill
4212 When making @value{GDBN} run native on a new operating system, to make it
4213 possible to debug core files, you will need to either write specific
4214 code for parsing your OS's core files, or customize
4215 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4216 machine uses to define the struct of registers that is accessible
4217 (possibly in the u-area) in a core file (rather than
4218 @file{machine/reg.h}), and an include file that defines whatever header
4219 exists on a core file (e.g. the u-area or a @code{struct core}). Then
4220 modify @code{trad_unix_core_file_p} to use these values to set up the
4221 section information for the data segment, stack segment, any other
4222 segments in the core file (perhaps shared library contents or control
4223 information), ``registers'' segment, and if there are two discontiguous
4224 sets of registers (e.g. integer and float), the ``reg2'' segment. This
4225 section information basically delimits areas in the core file in a
4226 standard way, which the section-reading routines in BFD know how to seek
4229 Then back in @value{GDBN}, you need a matching routine called
4230 @code{fetch_core_registers}. If you can use the generic one, it's in
4231 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4232 It will be passed a char pointer to the entire ``registers'' segment,
4233 its length, and a zero; or a char pointer to the entire ``regs2''
4234 segment, its length, and a 2. The routine should suck out the supplied
4235 register values and install them into @value{GDBN}'s ``registers'' array.
4237 If your system uses @file{/proc} to control processes, and uses ELF
4238 format core files, then you may be able to use the same routines for
4239 reading the registers out of processes and out of core files.
4247 @section shared libraries
4249 @section Native Conditionals
4250 @cindex native conditionals
4252 When @value{GDBN} is configured and compiled, various macros are
4253 defined or left undefined, to control compilation when the host and
4254 target systems are the same. These macros should be defined (or left
4255 undefined) in @file{nm-@var{system}.h}.
4259 @findex ATTACH_DETACH
4260 If defined, then @value{GDBN} will include support for the @code{attach} and
4261 @code{detach} commands.
4263 @item CHILD_PREPARE_TO_STORE
4264 @findex CHILD_PREPARE_TO_STORE
4265 If the machine stores all registers at once in the child process, then
4266 define this to ensure that all values are correct. This usually entails
4267 a read from the child.
4269 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4272 @item FETCH_INFERIOR_REGISTERS
4273 @findex FETCH_INFERIOR_REGISTERS
4274 Define this if the native-dependent code will provide its own routines
4275 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4276 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4277 @file{infptrace.c} is included in this configuration, the default
4278 routines in @file{infptrace.c} are used for these functions.
4280 @item FILES_INFO_HOOK
4281 @findex FILES_INFO_HOOK
4282 (Only defined for Convex.)
4286 This macro is normally defined to be the number of the first floating
4287 point register, if the machine has such registers. As such, it would
4288 appear only in target-specific code. However, @file{/proc} support uses this
4289 to decide whether floats are in use on this target.
4291 @item GET_LONGJMP_TARGET
4292 @findex GET_LONGJMP_TARGET
4293 For most machines, this is a target-dependent parameter. On the
4294 DECstation and the Iris, this is a native-dependent parameter, since
4295 @file{setjmp.h} is needed to define it.
4297 This macro determines the target PC address that @code{longjmp} will jump to,
4298 assuming that we have just stopped at a longjmp breakpoint. It takes a
4299 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4300 pointer. It examines the current state of the machine as needed.
4302 @item I386_USE_GENERIC_WATCHPOINTS
4303 An x86-based machine can define this to use the generic x86 watchpoint
4304 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4307 @findex KERNEL_U_ADDR
4308 Define this to the address of the @code{u} structure (the ``user
4309 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4310 needs to know this so that it can subtract this address from absolute
4311 addresses in the upage, that are obtained via ptrace or from core files.
4312 On systems that don't need this value, set it to zero.
4314 @item KERNEL_U_ADDR_BSD
4315 @findex KERNEL_U_ADDR_BSD
4316 Define this to cause @value{GDBN} to determine the address of @code{u} at
4317 runtime, by using Berkeley-style @code{nlist} on the kernel's image in
4320 @item KERNEL_U_ADDR_HPUX
4321 @findex KERNEL_U_ADDR_HPUX
4322 Define this to cause @value{GDBN} to determine the address of @code{u} at
4323 runtime, by using HP-style @code{nlist} on the kernel's image in the
4326 @item ONE_PROCESS_WRITETEXT
4327 @findex ONE_PROCESS_WRITETEXT
4328 Define this to be able to, when a breakpoint insertion fails, warn the
4329 user that another process may be running with the same executable.
4331 @item PREPARE_TO_PROCEED (@var{select_it})
4332 @findex PREPARE_TO_PROCEED
4333 This (ugly) macro allows a native configuration to customize the way the
4334 @code{proceed} function in @file{infrun.c} deals with switching between
4337 In a multi-threaded task we may select another thread and then continue
4338 or step. But if the old thread was stopped at a breakpoint, it will
4339 immediately cause another breakpoint stop without any execution (i.e. it
4340 will report a breakpoint hit incorrectly). So @value{GDBN} must step over it
4343 If defined, @code{PREPARE_TO_PROCEED} should check the current thread
4344 against the thread that reported the most recent event. If a step-over
4345 is required, it returns TRUE. If @var{select_it} is non-zero, it should
4346 reselect the old thread.
4349 @findex PROC_NAME_FMT
4350 Defines the format for the name of a @file{/proc} device. Should be
4351 defined in @file{nm.h} @emph{only} in order to override the default
4352 definition in @file{procfs.c}.
4355 @findex PTRACE_FP_BUG
4356 See @file{mach386-xdep.c}.
4358 @item PTRACE_ARG3_TYPE
4359 @findex PTRACE_ARG3_TYPE
4360 The type of the third argument to the @code{ptrace} system call, if it
4361 exists and is different from @code{int}.
4363 @item REGISTER_U_ADDR
4364 @findex REGISTER_U_ADDR
4365 Defines the offset of the registers in the ``u area''.
4367 @item SHELL_COMMAND_CONCAT
4368 @findex SHELL_COMMAND_CONCAT
4369 If defined, is a string to prefix on the shell command used to start the
4374 If defined, this is the name of the shell to use to run the inferior.
4375 Defaults to @code{"/bin/sh"}.
4377 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4379 Define this to expand into an expression that will cause the symbols in
4380 @var{filename} to be added to @value{GDBN}'s symbol table. If
4381 @var{readsyms} is zero symbols are not read but any necessary low level
4382 processing for @var{filename} is still done.
4384 @item SOLIB_CREATE_INFERIOR_HOOK
4385 @findex SOLIB_CREATE_INFERIOR_HOOK
4386 Define this to expand into any shared-library-relocation code that you
4387 want to be run just after the child process has been forked.
4389 @item START_INFERIOR_TRAPS_EXPECTED
4390 @findex START_INFERIOR_TRAPS_EXPECTED
4391 When starting an inferior, @value{GDBN} normally expects to trap
4393 the shell execs, and once when the program itself execs. If the actual
4394 number of traps is something other than 2, then define this macro to
4395 expand into the number expected.
4397 @item SVR4_SHARED_LIBS
4398 @findex SVR4_SHARED_LIBS
4399 Define this to indicate that SVR4-style shared libraries are in use.
4403 This determines whether small routines in @file{*-tdep.c}, which
4404 translate register values between @value{GDBN}'s internal
4405 representation and the @file{/proc} representation, are compiled.
4408 @findex U_REGS_OFFSET
4409 This is the offset of the registers in the upage. It need only be
4410 defined if the generic ptrace register access routines in
4411 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4412 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4413 the default value from @file{infptrace.c} is good enough, leave it
4416 The default value means that u.u_ar0 @emph{points to} the location of
4417 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4418 that @code{u.u_ar0} @emph{is} the location of the registers.
4422 See @file{objfiles.c}.
4425 @findex DEBUG_PTRACE
4426 Define this to debug @code{ptrace} calls.
4430 @node Support Libraries
4432 @chapter Support Libraries
4437 BFD provides support for @value{GDBN} in several ways:
4440 @item identifying executable and core files
4441 BFD will identify a variety of file types, including a.out, coff, and
4442 several variants thereof, as well as several kinds of core files.
4444 @item access to sections of files
4445 BFD parses the file headers to determine the names, virtual addresses,
4446 sizes, and file locations of all the various named sections in files
4447 (such as the text section or the data section). @value{GDBN} simply
4448 calls BFD to read or write section @var{x} at byte offset @var{y} for
4451 @item specialized core file support
4452 BFD provides routines to determine the failing command name stored in a
4453 core file, the signal with which the program failed, and whether a core
4454 file matches (i.e.@: could be a core dump of) a particular executable
4457 @item locating the symbol information
4458 @value{GDBN} uses an internal interface of BFD to determine where to find the
4459 symbol information in an executable file or symbol-file. @value{GDBN} itself
4460 handles the reading of symbols, since BFD does not ``understand'' debug
4461 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
4466 @cindex opcodes library
4468 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
4469 library because it's also used in binutils, for @file{objdump}).
4478 @cindex regular expressions library
4489 @item SIGN_EXTEND_CHAR
4491 @item SWITCH_ENUM_BUG
4506 This chapter covers topics that are lower-level than the major
4507 algorithms of @value{GDBN}.
4512 Cleanups are a structured way to deal with things that need to be done
4515 When your code does something (e.g., @code{xmalloc} some memory, or
4516 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
4517 the memory or @code{close} the file), it can make a cleanup. The
4518 cleanup will be done at some future point: when the command is finished
4519 and control returns to the top level; when an error occurs and the stack
4520 is unwound; or when your code decides it's time to explicitly perform
4521 cleanups. Alternatively you can elect to discard the cleanups you
4527 @item struct cleanup *@var{old_chain};
4528 Declare a variable which will hold a cleanup chain handle.
4530 @findex make_cleanup
4531 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
4532 Make a cleanup which will cause @var{function} to be called with
4533 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
4534 handle that can later be passed to @code{do_cleanups} or
4535 @code{discard_cleanups}. Unless you are going to call
4536 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
4537 from @code{make_cleanup}.
4540 @item do_cleanups (@var{old_chain});
4541 Do all cleanups added to the chain since the corresponding
4542 @code{make_cleanup} call was made.
4544 @findex discard_cleanups
4545 @item discard_cleanups (@var{old_chain});
4546 Same as @code{do_cleanups} except that it just removes the cleanups from
4547 the chain and does not call the specified functions.
4550 Cleanups are implemented as a chain. The handle returned by
4551 @code{make_cleanups} includes the cleanup passed to the call and any
4552 later cleanups appended to the chain (but not yet discarded or
4556 make_cleanup (a, 0);
4558 struct cleanup *old = make_cleanup (b, 0);
4566 will call @code{c()} and @code{b()} but will not call @code{a()}. The
4567 cleanup that calls @code{a()} will remain in the cleanup chain, and will
4568 be done later unless otherwise discarded.@refill
4570 Your function should explicitly do or discard the cleanups it creates.
4571 Failing to do this leads to non-deterministic behavior since the caller
4572 will arbitrarily do or discard your functions cleanups. This need leads
4573 to two common cleanup styles.
4575 The first style is try/finally. Before it exits, your code-block calls
4576 @code{do_cleanups} with the old cleanup chain and thus ensures that your
4577 code-block's cleanups are always performed. For instance, the following
4578 code-segment avoids a memory leak problem (even when @code{error} is
4579 called and a forced stack unwind occurs) by ensuring that the
4580 @code{xfree} will always be called:
4583 struct cleanup *old = make_cleanup (null_cleanup, 0);
4584 data = xmalloc (sizeof blah);
4585 make_cleanup (xfree, data);
4590 The second style is try/except. Before it exits, your code-block calls
4591 @code{discard_cleanups} with the old cleanup chain and thus ensures that
4592 any created cleanups are not performed. For instance, the following
4593 code segment, ensures that the file will be closed but only if there is
4597 FILE *file = fopen ("afile", "r");
4598 struct cleanup *old = make_cleanup (close_file, file);
4600 discard_cleanups (old);
4604 Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify
4605 that they ``should not be called when cleanups are not in place''. This
4606 means that any actions you need to reverse in the case of an error or
4607 interruption must be on the cleanup chain before you call these
4608 functions, since they might never return to your code (they
4609 @samp{longjmp} instead).
4611 @section Wrapping Output Lines
4612 @cindex line wrap in output
4615 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
4616 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
4617 added in places that would be good breaking points. The utility
4618 routines will take care of actually wrapping if the line width is
4621 The argument to @code{wrap_here} is an indentation string which is
4622 printed @emph{only} if the line breaks there. This argument is saved
4623 away and used later. It must remain valid until the next call to
4624 @code{wrap_here} or until a newline has been printed through the
4625 @code{*_filtered} functions. Don't pass in a local variable and then
4628 It is usually best to call @code{wrap_here} after printing a comma or
4629 space. If you call it before printing a space, make sure that your
4630 indentation properly accounts for the leading space that will print if
4631 the line wraps there.
4633 Any function or set of functions that produce filtered output must
4634 finish by printing a newline, to flush the wrap buffer, before switching
4635 to unfiltered (@code{printf}) output. Symbol reading routines that
4636 print warnings are a good example.
4638 @section @value{GDBN} Coding Standards
4639 @cindex coding standards
4641 @value{GDBN} follows the GNU coding standards, as described in
4642 @file{etc/standards.texi}. This file is also available for anonymous
4643 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
4644 of the standard; in general, when the GNU standard recommends a practice
4645 but does not require it, @value{GDBN} requires it.
4647 @value{GDBN} follows an additional set of coding standards specific to
4648 @value{GDBN}, as described in the following sections.
4653 @value{GDBN} assumes an ISO-C compliant compiler.
4655 @value{GDBN} does not assume an ISO-C or POSIX compliant C library.
4658 @subsection Memory Management
4660 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
4661 @code{calloc}, @code{free} and @code{asprintf}.
4663 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
4664 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
4665 these functions do not return when the memory pool is empty. Instead,
4666 they unwind the stack using cleanups. These functions return
4667 @code{NULL} when requested to allocate a chunk of memory of size zero.
4669 @emph{Pragmatics: By using these functions, the need to check every
4670 memory allocation is removed. These functions provide portable
4673 @value{GDBN} does not use the function @code{free}.
4675 @value{GDBN} uses the function @code{xfree} to return memory to the
4676 memory pool. Consistent with ISO-C, this function ignores a request to
4677 free a @code{NULL} pointer.
4679 @emph{Pragmatics: On some systems @code{free} fails when passed a
4680 @code{NULL} pointer.}
4682 @value{GDBN} can use the non-portable function @code{alloca} for the
4683 allocation of small temporary values (such as strings).
4685 @emph{Pragmatics: This function is very non-portable. Some systems
4686 restrict the memory being allocated to no more than a few kilobytes.}
4688 @value{GDBN} uses the string function @code{xstrdup} and the print
4689 function @code{xasprintf}.
4691 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
4692 functions such as @code{sprintf} are very prone to buffer overflow
4696 @subsection Compiler Warnings
4697 @cindex compiler warnings
4699 With few exceptions, developers should include the configuration option
4700 @samp{--enable-gdb-build-warnings=,-Werror} when building @value{GDBN}.
4701 The exceptions are listed in the file @file{gdb/MAINTAINERS}.
4703 This option causes @value{GDBN} (when built using GCC) to be compiled
4704 with a carefully selected list of compiler warning flags. Any warnings
4705 from those flags being treated as errors.
4707 The current list of warning flags includes:
4711 Since @value{GDBN} coding standard requires all functions to be declared
4712 using a prototype, the flag has the side effect of ensuring that
4713 prototyped functions are always visible with out resorting to
4714 @samp{-Wstrict-prototypes}.
4717 Such code often appears to work except on instruction set architectures
4718 that use register windows.
4725 Since @value{GDBN} uses the @code{format printf} attribute on all
4726 @code{printf} like functions this checks not just @code{printf} calls
4727 but also calls to functions such as @code{fprintf_unfiltered}.
4730 This warning includes uses of the assignment operator within an
4731 @code{if} statement.
4733 @item -Wpointer-arith
4735 @item -Wuninitialized
4738 @emph{Pragmatics: Due to the way that @value{GDBN} is implemented most
4739 functions have unused parameters. Consequently the warning
4740 @samp{-Wunused-parameter} is precluded from the list. The macro
4741 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
4742 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
4743 is being used. The options @samp{-Wall} and @samp{-Wunused} are also
4744 precluded because they both include @samp{-Wunused-parameter}.}
4746 @emph{Pragmatics: @value{GDBN} has not simply accepted the warnings
4747 enabled by @samp{-Wall -Werror -W...}. Instead it is selecting warnings
4748 when and where their benefits can be demonstrated.}
4750 @subsection Formatting
4752 @cindex source code formatting
4753 The standard GNU recommendations for formatting must be followed
4756 A function declaration should not have its name in column zero. A
4757 function definition should have its name in column zero.
4761 static void foo (void);
4769 @emph{Pragmatics: This simplifies scripting. Function definitions can
4770 be found using @samp{^function-name}.}
4772 There must be a space between a function or macro name and the opening
4773 parenthesis of its argument list (except for macro definitions, as
4774 required by C). There must not be a space after an open paren/bracket
4775 or before a close paren/bracket.
4777 While additional whitespace is generally helpful for reading, do not use
4778 more than one blank line to separate blocks, and avoid adding whitespace
4779 after the end of a program line (as of 1/99, some 600 lines had
4780 whitespace after the semicolon). Excess whitespace causes difficulties
4781 for @code{diff} and @code{patch} utilities.
4783 Pointers are declared using the traditional K&R C style:
4797 @subsection Comments
4799 @cindex comment formatting
4800 The standard GNU requirements on comments must be followed strictly.
4802 Block comments must appear in the following form, with no @code{/*}- or
4803 @code{*/}-only lines, and no leading @code{*}:
4806 /* Wait for control to return from inferior to debugger. If inferior
4807 gets a signal, we may decide to start it up again instead of
4808 returning. That is why there is a loop in this function. When
4809 this function actually returns it means the inferior should be left
4810 stopped and @value{GDBN} should read more commands. */
4813 (Note that this format is encouraged by Emacs; tabbing for a multi-line
4814 comment works correctly, and @kbd{M-q} fills the block consistently.)
4816 Put a blank line between the block comments preceding function or
4817 variable definitions, and the definition itself.
4819 In general, put function-body comments on lines by themselves, rather
4820 than trying to fit them into the 20 characters left at the end of a
4821 line, since either the comment or the code will inevitably get longer
4822 than will fit, and then somebody will have to move it anyhow.
4826 @cindex C data types
4827 Code must not depend on the sizes of C data types, the format of the
4828 host's floating point numbers, the alignment of anything, or the order
4829 of evaluation of expressions.
4831 @cindex function usage
4832 Use functions freely. There are only a handful of compute-bound areas
4833 in @value{GDBN} that might be affected by the overhead of a function
4834 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
4835 limited by the target interface (whether serial line or system call).
4837 However, use functions with moderation. A thousand one-line functions
4838 are just as hard to understand as a single thousand-line function.
4840 @emph{Macros are bad, M'kay.}
4841 (But if you have to use a macro, make sure that the macro arguments are
4842 protected with parentheses.)
4846 Declarations like @samp{struct foo *} should be used in preference to
4847 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
4850 @subsection Function Prototypes
4851 @cindex function prototypes
4853 Prototypes must be used when both @emph{declaring} and @emph{defining}
4854 a function. Prototypes for @value{GDBN} functions must include both the
4855 argument type and name, with the name matching that used in the actual
4856 function definition.
4858 All external functions should have a declaration in a header file that
4859 callers include, except for @code{_initialize_*} functions, which must
4860 be external so that @file{init.c} construction works, but shouldn't be
4861 visible to random source files.
4863 Where a source file needs a forward declaration of a static function,
4864 that declaration must appear in a block near the top of the source file.
4867 @subsection Internal Error Recovery
4869 During its execution, @value{GDBN} can encounter two types of errors.
4870 User errors and internal errors. User errors include not only a user
4871 entering an incorrect command but also problems arising from corrupt
4872 object files and system errors when interacting with the target.
4873 Internal errors include situations where @value{GDBN} has detected, at
4874 run time, a corrupt or erroneous situation.
4876 When reporting an internal error, @value{GDBN} uses
4877 @code{internal_error} and @code{gdb_assert}.
4879 @value{GDBN} must not call @code{abort} or @code{assert}.
4881 @emph{Pragmatics: There is no @code{internal_warning} function. Either
4882 the code detected a user error, recovered from it and issued a
4883 @code{warning} or the code failed to correctly recover from the user
4884 error and issued an @code{internal_error}.}
4886 @subsection File Names
4888 Any file used when building the core of @value{GDBN} must be in lower
4889 case. Any file used when building the core of @value{GDBN} must be 8.3
4890 unique. These requirements apply to both source and generated files.
4892 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
4893 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
4894 is introduced to the build process both @file{Makefile.in} and
4895 @file{configure.in} need to be modified accordingly. Compare the
4896 convoluted conversion process needed to transform @file{COPYING} into
4897 @file{copying.c} with the conversion needed to transform
4898 @file{version.in} into @file{version.c}.}
4900 Any file non 8.3 compliant file (that is not used when building the core
4901 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
4903 @emph{Pragmatics: This is clearly a compromise.}
4905 When @value{GDBN} has a local version of a system header file (ex
4906 @file{string.h}) the file name based on the POSIX header prefixed with
4907 @file{gdb_} (@file{gdb_string.h}).
4909 For other files @samp{-} is used as the separator.
4912 @subsection Include Files
4914 All @file{.c} files should include @file{defs.h} first.
4916 All @file{.c} files should explicitly include the headers for any
4917 declarations they refer to. They should not rely on files being
4918 included indirectly.
4920 With the exception of the global definitions supplied by @file{defs.h},
4921 a header file should explicitly include the header declaring any
4922 @code{typedefs} et.al.@: it refers to.
4924 @code{extern} declarations should never appear in @code{.c} files.
4926 All include files should be wrapped in:
4929 #ifndef INCLUDE_FILE_NAME_H
4930 #define INCLUDE_FILE_NAME_H
4936 @subsection Clean Design and Portable Implementation
4939 In addition to getting the syntax right, there's the little question of
4940 semantics. Some things are done in certain ways in @value{GDBN} because long
4941 experience has shown that the more obvious ways caused various kinds of
4944 @cindex assumptions about targets
4945 You can't assume the byte order of anything that comes from a target
4946 (including @var{value}s, object files, and instructions). Such things
4947 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
4948 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
4949 such as @code{bfd_get_32}.
4951 You can't assume that you know what interface is being used to talk to
4952 the target system. All references to the target must go through the
4953 current @code{target_ops} vector.
4955 You can't assume that the host and target machines are the same machine
4956 (except in the ``native'' support modules). In particular, you can't
4957 assume that the target machine's header files will be available on the
4958 host machine. Target code must bring along its own header files --
4959 written from scratch or explicitly donated by their owner, to avoid
4963 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
4964 to write the code portably than to conditionalize it for various
4967 @cindex system dependencies
4968 New @code{#ifdef}'s which test for specific compilers or manufacturers
4969 or operating systems are unacceptable. All @code{#ifdef}'s should test
4970 for features. The information about which configurations contain which
4971 features should be segregated into the configuration files. Experience
4972 has proven far too often that a feature unique to one particular system
4973 often creeps into other systems; and that a conditional based on some
4974 predefined macro for your current system will become worthless over
4975 time, as new versions of your system come out that behave differently
4976 with regard to this feature.
4978 Adding code that handles specific architectures, operating systems,
4979 target interfaces, or hosts, is not acceptable in generic code.
4981 @cindex portable file name handling
4982 @cindex file names, portability
4983 One particularly notorious area where system dependencies tend to
4984 creep in is handling of file names. The mainline @value{GDBN} code
4985 assumes Posix semantics of file names: absolute file names begin with
4986 a forward slash @file{/}, slashes are used to separate leading
4987 directories, case-sensitive file names. These assumptions are not
4988 necessarily true on non-Posix systems such as MS-Windows. To avoid
4989 system-dependent code where you need to take apart or construct a file
4990 name, use the following portable macros:
4993 @findex HAVE_DOS_BASED_FILE_SYSTEM
4994 @item HAVE_DOS_BASED_FILE_SYSTEM
4995 This preprocessing symbol is defined to a non-zero value on hosts
4996 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
4997 symbol to write conditional code which should only be compiled for
5000 @findex IS_DIR_SEPARATOR
5001 @item IS_DIR_SEPARATOR (@var{c})
5002 Evaluates to a non-zero value if @var{c} is a directory separator
5003 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5004 such a character, but on Windows, both @file{/} and @file{\} will
5007 @findex IS_ABSOLUTE_PATH
5008 @item IS_ABSOLUTE_PATH (@var{file})
5009 Evaluates to a non-zero value if @var{file} is an absolute file name.
5010 For Unix and GNU/Linux hosts, a name which begins with a slash
5011 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5012 @file{x:\bar} are also absolute file names.
5014 @findex FILENAME_CMP
5015 @item FILENAME_CMP (@var{f1}, @var{f2})
5016 Calls a function which compares file names @var{f1} and @var{f2} as
5017 appropriate for the underlying host filesystem. For Posix systems,
5018 this simply calls @code{strcmp}; on case-insensitive filesystems it
5019 will call @code{strcasecmp} instead.
5021 @findex DIRNAME_SEPARATOR
5022 @item DIRNAME_SEPARATOR
5023 Evaluates to a character which separates directories in
5024 @code{PATH}-style lists, typically held in environment variables.
5025 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5027 @findex SLASH_STRING
5029 This evaluates to a constant string you should use to produce an
5030 absolute filename from leading directories and the file's basename.
5031 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5032 @code{"\\"} for some Windows-based ports.
5035 In addition to using these macros, be sure to use portable library
5036 functions whenever possible. For example, to extract a directory or a
5037 basename part from a file name, use the @code{dirname} and
5038 @code{basename} library functions (available in @code{libiberty} for
5039 platforms which don't provide them), instead of searching for a slash
5040 with @code{strrchr}.
5042 Another way to generalize @value{GDBN} along a particular interface is with an
5043 attribute struct. For example, @value{GDBN} has been generalized to handle
5044 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5045 by defining the @code{target_ops} structure and having a current target (as
5046 well as a stack of targets below it, for memory references). Whenever
5047 something needs to be done that depends on which remote interface we are
5048 using, a flag in the current target_ops structure is tested (e.g.,
5049 @code{target_has_stack}), or a function is called through a pointer in the
5050 current target_ops structure. In this way, when a new remote interface
5051 is added, only one module needs to be touched---the one that actually
5052 implements the new remote interface. Other examples of
5053 attribute-structs are BFD access to multiple kinds of object file
5054 formats, or @value{GDBN}'s access to multiple source languages.
5056 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5057 the code interfacing between @code{ptrace} and the rest of
5058 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5059 something was very painful. In @value{GDBN} 4.x, these have all been
5060 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5061 with variations between systems the same way any system-independent
5062 file would (hooks, @code{#if defined}, etc.), and machines which are
5063 radically different don't need to use @file{infptrace.c} at all.
5065 All debugging code must be controllable using the @samp{set debug
5066 @var{module}} command. Do not use @code{printf} to print trace
5067 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5068 @code{#ifdef DEBUG}.
5073 @chapter Porting @value{GDBN}
5074 @cindex porting to new machines
5076 Most of the work in making @value{GDBN} compile on a new machine is in
5077 specifying the configuration of the machine. This is done in a
5078 dizzying variety of header files and configuration scripts, which we
5079 hope to make more sensible soon. Let's say your new host is called an
5080 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
5081 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
5082 @samp{sparc-sun-sunos4}). In particular:
5086 In the top level directory, edit @file{config.sub} and add @var{arch},
5087 @var{xvend}, and @var{xos} to the lists of supported architectures,
5088 vendors, and operating systems near the bottom of the file. Also, add
5089 @var{xyz} as an alias that maps to
5090 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
5094 ./config.sub @var{xyz}
5101 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
5105 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
5106 and no error messages.
5109 You need to port BFD, if that hasn't been done already. Porting BFD is
5110 beyond the scope of this manual.
5113 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
5114 your system and set @code{gdb_host} to @var{xyz}, and (unless your
5115 desired target is already available) also edit @file{gdb/configure.tgt},
5116 setting @code{gdb_target} to something appropriate (for instance,
5119 @emph{Maintainer's note: Work in progress. The file
5120 @file{gdb/configure.host} originally needed to be modified when either a
5121 new native target or a new host machine was being added to @value{GDBN}.
5122 Recent changes have removed this requirement. The file now only needs
5123 to be modified when adding a new native configuration. This will likely
5124 changed again in the future.}
5127 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
5128 target-dependent @file{.h} and @file{.c} files used for your
5132 @section Configuring @value{GDBN} for Release
5134 @cindex preparing a release
5135 @cindex making a distribution tarball
5136 From the top level directory (containing @file{gdb}, @file{bfd},
5137 @file{libiberty}, and so on):
5140 make -f Makefile.in gdb.tar.gz
5144 This will properly configure, clean, rebuild any files that are
5145 distributed pre-built (e.g. @file{c-exp.tab.c} or @file{refcard.ps}),
5146 and will then make a tarfile. (If the top level directory has already
5147 been configured, you can just do @code{make gdb.tar.gz} instead.)
5149 This procedure requires:
5157 @code{makeinfo} (texinfo2 level);
5166 @code{yacc} or @code{bison}.
5170 @dots{} and the usual slew of utilities (@code{sed}, @code{tar}, etc.).
5172 @subheading TEMPORARY RELEASE PROCEDURE FOR DOCUMENTATION
5174 @file{gdb.texinfo} is currently marked up using the texinfo-2 macros,
5175 which are not yet a default for anything (but we have to start using
5178 For making paper, the only thing this implies is the right generation of
5179 @file{texinfo.tex} needs to be included in the distribution.
5181 For making info files, however, rather than duplicating the texinfo2
5182 distribution, generate @file{gdb-all.texinfo} locally, and include the
5183 files @file{gdb.info*} in the distribution. Note the plural;
5184 @code{makeinfo} will split the document into one overall file and five
5185 or so included files.
5190 @chapter Releasing @value{GDBN}
5191 @cindex making a new release of gdb
5193 @section Versions and Branches
5195 @subsection Version Identifiers
5197 @value{GDBN}'s version is determined by the file @file{gdb/version.in}.
5199 @value{GDBN}'s mainline uses ISO dates to differentiate between
5200 versions. The CVS repository uses @var{YYYY}-@var{MM}-@var{DD}-cvs
5201 while the corresponding snapshot uses @var{YYYYMMDD}.
5203 @value{GDBN}'s release branch uses a slightly more complicated scheme.
5204 When the branch is first cut, the mainline version identifier is
5205 prefixed with the @var{major}.@var{minor} from of the previous release
5206 series but with .90 appended. As draft releases are drawn from the
5207 branch, the minor minor number (.90) is incremented. Once the first
5208 release (@var{M}.@var{N}) has been made, the version prefix is updated
5209 to @var{M}.@var{N}.0.90 (dot zero, dot ninety). Follow on releases have
5210 an incremented minor minor version number (.0).
5212 Using 5.1 (previous) and 5.2 (current), the example below illustrates a
5213 typical sequence of version identifiers:
5217 final release from previous branch
5218 @item 2002-03-03-cvs
5219 main-line the day the branch is cut
5220 @item 5.1.90-2002-03-03-cvs
5221 corresponding branch version
5223 first draft release candidate
5224 @item 5.1.91-2002-03-17-cvs
5225 updated branch version
5227 second draft release candidate
5228 @item 5.1.92-2002-03-31-cvs
5229 updated branch version
5231 final release candidate (see below)
5234 @item 5.2.0.90-2002-04-07-cvs
5235 updated CVS branch version
5237 second official release
5244 Minor minor minor draft release candidates such as 5.2.0.91 have been
5245 omitted from the example. Such release candidates are, typically, never
5248 For 5.1.93 the bziped tar ball @file{gdb-5.1.93.tar.bz2} is just the
5249 official @file{gdb-5.2.tar} renamed and compressed.
5252 To avoid version conflicts, vendors are expected to modify the file
5253 @file{gdb/version.in} to include a vendor unique alphabetic identifier
5254 (an official @value{GDBN} release never uses alphabetic characters in
5255 its version identifer).
5257 Since @value{GDBN} does not make minor minor minor releases (e.g.,
5258 5.1.0.1) the conflict between that and a minor minor draft release
5259 identifier (e.g., 5.1.0.90) is avoided.
5262 @subsection Branches
5264 @value{GDBN} draws a release series (5.2, 5.2.1, @dots{}) from a single
5265 release branch (gdb_5_2-branch). Since minor minor minor releases
5266 (5.1.0.1) are not made, the need to branch the release branch is avoided
5267 (it also turns out that the effort required for such a a branch and
5268 release is significantly greater than the effort needed to create a new
5269 release from the head of the release branch).
5271 Releases 5.0 and 5.1 used branch and release tags of the form:
5274 gdb_N_M-YYYY-MM-DD-branchpoint
5275 gdb_N_M-YYYY-MM-DD-branch
5276 gdb_M_N-YYYY-MM-DD-release
5279 Release 5.2 is trialing the branch and release tags:
5282 gdb_N_M-YYYY-MM-DD-branchpoint
5284 gdb_M_N-YYYY-MM-DD-release
5287 @emph{Pragmatics: The branchpoint and release tags need to identify when
5288 a branch and release are made. The branch tag, denoting the head of the
5289 branch, does not have this criteria.}
5292 @section Branch Commit Policy
5294 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
5295 5.1 and 5.2 all used the below:
5299 The @file{gdb/MAINTAINERS} file still holds.
5301 Don't fix something on the branch unless/until it is also fixed in the
5302 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
5303 file is better than committing a hack.
5305 When considering a patch for the branch, suggested criteria include:
5306 Does it fix a build? Does it fix the sequence @kbd{break main; run}
5307 when debugging a static binary?
5309 The further a change is from the core of @value{GDBN}, the less likely
5310 the change will worry anyone (e.g., target specific code).
5312 Only post a proposal to change the core of @value{GDBN} after you've
5313 sent individual bribes to all the people listed in the
5314 @file{MAINTAINERS} file @t{;-)}
5317 @emph{Pragmatics: Provided updates are restricted to non-core
5318 functionality there is little chance that a broken change will be fatal.
5319 This means that changes such as adding a new architectures or (within
5320 reason) support for a new host are considered acceptable.}
5323 @section Obsoleting code
5325 Before anything else, poke the other developers (and around the source
5326 code) to see if there is anything that can be removed from @value{GDBN}
5327 (an old target, an unused file).
5329 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
5330 line. Doing this means that it is easy to identify something that has
5331 been obsoleted when greping through the sources.
5333 The process is done in stages --- this is mainly to ensure that the
5334 wider @value{GDBN} community has a reasonable opportunity to respond.
5335 Remember, everything on the Internet takes a week.
5339 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
5340 list} Creating a bug report to track the task's state, is also highly
5345 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
5346 Announcement mailing list}.
5350 Go through and edit all relevant files and lines so that they are
5351 prefixed with the word @code{OBSOLETE}.
5353 Wait until the next GDB version, containing this obsolete code, has been
5356 Remove the obsolete code.
5360 @emph{Maintainer note: While removing old code is regrettable it is
5361 hopefully better for @value{GDBN}'s long term development. Firstly it
5362 helps the developers by removing code that is either no longer relevant
5363 or simply wrong. Secondly since it removes any history associated with
5364 the file (effectively clearing the slate) the developer has a much freer
5365 hand when it comes to fixing broken files.}
5369 @section Before the Branch
5371 The most important objective at this stage is to find and fix simple
5372 changes that become a pain to track once the branch is created. For
5373 instance, configuration problems that stop @value{GDBN} from even
5374 building. If you can't get the problem fixed, document it in the
5375 @file{gdb/PROBLEMS} file.
5377 @subheading Prompt for @file{gdb/NEWS}
5379 People always forget. Send a post reminding them but also if you know
5380 something interesting happened add it yourself. The @code{schedule}
5381 script will mention this in its e-mail.
5383 @subheading Review @file{gdb/README}
5385 Grab one of the nightly snapshots and then walk through the
5386 @file{gdb/README} looking for anything that can be improved. The
5387 @code{schedule} script will mention this in its e-mail.
5389 @subheading Refresh any imported files.
5391 A number of files are taken from external repositories. They include:
5395 @file{texinfo/texinfo.tex}
5397 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
5400 @file{etc/standards.texi}, @file{etc/make-stds.texi}
5403 @subheading Check the ARI
5405 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
5406 (Awk Regression Index ;-) that checks for a number of errors and coding
5407 conventions. The checks include things like using @code{malloc} instead
5408 of @code{xmalloc} and file naming problems. There shouldn't be any
5411 @subsection Review the bug data base
5413 Close anything obviously fixed.
5415 @subsection Check all cross targets build
5417 The targets are listed in @file{gdb/MAINTAINERS}.
5420 @section Cut the Branch
5422 @subheading Create the branch
5427 $ V=`echo $v | sed 's/\./_/g'`
5428 $ D=`date -u +%Y-%m-%d`
5431 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5432 -D $D-gmt gdb_$V-$D-branchpoint insight+dejagnu
5433 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
5434 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight+dejagnu
5437 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5438 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight+dejagnu
5439 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5440 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight+dejagnu
5448 by using @kbd{-D YYYY-MM-DD-gmt} the branch is forced to an exact
5451 the trunk is first taged so that the branch point can easily be found
5453 Insight (which includes GDB) and dejagnu are all tagged at the same time
5455 @file{version.in} gets bumped to avoid version number conflicts
5457 the reading of @file{.cvsrc} is disabled using @file{-f}
5460 @subheading Update @file{version.in}
5465 $ V=`echo $v | sed 's/\./_/g'`
5469 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
5470 -r gdb_$V-branch src/gdb/version.in
5471 cvs -f -d :ext:sources.redhat.com:/cvs/src co
5472 -r gdb_5_2-branch src/gdb/version.in
5474 U src/gdb/version.in
5476 $ echo $u.90-0000-00-00-cvs > version.in
5478 5.1.90-0000-00-00-cvs
5479 $ cvs -f commit version.in
5484 @file{0000-00-00} is used as a date to pump prime the version.in update
5487 @file{.90} and the previous branch version are used as fairly arbitrary
5488 initial branch version number
5492 @subheading Update the web and news pages
5496 @subheading Tweak cron to track the new branch
5498 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
5499 This file needs to be updated so that:
5503 a daily timestamp is added to the file @file{version.in}
5505 the new branch is included in the snapshot process
5509 See the file @file{gdbadmin/cron/README} for how to install the updated
5512 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
5513 any changes. That file is copied to both the branch/ and current/
5514 snapshot directories.
5517 @subheading Update the NEWS and README files
5519 The @file{NEWS} file needs to be updated so that on the branch it refers
5520 to @emph{changes in the current release} while on the trunk it also
5521 refers to @emph{changes since the current release}.
5523 The @file{README} file needs to be updated so that it refers to the
5526 @subheading Post the branch info
5528 Send an announcement to the mailing lists:
5532 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
5534 @email{gdb@@sources.redhat.com, GDB Discsussion mailing list} and
5535 @email{gdb-testers@@sources.redhat.com, GDB Discsussion mailing list}
5538 @emph{Pragmatics: The branch creation is sent to the announce list to
5539 ensure that people people not subscribed to the higher volume discussion
5542 The announcement should include:
5548 how to check out the branch using CVS
5550 the date/number of weeks until the release
5552 the branch commit policy
5556 @section Stabilize the branch
5558 Something goes here.
5560 @section Create a Release
5562 The process of creating and then making available a release is broken
5563 down into a number of stages. The first part addresses the technical
5564 process of creating a releasable tar ball. The later stages address the
5565 process of releasing that tar ball.
5567 When making a release candidate just the first section is needed.
5569 @subsection Create a release candidate
5571 The objective at this stage is to create a set of tar balls that can be
5572 made available as a formal release (or as a less formal release
5575 @subsubheading Freeze the branch
5577 Send out an e-mail notifying everyone that the branch is frozen to
5578 @email{gdb-patches@@sources.redhat.com}.
5580 @subsubheading Establish a few defaults.
5585 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
5587 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5591 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5593 /home/gdbadmin/bin/autoconf
5602 Check the @code{autoconf} version carefully. You want to be using the
5603 version taken from the @file{binutils} snapshot directory. It is very
5604 unlikely that a system installed version of @code{autoconf} (e.g.,
5605 @file{/usr/bin/autoconf}) is correct.
5608 @subsubheading Check out the relevant modules:
5611 $ for m in gdb insight dejagnu
5613 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
5623 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
5624 any confusion between what is written here and what your local
5625 @code{cvs} really does.
5628 @subsubheading Update relevant files.
5634 Major releases get their comments added as part of the mainline. Minor
5635 releases should probably mention any significant bugs that were fixed.
5637 Don't forget to include the @file{ChangeLog} entry.
5640 $ emacs gdb/src/gdb/NEWS
5645 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
5646 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5651 You'll need to update:
5663 $ emacs gdb/src/gdb/README
5668 $ cp gdb/src/gdb/README insight/src/gdb/README
5669 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5672 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
5673 before the initial branch was cut so just a simple substitute is needed
5676 @emph{Maintainer note: Other projects generate @file{README} and
5677 @file{INSTALL} from the core documentation. This might be worth
5680 @item gdb/version.in
5683 $ echo $v > gdb/src/gdb/version.in
5684 $ cat gdb/src/gdb/version.in
5686 $ emacs gdb/src/gdb/version.in
5689 ... Bump to version ...
5691 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
5692 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5695 @item dejagnu/src/dejagnu/configure.in
5697 Dejagnu is more complicated. The version number is a parameter to
5698 @code{AM_INIT_AUTOMAKE}. Tweak it to read something like gdb-5.1.91.
5700 Don't forget to re-generate @file{configure}.
5702 Don't forget to include a @file{ChangeLog} entry.
5705 $ emacs dejagnu/src/dejagnu/configure.in
5710 $ ( cd dejagnu/src/dejagnu && autoconf )
5715 @subsubheading Do the dirty work
5717 This is identical to the process used to create the daily snapshot.
5720 $ for m in gdb insight
5722 ( cd $m/src && gmake -f Makefile.in $m.tar )
5724 $ ( m=dejagnu; cd $m/src && gmake -f Makefile.in $m.tar.bz2 )
5727 @subsubheading Check the source files
5729 You're looking for files that have mysteriously disappeared.
5730 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
5731 for the @file{version.in} update @kbd{cronjob}.
5734 $ ( cd gdb/src && cvs -f -q -n update )
5738 @dots{} lots of generated files @dots{}
5743 @dots{} lots of generated files @dots{}
5748 @emph{Don't worry about the @file{gdb.info-??} or
5749 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
5750 was also generated only something strange with CVS means that they
5751 didn't get supressed). Fixing it would be nice though.}
5753 @subsubheading Create compressed versions of the release
5759 dejagnu/ dejagnu-gdb-5.2.tar.bz2 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
5760 $ for m in gdb insight
5762 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
5763 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
5773 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
5774 in that mode, @code{gzip} does not know the name of the file and, hence,
5775 can not include it in the compressed file. This is also why the release
5776 process runs @code{tar} and @code{bzip2} as separate passes.
5779 @subsection Sanity check the tar ball
5781 Pick a popular machine (Solaris/PPC?) and try the build on that.
5784 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
5789 $ ./gdb/gdb ./gdb/gdb
5793 Breakpoint 1 at 0x80732bc: file main.c, line 734.
5795 Starting program: /tmp/gdb-5.2/gdb/gdb
5797 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
5798 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
5800 $1 = @{argc = 136426532, argv = 0x821b7f0@}
5804 @subsection Make a release candidate available
5806 If this is a release candidate then the only remaining steps are:
5810 Commit @file{version.in} and @file{ChangeLog}
5812 Tweak @file{version.in} (and @file{ChangeLog} to read
5813 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
5814 process can restart.
5816 Make the release candidate available in
5817 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
5819 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
5820 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
5823 @subsection Make a formal release available
5825 (And you thought all that was required was to post an e-mail.)
5827 @subsubheading Install on sware
5829 Copy the new files to both the release and the old release directory:
5832 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
5833 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
5837 Clean up the releases directory so that only the most recent releases
5838 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
5841 $ cd ~ftp/pub/gdb/releases
5846 Update the file @file{README} and @file{.message} in the releases
5853 $ ln README .message
5856 @subsubheading Update the web pages.
5860 @item htdocs/download/ANNOUNCEMENT
5861 This file, which is posted as the official announcement, includes:
5864 General announcement
5866 News. If making an @var{M}.@var{N}.1 release, retain the news from
5867 earlier @var{M}.@var{N} release.
5872 @item htdocs/index.html
5873 @itemx htdocs/news/index.html
5874 @itemx htdocs/download/index.html
5875 These files include:
5878 announcement of the most recent release
5880 news entry (remember to update both the top level and the news directory).
5882 These pages also need to be regenerate using @code{index.sh}.
5884 @item download/onlinedocs/
5885 You need to find the magic command that is used to generate the online
5886 docs from the @file{.tar.bz2}. The best way is to look in the output
5887 from one of the nightly @code{cron} jobs and then just edit accordingly.
5891 $ ~/ss/update-web-docs \
5892 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
5894 /www/sourceware/htdocs/gdb/download/onlinedocs \
5899 Just like the online documentation. Something like:
5902 $ /bin/sh ~/ss/update-web-ari \
5903 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
5905 /www/sourceware/htdocs/gdb/download/ari \
5911 @subsubheading Shadow the pages onto gnu
5913 Something goes here.
5916 @subsubheading Install the @value{GDBN} tar ball on GNU
5918 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
5919 @file{~ftp/gnu/gdb}.
5921 @subsubheading Make the @file{ANNOUNCEMENT}
5923 Post the @file{ANNOUNCEMENT} file you created above to:
5927 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
5929 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
5930 day or so to let things get out)
5932 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
5937 The release is out but you're still not finished.
5939 @subsubheading Commit outstanding changes
5941 In particular you'll need to commit any changes to:
5945 @file{gdb/ChangeLog}
5947 @file{gdb/version.in}
5954 @subsubheading Tag the release
5959 $ d=`date -u +%Y-%m-%d`
5962 $ ( cd insight/src/gdb && cvs -f -q update )
5963 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
5966 Insight is used since that contains more of the release than
5967 @value{GDBN} (@code{dejagnu} doesn't get tagged but I think we can live
5970 @subsubheading Mention the release on the trunk
5972 Just put something in the @file{ChangeLog} so that the trunk also
5973 indicates when the release was made.
5975 @subsubheading Restart @file{gdb/version.in}
5977 If @file{gdb/version.in} does not contain an ISO date such as
5978 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
5979 committed all the release changes it can be set to
5980 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
5981 is important - it affects the snapshot process).
5983 Don't forget the @file{ChangeLog}.
5985 @subsubheading Merge into trunk
5987 The files committed to the branch may also need changes merged into the
5990 @subsubheading Revise the release schedule
5992 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
5993 Discussion List} with an updated announcement. The schedule can be
5994 generated by running:
5997 $ ~/ss/schedule `date +%s` schedule
6001 The first parameter is approximate date/time in seconds (from the epoch)
6002 of the most recent release.
6004 Also update the schedule @code{cronjob}.
6006 @section Post release
6008 Remove any @code{OBSOLETE} code.
6015 The testsuite is an important component of the @value{GDBN} package.
6016 While it is always worthwhile to encourage user testing, in practice
6017 this is rarely sufficient; users typically use only a small subset of
6018 the available commands, and it has proven all too common for a change
6019 to cause a significant regression that went unnoticed for some time.
6021 The @value{GDBN} testsuite uses the DejaGNU testing framework.
6022 DejaGNU is built using @code{Tcl} and @code{expect}. The tests
6023 themselves are calls to various @code{Tcl} procs; the framework runs all the
6024 procs and summarizes the passes and fails.
6026 @section Using the Testsuite
6028 @cindex running the test suite
6029 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
6030 testsuite's objdir) and type @code{make check}. This just sets up some
6031 environment variables and invokes DejaGNU's @code{runtest} script. While
6032 the testsuite is running, you'll get mentions of which test file is in use,
6033 and a mention of any unexpected passes or fails. When the testsuite is
6034 finished, you'll get a summary that looks like this:
6039 # of expected passes 6016
6040 # of unexpected failures 58
6041 # of unexpected successes 5
6042 # of expected failures 183
6043 # of unresolved testcases 3
6044 # of untested testcases 5
6047 The ideal test run consists of expected passes only; however, reality
6048 conspires to keep us from this ideal. Unexpected failures indicate
6049 real problems, whether in @value{GDBN} or in the testsuite. Expected
6050 failures are still failures, but ones which have been decided are too
6051 hard to deal with at the time; for instance, a test case might work
6052 everywhere except on AIX, and there is no prospect of the AIX case
6053 being fixed in the near future. Expected failures should not be added
6054 lightly, since you may be masking serious bugs in @value{GDBN}.
6055 Unexpected successes are expected fails that are passing for some
6056 reason, while unresolved and untested cases often indicate some minor
6057 catastrophe, such as the compiler being unable to deal with a test
6060 When making any significant change to @value{GDBN}, you should run the
6061 testsuite before and after the change, to confirm that there are no
6062 regressions. Note that truly complete testing would require that you
6063 run the testsuite with all supported configurations and a variety of
6064 compilers; however this is more than really necessary. In many cases
6065 testing with a single configuration is sufficient. Other useful
6066 options are to test one big-endian (Sparc) and one little-endian (x86)
6067 host, a cross config with a builtin simulator (powerpc-eabi,
6068 mips-elf), or a 64-bit host (Alpha).
6070 If you add new functionality to @value{GDBN}, please consider adding
6071 tests for it as well; this way future @value{GDBN} hackers can detect
6072 and fix their changes that break the functionality you added.
6073 Similarly, if you fix a bug that was not previously reported as a test
6074 failure, please add a test case for it. Some cases are extremely
6075 difficult to test, such as code that handles host OS failures or bugs
6076 in particular versions of compilers, and it's OK not to try to write
6077 tests for all of those.
6079 @section Testsuite Organization
6081 @cindex test suite organization
6082 The testsuite is entirely contained in @file{gdb/testsuite}. While the
6083 testsuite includes some makefiles and configury, these are very minimal,
6084 and used for little besides cleaning up, since the tests themselves
6085 handle the compilation of the programs that @value{GDBN} will run. The file
6086 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
6087 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
6088 configuration-specific files, typically used for special-purpose
6089 definitions of procs like @code{gdb_load} and @code{gdb_start}.
6091 The tests themselves are to be found in @file{testsuite/gdb.*} and
6092 subdirectories of those. The names of the test files must always end
6093 with @file{.exp}. DejaGNU collects the test files by wildcarding
6094 in the test directories, so both subdirectories and individual files
6095 get chosen and run in alphabetical order.
6097 The following table lists the main types of subdirectories and what they
6098 are for. Since DejaGNU finds test files no matter where they are
6099 located, and since each test file sets up its own compilation and
6100 execution environment, this organization is simply for convenience and
6105 This is the base testsuite. The tests in it should apply to all
6106 configurations of @value{GDBN} (but generic native-only tests may live here).
6107 The test programs should be in the subset of C that is valid K&R,
6108 ANSI/ISO, and C++ (@code{#ifdef}s are allowed if necessary, for instance
6111 @item gdb.@var{lang}
6112 Language-specific tests for any language @var{lang} besides C. Examples are
6113 @file{gdb.c++} and @file{gdb.java}.
6115 @item gdb.@var{platform}
6116 Non-portable tests. The tests are specific to a specific configuration
6117 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
6120 @item gdb.@var{compiler}
6121 Tests specific to a particular compiler. As of this writing (June
6122 1999), there aren't currently any groups of tests in this category that
6123 couldn't just as sensibly be made platform-specific, but one could
6124 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
6127 @item gdb.@var{subsystem}
6128 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
6129 instance, @file{gdb.disasm} exercises various disassemblers, while
6130 @file{gdb.stabs} tests pathways through the stabs symbol reader.
6133 @section Writing Tests
6134 @cindex writing tests
6136 In many areas, the @value{GDBN} tests are already quite comprehensive; you
6137 should be able to copy existing tests to handle new cases.
6139 You should try to use @code{gdb_test} whenever possible, since it
6140 includes cases to handle all the unexpected errors that might happen.
6141 However, it doesn't cost anything to add new test procedures; for
6142 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
6143 calls @code{gdb_test} multiple times.
6145 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
6146 necessary, such as when @value{GDBN} has several valid responses to a command.
6148 The source language programs do @emph{not} need to be in a consistent
6149 style. Since @value{GDBN} is used to debug programs written in many different
6150 styles, it's worth having a mix of styles in the testsuite; for
6151 instance, some @value{GDBN} bugs involving the display of source lines would
6152 never manifest themselves if the programs used GNU coding style
6159 Check the @file{README} file, it often has useful information that does not
6160 appear anywhere else in the directory.
6163 * Getting Started:: Getting started working on @value{GDBN}
6164 * Debugging GDB:: Debugging @value{GDBN} with itself
6167 @node Getting Started,,, Hints
6169 @section Getting Started
6171 @value{GDBN} is a large and complicated program, and if you first starting to
6172 work on it, it can be hard to know where to start. Fortunately, if you
6173 know how to go about it, there are ways to figure out what is going on.
6175 This manual, the @value{GDBN} Internals manual, has information which applies
6176 generally to many parts of @value{GDBN}.
6178 Information about particular functions or data structures are located in
6179 comments with those functions or data structures. If you run across a
6180 function or a global variable which does not have a comment correctly
6181 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
6182 free to submit a bug report, with a suggested comment if you can figure
6183 out what the comment should say. If you find a comment which is
6184 actually wrong, be especially sure to report that.
6186 Comments explaining the function of macros defined in host, target, or
6187 native dependent files can be in several places. Sometimes they are
6188 repeated every place the macro is defined. Sometimes they are where the
6189 macro is used. Sometimes there is a header file which supplies a
6190 default definition of the macro, and the comment is there. This manual
6191 also documents all the available macros.
6192 @c (@pxref{Host Conditionals}, @pxref{Target
6193 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
6196 Start with the header files. Once you have some idea of how
6197 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
6198 @file{gdbtypes.h}), you will find it much easier to understand the
6199 code which uses and creates those symbol tables.
6201 You may wish to process the information you are getting somehow, to
6202 enhance your understanding of it. Summarize it, translate it to another
6203 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
6204 the code to predict what a test case would do and write the test case
6205 and verify your prediction, etc. If you are reading code and your eyes
6206 are starting to glaze over, this is a sign you need to use a more active
6209 Once you have a part of @value{GDBN} to start with, you can find more
6210 specifically the part you are looking for by stepping through each
6211 function with the @code{next} command. Do not use @code{step} or you
6212 will quickly get distracted; when the function you are stepping through
6213 calls another function try only to get a big-picture understanding
6214 (perhaps using the comment at the beginning of the function being
6215 called) of what it does. This way you can identify which of the
6216 functions being called by the function you are stepping through is the
6217 one which you are interested in. You may need to examine the data
6218 structures generated at each stage, with reference to the comments in
6219 the header files explaining what the data structures are supposed to
6222 Of course, this same technique can be used if you are just reading the
6223 code, rather than actually stepping through it. The same general
6224 principle applies---when the code you are looking at calls something
6225 else, just try to understand generally what the code being called does,
6226 rather than worrying about all its details.
6228 @cindex command implementation
6229 A good place to start when tracking down some particular area is with
6230 a command which invokes that feature. Suppose you want to know how
6231 single-stepping works. As a @value{GDBN} user, you know that the
6232 @code{step} command invokes single-stepping. The command is invoked
6233 via command tables (see @file{command.h}); by convention the function
6234 which actually performs the command is formed by taking the name of
6235 the command and adding @samp{_command}, or in the case of an
6236 @code{info} subcommand, @samp{_info}. For example, the @code{step}
6237 command invokes the @code{step_command} function and the @code{info
6238 display} command invokes @code{display_info}. When this convention is
6239 not followed, you might have to use @code{grep} or @kbd{M-x
6240 tags-search} in emacs, or run @value{GDBN} on itself and set a
6241 breakpoint in @code{execute_command}.
6243 @cindex @code{bug-gdb} mailing list
6244 If all of the above fail, it may be appropriate to ask for information
6245 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
6246 wondering if anyone could give me some tips about understanding
6247 @value{GDBN}''---if we had some magic secret we would put it in this manual.
6248 Suggestions for improving the manual are always welcome, of course.
6250 @node Debugging GDB,,,Hints
6252 @section Debugging @value{GDBN} with itself
6253 @cindex debugging @value{GDBN}
6255 If @value{GDBN} is limping on your machine, this is the preferred way to get it
6256 fully functional. Be warned that in some ancient Unix systems, like
6257 Ultrix 4.2, a program can't be running in one process while it is being
6258 debugged in another. Rather than typing the command @kbd{@w{./gdb
6259 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
6260 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
6262 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
6263 @file{.gdbinit} file that sets up some simple things to make debugging
6264 gdb easier. The @code{info} command, when executed without a subcommand
6265 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
6266 gdb. See @file{.gdbinit} for details.
6268 If you use emacs, you will probably want to do a @code{make TAGS} after
6269 you configure your distribution; this will put the machine dependent
6270 routines for your local machine where they will be accessed first by
6273 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
6274 have run @code{fixincludes} if you are compiling with gcc.
6276 @section Submitting Patches
6278 @cindex submitting patches
6279 Thanks for thinking of offering your changes back to the community of
6280 @value{GDBN} users. In general we like to get well designed enhancements.
6281 Thanks also for checking in advance about the best way to transfer the
6284 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
6285 This manual summarizes what we believe to be clean design for @value{GDBN}.
6287 If the maintainers don't have time to put the patch in when it arrives,
6288 or if there is any question about a patch, it goes into a large queue
6289 with everyone else's patches and bug reports.
6291 @cindex legal papers for code contributions
6292 The legal issue is that to incorporate substantial changes requires a
6293 copyright assignment from you and/or your employer, granting ownership
6294 of the changes to the Free Software Foundation. You can get the
6295 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
6296 and asking for it. We recommend that people write in "All programs
6297 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
6298 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
6300 contributed with only one piece of legalese pushed through the
6301 bureaucracy and filed with the FSF. We can't start merging changes until
6302 this paperwork is received by the FSF (their rules, which we follow
6303 since we maintain it for them).
6305 Technically, the easiest way to receive changes is to receive each
6306 feature as a small context diff or unidiff, suitable for @code{patch}.
6307 Each message sent to me should include the changes to C code and
6308 header files for a single feature, plus @file{ChangeLog} entries for
6309 each directory where files were modified, and diffs for any changes
6310 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
6311 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
6312 single feature, they can be split down into multiple messages.
6314 In this way, if we read and like the feature, we can add it to the
6315 sources with a single patch command, do some testing, and check it in.
6316 If you leave out the @file{ChangeLog}, we have to write one. If you leave
6317 out the doc, we have to puzzle out what needs documenting. Etc., etc.
6319 The reason to send each change in a separate message is that we will not
6320 install some of the changes. They'll be returned to you with questions
6321 or comments. If we're doing our job correctly, the message back to you
6322 will say what you have to fix in order to make the change acceptable.
6323 The reason to have separate messages for separate features is so that
6324 the acceptable changes can be installed while one or more changes are
6325 being reworked. If multiple features are sent in a single message, we
6326 tend to not put in the effort to sort out the acceptable changes from
6327 the unacceptable, so none of the features get installed until all are
6330 If this sounds painful or authoritarian, well, it is. But we get a lot
6331 of bug reports and a lot of patches, and many of them don't get
6332 installed because we don't have the time to finish the job that the bug
6333 reporter or the contributor could have done. Patches that arrive
6334 complete, working, and well designed, tend to get installed on the day
6335 they arrive. The others go into a queue and get installed as time
6336 permits, which, since the maintainers have many demands to meet, may not
6337 be for quite some time.
6339 Please send patches directly to
6340 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
6342 @section Obsolete Conditionals
6343 @cindex obsolete code
6345 Fragments of old code in @value{GDBN} sometimes reference or set the following
6346 configuration macros. They should not be used by new code, and old uses
6347 should be removed as those parts of the debugger are otherwise touched.
6350 @item STACK_END_ADDR
6351 This macro used to define where the end of the stack appeared, for use
6352 in interpreting core file formats that don't record this address in the
6353 core file itself. This information is now configured in BFD, and @value{GDBN}
6354 gets the info portably from there. The values in @value{GDBN}'s configuration
6355 files should be moved into BFD configuration files (if needed there),
6356 and deleted from all of @value{GDBN}'s config files.
6358 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
6359 is so old that it has never been converted to use BFD. Now that's old!