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, 2002
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 @findex add_setshow_cmd
726 @findex add_setshow_cmd_full
727 To add paired @samp{set} and @samp{show} commands, use
728 @code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is
729 a slightly simpler interface which is useful when you don't need to
730 further modify the new command structures, while the latter returns
731 the new command structures for manipulation.
733 @cindex deprecating commands
734 @findex deprecate_cmd
735 Before removing commands from the command set it is a good idea to
736 deprecate them for some time. Use @code{deprecate_cmd} on commands or
737 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
738 @code{struct cmd_list_element} as it's first argument. You can use the
739 return value from @code{add_com} or @code{add_cmd} to deprecate the
740 command immediately after it is created.
742 The first time a command is used the user will be warned and offered a
743 replacement (if one exists). Note that the replacement string passed to
744 @code{deprecate_cmd} should be the full name of the command, i.e. the
745 entire string the user should type at the command line.
747 @section UI-Independent Output---the @code{ui_out} Functions
748 @c This section is based on the documentation written by Fernando
749 @c Nasser <fnasser@redhat.com>.
751 @cindex @code{ui_out} functions
752 The @code{ui_out} functions present an abstraction level for the
753 @value{GDBN} output code. They hide the specifics of different user
754 interfaces supported by @value{GDBN}, and thus free the programmer
755 from the need to write several versions of the same code, one each for
756 every UI, to produce output.
758 @subsection Overview and Terminology
760 In general, execution of each @value{GDBN} command produces some sort
761 of output, and can even generate an input request.
763 Output can be generated for the following purposes:
767 to display a @emph{result} of an operation;
770 to convey @emph{info} or produce side-effects of a requested
774 to provide a @emph{notification} of an asynchronous event (including
775 progress indication of a prolonged asynchronous operation);
778 to display @emph{error messages} (including warnings);
781 to show @emph{debug data};
784 to @emph{query} or prompt a user for input (a special case).
788 This section mainly concentrates on how to build result output,
789 although some of it also applies to other kinds of output.
791 Generation of output that displays the results of an operation
792 involves one or more of the following:
796 output of the actual data
799 formatting the output as appropriate for console output, to make it
800 easily readable by humans
803 machine oriented formatting--a more terse formatting to allow for easy
804 parsing by programs which read @value{GDBN}'s output
807 annotation, whose purpose is to help legacy GUIs to identify interesting
811 The @code{ui_out} routines take care of the first three aspects.
812 Annotations are provided by separate annotation routines. Note that use
813 of annotations for an interface between a GUI and @value{GDBN} is
816 Output can be in the form of a single item, which we call a @dfn{field};
817 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
818 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
819 header and a body. In a BNF-like form:
822 @item <table> @expansion{}
823 @code{<header> <body>}
824 @item <header> @expansion{}
825 @code{@{ <column> @}}
826 @item <column> @expansion{}
827 @code{<width> <alignment> <title>}
828 @item <body> @expansion{}
833 @subsection General Conventions
835 Most @code{ui_out} routines are of type @code{void}, the exceptions are
836 @code{ui_out_stream_new} (which returns a pointer to the newly created
837 object) and the @code{make_cleanup} routines.
839 The first parameter is always the @code{ui_out} vector object, a pointer
840 to a @code{struct ui_out}.
842 The @var{format} parameter is like in @code{printf} family of functions.
843 When it is present, there must also be a variable list of arguments
844 sufficient used to satisfy the @code{%} specifiers in the supplied
847 When a character string argument is not used in a @code{ui_out} function
848 call, a @code{NULL} pointer has to be supplied instead.
851 @subsection Table, Tuple and List Functions
853 @cindex list output functions
854 @cindex table output functions
855 @cindex tuple output functions
856 This section introduces @code{ui_out} routines for building lists,
857 tuples and tables. The routines to output the actual data items
858 (fields) are presented in the next section.
860 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
861 containing information about an object; a @dfn{list} is a sequence of
862 fields where each field describes an identical object.
864 Use the @dfn{table} functions when your output consists of a list of
865 rows (tuples) and the console output should include a heading. Use this
866 even when you are listing just one object but you still want the header.
868 @cindex nesting level in @code{ui_out} functions
869 Tables can not be nested. Tuples and lists can be nested up to a
870 maximum of five levels.
872 The overall structure of the table output code is something like this:
887 Here is the description of table-, tuple- and list-related @code{ui_out}
890 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
891 The function @code{ui_out_table_begin} marks the beginning of the output
892 of a table. It should always be called before any other @code{ui_out}
893 function for a given table. @var{nbrofcols} is the number of columns in
894 the table. @var{nr_rows} is the number of rows in the table.
895 @var{tblid} is an optional string identifying the table. The string
896 pointed to by @var{tblid} is copied by the implementation of
897 @code{ui_out_table_begin}, so the application can free the string if it
900 The companion function @code{ui_out_table_end}, described below, marks
901 the end of the table's output.
904 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
905 @code{ui_out_table_header} provides the header information for a single
906 table column. You call this function several times, one each for every
907 column of the table, after @code{ui_out_table_begin}, but before
908 @code{ui_out_table_body}.
910 The value of @var{width} gives the column width in characters. The
911 value of @var{alignment} is one of @code{left}, @code{center}, and
912 @code{right}, and it specifies how to align the header: left-justify,
913 center, or right-justify it. @var{colhdr} points to a string that
914 specifies the column header; the implementation copies that string, so
915 column header strings in @code{malloc}ed storage can be freed after the
919 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
920 This function delimits the table header from the table body.
923 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
924 This function signals the end of a table's output. It should be called
925 after the table body has been produced by the list and field output
928 There should be exactly one call to @code{ui_out_table_end} for each
929 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
930 will signal an internal error.
933 The output of the tuples that represent the table rows must follow the
934 call to @code{ui_out_table_body} and precede the call to
935 @code{ui_out_table_end}. You build a tuple by calling
936 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
937 calls to functions which actually output fields between them.
939 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
940 This function marks the beginning of a tuple output. @var{id} points
941 to an optional string that identifies the tuple; it is copied by the
942 implementation, and so strings in @code{malloc}ed storage can be freed
946 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
947 This function signals an end of a tuple output. There should be exactly
948 one call to @code{ui_out_tuple_end} for each call to
949 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
953 @deftypefun struct cleanup *make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
954 This function first opens the tuple and then establishes a cleanup
955 (@pxref{Coding, Cleanups}) to close the tuple. It provides a convenient
956 and correct implementation of the non-portable@footnote{The function
957 cast is not portable ISO C.} code sequence:
959 struct cleanup *old_cleanup;
960 ui_out_tuple_begin (uiout, "...");
961 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
966 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
967 This function marks the beginning of a list output. @var{id} points to
968 an optional string that identifies the list; it is copied by the
969 implementation, and so strings in @code{malloc}ed storage can be freed
973 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
974 This function signals an end of a list output. There should be exactly
975 one call to @code{ui_out_list_end} for each call to
976 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
980 @deftypefun struct cleanup *make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
981 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
982 opens a list and then establishes cleanup (@pxref{Coding, Cleanups})
983 that will close the list.list.
986 @subsection Item Output Functions
988 @cindex item output functions
989 @cindex field output functions
991 The functions described below produce output for the actual data
992 items, or fields, which contain information about the object.
994 Choose the appropriate function accordingly to your particular needs.
996 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
997 This is the most general output function. It produces the
998 representation of the data in the variable-length argument list
999 according to formatting specifications in @var{format}, a
1000 @code{printf}-like format string. The optional argument @var{fldname}
1001 supplies the name of the field. The data items themselves are
1002 supplied as additional arguments after @var{format}.
1004 This generic function should be used only when it is not possible to
1005 use one of the specialized versions (see below).
1008 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1009 This function outputs a value of an @code{int} variable. It uses the
1010 @code{"%d"} output conversion specification. @var{fldname} specifies
1011 the name of the field.
1014 @deftypefun void ui_out_field_fmt_int (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{fldname}, int @var{value})
1015 This function outputs a value of an @code{int} variable. It differs from
1016 @code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output.
1017 @var{fldname} specifies
1018 the name of the field.
1021 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, CORE_ADDR @var{address})
1022 This function outputs an address.
1025 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1026 This function outputs a string using the @code{"%s"} conversion
1030 Sometimes, there's a need to compose your output piece by piece using
1031 functions that operate on a stream, such as @code{value_print} or
1032 @code{fprintf_symbol_filtered}. These functions accept an argument of
1033 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1034 used to store the data stream used for the output. When you use one
1035 of these functions, you need a way to pass their results stored in a
1036 @code{ui_file} object to the @code{ui_out} functions. To this end,
1037 you first create a @code{ui_stream} object by calling
1038 @code{ui_out_stream_new}, pass the @code{stream} member of that
1039 @code{ui_stream} object to @code{value_print} and similar functions,
1040 and finally call @code{ui_out_field_stream} to output the field you
1041 constructed. When the @code{ui_stream} object is no longer needed,
1042 you should destroy it and free its memory by calling
1043 @code{ui_out_stream_delete}.
1045 @deftypefun struct ui_stream *ui_out_stream_new (struct ui_out *@var{uiout})
1046 This function creates a new @code{ui_stream} object which uses the
1047 same output methods as the @code{ui_out} object whose pointer is
1048 passed in @var{uiout}. It returns a pointer to the newly created
1049 @code{ui_stream} object.
1052 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1053 This functions destroys a @code{ui_stream} object specified by
1057 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1058 This function consumes all the data accumulated in
1059 @code{streambuf->stream} and outputs it like
1060 @code{ui_out_field_string} does. After a call to
1061 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1062 the stream is still valid and may be used for producing more fields.
1065 @strong{Important:} If there is any chance that your code could bail
1066 out before completing output generation and reaching the point where
1067 @code{ui_out_stream_delete} is called, it is necessary to set up a
1068 cleanup, to avoid leaking memory and other resources. Here's a
1069 skeleton code to do that:
1072 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1073 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1078 If the function already has the old cleanup chain set (for other kinds
1079 of cleanups), you just have to add your cleanup to it:
1082 mybuf = ui_out_stream_new (uiout);
1083 make_cleanup (ui_out_stream_delete, mybuf);
1086 Note that with cleanups in place, you should not call
1087 @code{ui_out_stream_delete} directly, or you would attempt to free the
1090 @subsection Utility Output Functions
1092 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1093 This function skips a field in a table. Use it if you have to leave
1094 an empty field without disrupting the table alignment. The argument
1095 @var{fldname} specifies a name for the (missing) filed.
1098 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1099 This function outputs the text in @var{string} in a way that makes it
1100 easy to be read by humans. For example, the console implementation of
1101 this method filters the text through a built-in pager, to prevent it
1102 from scrolling off the visible portion of the screen.
1104 Use this function for printing relatively long chunks of text around
1105 the actual field data: the text it produces is not aligned according
1106 to the table's format. Use @code{ui_out_field_string} to output a
1107 string field, and use @code{ui_out_message}, described below, to
1108 output short messages.
1111 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1112 This function outputs @var{nspaces} spaces. It is handy to align the
1113 text produced by @code{ui_out_text} with the rest of the table or
1117 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1118 This function produces a formatted message, provided that the current
1119 verbosity level is at least as large as given by @var{verbosity}. The
1120 current verbosity level is specified by the user with the @samp{set
1121 verbositylevel} command.@footnote{As of this writing (April 2001),
1122 setting verbosity level is not yet implemented, and is always returned
1123 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1124 argument more than zero will cause the message to never be printed.}
1127 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1128 This function gives the console output filter (a paging filter) a hint
1129 of where to break lines which are too long. Ignored for all other
1130 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1131 be printed to indent the wrapped text on the next line; it must remain
1132 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1133 explicit newline is produced by one of the other functions. If
1134 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1137 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1138 This function flushes whatever output has been accumulated so far, if
1139 the UI buffers output.
1143 @subsection Examples of Use of @code{ui_out} functions
1145 @cindex using @code{ui_out} functions
1146 @cindex @code{ui_out} functions, usage examples
1147 This section gives some practical examples of using the @code{ui_out}
1148 functions to generalize the old console-oriented code in
1149 @value{GDBN}. The examples all come from functions defined on the
1150 @file{breakpoints.c} file.
1152 This example, from the @code{breakpoint_1} function, shows how to
1155 The original code was:
1158 if (!found_a_breakpoint++)
1160 annotate_breakpoints_headers ();
1163 printf_filtered ("Num ");
1165 printf_filtered ("Type ");
1167 printf_filtered ("Disp ");
1169 printf_filtered ("Enb ");
1173 printf_filtered ("Address ");
1176 printf_filtered ("What\n");
1178 annotate_breakpoints_table ();
1182 Here's the new version:
1185 nr_printable_breakpoints = @dots{};
1188 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1190 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1192 if (nr_printable_breakpoints > 0)
1193 annotate_breakpoints_headers ();
1194 if (nr_printable_breakpoints > 0)
1196 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1197 if (nr_printable_breakpoints > 0)
1199 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1200 if (nr_printable_breakpoints > 0)
1202 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1203 if (nr_printable_breakpoints > 0)
1205 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1208 if (nr_printable_breakpoints > 0)
1210 if (TARGET_ADDR_BIT <= 32)
1211 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1213 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1215 if (nr_printable_breakpoints > 0)
1217 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1218 ui_out_table_body (uiout);
1219 if (nr_printable_breakpoints > 0)
1220 annotate_breakpoints_table ();
1223 This example, from the @code{print_one_breakpoint} function, shows how
1224 to produce the actual data for the table whose structure was defined
1225 in the above example. The original code was:
1230 printf_filtered ("%-3d ", b->number);
1232 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1233 || ((int) b->type != bptypes[(int) b->type].type))
1234 internal_error ("bptypes table does not describe type #%d.",
1236 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1238 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1240 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1244 This is the new version:
1248 ui_out_tuple_begin (uiout, "bkpt");
1250 ui_out_field_int (uiout, "number", b->number);
1252 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1253 || ((int) b->type != bptypes[(int) b->type].type))
1254 internal_error ("bptypes table does not describe type #%d.",
1256 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1258 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1260 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1264 This example, also from @code{print_one_breakpoint}, shows how to
1265 produce a complicated output field using the @code{print_expression}
1266 functions which requires a stream to be passed. It also shows how to
1267 automate stream destruction with cleanups. The original code was:
1271 print_expression (b->exp, gdb_stdout);
1277 struct ui_stream *stb = ui_out_stream_new (uiout);
1278 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1281 print_expression (b->exp, stb->stream);
1282 ui_out_field_stream (uiout, "what", local_stream);
1285 This example, also from @code{print_one_breakpoint}, shows how to use
1286 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1291 if (b->dll_pathname == NULL)
1292 printf_filtered ("<any library> ");
1294 printf_filtered ("library \"%s\" ", b->dll_pathname);
1301 if (b->dll_pathname == NULL)
1303 ui_out_field_string (uiout, "what", "<any library>");
1304 ui_out_spaces (uiout, 1);
1308 ui_out_text (uiout, "library \"");
1309 ui_out_field_string (uiout, "what", b->dll_pathname);
1310 ui_out_text (uiout, "\" ");
1314 The following example from @code{print_one_breakpoint} shows how to
1315 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1320 if (b->forked_inferior_pid != 0)
1321 printf_filtered ("process %d ", b->forked_inferior_pid);
1328 if (b->forked_inferior_pid != 0)
1330 ui_out_text (uiout, "process ");
1331 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1332 ui_out_spaces (uiout, 1);
1336 Here's an example of using @code{ui_out_field_string}. The original
1341 if (b->exec_pathname != NULL)
1342 printf_filtered ("program \"%s\" ", b->exec_pathname);
1349 if (b->exec_pathname != NULL)
1351 ui_out_text (uiout, "program \"");
1352 ui_out_field_string (uiout, "what", b->exec_pathname);
1353 ui_out_text (uiout, "\" ");
1357 Finally, here's an example of printing an address. The original code:
1361 printf_filtered ("%s ",
1362 local_hex_string_custom ((unsigned long) b->address, "08l"));
1369 ui_out_field_core_addr (uiout, "Address", b->address);
1373 @section Console Printing
1382 @cindex @code{libgdb}
1383 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1384 to provide an API to @value{GDBN}'s functionality.
1387 @cindex @code{libgdb}
1388 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1389 better able to support graphical and other environments.
1391 Since @code{libgdb} development is on-going, its architecture is still
1392 evolving. The following components have so far been identified:
1396 Observer - @file{gdb-events.h}.
1398 Builder - @file{ui-out.h}
1400 Event Loop - @file{event-loop.h}
1402 Library - @file{gdb.h}
1405 The model that ties these components together is described below.
1407 @section The @code{libgdb} Model
1409 A client of @code{libgdb} interacts with the library in two ways.
1413 As an observer (using @file{gdb-events}) receiving notifications from
1414 @code{libgdb} of any internal state changes (break point changes, run
1417 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1418 obtain various status values from @value{GDBN}.
1421 Since @code{libgdb} could have multiple clients (e.g. a GUI supporting
1422 the existing @value{GDBN} CLI), those clients must co-operate when
1423 controlling @code{libgdb}. In particular, a client must ensure that
1424 @code{libgdb} is idle (i.e. no other client is using @code{libgdb})
1425 before responding to a @file{gdb-event} by making a query.
1427 @section CLI support
1429 At present @value{GDBN}'s CLI is very much entangled in with the core of
1430 @code{libgdb}. Consequently, a client wishing to include the CLI in
1431 their interface needs to carefully co-ordinate its own and the CLI's
1434 It is suggested that the client set @code{libgdb} up to be bi-modal
1435 (alternate between CLI and client query modes). The notes below sketch
1440 The client registers itself as an observer of @code{libgdb}.
1442 The client create and install @code{cli-out} builder using its own
1443 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1444 @code{gdb_stdout} streams.
1446 The client creates a separate custom @code{ui-out} builder that is only
1447 used while making direct queries to @code{libgdb}.
1450 When the client receives input intended for the CLI, it simply passes it
1451 along. Since the @code{cli-out} builder is installed by default, all
1452 the CLI output in response to that command is routed (pronounced rooted)
1453 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1454 At the same time, the client is kept abreast of internal changes by
1455 virtue of being a @code{libgdb} observer.
1457 The only restriction on the client is that it must wait until
1458 @code{libgdb} becomes idle before initiating any queries (using the
1459 client's custom builder).
1461 @section @code{libgdb} components
1463 @subheading Observer - @file{gdb-events.h}
1464 @file{gdb-events} provides the client with a very raw mechanism that can
1465 be used to implement an observer. At present it only allows for one
1466 observer and that observer must, internally, handle the need to delay
1467 the processing of any event notifications until after @code{libgdb} has
1468 finished the current command.
1470 @subheading Builder - @file{ui-out.h}
1471 @file{ui-out} provides the infrastructure necessary for a client to
1472 create a builder. That builder is then passed down to @code{libgdb}
1473 when doing any queries.
1475 @subheading Event Loop - @file{event-loop.h}
1476 @c There could be an entire section on the event-loop
1477 @file{event-loop}, currently non-re-entrant, provides a simple event
1478 loop. A client would need to either plug its self into this loop or,
1479 implement a new event-loop that GDB would use.
1481 The event-loop will eventually be made re-entrant. This is so that
1482 @value{GDB} can better handle the problem of some commands blocking
1483 instead of returning.
1485 @subheading Library - @file{gdb.h}
1486 @file{libgdb} is the most obvious component of this system. It provides
1487 the query interface. Each function is parameterized by a @code{ui-out}
1488 builder. The result of the query is constructed using that builder
1489 before the query function returns.
1491 @node Symbol Handling
1493 @chapter Symbol Handling
1495 Symbols are a key part of @value{GDBN}'s operation. Symbols include variables,
1496 functions, and types.
1498 @section Symbol Reading
1500 @cindex symbol reading
1501 @cindex reading of symbols
1502 @cindex symbol files
1503 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
1504 file is the file containing the program which @value{GDBN} is
1505 debugging. @value{GDBN} can be directed to use a different file for
1506 symbols (with the @samp{symbol-file} command), and it can also read
1507 more symbols via the @samp{add-file} and @samp{load} commands, or while
1508 reading symbols from shared libraries.
1510 @findex find_sym_fns
1511 Symbol files are initially opened by code in @file{symfile.c} using
1512 the BFD library (@pxref{Support Libraries}). BFD identifies the type
1513 of the file by examining its header. @code{find_sym_fns} then uses
1514 this identification to locate a set of symbol-reading functions.
1516 @findex add_symtab_fns
1517 @cindex @code{sym_fns} structure
1518 @cindex adding a symbol-reading module
1519 Symbol-reading modules identify themselves to @value{GDBN} by calling
1520 @code{add_symtab_fns} during their module initialization. The argument
1521 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
1522 name (or name prefix) of the symbol format, the length of the prefix,
1523 and pointers to four functions. These functions are called at various
1524 times to process symbol files whose identification matches the specified
1527 The functions supplied by each module are:
1530 @item @var{xyz}_symfile_init(struct sym_fns *sf)
1532 @cindex secondary symbol file
1533 Called from @code{symbol_file_add} when we are about to read a new
1534 symbol file. This function should clean up any internal state (possibly
1535 resulting from half-read previous files, for example) and prepare to
1536 read a new symbol file. Note that the symbol file which we are reading
1537 might be a new ``main'' symbol file, or might be a secondary symbol file
1538 whose symbols are being added to the existing symbol table.
1540 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
1541 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
1542 new symbol file being read. Its @code{private} field has been zeroed,
1543 and can be modified as desired. Typically, a struct of private
1544 information will be @code{malloc}'d, and a pointer to it will be placed
1545 in the @code{private} field.
1547 There is no result from @code{@var{xyz}_symfile_init}, but it can call
1548 @code{error} if it detects an unavoidable problem.
1550 @item @var{xyz}_new_init()
1552 Called from @code{symbol_file_add} when discarding existing symbols.
1553 This function needs only handle the symbol-reading module's internal
1554 state; the symbol table data structures visible to the rest of
1555 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
1556 arguments and no result. It may be called after
1557 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
1558 may be called alone if all symbols are simply being discarded.
1560 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
1562 Called from @code{symbol_file_add} to actually read the symbols from a
1563 symbol-file into a set of psymtabs or symtabs.
1565 @code{sf} points to the @code{struct sym_fns} originally passed to
1566 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
1567 the offset between the file's specified start address and its true
1568 address in memory. @code{mainline} is 1 if this is the main symbol
1569 table being read, and 0 if a secondary symbol file (e.g. shared library
1570 or dynamically loaded file) is being read.@refill
1573 In addition, if a symbol-reading module creates psymtabs when
1574 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
1575 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
1576 from any point in the @value{GDBN} symbol-handling code.
1579 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
1581 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
1582 the psymtab has not already been read in and had its @code{pst->symtab}
1583 pointer set. The argument is the psymtab to be fleshed-out into a
1584 symtab. Upon return, @code{pst->readin} should have been set to 1, and
1585 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
1586 zero if there were no symbols in that part of the symbol file.
1589 @section Partial Symbol Tables
1591 @value{GDBN} has three types of symbol tables:
1594 @cindex full symbol table
1597 Full symbol tables (@dfn{symtabs}). These contain the main
1598 information about symbols and addresses.
1602 Partial symbol tables (@dfn{psymtabs}). These contain enough
1603 information to know when to read the corresponding part of the full
1606 @cindex minimal symbol table
1609 Minimal symbol tables (@dfn{msymtabs}). These contain information
1610 gleaned from non-debugging symbols.
1613 @cindex partial symbol table
1614 This section describes partial symbol tables.
1616 A psymtab is constructed by doing a very quick pass over an executable
1617 file's debugging information. Small amounts of information are
1618 extracted---enough to identify which parts of the symbol table will
1619 need to be re-read and fully digested later, when the user needs the
1620 information. The speed of this pass causes @value{GDBN} to start up very
1621 quickly. Later, as the detailed rereading occurs, it occurs in small
1622 pieces, at various times, and the delay therefrom is mostly invisible to
1624 @c (@xref{Symbol Reading}.)
1626 The symbols that show up in a file's psymtab should be, roughly, those
1627 visible to the debugger's user when the program is not running code from
1628 that file. These include external symbols and types, static symbols and
1629 types, and @code{enum} values declared at file scope.
1631 The psymtab also contains the range of instruction addresses that the
1632 full symbol table would represent.
1634 @cindex finding a symbol
1635 @cindex symbol lookup
1636 The idea is that there are only two ways for the user (or much of the
1637 code in the debugger) to reference a symbol:
1640 @findex find_pc_function
1641 @findex find_pc_line
1643 By its address (e.g. execution stops at some address which is inside a
1644 function in this file). The address will be noticed to be in the
1645 range of this psymtab, and the full symtab will be read in.
1646 @code{find_pc_function}, @code{find_pc_line}, and other
1647 @code{find_pc_@dots{}} functions handle this.
1649 @cindex lookup_symbol
1652 (e.g. the user asks to print a variable, or set a breakpoint on a
1653 function). Global names and file-scope names will be found in the
1654 psymtab, which will cause the symtab to be pulled in. Local names will
1655 have to be qualified by a global name, or a file-scope name, in which
1656 case we will have already read in the symtab as we evaluated the
1657 qualifier. Or, a local symbol can be referenced when we are ``in'' a
1658 local scope, in which case the first case applies. @code{lookup_symbol}
1659 does most of the work here.
1662 The only reason that psymtabs exist is to cause a symtab to be read in
1663 at the right moment. Any symbol that can be elided from a psymtab,
1664 while still causing that to happen, should not appear in it. Since
1665 psymtabs don't have the idea of scope, you can't put local symbols in
1666 them anyway. Psymtabs don't have the idea of the type of a symbol,
1667 either, so types need not appear, unless they will be referenced by
1670 It is a bug for @value{GDBN} to behave one way when only a psymtab has
1671 been read, and another way if the corresponding symtab has been read
1672 in. Such bugs are typically caused by a psymtab that does not contain
1673 all the visible symbols, or which has the wrong instruction address
1676 The psymtab for a particular section of a symbol file (objfile) could be
1677 thrown away after the symtab has been read in. The symtab should always
1678 be searched before the psymtab, so the psymtab will never be used (in a
1679 bug-free environment). Currently, psymtabs are allocated on an obstack,
1680 and all the psymbols themselves are allocated in a pair of large arrays
1681 on an obstack, so there is little to be gained by trying to free them
1682 unless you want to do a lot more work.
1686 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
1688 @cindex fundamental types
1689 These are the fundamental types that @value{GDBN} uses internally. Fundamental
1690 types from the various debugging formats (stabs, ELF, etc) are mapped
1691 into one of these. They are basically a union of all fundamental types
1692 that @value{GDBN} knows about for all the languages that @value{GDBN}
1695 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
1698 Each time @value{GDBN} builds an internal type, it marks it with one
1699 of these types. The type may be a fundamental type, such as
1700 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
1701 which is a pointer to another type. Typically, several @code{FT_*}
1702 types map to one @code{TYPE_CODE_*} type, and are distinguished by
1703 other members of the type struct, such as whether the type is signed
1704 or unsigned, and how many bits it uses.
1706 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
1708 These are instances of type structs that roughly correspond to
1709 fundamental types and are created as global types for @value{GDBN} to
1710 use for various ugly historical reasons. We eventually want to
1711 eliminate these. Note for example that @code{builtin_type_int}
1712 initialized in @file{gdbtypes.c} is basically the same as a
1713 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
1714 an @code{FT_INTEGER} fundamental type. The difference is that the
1715 @code{builtin_type} is not associated with any particular objfile, and
1716 only one instance exists, while @file{c-lang.c} builds as many
1717 @code{TYPE_CODE_INT} types as needed, with each one associated with
1718 some particular objfile.
1720 @section Object File Formats
1721 @cindex object file formats
1725 @cindex @code{a.out} format
1726 The @code{a.out} format is the original file format for Unix. It
1727 consists of three sections: @code{text}, @code{data}, and @code{bss},
1728 which are for program code, initialized data, and uninitialized data,
1731 The @code{a.out} format is so simple that it doesn't have any reserved
1732 place for debugging information. (Hey, the original Unix hackers used
1733 @samp{adb}, which is a machine-language debugger!) The only debugging
1734 format for @code{a.out} is stabs, which is encoded as a set of normal
1735 symbols with distinctive attributes.
1737 The basic @code{a.out} reader is in @file{dbxread.c}.
1742 The COFF format was introduced with System V Release 3 (SVR3) Unix.
1743 COFF files may have multiple sections, each prefixed by a header. The
1744 number of sections is limited.
1746 The COFF specification includes support for debugging. Although this
1747 was a step forward, the debugging information was woefully limited. For
1748 instance, it was not possible to represent code that came from an
1751 The COFF reader is in @file{coffread.c}.
1755 @cindex ECOFF format
1756 ECOFF is an extended COFF originally introduced for Mips and Alpha
1759 The basic ECOFF reader is in @file{mipsread.c}.
1763 @cindex XCOFF format
1764 The IBM RS/6000 running AIX uses an object file format called XCOFF.
1765 The COFF sections, symbols, and line numbers are used, but debugging
1766 symbols are @code{dbx}-style stabs whose strings are located in the
1767 @code{.debug} section (rather than the string table). For more
1768 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
1770 The shared library scheme has a clean interface for figuring out what
1771 shared libraries are in use, but the catch is that everything which
1772 refers to addresses (symbol tables and breakpoints at least) needs to be
1773 relocated for both shared libraries and the main executable. At least
1774 using the standard mechanism this can only be done once the program has
1775 been run (or the core file has been read).
1779 @cindex PE-COFF format
1780 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
1781 executables. PE is basically COFF with additional headers.
1783 While BFD includes special PE support, @value{GDBN} needs only the basic
1789 The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
1790 to COFF in being organized into a number of sections, but it removes
1791 many of COFF's limitations.
1793 The basic ELF reader is in @file{elfread.c}.
1798 SOM is HP's object file and debug format (not to be confused with IBM's
1799 SOM, which is a cross-language ABI).
1801 The SOM reader is in @file{hpread.c}.
1803 @subsection Other File Formats
1805 @cindex Netware Loadable Module format
1806 Other file formats that have been supported by @value{GDBN} include Netware
1807 Loadable Modules (@file{nlmread.c}).
1809 @section Debugging File Formats
1811 This section describes characteristics of debugging information that
1812 are independent of the object file format.
1816 @cindex stabs debugging info
1817 @code{stabs} started out as special symbols within the @code{a.out}
1818 format. Since then, it has been encapsulated into other file
1819 formats, such as COFF and ELF.
1821 While @file{dbxread.c} does some of the basic stab processing,
1822 including for encapsulated versions, @file{stabsread.c} does
1827 @cindex COFF debugging info
1828 The basic COFF definition includes debugging information. The level
1829 of support is minimal and non-extensible, and is not often used.
1831 @subsection Mips debug (Third Eye)
1833 @cindex ECOFF debugging info
1834 ECOFF includes a definition of a special debug format.
1836 The file @file{mdebugread.c} implements reading for this format.
1840 @cindex DWARF 1 debugging info
1841 DWARF 1 is a debugging format that was originally designed to be
1842 used with ELF in SVR4 systems.
1844 @c OBSOLETE CHILL_PRODUCER
1848 @c If defined, these are the producer strings in a DWARF 1 file. All of
1849 @c these have reasonable defaults already.
1851 The DWARF 1 reader is in @file{dwarfread.c}.
1855 @cindex DWARF 2 debugging info
1856 DWARF 2 is an improved but incompatible version of DWARF 1.
1858 The DWARF 2 reader is in @file{dwarf2read.c}.
1862 @cindex SOM debugging info
1863 Like COFF, the SOM definition includes debugging information.
1865 @section Adding a New Symbol Reader to @value{GDBN}
1867 @cindex adding debugging info reader
1868 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
1869 there is probably little to be done.
1871 If you need to add a new object file format, you must first add it to
1872 BFD. This is beyond the scope of this document.
1874 You must then arrange for the BFD code to provide access to the
1875 debugging symbols. Generally @value{GDBN} will have to call swapping routines
1876 from BFD and a few other BFD internal routines to locate the debugging
1877 information. As much as possible, @value{GDBN} should not depend on the BFD
1878 internal data structures.
1880 For some targets (e.g., COFF), there is a special transfer vector used
1881 to call swapping routines, since the external data structures on various
1882 platforms have different sizes and layouts. Specialized routines that
1883 will only ever be implemented by one object file format may be called
1884 directly. This interface should be described in a file
1885 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
1888 @node Language Support
1890 @chapter Language Support
1892 @cindex language support
1893 @value{GDBN}'s language support is mainly driven by the symbol reader,
1894 although it is possible for the user to set the source language
1897 @value{GDBN} chooses the source language by looking at the extension
1898 of the file recorded in the debug info; @file{.c} means C, @file{.f}
1899 means Fortran, etc. It may also use a special-purpose language
1900 identifier if the debug format supports it, like with DWARF.
1902 @section Adding a Source Language to @value{GDBN}
1904 @cindex adding source language
1905 To add other languages to @value{GDBN}'s expression parser, follow the
1909 @item Create the expression parser.
1911 @cindex expression parser
1912 This should reside in a file @file{@var{lang}-exp.y}. Routines for
1913 building parsed expressions into a @code{union exp_element} list are in
1916 @cindex language parser
1917 Since we can't depend upon everyone having Bison, and YACC produces
1918 parsers that define a bunch of global names, the following lines
1919 @strong{must} be included at the top of the YACC parser, to prevent the
1920 various parsers from defining the same global names:
1923 #define yyparse @var{lang}_parse
1924 #define yylex @var{lang}_lex
1925 #define yyerror @var{lang}_error
1926 #define yylval @var{lang}_lval
1927 #define yychar @var{lang}_char
1928 #define yydebug @var{lang}_debug
1929 #define yypact @var{lang}_pact
1930 #define yyr1 @var{lang}_r1
1931 #define yyr2 @var{lang}_r2
1932 #define yydef @var{lang}_def
1933 #define yychk @var{lang}_chk
1934 #define yypgo @var{lang}_pgo
1935 #define yyact @var{lang}_act
1936 #define yyexca @var{lang}_exca
1937 #define yyerrflag @var{lang}_errflag
1938 #define yynerrs @var{lang}_nerrs
1941 At the bottom of your parser, define a @code{struct language_defn} and
1942 initialize it with the right values for your language. Define an
1943 @code{initialize_@var{lang}} routine and have it call
1944 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
1945 that your language exists. You'll need some other supporting variables
1946 and functions, which will be used via pointers from your
1947 @code{@var{lang}_language_defn}. See the declaration of @code{struct
1948 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
1949 for more information.
1951 @item Add any evaluation routines, if necessary
1953 @cindex expression evaluation routines
1954 @findex evaluate_subexp
1955 @findex prefixify_subexp
1956 @findex length_of_subexp
1957 If you need new opcodes (that represent the operations of the language),
1958 add them to the enumerated type in @file{expression.h}. Add support
1959 code for these operations in the @code{evaluate_subexp} function
1960 defined in the file @file{eval.c}. Add cases
1961 for new opcodes in two functions from @file{parse.c}:
1962 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
1963 the number of @code{exp_element}s that a given operation takes up.
1965 @item Update some existing code
1967 Add an enumerated identifier for your language to the enumerated type
1968 @code{enum language} in @file{defs.h}.
1970 Update the routines in @file{language.c} so your language is included.
1971 These routines include type predicates and such, which (in some cases)
1972 are language dependent. If your language does not appear in the switch
1973 statement, an error is reported.
1975 @vindex current_language
1976 Also included in @file{language.c} is the code that updates the variable
1977 @code{current_language}, and the routines that translate the
1978 @code{language_@var{lang}} enumerated identifier into a printable
1981 @findex _initialize_language
1982 Update the function @code{_initialize_language} to include your
1983 language. This function picks the default language upon startup, so is
1984 dependent upon which languages that @value{GDBN} is built for.
1986 @findex allocate_symtab
1987 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
1988 code so that the language of each symtab (source file) is set properly.
1989 This is used to determine the language to use at each stack frame level.
1990 Currently, the language is set based upon the extension of the source
1991 file. If the language can be better inferred from the symbol
1992 information, please set the language of the symtab in the symbol-reading
1995 @findex print_subexp
1996 @findex op_print_tab
1997 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
1998 expression opcodes you have added to @file{expression.h}. Also, add the
1999 printed representations of your operators to @code{op_print_tab}.
2001 @item Add a place of call
2004 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2005 @code{parse_exp_1} (defined in @file{parse.c}).
2007 @item Use macros to trim code
2009 @cindex trimming language-dependent code
2010 The user has the option of building @value{GDBN} for some or all of the
2011 languages. If the user decides to build @value{GDBN} for the language
2012 @var{lang}, then every file dependent on @file{language.h} will have the
2013 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2014 leave out large routines that the user won't need if he or she is not
2015 using your language.
2017 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2018 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2019 compiled form of your parser) is not linked into @value{GDBN} at all.
2021 See the file @file{configure.in} for how @value{GDBN} is configured
2022 for different languages.
2024 @item Edit @file{Makefile.in}
2026 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2027 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2028 not get linked in, or, worse yet, it may not get @code{tar}red into the
2033 @node Host Definition
2035 @chapter Host Definition
2037 With the advent of Autoconf, it's rarely necessary to have host
2038 definition machinery anymore. The following information is provided,
2039 mainly, as an historical reference.
2041 @section Adding a New Host
2043 @cindex adding a new host
2044 @cindex host, adding
2045 @value{GDBN}'s host configuration support normally happens via Autoconf.
2046 New host-specific definitions should not be needed. Older hosts
2047 @value{GDBN} still use the host-specific definitions and files listed
2048 below, but these mostly exist for historical reasons, and will
2049 eventually disappear.
2052 @item gdb/config/@var{arch}/@var{xyz}.mh
2053 This file once contained both host and native configuration information
2054 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2055 configuration information is now handed by Autoconf.
2057 Host configuration information included a definition of
2058 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2059 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2060 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2062 New host only configurations do not need this file.
2064 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2065 This file once contained definitions and includes required when hosting
2066 gdb on machine @var{xyz}. Those definitions and includes are now
2067 handled by Autoconf.
2069 New host and native configurations do not need this file.
2071 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2072 file to define the macros @var{HOST_FLOAT_FORMAT},
2073 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2074 also needs to be replaced with either an Autoconf or run-time test.}
2078 @subheading Generic Host Support Files
2080 @cindex generic host support
2081 There are some ``generic'' versions of routines that can be used by
2082 various systems. These can be customized in various ways by macros
2083 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2084 the @var{xyz} host, you can just include the generic file's name (with
2085 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2087 Otherwise, if your machine needs custom support routines, you will need
2088 to write routines that perform the same functions as the generic file.
2089 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2090 into @code{XDEPFILES}.
2093 @cindex remote debugging support
2094 @cindex serial line support
2096 This contains serial line support for Unix systems. This is always
2097 included, via the makefile variable @code{SER_HARDWIRE}; override this
2098 variable in the @file{.mh} file to avoid it.
2101 This contains serial line support for 32-bit programs running under DOS,
2102 using the DJGPP (a.k.a.@: GO32) execution environment.
2104 @cindex TCP remote support
2106 This contains generic TCP support using sockets.
2109 @section Host Conditionals
2111 When @value{GDBN} is configured and compiled, various macros are
2112 defined or left undefined, to control compilation based on the
2113 attributes of the host system. These macros and their meanings (or if
2114 the meaning is not documented here, then one of the source files where
2115 they are used is indicated) are:
2118 @item @value{GDBN}INIT_FILENAME
2119 The default name of @value{GDBN}'s initialization file (normally
2123 This macro is deprecated.
2126 Define this if your system does not have a @code{<sys/file.h>}.
2128 @item SIGWINCH_HANDLER
2129 If your host defines @code{SIGWINCH}, you can define this to be the name
2130 of a function to be called if @code{SIGWINCH} is received.
2132 @item SIGWINCH_HANDLER_BODY
2133 Define this to expand into code that will define the function named by
2134 the expansion of @code{SIGWINCH_HANDLER}.
2136 @item ALIGN_STACK_ON_STARTUP
2137 @cindex stack alignment
2138 Define this if your system is of a sort that will crash in
2139 @code{tgetent} if the stack happens not to be longword-aligned when
2140 @code{main} is called. This is a rare situation, but is known to occur
2141 on several different types of systems.
2143 @item CRLF_SOURCE_FILES
2144 @cindex DOS text files
2145 Define this if host files use @code{\r\n} rather than @code{\n} as a
2146 line terminator. This will cause source file listings to omit @code{\r}
2147 characters when printing and it will allow @code{\r\n} line endings of files
2148 which are ``sourced'' by gdb. It must be possible to open files in binary
2149 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2151 @item DEFAULT_PROMPT
2153 The default value of the prompt string (normally @code{"(gdb) "}).
2156 @cindex terminal device
2157 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2159 @item FCLOSE_PROVIDED
2160 Define this if the system declares @code{fclose} in the headers included
2161 in @code{defs.h}. This isn't needed unless your compiler is unusually
2165 Define this if binary files are opened the same way as text files.
2167 @item GETENV_PROVIDED
2168 Define this if the system declares @code{getenv} in its headers included
2169 in @code{defs.h}. This isn't needed unless your compiler is unusually
2174 In some cases, use the system call @code{mmap} for reading symbol
2175 tables. For some machines this allows for sharing and quick updates.
2178 Define this if the host system has @code{termio.h}.
2185 Values for host-side constants.
2188 Substitute for isatty, if not available.
2191 This is the longest integer type available on the host. If not defined,
2192 it will default to @code{long long} or @code{long}, depending on
2193 @code{CC_HAS_LONG_LONG}.
2195 @item CC_HAS_LONG_LONG
2196 @cindex @code{long long} data type
2197 Define this if the host C compiler supports @code{long long}. This is set
2198 by the @code{configure} script.
2200 @item PRINTF_HAS_LONG_LONG
2201 Define this if the host can handle printing of long long integers via
2202 the printf format conversion specifier @code{ll}. This is set by the
2203 @code{configure} script.
2205 @item HAVE_LONG_DOUBLE
2206 Define this if the host C compiler supports @code{long double}. This is
2207 set by the @code{configure} script.
2209 @item PRINTF_HAS_LONG_DOUBLE
2210 Define this if the host can handle printing of long double float-point
2211 numbers via the printf format conversion specifier @code{Lg}. This is
2212 set by the @code{configure} script.
2214 @item SCANF_HAS_LONG_DOUBLE
2215 Define this if the host can handle the parsing of long double
2216 float-point numbers via the scanf format conversion specifier
2217 @code{Lg}. This is set by the @code{configure} script.
2219 @item LSEEK_NOT_LINEAR
2220 Define this if @code{lseek (n)} does not necessarily move to byte number
2221 @code{n} in the file. This is only used when reading source files. It
2222 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2225 This macro is used as the argument to @code{lseek} (or, most commonly,
2226 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2227 which is the POSIX equivalent.
2229 @item MMAP_BASE_ADDRESS
2230 When using HAVE_MMAP, the first mapping should go at this address.
2232 @item MMAP_INCREMENT
2233 when using HAVE_MMAP, this is the increment between mappings.
2236 If defined, this should be one or more tokens, such as @code{volatile},
2237 that can be used in both the declaration and definition of functions to
2238 indicate that they never return. The default is already set correctly
2239 if compiling with GCC. This will almost never need to be defined.
2242 If defined, this should be one or more tokens, such as
2243 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2244 of functions to indicate that they never return. The default is already
2245 set correctly if compiling with GCC. This will almost never need to be
2248 @item USE_GENERIC_DUMMY_FRAMES
2249 @cindex generic dummy frames
2250 Define this to 1 if the target is using the generic inferior function
2251 call code. See @code{blockframe.c} for more information.
2255 @value{GDBN} will use the @code{mmalloc} library for memory allocation
2256 for symbol reading if this symbol is defined. Be careful defining it
2257 since there are systems on which @code{mmalloc} does not work for some
2258 reason. One example is the DECstation, where its RPC library can't
2259 cope with our redefinition of @code{malloc} to call @code{mmalloc}.
2260 When defining @code{USE_MMALLOC}, you will also have to set
2261 @code{MMALLOC} in the Makefile, to point to the @code{mmalloc} library. This
2262 define is set when you configure with @samp{--with-mmalloc}.
2266 Define this if you are using @code{mmalloc}, but don't want the overhead
2267 of checking the heap with @code{mmcheck}. Note that on some systems,
2268 the C runtime makes calls to @code{malloc} prior to calling @code{main}, and if
2269 @code{free} is ever called with these pointers after calling
2270 @code{mmcheck} to enable checking, a memory corruption abort is certain
2271 to occur. These systems can still use @code{mmalloc}, but must define
2275 Define this to 1 if the C runtime allocates memory prior to
2276 @code{mmcheck} being called, but that memory is never freed so we don't
2277 have to worry about it triggering a memory corruption abort. The
2278 default is 0, which means that @code{mmcheck} will only install the heap
2279 checking functions if there has not yet been any memory allocation
2280 calls, and if it fails to install the functions, @value{GDBN} will issue a
2281 warning. This is currently defined if you configure using
2282 @samp{--with-mmalloc}.
2284 @item NO_SIGINTERRUPT
2285 @findex siginterrupt
2286 Define this to indicate that @code{siginterrupt} is not available.
2290 Define these to appropriate value for the system @code{lseek}, if not already
2294 This is the signal for stopping @value{GDBN}. Defaults to
2295 @code{SIGTSTP}. (Only redefined for the Convex.)
2298 Define this if the interior's tty should be opened with the @code{O_NOCTTY}
2299 flag. (FIXME: This should be a native-only flag, but @file{inflow.c} is
2303 Means that System V (prior to SVR4) include files are in use. (FIXME:
2304 This symbol is abused in @file{infrun.c}, @file{regex.c},
2305 @file{remote-nindy.c}, and @file{utils.c} for other things, at the
2309 Define this to help placate @code{lint} in some situations.
2312 Define this to override the defaults of @code{__volatile__} or
2317 @node Target Architecture Definition
2319 @chapter Target Architecture Definition
2321 @cindex target architecture definition
2322 @value{GDBN}'s target architecture defines what sort of
2323 machine-language programs @value{GDBN} can work with, and how it works
2326 The target architecture object is implemented as the C structure
2327 @code{struct gdbarch *}. The structure, and its methods, are generated
2328 using the Bourne shell script @file{gdbarch.sh}.
2330 @section Operating System ABI Variant Handling
2331 @cindex OS ABI variants
2333 @value{GDBN} provides a mechanism for handling variations in OS
2334 ABIs. An OS ABI variant may have influence over any number of
2335 variables in the target architecture definition. There are two major
2336 components in the OS ABI mechanism: sniffers and handlers.
2338 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2339 (the architecture may be wildcarded) in an attempt to determine the
2340 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2341 to be @dfn{generic}, while sniffers for a specific architecture are
2342 considered to be @dfn{specific}. A match from a specific sniffer
2343 overrides a match from a generic sniffer. Multiple sniffers for an
2344 architecture/flavour may exist, in order to differentiate between two
2345 different operating systems which use the same basic file format. The
2346 OS ABI framework provides a generic sniffer for ELF-format files which
2347 examines the @code{EI_OSABI} field of the ELF header, as well as note
2348 sections known to be used by several operating systems.
2350 @cindex fine-tuning @code{gdbarch} structure
2351 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2352 selected OS ABI. There may be only one handler for a given OS ABI
2353 for each BFD architecture.
2355 The following OS ABI variants are defined in @file{osabi.h}:
2359 @findex GDB_OSABI_UNKNOWN
2360 @item GDB_OSABI_UNKNOWN
2361 The ABI of the inferior is unknown. The default @code{gdbarch}
2362 settings for the architecture will be used.
2364 @findex GDB_OSABI_SVR4
2365 @item GDB_OSABI_SVR4
2366 UNIX System V Release 4
2368 @findex GDB_OSABI_HURD
2369 @item GDB_OSABI_HURD
2370 GNU using the Hurd kernel
2372 @findex GDB_OSABI_SOLARIS
2373 @item GDB_OSABI_SOLARIS
2376 @findex GDB_OSABI_OSF1
2377 @item GDB_OSABI_OSF1
2378 OSF/1, including Digital UNIX and Compaq Tru64 UNIX
2380 @findex GDB_OSABI_LINUX
2381 @item GDB_OSABI_LINUX
2382 GNU using the Linux kernel
2384 @findex GDB_OSABI_FREEBSD_AOUT
2385 @item GDB_OSABI_FREEBSD_AOUT
2386 FreeBSD using the a.out executable format
2388 @findex GDB_OSABI_FREEBSD_ELF
2389 @item GDB_OSABI_FREEBSD_ELF
2390 FreeBSD using the ELF executable format
2392 @findex GDB_OSABI_NETBSD_AOUT
2393 @item GDB_OSABI_NETBSD_AOUT
2394 NetBSD using the a.out executable format
2396 @findex GDB_OSABI_NETBSD_ELF
2397 @item GDB_OSABI_NETBSD_ELF
2398 NetBSD using the ELF executable format
2400 @findex GDB_OSABI_WINCE
2401 @item GDB_OSABI_WINCE
2404 @findex GDB_OSABI_GO32
2405 @item GDB_OSABI_GO32
2408 @findex GDB_OSABI_NETWARE
2409 @item GDB_OSABI_NETWARE
2412 @findex GDB_OSABI_ARM_EABI_V1
2413 @item GDB_OSABI_ARM_EABI_V1
2414 ARM Embedded ABI version 1
2416 @findex GDB_OSABI_ARM_EABI_V2
2417 @item GDB_OSABI_ARM_EABI_V2
2418 ARM Embedded ABI version 2
2420 @findex GDB_OSABI_ARM_APCS
2421 @item GDB_OSABI_ARM_APCS
2422 Generic ARM Procedure Call Standard
2426 Here are the functions that make up the OS ABI framework:
2428 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2429 Return the name of the OS ABI corresponding to @var{osabi}.
2432 @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}))
2433 Register the OS ABI handler specified by @var{init_osabi} for the
2434 architecture/OS ABI pair specified by @var{arch} and @var{osabi}.
2437 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2438 Register the OS ABI file sniffer specified by @var{sniffer} for the
2439 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2440 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2441 be generic, and is allowed to examine @var{flavour}-flavoured files for
2445 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2446 Examine the file described by @var{abfd} to determine its OS ABI.
2447 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2451 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2452 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2453 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2454 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2455 architecture, a warning will be issued and the debugging session will continue
2456 with the defaults already established for @var{gdbarch}.
2459 @section Registers and Memory
2461 @value{GDBN}'s model of the target machine is rather simple.
2462 @value{GDBN} assumes the machine includes a bank of registers and a
2463 block of memory. Each register may have a different size.
2465 @value{GDBN} does not have a magical way to match up with the
2466 compiler's idea of which registers are which; however, it is critical
2467 that they do match up accurately. The only way to make this work is
2468 to get accurate information about the order that the compiler uses,
2469 and to reflect that in the @code{REGISTER_NAME} and related macros.
2471 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2473 @section Pointers Are Not Always Addresses
2474 @cindex pointer representation
2475 @cindex address representation
2476 @cindex word-addressed machines
2477 @cindex separate data and code address spaces
2478 @cindex spaces, separate data and code address
2479 @cindex address spaces, separate data and code
2480 @cindex code pointers, word-addressed
2481 @cindex converting between pointers and addresses
2482 @cindex D10V addresses
2484 On almost all 32-bit architectures, the representation of a pointer is
2485 indistinguishable from the representation of some fixed-length number
2486 whose value is the byte address of the object pointed to. On such
2487 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2488 However, architectures with smaller word sizes are often cramped for
2489 address space, so they may choose a pointer representation that breaks this
2490 identity, and allows a larger code address space.
2492 For example, the Mitsubishi D10V is a 16-bit VLIW processor whose
2493 instructions are 32 bits long@footnote{Some D10V instructions are
2494 actually pairs of 16-bit sub-instructions. However, since you can't
2495 jump into the middle of such a pair, code addresses can only refer to
2496 full 32 bit instructions, which is what matters in this explanation.}.
2497 If the D10V used ordinary byte addresses to refer to code locations,
2498 then the processor would only be able to address 64kb of instructions.
2499 However, since instructions must be aligned on four-byte boundaries, the
2500 low two bits of any valid instruction's byte address are always
2501 zero---byte addresses waste two bits. So instead of byte addresses,
2502 the D10V uses word addresses---byte addresses shifted right two bits---to
2503 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2506 However, this means that code pointers and data pointers have different
2507 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2508 @code{0xC020} when used as a data address, but refers to byte address
2509 @code{0x30080} when used as a code address.
2511 (The D10V also uses separate code and data address spaces, which also
2512 affects the correspondence between pointers and addresses, but we're
2513 going to ignore that here; this example is already too long.)
2515 To cope with architectures like this---the D10V is not the only
2516 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2517 byte numbers, and @dfn{pointers}, which are the target's representation
2518 of an address of a particular type of data. In the example above,
2519 @code{0xC020} is the pointer, which refers to one of the addresses
2520 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2521 @value{GDBN} provides functions for turning a pointer into an address
2522 and vice versa, in the appropriate way for the current architecture.
2524 Unfortunately, since addresses and pointers are identical on almost all
2525 processors, this distinction tends to bit-rot pretty quickly. Thus,
2526 each time you port @value{GDBN} to an architecture which does
2527 distinguish between pointers and addresses, you'll probably need to
2528 clean up some architecture-independent code.
2530 Here are functions which convert between pointers and addresses:
2532 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2533 Treat the bytes at @var{buf} as a pointer or reference of type
2534 @var{type}, and return the address it represents, in a manner
2535 appropriate for the current architecture. This yields an address
2536 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2537 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2540 For example, if the current architecture is the Intel x86, this function
2541 extracts a little-endian integer of the appropriate length from
2542 @var{buf} and returns it. However, if the current architecture is the
2543 D10V, this function will return a 16-bit integer extracted from
2544 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2546 If @var{type} is not a pointer or reference type, then this function
2547 will signal an internal error.
2550 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2551 Store the address @var{addr} in @var{buf}, in the proper format for a
2552 pointer of type @var{type} in the current architecture. Note that
2553 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2556 For example, if the current architecture is the Intel x86, this function
2557 stores @var{addr} unmodified as a little-endian integer of the
2558 appropriate length in @var{buf}. However, if the current architecture
2559 is the D10V, this function divides @var{addr} by four if @var{type} is
2560 a pointer to a function, and then stores it in @var{buf}.
2562 If @var{type} is not a pointer or reference type, then this function
2563 will signal an internal error.
2566 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2567 Assuming that @var{val} is a pointer, return the address it represents,
2568 as appropriate for the current architecture.
2570 This function actually works on integral values, as well as pointers.
2571 For pointers, it performs architecture-specific conversions as
2572 described above for @code{extract_typed_address}.
2575 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2576 Create and return a value representing a pointer of type @var{type} to
2577 the address @var{addr}, as appropriate for the current architecture.
2578 This function performs architecture-specific conversions as described
2579 above for @code{store_typed_address}.
2583 @value{GDBN} also provides functions that do the same tasks, but assume
2584 that pointers are simply byte addresses; they aren't sensitive to the
2585 current architecture, beyond knowing the appropriate endianness.
2587 @deftypefun CORE_ADDR extract_address (void *@var{addr}, int len)
2588 Extract a @var{len}-byte number from @var{addr} in the appropriate
2589 endianness for the current architecture, and return it. Note that
2590 @var{addr} refers to @value{GDBN}'s memory, not the inferior's.
2592 This function should only be used in architecture-specific code; it
2593 doesn't have enough information to turn bits into a true address in the
2594 appropriate way for the current architecture. If you can, use
2595 @code{extract_typed_address} instead.
2598 @deftypefun void store_address (void *@var{addr}, int @var{len}, LONGEST @var{val})
2599 Store @var{val} at @var{addr} as a @var{len}-byte integer, in the
2600 appropriate endianness for the current architecture. Note that
2601 @var{addr} refers to a buffer in @value{GDBN}'s memory, not the
2604 This function should only be used in architecture-specific code; it
2605 doesn't have enough information to turn a true address into bits in the
2606 appropriate way for the current architecture. If you can, use
2607 @code{store_typed_address} instead.
2611 Here are some macros which architectures can define to indicate the
2612 relationship between pointers and addresses. These have default
2613 definitions, appropriate for architectures on which all pointers are
2614 simple unsigned byte addresses.
2616 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2617 Assume that @var{buf} holds a pointer of type @var{type}, in the
2618 appropriate format for the current architecture. Return the byte
2619 address the pointer refers to.
2621 This function may safely assume that @var{type} is either a pointer or a
2622 C@t{++} reference type.
2625 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2626 Store in @var{buf} a pointer of type @var{type} representing the address
2627 @var{addr}, in the appropriate format for the current architecture.
2629 This function may safely assume that @var{type} is either a pointer or a
2630 C@t{++} reference type.
2633 @section Address Classes
2634 @cindex address classes
2635 @cindex DW_AT_byte_size
2636 @cindex DW_AT_address_class
2638 Sometimes information about different kinds of addresses is available
2639 via the debug information. For example, some programming environments
2640 define addresses of several different sizes. If the debug information
2641 distinguishes these kinds of address classes through either the size
2642 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2643 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2644 following macros should be defined in order to disambiguate these
2645 types within @value{GDBN} as well as provide the added information to
2646 a @value{GDBN} user when printing type expressions.
2648 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2649 Returns the type flags needed to construct a pointer type whose size
2650 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2651 This function is normally called from within a symbol reader. See
2652 @file{dwarf2read.c}.
2655 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2656 Given the type flags representing an address class qualifier, return
2659 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2660 Given an address qualifier name, set the @code{int} refererenced by @var{type_flags_ptr} to the type flags
2661 for that address class qualifier.
2664 Since the need for address classes is rather rare, none of
2665 the address class macros defined by default. Predicate
2666 macros are provided to detect when they are defined.
2668 Consider a hypothetical architecture in which addresses are normally
2669 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2670 suppose that the @w{DWARF 2} information for this architecture simply
2671 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2672 of these "short" pointers. The following functions could be defined
2673 to implement the address class macros:
2676 somearch_address_class_type_flags (int byte_size,
2677 int dwarf2_addr_class)
2680 return TYPE_FLAG_ADDRESS_CLASS_1;
2686 somearch_address_class_type_flags_to_name (int type_flags)
2688 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
2695 somearch_address_class_name_to_type_flags (char *name,
2696 int *type_flags_ptr)
2698 if (strcmp (name, "short") == 0)
2700 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
2708 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
2709 to indicate the presence of one of these "short" pointers. E.g, if
2710 the debug information indicates that @code{short_ptr_var} is one of these
2711 short pointers, @value{GDBN} might show the following behavior:
2714 (gdb) ptype short_ptr_var
2715 type = int * @@short
2719 @section Raw and Virtual Register Representations
2720 @cindex raw register representation
2721 @cindex virtual register representation
2722 @cindex representations, raw and virtual registers
2724 @emph{Maintainer note: This section is pretty much obsolete. The
2725 functionality described here has largely been replaced by
2726 pseudo-registers and the mechanisms described in @ref{Target
2727 Architecture Definition, , Using Different Register and Memory Data
2728 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
2729 Bug Tracking Database} and
2730 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
2731 up-to-date information.}
2733 Some architectures use one representation for a value when it lives in a
2734 register, but use a different representation when it lives in memory.
2735 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
2736 the target registers, and the @dfn{virtual} representation is the one
2737 used in memory, and within @value{GDBN} @code{struct value} objects.
2739 @emph{Maintainer note: Notice that the same mechanism is being used to
2740 both convert a register to a @code{struct value} and alternative
2743 For almost all data types on almost all architectures, the virtual and
2744 raw representations are identical, and no special handling is needed.
2745 However, they do occasionally differ. For example:
2749 The x86 architecture supports an 80-bit @code{long double} type. However, when
2750 we store those values in memory, they occupy twelve bytes: the
2751 floating-point number occupies the first ten, and the final two bytes
2752 are unused. This keeps the values aligned on four-byte boundaries,
2753 allowing more efficient access. Thus, the x86 80-bit floating-point
2754 type is the raw representation, and the twelve-byte loosely-packed
2755 arrangement is the virtual representation.
2758 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
2759 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
2760 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
2761 raw representation, and the trimmed 32-bit representation is the
2762 virtual representation.
2765 In general, the raw representation is determined by the architecture, or
2766 @value{GDBN}'s interface to the architecture, while the virtual representation
2767 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
2768 @code{registers}, holds the register contents in raw format, and the
2769 @value{GDBN} remote protocol transmits register values in raw format.
2771 Your architecture may define the following macros to request
2772 conversions between the raw and virtual format:
2774 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
2775 Return non-zero if register number @var{reg}'s value needs different raw
2776 and virtual formats.
2778 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
2779 unless this macro returns a non-zero value for that register.
2782 @deftypefn {Target Macro} int REGISTER_RAW_SIZE (int @var{reg})
2783 The size of register number @var{reg}'s raw value. This is the number
2784 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
2785 remote protocol packet.
2788 @deftypefn {Target Macro} int REGISTER_VIRTUAL_SIZE (int @var{reg})
2789 The size of register number @var{reg}'s value, in its virtual format.
2790 This is the size a @code{struct value}'s buffer will have, holding that
2794 @deftypefn {Target Macro} struct type *REGISTER_VIRTUAL_TYPE (int @var{reg})
2795 This is the type of the virtual representation of register number
2796 @var{reg}. Note that there is no need for a macro giving a type for the
2797 register's raw form; once the register's value has been obtained, @value{GDBN}
2798 always uses the virtual form.
2801 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2802 Convert the value of register number @var{reg} to @var{type}, which
2803 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2804 at @var{from} holds the register's value in raw format; the macro should
2805 convert the value to virtual format, and place it at @var{to}.
2807 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
2808 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
2809 arguments in different orders.
2811 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
2812 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
2816 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2817 Convert the value of register number @var{reg} to @var{type}, which
2818 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2819 at @var{from} holds the register's value in raw format; the macro should
2820 convert the value to virtual format, and place it at @var{to}.
2822 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
2823 their @var{reg} and @var{type} arguments in different orders.
2827 @section Using Different Register and Memory Data Representations
2828 @cindex register representation
2829 @cindex memory representation
2830 @cindex representations, register and memory
2831 @cindex register data formats, converting
2832 @cindex @code{struct value}, converting register contents to
2834 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
2835 significant change. Many of the macros and functions refered to in this
2836 section are likely to be subject to further revision. See
2837 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
2838 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
2839 further information. cagney/2002-05-06.}
2841 Some architectures can represent a data object in a register using a
2842 form that is different to the objects more normal memory representation.
2848 The Alpha architecture can represent 32 bit integer values in
2849 floating-point registers.
2852 The x86 architecture supports 80-bit floating-point registers. The
2853 @code{long double} data type occupies 96 bits in memory but only 80 bits
2854 when stored in a register.
2858 In general, the register representation of a data type is determined by
2859 the architecture, or @value{GDBN}'s interface to the architecture, while
2860 the memory representation is determined by the Application Binary
2863 For almost all data types on almost all architectures, the two
2864 representations are identical, and no special handling is needed.
2865 However, they do occasionally differ. Your architecture may define the
2866 following macros to request conversions between the register and memory
2867 representations of a data type:
2869 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
2870 Return non-zero if the representation of a data value stored in this
2871 register may be different to the representation of that same data value
2872 when stored in memory.
2874 When non-zero, the macros @code{REGISTER_TO_VALUE} and
2875 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
2878 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2879 Convert the value of register number @var{reg} to a data object of type
2880 @var{type}. The buffer at @var{from} holds the register's value in raw
2881 format; the converted value should be placed in the buffer at @var{to}.
2883 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2884 their @var{reg} and @var{type} arguments in different orders.
2886 You should only use @code{REGISTER_TO_VALUE} with registers for which
2887 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2890 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2891 Convert a data value of type @var{type} to register number @var{reg}'
2894 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2895 their @var{reg} and @var{type} arguments in different orders.
2897 You should only use @code{VALUE_TO_REGISTER} with registers for which
2898 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2901 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
2902 See @file{mips-tdep.c}. It does not do what you want.
2906 @section Frame Interpretation
2908 @section Inferior Call Setup
2910 @section Compiler Characteristics
2912 @section Target Conditionals
2914 This section describes the macros that you can use to define the target
2919 @item ADDITIONAL_OPTIONS
2920 @itemx ADDITIONAL_OPTION_CASES
2921 @itemx ADDITIONAL_OPTION_HANDLER
2922 @itemx ADDITIONAL_OPTION_HELP
2923 @findex ADDITIONAL_OPTION_HELP
2924 @findex ADDITIONAL_OPTION_HANDLER
2925 @findex ADDITIONAL_OPTION_CASES
2926 @findex ADDITIONAL_OPTIONS
2927 These are a set of macros that allow the addition of additional command
2928 line options to @value{GDBN}. They are currently used only for the unsupported
2929 i960 Nindy target, and should not be used in any other configuration.
2931 @item ADDR_BITS_REMOVE (addr)
2932 @findex ADDR_BITS_REMOVE
2933 If a raw machine instruction address includes any bits that are not
2934 really part of the address, then define this macro to expand into an
2935 expression that zeroes those bits in @var{addr}. This is only used for
2936 addresses of instructions, and even then not in all contexts.
2938 For example, the two low-order bits of the PC on the Hewlett-Packard PA
2939 2.0 architecture contain the privilege level of the corresponding
2940 instruction. Since instructions must always be aligned on four-byte
2941 boundaries, the processor masks out these bits to generate the actual
2942 address of the instruction. ADDR_BITS_REMOVE should filter out these
2943 bits with an expression such as @code{((addr) & ~3)}.
2945 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
2946 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
2947 If @var{name} is a valid address class qualifier name, set the @code{int}
2948 referenced by @var{type_flags_ptr} to the mask representing the qualifier
2949 and return 1. If @var{name} is not a valid address class qualifier name,
2952 The value for @var{type_flags_ptr} should be one of
2953 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
2954 possibly some combination of these values or'd together.
2955 @xref{Target Architecture Definition, , Address Classes}.
2957 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
2958 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
2959 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
2962 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2963 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2964 Given a pointers byte size (as described by the debug information) and
2965 the possible @code{DW_AT_address_class} value, return the type flags
2966 used by @value{GDBN} to represent this address class. The value
2967 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
2968 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
2969 values or'd together.
2970 @xref{Target Architecture Definition, , Address Classes}.
2972 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
2973 @findex ADDRESS_CLASS_TYPE_FLAGS_P
2974 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
2977 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
2978 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
2979 Return the name of the address class qualifier associated with the type
2980 flags given by @var{type_flags}.
2982 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
2983 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
2984 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
2986 @xref{Target Architecture Definition, , Address Classes}.
2988 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
2989 @findex ADDRESS_TO_POINTER
2990 Store in @var{buf} a pointer of type @var{type} representing the address
2991 @var{addr}, in the appropriate format for the current architecture.
2992 This macro may safely assume that @var{type} is either a pointer or a
2993 C@t{++} reference type.
2994 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
2996 @item BEFORE_MAIN_LOOP_HOOK
2997 @findex BEFORE_MAIN_LOOP_HOOK
2998 Define this to expand into any code that you want to execute before the
2999 main loop starts. Although this is not, strictly speaking, a target
3000 conditional, that is how it is currently being used. Note that if a
3001 configuration were to define it one way for a host and a different way
3002 for the target, @value{GDBN} will probably not compile, let alone run
3003 correctly. This macro is currently used only for the unsupported i960 Nindy
3004 target, and should not be used in any other configuration.
3006 @item BELIEVE_PCC_PROMOTION
3007 @findex BELIEVE_PCC_PROMOTION
3008 Define if the compiler promotes a @code{short} or @code{char}
3009 parameter to an @code{int}, but still reports the parameter as its
3010 original type, rather than the promoted type.
3012 @item BELIEVE_PCC_PROMOTION_TYPE
3013 @findex BELIEVE_PCC_PROMOTION_TYPE
3014 Define this if @value{GDBN} should believe the type of a @code{short}
3015 argument when compiled by @code{pcc}, but look within a full int space to get
3016 its value. Only defined for Sun-3 at present.
3018 @item BITS_BIG_ENDIAN
3019 @findex BITS_BIG_ENDIAN
3020 Define this if the numbering of bits in the targets does @strong{not} match the
3021 endianness of the target byte order. A value of 1 means that the bits
3022 are numbered in a big-endian bit order, 0 means little-endian.
3026 This is the character array initializer for the bit pattern to put into
3027 memory where a breakpoint is set. Although it's common to use a trap
3028 instruction for a breakpoint, it's not required; for instance, the bit
3029 pattern could be an invalid instruction. The breakpoint must be no
3030 longer than the shortest instruction of the architecture.
3032 @code{BREAKPOINT} has been deprecated in favor of
3033 @code{BREAKPOINT_FROM_PC}.
3035 @item BIG_BREAKPOINT
3036 @itemx LITTLE_BREAKPOINT
3037 @findex LITTLE_BREAKPOINT
3038 @findex BIG_BREAKPOINT
3039 Similar to BREAKPOINT, but used for bi-endian targets.
3041 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3042 favor of @code{BREAKPOINT_FROM_PC}.
3044 @item REMOTE_BREAKPOINT
3045 @itemx LITTLE_REMOTE_BREAKPOINT
3046 @itemx BIG_REMOTE_BREAKPOINT
3047 @findex BIG_REMOTE_BREAKPOINT
3048 @findex LITTLE_REMOTE_BREAKPOINT
3049 @findex REMOTE_BREAKPOINT
3050 Similar to BREAKPOINT, but used for remote targets.
3052 @code{BIG_REMOTE_BREAKPOINT} and @code{LITTLE_REMOTE_BREAKPOINT} have been
3053 deprecated in favor of @code{BREAKPOINT_FROM_PC}.
3055 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3056 @findex BREAKPOINT_FROM_PC
3057 Use the program counter to determine the contents and size of a
3058 breakpoint instruction. It returns a pointer to a string of bytes
3059 that encode a breakpoint instruction, stores the length of the string
3060 to *@var{lenptr}, and adjusts pc (if necessary) to point to the actual
3061 memory location where the breakpoint should be inserted.
3063 Although it is common to use a trap instruction for a breakpoint, it's
3064 not required; for instance, the bit pattern could be an invalid
3065 instruction. The breakpoint must be no longer than the shortest
3066 instruction of the architecture.
3068 Replaces all the other @var{BREAKPOINT} macros.
3070 @item MEMORY_INSERT_BREAKPOINT (@var{addr}, @var{contents_cache})
3071 @itemx MEMORY_REMOVE_BREAKPOINT (@var{addr}, @var{contents_cache})
3072 @findex MEMORY_REMOVE_BREAKPOINT
3073 @findex MEMORY_INSERT_BREAKPOINT
3074 Insert or remove memory based breakpoints. Reasonable defaults
3075 (@code{default_memory_insert_breakpoint} and
3076 @code{default_memory_remove_breakpoint} respectively) have been
3077 provided so that it is not necessary to define these for most
3078 architectures. Architectures which may want to define
3079 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3080 likely have instructions that are oddly sized or are not stored in a
3081 conventional manner.
3083 It may also be desirable (from an efficiency standpoint) to define
3084 custom breakpoint insertion and removal routines if
3085 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3089 @findex CALL_DUMMY_P
3090 A C expression that is non-zero when the target supports inferior function
3093 @item CALL_DUMMY_WORDS
3094 @findex CALL_DUMMY_WORDS
3095 Pointer to an array of @code{LONGEST} words of data containing
3096 host-byte-ordered @code{REGISTER_BYTES} sized values that partially
3097 specify the sequence of instructions needed for an inferior function
3100 Should be deprecated in favor of a macro that uses target-byte-ordered
3103 @item SIZEOF_CALL_DUMMY_WORDS
3104 @findex SIZEOF_CALL_DUMMY_WORDS
3105 The size of @code{CALL_DUMMY_WORDS}. When @code{CALL_DUMMY_P} this must
3106 return a positive value. See also @code{CALL_DUMMY_LENGTH}.
3110 A static initializer for @code{CALL_DUMMY_WORDS}. Deprecated.
3112 @item CALL_DUMMY_LOCATION
3113 @findex CALL_DUMMY_LOCATION
3114 See the file @file{inferior.h}.
3116 @item CALL_DUMMY_STACK_ADJUST
3117 @findex CALL_DUMMY_STACK_ADJUST
3118 Stack adjustment needed when performing an inferior function call.
3120 Should be deprecated in favor of something like @code{STACK_ALIGN}.
3122 @item CALL_DUMMY_STACK_ADJUST_P
3123 @findex CALL_DUMMY_STACK_ADJUST_P
3124 Predicate for use of @code{CALL_DUMMY_STACK_ADJUST}.
3126 Should be deprecated in favor of something like @code{STACK_ALIGN}.
3128 @item CANNOT_FETCH_REGISTER (@var{regno})
3129 @findex CANNOT_FETCH_REGISTER
3130 A C expression that should be nonzero if @var{regno} cannot be fetched
3131 from an inferior process. This is only relevant if
3132 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3134 @item CANNOT_STORE_REGISTER (@var{regno})
3135 @findex CANNOT_STORE_REGISTER
3136 A C expression that should be nonzero if @var{regno} should not be
3137 written to the target. This is often the case for program counters,
3138 status words, and other special registers. If this is not defined,
3139 @value{GDBN} will assume that all registers may be written.
3141 @item DO_DEFERRED_STORES
3142 @itemx CLEAR_DEFERRED_STORES
3143 @findex CLEAR_DEFERRED_STORES
3144 @findex DO_DEFERRED_STORES
3145 Define this to execute any deferred stores of registers into the inferior,
3146 and to cancel any deferred stores.
3148 Currently only implemented correctly for native Sparc configurations?
3150 @item COERCE_FLOAT_TO_DOUBLE (@var{formal}, @var{actual})
3151 @findex COERCE_FLOAT_TO_DOUBLE
3152 @cindex promotion to @code{double}
3153 @cindex @code{float} arguments
3154 @cindex prototyped functions, passing arguments to
3155 @cindex passing arguments to prototyped functions
3156 Return non-zero if GDB should promote @code{float} values to
3157 @code{double} when calling a non-prototyped function. The argument
3158 @var{actual} is the type of the value we want to pass to the function.
3159 The argument @var{formal} is the type of this argument, as it appears in
3160 the function's definition. Note that @var{formal} may be zero if we
3161 have no debugging information for the function, or if we're passing more
3162 arguments than are officially declared (for example, varargs). This
3163 macro is never invoked if the function definitely has a prototype.
3165 How you should pass arguments to a function depends on whether it was
3166 defined in K&R style or prototype style. If you define a function using
3167 the K&R syntax that takes a @code{float} argument, then callers must
3168 pass that argument as a @code{double}. If you define the function using
3169 the prototype syntax, then you must pass the argument as a @code{float},
3172 Unfortunately, on certain older platforms, the debug info doesn't
3173 indicate reliably how each function was defined. A function type's
3174 @code{TYPE_FLAG_PROTOTYPED} flag may be unset, even if the function was
3175 defined in prototype style. When calling a function whose
3176 @code{TYPE_FLAG_PROTOTYPED} flag is unset, GDB consults the
3177 @code{COERCE_FLOAT_TO_DOUBLE} macro to decide what to do.
3179 @findex standard_coerce_float_to_double
3180 For modern targets, it is proper to assume that, if the prototype flag
3181 is unset, that can be trusted: @code{float} arguments should be promoted
3182 to @code{double}. You should use the function
3183 @code{standard_coerce_float_to_double} to get this behavior.
3185 @findex default_coerce_float_to_double
3186 For some older targets, if the prototype flag is unset, that doesn't
3187 tell us anything. So we guess that, if we don't have a type for the
3188 formal parameter (@i{i.e.}, the first argument to
3189 @code{COERCE_FLOAT_TO_DOUBLE} is null), then we should promote it;
3190 otherwise, we should leave it alone. The function
3191 @code{default_coerce_float_to_double} provides this behavior; it is the
3192 default value, for compatibility with older configurations.
3194 @item int CONVERT_REGISTER_P(@var{regnum})
3195 @findex CONVERT_REGISTER_P
3196 Return non-zero if register @var{regnum} can represent data values in a
3198 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3200 @item DBX_PARM_SYMBOL_CLASS
3201 @findex DBX_PARM_SYMBOL_CLASS
3202 Hook for the @code{SYMBOL_CLASS} of a parameter when decoding DBX symbol
3203 information. In the i960, parameters can be stored as locals or as
3204 args, depending on the type of the debug record.
3206 @item DECR_PC_AFTER_BREAK
3207 @findex DECR_PC_AFTER_BREAK
3208 Define this to be the amount by which to decrement the PC after the
3209 program encounters a breakpoint. This is often the number of bytes in
3210 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3212 @item DECR_PC_AFTER_HW_BREAK
3213 @findex DECR_PC_AFTER_HW_BREAK
3214 Similarly, for hardware breakpoints.
3216 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3217 @findex DISABLE_UNSETTABLE_BREAK
3218 If defined, this should evaluate to 1 if @var{addr} is in a shared
3219 library in which breakpoints cannot be set and so should be disabled.
3221 @item DO_REGISTERS_INFO
3222 @findex DO_REGISTERS_INFO
3223 If defined, use this to print the value of a register or all registers.
3225 This method is deprecated.
3227 @item PRINT_FLOAT_INFO()
3228 @findex PRINT_FLOAT_INFO
3229 If defined, then the @samp{info float} command will print information about
3230 the processor's floating point unit.
3232 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3233 @findex print_registers_info
3234 If defined, pretty print the value of the register @var{regnum} for the
3235 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3236 either all registers (@var{all} is non zero) or a select subset of
3237 registers (@var{all} is zero).
3239 The default method prints one register per line, and if @var{all} is
3240 zero omits floating-point registers.
3242 @item PRINT_VECTOR_INFO()
3243 @findex PRINT_VECTOR_INFO
3244 If defined, then the @samp{info vector} command will call this function
3245 to print information about the processor's vector unit.
3247 By default, the @samp{info vector} command will print all vector
3248 registers (the register's type having the vector attribute).
3250 @item DWARF_REG_TO_REGNUM
3251 @findex DWARF_REG_TO_REGNUM
3252 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3253 no conversion will be performed.
3255 @item DWARF2_REG_TO_REGNUM
3256 @findex DWARF2_REG_TO_REGNUM
3257 Convert DWARF2 register number into @value{GDBN} regnum. If not
3258 defined, no conversion will be performed.
3260 @item ECOFF_REG_TO_REGNUM
3261 @findex ECOFF_REG_TO_REGNUM
3262 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3263 no conversion will be performed.
3265 @item END_OF_TEXT_DEFAULT
3266 @findex END_OF_TEXT_DEFAULT
3267 This is an expression that should designate the end of the text section.
3270 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3271 @findex EXTRACT_RETURN_VALUE
3272 Define this to extract a function's return value of type @var{type} from
3273 the raw register state @var{regbuf} and copy that, in virtual format,
3276 @item EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3277 @findex EXTRACT_STRUCT_VALUE_ADDRESS
3278 When defined, extract from the array @var{regbuf} (containing the raw
3279 register state) the @code{CORE_ADDR} at which a function should return
3280 its structure value.
3282 If not defined, @code{EXTRACT_RETURN_VALUE} is used.
3284 @item EXTRACT_STRUCT_VALUE_ADDRESS_P()
3285 @findex EXTRACT_STRUCT_VALUE_ADDRESS_P
3286 Predicate for @code{EXTRACT_STRUCT_VALUE_ADDRESS}.
3290 Deprecated in favor of @code{PRINT_FLOAT_INFO}.
3294 If the virtual frame pointer is kept in a register, then define this
3295 macro to be the number (greater than or equal to zero) of that register.
3297 This should only need to be defined if @code{TARGET_READ_FP} is not
3300 @item FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3301 @findex FRAMELESS_FUNCTION_INVOCATION
3302 Define this to an expression that returns 1 if the function invocation
3303 represented by @var{fi} does not have a stack frame associated with it.
3306 @item frame_align (@var{address})
3307 @anchor{frame_align}
3309 Define this to adjust @var{address} so that it meets the alignment
3310 requirements for the start of a new stack frame. A stack frame's
3311 alignment requirements are typically stronger than a target processors
3312 stack alignment requirements (@pxref{STACK_ALIGN}).
3314 This function is used to ensure that, when creating a dummy frame, both
3315 the initial stack pointer and (if needed) the address of the return
3316 value are correctly aligned.
3318 Unlike @code{STACK_ALIGN}, this function always adjusts the address in
3319 the direction of stack growth.
3321 By default, no frame based stack alignment is performed.
3323 @item FRAME_ARGS_ADDRESS_CORRECT
3324 @findex FRAME_ARGS_ADDRESS_CORRECT
3327 @item FRAME_CHAIN(@var{frame})
3329 Given @var{frame}, return a pointer to the calling frame.
3331 @item FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3332 @findex FRAME_CHAIN_VALID
3333 Define this to be an expression that returns zero if the given frame is
3334 an outermost frame, with no caller, and nonzero otherwise. Several
3335 common definitions are available:
3339 @code{file_frame_chain_valid} is nonzero if the chain pointer is nonzero
3340 and given frame's PC is not inside the startup file (such as
3344 @code{func_frame_chain_valid} is nonzero if the chain
3345 pointer is nonzero and the given frame's PC is not in @code{main} or a
3346 known entry point function (such as @code{_start}).
3349 @code{generic_file_frame_chain_valid} and
3350 @code{generic_func_frame_chain_valid} are equivalent implementations for
3351 targets using generic dummy frames.
3354 @item FRAME_INIT_SAVED_REGS(@var{frame})
3355 @findex FRAME_INIT_SAVED_REGS
3356 See @file{frame.h}. Determines the address of all registers in the
3357 current stack frame storing each in @code{frame->saved_regs}. Space for
3358 @code{frame->saved_regs} shall be allocated by
3359 @code{FRAME_INIT_SAVED_REGS} using either
3360 @code{frame_saved_regs_zalloc} or @code{frame_obstack_alloc}.
3362 @code{FRAME_FIND_SAVED_REGS} and @code{EXTRA_FRAME_INFO} are deprecated.
3364 @item FRAME_NUM_ARGS (@var{fi})
3365 @findex FRAME_NUM_ARGS
3366 For the frame described by @var{fi} return the number of arguments that
3367 are being passed. If the number of arguments is not known, return
3370 @item FRAME_SAVED_PC(@var{frame})
3371 @findex FRAME_SAVED_PC
3372 Given @var{frame}, return the pc saved there. This is the return
3375 @item FUNCTION_EPILOGUE_SIZE
3376 @findex FUNCTION_EPILOGUE_SIZE
3377 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3378 function end symbol is 0. For such targets, you must define
3379 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3380 function's epilogue.
3382 @item FUNCTION_START_OFFSET
3383 @findex FUNCTION_START_OFFSET
3384 An integer, giving the offset in bytes from a function's address (as
3385 used in the values of symbols, function pointers, etc.), and the
3386 function's first genuine instruction.
3388 This is zero on almost all machines: the function's address is usually
3389 the address of its first instruction. However, on the VAX, for example,
3390 each function starts with two bytes containing a bitmask indicating
3391 which registers to save upon entry to the function. The VAX @code{call}
3392 instructions check this value, and save the appropriate registers
3393 automatically. Thus, since the offset from the function's address to
3394 its first instruction is two bytes, @code{FUNCTION_START_OFFSET} would
3397 @item GCC_COMPILED_FLAG_SYMBOL
3398 @itemx GCC2_COMPILED_FLAG_SYMBOL
3399 @findex GCC2_COMPILED_FLAG_SYMBOL
3400 @findex GCC_COMPILED_FLAG_SYMBOL
3401 If defined, these are the names of the symbols that @value{GDBN} will
3402 look for to detect that GCC compiled the file. The default symbols
3403 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3404 respectively. (Currently only defined for the Delta 68.)
3406 @item @value{GDBN}_MULTI_ARCH
3407 @findex @value{GDBN}_MULTI_ARCH
3408 If defined and non-zero, enables support for multiple architectures
3409 within @value{GDBN}.
3411 This support can be enabled at two levels. At level one, only
3412 definitions for previously undefined macros are provided; at level two,
3413 a multi-arch definition of all architecture dependent macros will be
3416 @item @value{GDBN}_TARGET_IS_HPPA
3417 @findex @value{GDBN}_TARGET_IS_HPPA
3418 This determines whether horrible kludge code in @file{dbxread.c} and
3419 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3420 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3423 @item GET_LONGJMP_TARGET
3424 @findex GET_LONGJMP_TARGET
3425 For most machines, this is a target-dependent parameter. On the
3426 DECstation and the Iris, this is a native-dependent parameter, since
3427 the header file @file{setjmp.h} is needed to define it.
3429 This macro determines the target PC address that @code{longjmp} will jump to,
3430 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3431 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3432 pointer. It examines the current state of the machine as needed.
3434 @item GET_SAVED_REGISTER
3435 @findex GET_SAVED_REGISTER
3436 @findex get_saved_register
3437 Define this if you need to supply your own definition for the function
3438 @code{get_saved_register}.
3440 @item IBM6000_TARGET
3441 @findex IBM6000_TARGET
3442 Shows that we are configured for an IBM RS/6000 target. This
3443 conditional should be eliminated (FIXME) and replaced by
3444 feature-specific macros. It was introduced in a haste and we are
3445 repenting at leisure.
3447 @item I386_USE_GENERIC_WATCHPOINTS
3448 An x86-based target can define this to use the generic x86 watchpoint
3449 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3451 @item SYMBOLS_CAN_START_WITH_DOLLAR
3452 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3453 Some systems have routines whose names start with @samp{$}. Giving this
3454 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3455 routines when parsing tokens that begin with @samp{$}.
3457 On HP-UX, certain system routines (millicode) have names beginning with
3458 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3459 routine that handles inter-space procedure calls on PA-RISC.
3461 @item INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3462 @findex INIT_EXTRA_FRAME_INFO
3463 If additional information about the frame is required this should be
3464 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3465 is allocated using @code{frame_obstack_alloc}.
3467 @item INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3468 @findex INIT_FRAME_PC
3469 This is a C statement that sets the pc of the frame pointed to by
3470 @var{prev}. [By default...]
3472 @item INNER_THAN (@var{lhs}, @var{rhs})
3474 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3475 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3476 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3479 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3480 @findex gdbarch_in_function_epilogue_p
3481 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3482 The epilogue of a function is defined as the part of a function where
3483 the stack frame of the function already has been destroyed up to the
3484 final `return from function call' instruction.
3486 @item SIGTRAMP_START (@var{pc})
3487 @findex SIGTRAMP_START
3488 @itemx SIGTRAMP_END (@var{pc})
3489 @findex SIGTRAMP_END
3490 Define these to be the start and end address of the @code{sigtramp} for the
3491 given @var{pc}. On machines where the address is just a compile time
3492 constant, the macro expansion will typically just ignore the supplied
3495 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3496 @findex IN_SOLIB_CALL_TRAMPOLINE
3497 Define this to evaluate to nonzero if the program is stopped in the
3498 trampoline that connects to a shared library.
3500 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3501 @findex IN_SOLIB_RETURN_TRAMPOLINE
3502 Define this to evaluate to nonzero if the program is stopped in the
3503 trampoline that returns from a shared library.
3505 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3506 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3507 Define this to evaluate to nonzero if the program is stopped in the
3510 @item SKIP_SOLIB_RESOLVER (@var{pc})
3511 @findex SKIP_SOLIB_RESOLVER
3512 Define this to evaluate to the (nonzero) address at which execution
3513 should continue to get past the dynamic linker's symbol resolution
3514 function. A zero value indicates that it is not important or necessary
3515 to set a breakpoint to get through the dynamic linker and that single
3516 stepping will suffice.
3518 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3519 @findex INTEGER_TO_ADDRESS
3520 @cindex converting integers to addresses
3521 Define this when the architecture needs to handle non-pointer to address
3522 conversions specially. Converts that value to an address according to
3523 the current architectures conventions.
3525 @emph{Pragmatics: When the user copies a well defined expression from
3526 their source code and passes it, as a parameter, to @value{GDBN}'s
3527 @code{print} command, they should get the same value as would have been
3528 computed by the target program. Any deviation from this rule can cause
3529 major confusion and annoyance, and needs to be justified carefully. In
3530 other words, @value{GDBN} doesn't really have the freedom to do these
3531 conversions in clever and useful ways. It has, however, been pointed
3532 out that users aren't complaining about how @value{GDBN} casts integers
3533 to pointers; they are complaining that they can't take an address from a
3534 disassembly listing and give it to @code{x/i}. Adding an architecture
3535 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3536 @value{GDBN} to ``get it right'' in all circumstances.}
3538 @xref{Target Architecture Definition, , Pointers Are Not Always
3541 @item IS_TRAPPED_INTERNALVAR (@var{name})
3542 @findex IS_TRAPPED_INTERNALVAR
3543 This is an ugly hook to allow the specification of special actions that
3544 should occur as a side-effect of setting the value of a variable
3545 internal to @value{GDBN}. Currently only used by the h8500. Note that this
3546 could be either a host or target conditional.
3548 @item NEED_TEXT_START_END
3549 @findex NEED_TEXT_START_END
3550 Define this if @value{GDBN} should determine the start and end addresses of the
3551 text section. (Seems dubious.)
3553 @item NO_HIF_SUPPORT
3554 @findex NO_HIF_SUPPORT
3555 (Specific to the a29k.)
3557 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3558 @findex POINTER_TO_ADDRESS
3559 Assume that @var{buf} holds a pointer of type @var{type}, in the
3560 appropriate format for the current architecture. Return the byte
3561 address the pointer refers to.
3562 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3564 @item REGISTER_CONVERTIBLE (@var{reg})
3565 @findex REGISTER_CONVERTIBLE
3566 Return non-zero if @var{reg} uses different raw and virtual formats.
3567 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3569 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3570 @findex REGISTER_TO_VALUE
3571 Convert the raw contents of register @var{regnum} into a value of type
3573 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3575 @item REGISTER_RAW_SIZE (@var{reg})
3576 @findex REGISTER_RAW_SIZE
3577 Return the raw size of @var{reg}; defaults to the size of the register's
3579 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3581 @item REGISTER_VIRTUAL_SIZE (@var{reg})
3582 @findex REGISTER_VIRTUAL_SIZE
3583 Return the virtual size of @var{reg}; defaults to the size of the
3584 register's virtual type.
3585 Return the virtual size of @var{reg}.
3586 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3588 @item REGISTER_VIRTUAL_TYPE (@var{reg})
3589 @findex REGISTER_VIRTUAL_TYPE
3590 Return the virtual type of @var{reg}.
3591 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3593 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3594 @findex REGISTER_CONVERT_TO_VIRTUAL
3595 Convert the value of register @var{reg} from its raw form to its virtual
3597 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3599 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3600 @findex REGISTER_CONVERT_TO_RAW
3601 Convert the value of register @var{reg} from its virtual form to its raw
3603 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3605 @item RETURN_VALUE_ON_STACK(@var{type})
3606 @findex RETURN_VALUE_ON_STACK
3607 @cindex returning structures by value
3608 @cindex structures, returning by value
3610 Return non-zero if values of type TYPE are returned on the stack, using
3611 the ``struct convention'' (i.e., the caller provides a pointer to a
3612 buffer in which the callee should store the return value). This
3613 controls how the @samp{finish} command finds a function's return value,
3614 and whether an inferior function call reserves space on the stack for
3617 The full logic @value{GDBN} uses here is kind of odd.
3621 If the type being returned by value is not a structure, union, or array,
3622 and @code{RETURN_VALUE_ON_STACK} returns zero, then @value{GDBN}
3623 concludes the value is not returned using the struct convention.
3626 Otherwise, @value{GDBN} calls @code{USE_STRUCT_CONVENTION} (see below).
3627 If that returns non-zero, @value{GDBN} assumes the struct convention is
3631 In other words, to indicate that a given type is returned by value using
3632 the struct convention, that type must be either a struct, union, array,
3633 or something @code{RETURN_VALUE_ON_STACK} likes, @emph{and} something
3634 that @code{USE_STRUCT_CONVENTION} likes.
3636 Note that, in C and C@t{++}, arrays are never returned by value. In those
3637 languages, these predicates will always see a pointer type, never an
3638 array type. All the references above to arrays being returned by value
3639 apply only to other languages.
3641 @item SOFTWARE_SINGLE_STEP_P()
3642 @findex SOFTWARE_SINGLE_STEP_P
3643 Define this as 1 if the target does not have a hardware single-step
3644 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3646 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breapoints_p})
3647 @findex SOFTWARE_SINGLE_STEP
3648 A function that inserts or removes (depending on
3649 @var{insert_breapoints_p}) breakpoints at each possible destinations of
3650 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3653 @item SOFUN_ADDRESS_MAYBE_MISSING
3654 @findex SOFUN_ADDRESS_MAYBE_MISSING
3655 Somebody clever observed that, the more actual addresses you have in the
3656 debug information, the more time the linker has to spend relocating
3657 them. So whenever there's some other way the debugger could find the
3658 address it needs, you should omit it from the debug info, to make
3661 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3662 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3663 entries in stabs-format debugging information. @code{N_SO} stabs mark
3664 the beginning and ending addresses of compilation units in the text
3665 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3667 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3671 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3672 addresses where the function starts by taking the function name from
3673 the stab, and then looking that up in the minsyms (the
3674 linker/assembler symbol table). In other words, the stab has the
3675 name, and the linker/assembler symbol table is the only place that carries
3679 @code{N_SO} stabs have an address of zero, too. You just look at the
3680 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3681 and guess the starting and ending addresses of the compilation unit from
3685 @item PCC_SOL_BROKEN
3686 @findex PCC_SOL_BROKEN
3687 (Used only in the Convex target.)
3689 @item PC_IN_CALL_DUMMY
3690 @findex PC_IN_CALL_DUMMY
3691 See @file{inferior.h}.
3693 @item PC_IN_SIGTRAMP (@var{pc}, @var{name})
3694 @findex PC_IN_SIGTRAMP
3696 The @dfn{sigtramp} is a routine that the kernel calls (which then calls
3697 the signal handler). On most machines it is a library routine that is
3698 linked into the executable.
3700 This function, given a program counter value in @var{pc} and the
3701 (possibly NULL) name of the function in which that @var{pc} resides,
3702 returns nonzero if the @var{pc} and/or @var{name} show that we are in
3705 @item PC_LOAD_SEGMENT
3706 @findex PC_LOAD_SEGMENT
3707 If defined, print information about the load segment for the program
3708 counter. (Defined only for the RS/6000.)
3712 If the program counter is kept in a register, then define this macro to
3713 be the number (greater than or equal to zero) of that register.
3715 This should only need to be defined if @code{TARGET_READ_PC} and
3716 @code{TARGET_WRITE_PC} are not defined.
3720 The number of the ``next program counter'' register, if defined.
3723 @findex PARM_BOUNDARY
3724 If non-zero, round arguments to a boundary of this many bits before
3725 pushing them on the stack.
3727 @item PRINT_REGISTER_HOOK (@var{regno})
3728 @findex PRINT_REGISTER_HOOK
3729 If defined, this must be a function that prints the contents of the
3730 given register to standard output.
3732 @item PRINT_TYPELESS_INTEGER
3733 @findex PRINT_TYPELESS_INTEGER
3734 This is an obscure substitute for @code{print_longest} that seems to
3735 have been defined for the Convex target.
3737 @item PROCESS_LINENUMBER_HOOK
3738 @findex PROCESS_LINENUMBER_HOOK
3739 A hook defined for XCOFF reading.
3741 @item PROLOGUE_FIRSTLINE_OVERLAP
3742 @findex PROLOGUE_FIRSTLINE_OVERLAP
3743 (Only used in unsupported Convex configuration.)
3747 If defined, this is the number of the processor status register. (This
3748 definition is only used in generic code when parsing "$ps".)
3752 @findex call_function_by_hand
3753 @findex return_command
3754 Used in @samp{call_function_by_hand} to remove an artificial stack
3755 frame and in @samp{return_command} to remove a real stack frame.
3757 @item PUSH_ARGUMENTS (@var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
3758 @findex PUSH_ARGUMENTS
3759 Define this to push arguments onto the stack for inferior function
3760 call. Returns the updated stack pointer value.
3762 @item PUSH_DUMMY_FRAME
3763 @findex PUSH_DUMMY_FRAME
3764 Used in @samp{call_function_by_hand} to create an artificial stack frame.
3766 @item REGISTER_BYTES
3767 @findex REGISTER_BYTES
3768 The total amount of space needed to store @value{GDBN}'s copy of the machine's
3771 @item REGISTER_NAME(@var{i})
3772 @findex REGISTER_NAME
3773 Return the name of register @var{i} as a string. May return @code{NULL}
3774 or @code{NUL} to indicate that register @var{i} is not valid.
3776 @item REGISTER_NAMES
3777 @findex REGISTER_NAMES
3778 Deprecated in favor of @code{REGISTER_NAME}.
3780 @item REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3781 @findex REG_STRUCT_HAS_ADDR
3782 Define this to return 1 if the given type will be passed by pointer
3783 rather than directly.
3785 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3786 @findex SAVE_DUMMY_FRAME_TOS
3787 Used in @samp{call_function_by_hand} to notify the target dependent code
3788 of the top-of-stack value that will be passed to the the inferior code.
3789 This is the value of the @code{SP} after both the dummy frame and space
3790 for parameters/results have been allocated on the stack.
3792 @item SDB_REG_TO_REGNUM
3793 @findex SDB_REG_TO_REGNUM
3794 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3795 defined, no conversion will be done.
3797 @c OBSOLETE @item SHIFT_INST_REGS
3798 @c OBSOLETE @findex SHIFT_INST_REGS
3799 @c OBSOLETE (Only used for m88k targets.)
3801 @item SKIP_PERMANENT_BREAKPOINT
3802 @findex SKIP_PERMANENT_BREAKPOINT
3803 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
3804 steps over a breakpoint by removing it, stepping one instruction, and
3805 re-inserting the breakpoint. However, permanent breakpoints are
3806 hardwired into the inferior, and can't be removed, so this strategy
3807 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
3808 state so that execution will resume just after the breakpoint. This
3809 macro does the right thing even when the breakpoint is in the delay slot
3810 of a branch or jump.
3812 @item SKIP_PROLOGUE (@var{pc})
3813 @findex SKIP_PROLOGUE
3814 A C expression that returns the address of the ``real'' code beyond the
3815 function entry prologue found at @var{pc}.
3817 @item SKIP_TRAMPOLINE_CODE (@var{pc})
3818 @findex SKIP_TRAMPOLINE_CODE
3819 If the target machine has trampoline code that sits between callers and
3820 the functions being called, then define this macro to return a new PC
3821 that is at the start of the real function.
3825 If the stack-pointer is kept in a register, then define this macro to be
3826 the number (greater than or equal to zero) of that register.
3828 This should only need to be defined if @code{TARGET_WRITE_SP} and
3829 @code{TARGET_WRITE_SP} are not defined.
3831 @item STAB_REG_TO_REGNUM
3832 @findex STAB_REG_TO_REGNUM
3833 Define this to convert stab register numbers (as gotten from `r'
3834 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
3837 @item STACK_ALIGN (@var{addr})
3838 @anchor{STACK_ALIGN}
3840 Define this to increase @var{addr} so that it meets the alignment
3841 requirements for the processor's stack.
3843 Unlike @ref{frame_align}, this function always adjusts @var{addr}
3846 By default, no stack alignment is performed.
3848 @item STEP_SKIPS_DELAY (@var{addr})
3849 @findex STEP_SKIPS_DELAY
3850 Define this to return true if the address is of an instruction with a
3851 delay slot. If a breakpoint has been placed in the instruction's delay
3852 slot, @value{GDBN} will single-step over that instruction before resuming
3853 normally. Currently only defined for the Mips.
3855 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
3856 @findex STORE_RETURN_VALUE
3857 A C expression that writes the function return value, found in
3858 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
3859 value that is to be returned.
3861 @item SUN_FIXED_LBRAC_BUG
3862 @findex SUN_FIXED_LBRAC_BUG
3863 (Used only for Sun-3 and Sun-4 targets.)
3865 @item SYMBOL_RELOADING_DEFAULT
3866 @findex SYMBOL_RELOADING_DEFAULT
3867 The default value of the ``symbol-reloading'' variable. (Never defined in
3870 @item TARGET_CHAR_BIT
3871 @findex TARGET_CHAR_BIT
3872 Number of bits in a char; defaults to 8.
3874 @item TARGET_CHAR_SIGNED
3875 @findex TARGET_CHAR_SIGNED
3876 Non-zero if @code{char} is normally signed on this architecture; zero if
3877 it should be unsigned.
3879 The ISO C standard requires the compiler to treat @code{char} as
3880 equivalent to either @code{signed char} or @code{unsigned char}; any
3881 character in the standard execution set is supposed to be positive.
3882 Most compilers treat @code{char} as signed, but @code{char} is unsigned
3883 on the IBM S/390, RS6000, and PowerPC targets.
3885 @item TARGET_COMPLEX_BIT
3886 @findex TARGET_COMPLEX_BIT
3887 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
3889 At present this macro is not used.
3891 @item TARGET_DOUBLE_BIT
3892 @findex TARGET_DOUBLE_BIT
3893 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
3895 @item TARGET_DOUBLE_COMPLEX_BIT
3896 @findex TARGET_DOUBLE_COMPLEX_BIT
3897 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
3899 At present this macro is not used.
3901 @item TARGET_FLOAT_BIT
3902 @findex TARGET_FLOAT_BIT
3903 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
3905 @item TARGET_INT_BIT
3906 @findex TARGET_INT_BIT
3907 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3909 @item TARGET_LONG_BIT
3910 @findex TARGET_LONG_BIT
3911 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3913 @item TARGET_LONG_DOUBLE_BIT
3914 @findex TARGET_LONG_DOUBLE_BIT
3915 Number of bits in a long double float;
3916 defaults to @code{2 * TARGET_DOUBLE_BIT}.
3918 @item TARGET_LONG_LONG_BIT
3919 @findex TARGET_LONG_LONG_BIT
3920 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
3922 @item TARGET_PTR_BIT
3923 @findex TARGET_PTR_BIT
3924 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
3926 @item TARGET_SHORT_BIT
3927 @findex TARGET_SHORT_BIT
3928 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
3930 @item TARGET_READ_PC
3931 @findex TARGET_READ_PC
3932 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
3933 @findex TARGET_WRITE_PC
3934 @itemx TARGET_READ_SP
3935 @findex TARGET_READ_SP
3936 @itemx TARGET_WRITE_SP
3937 @findex TARGET_WRITE_SP
3938 @itemx TARGET_READ_FP
3939 @findex TARGET_READ_FP
3945 These change the behavior of @code{read_pc}, @code{write_pc},
3946 @code{read_sp}, @code{write_sp} and @code{read_fp}. For most targets,
3947 these may be left undefined. @value{GDBN} will call the read and write
3948 register functions with the relevant @code{_REGNUM} argument.
3950 These macros are useful when a target keeps one of these registers in a
3951 hard to get at place; for example, part in a segment register and part
3952 in an ordinary register.
3954 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
3955 @findex TARGET_VIRTUAL_FRAME_POINTER
3956 Returns a @code{(register, offset)} pair representing the virtual
3957 frame pointer in use at the code address @var{pc}. If virtual
3958 frame pointers are not used, a default definition simply returns
3959 @code{FP_REGNUM}, with an offset of zero.
3961 @item TARGET_HAS_HARDWARE_WATCHPOINTS
3962 If non-zero, the target has support for hardware-assisted
3963 watchpoints. @xref{Algorithms, watchpoints}, for more details and
3964 other related macros.
3966 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
3967 @findex TARGET_PRINT_INSN
3968 This is the function used by @value{GDBN} to print an assembly
3969 instruction. It prints the instruction at address @var{addr} in
3970 debugged memory and returns the length of the instruction, in bytes. If
3971 a target doesn't define its own printing routine, it defaults to an
3972 accessor function for the global pointer @code{tm_print_insn}. This
3973 usually points to a function in the @code{opcodes} library (@pxref{Support
3974 Libraries, ,Opcodes}). @var{info} is a structure (of type
3975 @code{disassemble_info}) defined in @file{include/dis-asm.h} used to
3976 pass information to the instruction decoding routine.
3978 @item USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
3979 @findex USE_STRUCT_CONVENTION
3980 If defined, this must be an expression that is nonzero if a value of the
3981 given @var{type} being returned from a function must have space
3982 allocated for it on the stack. @var{gcc_p} is true if the function
3983 being considered is known to have been compiled by GCC; this is helpful
3984 for systems where GCC is known to use different calling convention than
3987 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
3988 @findex VALUE_TO_REGISTER
3989 Convert a value of type @var{type} into the raw contents of register
3991 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3993 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3994 @findex VARIABLES_INSIDE_BLOCK
3995 For dbx-style debugging information, if the compiler puts variable
3996 declarations inside LBRAC/RBRAC blocks, this should be defined to be
3997 nonzero. @var{desc} is the value of @code{n_desc} from the
3998 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
3999 presence of either the @code{GCC_COMPILED_SYMBOL} or the
4000 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
4002 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
4003 @findex OS9K_VARIABLES_INSIDE_BLOCK
4004 Similarly, for OS/9000. Defaults to 1.
4007 Motorola M68K target conditionals.
4011 Define this to be the 4-bit location of the breakpoint trap vector. If
4012 not defined, it will default to @code{0xf}.
4014 @item REMOTE_BPT_VECTOR
4015 Defaults to @code{1}.
4017 @item NAME_OF_MALLOC
4018 @findex NAME_OF_MALLOC
4019 A string containing the name of the function to call in order to
4020 allocate some memory in the inferior. The default value is "malloc".
4024 @section Adding a New Target
4026 @cindex adding a target
4027 The following files add a target to @value{GDBN}:
4031 @item gdb/config/@var{arch}/@var{ttt}.mt
4032 Contains a Makefile fragment specific to this target. Specifies what
4033 object files are needed for target @var{ttt}, by defining
4034 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
4035 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
4038 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
4039 but these are now deprecated, replaced by autoconf, and may go away in
4040 future versions of @value{GDBN}.
4042 @item gdb/@var{ttt}-tdep.c
4043 Contains any miscellaneous code required for this target machine. On
4044 some machines it doesn't exist at all. Sometimes the macros in
4045 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
4046 as functions here instead, and the macro is simply defined to call the
4047 function. This is vastly preferable, since it is easier to understand
4050 @item gdb/@var{arch}-tdep.c
4051 @itemx gdb/@var{arch}-tdep.h
4052 This often exists to describe the basic layout of the target machine's
4053 processor chip (registers, stack, etc.). If used, it is included by
4054 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
4057 @item gdb/config/@var{arch}/tm-@var{ttt}.h
4058 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
4059 macro definitions about the target machine's registers, stack frame
4060 format and instructions.
4062 New targets do not need this file and should not create it.
4064 @item gdb/config/@var{arch}/tm-@var{arch}.h
4065 This often exists to describe the basic layout of the target machine's
4066 processor chip (registers, stack, etc.). If used, it is included by
4067 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
4070 New targets do not need this file and should not create it.
4074 If you are adding a new operating system for an existing CPU chip, add a
4075 @file{config/tm-@var{os}.h} file that describes the operating system
4076 facilities that are unusual (extra symbol table info; the breakpoint
4077 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
4078 that just @code{#include}s @file{tm-@var{arch}.h} and
4079 @file{config/tm-@var{os}.h}.
4082 @section Converting an existing Target Architecture to Multi-arch
4083 @cindex converting targets to multi-arch
4085 This section describes the current accepted best practice for converting
4086 an existing target architecture to the multi-arch framework.
4088 The process consists of generating, testing, posting and committing a
4089 sequence of patches. Each patch must contain a single change, for
4095 Directly convert a group of functions into macros (the conversion does
4096 not change the behavior of any of the functions).
4099 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4103 Enable multi-arch level one.
4106 Delete one or more files.
4111 There isn't a size limit on a patch, however, a developer is strongly
4112 encouraged to keep the patch size down.
4114 Since each patch is well defined, and since each change has been tested
4115 and shows no regressions, the patches are considered @emph{fairly}
4116 obvious. Such patches, when submitted by developers listed in the
4117 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4118 process may be more complicated and less clear. The developer is
4119 expected to use their judgment and is encouraged to seek advice as
4122 @subsection Preparation
4124 The first step is to establish control. Build (with @option{-Werror}
4125 enabled) and test the target so that there is a baseline against which
4126 the debugger can be compared.
4128 At no stage can the test results regress or @value{GDBN} stop compiling
4129 with @option{-Werror}.
4131 @subsection Add the multi-arch initialization code
4133 The objective of this step is to establish the basic multi-arch
4134 framework. It involves
4139 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4140 above is from the original example and uses K&R C. @value{GDBN}
4141 has since converted to ISO C but lets ignore that.} that creates
4144 static struct gdbarch *
4145 d10v_gdbarch_init (info, arches)
4146 struct gdbarch_info info;
4147 struct gdbarch_list *arches;
4149 struct gdbarch *gdbarch;
4150 /* there is only one d10v architecture */
4152 return arches->gdbarch;
4153 gdbarch = gdbarch_alloc (&info, NULL);
4161 A per-architecture dump function to print any architecture specific
4165 mips_dump_tdep (struct gdbarch *current_gdbarch,
4166 struct ui_file *file)
4168 @dots{} code to print architecture specific info @dots{}
4173 A change to @code{_initialize_@var{arch}_tdep} to register this new
4177 _initialize_mips_tdep (void)
4179 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4184 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4185 @file{config/@var{arch}/tm-@var{arch}.h}.
4189 @subsection Update multi-arch incompatible mechanisms
4191 Some mechanisms do not work with multi-arch. They include:
4194 @item EXTRA_FRAME_INFO
4196 @item FRAME_FIND_SAVED_REGS
4197 Replaced with @code{FRAME_INIT_SAVED_REGS}
4201 At this stage you could also consider converting the macros into
4204 @subsection Prepare for multi-arch level to one
4206 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4207 and then build and start @value{GDBN} (the change should not be
4208 committed). @value{GDBN} may not build, and once built, it may die with
4209 an internal error listing the architecture methods that must be
4212 Fix any build problems (patch(es)).
4214 Convert all the architecture methods listed, which are only macros, into
4215 functions (patch(es)).
4217 Update @code{@var{arch}_gdbarch_init} to set all the missing
4218 architecture methods and wrap the corresponding macros in @code{#if
4219 !GDB_MULTI_ARCH} (patch(es)).
4221 @subsection Set multi-arch level one
4223 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4226 Any problems with throwing ``the switch'' should have been fixed
4229 @subsection Convert remaining macros
4231 Suggest converting macros into functions (and setting the corresponding
4232 architecture method) in small batches.
4234 @subsection Set multi-arch level to two
4236 This should go smoothly.
4238 @subsection Delete the TM file
4240 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4241 @file{configure.in} updated.
4244 @node Target Vector Definition
4246 @chapter Target Vector Definition
4247 @cindex target vector
4249 The target vector defines the interface between @value{GDBN}'s
4250 abstract handling of target systems, and the nitty-gritty code that
4251 actually exercises control over a process or a serial port.
4252 @value{GDBN} includes some 30-40 different target vectors; however,
4253 each configuration of @value{GDBN} includes only a few of them.
4255 @section File Targets
4257 Both executables and core files have target vectors.
4259 @section Standard Protocol and Remote Stubs
4261 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4262 that runs in the target system. @value{GDBN} provides several sample
4263 @dfn{stubs} that can be integrated into target programs or operating
4264 systems for this purpose; they are named @file{*-stub.c}.
4266 The @value{GDBN} user's manual describes how to put such a stub into
4267 your target code. What follows is a discussion of integrating the
4268 SPARC stub into a complicated operating system (rather than a simple
4269 program), by Stu Grossman, the author of this stub.
4271 The trap handling code in the stub assumes the following upon entry to
4276 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4282 you are in the correct trap window.
4285 As long as your trap handler can guarantee those conditions, then there
4286 is no reason why you shouldn't be able to ``share'' traps with the stub.
4287 The stub has no requirement that it be jumped to directly from the
4288 hardware trap vector. That is why it calls @code{exceptionHandler()},
4289 which is provided by the external environment. For instance, this could
4290 set up the hardware traps to actually execute code which calls the stub
4291 first, and then transfers to its own trap handler.
4293 For the most point, there probably won't be much of an issue with
4294 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4295 and often indicate unrecoverable error conditions. Anyway, this is all
4296 controlled by a table, and is trivial to modify. The most important
4297 trap for us is for @code{ta 1}. Without that, we can't single step or
4298 do breakpoints. Everything else is unnecessary for the proper operation
4299 of the debugger/stub.
4301 From reading the stub, it's probably not obvious how breakpoints work.
4302 They are simply done by deposit/examine operations from @value{GDBN}.
4304 @section ROM Monitor Interface
4306 @section Custom Protocols
4308 @section Transport Layer
4310 @section Builtin Simulator
4313 @node Native Debugging
4315 @chapter Native Debugging
4316 @cindex native debugging
4318 Several files control @value{GDBN}'s configuration for native support:
4322 @item gdb/config/@var{arch}/@var{xyz}.mh
4323 Specifies Makefile fragments needed by a @emph{native} configuration on
4324 machine @var{xyz}. In particular, this lists the required
4325 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4326 Also specifies the header file which describes native support on
4327 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4328 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4329 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4331 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4332 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4333 on machine @var{xyz}. While the file is no longer used for this
4334 purpose, the @file{.mh} suffix remains. Perhaps someone will
4335 eventually rename these fragments so that they have a @file{.mn}
4338 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4339 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4340 macro definitions describing the native system environment, such as
4341 child process control and core file support.
4343 @item gdb/@var{xyz}-nat.c
4344 Contains any miscellaneous C code required for this native support of
4345 this machine. On some machines it doesn't exist at all.
4348 There are some ``generic'' versions of routines that can be used by
4349 various systems. These can be customized in various ways by macros
4350 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4351 the @var{xyz} host, you can just include the generic file's name (with
4352 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4354 Otherwise, if your machine needs custom support routines, you will need
4355 to write routines that perform the same functions as the generic file.
4356 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4357 into @code{NATDEPFILES}.
4361 This contains the @emph{target_ops vector} that supports Unix child
4362 processes on systems which use ptrace and wait to control the child.
4365 This contains the @emph{target_ops vector} that supports Unix child
4366 processes on systems which use /proc to control the child.
4369 This does the low-level grunge that uses Unix system calls to do a ``fork
4370 and exec'' to start up a child process.
4373 This is the low level interface to inferior processes for systems using
4374 the Unix @code{ptrace} call in a vanilla way.
4377 @section Native core file Support
4378 @cindex native core files
4381 @findex fetch_core_registers
4382 @item core-aout.c::fetch_core_registers()
4383 Support for reading registers out of a core file. This routine calls
4384 @code{register_addr()}, see below. Now that BFD is used to read core
4385 files, virtually all machines should use @code{core-aout.c}, and should
4386 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4387 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4389 @item core-aout.c::register_addr()
4390 If your @code{nm-@var{xyz}.h} file defines the macro
4391 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4392 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4393 register number @code{regno}. @code{blockend} is the offset within the
4394 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4395 @file{core-aout.c} will define the @code{register_addr()} function and
4396 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4397 you are using the standard @code{fetch_core_registers()}, you will need
4398 to define your own version of @code{register_addr()}, put it into your
4399 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4400 the @code{NATDEPFILES} list. If you have your own
4401 @code{fetch_core_registers()}, you may not need a separate
4402 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4403 implementations simply locate the registers themselves.@refill
4406 When making @value{GDBN} run native on a new operating system, to make it
4407 possible to debug core files, you will need to either write specific
4408 code for parsing your OS's core files, or customize
4409 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4410 machine uses to define the struct of registers that is accessible
4411 (possibly in the u-area) in a core file (rather than
4412 @file{machine/reg.h}), and an include file that defines whatever header
4413 exists on a core file (e.g. the u-area or a @code{struct core}). Then
4414 modify @code{trad_unix_core_file_p} to use these values to set up the
4415 section information for the data segment, stack segment, any other
4416 segments in the core file (perhaps shared library contents or control
4417 information), ``registers'' segment, and if there are two discontiguous
4418 sets of registers (e.g. integer and float), the ``reg2'' segment. This
4419 section information basically delimits areas in the core file in a
4420 standard way, which the section-reading routines in BFD know how to seek
4423 Then back in @value{GDBN}, you need a matching routine called
4424 @code{fetch_core_registers}. If you can use the generic one, it's in
4425 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4426 It will be passed a char pointer to the entire ``registers'' segment,
4427 its length, and a zero; or a char pointer to the entire ``regs2''
4428 segment, its length, and a 2. The routine should suck out the supplied
4429 register values and install them into @value{GDBN}'s ``registers'' array.
4431 If your system uses @file{/proc} to control processes, and uses ELF
4432 format core files, then you may be able to use the same routines for
4433 reading the registers out of processes and out of core files.
4441 @section shared libraries
4443 @section Native Conditionals
4444 @cindex native conditionals
4446 When @value{GDBN} is configured and compiled, various macros are
4447 defined or left undefined, to control compilation when the host and
4448 target systems are the same. These macros should be defined (or left
4449 undefined) in @file{nm-@var{system}.h}.
4453 @findex ATTACH_DETACH
4454 If defined, then @value{GDBN} will include support for the @code{attach} and
4455 @code{detach} commands.
4457 @item CHILD_PREPARE_TO_STORE
4458 @findex CHILD_PREPARE_TO_STORE
4459 If the machine stores all registers at once in the child process, then
4460 define this to ensure that all values are correct. This usually entails
4461 a read from the child.
4463 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4466 @item FETCH_INFERIOR_REGISTERS
4467 @findex FETCH_INFERIOR_REGISTERS
4468 Define this if the native-dependent code will provide its own routines
4469 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4470 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4471 @file{infptrace.c} is included in this configuration, the default
4472 routines in @file{infptrace.c} are used for these functions.
4474 @item FILES_INFO_HOOK
4475 @findex FILES_INFO_HOOK
4476 (Only defined for Convex.)
4480 This macro is normally defined to be the number of the first floating
4481 point register, if the machine has such registers. As such, it would
4482 appear only in target-specific code. However, @file{/proc} support uses this
4483 to decide whether floats are in use on this target.
4485 @item GET_LONGJMP_TARGET
4486 @findex GET_LONGJMP_TARGET
4487 For most machines, this is a target-dependent parameter. On the
4488 DECstation and the Iris, this is a native-dependent parameter, since
4489 @file{setjmp.h} is needed to define it.
4491 This macro determines the target PC address that @code{longjmp} will jump to,
4492 assuming that we have just stopped at a longjmp breakpoint. It takes a
4493 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4494 pointer. It examines the current state of the machine as needed.
4496 @item I386_USE_GENERIC_WATCHPOINTS
4497 An x86-based machine can define this to use the generic x86 watchpoint
4498 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4501 @findex KERNEL_U_ADDR
4502 Define this to the address of the @code{u} structure (the ``user
4503 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4504 needs to know this so that it can subtract this address from absolute
4505 addresses in the upage, that are obtained via ptrace or from core files.
4506 On systems that don't need this value, set it to zero.
4508 @item KERNEL_U_ADDR_BSD
4509 @findex KERNEL_U_ADDR_BSD
4510 Define this to cause @value{GDBN} to determine the address of @code{u} at
4511 runtime, by using Berkeley-style @code{nlist} on the kernel's image in
4514 @item KERNEL_U_ADDR_HPUX
4515 @findex KERNEL_U_ADDR_HPUX
4516 Define this to cause @value{GDBN} to determine the address of @code{u} at
4517 runtime, by using HP-style @code{nlist} on the kernel's image in the
4520 @item ONE_PROCESS_WRITETEXT
4521 @findex ONE_PROCESS_WRITETEXT
4522 Define this to be able to, when a breakpoint insertion fails, warn the
4523 user that another process may be running with the same executable.
4525 @item PREPARE_TO_PROCEED (@var{select_it})
4526 @findex PREPARE_TO_PROCEED
4527 This (ugly) macro allows a native configuration to customize the way the
4528 @code{proceed} function in @file{infrun.c} deals with switching between
4531 In a multi-threaded task we may select another thread and then continue
4532 or step. But if the old thread was stopped at a breakpoint, it will
4533 immediately cause another breakpoint stop without any execution (i.e. it
4534 will report a breakpoint hit incorrectly). So @value{GDBN} must step over it
4537 If defined, @code{PREPARE_TO_PROCEED} should check the current thread
4538 against the thread that reported the most recent event. If a step-over
4539 is required, it returns TRUE. If @var{select_it} is non-zero, it should
4540 reselect the old thread.
4543 @findex PROC_NAME_FMT
4544 Defines the format for the name of a @file{/proc} device. Should be
4545 defined in @file{nm.h} @emph{only} in order to override the default
4546 definition in @file{procfs.c}.
4549 @findex PTRACE_FP_BUG
4550 See @file{mach386-xdep.c}.
4552 @item PTRACE_ARG3_TYPE
4553 @findex PTRACE_ARG3_TYPE
4554 The type of the third argument to the @code{ptrace} system call, if it
4555 exists and is different from @code{int}.
4557 @item REGISTER_U_ADDR
4558 @findex REGISTER_U_ADDR
4559 Defines the offset of the registers in the ``u area''.
4561 @item SHELL_COMMAND_CONCAT
4562 @findex SHELL_COMMAND_CONCAT
4563 If defined, is a string to prefix on the shell command used to start the
4568 If defined, this is the name of the shell to use to run the inferior.
4569 Defaults to @code{"/bin/sh"}.
4571 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4573 Define this to expand into an expression that will cause the symbols in
4574 @var{filename} to be added to @value{GDBN}'s symbol table. If
4575 @var{readsyms} is zero symbols are not read but any necessary low level
4576 processing for @var{filename} is still done.
4578 @item SOLIB_CREATE_INFERIOR_HOOK
4579 @findex SOLIB_CREATE_INFERIOR_HOOK
4580 Define this to expand into any shared-library-relocation code that you
4581 want to be run just after the child process has been forked.
4583 @item START_INFERIOR_TRAPS_EXPECTED
4584 @findex START_INFERIOR_TRAPS_EXPECTED
4585 When starting an inferior, @value{GDBN} normally expects to trap
4587 the shell execs, and once when the program itself execs. If the actual
4588 number of traps is something other than 2, then define this macro to
4589 expand into the number expected.
4591 @item SVR4_SHARED_LIBS
4592 @findex SVR4_SHARED_LIBS
4593 Define this to indicate that SVR4-style shared libraries are in use.
4597 This determines whether small routines in @file{*-tdep.c}, which
4598 translate register values between @value{GDBN}'s internal
4599 representation and the @file{/proc} representation, are compiled.
4602 @findex U_REGS_OFFSET
4603 This is the offset of the registers in the upage. It need only be
4604 defined if the generic ptrace register access routines in
4605 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4606 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4607 the default value from @file{infptrace.c} is good enough, leave it
4610 The default value means that u.u_ar0 @emph{points to} the location of
4611 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4612 that @code{u.u_ar0} @emph{is} the location of the registers.
4616 See @file{objfiles.c}.
4619 @findex DEBUG_PTRACE
4620 Define this to debug @code{ptrace} calls.
4624 @node Support Libraries
4626 @chapter Support Libraries
4631 BFD provides support for @value{GDBN} in several ways:
4634 @item identifying executable and core files
4635 BFD will identify a variety of file types, including a.out, coff, and
4636 several variants thereof, as well as several kinds of core files.
4638 @item access to sections of files
4639 BFD parses the file headers to determine the names, virtual addresses,
4640 sizes, and file locations of all the various named sections in files
4641 (such as the text section or the data section). @value{GDBN} simply
4642 calls BFD to read or write section @var{x} at byte offset @var{y} for
4645 @item specialized core file support
4646 BFD provides routines to determine the failing command name stored in a
4647 core file, the signal with which the program failed, and whether a core
4648 file matches (i.e.@: could be a core dump of) a particular executable
4651 @item locating the symbol information
4652 @value{GDBN} uses an internal interface of BFD to determine where to find the
4653 symbol information in an executable file or symbol-file. @value{GDBN} itself
4654 handles the reading of symbols, since BFD does not ``understand'' debug
4655 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
4660 @cindex opcodes library
4662 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
4663 library because it's also used in binutils, for @file{objdump}).
4672 @cindex regular expressions library
4683 @item SIGN_EXTEND_CHAR
4685 @item SWITCH_ENUM_BUG
4700 This chapter covers topics that are lower-level than the major
4701 algorithms of @value{GDBN}.
4706 Cleanups are a structured way to deal with things that need to be done
4709 When your code does something (e.g., @code{xmalloc} some memory, or
4710 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
4711 the memory or @code{close} the file), it can make a cleanup. The
4712 cleanup will be done at some future point: when the command is finished
4713 and control returns to the top level; when an error occurs and the stack
4714 is unwound; or when your code decides it's time to explicitly perform
4715 cleanups. Alternatively you can elect to discard the cleanups you
4721 @item struct cleanup *@var{old_chain};
4722 Declare a variable which will hold a cleanup chain handle.
4724 @findex make_cleanup
4725 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
4726 Make a cleanup which will cause @var{function} to be called with
4727 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
4728 handle that can later be passed to @code{do_cleanups} or
4729 @code{discard_cleanups}. Unless you are going to call
4730 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
4731 from @code{make_cleanup}.
4734 @item do_cleanups (@var{old_chain});
4735 Do all cleanups added to the chain since the corresponding
4736 @code{make_cleanup} call was made.
4738 @findex discard_cleanups
4739 @item discard_cleanups (@var{old_chain});
4740 Same as @code{do_cleanups} except that it just removes the cleanups from
4741 the chain and does not call the specified functions.
4744 Cleanups are implemented as a chain. The handle returned by
4745 @code{make_cleanups} includes the cleanup passed to the call and any
4746 later cleanups appended to the chain (but not yet discarded or
4750 make_cleanup (a, 0);
4752 struct cleanup *old = make_cleanup (b, 0);
4760 will call @code{c()} and @code{b()} but will not call @code{a()}. The
4761 cleanup that calls @code{a()} will remain in the cleanup chain, and will
4762 be done later unless otherwise discarded.@refill
4764 Your function should explicitly do or discard the cleanups it creates.
4765 Failing to do this leads to non-deterministic behavior since the caller
4766 will arbitrarily do or discard your functions cleanups. This need leads
4767 to two common cleanup styles.
4769 The first style is try/finally. Before it exits, your code-block calls
4770 @code{do_cleanups} with the old cleanup chain and thus ensures that your
4771 code-block's cleanups are always performed. For instance, the following
4772 code-segment avoids a memory leak problem (even when @code{error} is
4773 called and a forced stack unwind occurs) by ensuring that the
4774 @code{xfree} will always be called:
4777 struct cleanup *old = make_cleanup (null_cleanup, 0);
4778 data = xmalloc (sizeof blah);
4779 make_cleanup (xfree, data);
4784 The second style is try/except. Before it exits, your code-block calls
4785 @code{discard_cleanups} with the old cleanup chain and thus ensures that
4786 any created cleanups are not performed. For instance, the following
4787 code segment, ensures that the file will be closed but only if there is
4791 FILE *file = fopen ("afile", "r");
4792 struct cleanup *old = make_cleanup (close_file, file);
4794 discard_cleanups (old);
4798 Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify
4799 that they ``should not be called when cleanups are not in place''. This
4800 means that any actions you need to reverse in the case of an error or
4801 interruption must be on the cleanup chain before you call these
4802 functions, since they might never return to your code (they
4803 @samp{longjmp} instead).
4805 @section Per-architecture module data
4806 @cindex per-architecture module data
4807 @cindex multi-arch data
4808 @cindex data-pointer, per-architecture/per-module
4810 The multi-arch framework includes a mechanism for adding module specific
4811 per-architecture data-pointers to the @code{struct gdbarch} architecture
4814 A module registers one or more per-architecture data-pointers using the
4815 function @code{register_gdbarch_data}:
4817 @deftypefun struct gdbarch_data *register_gdbarch_data (gdbarch_data_init_ftype *@var{init}, gdbarch_data_free_ftype *@var{free})
4819 The @var{init} function is used to obtain an initial value for a
4820 per-architecture data-pointer. The function is called, after the
4821 architecture has been created, when the data-pointer is still
4822 uninitialized (@code{NULL}) and its value has been requested via a call
4823 to @code{gdbarch_data}. A data-pointer can also be initialize
4824 explicitly using @code{set_gdbarch_data}.
4826 The @var{free} function is called when a data-pointer needs to be
4827 destroyed. This occurs when either the corresponding @code{struct
4828 gdbarch} object is being destroyed or when @code{set_gdbarch_data} is
4829 overriding a non-@code{NULL} data-pointer value.
4831 The function @code{register_gdbarch_data} returns a @code{struct
4832 gdbarch_data} that is used to identify the data-pointer that was added
4837 A typical module has @code{init} and @code{free} functions of the form:
4840 static struct gdbarch_data *nozel_handle;
4842 nozel_init (struct gdbarch *gdbarch)
4844 struct nozel *data = XMALLOC (struct nozel);
4850 nozel_free (struct gdbarch *gdbarch, void *data)
4856 Since uninitialized (@code{NULL}) data-pointers are initialized
4857 on-demand, an @code{init} function is free to call other modules that
4858 use data-pointers. Those modules data-pointers will be initialized as
4859 needed. Care should be taken to ensure that the @code{init} call graph
4860 does not contain cycles.
4862 The data-pointer is registered with the call:
4866 _initialize_nozel (void)
4868 nozel_handle = register_gdbarch_data (nozel_init, nozel_free);
4872 The per-architecture data-pointer is accessed using the function:
4874 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
4875 Given the architecture @var{arch} and module data handle
4876 @var{data_handle} (returned by @code{register_gdbarch_data}, this
4877 function returns the current value of the per-architecture data-pointer.
4880 The non-@code{NULL} data-pointer returned by @code{gdbarch_data} should
4881 be saved in a local variable and then used directly:
4885 nozel_total (struct gdbarch *gdbarch)
4888 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
4894 It is also possible to directly initialize the data-pointer using:
4896 @deftypefun void set_gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *handle, void *@var{pointer})
4897 Update the data-pointer corresponding to @var{handle} with the value of
4898 @var{pointer}. If the previous data-pointer value is non-NULL, then it
4899 is freed using data-pointers @var{free} function.
4902 This function is used by modules that require a mechanism for explicitly
4903 setting the per-architecture data-pointer during architecture creation:
4906 /* Called during architecture creation. */
4908 set_gdbarch_nozel (struct gdbarch *gdbarch,
4911 struct nozel *data = XMALLOC (struct nozel);
4913 set_gdbarch_data (gdbarch, nozel_handle, nozel);
4918 /* Default, called when nozel not set by set_gdbarch_nozel(). */
4920 nozel_init (struct gdbarch *gdbarch)
4922 struct nozel *default_nozel = XMALLOC (struc nozel);
4924 return default_nozel;
4930 _initialize_nozel (void)
4932 nozel_handle = register_gdbarch_data (nozel_init, NULL);
4937 Note that an @code{init} function still needs to be registered. It is
4938 used to initialize the data-pointer when the architecture creation phase
4939 fail to set an initial value.
4942 @section Wrapping Output Lines
4943 @cindex line wrap in output
4946 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
4947 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
4948 added in places that would be good breaking points. The utility
4949 routines will take care of actually wrapping if the line width is
4952 The argument to @code{wrap_here} is an indentation string which is
4953 printed @emph{only} if the line breaks there. This argument is saved
4954 away and used later. It must remain valid until the next call to
4955 @code{wrap_here} or until a newline has been printed through the
4956 @code{*_filtered} functions. Don't pass in a local variable and then
4959 It is usually best to call @code{wrap_here} after printing a comma or
4960 space. If you call it before printing a space, make sure that your
4961 indentation properly accounts for the leading space that will print if
4962 the line wraps there.
4964 Any function or set of functions that produce filtered output must
4965 finish by printing a newline, to flush the wrap buffer, before switching
4966 to unfiltered (@code{printf}) output. Symbol reading routines that
4967 print warnings are a good example.
4969 @section @value{GDBN} Coding Standards
4970 @cindex coding standards
4972 @value{GDBN} follows the GNU coding standards, as described in
4973 @file{etc/standards.texi}. This file is also available for anonymous
4974 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
4975 of the standard; in general, when the GNU standard recommends a practice
4976 but does not require it, @value{GDBN} requires it.
4978 @value{GDBN} follows an additional set of coding standards specific to
4979 @value{GDBN}, as described in the following sections.
4984 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
4987 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
4990 @subsection Memory Management
4992 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
4993 @code{calloc}, @code{free} and @code{asprintf}.
4995 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
4996 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
4997 these functions do not return when the memory pool is empty. Instead,
4998 they unwind the stack using cleanups. These functions return
4999 @code{NULL} when requested to allocate a chunk of memory of size zero.
5001 @emph{Pragmatics: By using these functions, the need to check every
5002 memory allocation is removed. These functions provide portable
5005 @value{GDBN} does not use the function @code{free}.
5007 @value{GDBN} uses the function @code{xfree} to return memory to the
5008 memory pool. Consistent with ISO-C, this function ignores a request to
5009 free a @code{NULL} pointer.
5011 @emph{Pragmatics: On some systems @code{free} fails when passed a
5012 @code{NULL} pointer.}
5014 @value{GDBN} can use the non-portable function @code{alloca} for the
5015 allocation of small temporary values (such as strings).
5017 @emph{Pragmatics: This function is very non-portable. Some systems
5018 restrict the memory being allocated to no more than a few kilobytes.}
5020 @value{GDBN} uses the string function @code{xstrdup} and the print
5021 function @code{xasprintf}.
5023 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
5024 functions such as @code{sprintf} are very prone to buffer overflow
5028 @subsection Compiler Warnings
5029 @cindex compiler warnings
5031 With few exceptions, developers should include the configuration option
5032 @samp{--enable-gdb-build-warnings=,-Werror} when building @value{GDBN}.
5033 The exceptions are listed in the file @file{gdb/MAINTAINERS}.
5035 This option causes @value{GDBN} (when built using GCC) to be compiled
5036 with a carefully selected list of compiler warning flags. Any warnings
5037 from those flags being treated as errors.
5039 The current list of warning flags includes:
5043 Since @value{GDBN} coding standard requires all functions to be declared
5044 using a prototype, the flag has the side effect of ensuring that
5045 prototyped functions are always visible with out resorting to
5046 @samp{-Wstrict-prototypes}.
5049 Such code often appears to work except on instruction set architectures
5050 that use register windows.
5057 Since @value{GDBN} uses the @code{format printf} attribute on all
5058 @code{printf} like functions this checks not just @code{printf} calls
5059 but also calls to functions such as @code{fprintf_unfiltered}.
5062 This warning includes uses of the assignment operator within an
5063 @code{if} statement.
5065 @item -Wpointer-arith
5067 @item -Wuninitialized
5070 @emph{Pragmatics: Due to the way that @value{GDBN} is implemented most
5071 functions have unused parameters. Consequently the warning
5072 @samp{-Wunused-parameter} is precluded from the list. The macro
5073 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
5074 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
5075 is being used. The options @samp{-Wall} and @samp{-Wunused} are also
5076 precluded because they both include @samp{-Wunused-parameter}.}
5078 @emph{Pragmatics: @value{GDBN} has not simply accepted the warnings
5079 enabled by @samp{-Wall -Werror -W...}. Instead it is selecting warnings
5080 when and where their benefits can be demonstrated.}
5082 @subsection Formatting
5084 @cindex source code formatting
5085 The standard GNU recommendations for formatting must be followed
5088 A function declaration should not have its name in column zero. A
5089 function definition should have its name in column zero.
5093 static void foo (void);
5101 @emph{Pragmatics: This simplifies scripting. Function definitions can
5102 be found using @samp{^function-name}.}
5104 There must be a space between a function or macro name and the opening
5105 parenthesis of its argument list (except for macro definitions, as
5106 required by C). There must not be a space after an open paren/bracket
5107 or before a close paren/bracket.
5109 While additional whitespace is generally helpful for reading, do not use
5110 more than one blank line to separate blocks, and avoid adding whitespace
5111 after the end of a program line (as of 1/99, some 600 lines had
5112 whitespace after the semicolon). Excess whitespace causes difficulties
5113 for @code{diff} and @code{patch} utilities.
5115 Pointers are declared using the traditional K&R C style:
5129 @subsection Comments
5131 @cindex comment formatting
5132 The standard GNU requirements on comments must be followed strictly.
5134 Block comments must appear in the following form, with no @code{/*}- or
5135 @code{*/}-only lines, and no leading @code{*}:
5138 /* Wait for control to return from inferior to debugger. If inferior
5139 gets a signal, we may decide to start it up again instead of
5140 returning. That is why there is a loop in this function. When
5141 this function actually returns it means the inferior should be left
5142 stopped and @value{GDBN} should read more commands. */
5145 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5146 comment works correctly, and @kbd{M-q} fills the block consistently.)
5148 Put a blank line between the block comments preceding function or
5149 variable definitions, and the definition itself.
5151 In general, put function-body comments on lines by themselves, rather
5152 than trying to fit them into the 20 characters left at the end of a
5153 line, since either the comment or the code will inevitably get longer
5154 than will fit, and then somebody will have to move it anyhow.
5158 @cindex C data types
5159 Code must not depend on the sizes of C data types, the format of the
5160 host's floating point numbers, the alignment of anything, or the order
5161 of evaluation of expressions.
5163 @cindex function usage
5164 Use functions freely. There are only a handful of compute-bound areas
5165 in @value{GDBN} that might be affected by the overhead of a function
5166 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5167 limited by the target interface (whether serial line or system call).
5169 However, use functions with moderation. A thousand one-line functions
5170 are just as hard to understand as a single thousand-line function.
5172 @emph{Macros are bad, M'kay.}
5173 (But if you have to use a macro, make sure that the macro arguments are
5174 protected with parentheses.)
5178 Declarations like @samp{struct foo *} should be used in preference to
5179 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5182 @subsection Function Prototypes
5183 @cindex function prototypes
5185 Prototypes must be used when both @emph{declaring} and @emph{defining}
5186 a function. Prototypes for @value{GDBN} functions must include both the
5187 argument type and name, with the name matching that used in the actual
5188 function definition.
5190 All external functions should have a declaration in a header file that
5191 callers include, except for @code{_initialize_*} functions, which must
5192 be external so that @file{init.c} construction works, but shouldn't be
5193 visible to random source files.
5195 Where a source file needs a forward declaration of a static function,
5196 that declaration must appear in a block near the top of the source file.
5199 @subsection Internal Error Recovery
5201 During its execution, @value{GDBN} can encounter two types of errors.
5202 User errors and internal errors. User errors include not only a user
5203 entering an incorrect command but also problems arising from corrupt
5204 object files and system errors when interacting with the target.
5205 Internal errors include situations where @value{GDBN} has detected, at
5206 run time, a corrupt or erroneous situation.
5208 When reporting an internal error, @value{GDBN} uses
5209 @code{internal_error} and @code{gdb_assert}.
5211 @value{GDBN} must not call @code{abort} or @code{assert}.
5213 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5214 the code detected a user error, recovered from it and issued a
5215 @code{warning} or the code failed to correctly recover from the user
5216 error and issued an @code{internal_error}.}
5218 @subsection File Names
5220 Any file used when building the core of @value{GDBN} must be in lower
5221 case. Any file used when building the core of @value{GDBN} must be 8.3
5222 unique. These requirements apply to both source and generated files.
5224 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5225 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5226 is introduced to the build process both @file{Makefile.in} and
5227 @file{configure.in} need to be modified accordingly. Compare the
5228 convoluted conversion process needed to transform @file{COPYING} into
5229 @file{copying.c} with the conversion needed to transform
5230 @file{version.in} into @file{version.c}.}
5232 Any file non 8.3 compliant file (that is not used when building the core
5233 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5235 @emph{Pragmatics: This is clearly a compromise.}
5237 When @value{GDBN} has a local version of a system header file (ex
5238 @file{string.h}) the file name based on the POSIX header prefixed with
5239 @file{gdb_} (@file{gdb_string.h}).
5241 For other files @samp{-} is used as the separator.
5244 @subsection Include Files
5246 A @file{.c} file should include @file{defs.h} first.
5248 A @file{.c} file should directly include the @code{.h} file of every
5249 declaration and/or definition it directly refers to. It cannot rely on
5252 A @file{.h} file should directly include the @code{.h} file of every
5253 declaration and/or definition it directly refers to. It cannot rely on
5254 indirect inclusion. Exception: The file @file{defs.h} does not need to
5255 be directly included.
5257 An external declaration should only appear in one include file.
5259 An external declaration should never appear in a @code{.c} file.
5260 Exception: a declaration for the @code{_initialize} function that
5261 pacifies @option{-Wmissing-declaration}.
5263 A @code{typedef} definition should only appear in one include file.
5265 An opaque @code{struct} declaration can appear in multiple @file{.h}
5266 files. Where possible, a @file{.h} file should use an opaque
5267 @code{struct} declaration instead of an include.
5269 All @file{.h} files should be wrapped in:
5272 #ifndef INCLUDE_FILE_NAME_H
5273 #define INCLUDE_FILE_NAME_H
5279 @subsection Clean Design and Portable Implementation
5282 In addition to getting the syntax right, there's the little question of
5283 semantics. Some things are done in certain ways in @value{GDBN} because long
5284 experience has shown that the more obvious ways caused various kinds of
5287 @cindex assumptions about targets
5288 You can't assume the byte order of anything that comes from a target
5289 (including @var{value}s, object files, and instructions). Such things
5290 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5291 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5292 such as @code{bfd_get_32}.
5294 You can't assume that you know what interface is being used to talk to
5295 the target system. All references to the target must go through the
5296 current @code{target_ops} vector.
5298 You can't assume that the host and target machines are the same machine
5299 (except in the ``native'' support modules). In particular, you can't
5300 assume that the target machine's header files will be available on the
5301 host machine. Target code must bring along its own header files --
5302 written from scratch or explicitly donated by their owner, to avoid
5306 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5307 to write the code portably than to conditionalize it for various
5310 @cindex system dependencies
5311 New @code{#ifdef}'s which test for specific compilers or manufacturers
5312 or operating systems are unacceptable. All @code{#ifdef}'s should test
5313 for features. The information about which configurations contain which
5314 features should be segregated into the configuration files. Experience
5315 has proven far too often that a feature unique to one particular system
5316 often creeps into other systems; and that a conditional based on some
5317 predefined macro for your current system will become worthless over
5318 time, as new versions of your system come out that behave differently
5319 with regard to this feature.
5321 Adding code that handles specific architectures, operating systems,
5322 target interfaces, or hosts, is not acceptable in generic code.
5324 @cindex portable file name handling
5325 @cindex file names, portability
5326 One particularly notorious area where system dependencies tend to
5327 creep in is handling of file names. The mainline @value{GDBN} code
5328 assumes Posix semantics of file names: absolute file names begin with
5329 a forward slash @file{/}, slashes are used to separate leading
5330 directories, case-sensitive file names. These assumptions are not
5331 necessarily true on non-Posix systems such as MS-Windows. To avoid
5332 system-dependent code where you need to take apart or construct a file
5333 name, use the following portable macros:
5336 @findex HAVE_DOS_BASED_FILE_SYSTEM
5337 @item HAVE_DOS_BASED_FILE_SYSTEM
5338 This preprocessing symbol is defined to a non-zero value on hosts
5339 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5340 symbol to write conditional code which should only be compiled for
5343 @findex IS_DIR_SEPARATOR
5344 @item IS_DIR_SEPARATOR (@var{c})
5345 Evaluates to a non-zero value if @var{c} is a directory separator
5346 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5347 such a character, but on Windows, both @file{/} and @file{\} will
5350 @findex IS_ABSOLUTE_PATH
5351 @item IS_ABSOLUTE_PATH (@var{file})
5352 Evaluates to a non-zero value if @var{file} is an absolute file name.
5353 For Unix and GNU/Linux hosts, a name which begins with a slash
5354 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5355 @file{x:\bar} are also absolute file names.
5357 @findex FILENAME_CMP
5358 @item FILENAME_CMP (@var{f1}, @var{f2})
5359 Calls a function which compares file names @var{f1} and @var{f2} as
5360 appropriate for the underlying host filesystem. For Posix systems,
5361 this simply calls @code{strcmp}; on case-insensitive filesystems it
5362 will call @code{strcasecmp} instead.
5364 @findex DIRNAME_SEPARATOR
5365 @item DIRNAME_SEPARATOR
5366 Evaluates to a character which separates directories in
5367 @code{PATH}-style lists, typically held in environment variables.
5368 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5370 @findex SLASH_STRING
5372 This evaluates to a constant string you should use to produce an
5373 absolute filename from leading directories and the file's basename.
5374 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5375 @code{"\\"} for some Windows-based ports.
5378 In addition to using these macros, be sure to use portable library
5379 functions whenever possible. For example, to extract a directory or a
5380 basename part from a file name, use the @code{dirname} and
5381 @code{basename} library functions (available in @code{libiberty} for
5382 platforms which don't provide them), instead of searching for a slash
5383 with @code{strrchr}.
5385 Another way to generalize @value{GDBN} along a particular interface is with an
5386 attribute struct. For example, @value{GDBN} has been generalized to handle
5387 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5388 by defining the @code{target_ops} structure and having a current target (as
5389 well as a stack of targets below it, for memory references). Whenever
5390 something needs to be done that depends on which remote interface we are
5391 using, a flag in the current target_ops structure is tested (e.g.,
5392 @code{target_has_stack}), or a function is called through a pointer in the
5393 current target_ops structure. In this way, when a new remote interface
5394 is added, only one module needs to be touched---the one that actually
5395 implements the new remote interface. Other examples of
5396 attribute-structs are BFD access to multiple kinds of object file
5397 formats, or @value{GDBN}'s access to multiple source languages.
5399 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5400 the code interfacing between @code{ptrace} and the rest of
5401 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5402 something was very painful. In @value{GDBN} 4.x, these have all been
5403 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5404 with variations between systems the same way any system-independent
5405 file would (hooks, @code{#if defined}, etc.), and machines which are
5406 radically different don't need to use @file{infptrace.c} at all.
5408 All debugging code must be controllable using the @samp{set debug
5409 @var{module}} command. Do not use @code{printf} to print trace
5410 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5411 @code{#ifdef DEBUG}.
5416 @chapter Porting @value{GDBN}
5417 @cindex porting to new machines
5419 Most of the work in making @value{GDBN} compile on a new machine is in
5420 specifying the configuration of the machine. This is done in a
5421 dizzying variety of header files and configuration scripts, which we
5422 hope to make more sensible soon. Let's say your new host is called an
5423 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
5424 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
5425 @samp{sparc-sun-sunos4}). In particular:
5429 In the top level directory, edit @file{config.sub} and add @var{arch},
5430 @var{xvend}, and @var{xos} to the lists of supported architectures,
5431 vendors, and operating systems near the bottom of the file. Also, add
5432 @var{xyz} as an alias that maps to
5433 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
5437 ./config.sub @var{xyz}
5444 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
5448 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
5449 and no error messages.
5452 You need to port BFD, if that hasn't been done already. Porting BFD is
5453 beyond the scope of this manual.
5456 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
5457 your system and set @code{gdb_host} to @var{xyz}, and (unless your
5458 desired target is already available) also edit @file{gdb/configure.tgt},
5459 setting @code{gdb_target} to something appropriate (for instance,
5462 @emph{Maintainer's note: Work in progress. The file
5463 @file{gdb/configure.host} originally needed to be modified when either a
5464 new native target or a new host machine was being added to @value{GDBN}.
5465 Recent changes have removed this requirement. The file now only needs
5466 to be modified when adding a new native configuration. This will likely
5467 changed again in the future.}
5470 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
5471 target-dependent @file{.h} and @file{.c} files used for your
5475 @section Configuring @value{GDBN} for Release
5477 @cindex preparing a release
5478 @cindex making a distribution tarball
5479 From the top level directory (containing @file{gdb}, @file{bfd},
5480 @file{libiberty}, and so on):
5483 make -f Makefile.in gdb.tar.gz
5487 This will properly configure, clean, rebuild any files that are
5488 distributed pre-built (e.g. @file{c-exp.tab.c} or @file{refcard.ps}),
5489 and will then make a tarfile. (If the top level directory has already
5490 been configured, you can just do @code{make gdb.tar.gz} instead.)
5492 This procedure requires:
5500 @code{makeinfo} (texinfo2 level);
5509 @code{yacc} or @code{bison}.
5513 @dots{} and the usual slew of utilities (@code{sed}, @code{tar}, etc.).
5515 @subheading TEMPORARY RELEASE PROCEDURE FOR DOCUMENTATION
5517 @file{gdb.texinfo} is currently marked up using the texinfo-2 macros,
5518 which are not yet a default for anything (but we have to start using
5521 For making paper, the only thing this implies is the right generation of
5522 @file{texinfo.tex} needs to be included in the distribution.
5524 For making info files, however, rather than duplicating the texinfo2
5525 distribution, generate @file{gdb-all.texinfo} locally, and include the
5526 files @file{gdb.info*} in the distribution. Note the plural;
5527 @code{makeinfo} will split the document into one overall file and five
5528 or so included files.
5533 @chapter Releasing @value{GDBN}
5534 @cindex making a new release of gdb
5536 @section Versions and Branches
5538 @subsection Version Identifiers
5540 @value{GDBN}'s version is determined by the file @file{gdb/version.in}.
5542 @value{GDBN}'s mainline uses ISO dates to differentiate between
5543 versions. The CVS repository uses @var{YYYY}-@var{MM}-@var{DD}-cvs
5544 while the corresponding snapshot uses @var{YYYYMMDD}.
5546 @value{GDBN}'s release branch uses a slightly more complicated scheme.
5547 When the branch is first cut, the mainline version identifier is
5548 prefixed with the @var{major}.@var{minor} from of the previous release
5549 series but with .90 appended. As draft releases are drawn from the
5550 branch, the minor minor number (.90) is incremented. Once the first
5551 release (@var{M}.@var{N}) has been made, the version prefix is updated
5552 to @var{M}.@var{N}.0.90 (dot zero, dot ninety). Follow on releases have
5553 an incremented minor minor version number (.0).
5555 Using 5.1 (previous) and 5.2 (current), the example below illustrates a
5556 typical sequence of version identifiers:
5560 final release from previous branch
5561 @item 2002-03-03-cvs
5562 main-line the day the branch is cut
5563 @item 5.1.90-2002-03-03-cvs
5564 corresponding branch version
5566 first draft release candidate
5567 @item 5.1.91-2002-03-17-cvs
5568 updated branch version
5570 second draft release candidate
5571 @item 5.1.92-2002-03-31-cvs
5572 updated branch version
5574 final release candidate (see below)
5577 @item 5.2.0.90-2002-04-07-cvs
5578 updated CVS branch version
5580 second official release
5587 Minor minor minor draft release candidates such as 5.2.0.91 have been
5588 omitted from the example. Such release candidates are, typically, never
5591 For 5.1.93 the bziped tar ball @file{gdb-5.1.93.tar.bz2} is just the
5592 official @file{gdb-5.2.tar} renamed and compressed.
5595 To avoid version conflicts, vendors are expected to modify the file
5596 @file{gdb/version.in} to include a vendor unique alphabetic identifier
5597 (an official @value{GDBN} release never uses alphabetic characters in
5598 its version identifer).
5600 Since @value{GDBN} does not make minor minor minor releases (e.g.,
5601 5.1.0.1) the conflict between that and a minor minor draft release
5602 identifier (e.g., 5.1.0.90) is avoided.
5605 @subsection Branches
5607 @value{GDBN} draws a release series (5.2, 5.2.1, @dots{}) from a single
5608 release branch (gdb_5_2-branch). Since minor minor minor releases
5609 (5.1.0.1) are not made, the need to branch the release branch is avoided
5610 (it also turns out that the effort required for such a a branch and
5611 release is significantly greater than the effort needed to create a new
5612 release from the head of the release branch).
5614 Releases 5.0 and 5.1 used branch and release tags of the form:
5617 gdb_N_M-YYYY-MM-DD-branchpoint
5618 gdb_N_M-YYYY-MM-DD-branch
5619 gdb_M_N-YYYY-MM-DD-release
5622 Release 5.2 is trialing the branch and release tags:
5625 gdb_N_M-YYYY-MM-DD-branchpoint
5627 gdb_M_N-YYYY-MM-DD-release
5630 @emph{Pragmatics: The branchpoint and release tags need to identify when
5631 a branch and release are made. The branch tag, denoting the head of the
5632 branch, does not have this criteria.}
5635 @section Branch Commit Policy
5637 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
5638 5.1 and 5.2 all used the below:
5642 The @file{gdb/MAINTAINERS} file still holds.
5644 Don't fix something on the branch unless/until it is also fixed in the
5645 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
5646 file is better than committing a hack.
5648 When considering a patch for the branch, suggested criteria include:
5649 Does it fix a build? Does it fix the sequence @kbd{break main; run}
5650 when debugging a static binary?
5652 The further a change is from the core of @value{GDBN}, the less likely
5653 the change will worry anyone (e.g., target specific code).
5655 Only post a proposal to change the core of @value{GDBN} after you've
5656 sent individual bribes to all the people listed in the
5657 @file{MAINTAINERS} file @t{;-)}
5660 @emph{Pragmatics: Provided updates are restricted to non-core
5661 functionality there is little chance that a broken change will be fatal.
5662 This means that changes such as adding a new architectures or (within
5663 reason) support for a new host are considered acceptable.}
5666 @section Obsoleting code
5668 Before anything else, poke the other developers (and around the source
5669 code) to see if there is anything that can be removed from @value{GDBN}
5670 (an old target, an unused file).
5672 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
5673 line. Doing this means that it is easy to identify something that has
5674 been obsoleted when greping through the sources.
5676 The process is done in stages --- this is mainly to ensure that the
5677 wider @value{GDBN} community has a reasonable opportunity to respond.
5678 Remember, everything on the Internet takes a week.
5682 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
5683 list} Creating a bug report to track the task's state, is also highly
5688 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
5689 Announcement mailing list}.
5693 Go through and edit all relevant files and lines so that they are
5694 prefixed with the word @code{OBSOLETE}.
5696 Wait until the next GDB version, containing this obsolete code, has been
5699 Remove the obsolete code.
5703 @emph{Maintainer note: While removing old code is regrettable it is
5704 hopefully better for @value{GDBN}'s long term development. Firstly it
5705 helps the developers by removing code that is either no longer relevant
5706 or simply wrong. Secondly since it removes any history associated with
5707 the file (effectively clearing the slate) the developer has a much freer
5708 hand when it comes to fixing broken files.}
5712 @section Before the Branch
5714 The most important objective at this stage is to find and fix simple
5715 changes that become a pain to track once the branch is created. For
5716 instance, configuration problems that stop @value{GDBN} from even
5717 building. If you can't get the problem fixed, document it in the
5718 @file{gdb/PROBLEMS} file.
5720 @subheading Prompt for @file{gdb/NEWS}
5722 People always forget. Send a post reminding them but also if you know
5723 something interesting happened add it yourself. The @code{schedule}
5724 script will mention this in its e-mail.
5726 @subheading Review @file{gdb/README}
5728 Grab one of the nightly snapshots and then walk through the
5729 @file{gdb/README} looking for anything that can be improved. The
5730 @code{schedule} script will mention this in its e-mail.
5732 @subheading Refresh any imported files.
5734 A number of files are taken from external repositories. They include:
5738 @file{texinfo/texinfo.tex}
5740 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
5743 @file{etc/standards.texi}, @file{etc/make-stds.texi}
5746 @subheading Check the ARI
5748 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
5749 (Awk Regression Index ;-) that checks for a number of errors and coding
5750 conventions. The checks include things like using @code{malloc} instead
5751 of @code{xmalloc} and file naming problems. There shouldn't be any
5754 @subsection Review the bug data base
5756 Close anything obviously fixed.
5758 @subsection Check all cross targets build
5760 The targets are listed in @file{gdb/MAINTAINERS}.
5763 @section Cut the Branch
5765 @subheading Create the branch
5770 $ V=`echo $v | sed 's/\./_/g'`
5771 $ D=`date -u +%Y-%m-%d`
5774 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5775 -D $D-gmt gdb_$V-$D-branchpoint insight+dejagnu
5776 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
5777 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight+dejagnu
5780 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5781 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight+dejagnu
5782 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5783 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight+dejagnu
5791 by using @kbd{-D YYYY-MM-DD-gmt} the branch is forced to an exact
5794 the trunk is first taged so that the branch point can easily be found
5796 Insight (which includes GDB) and dejagnu are all tagged at the same time
5798 @file{version.in} gets bumped to avoid version number conflicts
5800 the reading of @file{.cvsrc} is disabled using @file{-f}
5803 @subheading Update @file{version.in}
5808 $ V=`echo $v | sed 's/\./_/g'`
5812 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
5813 -r gdb_$V-branch src/gdb/version.in
5814 cvs -f -d :ext:sources.redhat.com:/cvs/src co
5815 -r gdb_5_2-branch src/gdb/version.in
5817 U src/gdb/version.in
5819 $ echo $u.90-0000-00-00-cvs > version.in
5821 5.1.90-0000-00-00-cvs
5822 $ cvs -f commit version.in
5827 @file{0000-00-00} is used as a date to pump prime the version.in update
5830 @file{.90} and the previous branch version are used as fairly arbitrary
5831 initial branch version number
5835 @subheading Update the web and news pages
5839 @subheading Tweak cron to track the new branch
5841 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
5842 This file needs to be updated so that:
5846 a daily timestamp is added to the file @file{version.in}
5848 the new branch is included in the snapshot process
5852 See the file @file{gdbadmin/cron/README} for how to install the updated
5855 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
5856 any changes. That file is copied to both the branch/ and current/
5857 snapshot directories.
5860 @subheading Update the NEWS and README files
5862 The @file{NEWS} file needs to be updated so that on the branch it refers
5863 to @emph{changes in the current release} while on the trunk it also
5864 refers to @emph{changes since the current release}.
5866 The @file{README} file needs to be updated so that it refers to the
5869 @subheading Post the branch info
5871 Send an announcement to the mailing lists:
5875 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
5877 @email{gdb@@sources.redhat.com, GDB Discsussion mailing list} and
5878 @email{gdb-testers@@sources.redhat.com, GDB Discsussion mailing list}
5881 @emph{Pragmatics: The branch creation is sent to the announce list to
5882 ensure that people people not subscribed to the higher volume discussion
5885 The announcement should include:
5891 how to check out the branch using CVS
5893 the date/number of weeks until the release
5895 the branch commit policy
5899 @section Stabilize the branch
5901 Something goes here.
5903 @section Create a Release
5905 The process of creating and then making available a release is broken
5906 down into a number of stages. The first part addresses the technical
5907 process of creating a releasable tar ball. The later stages address the
5908 process of releasing that tar ball.
5910 When making a release candidate just the first section is needed.
5912 @subsection Create a release candidate
5914 The objective at this stage is to create a set of tar balls that can be
5915 made available as a formal release (or as a less formal release
5918 @subsubheading Freeze the branch
5920 Send out an e-mail notifying everyone that the branch is frozen to
5921 @email{gdb-patches@@sources.redhat.com}.
5923 @subsubheading Establish a few defaults.
5928 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
5930 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5934 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5936 /home/gdbadmin/bin/autoconf
5945 Check the @code{autoconf} version carefully. You want to be using the
5946 version taken from the @file{binutils} snapshot directory, which can be
5947 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
5948 unlikely that a system installed version of @code{autoconf} (e.g.,
5949 @file{/usr/bin/autoconf}) is correct.
5952 @subsubheading Check out the relevant modules:
5955 $ for m in gdb insight dejagnu
5957 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
5967 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
5968 any confusion between what is written here and what your local
5969 @code{cvs} really does.
5972 @subsubheading Update relevant files.
5978 Major releases get their comments added as part of the mainline. Minor
5979 releases should probably mention any significant bugs that were fixed.
5981 Don't forget to include the @file{ChangeLog} entry.
5984 $ emacs gdb/src/gdb/NEWS
5989 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
5990 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5995 You'll need to update:
6007 $ emacs gdb/src/gdb/README
6012 $ cp gdb/src/gdb/README insight/src/gdb/README
6013 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6016 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
6017 before the initial branch was cut so just a simple substitute is needed
6020 @emph{Maintainer note: Other projects generate @file{README} and
6021 @file{INSTALL} from the core documentation. This might be worth
6024 @item gdb/version.in
6027 $ echo $v > gdb/src/gdb/version.in
6028 $ cat gdb/src/gdb/version.in
6030 $ emacs gdb/src/gdb/version.in
6033 ... Bump to version ...
6035 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
6036 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
6039 @item dejagnu/src/dejagnu/configure.in
6041 Dejagnu is more complicated. The version number is a parameter to
6042 @code{AM_INIT_AUTOMAKE}. Tweak it to read something like gdb-5.1.91.
6044 Don't forget to re-generate @file{configure}.
6046 Don't forget to include a @file{ChangeLog} entry.
6049 $ emacs dejagnu/src/dejagnu/configure.in
6054 $ ( cd dejagnu/src/dejagnu && autoconf )
6059 @subsubheading Do the dirty work
6061 This is identical to the process used to create the daily snapshot.
6064 $ for m in gdb insight
6066 ( cd $m/src && gmake -f Makefile.in $m.tar )
6068 $ ( m=dejagnu; cd $m/src && gmake -f Makefile.in $m.tar.bz2 )
6071 @subsubheading Check the source files
6073 You're looking for files that have mysteriously disappeared.
6074 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
6075 for the @file{version.in} update @kbd{cronjob}.
6078 $ ( cd gdb/src && cvs -f -q -n update )
6082 @dots{} lots of generated files @dots{}
6087 @dots{} lots of generated files @dots{}
6092 @emph{Don't worry about the @file{gdb.info-??} or
6093 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
6094 was also generated only something strange with CVS means that they
6095 didn't get supressed). Fixing it would be nice though.}
6097 @subsubheading Create compressed versions of the release
6103 dejagnu/ dejagnu-gdb-5.2.tar.bz2 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
6104 $ for m in gdb insight
6106 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
6107 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
6117 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
6118 in that mode, @code{gzip} does not know the name of the file and, hence,
6119 can not include it in the compressed file. This is also why the release
6120 process runs @code{tar} and @code{bzip2} as separate passes.
6123 @subsection Sanity check the tar ball
6125 Pick a popular machine (Solaris/PPC?) and try the build on that.
6128 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
6133 $ ./gdb/gdb ./gdb/gdb
6137 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6139 Starting program: /tmp/gdb-5.2/gdb/gdb
6141 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6142 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6144 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6148 @subsection Make a release candidate available
6150 If this is a release candidate then the only remaining steps are:
6154 Commit @file{version.in} and @file{ChangeLog}
6156 Tweak @file{version.in} (and @file{ChangeLog} to read
6157 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6158 process can restart.
6160 Make the release candidate available in
6161 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6163 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6164 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6167 @subsection Make a formal release available
6169 (And you thought all that was required was to post an e-mail.)
6171 @subsubheading Install on sware
6173 Copy the new files to both the release and the old release directory:
6176 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6177 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6181 Clean up the releases directory so that only the most recent releases
6182 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6185 $ cd ~ftp/pub/gdb/releases
6190 Update the file @file{README} and @file{.message} in the releases
6197 $ ln README .message
6200 @subsubheading Update the web pages.
6204 @item htdocs/download/ANNOUNCEMENT
6205 This file, which is posted as the official announcement, includes:
6208 General announcement
6210 News. If making an @var{M}.@var{N}.1 release, retain the news from
6211 earlier @var{M}.@var{N} release.
6216 @item htdocs/index.html
6217 @itemx htdocs/news/index.html
6218 @itemx htdocs/download/index.html
6219 These files include:
6222 announcement of the most recent release
6224 news entry (remember to update both the top level and the news directory).
6226 These pages also need to be regenerate using @code{index.sh}.
6228 @item download/onlinedocs/
6229 You need to find the magic command that is used to generate the online
6230 docs from the @file{.tar.bz2}. The best way is to look in the output
6231 from one of the nightly @code{cron} jobs and then just edit accordingly.
6235 $ ~/ss/update-web-docs \
6236 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6238 /www/sourceware/htdocs/gdb/download/onlinedocs \
6243 Just like the online documentation. Something like:
6246 $ /bin/sh ~/ss/update-web-ari \
6247 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6249 /www/sourceware/htdocs/gdb/download/ari \
6255 @subsubheading Shadow the pages onto gnu
6257 Something goes here.
6260 @subsubheading Install the @value{GDBN} tar ball on GNU
6262 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6263 @file{~ftp/gnu/gdb}.
6265 @subsubheading Make the @file{ANNOUNCEMENT}
6267 Post the @file{ANNOUNCEMENT} file you created above to:
6271 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6273 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6274 day or so to let things get out)
6276 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6281 The release is out but you're still not finished.
6283 @subsubheading Commit outstanding changes
6285 In particular you'll need to commit any changes to:
6289 @file{gdb/ChangeLog}
6291 @file{gdb/version.in}
6298 @subsubheading Tag the release
6303 $ d=`date -u +%Y-%m-%d`
6306 $ ( cd insight/src/gdb && cvs -f -q update )
6307 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6310 Insight is used since that contains more of the release than
6311 @value{GDBN} (@code{dejagnu} doesn't get tagged but I think we can live
6314 @subsubheading Mention the release on the trunk
6316 Just put something in the @file{ChangeLog} so that the trunk also
6317 indicates when the release was made.
6319 @subsubheading Restart @file{gdb/version.in}
6321 If @file{gdb/version.in} does not contain an ISO date such as
6322 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6323 committed all the release changes it can be set to
6324 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6325 is important - it affects the snapshot process).
6327 Don't forget the @file{ChangeLog}.
6329 @subsubheading Merge into trunk
6331 The files committed to the branch may also need changes merged into the
6334 @subsubheading Revise the release schedule
6336 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
6337 Discussion List} with an updated announcement. The schedule can be
6338 generated by running:
6341 $ ~/ss/schedule `date +%s` schedule
6345 The first parameter is approximate date/time in seconds (from the epoch)
6346 of the most recent release.
6348 Also update the schedule @code{cronjob}.
6350 @section Post release
6352 Remove any @code{OBSOLETE} code.
6359 The testsuite is an important component of the @value{GDBN} package.
6360 While it is always worthwhile to encourage user testing, in practice
6361 this is rarely sufficient; users typically use only a small subset of
6362 the available commands, and it has proven all too common for a change
6363 to cause a significant regression that went unnoticed for some time.
6365 The @value{GDBN} testsuite uses the DejaGNU testing framework.
6366 DejaGNU is built using @code{Tcl} and @code{expect}. The tests
6367 themselves are calls to various @code{Tcl} procs; the framework runs all the
6368 procs and summarizes the passes and fails.
6370 @section Using the Testsuite
6372 @cindex running the test suite
6373 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
6374 testsuite's objdir) and type @code{make check}. This just sets up some
6375 environment variables and invokes DejaGNU's @code{runtest} script. While
6376 the testsuite is running, you'll get mentions of which test file is in use,
6377 and a mention of any unexpected passes or fails. When the testsuite is
6378 finished, you'll get a summary that looks like this:
6383 # of expected passes 6016
6384 # of unexpected failures 58
6385 # of unexpected successes 5
6386 # of expected failures 183
6387 # of unresolved testcases 3
6388 # of untested testcases 5
6391 The ideal test run consists of expected passes only; however, reality
6392 conspires to keep us from this ideal. Unexpected failures indicate
6393 real problems, whether in @value{GDBN} or in the testsuite. Expected
6394 failures are still failures, but ones which have been decided are too
6395 hard to deal with at the time; for instance, a test case might work
6396 everywhere except on AIX, and there is no prospect of the AIX case
6397 being fixed in the near future. Expected failures should not be added
6398 lightly, since you may be masking serious bugs in @value{GDBN}.
6399 Unexpected successes are expected fails that are passing for some
6400 reason, while unresolved and untested cases often indicate some minor
6401 catastrophe, such as the compiler being unable to deal with a test
6404 When making any significant change to @value{GDBN}, you should run the
6405 testsuite before and after the change, to confirm that there are no
6406 regressions. Note that truly complete testing would require that you
6407 run the testsuite with all supported configurations and a variety of
6408 compilers; however this is more than really necessary. In many cases
6409 testing with a single configuration is sufficient. Other useful
6410 options are to test one big-endian (Sparc) and one little-endian (x86)
6411 host, a cross config with a builtin simulator (powerpc-eabi,
6412 mips-elf), or a 64-bit host (Alpha).
6414 If you add new functionality to @value{GDBN}, please consider adding
6415 tests for it as well; this way future @value{GDBN} hackers can detect
6416 and fix their changes that break the functionality you added.
6417 Similarly, if you fix a bug that was not previously reported as a test
6418 failure, please add a test case for it. Some cases are extremely
6419 difficult to test, such as code that handles host OS failures or bugs
6420 in particular versions of compilers, and it's OK not to try to write
6421 tests for all of those.
6423 @section Testsuite Organization
6425 @cindex test suite organization
6426 The testsuite is entirely contained in @file{gdb/testsuite}. While the
6427 testsuite includes some makefiles and configury, these are very minimal,
6428 and used for little besides cleaning up, since the tests themselves
6429 handle the compilation of the programs that @value{GDBN} will run. The file
6430 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
6431 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
6432 configuration-specific files, typically used for special-purpose
6433 definitions of procs like @code{gdb_load} and @code{gdb_start}.
6435 The tests themselves are to be found in @file{testsuite/gdb.*} and
6436 subdirectories of those. The names of the test files must always end
6437 with @file{.exp}. DejaGNU collects the test files by wildcarding
6438 in the test directories, so both subdirectories and individual files
6439 get chosen and run in alphabetical order.
6441 The following table lists the main types of subdirectories and what they
6442 are for. Since DejaGNU finds test files no matter where they are
6443 located, and since each test file sets up its own compilation and
6444 execution environment, this organization is simply for convenience and
6449 This is the base testsuite. The tests in it should apply to all
6450 configurations of @value{GDBN} (but generic native-only tests may live here).
6451 The test programs should be in the subset of C that is valid K&R,
6452 ANSI/ISO, and C++ (@code{#ifdef}s are allowed if necessary, for instance
6455 @item gdb.@var{lang}
6456 Language-specific tests for any language @var{lang} besides C. Examples are
6457 @file{gdb.c++} and @file{gdb.java}.
6459 @item gdb.@var{platform}
6460 Non-portable tests. The tests are specific to a specific configuration
6461 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
6464 @item gdb.@var{compiler}
6465 Tests specific to a particular compiler. As of this writing (June
6466 1999), there aren't currently any groups of tests in this category that
6467 couldn't just as sensibly be made platform-specific, but one could
6468 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
6471 @item gdb.@var{subsystem}
6472 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
6473 instance, @file{gdb.disasm} exercises various disassemblers, while
6474 @file{gdb.stabs} tests pathways through the stabs symbol reader.
6477 @section Writing Tests
6478 @cindex writing tests
6480 In many areas, the @value{GDBN} tests are already quite comprehensive; you
6481 should be able to copy existing tests to handle new cases.
6483 You should try to use @code{gdb_test} whenever possible, since it
6484 includes cases to handle all the unexpected errors that might happen.
6485 However, it doesn't cost anything to add new test procedures; for
6486 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
6487 calls @code{gdb_test} multiple times.
6489 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
6490 necessary, such as when @value{GDBN} has several valid responses to a command.
6492 The source language programs do @emph{not} need to be in a consistent
6493 style. Since @value{GDBN} is used to debug programs written in many different
6494 styles, it's worth having a mix of styles in the testsuite; for
6495 instance, some @value{GDBN} bugs involving the display of source lines would
6496 never manifest themselves if the programs used GNU coding style
6503 Check the @file{README} file, it often has useful information that does not
6504 appear anywhere else in the directory.
6507 * Getting Started:: Getting started working on @value{GDBN}
6508 * Debugging GDB:: Debugging @value{GDBN} with itself
6511 @node Getting Started,,, Hints
6513 @section Getting Started
6515 @value{GDBN} is a large and complicated program, and if you first starting to
6516 work on it, it can be hard to know where to start. Fortunately, if you
6517 know how to go about it, there are ways to figure out what is going on.
6519 This manual, the @value{GDBN} Internals manual, has information which applies
6520 generally to many parts of @value{GDBN}.
6522 Information about particular functions or data structures are located in
6523 comments with those functions or data structures. If you run across a
6524 function or a global variable which does not have a comment correctly
6525 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
6526 free to submit a bug report, with a suggested comment if you can figure
6527 out what the comment should say. If you find a comment which is
6528 actually wrong, be especially sure to report that.
6530 Comments explaining the function of macros defined in host, target, or
6531 native dependent files can be in several places. Sometimes they are
6532 repeated every place the macro is defined. Sometimes they are where the
6533 macro is used. Sometimes there is a header file which supplies a
6534 default definition of the macro, and the comment is there. This manual
6535 also documents all the available macros.
6536 @c (@pxref{Host Conditionals}, @pxref{Target
6537 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
6540 Start with the header files. Once you have some idea of how
6541 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
6542 @file{gdbtypes.h}), you will find it much easier to understand the
6543 code which uses and creates those symbol tables.
6545 You may wish to process the information you are getting somehow, to
6546 enhance your understanding of it. Summarize it, translate it to another
6547 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
6548 the code to predict what a test case would do and write the test case
6549 and verify your prediction, etc. If you are reading code and your eyes
6550 are starting to glaze over, this is a sign you need to use a more active
6553 Once you have a part of @value{GDBN} to start with, you can find more
6554 specifically the part you are looking for by stepping through each
6555 function with the @code{next} command. Do not use @code{step} or you
6556 will quickly get distracted; when the function you are stepping through
6557 calls another function try only to get a big-picture understanding
6558 (perhaps using the comment at the beginning of the function being
6559 called) of what it does. This way you can identify which of the
6560 functions being called by the function you are stepping through is the
6561 one which you are interested in. You may need to examine the data
6562 structures generated at each stage, with reference to the comments in
6563 the header files explaining what the data structures are supposed to
6566 Of course, this same technique can be used if you are just reading the
6567 code, rather than actually stepping through it. The same general
6568 principle applies---when the code you are looking at calls something
6569 else, just try to understand generally what the code being called does,
6570 rather than worrying about all its details.
6572 @cindex command implementation
6573 A good place to start when tracking down some particular area is with
6574 a command which invokes that feature. Suppose you want to know how
6575 single-stepping works. As a @value{GDBN} user, you know that the
6576 @code{step} command invokes single-stepping. The command is invoked
6577 via command tables (see @file{command.h}); by convention the function
6578 which actually performs the command is formed by taking the name of
6579 the command and adding @samp{_command}, or in the case of an
6580 @code{info} subcommand, @samp{_info}. For example, the @code{step}
6581 command invokes the @code{step_command} function and the @code{info
6582 display} command invokes @code{display_info}. When this convention is
6583 not followed, you might have to use @code{grep} or @kbd{M-x
6584 tags-search} in emacs, or run @value{GDBN} on itself and set a
6585 breakpoint in @code{execute_command}.
6587 @cindex @code{bug-gdb} mailing list
6588 If all of the above fail, it may be appropriate to ask for information
6589 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
6590 wondering if anyone could give me some tips about understanding
6591 @value{GDBN}''---if we had some magic secret we would put it in this manual.
6592 Suggestions for improving the manual are always welcome, of course.
6594 @node Debugging GDB,,,Hints
6596 @section Debugging @value{GDBN} with itself
6597 @cindex debugging @value{GDBN}
6599 If @value{GDBN} is limping on your machine, this is the preferred way to get it
6600 fully functional. Be warned that in some ancient Unix systems, like
6601 Ultrix 4.2, a program can't be running in one process while it is being
6602 debugged in another. Rather than typing the command @kbd{@w{./gdb
6603 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
6604 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
6606 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
6607 @file{.gdbinit} file that sets up some simple things to make debugging
6608 gdb easier. The @code{info} command, when executed without a subcommand
6609 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
6610 gdb. See @file{.gdbinit} for details.
6612 If you use emacs, you will probably want to do a @code{make TAGS} after
6613 you configure your distribution; this will put the machine dependent
6614 routines for your local machine where they will be accessed first by
6617 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
6618 have run @code{fixincludes} if you are compiling with gcc.
6620 @section Submitting Patches
6622 @cindex submitting patches
6623 Thanks for thinking of offering your changes back to the community of
6624 @value{GDBN} users. In general we like to get well designed enhancements.
6625 Thanks also for checking in advance about the best way to transfer the
6628 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
6629 This manual summarizes what we believe to be clean design for @value{GDBN}.
6631 If the maintainers don't have time to put the patch in when it arrives,
6632 or if there is any question about a patch, it goes into a large queue
6633 with everyone else's patches and bug reports.
6635 @cindex legal papers for code contributions
6636 The legal issue is that to incorporate substantial changes requires a
6637 copyright assignment from you and/or your employer, granting ownership
6638 of the changes to the Free Software Foundation. You can get the
6639 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
6640 and asking for it. We recommend that people write in "All programs
6641 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
6642 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
6644 contributed with only one piece of legalese pushed through the
6645 bureaucracy and filed with the FSF. We can't start merging changes until
6646 this paperwork is received by the FSF (their rules, which we follow
6647 since we maintain it for them).
6649 Technically, the easiest way to receive changes is to receive each
6650 feature as a small context diff or unidiff, suitable for @code{patch}.
6651 Each message sent to me should include the changes to C code and
6652 header files for a single feature, plus @file{ChangeLog} entries for
6653 each directory where files were modified, and diffs for any changes
6654 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
6655 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
6656 single feature, they can be split down into multiple messages.
6658 In this way, if we read and like the feature, we can add it to the
6659 sources with a single patch command, do some testing, and check it in.
6660 If you leave out the @file{ChangeLog}, we have to write one. If you leave
6661 out the doc, we have to puzzle out what needs documenting. Etc., etc.
6663 The reason to send each change in a separate message is that we will not
6664 install some of the changes. They'll be returned to you with questions
6665 or comments. If we're doing our job correctly, the message back to you
6666 will say what you have to fix in order to make the change acceptable.
6667 The reason to have separate messages for separate features is so that
6668 the acceptable changes can be installed while one or more changes are
6669 being reworked. If multiple features are sent in a single message, we
6670 tend to not put in the effort to sort out the acceptable changes from
6671 the unacceptable, so none of the features get installed until all are
6674 If this sounds painful or authoritarian, well, it is. But we get a lot
6675 of bug reports and a lot of patches, and many of them don't get
6676 installed because we don't have the time to finish the job that the bug
6677 reporter or the contributor could have done. Patches that arrive
6678 complete, working, and well designed, tend to get installed on the day
6679 they arrive. The others go into a queue and get installed as time
6680 permits, which, since the maintainers have many demands to meet, may not
6681 be for quite some time.
6683 Please send patches directly to
6684 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
6686 @section Obsolete Conditionals
6687 @cindex obsolete code
6689 Fragments of old code in @value{GDBN} sometimes reference or set the following
6690 configuration macros. They should not be used by new code, and old uses
6691 should be removed as those parts of the debugger are otherwise touched.
6694 @item STACK_END_ADDR
6695 This macro used to define where the end of the stack appeared, for use
6696 in interpreting core file formats that don't record this address in the
6697 core file itself. This information is now configured in BFD, and @value{GDBN}
6698 gets the info portably from there. The values in @value{GDBN}'s configuration
6699 files should be moved into BFD configuration files (if needed there),
6700 and deleted from all of @value{GDBN}'s config files.
6702 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
6703 is so old that it has never been converted to use BFD. Now that's old!