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 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001,2002,2003
12 Free Software Foundation, Inc.
13 Contributed by Cygnus Solutions. Written by John Gilmore.
14 Second Edition by Stan Shebs.
16 Permission is granted to copy, distribute and/or modify this document
17 under the terms of the GNU Free Documentation License, Version 1.1 or
18 any later version published by the Free Software Foundation; with no
19 Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
20 and with the Back-Cover Texts as in (a) below.
22 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
23 this GNU Manual, like GNU software. Copies published by the Free
24 Software Foundation raise funds for GNU development.''
27 @setchapternewpage off
28 @settitle @value{GDBN} Internals
34 @title @value{GDBN} Internals
35 @subtitle{A guide to the internals of the GNU debugger}
37 @author Cygnus Solutions
38 @author Second Edition:
40 @author Cygnus Solutions
43 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
44 \xdef\manvers{\$Revision$} % For use in headers, footers too
46 \hfill Cygnus Solutions\par
48 \hfill \TeX{}info \texinfoversion\par
52 @vskip 0pt plus 1filll
53 Copyright @copyright{} 1990,1991,1992,1993,1994,1996,1998,1999,2000,2001,
54 2002, 2003 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 a
257 new @value{GDBN} frame struct, and then @code{INIT_EXTRA_FRAME_INFO} and
258 @code{DEPRECATED_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.
1847 @c If defined, these are the producer strings in a DWARF 1 file. All of
1848 @c these have reasonable defaults already.
1850 The DWARF 1 reader is in @file{dwarfread.c}.
1854 @cindex DWARF 2 debugging info
1855 DWARF 2 is an improved but incompatible version of DWARF 1.
1857 The DWARF 2 reader is in @file{dwarf2read.c}.
1861 @cindex SOM debugging info
1862 Like COFF, the SOM definition includes debugging information.
1864 @section Adding a New Symbol Reader to @value{GDBN}
1866 @cindex adding debugging info reader
1867 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
1868 there is probably little to be done.
1870 If you need to add a new object file format, you must first add it to
1871 BFD. This is beyond the scope of this document.
1873 You must then arrange for the BFD code to provide access to the
1874 debugging symbols. Generally @value{GDBN} will have to call swapping routines
1875 from BFD and a few other BFD internal routines to locate the debugging
1876 information. As much as possible, @value{GDBN} should not depend on the BFD
1877 internal data structures.
1879 For some targets (e.g., COFF), there is a special transfer vector used
1880 to call swapping routines, since the external data structures on various
1881 platforms have different sizes and layouts. Specialized routines that
1882 will only ever be implemented by one object file format may be called
1883 directly. This interface should be described in a file
1884 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
1887 @node Language Support
1889 @chapter Language Support
1891 @cindex language support
1892 @value{GDBN}'s language support is mainly driven by the symbol reader,
1893 although it is possible for the user to set the source language
1896 @value{GDBN} chooses the source language by looking at the extension
1897 of the file recorded in the debug info; @file{.c} means C, @file{.f}
1898 means Fortran, etc. It may also use a special-purpose language
1899 identifier if the debug format supports it, like with DWARF.
1901 @section Adding a Source Language to @value{GDBN}
1903 @cindex adding source language
1904 To add other languages to @value{GDBN}'s expression parser, follow the
1908 @item Create the expression parser.
1910 @cindex expression parser
1911 This should reside in a file @file{@var{lang}-exp.y}. Routines for
1912 building parsed expressions into a @code{union exp_element} list are in
1915 @cindex language parser
1916 Since we can't depend upon everyone having Bison, and YACC produces
1917 parsers that define a bunch of global names, the following lines
1918 @strong{must} be included at the top of the YACC parser, to prevent the
1919 various parsers from defining the same global names:
1922 #define yyparse @var{lang}_parse
1923 #define yylex @var{lang}_lex
1924 #define yyerror @var{lang}_error
1925 #define yylval @var{lang}_lval
1926 #define yychar @var{lang}_char
1927 #define yydebug @var{lang}_debug
1928 #define yypact @var{lang}_pact
1929 #define yyr1 @var{lang}_r1
1930 #define yyr2 @var{lang}_r2
1931 #define yydef @var{lang}_def
1932 #define yychk @var{lang}_chk
1933 #define yypgo @var{lang}_pgo
1934 #define yyact @var{lang}_act
1935 #define yyexca @var{lang}_exca
1936 #define yyerrflag @var{lang}_errflag
1937 #define yynerrs @var{lang}_nerrs
1940 At the bottom of your parser, define a @code{struct language_defn} and
1941 initialize it with the right values for your language. Define an
1942 @code{initialize_@var{lang}} routine and have it call
1943 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
1944 that your language exists. You'll need some other supporting variables
1945 and functions, which will be used via pointers from your
1946 @code{@var{lang}_language_defn}. See the declaration of @code{struct
1947 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
1948 for more information.
1950 @item Add any evaluation routines, if necessary
1952 @cindex expression evaluation routines
1953 @findex evaluate_subexp
1954 @findex prefixify_subexp
1955 @findex length_of_subexp
1956 If you need new opcodes (that represent the operations of the language),
1957 add them to the enumerated type in @file{expression.h}. Add support
1958 code for these operations in the @code{evaluate_subexp} function
1959 defined in the file @file{eval.c}. Add cases
1960 for new opcodes in two functions from @file{parse.c}:
1961 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
1962 the number of @code{exp_element}s that a given operation takes up.
1964 @item Update some existing code
1966 Add an enumerated identifier for your language to the enumerated type
1967 @code{enum language} in @file{defs.h}.
1969 Update the routines in @file{language.c} so your language is included.
1970 These routines include type predicates and such, which (in some cases)
1971 are language dependent. If your language does not appear in the switch
1972 statement, an error is reported.
1974 @vindex current_language
1975 Also included in @file{language.c} is the code that updates the variable
1976 @code{current_language}, and the routines that translate the
1977 @code{language_@var{lang}} enumerated identifier into a printable
1980 @findex _initialize_language
1981 Update the function @code{_initialize_language} to include your
1982 language. This function picks the default language upon startup, so is
1983 dependent upon which languages that @value{GDBN} is built for.
1985 @findex allocate_symtab
1986 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
1987 code so that the language of each symtab (source file) is set properly.
1988 This is used to determine the language to use at each stack frame level.
1989 Currently, the language is set based upon the extension of the source
1990 file. If the language can be better inferred from the symbol
1991 information, please set the language of the symtab in the symbol-reading
1994 @findex print_subexp
1995 @findex op_print_tab
1996 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
1997 expression opcodes you have added to @file{expression.h}. Also, add the
1998 printed representations of your operators to @code{op_print_tab}.
2000 @item Add a place of call
2003 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2004 @code{parse_exp_1} (defined in @file{parse.c}).
2006 @item Use macros to trim code
2008 @cindex trimming language-dependent code
2009 The user has the option of building @value{GDBN} for some or all of the
2010 languages. If the user decides to build @value{GDBN} for the language
2011 @var{lang}, then every file dependent on @file{language.h} will have the
2012 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2013 leave out large routines that the user won't need if he or she is not
2014 using your language.
2016 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2017 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2018 compiled form of your parser) is not linked into @value{GDBN} at all.
2020 See the file @file{configure.in} for how @value{GDBN} is configured
2021 for different languages.
2023 @item Edit @file{Makefile.in}
2025 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2026 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2027 not get linked in, or, worse yet, it may not get @code{tar}red into the
2032 @node Host Definition
2034 @chapter Host Definition
2036 With the advent of Autoconf, it's rarely necessary to have host
2037 definition machinery anymore. The following information is provided,
2038 mainly, as an historical reference.
2040 @section Adding a New Host
2042 @cindex adding a new host
2043 @cindex host, adding
2044 @value{GDBN}'s host configuration support normally happens via Autoconf.
2045 New host-specific definitions should not be needed. Older hosts
2046 @value{GDBN} still use the host-specific definitions and files listed
2047 below, but these mostly exist for historical reasons, and will
2048 eventually disappear.
2051 @item gdb/config/@var{arch}/@var{xyz}.mh
2052 This file once contained both host and native configuration information
2053 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2054 configuration information is now handed by Autoconf.
2056 Host configuration information included a definition of
2057 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2058 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2059 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2061 New host only configurations do not need this file.
2063 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2064 This file once contained definitions and includes required when hosting
2065 gdb on machine @var{xyz}. Those definitions and includes are now
2066 handled by Autoconf.
2068 New host and native configurations do not need this file.
2070 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2071 file to define the macros @var{HOST_FLOAT_FORMAT},
2072 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2073 also needs to be replaced with either an Autoconf or run-time test.}
2077 @subheading Generic Host Support Files
2079 @cindex generic host support
2080 There are some ``generic'' versions of routines that can be used by
2081 various systems. These can be customized in various ways by macros
2082 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2083 the @var{xyz} host, you can just include the generic file's name (with
2084 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2086 Otherwise, if your machine needs custom support routines, you will need
2087 to write routines that perform the same functions as the generic file.
2088 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2089 into @code{XDEPFILES}.
2092 @cindex remote debugging support
2093 @cindex serial line support
2095 This contains serial line support for Unix systems. This is always
2096 included, via the makefile variable @code{SER_HARDWIRE}; override this
2097 variable in the @file{.mh} file to avoid it.
2100 This contains serial line support for 32-bit programs running under DOS,
2101 using the DJGPP (a.k.a.@: GO32) execution environment.
2103 @cindex TCP remote support
2105 This contains generic TCP support using sockets.
2108 @section Host Conditionals
2110 When @value{GDBN} is configured and compiled, various macros are
2111 defined or left undefined, to control compilation based on the
2112 attributes of the host system. These macros and their meanings (or if
2113 the meaning is not documented here, then one of the source files where
2114 they are used is indicated) are:
2117 @item @value{GDBN}INIT_FILENAME
2118 The default name of @value{GDBN}'s initialization file (normally
2122 This macro is deprecated.
2125 Define this if your system does not have a @code{<sys/file.h>}.
2127 @item SIGWINCH_HANDLER
2128 If your host defines @code{SIGWINCH}, you can define this to be the name
2129 of a function to be called if @code{SIGWINCH} is received.
2131 @item SIGWINCH_HANDLER_BODY
2132 Define this to expand into code that will define the function named by
2133 the expansion of @code{SIGWINCH_HANDLER}.
2135 @item ALIGN_STACK_ON_STARTUP
2136 @cindex stack alignment
2137 Define this if your system is of a sort that will crash in
2138 @code{tgetent} if the stack happens not to be longword-aligned when
2139 @code{main} is called. This is a rare situation, but is known to occur
2140 on several different types of systems.
2142 @item CRLF_SOURCE_FILES
2143 @cindex DOS text files
2144 Define this if host files use @code{\r\n} rather than @code{\n} as a
2145 line terminator. This will cause source file listings to omit @code{\r}
2146 characters when printing and it will allow @code{\r\n} line endings of files
2147 which are ``sourced'' by gdb. It must be possible to open files in binary
2148 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2150 @item DEFAULT_PROMPT
2152 The default value of the prompt string (normally @code{"(gdb) "}).
2155 @cindex terminal device
2156 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2158 @item FCLOSE_PROVIDED
2159 Define this if the system declares @code{fclose} in the headers included
2160 in @code{defs.h}. This isn't needed unless your compiler is unusually
2164 Define this if binary files are opened the same way as text files.
2166 @item GETENV_PROVIDED
2167 Define this if the system declares @code{getenv} in its headers included
2168 in @code{defs.h}. This isn't needed unless your compiler is unusually
2173 In some cases, use the system call @code{mmap} for reading symbol
2174 tables. For some machines this allows for sharing and quick updates.
2177 Define this if the host system has @code{termio.h}.
2184 Values for host-side constants.
2187 Substitute for isatty, if not available.
2190 This is the longest integer type available on the host. If not defined,
2191 it will default to @code{long long} or @code{long}, depending on
2192 @code{CC_HAS_LONG_LONG}.
2194 @item CC_HAS_LONG_LONG
2195 @cindex @code{long long} data type
2196 Define this if the host C compiler supports @code{long long}. This is set
2197 by the @code{configure} script.
2199 @item PRINTF_HAS_LONG_LONG
2200 Define this if the host can handle printing of long long integers via
2201 the printf format conversion specifier @code{ll}. This is set by the
2202 @code{configure} script.
2204 @item HAVE_LONG_DOUBLE
2205 Define this if the host C compiler supports @code{long double}. This is
2206 set by the @code{configure} script.
2208 @item PRINTF_HAS_LONG_DOUBLE
2209 Define this if the host can handle printing of long double float-point
2210 numbers via the printf format conversion specifier @code{Lg}. This is
2211 set by the @code{configure} script.
2213 @item SCANF_HAS_LONG_DOUBLE
2214 Define this if the host can handle the parsing of long double
2215 float-point numbers via the scanf format conversion specifier
2216 @code{Lg}. This is set by the @code{configure} script.
2218 @item LSEEK_NOT_LINEAR
2219 Define this if @code{lseek (n)} does not necessarily move to byte number
2220 @code{n} in the file. This is only used when reading source files. It
2221 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2224 This macro is used as the argument to @code{lseek} (or, most commonly,
2225 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2226 which is the POSIX equivalent.
2228 @item MMAP_BASE_ADDRESS
2229 When using HAVE_MMAP, the first mapping should go at this address.
2231 @item MMAP_INCREMENT
2232 when using HAVE_MMAP, this is the increment between mappings.
2235 If defined, this should be one or more tokens, such as @code{volatile},
2236 that can be used in both the declaration and definition of functions to
2237 indicate that they never return. The default is already set correctly
2238 if compiling with GCC. This will almost never need to be defined.
2241 If defined, this should be one or more tokens, such as
2242 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2243 of functions to indicate that they never return. The default is already
2244 set correctly if compiling with GCC. This will almost never need to be
2249 @value{GDBN} will use the @code{mmalloc} library for memory allocation
2250 for symbol reading if this symbol is defined. Be careful defining it
2251 since there are systems on which @code{mmalloc} does not work for some
2252 reason. One example is the DECstation, where its RPC library can't
2253 cope with our redefinition of @code{malloc} to call @code{mmalloc}.
2254 When defining @code{USE_MMALLOC}, you will also have to set
2255 @code{MMALLOC} in the Makefile, to point to the @code{mmalloc} library. This
2256 define is set when you configure with @samp{--with-mmalloc}.
2260 Define this if you are using @code{mmalloc}, but don't want the overhead
2261 of checking the heap with @code{mmcheck}. Note that on some systems,
2262 the C runtime makes calls to @code{malloc} prior to calling @code{main}, and if
2263 @code{free} is ever called with these pointers after calling
2264 @code{mmcheck} to enable checking, a memory corruption abort is certain
2265 to occur. These systems can still use @code{mmalloc}, but must define
2269 Define this to 1 if the C runtime allocates memory prior to
2270 @code{mmcheck} being called, but that memory is never freed so we don't
2271 have to worry about it triggering a memory corruption abort. The
2272 default is 0, which means that @code{mmcheck} will only install the heap
2273 checking functions if there has not yet been any memory allocation
2274 calls, and if it fails to install the functions, @value{GDBN} will issue a
2275 warning. This is currently defined if you configure using
2276 @samp{--with-mmalloc}.
2278 @item NO_SIGINTERRUPT
2279 @findex siginterrupt
2280 Define this to indicate that @code{siginterrupt} is not available.
2284 Define these to appropriate value for the system @code{lseek}, if not already
2288 This is the signal for stopping @value{GDBN}. Defaults to
2289 @code{SIGTSTP}. (Only redefined for the Convex.)
2292 Define this if the interior's tty should be opened with the @code{O_NOCTTY}
2293 flag. (FIXME: This should be a native-only flag, but @file{inflow.c} is
2297 Means that System V (prior to SVR4) include files are in use. (FIXME:
2298 This symbol is abused in @file{infrun.c}, @file{regex.c}, and
2299 @file{utils.c} for other things, at the moment.)
2302 Define this to help placate @code{lint} in some situations.
2305 Define this to override the defaults of @code{__volatile__} or
2310 @node Target Architecture Definition
2312 @chapter Target Architecture Definition
2314 @cindex target architecture definition
2315 @value{GDBN}'s target architecture defines what sort of
2316 machine-language programs @value{GDBN} can work with, and how it works
2319 The target architecture object is implemented as the C structure
2320 @code{struct gdbarch *}. The structure, and its methods, are generated
2321 using the Bourne shell script @file{gdbarch.sh}.
2323 @section Operating System ABI Variant Handling
2324 @cindex OS ABI variants
2326 @value{GDBN} provides a mechanism for handling variations in OS
2327 ABIs. An OS ABI variant may have influence over any number of
2328 variables in the target architecture definition. There are two major
2329 components in the OS ABI mechanism: sniffers and handlers.
2331 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2332 (the architecture may be wildcarded) in an attempt to determine the
2333 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2334 to be @dfn{generic}, while sniffers for a specific architecture are
2335 considered to be @dfn{specific}. A match from a specific sniffer
2336 overrides a match from a generic sniffer. Multiple sniffers for an
2337 architecture/flavour may exist, in order to differentiate between two
2338 different operating systems which use the same basic file format. The
2339 OS ABI framework provides a generic sniffer for ELF-format files which
2340 examines the @code{EI_OSABI} field of the ELF header, as well as note
2341 sections known to be used by several operating systems.
2343 @cindex fine-tuning @code{gdbarch} structure
2344 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2345 selected OS ABI. There may be only one handler for a given OS ABI
2346 for each BFD architecture.
2348 The following OS ABI variants are defined in @file{osabi.h}:
2352 @findex GDB_OSABI_UNKNOWN
2353 @item GDB_OSABI_UNKNOWN
2354 The ABI of the inferior is unknown. The default @code{gdbarch}
2355 settings for the architecture will be used.
2357 @findex GDB_OSABI_SVR4
2358 @item GDB_OSABI_SVR4
2359 UNIX System V Release 4
2361 @findex GDB_OSABI_HURD
2362 @item GDB_OSABI_HURD
2363 GNU using the Hurd kernel
2365 @findex GDB_OSABI_SOLARIS
2366 @item GDB_OSABI_SOLARIS
2369 @findex GDB_OSABI_OSF1
2370 @item GDB_OSABI_OSF1
2371 OSF/1, including Digital UNIX and Compaq Tru64 UNIX
2373 @findex GDB_OSABI_LINUX
2374 @item GDB_OSABI_LINUX
2375 GNU using the Linux kernel
2377 @findex GDB_OSABI_FREEBSD_AOUT
2378 @item GDB_OSABI_FREEBSD_AOUT
2379 FreeBSD using the a.out executable format
2381 @findex GDB_OSABI_FREEBSD_ELF
2382 @item GDB_OSABI_FREEBSD_ELF
2383 FreeBSD using the ELF executable format
2385 @findex GDB_OSABI_NETBSD_AOUT
2386 @item GDB_OSABI_NETBSD_AOUT
2387 NetBSD using the a.out executable format
2389 @findex GDB_OSABI_NETBSD_ELF
2390 @item GDB_OSABI_NETBSD_ELF
2391 NetBSD using the ELF executable format
2393 @findex GDB_OSABI_WINCE
2394 @item GDB_OSABI_WINCE
2397 @findex GDB_OSABI_GO32
2398 @item GDB_OSABI_GO32
2401 @findex GDB_OSABI_NETWARE
2402 @item GDB_OSABI_NETWARE
2405 @findex GDB_OSABI_ARM_EABI_V1
2406 @item GDB_OSABI_ARM_EABI_V1
2407 ARM Embedded ABI version 1
2409 @findex GDB_OSABI_ARM_EABI_V2
2410 @item GDB_OSABI_ARM_EABI_V2
2411 ARM Embedded ABI version 2
2413 @findex GDB_OSABI_ARM_APCS
2414 @item GDB_OSABI_ARM_APCS
2415 Generic ARM Procedure Call Standard
2419 Here are the functions that make up the OS ABI framework:
2421 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2422 Return the name of the OS ABI corresponding to @var{osabi}.
2425 @deftypefun void gdbarch_register_osabi (enum bfd_architecture @var{arch}, unsigned long @var{machine}, enum gdb_osabi @var{osabi}, void (*@var{init_osabi})(struct gdbarch_info @var{info}, struct gdbarch *@var{gdbarch}))
2426 Register the OS ABI handler specified by @var{init_osabi} for the
2427 architecture, machine type and OS ABI specified by @var{arch},
2428 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2429 machine type, which implies the architecture's default machine type,
2433 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2434 Register the OS ABI file sniffer specified by @var{sniffer} for the
2435 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2436 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2437 be generic, and is allowed to examine @var{flavour}-flavoured files for
2441 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2442 Examine the file described by @var{abfd} to determine its OS ABI.
2443 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2447 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2448 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2449 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2450 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2451 architecture, a warning will be issued and the debugging session will continue
2452 with the defaults already established for @var{gdbarch}.
2455 @section Registers and Memory
2457 @value{GDBN}'s model of the target machine is rather simple.
2458 @value{GDBN} assumes the machine includes a bank of registers and a
2459 block of memory. Each register may have a different size.
2461 @value{GDBN} does not have a magical way to match up with the
2462 compiler's idea of which registers are which; however, it is critical
2463 that they do match up accurately. The only way to make this work is
2464 to get accurate information about the order that the compiler uses,
2465 and to reflect that in the @code{REGISTER_NAME} and related macros.
2467 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2469 @section Pointers Are Not Always Addresses
2470 @cindex pointer representation
2471 @cindex address representation
2472 @cindex word-addressed machines
2473 @cindex separate data and code address spaces
2474 @cindex spaces, separate data and code address
2475 @cindex address spaces, separate data and code
2476 @cindex code pointers, word-addressed
2477 @cindex converting between pointers and addresses
2478 @cindex D10V addresses
2480 On almost all 32-bit architectures, the representation of a pointer is
2481 indistinguishable from the representation of some fixed-length number
2482 whose value is the byte address of the object pointed to. On such
2483 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2484 However, architectures with smaller word sizes are often cramped for
2485 address space, so they may choose a pointer representation that breaks this
2486 identity, and allows a larger code address space.
2488 For example, the Mitsubishi D10V is a 16-bit VLIW processor whose
2489 instructions are 32 bits long@footnote{Some D10V instructions are
2490 actually pairs of 16-bit sub-instructions. However, since you can't
2491 jump into the middle of such a pair, code addresses can only refer to
2492 full 32 bit instructions, which is what matters in this explanation.}.
2493 If the D10V used ordinary byte addresses to refer to code locations,
2494 then the processor would only be able to address 64kb of instructions.
2495 However, since instructions must be aligned on four-byte boundaries, the
2496 low two bits of any valid instruction's byte address are always
2497 zero---byte addresses waste two bits. So instead of byte addresses,
2498 the D10V uses word addresses---byte addresses shifted right two bits---to
2499 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2502 However, this means that code pointers and data pointers have different
2503 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2504 @code{0xC020} when used as a data address, but refers to byte address
2505 @code{0x30080} when used as a code address.
2507 (The D10V also uses separate code and data address spaces, which also
2508 affects the correspondence between pointers and addresses, but we're
2509 going to ignore that here; this example is already too long.)
2511 To cope with architectures like this---the D10V is not the only
2512 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2513 byte numbers, and @dfn{pointers}, which are the target's representation
2514 of an address of a particular type of data. In the example above,
2515 @code{0xC020} is the pointer, which refers to one of the addresses
2516 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2517 @value{GDBN} provides functions for turning a pointer into an address
2518 and vice versa, in the appropriate way for the current architecture.
2520 Unfortunately, since addresses and pointers are identical on almost all
2521 processors, this distinction tends to bit-rot pretty quickly. Thus,
2522 each time you port @value{GDBN} to an architecture which does
2523 distinguish between pointers and addresses, you'll probably need to
2524 clean up some architecture-independent code.
2526 Here are functions which convert between pointers and addresses:
2528 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2529 Treat the bytes at @var{buf} as a pointer or reference of type
2530 @var{type}, and return the address it represents, in a manner
2531 appropriate for the current architecture. This yields an address
2532 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2533 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2536 For example, if the current architecture is the Intel x86, this function
2537 extracts a little-endian integer of the appropriate length from
2538 @var{buf} and returns it. However, if the current architecture is the
2539 D10V, this function will return a 16-bit integer extracted from
2540 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2542 If @var{type} is not a pointer or reference type, then this function
2543 will signal an internal error.
2546 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2547 Store the address @var{addr} in @var{buf}, in the proper format for a
2548 pointer of type @var{type} in the current architecture. Note that
2549 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2552 For example, if the current architecture is the Intel x86, this function
2553 stores @var{addr} unmodified as a little-endian integer of the
2554 appropriate length in @var{buf}. However, if the current architecture
2555 is the D10V, this function divides @var{addr} by four if @var{type} is
2556 a pointer to a function, and then stores it in @var{buf}.
2558 If @var{type} is not a pointer or reference type, then this function
2559 will signal an internal error.
2562 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2563 Assuming that @var{val} is a pointer, return the address it represents,
2564 as appropriate for the current architecture.
2566 This function actually works on integral values, as well as pointers.
2567 For pointers, it performs architecture-specific conversions as
2568 described above for @code{extract_typed_address}.
2571 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2572 Create and return a value representing a pointer of type @var{type} to
2573 the address @var{addr}, as appropriate for the current architecture.
2574 This function performs architecture-specific conversions as described
2575 above for @code{store_typed_address}.
2579 @value{GDBN} also provides functions that do the same tasks, but assume
2580 that pointers are simply byte addresses; they aren't sensitive to the
2581 current architecture, beyond knowing the appropriate endianness.
2583 @deftypefun CORE_ADDR extract_address (void *@var{addr}, int len)
2584 Extract a @var{len}-byte number from @var{addr} in the appropriate
2585 endianness for the current architecture, and return it. Note that
2586 @var{addr} refers to @value{GDBN}'s memory, not the inferior's.
2588 This function should only be used in architecture-specific code; it
2589 doesn't have enough information to turn bits into a true address in the
2590 appropriate way for the current architecture. If you can, use
2591 @code{extract_typed_address} instead.
2594 @deftypefun void store_address (void *@var{addr}, int @var{len}, LONGEST @var{val})
2595 Store @var{val} at @var{addr} as a @var{len}-byte integer, in the
2596 appropriate endianness for the current architecture. Note that
2597 @var{addr} refers to a buffer in @value{GDBN}'s memory, not the
2600 This function should only be used in architecture-specific code; it
2601 doesn't have enough information to turn a true address into bits in the
2602 appropriate way for the current architecture. If you can, use
2603 @code{store_typed_address} instead.
2607 Here are some macros which architectures can define to indicate the
2608 relationship between pointers and addresses. These have default
2609 definitions, appropriate for architectures on which all pointers are
2610 simple unsigned byte addresses.
2612 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2613 Assume that @var{buf} holds a pointer of type @var{type}, in the
2614 appropriate format for the current architecture. Return the byte
2615 address the pointer refers to.
2617 This function may safely assume that @var{type} is either a pointer or a
2618 C@t{++} reference type.
2621 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2622 Store in @var{buf} a pointer of type @var{type} representing the address
2623 @var{addr}, in the appropriate format for the current architecture.
2625 This function may safely assume that @var{type} is either a pointer or a
2626 C@t{++} reference type.
2629 @section Address Classes
2630 @cindex address classes
2631 @cindex DW_AT_byte_size
2632 @cindex DW_AT_address_class
2634 Sometimes information about different kinds of addresses is available
2635 via the debug information. For example, some programming environments
2636 define addresses of several different sizes. If the debug information
2637 distinguishes these kinds of address classes through either the size
2638 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2639 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2640 following macros should be defined in order to disambiguate these
2641 types within @value{GDBN} as well as provide the added information to
2642 a @value{GDBN} user when printing type expressions.
2644 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2645 Returns the type flags needed to construct a pointer type whose size
2646 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2647 This function is normally called from within a symbol reader. See
2648 @file{dwarf2read.c}.
2651 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2652 Given the type flags representing an address class qualifier, return
2655 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2656 Given an address qualifier name, set the @code{int} refererenced by @var{type_flags_ptr} to the type flags
2657 for that address class qualifier.
2660 Since the need for address classes is rather rare, none of
2661 the address class macros defined by default. Predicate
2662 macros are provided to detect when they are defined.
2664 Consider a hypothetical architecture in which addresses are normally
2665 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2666 suppose that the @w{DWARF 2} information for this architecture simply
2667 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2668 of these "short" pointers. The following functions could be defined
2669 to implement the address class macros:
2672 somearch_address_class_type_flags (int byte_size,
2673 int dwarf2_addr_class)
2676 return TYPE_FLAG_ADDRESS_CLASS_1;
2682 somearch_address_class_type_flags_to_name (int type_flags)
2684 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
2691 somearch_address_class_name_to_type_flags (char *name,
2692 int *type_flags_ptr)
2694 if (strcmp (name, "short") == 0)
2696 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
2704 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
2705 to indicate the presence of one of these "short" pointers. E.g, if
2706 the debug information indicates that @code{short_ptr_var} is one of these
2707 short pointers, @value{GDBN} might show the following behavior:
2710 (gdb) ptype short_ptr_var
2711 type = int * @@short
2715 @section Raw and Virtual Register Representations
2716 @cindex raw register representation
2717 @cindex virtual register representation
2718 @cindex representations, raw and virtual registers
2720 @emph{Maintainer note: This section is pretty much obsolete. The
2721 functionality described here has largely been replaced by
2722 pseudo-registers and the mechanisms described in @ref{Target
2723 Architecture Definition, , Using Different Register and Memory Data
2724 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
2725 Bug Tracking Database} and
2726 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
2727 up-to-date information.}
2729 Some architectures use one representation for a value when it lives in a
2730 register, but use a different representation when it lives in memory.
2731 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
2732 the target registers, and the @dfn{virtual} representation is the one
2733 used in memory, and within @value{GDBN} @code{struct value} objects.
2735 @emph{Maintainer note: Notice that the same mechanism is being used to
2736 both convert a register to a @code{struct value} and alternative
2739 For almost all data types on almost all architectures, the virtual and
2740 raw representations are identical, and no special handling is needed.
2741 However, they do occasionally differ. For example:
2745 The x86 architecture supports an 80-bit @code{long double} type. However, when
2746 we store those values in memory, they occupy twelve bytes: the
2747 floating-point number occupies the first ten, and the final two bytes
2748 are unused. This keeps the values aligned on four-byte boundaries,
2749 allowing more efficient access. Thus, the x86 80-bit floating-point
2750 type is the raw representation, and the twelve-byte loosely-packed
2751 arrangement is the virtual representation.
2754 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
2755 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
2756 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
2757 raw representation, and the trimmed 32-bit representation is the
2758 virtual representation.
2761 In general, the raw representation is determined by the architecture, or
2762 @value{GDBN}'s interface to the architecture, while the virtual representation
2763 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
2764 @code{registers}, holds the register contents in raw format, and the
2765 @value{GDBN} remote protocol transmits register values in raw format.
2767 Your architecture may define the following macros to request
2768 conversions between the raw and virtual format:
2770 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
2771 Return non-zero if register number @var{reg}'s value needs different raw
2772 and virtual formats.
2774 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
2775 unless this macro returns a non-zero value for that register.
2778 @deftypefn {Target Macro} int REGISTER_RAW_SIZE (int @var{reg})
2779 The size of register number @var{reg}'s raw value. This is the number
2780 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
2781 remote protocol packet.
2784 @deftypefn {Target Macro} int REGISTER_VIRTUAL_SIZE (int @var{reg})
2785 The size of register number @var{reg}'s value, in its virtual format.
2786 This is the size a @code{struct value}'s buffer will have, holding that
2790 @deftypefn {Target Macro} struct type *REGISTER_VIRTUAL_TYPE (int @var{reg})
2791 This is the type of the virtual representation of register number
2792 @var{reg}. Note that there is no need for a macro giving a type for the
2793 register's raw form; once the register's value has been obtained, @value{GDBN}
2794 always uses the virtual form.
2797 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2798 Convert the value of register number @var{reg} to @var{type}, which
2799 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2800 at @var{from} holds the register's value in raw format; the macro should
2801 convert the value to virtual format, and place it at @var{to}.
2803 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
2804 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
2805 arguments in different orders.
2807 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
2808 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
2812 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2813 Convert the value of register number @var{reg} to @var{type}, which
2814 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2815 at @var{from} holds the register's value in raw format; the macro should
2816 convert the value to virtual format, and place it at @var{to}.
2818 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
2819 their @var{reg} and @var{type} arguments in different orders.
2823 @section Using Different Register and Memory Data Representations
2824 @cindex register representation
2825 @cindex memory representation
2826 @cindex representations, register and memory
2827 @cindex register data formats, converting
2828 @cindex @code{struct value}, converting register contents to
2830 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
2831 significant change. Many of the macros and functions refered to in this
2832 section are likely to be subject to further revision. See
2833 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
2834 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
2835 further information. cagney/2002-05-06.}
2837 Some architectures can represent a data object in a register using a
2838 form that is different to the objects more normal memory representation.
2844 The Alpha architecture can represent 32 bit integer values in
2845 floating-point registers.
2848 The x86 architecture supports 80-bit floating-point registers. The
2849 @code{long double} data type occupies 96 bits in memory but only 80 bits
2850 when stored in a register.
2854 In general, the register representation of a data type is determined by
2855 the architecture, or @value{GDBN}'s interface to the architecture, while
2856 the memory representation is determined by the Application Binary
2859 For almost all data types on almost all architectures, the two
2860 representations are identical, and no special handling is needed.
2861 However, they do occasionally differ. Your architecture may define the
2862 following macros to request conversions between the register and memory
2863 representations of a data type:
2865 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
2866 Return non-zero if the representation of a data value stored in this
2867 register may be different to the representation of that same data value
2868 when stored in memory.
2870 When non-zero, the macros @code{REGISTER_TO_VALUE} and
2871 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
2874 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2875 Convert the value of register number @var{reg} to a data object of type
2876 @var{type}. The buffer at @var{from} holds the register's value in raw
2877 format; the converted value should be placed in the buffer at @var{to}.
2879 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2880 their @var{reg} and @var{type} arguments in different orders.
2882 You should only use @code{REGISTER_TO_VALUE} with registers for which
2883 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2886 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2887 Convert a data value of type @var{type} to register number @var{reg}'
2890 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2891 their @var{reg} and @var{type} arguments in different orders.
2893 You should only use @code{VALUE_TO_REGISTER} with registers for which
2894 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2897 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
2898 See @file{mips-tdep.c}. It does not do what you want.
2902 @section Frame Interpretation
2904 @section Inferior Call Setup
2906 @section Compiler Characteristics
2908 @section Target Conditionals
2910 This section describes the macros that you can use to define the target
2915 @item ADDR_BITS_REMOVE (addr)
2916 @findex ADDR_BITS_REMOVE
2917 If a raw machine instruction address includes any bits that are not
2918 really part of the address, then define this macro to expand into an
2919 expression that zeroes those bits in @var{addr}. This is only used for
2920 addresses of instructions, and even then not in all contexts.
2922 For example, the two low-order bits of the PC on the Hewlett-Packard PA
2923 2.0 architecture contain the privilege level of the corresponding
2924 instruction. Since instructions must always be aligned on four-byte
2925 boundaries, the processor masks out these bits to generate the actual
2926 address of the instruction. ADDR_BITS_REMOVE should filter out these
2927 bits with an expression such as @code{((addr) & ~3)}.
2929 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
2930 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
2931 If @var{name} is a valid address class qualifier name, set the @code{int}
2932 referenced by @var{type_flags_ptr} to the mask representing the qualifier
2933 and return 1. If @var{name} is not a valid address class qualifier name,
2936 The value for @var{type_flags_ptr} should be one of
2937 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
2938 possibly some combination of these values or'd together.
2939 @xref{Target Architecture Definition, , Address Classes}.
2941 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
2942 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
2943 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
2946 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2947 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2948 Given a pointers byte size (as described by the debug information) and
2949 the possible @code{DW_AT_address_class} value, return the type flags
2950 used by @value{GDBN} to represent this address class. The value
2951 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
2952 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
2953 values or'd together.
2954 @xref{Target Architecture Definition, , Address Classes}.
2956 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
2957 @findex ADDRESS_CLASS_TYPE_FLAGS_P
2958 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
2961 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
2962 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
2963 Return the name of the address class qualifier associated with the type
2964 flags given by @var{type_flags}.
2966 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
2967 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
2968 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
2970 @xref{Target Architecture Definition, , Address Classes}.
2972 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
2973 @findex ADDRESS_TO_POINTER
2974 Store in @var{buf} a pointer of type @var{type} representing the address
2975 @var{addr}, in the appropriate format for the current architecture.
2976 This macro may safely assume that @var{type} is either a pointer or a
2977 C@t{++} reference type.
2978 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
2980 @item BELIEVE_PCC_PROMOTION
2981 @findex BELIEVE_PCC_PROMOTION
2982 Define if the compiler promotes a @code{short} or @code{char}
2983 parameter to an @code{int}, but still reports the parameter as its
2984 original type, rather than the promoted type.
2986 @item BELIEVE_PCC_PROMOTION_TYPE
2987 @findex BELIEVE_PCC_PROMOTION_TYPE
2988 Define this if @value{GDBN} should believe the type of a @code{short}
2989 argument when compiled by @code{pcc}, but look within a full int space to get
2990 its value. Only defined for Sun-3 at present.
2992 @item BITS_BIG_ENDIAN
2993 @findex BITS_BIG_ENDIAN
2994 Define this if the numbering of bits in the targets does @strong{not} match the
2995 endianness of the target byte order. A value of 1 means that the bits
2996 are numbered in a big-endian bit order, 0 means little-endian.
3000 This is the character array initializer for the bit pattern to put into
3001 memory where a breakpoint is set. Although it's common to use a trap
3002 instruction for a breakpoint, it's not required; for instance, the bit
3003 pattern could be an invalid instruction. The breakpoint must be no
3004 longer than the shortest instruction of the architecture.
3006 @code{BREAKPOINT} has been deprecated in favor of
3007 @code{BREAKPOINT_FROM_PC}.
3009 @item BIG_BREAKPOINT
3010 @itemx LITTLE_BREAKPOINT
3011 @findex LITTLE_BREAKPOINT
3012 @findex BIG_BREAKPOINT
3013 Similar to BREAKPOINT, but used for bi-endian targets.
3015 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3016 favor of @code{BREAKPOINT_FROM_PC}.
3018 @item REMOTE_BREAKPOINT
3019 @itemx LITTLE_REMOTE_BREAKPOINT
3020 @itemx BIG_REMOTE_BREAKPOINT
3021 @findex BIG_REMOTE_BREAKPOINT
3022 @findex LITTLE_REMOTE_BREAKPOINT
3023 @findex REMOTE_BREAKPOINT
3024 Similar to BREAKPOINT, but used for remote targets.
3026 @code{BIG_REMOTE_BREAKPOINT} and @code{LITTLE_REMOTE_BREAKPOINT} have been
3027 deprecated in favor of @code{BREAKPOINT_FROM_PC}.
3029 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3030 @findex BREAKPOINT_FROM_PC
3031 Use the program counter to determine the contents and size of a
3032 breakpoint instruction. It returns a pointer to a string of bytes
3033 that encode a breakpoint instruction, stores the length of the string
3034 to *@var{lenptr}, and adjusts pc (if necessary) to point to the actual
3035 memory location where the breakpoint should be inserted.
3037 Although it is common to use a trap instruction for a breakpoint, it's
3038 not required; for instance, the bit pattern could be an invalid
3039 instruction. The breakpoint must be no longer than the shortest
3040 instruction of the architecture.
3042 Replaces all the other @var{BREAKPOINT} macros.
3044 @item MEMORY_INSERT_BREAKPOINT (@var{addr}, @var{contents_cache})
3045 @itemx MEMORY_REMOVE_BREAKPOINT (@var{addr}, @var{contents_cache})
3046 @findex MEMORY_REMOVE_BREAKPOINT
3047 @findex MEMORY_INSERT_BREAKPOINT
3048 Insert or remove memory based breakpoints. Reasonable defaults
3049 (@code{default_memory_insert_breakpoint} and
3050 @code{default_memory_remove_breakpoint} respectively) have been
3051 provided so that it is not necessary to define these for most
3052 architectures. Architectures which may want to define
3053 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3054 likely have instructions that are oddly sized or are not stored in a
3055 conventional manner.
3057 It may also be desirable (from an efficiency standpoint) to define
3058 custom breakpoint insertion and removal routines if
3059 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3063 @findex CALL_DUMMY_P
3064 A C expression that is non-zero when the target supports inferior function
3067 @item CALL_DUMMY_WORDS
3068 @findex CALL_DUMMY_WORDS
3069 Pointer to an array of @code{LONGEST} words of data containing
3070 host-byte-ordered @code{REGISTER_BYTES} sized values that partially
3071 specify the sequence of instructions needed for an inferior function
3074 Should be deprecated in favor of a macro that uses target-byte-ordered
3077 @item SIZEOF_CALL_DUMMY_WORDS
3078 @findex SIZEOF_CALL_DUMMY_WORDS
3079 The size of @code{CALL_DUMMY_WORDS}. When @code{CALL_DUMMY_P} this must
3080 return a positive value. See also @code{CALL_DUMMY_LENGTH}.
3084 A static initializer for @code{CALL_DUMMY_WORDS}. Deprecated.
3086 @item CALL_DUMMY_LOCATION
3087 @findex CALL_DUMMY_LOCATION
3088 See the file @file{inferior.h}.
3090 @item CALL_DUMMY_STACK_ADJUST
3091 @findex CALL_DUMMY_STACK_ADJUST
3092 Stack adjustment needed when performing an inferior function call.
3094 Should be deprecated in favor of something like @code{STACK_ALIGN}.
3096 @item CALL_DUMMY_STACK_ADJUST_P
3097 @findex CALL_DUMMY_STACK_ADJUST_P
3098 Predicate for use of @code{CALL_DUMMY_STACK_ADJUST}.
3100 Should be deprecated in favor of something like @code{STACK_ALIGN}.
3102 @item CANNOT_FETCH_REGISTER (@var{regno})
3103 @findex CANNOT_FETCH_REGISTER
3104 A C expression that should be nonzero if @var{regno} cannot be fetched
3105 from an inferior process. This is only relevant if
3106 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3108 @item CANNOT_STORE_REGISTER (@var{regno})
3109 @findex CANNOT_STORE_REGISTER
3110 A C expression that should be nonzero if @var{regno} should not be
3111 written to the target. This is often the case for program counters,
3112 status words, and other special registers. If this is not defined,
3113 @value{GDBN} will assume that all registers may be written.
3115 @item DO_DEFERRED_STORES
3116 @itemx CLEAR_DEFERRED_STORES
3117 @findex CLEAR_DEFERRED_STORES
3118 @findex DO_DEFERRED_STORES
3119 Define this to execute any deferred stores of registers into the inferior,
3120 and to cancel any deferred stores.
3122 Currently only implemented correctly for native Sparc configurations?
3124 @item int CONVERT_REGISTER_P(@var{regnum})
3125 @findex CONVERT_REGISTER_P
3126 Return non-zero if register @var{regnum} can represent data values in a
3128 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3130 @item DECR_PC_AFTER_BREAK
3131 @findex DECR_PC_AFTER_BREAK
3132 Define this to be the amount by which to decrement the PC after the
3133 program encounters a breakpoint. This is often the number of bytes in
3134 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3136 @item DECR_PC_AFTER_HW_BREAK
3137 @findex DECR_PC_AFTER_HW_BREAK
3138 Similarly, for hardware breakpoints.
3140 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3141 @findex DISABLE_UNSETTABLE_BREAK
3142 If defined, this should evaluate to 1 if @var{addr} is in a shared
3143 library in which breakpoints cannot be set and so should be disabled.
3145 @item PRINT_FLOAT_INFO()
3146 @findex PRINT_FLOAT_INFO
3147 If defined, then the @samp{info float} command will print information about
3148 the processor's floating point unit.
3150 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3151 @findex print_registers_info
3152 If defined, pretty print the value of the register @var{regnum} for the
3153 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3154 either all registers (@var{all} is non zero) or a select subset of
3155 registers (@var{all} is zero).
3157 The default method prints one register per line, and if @var{all} is
3158 zero omits floating-point registers.
3160 @item PRINT_VECTOR_INFO()
3161 @findex PRINT_VECTOR_INFO
3162 If defined, then the @samp{info vector} command will call this function
3163 to print information about the processor's vector unit.
3165 By default, the @samp{info vector} command will print all vector
3166 registers (the register's type having the vector attribute).
3168 @item DWARF_REG_TO_REGNUM
3169 @findex DWARF_REG_TO_REGNUM
3170 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3171 no conversion will be performed.
3173 @item DWARF2_REG_TO_REGNUM
3174 @findex DWARF2_REG_TO_REGNUM
3175 Convert DWARF2 register number into @value{GDBN} regnum. If not
3176 defined, no conversion will be performed.
3178 @item ECOFF_REG_TO_REGNUM
3179 @findex ECOFF_REG_TO_REGNUM
3180 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3181 no conversion will be performed.
3183 @item END_OF_TEXT_DEFAULT
3184 @findex END_OF_TEXT_DEFAULT
3185 This is an expression that should designate the end of the text section.
3188 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3189 @findex EXTRACT_RETURN_VALUE
3190 Define this to extract a function's return value of type @var{type} from
3191 the raw register state @var{regbuf} and copy that, in virtual format,
3194 @item EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3195 @findex EXTRACT_STRUCT_VALUE_ADDRESS
3196 When defined, extract from the array @var{regbuf} (containing the raw
3197 register state) the @code{CORE_ADDR} at which a function should return
3198 its structure value.
3200 If not defined, @code{EXTRACT_RETURN_VALUE} is used.
3202 @item EXTRACT_STRUCT_VALUE_ADDRESS_P()
3203 @findex EXTRACT_STRUCT_VALUE_ADDRESS_P
3204 Predicate for @code{EXTRACT_STRUCT_VALUE_ADDRESS}.
3208 If the virtual frame pointer is kept in a register, then define this
3209 macro to be the number (greater than or equal to zero) of that register.
3211 This should only need to be defined if @code{TARGET_READ_FP} is not
3214 @item FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3215 @findex FRAMELESS_FUNCTION_INVOCATION
3216 Define this to an expression that returns 1 if the function invocation
3217 represented by @var{fi} does not have a stack frame associated with it.
3220 @item frame_align (@var{address})
3221 @anchor{frame_align}
3223 Define this to adjust @var{address} so that it meets the alignment
3224 requirements for the start of a new stack frame. A stack frame's
3225 alignment requirements are typically stronger than a target processors
3226 stack alignment requirements (@pxref{STACK_ALIGN}).
3228 This function is used to ensure that, when creating a dummy frame, both
3229 the initial stack pointer and (if needed) the address of the return
3230 value are correctly aligned.
3232 Unlike @code{STACK_ALIGN}, this function always adjusts the address in
3233 the direction of stack growth.
3235 By default, no frame based stack alignment is performed.
3237 @item FRAME_ARGS_ADDRESS_CORRECT
3238 @findex FRAME_ARGS_ADDRESS_CORRECT
3241 @item FRAME_CHAIN(@var{frame})
3243 Given @var{frame}, return a pointer to the calling frame.
3245 @item FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3246 @findex FRAME_CHAIN_VALID
3247 Define this to be an expression that returns zero if the given frame is an
3248 outermost frame, with no caller, and nonzero otherwise. Most normal
3249 situations can be handled without defining this macro, including @code{NULL}
3250 chain pointers, dummy frames, and frames whose PC values are inside the
3251 startup file (e.g.@: @file{crt0.o}), inside @code{main}, or inside
3254 @item FRAME_INIT_SAVED_REGS(@var{frame})
3255 @findex FRAME_INIT_SAVED_REGS
3256 See @file{frame.h}. Determines the address of all registers in the
3257 current stack frame storing each in @code{frame->saved_regs}. Space for
3258 @code{frame->saved_regs} shall be allocated by
3259 @code{FRAME_INIT_SAVED_REGS} using @code{frame_saved_regs_zalloc}.
3261 @code{FRAME_FIND_SAVED_REGS} and @code{EXTRA_FRAME_INFO} are deprecated.
3263 @item FRAME_NUM_ARGS (@var{fi})
3264 @findex FRAME_NUM_ARGS
3265 For the frame described by @var{fi} return the number of arguments that
3266 are being passed. If the number of arguments is not known, return
3269 @item FRAME_SAVED_PC(@var{frame})
3270 @findex FRAME_SAVED_PC
3271 Given @var{frame}, return the pc saved there. This is the return
3274 @item FUNCTION_EPILOGUE_SIZE
3275 @findex FUNCTION_EPILOGUE_SIZE
3276 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3277 function end symbol is 0. For such targets, you must define
3278 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3279 function's epilogue.
3281 @item FUNCTION_START_OFFSET
3282 @findex FUNCTION_START_OFFSET
3283 An integer, giving the offset in bytes from a function's address (as
3284 used in the values of symbols, function pointers, etc.), and the
3285 function's first genuine instruction.
3287 This is zero on almost all machines: the function's address is usually
3288 the address of its first instruction. However, on the VAX, for example,
3289 each function starts with two bytes containing a bitmask indicating
3290 which registers to save upon entry to the function. The VAX @code{call}
3291 instructions check this value, and save the appropriate registers
3292 automatically. Thus, since the offset from the function's address to
3293 its first instruction is two bytes, @code{FUNCTION_START_OFFSET} would
3296 @item GCC_COMPILED_FLAG_SYMBOL
3297 @itemx GCC2_COMPILED_FLAG_SYMBOL
3298 @findex GCC2_COMPILED_FLAG_SYMBOL
3299 @findex GCC_COMPILED_FLAG_SYMBOL
3300 If defined, these are the names of the symbols that @value{GDBN} will
3301 look for to detect that GCC compiled the file. The default symbols
3302 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3303 respectively. (Currently only defined for the Delta 68.)
3305 @item @value{GDBN}_MULTI_ARCH
3306 @findex @value{GDBN}_MULTI_ARCH
3307 If defined and non-zero, enables support for multiple architectures
3308 within @value{GDBN}.
3310 This support can be enabled at two levels. At level one, only
3311 definitions for previously undefined macros are provided; at level two,
3312 a multi-arch definition of all architecture dependent macros will be
3315 @item @value{GDBN}_TARGET_IS_HPPA
3316 @findex @value{GDBN}_TARGET_IS_HPPA
3317 This determines whether horrible kludge code in @file{dbxread.c} and
3318 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3319 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3322 @item GET_LONGJMP_TARGET
3323 @findex GET_LONGJMP_TARGET
3324 For most machines, this is a target-dependent parameter. On the
3325 DECstation and the Iris, this is a native-dependent parameter, since
3326 the header file @file{setjmp.h} is needed to define it.
3328 This macro determines the target PC address that @code{longjmp} will jump to,
3329 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3330 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3331 pointer. It examines the current state of the machine as needed.
3333 @item GET_SAVED_REGISTER
3334 @findex GET_SAVED_REGISTER
3335 @findex get_saved_register
3336 Define this if you need to supply your own definition for the function
3337 @code{get_saved_register}.
3339 @item IBM6000_TARGET
3340 @findex IBM6000_TARGET
3341 Shows that we are configured for an IBM RS/6000 target. This
3342 conditional should be eliminated (FIXME) and replaced by
3343 feature-specific macros. It was introduced in a haste and we are
3344 repenting at leisure.
3346 @item I386_USE_GENERIC_WATCHPOINTS
3347 An x86-based target can define this to use the generic x86 watchpoint
3348 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3350 @item SYMBOLS_CAN_START_WITH_DOLLAR
3351 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3352 Some systems have routines whose names start with @samp{$}. Giving this
3353 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3354 routines when parsing tokens that begin with @samp{$}.
3356 On HP-UX, certain system routines (millicode) have names beginning with
3357 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3358 routine that handles inter-space procedure calls on PA-RISC.
3360 @item INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3361 @findex INIT_EXTRA_FRAME_INFO
3362 If additional information about the frame is required this should be
3363 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3364 is allocated using @code{frame_extra_info_zalloc}.
3366 @item DEPRECATED_INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3367 @findex DEPRECATED_INIT_FRAME_PC
3368 This is a C statement that sets the pc of the frame pointed to by
3369 @var{prev}. [By default...]
3371 @item INNER_THAN (@var{lhs}, @var{rhs})
3373 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3374 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3375 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3378 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3379 @findex gdbarch_in_function_epilogue_p
3380 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3381 The epilogue of a function is defined as the part of a function where
3382 the stack frame of the function already has been destroyed up to the
3383 final `return from function call' instruction.
3385 @item SIGTRAMP_START (@var{pc})
3386 @findex SIGTRAMP_START
3387 @itemx SIGTRAMP_END (@var{pc})
3388 @findex SIGTRAMP_END
3389 Define these to be the start and end address of the @code{sigtramp} for the
3390 given @var{pc}. On machines where the address is just a compile time
3391 constant, the macro expansion will typically just ignore the supplied
3394 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3395 @findex IN_SOLIB_CALL_TRAMPOLINE
3396 Define this to evaluate to nonzero if the program is stopped in the
3397 trampoline that connects to a shared library.
3399 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3400 @findex IN_SOLIB_RETURN_TRAMPOLINE
3401 Define this to evaluate to nonzero if the program is stopped in the
3402 trampoline that returns from a shared library.
3404 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3405 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3406 Define this to evaluate to nonzero if the program is stopped in the
3409 @item SKIP_SOLIB_RESOLVER (@var{pc})
3410 @findex SKIP_SOLIB_RESOLVER
3411 Define this to evaluate to the (nonzero) address at which execution
3412 should continue to get past the dynamic linker's symbol resolution
3413 function. A zero value indicates that it is not important or necessary
3414 to set a breakpoint to get through the dynamic linker and that single
3415 stepping will suffice.
3417 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3418 @findex INTEGER_TO_ADDRESS
3419 @cindex converting integers to addresses
3420 Define this when the architecture needs to handle non-pointer to address
3421 conversions specially. Converts that value to an address according to
3422 the current architectures conventions.
3424 @emph{Pragmatics: When the user copies a well defined expression from
3425 their source code and passes it, as a parameter, to @value{GDBN}'s
3426 @code{print} command, they should get the same value as would have been
3427 computed by the target program. Any deviation from this rule can cause
3428 major confusion and annoyance, and needs to be justified carefully. In
3429 other words, @value{GDBN} doesn't really have the freedom to do these
3430 conversions in clever and useful ways. It has, however, been pointed
3431 out that users aren't complaining about how @value{GDBN} casts integers
3432 to pointers; they are complaining that they can't take an address from a
3433 disassembly listing and give it to @code{x/i}. Adding an architecture
3434 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3435 @value{GDBN} to ``get it right'' in all circumstances.}
3437 @xref{Target Architecture Definition, , Pointers Are Not Always
3440 @item IS_TRAPPED_INTERNALVAR (@var{name})
3441 @findex IS_TRAPPED_INTERNALVAR
3442 This is an ugly hook to allow the specification of special actions that
3443 should occur as a side-effect of setting the value of a variable
3444 internal to @value{GDBN}. Currently only used by the h8500. Note that this
3445 could be either a host or target conditional.
3447 @item NEED_TEXT_START_END
3448 @findex NEED_TEXT_START_END
3449 Define this if @value{GDBN} should determine the start and end addresses of the
3450 text section. (Seems dubious.)
3452 @item NO_HIF_SUPPORT
3453 @findex NO_HIF_SUPPORT
3454 (Specific to the a29k.)
3456 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3457 @findex POINTER_TO_ADDRESS
3458 Assume that @var{buf} holds a pointer of type @var{type}, in the
3459 appropriate format for the current architecture. Return the byte
3460 address the pointer refers to.
3461 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3463 @item REGISTER_CONVERTIBLE (@var{reg})
3464 @findex REGISTER_CONVERTIBLE
3465 Return non-zero if @var{reg} uses different raw and virtual formats.
3466 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3468 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3469 @findex REGISTER_TO_VALUE
3470 Convert the raw contents of register @var{regnum} into a value of type
3472 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3474 @item REGISTER_RAW_SIZE (@var{reg})
3475 @findex REGISTER_RAW_SIZE
3476 Return the raw size of @var{reg}; defaults to the size of the register's
3478 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3480 @item register_reggroup_p (@var{gdbarch}, @var{regnum}, @var{reggroup})
3481 @findex register_reggroup_p
3482 @cindex register groups
3483 Return non-zero if register @var{regnum} is a member of the register
3484 group @var{reggroup}.
3486 By default, registers are grouped as follows:
3489 @item float_reggroup
3490 Any register with a valid name and a floating-point type.
3491 @item vector_reggroup
3492 Any register with a valid name and a vector type.
3493 @item general_reggroup
3494 Any register with a valid name and a type other than vector or
3495 floating-point. @samp{float_reggroup}.
3497 @itemx restore_reggroup
3499 Any register with a valid name.
3502 @item REGISTER_VIRTUAL_SIZE (@var{reg})
3503 @findex REGISTER_VIRTUAL_SIZE
3504 Return the virtual size of @var{reg}; defaults to the size of the
3505 register's virtual type.
3506 Return the virtual size of @var{reg}.
3507 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3509 @item REGISTER_VIRTUAL_TYPE (@var{reg})
3510 @findex REGISTER_VIRTUAL_TYPE
3511 Return the virtual type of @var{reg}.
3512 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3514 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3515 @findex REGISTER_CONVERT_TO_VIRTUAL
3516 Convert the value of register @var{reg} from its raw form to its virtual
3518 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3520 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3521 @findex REGISTER_CONVERT_TO_RAW
3522 Convert the value of register @var{reg} from its virtual form to its raw
3524 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3526 @item RETURN_VALUE_ON_STACK(@var{type})
3527 @findex RETURN_VALUE_ON_STACK
3528 @cindex returning structures by value
3529 @cindex structures, returning by value
3531 Return non-zero if values of type TYPE are returned on the stack, using
3532 the ``struct convention'' (i.e., the caller provides a pointer to a
3533 buffer in which the callee should store the return value). This
3534 controls how the @samp{finish} command finds a function's return value,
3535 and whether an inferior function call reserves space on the stack for
3538 The full logic @value{GDBN} uses here is kind of odd.
3542 If the type being returned by value is not a structure, union, or array,
3543 and @code{RETURN_VALUE_ON_STACK} returns zero, then @value{GDBN}
3544 concludes the value is not returned using the struct convention.
3547 Otherwise, @value{GDBN} calls @code{USE_STRUCT_CONVENTION} (see below).
3548 If that returns non-zero, @value{GDBN} assumes the struct convention is
3552 In other words, to indicate that a given type is returned by value using
3553 the struct convention, that type must be either a struct, union, array,
3554 or something @code{RETURN_VALUE_ON_STACK} likes, @emph{and} something
3555 that @code{USE_STRUCT_CONVENTION} likes.
3557 Note that, in C and C@t{++}, arrays are never returned by value. In those
3558 languages, these predicates will always see a pointer type, never an
3559 array type. All the references above to arrays being returned by value
3560 apply only to other languages.
3562 @item SOFTWARE_SINGLE_STEP_P()
3563 @findex SOFTWARE_SINGLE_STEP_P
3564 Define this as 1 if the target does not have a hardware single-step
3565 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3567 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breapoints_p})
3568 @findex SOFTWARE_SINGLE_STEP
3569 A function that inserts or removes (depending on
3570 @var{insert_breapoints_p}) breakpoints at each possible destinations of
3571 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3574 @item SOFUN_ADDRESS_MAYBE_MISSING
3575 @findex SOFUN_ADDRESS_MAYBE_MISSING
3576 Somebody clever observed that, the more actual addresses you have in the
3577 debug information, the more time the linker has to spend relocating
3578 them. So whenever there's some other way the debugger could find the
3579 address it needs, you should omit it from the debug info, to make
3582 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3583 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3584 entries in stabs-format debugging information. @code{N_SO} stabs mark
3585 the beginning and ending addresses of compilation units in the text
3586 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3588 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3592 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3593 addresses where the function starts by taking the function name from
3594 the stab, and then looking that up in the minsyms (the
3595 linker/assembler symbol table). In other words, the stab has the
3596 name, and the linker/assembler symbol table is the only place that carries
3600 @code{N_SO} stabs have an address of zero, too. You just look at the
3601 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3602 and guess the starting and ending addresses of the compilation unit from
3606 @item PCC_SOL_BROKEN
3607 @findex PCC_SOL_BROKEN
3608 (Used only in the Convex target.)
3610 @item PC_IN_SIGTRAMP (@var{pc}, @var{name})
3611 @findex PC_IN_SIGTRAMP
3613 The @dfn{sigtramp} is a routine that the kernel calls (which then calls
3614 the signal handler). On most machines it is a library routine that is
3615 linked into the executable.
3617 This function, given a program counter value in @var{pc} and the
3618 (possibly NULL) name of the function in which that @var{pc} resides,
3619 returns nonzero if the @var{pc} and/or @var{name} show that we are in
3622 @item PC_LOAD_SEGMENT
3623 @findex PC_LOAD_SEGMENT
3624 If defined, print information about the load segment for the program
3625 counter. (Defined only for the RS/6000.)
3629 If the program counter is kept in a register, then define this macro to
3630 be the number (greater than or equal to zero) of that register.
3632 This should only need to be defined if @code{TARGET_READ_PC} and
3633 @code{TARGET_WRITE_PC} are not defined.
3637 The number of the ``next program counter'' register, if defined.
3640 @findex PARM_BOUNDARY
3641 If non-zero, round arguments to a boundary of this many bits before
3642 pushing them on the stack.
3644 @item PRINT_TYPELESS_INTEGER
3645 @findex PRINT_TYPELESS_INTEGER
3646 This is an obscure substitute for @code{print_longest} that seems to
3647 have been defined for the Convex target.
3649 @item PROCESS_LINENUMBER_HOOK
3650 @findex PROCESS_LINENUMBER_HOOK
3651 A hook defined for XCOFF reading.
3653 @item PROLOGUE_FIRSTLINE_OVERLAP
3654 @findex PROLOGUE_FIRSTLINE_OVERLAP
3655 (Only used in unsupported Convex configuration.)
3659 If defined, this is the number of the processor status register. (This
3660 definition is only used in generic code when parsing "$ps".)
3664 @findex call_function_by_hand
3665 @findex return_command
3666 Used in @samp{call_function_by_hand} to remove an artificial stack
3667 frame and in @samp{return_command} to remove a real stack frame.
3669 @item PUSH_ARGUMENTS (@var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
3670 @findex PUSH_ARGUMENTS
3671 Define this to push arguments onto the stack for inferior function
3672 call. Returns the updated stack pointer value.
3674 @item PUSH_DUMMY_FRAME
3675 @findex PUSH_DUMMY_FRAME
3676 Used in @samp{call_function_by_hand} to create an artificial stack frame.
3678 @item REGISTER_BYTES
3679 @findex REGISTER_BYTES
3680 The total amount of space needed to store @value{GDBN}'s copy of the machine's
3683 @item REGISTER_NAME(@var{i})
3684 @findex REGISTER_NAME
3685 Return the name of register @var{i} as a string. May return @code{NULL}
3686 or @code{NUL} to indicate that register @var{i} is not valid.
3688 @item REGISTER_NAMES
3689 @findex REGISTER_NAMES
3690 Deprecated in favor of @code{REGISTER_NAME}.
3692 @item REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3693 @findex REG_STRUCT_HAS_ADDR
3694 Define this to return 1 if the given type will be passed by pointer
3695 rather than directly.
3697 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3698 @findex SAVE_DUMMY_FRAME_TOS
3699 Used in @samp{call_function_by_hand} to notify the target dependent code
3700 of the top-of-stack value that will be passed to the the inferior code.
3701 This is the value of the @code{SP} after both the dummy frame and space
3702 for parameters/results have been allocated on the stack.
3704 @item SDB_REG_TO_REGNUM
3705 @findex SDB_REG_TO_REGNUM
3706 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3707 defined, no conversion will be done.
3709 @item SKIP_PERMANENT_BREAKPOINT
3710 @findex SKIP_PERMANENT_BREAKPOINT
3711 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
3712 steps over a breakpoint by removing it, stepping one instruction, and
3713 re-inserting the breakpoint. However, permanent breakpoints are
3714 hardwired into the inferior, and can't be removed, so this strategy
3715 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
3716 state so that execution will resume just after the breakpoint. This
3717 macro does the right thing even when the breakpoint is in the delay slot
3718 of a branch or jump.
3720 @item SKIP_PROLOGUE (@var{pc})
3721 @findex SKIP_PROLOGUE
3722 A C expression that returns the address of the ``real'' code beyond the
3723 function entry prologue found at @var{pc}.
3725 @item SKIP_TRAMPOLINE_CODE (@var{pc})
3726 @findex SKIP_TRAMPOLINE_CODE
3727 If the target machine has trampoline code that sits between callers and
3728 the functions being called, then define this macro to return a new PC
3729 that is at the start of the real function.
3733 If the stack-pointer is kept in a register, then define this macro to be
3734 the number (greater than or equal to zero) of that register.
3736 This should only need to be defined if @code{TARGET_WRITE_SP} and
3737 @code{TARGET_WRITE_SP} are not defined.
3739 @item STAB_REG_TO_REGNUM
3740 @findex STAB_REG_TO_REGNUM
3741 Define this to convert stab register numbers (as gotten from `r'
3742 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
3745 @item STACK_ALIGN (@var{addr})
3746 @anchor{STACK_ALIGN}
3748 Define this to increase @var{addr} so that it meets the alignment
3749 requirements for the processor's stack.
3751 Unlike @ref{frame_align}, this function always adjusts @var{addr}
3754 By default, no stack alignment is performed.
3756 @item STEP_SKIPS_DELAY (@var{addr})
3757 @findex STEP_SKIPS_DELAY
3758 Define this to return true if the address is of an instruction with a
3759 delay slot. If a breakpoint has been placed in the instruction's delay
3760 slot, @value{GDBN} will single-step over that instruction before resuming
3761 normally. Currently only defined for the Mips.
3763 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
3764 @findex STORE_RETURN_VALUE
3765 A C expression that writes the function return value, found in
3766 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
3767 value that is to be returned.
3769 @item SUN_FIXED_LBRAC_BUG
3770 @findex SUN_FIXED_LBRAC_BUG
3771 (Used only for Sun-3 and Sun-4 targets.)
3773 @item SYMBOL_RELOADING_DEFAULT
3774 @findex SYMBOL_RELOADING_DEFAULT
3775 The default value of the ``symbol-reloading'' variable. (Never defined in
3778 @item TARGET_CHAR_BIT
3779 @findex TARGET_CHAR_BIT
3780 Number of bits in a char; defaults to 8.
3782 @item TARGET_CHAR_SIGNED
3783 @findex TARGET_CHAR_SIGNED
3784 Non-zero if @code{char} is normally signed on this architecture; zero if
3785 it should be unsigned.
3787 The ISO C standard requires the compiler to treat @code{char} as
3788 equivalent to either @code{signed char} or @code{unsigned char}; any
3789 character in the standard execution set is supposed to be positive.
3790 Most compilers treat @code{char} as signed, but @code{char} is unsigned
3791 on the IBM S/390, RS6000, and PowerPC targets.
3793 @item TARGET_COMPLEX_BIT
3794 @findex TARGET_COMPLEX_BIT
3795 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
3797 At present this macro is not used.
3799 @item TARGET_DOUBLE_BIT
3800 @findex TARGET_DOUBLE_BIT
3801 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
3803 @item TARGET_DOUBLE_COMPLEX_BIT
3804 @findex TARGET_DOUBLE_COMPLEX_BIT
3805 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
3807 At present this macro is not used.
3809 @item TARGET_FLOAT_BIT
3810 @findex TARGET_FLOAT_BIT
3811 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
3813 @item TARGET_INT_BIT
3814 @findex TARGET_INT_BIT
3815 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3817 @item TARGET_LONG_BIT
3818 @findex TARGET_LONG_BIT
3819 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3821 @item TARGET_LONG_DOUBLE_BIT
3822 @findex TARGET_LONG_DOUBLE_BIT
3823 Number of bits in a long double float;
3824 defaults to @code{2 * TARGET_DOUBLE_BIT}.
3826 @item TARGET_LONG_LONG_BIT
3827 @findex TARGET_LONG_LONG_BIT
3828 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
3830 @item TARGET_PTR_BIT
3831 @findex TARGET_PTR_BIT
3832 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
3834 @item TARGET_SHORT_BIT
3835 @findex TARGET_SHORT_BIT
3836 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
3838 @item TARGET_READ_PC
3839 @findex TARGET_READ_PC
3840 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
3841 @findex TARGET_WRITE_PC
3842 @itemx TARGET_READ_SP
3843 @findex TARGET_READ_SP
3844 @itemx TARGET_WRITE_SP
3845 @findex TARGET_WRITE_SP
3846 @itemx TARGET_READ_FP
3847 @findex TARGET_READ_FP
3853 These change the behavior of @code{read_pc}, @code{write_pc},
3854 @code{read_sp}, @code{write_sp} and @code{read_fp}. For most targets,
3855 these may be left undefined. @value{GDBN} will call the read and write
3856 register functions with the relevant @code{_REGNUM} argument.
3858 These macros are useful when a target keeps one of these registers in a
3859 hard to get at place; for example, part in a segment register and part
3860 in an ordinary register.
3862 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
3863 @findex TARGET_VIRTUAL_FRAME_POINTER
3864 Returns a @code{(register, offset)} pair representing the virtual
3865 frame pointer in use at the code address @var{pc}. If virtual
3866 frame pointers are not used, a default definition simply returns
3867 @code{FP_REGNUM}, with an offset of zero.
3869 @item TARGET_HAS_HARDWARE_WATCHPOINTS
3870 If non-zero, the target has support for hardware-assisted
3871 watchpoints. @xref{Algorithms, watchpoints}, for more details and
3872 other related macros.
3874 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
3875 @findex TARGET_PRINT_INSN
3876 This is the function used by @value{GDBN} to print an assembly
3877 instruction. It prints the instruction at address @var{addr} in
3878 debugged memory and returns the length of the instruction, in bytes. If
3879 a target doesn't define its own printing routine, it defaults to an
3880 accessor function for the global pointer @code{tm_print_insn}. This
3881 usually points to a function in the @code{opcodes} library (@pxref{Support
3882 Libraries, ,Opcodes}). @var{info} is a structure (of type
3883 @code{disassemble_info}) defined in @file{include/dis-asm.h} used to
3884 pass information to the instruction decoding routine.
3886 @item USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
3887 @findex USE_STRUCT_CONVENTION
3888 If defined, this must be an expression that is nonzero if a value of the
3889 given @var{type} being returned from a function must have space
3890 allocated for it on the stack. @var{gcc_p} is true if the function
3891 being considered is known to have been compiled by GCC; this is helpful
3892 for systems where GCC is known to use different calling convention than
3895 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
3896 @findex VALUE_TO_REGISTER
3897 Convert a value of type @var{type} into the raw contents of register
3899 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3901 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3902 @findex VARIABLES_INSIDE_BLOCK
3903 For dbx-style debugging information, if the compiler puts variable
3904 declarations inside LBRAC/RBRAC blocks, this should be defined to be
3905 nonzero. @var{desc} is the value of @code{n_desc} from the
3906 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
3907 presence of either the @code{GCC_COMPILED_SYMBOL} or the
3908 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
3910 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3911 @findex OS9K_VARIABLES_INSIDE_BLOCK
3912 Similarly, for OS/9000. Defaults to 1.
3915 Motorola M68K target conditionals.
3919 Define this to be the 4-bit location of the breakpoint trap vector. If
3920 not defined, it will default to @code{0xf}.
3922 @item REMOTE_BPT_VECTOR
3923 Defaults to @code{1}.
3925 @item NAME_OF_MALLOC
3926 @findex NAME_OF_MALLOC
3927 A string containing the name of the function to call in order to
3928 allocate some memory in the inferior. The default value is "malloc".
3932 @section Adding a New Target
3934 @cindex adding a target
3935 The following files add a target to @value{GDBN}:
3939 @item gdb/config/@var{arch}/@var{ttt}.mt
3940 Contains a Makefile fragment specific to this target. Specifies what
3941 object files are needed for target @var{ttt}, by defining
3942 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
3943 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
3946 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
3947 but these are now deprecated, replaced by autoconf, and may go away in
3948 future versions of @value{GDBN}.
3950 @item gdb/@var{ttt}-tdep.c
3951 Contains any miscellaneous code required for this target machine. On
3952 some machines it doesn't exist at all. Sometimes the macros in
3953 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
3954 as functions here instead, and the macro is simply defined to call the
3955 function. This is vastly preferable, since it is easier to understand
3958 @item gdb/@var{arch}-tdep.c
3959 @itemx gdb/@var{arch}-tdep.h
3960 This often exists to describe the basic layout of the target machine's
3961 processor chip (registers, stack, etc.). If used, it is included by
3962 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
3965 @item gdb/config/@var{arch}/tm-@var{ttt}.h
3966 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
3967 macro definitions about the target machine's registers, stack frame
3968 format and instructions.
3970 New targets do not need this file and should not create it.
3972 @item gdb/config/@var{arch}/tm-@var{arch}.h
3973 This often exists to describe the basic layout of the target machine's
3974 processor chip (registers, stack, etc.). If used, it is included by
3975 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
3978 New targets do not need this file and should not create it.
3982 If you are adding a new operating system for an existing CPU chip, add a
3983 @file{config/tm-@var{os}.h} file that describes the operating system
3984 facilities that are unusual (extra symbol table info; the breakpoint
3985 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
3986 that just @code{#include}s @file{tm-@var{arch}.h} and
3987 @file{config/tm-@var{os}.h}.
3990 @section Converting an existing Target Architecture to Multi-arch
3991 @cindex converting targets to multi-arch
3993 This section describes the current accepted best practice for converting
3994 an existing target architecture to the multi-arch framework.
3996 The process consists of generating, testing, posting and committing a
3997 sequence of patches. Each patch must contain a single change, for
4003 Directly convert a group of functions into macros (the conversion does
4004 not change the behavior of any of the functions).
4007 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4011 Enable multi-arch level one.
4014 Delete one or more files.
4019 There isn't a size limit on a patch, however, a developer is strongly
4020 encouraged to keep the patch size down.
4022 Since each patch is well defined, and since each change has been tested
4023 and shows no regressions, the patches are considered @emph{fairly}
4024 obvious. Such patches, when submitted by developers listed in the
4025 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4026 process may be more complicated and less clear. The developer is
4027 expected to use their judgment and is encouraged to seek advice as
4030 @subsection Preparation
4032 The first step is to establish control. Build (with @option{-Werror}
4033 enabled) and test the target so that there is a baseline against which
4034 the debugger can be compared.
4036 At no stage can the test results regress or @value{GDBN} stop compiling
4037 with @option{-Werror}.
4039 @subsection Add the multi-arch initialization code
4041 The objective of this step is to establish the basic multi-arch
4042 framework. It involves
4047 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4048 above is from the original example and uses K&R C. @value{GDBN}
4049 has since converted to ISO C but lets ignore that.} that creates
4052 static struct gdbarch *
4053 d10v_gdbarch_init (info, arches)
4054 struct gdbarch_info info;
4055 struct gdbarch_list *arches;
4057 struct gdbarch *gdbarch;
4058 /* there is only one d10v architecture */
4060 return arches->gdbarch;
4061 gdbarch = gdbarch_alloc (&info, NULL);
4069 A per-architecture dump function to print any architecture specific
4073 mips_dump_tdep (struct gdbarch *current_gdbarch,
4074 struct ui_file *file)
4076 @dots{} code to print architecture specific info @dots{}
4081 A change to @code{_initialize_@var{arch}_tdep} to register this new
4085 _initialize_mips_tdep (void)
4087 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4092 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4093 @file{config/@var{arch}/tm-@var{arch}.h}.
4097 @subsection Update multi-arch incompatible mechanisms
4099 Some mechanisms do not work with multi-arch. They include:
4102 @item EXTRA_FRAME_INFO
4104 @item FRAME_FIND_SAVED_REGS
4105 Replaced with @code{FRAME_INIT_SAVED_REGS}
4109 At this stage you could also consider converting the macros into
4112 @subsection Prepare for multi-arch level to one
4114 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4115 and then build and start @value{GDBN} (the change should not be
4116 committed). @value{GDBN} may not build, and once built, it may die with
4117 an internal error listing the architecture methods that must be
4120 Fix any build problems (patch(es)).
4122 Convert all the architecture methods listed, which are only macros, into
4123 functions (patch(es)).
4125 Update @code{@var{arch}_gdbarch_init} to set all the missing
4126 architecture methods and wrap the corresponding macros in @code{#if
4127 !GDB_MULTI_ARCH} (patch(es)).
4129 @subsection Set multi-arch level one
4131 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4134 Any problems with throwing ``the switch'' should have been fixed
4137 @subsection Convert remaining macros
4139 Suggest converting macros into functions (and setting the corresponding
4140 architecture method) in small batches.
4142 @subsection Set multi-arch level to two
4144 This should go smoothly.
4146 @subsection Delete the TM file
4148 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4149 @file{configure.in} updated.
4152 @node Target Vector Definition
4154 @chapter Target Vector Definition
4155 @cindex target vector
4157 The target vector defines the interface between @value{GDBN}'s
4158 abstract handling of target systems, and the nitty-gritty code that
4159 actually exercises control over a process or a serial port.
4160 @value{GDBN} includes some 30-40 different target vectors; however,
4161 each configuration of @value{GDBN} includes only a few of them.
4163 @section File Targets
4165 Both executables and core files have target vectors.
4167 @section Standard Protocol and Remote Stubs
4169 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4170 that runs in the target system. @value{GDBN} provides several sample
4171 @dfn{stubs} that can be integrated into target programs or operating
4172 systems for this purpose; they are named @file{*-stub.c}.
4174 The @value{GDBN} user's manual describes how to put such a stub into
4175 your target code. What follows is a discussion of integrating the
4176 SPARC stub into a complicated operating system (rather than a simple
4177 program), by Stu Grossman, the author of this stub.
4179 The trap handling code in the stub assumes the following upon entry to
4184 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4190 you are in the correct trap window.
4193 As long as your trap handler can guarantee those conditions, then there
4194 is no reason why you shouldn't be able to ``share'' traps with the stub.
4195 The stub has no requirement that it be jumped to directly from the
4196 hardware trap vector. That is why it calls @code{exceptionHandler()},
4197 which is provided by the external environment. For instance, this could
4198 set up the hardware traps to actually execute code which calls the stub
4199 first, and then transfers to its own trap handler.
4201 For the most point, there probably won't be much of an issue with
4202 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4203 and often indicate unrecoverable error conditions. Anyway, this is all
4204 controlled by a table, and is trivial to modify. The most important
4205 trap for us is for @code{ta 1}. Without that, we can't single step or
4206 do breakpoints. Everything else is unnecessary for the proper operation
4207 of the debugger/stub.
4209 From reading the stub, it's probably not obvious how breakpoints work.
4210 They are simply done by deposit/examine operations from @value{GDBN}.
4212 @section ROM Monitor Interface
4214 @section Custom Protocols
4216 @section Transport Layer
4218 @section Builtin Simulator
4221 @node Native Debugging
4223 @chapter Native Debugging
4224 @cindex native debugging
4226 Several files control @value{GDBN}'s configuration for native support:
4230 @item gdb/config/@var{arch}/@var{xyz}.mh
4231 Specifies Makefile fragments needed by a @emph{native} configuration on
4232 machine @var{xyz}. In particular, this lists the required
4233 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4234 Also specifies the header file which describes native support on
4235 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4236 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4237 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4239 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4240 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4241 on machine @var{xyz}. While the file is no longer used for this
4242 purpose, the @file{.mh} suffix remains. Perhaps someone will
4243 eventually rename these fragments so that they have a @file{.mn}
4246 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4247 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4248 macro definitions describing the native system environment, such as
4249 child process control and core file support.
4251 @item gdb/@var{xyz}-nat.c
4252 Contains any miscellaneous C code required for this native support of
4253 this machine. On some machines it doesn't exist at all.
4256 There are some ``generic'' versions of routines that can be used by
4257 various systems. These can be customized in various ways by macros
4258 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4259 the @var{xyz} host, you can just include the generic file's name (with
4260 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4262 Otherwise, if your machine needs custom support routines, you will need
4263 to write routines that perform the same functions as the generic file.
4264 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4265 into @code{NATDEPFILES}.
4269 This contains the @emph{target_ops vector} that supports Unix child
4270 processes on systems which use ptrace and wait to control the child.
4273 This contains the @emph{target_ops vector} that supports Unix child
4274 processes on systems which use /proc to control the child.
4277 This does the low-level grunge that uses Unix system calls to do a ``fork
4278 and exec'' to start up a child process.
4281 This is the low level interface to inferior processes for systems using
4282 the Unix @code{ptrace} call in a vanilla way.
4285 @section Native core file Support
4286 @cindex native core files
4289 @findex fetch_core_registers
4290 @item core-aout.c::fetch_core_registers()
4291 Support for reading registers out of a core file. This routine calls
4292 @code{register_addr()}, see below. Now that BFD is used to read core
4293 files, virtually all machines should use @code{core-aout.c}, and should
4294 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4295 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4297 @item core-aout.c::register_addr()
4298 If your @code{nm-@var{xyz}.h} file defines the macro
4299 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4300 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4301 register number @code{regno}. @code{blockend} is the offset within the
4302 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4303 @file{core-aout.c} will define the @code{register_addr()} function and
4304 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4305 you are using the standard @code{fetch_core_registers()}, you will need
4306 to define your own version of @code{register_addr()}, put it into your
4307 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4308 the @code{NATDEPFILES} list. If you have your own
4309 @code{fetch_core_registers()}, you may not need a separate
4310 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4311 implementations simply locate the registers themselves.@refill
4314 When making @value{GDBN} run native on a new operating system, to make it
4315 possible to debug core files, you will need to either write specific
4316 code for parsing your OS's core files, or customize
4317 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4318 machine uses to define the struct of registers that is accessible
4319 (possibly in the u-area) in a core file (rather than
4320 @file{machine/reg.h}), and an include file that defines whatever header
4321 exists on a core file (e.g. the u-area or a @code{struct core}). Then
4322 modify @code{trad_unix_core_file_p} to use these values to set up the
4323 section information for the data segment, stack segment, any other
4324 segments in the core file (perhaps shared library contents or control
4325 information), ``registers'' segment, and if there are two discontiguous
4326 sets of registers (e.g. integer and float), the ``reg2'' segment. This
4327 section information basically delimits areas in the core file in a
4328 standard way, which the section-reading routines in BFD know how to seek
4331 Then back in @value{GDBN}, you need a matching routine called
4332 @code{fetch_core_registers}. If you can use the generic one, it's in
4333 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4334 It will be passed a char pointer to the entire ``registers'' segment,
4335 its length, and a zero; or a char pointer to the entire ``regs2''
4336 segment, its length, and a 2. The routine should suck out the supplied
4337 register values and install them into @value{GDBN}'s ``registers'' array.
4339 If your system uses @file{/proc} to control processes, and uses ELF
4340 format core files, then you may be able to use the same routines for
4341 reading the registers out of processes and out of core files.
4349 @section shared libraries
4351 @section Native Conditionals
4352 @cindex native conditionals
4354 When @value{GDBN} is configured and compiled, various macros are
4355 defined or left undefined, to control compilation when the host and
4356 target systems are the same. These macros should be defined (or left
4357 undefined) in @file{nm-@var{system}.h}.
4361 @findex ATTACH_DETACH
4362 If defined, then @value{GDBN} will include support for the @code{attach} and
4363 @code{detach} commands.
4365 @item CHILD_PREPARE_TO_STORE
4366 @findex CHILD_PREPARE_TO_STORE
4367 If the machine stores all registers at once in the child process, then
4368 define this to ensure that all values are correct. This usually entails
4369 a read from the child.
4371 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4374 @item FETCH_INFERIOR_REGISTERS
4375 @findex FETCH_INFERIOR_REGISTERS
4376 Define this if the native-dependent code will provide its own routines
4377 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4378 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4379 @file{infptrace.c} is included in this configuration, the default
4380 routines in @file{infptrace.c} are used for these functions.
4382 @item FILES_INFO_HOOK
4383 @findex FILES_INFO_HOOK
4384 (Only defined for Convex.)
4388 This macro is normally defined to be the number of the first floating
4389 point register, if the machine has such registers. As such, it would
4390 appear only in target-specific code. However, @file{/proc} support uses this
4391 to decide whether floats are in use on this target.
4393 @item GET_LONGJMP_TARGET
4394 @findex GET_LONGJMP_TARGET
4395 For most machines, this is a target-dependent parameter. On the
4396 DECstation and the Iris, this is a native-dependent parameter, since
4397 @file{setjmp.h} is needed to define it.
4399 This macro determines the target PC address that @code{longjmp} will jump to,
4400 assuming that we have just stopped at a longjmp breakpoint. It takes a
4401 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4402 pointer. It examines the current state of the machine as needed.
4404 @item I386_USE_GENERIC_WATCHPOINTS
4405 An x86-based machine can define this to use the generic x86 watchpoint
4406 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4409 @findex KERNEL_U_ADDR
4410 Define this to the address of the @code{u} structure (the ``user
4411 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4412 needs to know this so that it can subtract this address from absolute
4413 addresses in the upage, that are obtained via ptrace or from core files.
4414 On systems that don't need this value, set it to zero.
4416 @item KERNEL_U_ADDR_BSD
4417 @findex KERNEL_U_ADDR_BSD
4418 Define this to cause @value{GDBN} to determine the address of @code{u} at
4419 runtime, by using Berkeley-style @code{nlist} on the kernel's image in
4422 @item KERNEL_U_ADDR_HPUX
4423 @findex KERNEL_U_ADDR_HPUX
4424 Define this to cause @value{GDBN} to determine the address of @code{u} at
4425 runtime, by using HP-style @code{nlist} on the kernel's image in the
4428 @item ONE_PROCESS_WRITETEXT
4429 @findex ONE_PROCESS_WRITETEXT
4430 Define this to be able to, when a breakpoint insertion fails, warn the
4431 user that another process may be running with the same executable.
4433 @item PREPARE_TO_PROCEED (@var{select_it})
4434 @findex PREPARE_TO_PROCEED
4435 This (ugly) macro allows a native configuration to customize the way the
4436 @code{proceed} function in @file{infrun.c} deals with switching between
4439 In a multi-threaded task we may select another thread and then continue
4440 or step. But if the old thread was stopped at a breakpoint, it will
4441 immediately cause another breakpoint stop without any execution (i.e. it
4442 will report a breakpoint hit incorrectly). So @value{GDBN} must step over it
4445 If defined, @code{PREPARE_TO_PROCEED} should check the current thread
4446 against the thread that reported the most recent event. If a step-over
4447 is required, it returns TRUE. If @var{select_it} is non-zero, it should
4448 reselect the old thread.
4451 @findex PROC_NAME_FMT
4452 Defines the format for the name of a @file{/proc} device. Should be
4453 defined in @file{nm.h} @emph{only} in order to override the default
4454 definition in @file{procfs.c}.
4457 @findex PTRACE_FP_BUG
4458 See @file{mach386-xdep.c}.
4460 @item PTRACE_ARG3_TYPE
4461 @findex PTRACE_ARG3_TYPE
4462 The type of the third argument to the @code{ptrace} system call, if it
4463 exists and is different from @code{int}.
4465 @item REGISTER_U_ADDR
4466 @findex REGISTER_U_ADDR
4467 Defines the offset of the registers in the ``u area''.
4469 @item SHELL_COMMAND_CONCAT
4470 @findex SHELL_COMMAND_CONCAT
4471 If defined, is a string to prefix on the shell command used to start the
4476 If defined, this is the name of the shell to use to run the inferior.
4477 Defaults to @code{"/bin/sh"}.
4479 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4481 Define this to expand into an expression that will cause the symbols in
4482 @var{filename} to be added to @value{GDBN}'s symbol table. If
4483 @var{readsyms} is zero symbols are not read but any necessary low level
4484 processing for @var{filename} is still done.
4486 @item SOLIB_CREATE_INFERIOR_HOOK
4487 @findex SOLIB_CREATE_INFERIOR_HOOK
4488 Define this to expand into any shared-library-relocation code that you
4489 want to be run just after the child process has been forked.
4491 @item START_INFERIOR_TRAPS_EXPECTED
4492 @findex START_INFERIOR_TRAPS_EXPECTED
4493 When starting an inferior, @value{GDBN} normally expects to trap
4495 the shell execs, and once when the program itself execs. If the actual
4496 number of traps is something other than 2, then define this macro to
4497 expand into the number expected.
4499 @item SVR4_SHARED_LIBS
4500 @findex SVR4_SHARED_LIBS
4501 Define this to indicate that SVR4-style shared libraries are in use.
4505 This determines whether small routines in @file{*-tdep.c}, which
4506 translate register values between @value{GDBN}'s internal
4507 representation and the @file{/proc} representation, are compiled.
4510 @findex U_REGS_OFFSET
4511 This is the offset of the registers in the upage. It need only be
4512 defined if the generic ptrace register access routines in
4513 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4514 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4515 the default value from @file{infptrace.c} is good enough, leave it
4518 The default value means that u.u_ar0 @emph{points to} the location of
4519 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4520 that @code{u.u_ar0} @emph{is} the location of the registers.
4524 See @file{objfiles.c}.
4527 @findex DEBUG_PTRACE
4528 Define this to debug @code{ptrace} calls.
4532 @node Support Libraries
4534 @chapter Support Libraries
4539 BFD provides support for @value{GDBN} in several ways:
4542 @item identifying executable and core files
4543 BFD will identify a variety of file types, including a.out, coff, and
4544 several variants thereof, as well as several kinds of core files.
4546 @item access to sections of files
4547 BFD parses the file headers to determine the names, virtual addresses,
4548 sizes, and file locations of all the various named sections in files
4549 (such as the text section or the data section). @value{GDBN} simply
4550 calls BFD to read or write section @var{x} at byte offset @var{y} for
4553 @item specialized core file support
4554 BFD provides routines to determine the failing command name stored in a
4555 core file, the signal with which the program failed, and whether a core
4556 file matches (i.e.@: could be a core dump of) a particular executable
4559 @item locating the symbol information
4560 @value{GDBN} uses an internal interface of BFD to determine where to find the
4561 symbol information in an executable file or symbol-file. @value{GDBN} itself
4562 handles the reading of symbols, since BFD does not ``understand'' debug
4563 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
4568 @cindex opcodes library
4570 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
4571 library because it's also used in binutils, for @file{objdump}).
4580 @cindex regular expressions library
4591 @item SIGN_EXTEND_CHAR
4593 @item SWITCH_ENUM_BUG
4608 This chapter covers topics that are lower-level than the major
4609 algorithms of @value{GDBN}.
4614 Cleanups are a structured way to deal with things that need to be done
4617 When your code does something (e.g., @code{xmalloc} some memory, or
4618 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
4619 the memory or @code{close} the file), it can make a cleanup. The
4620 cleanup will be done at some future point: when the command is finished
4621 and control returns to the top level; when an error occurs and the stack
4622 is unwound; or when your code decides it's time to explicitly perform
4623 cleanups. Alternatively you can elect to discard the cleanups you
4629 @item struct cleanup *@var{old_chain};
4630 Declare a variable which will hold a cleanup chain handle.
4632 @findex make_cleanup
4633 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
4634 Make a cleanup which will cause @var{function} to be called with
4635 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
4636 handle that can later be passed to @code{do_cleanups} or
4637 @code{discard_cleanups}. Unless you are going to call
4638 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
4639 from @code{make_cleanup}.
4642 @item do_cleanups (@var{old_chain});
4643 Do all cleanups added to the chain since the corresponding
4644 @code{make_cleanup} call was made.
4646 @findex discard_cleanups
4647 @item discard_cleanups (@var{old_chain});
4648 Same as @code{do_cleanups} except that it just removes the cleanups from
4649 the chain and does not call the specified functions.
4652 Cleanups are implemented as a chain. The handle returned by
4653 @code{make_cleanups} includes the cleanup passed to the call and any
4654 later cleanups appended to the chain (but not yet discarded or
4658 make_cleanup (a, 0);
4660 struct cleanup *old = make_cleanup (b, 0);
4668 will call @code{c()} and @code{b()} but will not call @code{a()}. The
4669 cleanup that calls @code{a()} will remain in the cleanup chain, and will
4670 be done later unless otherwise discarded.@refill
4672 Your function should explicitly do or discard the cleanups it creates.
4673 Failing to do this leads to non-deterministic behavior since the caller
4674 will arbitrarily do or discard your functions cleanups. This need leads
4675 to two common cleanup styles.
4677 The first style is try/finally. Before it exits, your code-block calls
4678 @code{do_cleanups} with the old cleanup chain and thus ensures that your
4679 code-block's cleanups are always performed. For instance, the following
4680 code-segment avoids a memory leak problem (even when @code{error} is
4681 called and a forced stack unwind occurs) by ensuring that the
4682 @code{xfree} will always be called:
4685 struct cleanup *old = make_cleanup (null_cleanup, 0);
4686 data = xmalloc (sizeof blah);
4687 make_cleanup (xfree, data);
4692 The second style is try/except. Before it exits, your code-block calls
4693 @code{discard_cleanups} with the old cleanup chain and thus ensures that
4694 any created cleanups are not performed. For instance, the following
4695 code segment, ensures that the file will be closed but only if there is
4699 FILE *file = fopen ("afile", "r");
4700 struct cleanup *old = make_cleanup (close_file, file);
4702 discard_cleanups (old);
4706 Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify
4707 that they ``should not be called when cleanups are not in place''. This
4708 means that any actions you need to reverse in the case of an error or
4709 interruption must be on the cleanup chain before you call these
4710 functions, since they might never return to your code (they
4711 @samp{longjmp} instead).
4713 @section Per-architecture module data
4714 @cindex per-architecture module data
4715 @cindex multi-arch data
4716 @cindex data-pointer, per-architecture/per-module
4718 The multi-arch framework includes a mechanism for adding module specific
4719 per-architecture data-pointers to the @code{struct gdbarch} architecture
4722 A module registers one or more per-architecture data-pointers using the
4723 function @code{register_gdbarch_data}:
4725 @deftypefun struct gdbarch_data *register_gdbarch_data (gdbarch_data_init_ftype *@var{init}, gdbarch_data_free_ftype *@var{free})
4727 The @var{init} function is used to obtain an initial value for a
4728 per-architecture data-pointer. The function is called, after the
4729 architecture has been created, when the data-pointer is still
4730 uninitialized (@code{NULL}) and its value has been requested via a call
4731 to @code{gdbarch_data}. A data-pointer can also be initialize
4732 explicitly using @code{set_gdbarch_data}.
4734 The @var{free} function is called when a data-pointer needs to be
4735 destroyed. This occurs when either the corresponding @code{struct
4736 gdbarch} object is being destroyed or when @code{set_gdbarch_data} is
4737 overriding a non-@code{NULL} data-pointer value.
4739 The function @code{register_gdbarch_data} returns a @code{struct
4740 gdbarch_data} that is used to identify the data-pointer that was added
4745 A typical module has @code{init} and @code{free} functions of the form:
4748 static struct gdbarch_data *nozel_handle;
4750 nozel_init (struct gdbarch *gdbarch)
4752 struct nozel *data = XMALLOC (struct nozel);
4758 nozel_free (struct gdbarch *gdbarch, void *data)
4764 Since uninitialized (@code{NULL}) data-pointers are initialized
4765 on-demand, an @code{init} function is free to call other modules that
4766 use data-pointers. Those modules data-pointers will be initialized as
4767 needed. Care should be taken to ensure that the @code{init} call graph
4768 does not contain cycles.
4770 The data-pointer is registered with the call:
4774 _initialize_nozel (void)
4776 nozel_handle = register_gdbarch_data (nozel_init, nozel_free);
4780 The per-architecture data-pointer is accessed using the function:
4782 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
4783 Given the architecture @var{arch} and module data handle
4784 @var{data_handle} (returned by @code{register_gdbarch_data}, this
4785 function returns the current value of the per-architecture data-pointer.
4788 The non-@code{NULL} data-pointer returned by @code{gdbarch_data} should
4789 be saved in a local variable and then used directly:
4793 nozel_total (struct gdbarch *gdbarch)
4796 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
4802 It is also possible to directly initialize the data-pointer using:
4804 @deftypefun void set_gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *handle, void *@var{pointer})
4805 Update the data-pointer corresponding to @var{handle} with the value of
4806 @var{pointer}. If the previous data-pointer value is non-NULL, then it
4807 is freed using data-pointers @var{free} function.
4810 This function is used by modules that require a mechanism for explicitly
4811 setting the per-architecture data-pointer during architecture creation:
4814 /* Called during architecture creation. */
4816 set_gdbarch_nozel (struct gdbarch *gdbarch,
4819 struct nozel *data = XMALLOC (struct nozel);
4821 set_gdbarch_data (gdbarch, nozel_handle, nozel);
4826 /* Default, called when nozel not set by set_gdbarch_nozel(). */
4828 nozel_init (struct gdbarch *gdbarch)
4830 struct nozel *default_nozel = XMALLOC (struc nozel);
4832 return default_nozel;
4838 _initialize_nozel (void)
4840 nozel_handle = register_gdbarch_data (nozel_init, NULL);
4845 Note that an @code{init} function still needs to be registered. It is
4846 used to initialize the data-pointer when the architecture creation phase
4847 fail to set an initial value.
4850 @section Wrapping Output Lines
4851 @cindex line wrap in output
4854 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
4855 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
4856 added in places that would be good breaking points. The utility
4857 routines will take care of actually wrapping if the line width is
4860 The argument to @code{wrap_here} is an indentation string which is
4861 printed @emph{only} if the line breaks there. This argument is saved
4862 away and used later. It must remain valid until the next call to
4863 @code{wrap_here} or until a newline has been printed through the
4864 @code{*_filtered} functions. Don't pass in a local variable and then
4867 It is usually best to call @code{wrap_here} after printing a comma or
4868 space. If you call it before printing a space, make sure that your
4869 indentation properly accounts for the leading space that will print if
4870 the line wraps there.
4872 Any function or set of functions that produce filtered output must
4873 finish by printing a newline, to flush the wrap buffer, before switching
4874 to unfiltered (@code{printf}) output. Symbol reading routines that
4875 print warnings are a good example.
4877 @section @value{GDBN} Coding Standards
4878 @cindex coding standards
4880 @value{GDBN} follows the GNU coding standards, as described in
4881 @file{etc/standards.texi}. This file is also available for anonymous
4882 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
4883 of the standard; in general, when the GNU standard recommends a practice
4884 but does not require it, @value{GDBN} requires it.
4886 @value{GDBN} follows an additional set of coding standards specific to
4887 @value{GDBN}, as described in the following sections.
4892 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
4895 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
4898 @subsection Memory Management
4900 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
4901 @code{calloc}, @code{free} and @code{asprintf}.
4903 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
4904 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
4905 these functions do not return when the memory pool is empty. Instead,
4906 they unwind the stack using cleanups. These functions return
4907 @code{NULL} when requested to allocate a chunk of memory of size zero.
4909 @emph{Pragmatics: By using these functions, the need to check every
4910 memory allocation is removed. These functions provide portable
4913 @value{GDBN} does not use the function @code{free}.
4915 @value{GDBN} uses the function @code{xfree} to return memory to the
4916 memory pool. Consistent with ISO-C, this function ignores a request to
4917 free a @code{NULL} pointer.
4919 @emph{Pragmatics: On some systems @code{free} fails when passed a
4920 @code{NULL} pointer.}
4922 @value{GDBN} can use the non-portable function @code{alloca} for the
4923 allocation of small temporary values (such as strings).
4925 @emph{Pragmatics: This function is very non-portable. Some systems
4926 restrict the memory being allocated to no more than a few kilobytes.}
4928 @value{GDBN} uses the string function @code{xstrdup} and the print
4929 function @code{xasprintf}.
4931 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
4932 functions such as @code{sprintf} are very prone to buffer overflow
4936 @subsection Compiler Warnings
4937 @cindex compiler warnings
4939 With few exceptions, developers should include the configuration option
4940 @samp{--enable-gdb-build-warnings=,-Werror} when building @value{GDBN}.
4941 The exceptions are listed in the file @file{gdb/MAINTAINERS}.
4943 This option causes @value{GDBN} (when built using GCC) to be compiled
4944 with a carefully selected list of compiler warning flags. Any warnings
4945 from those flags being treated as errors.
4947 The current list of warning flags includes:
4951 Since @value{GDBN} coding standard requires all functions to be declared
4952 using a prototype, the flag has the side effect of ensuring that
4953 prototyped functions are always visible with out resorting to
4954 @samp{-Wstrict-prototypes}.
4957 Such code often appears to work except on instruction set architectures
4958 that use register windows.
4965 Since @value{GDBN} uses the @code{format printf} attribute on all
4966 @code{printf} like functions this checks not just @code{printf} calls
4967 but also calls to functions such as @code{fprintf_unfiltered}.
4970 This warning includes uses of the assignment operator within an
4971 @code{if} statement.
4973 @item -Wpointer-arith
4975 @item -Wuninitialized
4978 @emph{Pragmatics: Due to the way that @value{GDBN} is implemented most
4979 functions have unused parameters. Consequently the warning
4980 @samp{-Wunused-parameter} is precluded from the list. The macro
4981 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
4982 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
4983 is being used. The options @samp{-Wall} and @samp{-Wunused} are also
4984 precluded because they both include @samp{-Wunused-parameter}.}
4986 @emph{Pragmatics: @value{GDBN} has not simply accepted the warnings
4987 enabled by @samp{-Wall -Werror -W...}. Instead it is selecting warnings
4988 when and where their benefits can be demonstrated.}
4990 @subsection Formatting
4992 @cindex source code formatting
4993 The standard GNU recommendations for formatting must be followed
4996 A function declaration should not have its name in column zero. A
4997 function definition should have its name in column zero.
5001 static void foo (void);
5009 @emph{Pragmatics: This simplifies scripting. Function definitions can
5010 be found using @samp{^function-name}.}
5012 There must be a space between a function or macro name and the opening
5013 parenthesis of its argument list (except for macro definitions, as
5014 required by C). There must not be a space after an open paren/bracket
5015 or before a close paren/bracket.
5017 While additional whitespace is generally helpful for reading, do not use
5018 more than one blank line to separate blocks, and avoid adding whitespace
5019 after the end of a program line (as of 1/99, some 600 lines had
5020 whitespace after the semicolon). Excess whitespace causes difficulties
5021 for @code{diff} and @code{patch} utilities.
5023 Pointers are declared using the traditional K&R C style:
5037 @subsection Comments
5039 @cindex comment formatting
5040 The standard GNU requirements on comments must be followed strictly.
5042 Block comments must appear in the following form, with no @code{/*}- or
5043 @code{*/}-only lines, and no leading @code{*}:
5046 /* Wait for control to return from inferior to debugger. If inferior
5047 gets a signal, we may decide to start it up again instead of
5048 returning. That is why there is a loop in this function. When
5049 this function actually returns it means the inferior should be left
5050 stopped and @value{GDBN} should read more commands. */
5053 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5054 comment works correctly, and @kbd{M-q} fills the block consistently.)
5056 Put a blank line between the block comments preceding function or
5057 variable definitions, and the definition itself.
5059 In general, put function-body comments on lines by themselves, rather
5060 than trying to fit them into the 20 characters left at the end of a
5061 line, since either the comment or the code will inevitably get longer
5062 than will fit, and then somebody will have to move it anyhow.
5066 @cindex C data types
5067 Code must not depend on the sizes of C data types, the format of the
5068 host's floating point numbers, the alignment of anything, or the order
5069 of evaluation of expressions.
5071 @cindex function usage
5072 Use functions freely. There are only a handful of compute-bound areas
5073 in @value{GDBN} that might be affected by the overhead of a function
5074 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5075 limited by the target interface (whether serial line or system call).
5077 However, use functions with moderation. A thousand one-line functions
5078 are just as hard to understand as a single thousand-line function.
5080 @emph{Macros are bad, M'kay.}
5081 (But if you have to use a macro, make sure that the macro arguments are
5082 protected with parentheses.)
5086 Declarations like @samp{struct foo *} should be used in preference to
5087 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5090 @subsection Function Prototypes
5091 @cindex function prototypes
5093 Prototypes must be used when both @emph{declaring} and @emph{defining}
5094 a function. Prototypes for @value{GDBN} functions must include both the
5095 argument type and name, with the name matching that used in the actual
5096 function definition.
5098 All external functions should have a declaration in a header file that
5099 callers include, except for @code{_initialize_*} functions, which must
5100 be external so that @file{init.c} construction works, but shouldn't be
5101 visible to random source files.
5103 Where a source file needs a forward declaration of a static function,
5104 that declaration must appear in a block near the top of the source file.
5107 @subsection Internal Error Recovery
5109 During its execution, @value{GDBN} can encounter two types of errors.
5110 User errors and internal errors. User errors include not only a user
5111 entering an incorrect command but also problems arising from corrupt
5112 object files and system errors when interacting with the target.
5113 Internal errors include situations where @value{GDBN} has detected, at
5114 run time, a corrupt or erroneous situation.
5116 When reporting an internal error, @value{GDBN} uses
5117 @code{internal_error} and @code{gdb_assert}.
5119 @value{GDBN} must not call @code{abort} or @code{assert}.
5121 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5122 the code detected a user error, recovered from it and issued a
5123 @code{warning} or the code failed to correctly recover from the user
5124 error and issued an @code{internal_error}.}
5126 @subsection File Names
5128 Any file used when building the core of @value{GDBN} must be in lower
5129 case. Any file used when building the core of @value{GDBN} must be 8.3
5130 unique. These requirements apply to both source and generated files.
5132 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5133 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5134 is introduced to the build process both @file{Makefile.in} and
5135 @file{configure.in} need to be modified accordingly. Compare the
5136 convoluted conversion process needed to transform @file{COPYING} into
5137 @file{copying.c} with the conversion needed to transform
5138 @file{version.in} into @file{version.c}.}
5140 Any file non 8.3 compliant file (that is not used when building the core
5141 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5143 @emph{Pragmatics: This is clearly a compromise.}
5145 When @value{GDBN} has a local version of a system header file (ex
5146 @file{string.h}) the file name based on the POSIX header prefixed with
5147 @file{gdb_} (@file{gdb_string.h}).
5149 For other files @samp{-} is used as the separator.
5152 @subsection Include Files
5154 A @file{.c} file should include @file{defs.h} first.
5156 A @file{.c} file should directly include the @code{.h} file of every
5157 declaration and/or definition it directly refers to. It cannot rely on
5160 A @file{.h} file should directly include the @code{.h} file of every
5161 declaration and/or definition it directly refers to. It cannot rely on
5162 indirect inclusion. Exception: The file @file{defs.h} does not need to
5163 be directly included.
5165 An external declaration should only appear in one include file.
5167 An external declaration should never appear in a @code{.c} file.
5168 Exception: a declaration for the @code{_initialize} function that
5169 pacifies @option{-Wmissing-declaration}.
5171 A @code{typedef} definition should only appear in one include file.
5173 An opaque @code{struct} declaration can appear in multiple @file{.h}
5174 files. Where possible, a @file{.h} file should use an opaque
5175 @code{struct} declaration instead of an include.
5177 All @file{.h} files should be wrapped in:
5180 #ifndef INCLUDE_FILE_NAME_H
5181 #define INCLUDE_FILE_NAME_H
5187 @subsection Clean Design and Portable Implementation
5190 In addition to getting the syntax right, there's the little question of
5191 semantics. Some things are done in certain ways in @value{GDBN} because long
5192 experience has shown that the more obvious ways caused various kinds of
5195 @cindex assumptions about targets
5196 You can't assume the byte order of anything that comes from a target
5197 (including @var{value}s, object files, and instructions). Such things
5198 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5199 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5200 such as @code{bfd_get_32}.
5202 You can't assume that you know what interface is being used to talk to
5203 the target system. All references to the target must go through the
5204 current @code{target_ops} vector.
5206 You can't assume that the host and target machines are the same machine
5207 (except in the ``native'' support modules). In particular, you can't
5208 assume that the target machine's header files will be available on the
5209 host machine. Target code must bring along its own header files --
5210 written from scratch or explicitly donated by their owner, to avoid
5214 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5215 to write the code portably than to conditionalize it for various
5218 @cindex system dependencies
5219 New @code{#ifdef}'s which test for specific compilers or manufacturers
5220 or operating systems are unacceptable. All @code{#ifdef}'s should test
5221 for features. The information about which configurations contain which
5222 features should be segregated into the configuration files. Experience
5223 has proven far too often that a feature unique to one particular system
5224 often creeps into other systems; and that a conditional based on some
5225 predefined macro for your current system will become worthless over
5226 time, as new versions of your system come out that behave differently
5227 with regard to this feature.
5229 Adding code that handles specific architectures, operating systems,
5230 target interfaces, or hosts, is not acceptable in generic code.
5232 @cindex portable file name handling
5233 @cindex file names, portability
5234 One particularly notorious area where system dependencies tend to
5235 creep in is handling of file names. The mainline @value{GDBN} code
5236 assumes Posix semantics of file names: absolute file names begin with
5237 a forward slash @file{/}, slashes are used to separate leading
5238 directories, case-sensitive file names. These assumptions are not
5239 necessarily true on non-Posix systems such as MS-Windows. To avoid
5240 system-dependent code where you need to take apart or construct a file
5241 name, use the following portable macros:
5244 @findex HAVE_DOS_BASED_FILE_SYSTEM
5245 @item HAVE_DOS_BASED_FILE_SYSTEM
5246 This preprocessing symbol is defined to a non-zero value on hosts
5247 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5248 symbol to write conditional code which should only be compiled for
5251 @findex IS_DIR_SEPARATOR
5252 @item IS_DIR_SEPARATOR (@var{c})
5253 Evaluates to a non-zero value if @var{c} is a directory separator
5254 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5255 such a character, but on Windows, both @file{/} and @file{\} will
5258 @findex IS_ABSOLUTE_PATH
5259 @item IS_ABSOLUTE_PATH (@var{file})
5260 Evaluates to a non-zero value if @var{file} is an absolute file name.
5261 For Unix and GNU/Linux hosts, a name which begins with a slash
5262 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5263 @file{x:\bar} are also absolute file names.
5265 @findex FILENAME_CMP
5266 @item FILENAME_CMP (@var{f1}, @var{f2})
5267 Calls a function which compares file names @var{f1} and @var{f2} as
5268 appropriate for the underlying host filesystem. For Posix systems,
5269 this simply calls @code{strcmp}; on case-insensitive filesystems it
5270 will call @code{strcasecmp} instead.
5272 @findex DIRNAME_SEPARATOR
5273 @item DIRNAME_SEPARATOR
5274 Evaluates to a character which separates directories in
5275 @code{PATH}-style lists, typically held in environment variables.
5276 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5278 @findex SLASH_STRING
5280 This evaluates to a constant string you should use to produce an
5281 absolute filename from leading directories and the file's basename.
5282 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5283 @code{"\\"} for some Windows-based ports.
5286 In addition to using these macros, be sure to use portable library
5287 functions whenever possible. For example, to extract a directory or a
5288 basename part from a file name, use the @code{dirname} and
5289 @code{basename} library functions (available in @code{libiberty} for
5290 platforms which don't provide them), instead of searching for a slash
5291 with @code{strrchr}.
5293 Another way to generalize @value{GDBN} along a particular interface is with an
5294 attribute struct. For example, @value{GDBN} has been generalized to handle
5295 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5296 by defining the @code{target_ops} structure and having a current target (as
5297 well as a stack of targets below it, for memory references). Whenever
5298 something needs to be done that depends on which remote interface we are
5299 using, a flag in the current target_ops structure is tested (e.g.,
5300 @code{target_has_stack}), or a function is called through a pointer in the
5301 current target_ops structure. In this way, when a new remote interface
5302 is added, only one module needs to be touched---the one that actually
5303 implements the new remote interface. Other examples of
5304 attribute-structs are BFD access to multiple kinds of object file
5305 formats, or @value{GDBN}'s access to multiple source languages.
5307 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5308 the code interfacing between @code{ptrace} and the rest of
5309 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5310 something was very painful. In @value{GDBN} 4.x, these have all been
5311 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5312 with variations between systems the same way any system-independent
5313 file would (hooks, @code{#if defined}, etc.), and machines which are
5314 radically different don't need to use @file{infptrace.c} at all.
5316 All debugging code must be controllable using the @samp{set debug
5317 @var{module}} command. Do not use @code{printf} to print trace
5318 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5319 @code{#ifdef DEBUG}.
5324 @chapter Porting @value{GDBN}
5325 @cindex porting to new machines
5327 Most of the work in making @value{GDBN} compile on a new machine is in
5328 specifying the configuration of the machine. This is done in a
5329 dizzying variety of header files and configuration scripts, which we
5330 hope to make more sensible soon. Let's say your new host is called an
5331 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
5332 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
5333 @samp{sparc-sun-sunos4}). In particular:
5337 In the top level directory, edit @file{config.sub} and add @var{arch},
5338 @var{xvend}, and @var{xos} to the lists of supported architectures,
5339 vendors, and operating systems near the bottom of the file. Also, add
5340 @var{xyz} as an alias that maps to
5341 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
5345 ./config.sub @var{xyz}
5352 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
5356 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
5357 and no error messages.
5360 You need to port BFD, if that hasn't been done already. Porting BFD is
5361 beyond the scope of this manual.
5364 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
5365 your system and set @code{gdb_host} to @var{xyz}, and (unless your
5366 desired target is already available) also edit @file{gdb/configure.tgt},
5367 setting @code{gdb_target} to something appropriate (for instance,
5370 @emph{Maintainer's note: Work in progress. The file
5371 @file{gdb/configure.host} originally needed to be modified when either a
5372 new native target or a new host machine was being added to @value{GDBN}.
5373 Recent changes have removed this requirement. The file now only needs
5374 to be modified when adding a new native configuration. This will likely
5375 changed again in the future.}
5378 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
5379 target-dependent @file{.h} and @file{.c} files used for your
5385 @chapter Releasing @value{GDBN}
5386 @cindex making a new release of gdb
5388 @section Versions and Branches
5390 @subsection Version Identifiers
5392 @value{GDBN}'s version is determined by the file @file{gdb/version.in}.
5394 @value{GDBN}'s mainline uses ISO dates to differentiate between
5395 versions. The CVS repository uses @var{YYYY}-@var{MM}-@var{DD}-cvs
5396 while the corresponding snapshot uses @var{YYYYMMDD}.
5398 @value{GDBN}'s release branch uses a slightly more complicated scheme.
5399 When the branch is first cut, the mainline version identifier is
5400 prefixed with the @var{major}.@var{minor} from of the previous release
5401 series but with .90 appended. As draft releases are drawn from the
5402 branch, the minor minor number (.90) is incremented. Once the first
5403 release (@var{M}.@var{N}) has been made, the version prefix is updated
5404 to @var{M}.@var{N}.0.90 (dot zero, dot ninety). Follow on releases have
5405 an incremented minor minor version number (.0).
5407 Using 5.1 (previous) and 5.2 (current), the example below illustrates a
5408 typical sequence of version identifiers:
5412 final release from previous branch
5413 @item 2002-03-03-cvs
5414 main-line the day the branch is cut
5415 @item 5.1.90-2002-03-03-cvs
5416 corresponding branch version
5418 first draft release candidate
5419 @item 5.1.91-2002-03-17-cvs
5420 updated branch version
5422 second draft release candidate
5423 @item 5.1.92-2002-03-31-cvs
5424 updated branch version
5426 final release candidate (see below)
5429 @item 5.2.0.90-2002-04-07-cvs
5430 updated CVS branch version
5432 second official release
5439 Minor minor minor draft release candidates such as 5.2.0.91 have been
5440 omitted from the example. Such release candidates are, typically, never
5443 For 5.1.93 the bziped tar ball @file{gdb-5.1.93.tar.bz2} is just the
5444 official @file{gdb-5.2.tar} renamed and compressed.
5447 To avoid version conflicts, vendors are expected to modify the file
5448 @file{gdb/version.in} to include a vendor unique alphabetic identifier
5449 (an official @value{GDBN} release never uses alphabetic characters in
5450 its version identifer).
5452 Since @value{GDBN} does not make minor minor minor releases (e.g.,
5453 5.1.0.1) the conflict between that and a minor minor draft release
5454 identifier (e.g., 5.1.0.90) is avoided.
5457 @subsection Branches
5459 @value{GDBN} draws a release series (5.2, 5.2.1, @dots{}) from a single
5460 release branch (gdb_5_2-branch). Since minor minor minor releases
5461 (5.1.0.1) are not made, the need to branch the release branch is avoided
5462 (it also turns out that the effort required for such a a branch and
5463 release is significantly greater than the effort needed to create a new
5464 release from the head of the release branch).
5466 Releases 5.0 and 5.1 used branch and release tags of the form:
5469 gdb_N_M-YYYY-MM-DD-branchpoint
5470 gdb_N_M-YYYY-MM-DD-branch
5471 gdb_M_N-YYYY-MM-DD-release
5474 Release 5.2 is trialing the branch and release tags:
5477 gdb_N_M-YYYY-MM-DD-branchpoint
5479 gdb_M_N-YYYY-MM-DD-release
5482 @emph{Pragmatics: The branchpoint and release tags need to identify when
5483 a branch and release are made. The branch tag, denoting the head of the
5484 branch, does not have this criteria.}
5487 @section Branch Commit Policy
5489 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
5490 5.1 and 5.2 all used the below:
5494 The @file{gdb/MAINTAINERS} file still holds.
5496 Don't fix something on the branch unless/until it is also fixed in the
5497 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
5498 file is better than committing a hack.
5500 When considering a patch for the branch, suggested criteria include:
5501 Does it fix a build? Does it fix the sequence @kbd{break main; run}
5502 when debugging a static binary?
5504 The further a change is from the core of @value{GDBN}, the less likely
5505 the change will worry anyone (e.g., target specific code).
5507 Only post a proposal to change the core of @value{GDBN} after you've
5508 sent individual bribes to all the people listed in the
5509 @file{MAINTAINERS} file @t{;-)}
5512 @emph{Pragmatics: Provided updates are restricted to non-core
5513 functionality there is little chance that a broken change will be fatal.
5514 This means that changes such as adding a new architectures or (within
5515 reason) support for a new host are considered acceptable.}
5518 @section Obsoleting code
5520 Before anything else, poke the other developers (and around the source
5521 code) to see if there is anything that can be removed from @value{GDBN}
5522 (an old target, an unused file).
5524 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
5525 line. Doing this means that it is easy to identify something that has
5526 been obsoleted when greping through the sources.
5528 The process is done in stages --- this is mainly to ensure that the
5529 wider @value{GDBN} community has a reasonable opportunity to respond.
5530 Remember, everything on the Internet takes a week.
5534 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
5535 list} Creating a bug report to track the task's state, is also highly
5540 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
5541 Announcement mailing list}.
5545 Go through and edit all relevant files and lines so that they are
5546 prefixed with the word @code{OBSOLETE}.
5548 Wait until the next GDB version, containing this obsolete code, has been
5551 Remove the obsolete code.
5555 @emph{Maintainer note: While removing old code is regrettable it is
5556 hopefully better for @value{GDBN}'s long term development. Firstly it
5557 helps the developers by removing code that is either no longer relevant
5558 or simply wrong. Secondly since it removes any history associated with
5559 the file (effectively clearing the slate) the developer has a much freer
5560 hand when it comes to fixing broken files.}
5564 @section Before the Branch
5566 The most important objective at this stage is to find and fix simple
5567 changes that become a pain to track once the branch is created. For
5568 instance, configuration problems that stop @value{GDBN} from even
5569 building. If you can't get the problem fixed, document it in the
5570 @file{gdb/PROBLEMS} file.
5572 @subheading Prompt for @file{gdb/NEWS}
5574 People always forget. Send a post reminding them but also if you know
5575 something interesting happened add it yourself. The @code{schedule}
5576 script will mention this in its e-mail.
5578 @subheading Review @file{gdb/README}
5580 Grab one of the nightly snapshots and then walk through the
5581 @file{gdb/README} looking for anything that can be improved. The
5582 @code{schedule} script will mention this in its e-mail.
5584 @subheading Refresh any imported files.
5586 A number of files are taken from external repositories. They include:
5590 @file{texinfo/texinfo.tex}
5592 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
5595 @file{etc/standards.texi}, @file{etc/make-stds.texi}
5598 @subheading Check the ARI
5600 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
5601 (Awk Regression Index ;-) that checks for a number of errors and coding
5602 conventions. The checks include things like using @code{malloc} instead
5603 of @code{xmalloc} and file naming problems. There shouldn't be any
5606 @subsection Review the bug data base
5608 Close anything obviously fixed.
5610 @subsection Check all cross targets build
5612 The targets are listed in @file{gdb/MAINTAINERS}.
5615 @section Cut the Branch
5617 @subheading Create the branch
5622 $ V=`echo $v | sed 's/\./_/g'`
5623 $ D=`date -u +%Y-%m-%d`
5626 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5627 -D $D-gmt gdb_$V-$D-branchpoint insight+dejagnu
5628 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
5629 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight+dejagnu
5632 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5633 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight+dejagnu
5634 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5635 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight+dejagnu
5643 by using @kbd{-D YYYY-MM-DD-gmt} the branch is forced to an exact
5646 the trunk is first taged so that the branch point can easily be found
5648 Insight (which includes GDB) and dejagnu are all tagged at the same time
5650 @file{version.in} gets bumped to avoid version number conflicts
5652 the reading of @file{.cvsrc} is disabled using @file{-f}
5655 @subheading Update @file{version.in}
5660 $ V=`echo $v | sed 's/\./_/g'`
5664 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
5665 -r gdb_$V-branch src/gdb/version.in
5666 cvs -f -d :ext:sources.redhat.com:/cvs/src co
5667 -r gdb_5_2-branch src/gdb/version.in
5669 U src/gdb/version.in
5671 $ echo $u.90-0000-00-00-cvs > version.in
5673 5.1.90-0000-00-00-cvs
5674 $ cvs -f commit version.in
5679 @file{0000-00-00} is used as a date to pump prime the version.in update
5682 @file{.90} and the previous branch version are used as fairly arbitrary
5683 initial branch version number
5687 @subheading Update the web and news pages
5691 @subheading Tweak cron to track the new branch
5693 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
5694 This file needs to be updated so that:
5698 a daily timestamp is added to the file @file{version.in}
5700 the new branch is included in the snapshot process
5704 See the file @file{gdbadmin/cron/README} for how to install the updated
5707 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
5708 any changes. That file is copied to both the branch/ and current/
5709 snapshot directories.
5712 @subheading Update the NEWS and README files
5714 The @file{NEWS} file needs to be updated so that on the branch it refers
5715 to @emph{changes in the current release} while on the trunk it also
5716 refers to @emph{changes since the current release}.
5718 The @file{README} file needs to be updated so that it refers to the
5721 @subheading Post the branch info
5723 Send an announcement to the mailing lists:
5727 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
5729 @email{gdb@@sources.redhat.com, GDB Discsussion mailing list} and
5730 @email{gdb-testers@@sources.redhat.com, GDB Discsussion mailing list}
5733 @emph{Pragmatics: The branch creation is sent to the announce list to
5734 ensure that people people not subscribed to the higher volume discussion
5737 The announcement should include:
5743 how to check out the branch using CVS
5745 the date/number of weeks until the release
5747 the branch commit policy
5751 @section Stabilize the branch
5753 Something goes here.
5755 @section Create a Release
5757 The process of creating and then making available a release is broken
5758 down into a number of stages. The first part addresses the technical
5759 process of creating a releasable tar ball. The later stages address the
5760 process of releasing that tar ball.
5762 When making a release candidate just the first section is needed.
5764 @subsection Create a release candidate
5766 The objective at this stage is to create a set of tar balls that can be
5767 made available as a formal release (or as a less formal release
5770 @subsubheading Freeze the branch
5772 Send out an e-mail notifying everyone that the branch is frozen to
5773 @email{gdb-patches@@sources.redhat.com}.
5775 @subsubheading Establish a few defaults.
5780 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
5782 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5786 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5788 /home/gdbadmin/bin/autoconf
5797 Check the @code{autoconf} version carefully. You want to be using the
5798 version taken from the @file{binutils} snapshot directory, which can be
5799 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
5800 unlikely that a system installed version of @code{autoconf} (e.g.,
5801 @file{/usr/bin/autoconf}) is correct.
5804 @subsubheading Check out the relevant modules:
5807 $ for m in gdb insight dejagnu
5809 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
5819 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
5820 any confusion between what is written here and what your local
5821 @code{cvs} really does.
5824 @subsubheading Update relevant files.
5830 Major releases get their comments added as part of the mainline. Minor
5831 releases should probably mention any significant bugs that were fixed.
5833 Don't forget to include the @file{ChangeLog} entry.
5836 $ emacs gdb/src/gdb/NEWS
5841 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
5842 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5847 You'll need to update:
5859 $ emacs gdb/src/gdb/README
5864 $ cp gdb/src/gdb/README insight/src/gdb/README
5865 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5868 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
5869 before the initial branch was cut so just a simple substitute is needed
5872 @emph{Maintainer note: Other projects generate @file{README} and
5873 @file{INSTALL} from the core documentation. This might be worth
5876 @item gdb/version.in
5879 $ echo $v > gdb/src/gdb/version.in
5880 $ cat gdb/src/gdb/version.in
5882 $ emacs gdb/src/gdb/version.in
5885 ... Bump to version ...
5887 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
5888 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5891 @item dejagnu/src/dejagnu/configure.in
5893 Dejagnu is more complicated. The version number is a parameter to
5894 @code{AM_INIT_AUTOMAKE}. Tweak it to read something like gdb-5.1.91.
5896 Don't forget to re-generate @file{configure}.
5898 Don't forget to include a @file{ChangeLog} entry.
5901 $ emacs dejagnu/src/dejagnu/configure.in
5906 $ ( cd dejagnu/src/dejagnu && autoconf )
5911 @subsubheading Do the dirty work
5913 This is identical to the process used to create the daily snapshot.
5916 $ for m in gdb insight
5918 ( cd $m/src && gmake -f src-release $m.tar )
5920 $ ( m=dejagnu; cd $m/src && gmake -f src-release $m.tar.bz2 )
5923 If the top level source directory does not have @file{src-release}
5924 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
5927 $ for m in gdb insight
5929 ( cd $m/src && gmake -f Makefile.in $m.tar )
5931 $ ( m=dejagnu; cd $m/src && gmake -f Makefile.in $m.tar.bz2 )
5934 @subsubheading Check the source files
5936 You're looking for files that have mysteriously disappeared.
5937 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
5938 for the @file{version.in} update @kbd{cronjob}.
5941 $ ( cd gdb/src && cvs -f -q -n update )
5945 @dots{} lots of generated files @dots{}
5950 @dots{} lots of generated files @dots{}
5955 @emph{Don't worry about the @file{gdb.info-??} or
5956 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
5957 was also generated only something strange with CVS means that they
5958 didn't get supressed). Fixing it would be nice though.}
5960 @subsubheading Create compressed versions of the release
5966 dejagnu/ dejagnu-gdb-5.2.tar.bz2 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
5967 $ for m in gdb insight
5969 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
5970 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
5980 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
5981 in that mode, @code{gzip} does not know the name of the file and, hence,
5982 can not include it in the compressed file. This is also why the release
5983 process runs @code{tar} and @code{bzip2} as separate passes.
5986 @subsection Sanity check the tar ball
5988 Pick a popular machine (Solaris/PPC?) and try the build on that.
5991 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
5996 $ ./gdb/gdb ./gdb/gdb
6000 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6002 Starting program: /tmp/gdb-5.2/gdb/gdb
6004 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6005 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6007 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6011 @subsection Make a release candidate available
6013 If this is a release candidate then the only remaining steps are:
6017 Commit @file{version.in} and @file{ChangeLog}
6019 Tweak @file{version.in} (and @file{ChangeLog} to read
6020 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6021 process can restart.
6023 Make the release candidate available in
6024 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6026 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6027 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6030 @subsection Make a formal release available
6032 (And you thought all that was required was to post an e-mail.)
6034 @subsubheading Install on sware
6036 Copy the new files to both the release and the old release directory:
6039 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6040 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6044 Clean up the releases directory so that only the most recent releases
6045 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6048 $ cd ~ftp/pub/gdb/releases
6053 Update the file @file{README} and @file{.message} in the releases
6060 $ ln README .message
6063 @subsubheading Update the web pages.
6067 @item htdocs/download/ANNOUNCEMENT
6068 This file, which is posted as the official announcement, includes:
6071 General announcement
6073 News. If making an @var{M}.@var{N}.1 release, retain the news from
6074 earlier @var{M}.@var{N} release.
6079 @item htdocs/index.html
6080 @itemx htdocs/news/index.html
6081 @itemx htdocs/download/index.html
6082 These files include:
6085 announcement of the most recent release
6087 news entry (remember to update both the top level and the news directory).
6089 These pages also need to be regenerate using @code{index.sh}.
6091 @item download/onlinedocs/
6092 You need to find the magic command that is used to generate the online
6093 docs from the @file{.tar.bz2}. The best way is to look in the output
6094 from one of the nightly @code{cron} jobs and then just edit accordingly.
6098 $ ~/ss/update-web-docs \
6099 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6101 /www/sourceware/htdocs/gdb/download/onlinedocs \
6106 Just like the online documentation. Something like:
6109 $ /bin/sh ~/ss/update-web-ari \
6110 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6112 /www/sourceware/htdocs/gdb/download/ari \
6118 @subsubheading Shadow the pages onto gnu
6120 Something goes here.
6123 @subsubheading Install the @value{GDBN} tar ball on GNU
6125 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6126 @file{~ftp/gnu/gdb}.
6128 @subsubheading Make the @file{ANNOUNCEMENT}
6130 Post the @file{ANNOUNCEMENT} file you created above to:
6134 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6136 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6137 day or so to let things get out)
6139 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6144 The release is out but you're still not finished.
6146 @subsubheading Commit outstanding changes
6148 In particular you'll need to commit any changes to:
6152 @file{gdb/ChangeLog}
6154 @file{gdb/version.in}
6161 @subsubheading Tag the release
6166 $ d=`date -u +%Y-%m-%d`
6169 $ ( cd insight/src/gdb && cvs -f -q update )
6170 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6173 Insight is used since that contains more of the release than
6174 @value{GDBN} (@code{dejagnu} doesn't get tagged but I think we can live
6177 @subsubheading Mention the release on the trunk
6179 Just put something in the @file{ChangeLog} so that the trunk also
6180 indicates when the release was made.
6182 @subsubheading Restart @file{gdb/version.in}
6184 If @file{gdb/version.in} does not contain an ISO date such as
6185 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6186 committed all the release changes it can be set to
6187 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6188 is important - it affects the snapshot process).
6190 Don't forget the @file{ChangeLog}.
6192 @subsubheading Merge into trunk
6194 The files committed to the branch may also need changes merged into the
6197 @subsubheading Revise the release schedule
6199 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
6200 Discussion List} with an updated announcement. The schedule can be
6201 generated by running:
6204 $ ~/ss/schedule `date +%s` schedule
6208 The first parameter is approximate date/time in seconds (from the epoch)
6209 of the most recent release.
6211 Also update the schedule @code{cronjob}.
6213 @section Post release
6215 Remove any @code{OBSOLETE} code.
6222 The testsuite is an important component of the @value{GDBN} package.
6223 While it is always worthwhile to encourage user testing, in practice
6224 this is rarely sufficient; users typically use only a small subset of
6225 the available commands, and it has proven all too common for a change
6226 to cause a significant regression that went unnoticed for some time.
6228 The @value{GDBN} testsuite uses the DejaGNU testing framework.
6229 DejaGNU is built using @code{Tcl} and @code{expect}. The tests
6230 themselves are calls to various @code{Tcl} procs; the framework runs all the
6231 procs and summarizes the passes and fails.
6233 @section Using the Testsuite
6235 @cindex running the test suite
6236 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
6237 testsuite's objdir) and type @code{make check}. This just sets up some
6238 environment variables and invokes DejaGNU's @code{runtest} script. While
6239 the testsuite is running, you'll get mentions of which test file is in use,
6240 and a mention of any unexpected passes or fails. When the testsuite is
6241 finished, you'll get a summary that looks like this:
6246 # of expected passes 6016
6247 # of unexpected failures 58
6248 # of unexpected successes 5
6249 # of expected failures 183
6250 # of unresolved testcases 3
6251 # of untested testcases 5
6254 The ideal test run consists of expected passes only; however, reality
6255 conspires to keep us from this ideal. Unexpected failures indicate
6256 real problems, whether in @value{GDBN} or in the testsuite. Expected
6257 failures are still failures, but ones which have been decided are too
6258 hard to deal with at the time; for instance, a test case might work
6259 everywhere except on AIX, and there is no prospect of the AIX case
6260 being fixed in the near future. Expected failures should not be added
6261 lightly, since you may be masking serious bugs in @value{GDBN}.
6262 Unexpected successes are expected fails that are passing for some
6263 reason, while unresolved and untested cases often indicate some minor
6264 catastrophe, such as the compiler being unable to deal with a test
6267 When making any significant change to @value{GDBN}, you should run the
6268 testsuite before and after the change, to confirm that there are no
6269 regressions. Note that truly complete testing would require that you
6270 run the testsuite with all supported configurations and a variety of
6271 compilers; however this is more than really necessary. In many cases
6272 testing with a single configuration is sufficient. Other useful
6273 options are to test one big-endian (Sparc) and one little-endian (x86)
6274 host, a cross config with a builtin simulator (powerpc-eabi,
6275 mips-elf), or a 64-bit host (Alpha).
6277 If you add new functionality to @value{GDBN}, please consider adding
6278 tests for it as well; this way future @value{GDBN} hackers can detect
6279 and fix their changes that break the functionality you added.
6280 Similarly, if you fix a bug that was not previously reported as a test
6281 failure, please add a test case for it. Some cases are extremely
6282 difficult to test, such as code that handles host OS failures or bugs
6283 in particular versions of compilers, and it's OK not to try to write
6284 tests for all of those.
6286 @section Testsuite Organization
6288 @cindex test suite organization
6289 The testsuite is entirely contained in @file{gdb/testsuite}. While the
6290 testsuite includes some makefiles and configury, these are very minimal,
6291 and used for little besides cleaning up, since the tests themselves
6292 handle the compilation of the programs that @value{GDBN} will run. The file
6293 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
6294 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
6295 configuration-specific files, typically used for special-purpose
6296 definitions of procs like @code{gdb_load} and @code{gdb_start}.
6298 The tests themselves are to be found in @file{testsuite/gdb.*} and
6299 subdirectories of those. The names of the test files must always end
6300 with @file{.exp}. DejaGNU collects the test files by wildcarding
6301 in the test directories, so both subdirectories and individual files
6302 get chosen and run in alphabetical order.
6304 The following table lists the main types of subdirectories and what they
6305 are for. Since DejaGNU finds test files no matter where they are
6306 located, and since each test file sets up its own compilation and
6307 execution environment, this organization is simply for convenience and
6312 This is the base testsuite. The tests in it should apply to all
6313 configurations of @value{GDBN} (but generic native-only tests may live here).
6314 The test programs should be in the subset of C that is valid K&R,
6315 ANSI/ISO, and C++ (@code{#ifdef}s are allowed if necessary, for instance
6318 @item gdb.@var{lang}
6319 Language-specific tests for any language @var{lang} besides C. Examples are
6320 @file{gdb.c++} and @file{gdb.java}.
6322 @item gdb.@var{platform}
6323 Non-portable tests. The tests are specific to a specific configuration
6324 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
6327 @item gdb.@var{compiler}
6328 Tests specific to a particular compiler. As of this writing (June
6329 1999), there aren't currently any groups of tests in this category that
6330 couldn't just as sensibly be made platform-specific, but one could
6331 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
6334 @item gdb.@var{subsystem}
6335 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
6336 instance, @file{gdb.disasm} exercises various disassemblers, while
6337 @file{gdb.stabs} tests pathways through the stabs symbol reader.
6340 @section Writing Tests
6341 @cindex writing tests
6343 In many areas, the @value{GDBN} tests are already quite comprehensive; you
6344 should be able to copy existing tests to handle new cases.
6346 You should try to use @code{gdb_test} whenever possible, since it
6347 includes cases to handle all the unexpected errors that might happen.
6348 However, it doesn't cost anything to add new test procedures; for
6349 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
6350 calls @code{gdb_test} multiple times.
6352 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
6353 necessary, such as when @value{GDBN} has several valid responses to a command.
6355 The source language programs do @emph{not} need to be in a consistent
6356 style. Since @value{GDBN} is used to debug programs written in many different
6357 styles, it's worth having a mix of styles in the testsuite; for
6358 instance, some @value{GDBN} bugs involving the display of source lines would
6359 never manifest themselves if the programs used GNU coding style
6366 Check the @file{README} file, it often has useful information that does not
6367 appear anywhere else in the directory.
6370 * Getting Started:: Getting started working on @value{GDBN}
6371 * Debugging GDB:: Debugging @value{GDBN} with itself
6374 @node Getting Started,,, Hints
6376 @section Getting Started
6378 @value{GDBN} is a large and complicated program, and if you first starting to
6379 work on it, it can be hard to know where to start. Fortunately, if you
6380 know how to go about it, there are ways to figure out what is going on.
6382 This manual, the @value{GDBN} Internals manual, has information which applies
6383 generally to many parts of @value{GDBN}.
6385 Information about particular functions or data structures are located in
6386 comments with those functions or data structures. If you run across a
6387 function or a global variable which does not have a comment correctly
6388 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
6389 free to submit a bug report, with a suggested comment if you can figure
6390 out what the comment should say. If you find a comment which is
6391 actually wrong, be especially sure to report that.
6393 Comments explaining the function of macros defined in host, target, or
6394 native dependent files can be in several places. Sometimes they are
6395 repeated every place the macro is defined. Sometimes they are where the
6396 macro is used. Sometimes there is a header file which supplies a
6397 default definition of the macro, and the comment is there. This manual
6398 also documents all the available macros.
6399 @c (@pxref{Host Conditionals}, @pxref{Target
6400 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
6403 Start with the header files. Once you have some idea of how
6404 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
6405 @file{gdbtypes.h}), you will find it much easier to understand the
6406 code which uses and creates those symbol tables.
6408 You may wish to process the information you are getting somehow, to
6409 enhance your understanding of it. Summarize it, translate it to another
6410 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
6411 the code to predict what a test case would do and write the test case
6412 and verify your prediction, etc. If you are reading code and your eyes
6413 are starting to glaze over, this is a sign you need to use a more active
6416 Once you have a part of @value{GDBN} to start with, you can find more
6417 specifically the part you are looking for by stepping through each
6418 function with the @code{next} command. Do not use @code{step} or you
6419 will quickly get distracted; when the function you are stepping through
6420 calls another function try only to get a big-picture understanding
6421 (perhaps using the comment at the beginning of the function being
6422 called) of what it does. This way you can identify which of the
6423 functions being called by the function you are stepping through is the
6424 one which you are interested in. You may need to examine the data
6425 structures generated at each stage, with reference to the comments in
6426 the header files explaining what the data structures are supposed to
6429 Of course, this same technique can be used if you are just reading the
6430 code, rather than actually stepping through it. The same general
6431 principle applies---when the code you are looking at calls something
6432 else, just try to understand generally what the code being called does,
6433 rather than worrying about all its details.
6435 @cindex command implementation
6436 A good place to start when tracking down some particular area is with
6437 a command which invokes that feature. Suppose you want to know how
6438 single-stepping works. As a @value{GDBN} user, you know that the
6439 @code{step} command invokes single-stepping. The command is invoked
6440 via command tables (see @file{command.h}); by convention the function
6441 which actually performs the command is formed by taking the name of
6442 the command and adding @samp{_command}, or in the case of an
6443 @code{info} subcommand, @samp{_info}. For example, the @code{step}
6444 command invokes the @code{step_command} function and the @code{info
6445 display} command invokes @code{display_info}. When this convention is
6446 not followed, you might have to use @code{grep} or @kbd{M-x
6447 tags-search} in emacs, or run @value{GDBN} on itself and set a
6448 breakpoint in @code{execute_command}.
6450 @cindex @code{bug-gdb} mailing list
6451 If all of the above fail, it may be appropriate to ask for information
6452 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
6453 wondering if anyone could give me some tips about understanding
6454 @value{GDBN}''---if we had some magic secret we would put it in this manual.
6455 Suggestions for improving the manual are always welcome, of course.
6457 @node Debugging GDB,,,Hints
6459 @section Debugging @value{GDBN} with itself
6460 @cindex debugging @value{GDBN}
6462 If @value{GDBN} is limping on your machine, this is the preferred way to get it
6463 fully functional. Be warned that in some ancient Unix systems, like
6464 Ultrix 4.2, a program can't be running in one process while it is being
6465 debugged in another. Rather than typing the command @kbd{@w{./gdb
6466 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
6467 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
6469 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
6470 @file{.gdbinit} file that sets up some simple things to make debugging
6471 gdb easier. The @code{info} command, when executed without a subcommand
6472 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
6473 gdb. See @file{.gdbinit} for details.
6475 If you use emacs, you will probably want to do a @code{make TAGS} after
6476 you configure your distribution; this will put the machine dependent
6477 routines for your local machine where they will be accessed first by
6480 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
6481 have run @code{fixincludes} if you are compiling with gcc.
6483 @section Submitting Patches
6485 @cindex submitting patches
6486 Thanks for thinking of offering your changes back to the community of
6487 @value{GDBN} users. In general we like to get well designed enhancements.
6488 Thanks also for checking in advance about the best way to transfer the
6491 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
6492 This manual summarizes what we believe to be clean design for @value{GDBN}.
6494 If the maintainers don't have time to put the patch in when it arrives,
6495 or if there is any question about a patch, it goes into a large queue
6496 with everyone else's patches and bug reports.
6498 @cindex legal papers for code contributions
6499 The legal issue is that to incorporate substantial changes requires a
6500 copyright assignment from you and/or your employer, granting ownership
6501 of the changes to the Free Software Foundation. You can get the
6502 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
6503 and asking for it. We recommend that people write in "All programs
6504 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
6505 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
6507 contributed with only one piece of legalese pushed through the
6508 bureaucracy and filed with the FSF. We can't start merging changes until
6509 this paperwork is received by the FSF (their rules, which we follow
6510 since we maintain it for them).
6512 Technically, the easiest way to receive changes is to receive each
6513 feature as a small context diff or unidiff, suitable for @code{patch}.
6514 Each message sent to me should include the changes to C code and
6515 header files for a single feature, plus @file{ChangeLog} entries for
6516 each directory where files were modified, and diffs for any changes
6517 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
6518 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
6519 single feature, they can be split down into multiple messages.
6521 In this way, if we read and like the feature, we can add it to the
6522 sources with a single patch command, do some testing, and check it in.
6523 If you leave out the @file{ChangeLog}, we have to write one. If you leave
6524 out the doc, we have to puzzle out what needs documenting. Etc., etc.
6526 The reason to send each change in a separate message is that we will not
6527 install some of the changes. They'll be returned to you with questions
6528 or comments. If we're doing our job correctly, the message back to you
6529 will say what you have to fix in order to make the change acceptable.
6530 The reason to have separate messages for separate features is so that
6531 the acceptable changes can be installed while one or more changes are
6532 being reworked. If multiple features are sent in a single message, we
6533 tend to not put in the effort to sort out the acceptable changes from
6534 the unacceptable, so none of the features get installed until all are
6537 If this sounds painful or authoritarian, well, it is. But we get a lot
6538 of bug reports and a lot of patches, and many of them don't get
6539 installed because we don't have the time to finish the job that the bug
6540 reporter or the contributor could have done. Patches that arrive
6541 complete, working, and well designed, tend to get installed on the day
6542 they arrive. The others go into a queue and get installed as time
6543 permits, which, since the maintainers have many demands to meet, may not
6544 be for quite some time.
6546 Please send patches directly to
6547 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
6549 @section Obsolete Conditionals
6550 @cindex obsolete code
6552 Fragments of old code in @value{GDBN} sometimes reference or set the following
6553 configuration macros. They should not be used by new code, and old uses
6554 should be removed as those parts of the debugger are otherwise touched.
6557 @item STACK_END_ADDR
6558 This macro used to define where the end of the stack appeared, for use
6559 in interpreting core file formats that don't record this address in the
6560 core file itself. This information is now configured in BFD, and @value{GDBN}
6561 gets the info portably from there. The values in @value{GDBN}'s configuration
6562 files should be moved into BFD configuration files (if needed there),
6563 and deleted from all of @value{GDBN}'s config files.
6565 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
6566 is so old that it has never been converted to use BFD. Now that's old!