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 * GDB Observers:: @value{GDBN} Currently available observers
98 * GNU Free Documentation License:: The license for this documentation
104 @chapter Requirements
105 @cindex requirements for @value{GDBN}
107 Before diving into the internals, you should understand the formal
108 requirements and other expectations for @value{GDBN}. Although some
109 of these may seem obvious, there have been proposals for @value{GDBN}
110 that have run counter to these requirements.
112 First of all, @value{GDBN} is a debugger. It's not designed to be a
113 front panel for embedded systems. It's not a text editor. It's not a
114 shell. It's not a programming environment.
116 @value{GDBN} is an interactive tool. Although a batch mode is
117 available, @value{GDBN}'s primary role is to interact with a human
120 @value{GDBN} should be responsive to the user. A programmer hot on
121 the trail of a nasty bug, and operating under a looming deadline, is
122 going to be very impatient of everything, including the response time
123 to debugger commands.
125 @value{GDBN} should be relatively permissive, such as for expressions.
126 While the compiler should be picky (or have the option to be made
127 picky), since source code lives for a long time usually, the
128 programmer doing debugging shouldn't be spending time figuring out to
129 mollify the debugger.
131 @value{GDBN} will be called upon to deal with really large programs.
132 Executable sizes of 50 to 100 megabytes occur regularly, and we've
133 heard reports of programs approaching 1 gigabyte in size.
135 @value{GDBN} should be able to run everywhere. No other debugger is
136 available for even half as many configurations as @value{GDBN}
140 @node Overall Structure
142 @chapter Overall Structure
144 @value{GDBN} consists of three major subsystems: user interface,
145 symbol handling (the @dfn{symbol side}), and target system handling (the
148 The user interface consists of several actual interfaces, plus
151 The symbol side consists of object file readers, debugging info
152 interpreters, symbol table management, source language expression
153 parsing, type and value printing.
155 The target side consists of execution control, stack frame analysis, and
156 physical target manipulation.
158 The target side/symbol side division is not formal, and there are a
159 number of exceptions. For instance, core file support involves symbolic
160 elements (the basic core file reader is in BFD) and target elements (it
161 supplies the contents of memory and the values of registers). Instead,
162 this division is useful for understanding how the minor subsystems
165 @section The Symbol Side
167 The symbolic side of @value{GDBN} can be thought of as ``everything
168 you can do in @value{GDBN} without having a live program running''.
169 For instance, you can look at the types of variables, and evaluate
170 many kinds of expressions.
172 @section The Target Side
174 The target side of @value{GDBN} is the ``bits and bytes manipulator''.
175 Although it may make reference to symbolic info here and there, most
176 of the target side will run with only a stripped executable
177 available---or even no executable at all, in remote debugging cases.
179 Operations such as disassembly, stack frame crawls, and register
180 display, are able to work with no symbolic info at all. In some cases,
181 such as disassembly, @value{GDBN} will use symbolic info to present addresses
182 relative to symbols rather than as raw numbers, but it will work either
185 @section Configurations
189 @dfn{Host} refers to attributes of the system where @value{GDBN} runs.
190 @dfn{Target} refers to the system where the program being debugged
191 executes. In most cases they are the same machine, in which case a
192 third type of @dfn{Native} attributes come into play.
194 Defines and include files needed to build on the host are host support.
195 Examples are tty support, system defined types, host byte order, host
198 Defines and information needed to handle the target format are target
199 dependent. Examples are the stack frame format, instruction set,
200 breakpoint instruction, registers, and how to set up and tear down the stack
203 Information that is only needed when the host and target are the same,
204 is native dependent. One example is Unix child process support; if the
205 host and target are not the same, doing a fork to start the target
206 process is a bad idea. The various macros needed for finding the
207 registers in the @code{upage}, running @code{ptrace}, and such are all
208 in the native-dependent files.
210 Another example of native-dependent code is support for features that
211 are really part of the target environment, but which require
212 @code{#include} files that are only available on the host system. Core
213 file handling and @code{setjmp} handling are two common cases.
215 When you want to make @value{GDBN} work ``native'' on a particular machine, you
216 have to include all three kinds of information.
224 @value{GDBN} uses a number of debugging-specific algorithms. They are
225 often not very complicated, but get lost in the thicket of special
226 cases and real-world issues. This chapter describes the basic
227 algorithms and mentions some of the specific target definitions that
233 @cindex call stack frame
234 A frame is a construct that @value{GDBN} uses to keep track of calling
235 and called functions.
237 @findex create_new_frame
239 @code{FRAME_FP} in the machine description has no meaning to the
240 machine-independent part of @value{GDBN}, except that it is used when
241 setting up a new frame from scratch, as follows:
244 create_new_frame (read_register (DEPRECATED_FP_REGNUM), read_pc ()));
247 @cindex frame pointer register
248 Other than that, all the meaning imparted to @code{DEPRECATED_FP_REGNUM}
249 is imparted by the machine-dependent code. So,
250 @code{DEPRECATED_FP_REGNUM} can have any value that is convenient for
251 the code that creates new frames. (@code{create_new_frame} calls
252 @code{DEPRECATED_INIT_EXTRA_FRAME_INFO} if it is defined; that is where
253 you should use the @code{DEPRECATED_FP_REGNUM} value, if your frames are
257 Given a @value{GDBN} frame, define @code{DEPRECATED_FRAME_CHAIN} to
258 determine the address of the calling function's frame. This will be
259 used to create a new @value{GDBN} frame struct, and then
260 @code{DEPRECATED_INIT_EXTRA_FRAME_INFO} and
261 @code{DEPRECATED_INIT_FRAME_PC} will be called for the new frame.
263 @section Breakpoint Handling
266 In general, a breakpoint is a user-designated location in the program
267 where the user wants to regain control if program execution ever reaches
270 There are two main ways to implement breakpoints; either as ``hardware''
271 breakpoints or as ``software'' breakpoints.
273 @cindex hardware breakpoints
274 @cindex program counter
275 Hardware breakpoints are sometimes available as a builtin debugging
276 features with some chips. Typically these work by having dedicated
277 register into which the breakpoint address may be stored. If the PC
278 (shorthand for @dfn{program counter})
279 ever matches a value in a breakpoint registers, the CPU raises an
280 exception and reports it to @value{GDBN}.
282 Another possibility is when an emulator is in use; many emulators
283 include circuitry that watches the address lines coming out from the
284 processor, and force it to stop if the address matches a breakpoint's
287 A third possibility is that the target already has the ability to do
288 breakpoints somehow; for instance, a ROM monitor may do its own
289 software breakpoints. So although these are not literally ``hardware
290 breakpoints'', from @value{GDBN}'s point of view they work the same;
291 @value{GDBN} need not do nothing more than set the breakpoint and wait
292 for something to happen.
294 Since they depend on hardware resources, hardware breakpoints may be
295 limited in number; when the user asks for more, @value{GDBN} will
296 start trying to set software breakpoints. (On some architectures,
297 notably the 32-bit x86 platforms, @value{GDBN} cannot always know
298 whether there's enough hardware resources to insert all the hardware
299 breakpoints and watchpoints. On those platforms, @value{GDBN} prints
300 an error message only when the program being debugged is continued.)
302 @cindex software breakpoints
303 Software breakpoints require @value{GDBN} to do somewhat more work.
304 The basic theory is that @value{GDBN} will replace a program
305 instruction with a trap, illegal divide, or some other instruction
306 that will cause an exception, and then when it's encountered,
307 @value{GDBN} will take the exception and stop the program. When the
308 user says to continue, @value{GDBN} will restore the original
309 instruction, single-step, re-insert the trap, and continue on.
311 Since it literally overwrites the program being tested, the program area
312 must be writable, so this technique won't work on programs in ROM. It
313 can also distort the behavior of programs that examine themselves,
314 although such a situation would be highly unusual.
316 Also, the software breakpoint instruction should be the smallest size of
317 instruction, so it doesn't overwrite an instruction that might be a jump
318 target, and cause disaster when the program jumps into the middle of the
319 breakpoint instruction. (Strictly speaking, the breakpoint must be no
320 larger than the smallest interval between instructions that may be jump
321 targets; perhaps there is an architecture where only even-numbered
322 instructions may jumped to.) Note that it's possible for an instruction
323 set not to have any instructions usable for a software breakpoint,
324 although in practice only the ARC has failed to define such an
328 The basic definition of the software breakpoint is the macro
331 Basic breakpoint object handling is in @file{breakpoint.c}. However,
332 much of the interesting breakpoint action is in @file{infrun.c}.
334 @section Single Stepping
336 @section Signal Handling
338 @section Thread Handling
340 @section Inferior Function Calls
342 @section Longjmp Support
344 @cindex @code{longjmp} debugging
345 @value{GDBN} has support for figuring out that the target is doing a
346 @code{longjmp} and for stopping at the target of the jump, if we are
347 stepping. This is done with a few specialized internal breakpoints,
348 which are visible in the output of the @samp{maint info breakpoint}
351 @findex GET_LONGJMP_TARGET
352 To make this work, you need to define a macro called
353 @code{GET_LONGJMP_TARGET}, which will examine the @code{jmp_buf}
354 structure and extract the longjmp target address. Since @code{jmp_buf}
355 is target specific, you will need to define it in the appropriate
356 @file{tm-@var{target}.h} file. Look in @file{tm-sun4os4.h} and
357 @file{sparc-tdep.c} for examples of how to do this.
362 Watchpoints are a special kind of breakpoints (@pxref{Algorithms,
363 breakpoints}) which break when data is accessed rather than when some
364 instruction is executed. When you have data which changes without
365 your knowing what code does that, watchpoints are the silver bullet to
366 hunt down and kill such bugs.
368 @cindex hardware watchpoints
369 @cindex software watchpoints
370 Watchpoints can be either hardware-assisted or not; the latter type is
371 known as ``software watchpoints.'' @value{GDBN} always uses
372 hardware-assisted watchpoints if they are available, and falls back on
373 software watchpoints otherwise. Typical situations where @value{GDBN}
374 will use software watchpoints are:
378 The watched memory region is too large for the underlying hardware
379 watchpoint support. For example, each x86 debug register can watch up
380 to 4 bytes of memory, so trying to watch data structures whose size is
381 more than 16 bytes will cause @value{GDBN} to use software
385 The value of the expression to be watched depends on data held in
386 registers (as opposed to memory).
389 Too many different watchpoints requested. (On some architectures,
390 this situation is impossible to detect until the debugged program is
391 resumed.) Note that x86 debug registers are used both for hardware
392 breakpoints and for watchpoints, so setting too many hardware
393 breakpoints might cause watchpoint insertion to fail.
396 No hardware-assisted watchpoints provided by the target
400 Software watchpoints are very slow, since @value{GDBN} needs to
401 single-step the program being debugged and test the value of the
402 watched expression(s) after each instruction. The rest of this
403 section is mostly irrelevant for software watchpoints.
405 @value{GDBN} uses several macros and primitives to support hardware
409 @findex TARGET_HAS_HARDWARE_WATCHPOINTS
410 @item TARGET_HAS_HARDWARE_WATCHPOINTS
411 If defined, the target supports hardware watchpoints.
413 @findex TARGET_CAN_USE_HARDWARE_WATCHPOINT
414 @item TARGET_CAN_USE_HARDWARE_WATCHPOINT (@var{type}, @var{count}, @var{other})
415 Return the number of hardware watchpoints of type @var{type} that are
416 possible to be set. The value is positive if @var{count} watchpoints
417 of this type can be set, zero if setting watchpoints of this type is
418 not supported, and negative if @var{count} is more than the maximum
419 number of watchpoints of type @var{type} that can be set. @var{other}
420 is non-zero if other types of watchpoints are currently enabled (there
421 are architectures which cannot set watchpoints of different types at
424 @findex TARGET_REGION_OK_FOR_HW_WATCHPOINT
425 @item TARGET_REGION_OK_FOR_HW_WATCHPOINT (@var{addr}, @var{len})
426 Return non-zero if hardware watchpoints can be used to watch a region
427 whose address is @var{addr} and whose length in bytes is @var{len}.
429 @findex TARGET_REGION_SIZE_OK_FOR_HW_WATCHPOINT
430 @item TARGET_REGION_SIZE_OK_FOR_HW_WATCHPOINT (@var{size})
431 Return non-zero if hardware watchpoints can be used to watch a region
432 whose size is @var{size}. @value{GDBN} only uses this macro as a
433 fall-back, in case @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is not
436 @findex TARGET_DISABLE_HW_WATCHPOINTS
437 @item TARGET_DISABLE_HW_WATCHPOINTS (@var{pid})
438 Disables watchpoints in the process identified by @var{pid}. This is
439 used, e.g., on HP-UX which provides operations to disable and enable
440 the page-level memory protection that implements hardware watchpoints
443 @findex TARGET_ENABLE_HW_WATCHPOINTS
444 @item TARGET_ENABLE_HW_WATCHPOINTS (@var{pid})
445 Enables watchpoints in the process identified by @var{pid}. This is
446 used, e.g., on HP-UX which provides operations to disable and enable
447 the page-level memory protection that implements hardware watchpoints
450 @findex target_insert_watchpoint
451 @findex target_remove_watchpoint
452 @item target_insert_watchpoint (@var{addr}, @var{len}, @var{type})
453 @itemx target_remove_watchpoint (@var{addr}, @var{len}, @var{type})
454 Insert or remove a hardware watchpoint starting at @var{addr}, for
455 @var{len} bytes. @var{type} is the watchpoint type, one of the
456 possible values of the enumerated data type @code{target_hw_bp_type},
457 defined by @file{breakpoint.h} as follows:
460 enum target_hw_bp_type
462 hw_write = 0, /* Common (write) HW watchpoint */
463 hw_read = 1, /* Read HW watchpoint */
464 hw_access = 2, /* Access (read or write) HW watchpoint */
465 hw_execute = 3 /* Execute HW breakpoint */
470 These two macros should return 0 for success, non-zero for failure.
472 @cindex insert or remove hardware breakpoint
473 @findex target_remove_hw_breakpoint
474 @findex target_insert_hw_breakpoint
475 @item target_remove_hw_breakpoint (@var{addr}, @var{shadow})
476 @itemx target_insert_hw_breakpoint (@var{addr}, @var{shadow})
477 Insert or remove a hardware-assisted breakpoint at address @var{addr}.
478 Returns zero for success, non-zero for failure. @var{shadow} is the
479 real contents of the byte where the breakpoint has been inserted; it
480 is generally not valid when hardware breakpoints are used, but since
481 no other code touches these values, the implementations of the above
482 two macros can use them for their internal purposes.
484 @findex target_stopped_data_address
485 @item target_stopped_data_address ()
486 If the inferior has some watchpoint that triggered, return the address
487 associated with that watchpoint. Otherwise, return zero.
489 @findex DECR_PC_AFTER_HW_BREAK
490 @item DECR_PC_AFTER_HW_BREAK
491 If defined, @value{GDBN} decrements the program counter by the value
492 of @code{DECR_PC_AFTER_HW_BREAK} after a hardware break-point. This
493 overrides the value of @code{DECR_PC_AFTER_BREAK} when a breakpoint
494 that breaks is a hardware-assisted breakpoint.
496 @findex HAVE_STEPPABLE_WATCHPOINT
497 @item HAVE_STEPPABLE_WATCHPOINT
498 If defined to a non-zero value, it is not necessary to disable a
499 watchpoint to step over it.
501 @findex HAVE_NONSTEPPABLE_WATCHPOINT
502 @item HAVE_NONSTEPPABLE_WATCHPOINT
503 If defined to a non-zero value, @value{GDBN} should disable a
504 watchpoint to step the inferior over it.
506 @findex HAVE_CONTINUABLE_WATCHPOINT
507 @item HAVE_CONTINUABLE_WATCHPOINT
508 If defined to a non-zero value, it is possible to continue the
509 inferior after a watchpoint has been hit.
511 @findex CANNOT_STEP_HW_WATCHPOINTS
512 @item CANNOT_STEP_HW_WATCHPOINTS
513 If this is defined to a non-zero value, @value{GDBN} will remove all
514 watchpoints before stepping the inferior.
516 @findex STOPPED_BY_WATCHPOINT
517 @item STOPPED_BY_WATCHPOINT (@var{wait_status})
518 Return non-zero if stopped by a watchpoint. @var{wait_status} is of
519 the type @code{struct target_waitstatus}, defined by @file{target.h}.
522 @subsection x86 Watchpoints
523 @cindex x86 debug registers
524 @cindex watchpoints, on x86
526 The 32-bit Intel x86 (a.k.a.@: ia32) processors feature special debug
527 registers designed to facilitate debugging. @value{GDBN} provides a
528 generic library of functions that x86-based ports can use to implement
529 support for watchpoints and hardware-assisted breakpoints. This
530 subsection documents the x86 watchpoint facilities in @value{GDBN}.
532 To use the generic x86 watchpoint support, a port should do the
536 @findex I386_USE_GENERIC_WATCHPOINTS
538 Define the macro @code{I386_USE_GENERIC_WATCHPOINTS} somewhere in the
539 target-dependent headers.
542 Include the @file{config/i386/nm-i386.h} header file @emph{after}
543 defining @code{I386_USE_GENERIC_WATCHPOINTS}.
546 Add @file{i386-nat.o} to the value of the Make variable
547 @code{NATDEPFILES} (@pxref{Native Debugging, NATDEPFILES}) or
548 @code{TDEPFILES} (@pxref{Target Architecture Definition, TDEPFILES}).
551 Provide implementations for the @code{I386_DR_LOW_*} macros described
552 below. Typically, each macro should call a target-specific function
553 which does the real work.
556 The x86 watchpoint support works by maintaining mirror images of the
557 debug registers. Values are copied between the mirror images and the
558 real debug registers via a set of macros which each target needs to
562 @findex I386_DR_LOW_SET_CONTROL
563 @item I386_DR_LOW_SET_CONTROL (@var{val})
564 Set the Debug Control (DR7) register to the value @var{val}.
566 @findex I386_DR_LOW_SET_ADDR
567 @item I386_DR_LOW_SET_ADDR (@var{idx}, @var{addr})
568 Put the address @var{addr} into the debug register number @var{idx}.
570 @findex I386_DR_LOW_RESET_ADDR
571 @item I386_DR_LOW_RESET_ADDR (@var{idx})
572 Reset (i.e.@: zero out) the address stored in the debug register
575 @findex I386_DR_LOW_GET_STATUS
576 @item I386_DR_LOW_GET_STATUS
577 Return the value of the Debug Status (DR6) register. This value is
578 used immediately after it is returned by
579 @code{I386_DR_LOW_GET_STATUS}, so as to support per-thread status
583 For each one of the 4 debug registers (whose indices are from 0 to 3)
584 that store addresses, a reference count is maintained by @value{GDBN},
585 to allow sharing of debug registers by several watchpoints. This
586 allows users to define several watchpoints that watch the same
587 expression, but with different conditions and/or commands, without
588 wasting debug registers which are in short supply. @value{GDBN}
589 maintains the reference counts internally, targets don't have to do
590 anything to use this feature.
592 The x86 debug registers can each watch a region that is 1, 2, or 4
593 bytes long. The ia32 architecture requires that each watched region
594 be appropriately aligned: 2-byte region on 2-byte boundary, 4-byte
595 region on 4-byte boundary. However, the x86 watchpoint support in
596 @value{GDBN} can watch unaligned regions and regions larger than 4
597 bytes (up to 16 bytes) by allocating several debug registers to watch
598 a single region. This allocation of several registers per a watched
599 region is also done automatically without target code intervention.
601 The generic x86 watchpoint support provides the following API for the
602 @value{GDBN}'s application code:
605 @findex i386_region_ok_for_watchpoint
606 @item i386_region_ok_for_watchpoint (@var{addr}, @var{len})
607 The macro @code{TARGET_REGION_OK_FOR_HW_WATCHPOINT} is set to call
608 this function. It counts the number of debug registers required to
609 watch a given region, and returns a non-zero value if that number is
610 less than 4, the number of debug registers available to x86
613 @findex i386_stopped_data_address
614 @item i386_stopped_data_address (void)
615 The macros @code{STOPPED_BY_WATCHPOINT} and
616 @code{target_stopped_data_address} are set to call this function. The
617 argument passed to @code{STOPPED_BY_WATCHPOINT} is ignored. This
618 function examines the breakpoint condition bits in the DR6 Debug
619 Status register, as returned by the @code{I386_DR_LOW_GET_STATUS}
620 macro, and returns the address associated with the first bit that is
623 @findex i386_insert_watchpoint
624 @findex i386_remove_watchpoint
625 @item i386_insert_watchpoint (@var{addr}, @var{len}, @var{type})
626 @itemx i386_remove_watchpoint (@var{addr}, @var{len}, @var{type})
627 Insert or remove a watchpoint. The macros
628 @code{target_insert_watchpoint} and @code{target_remove_watchpoint}
629 are set to call these functions. @code{i386_insert_watchpoint} first
630 looks for a debug register which is already set to watch the same
631 region for the same access types; if found, it just increments the
632 reference count of that debug register, thus implementing debug
633 register sharing between watchpoints. If no such register is found,
634 the function looks for a vacant debug register, sets its mirrored
635 value to @var{addr}, sets the mirrored value of DR7 Debug Control
636 register as appropriate for the @var{len} and @var{type} parameters,
637 and then passes the new values of the debug register and DR7 to the
638 inferior by calling @code{I386_DR_LOW_SET_ADDR} and
639 @code{I386_DR_LOW_SET_CONTROL}. If more than one debug register is
640 required to cover the given region, the above process is repeated for
643 @code{i386_remove_watchpoint} does the opposite: it resets the address
644 in the mirrored value of the debug register and its read/write and
645 length bits in the mirrored value of DR7, then passes these new
646 values to the inferior via @code{I386_DR_LOW_RESET_ADDR} and
647 @code{I386_DR_LOW_SET_CONTROL}. If a register is shared by several
648 watchpoints, each time a @code{i386_remove_watchpoint} is called, it
649 decrements the reference count, and only calls
650 @code{I386_DR_LOW_RESET_ADDR} and @code{I386_DR_LOW_SET_CONTROL} when
651 the count goes to zero.
653 @findex i386_insert_hw_breakpoint
654 @findex i386_remove_hw_breakpoint
655 @item i386_insert_hw_breakpoint (@var{addr}, @var{shadow}
656 @itemx i386_remove_hw_breakpoint (@var{addr}, @var{shadow})
657 These functions insert and remove hardware-assisted breakpoints. The
658 macros @code{target_insert_hw_breakpoint} and
659 @code{target_remove_hw_breakpoint} are set to call these functions.
660 These functions work like @code{i386_insert_watchpoint} and
661 @code{i386_remove_watchpoint}, respectively, except that they set up
662 the debug registers to watch instruction execution, and each
663 hardware-assisted breakpoint always requires exactly one debug
666 @findex i386_stopped_by_hwbp
667 @item i386_stopped_by_hwbp (void)
668 This function returns non-zero if the inferior has some watchpoint or
669 hardware breakpoint that triggered. It works like
670 @code{i386_stopped_data_address}, except that it doesn't return the
671 address whose watchpoint triggered.
673 @findex i386_cleanup_dregs
674 @item i386_cleanup_dregs (void)
675 This function clears all the reference counts, addresses, and control
676 bits in the mirror images of the debug registers. It doesn't affect
677 the actual debug registers in the inferior process.
684 x86 processors support setting watchpoints on I/O reads or writes.
685 However, since no target supports this (as of March 2001), and since
686 @code{enum target_hw_bp_type} doesn't even have an enumeration for I/O
687 watchpoints, this feature is not yet available to @value{GDBN} running
691 x86 processors can enable watchpoints locally, for the current task
692 only, or globally, for all the tasks. For each debug register,
693 there's a bit in the DR7 Debug Control register that determines
694 whether the associated address is watched locally or globally. The
695 current implementation of x86 watchpoint support in @value{GDBN}
696 always sets watchpoints to be locally enabled, since global
697 watchpoints might interfere with the underlying OS and are probably
698 unavailable in many platforms.
701 @section Observing changes in @value{GDBN} internals
702 @cindex observer pattern interface
703 @cindex notifications about changes in internals
705 In order to function properly, several modules need to be notified when
706 some changes occur in the @value{GDBN} internals. Traditionally, these
707 modules have relied on several paradigms, the most common ones being
708 hooks and gdb-events. Unfortunately, none of these paradigms was
709 versatile enough to become the standard notification mechanism in
710 @value{GDBN}. The fact that they only supported one ``client'' was also
713 A new paradigm, based on the Observer pattern of the @cite{Design
714 Patterns} book, has therefore been implemented. The goal was to provide
715 a new interface overcoming the issues with the notification mechanisms
716 previously available. This new interface needed to be strongly typed,
717 easy to extend, and versatile enough to be used as the standard
718 interface when adding new notifications.
720 See @ref{GDB Observers} for a brief description of the observers
721 currently implemented in GDB. The rationale for the current
722 implementation is also briefly discussed.
726 @chapter User Interface
728 @value{GDBN} has several user interfaces. Although the command-line interface
729 is the most common and most familiar, there are others.
731 @section Command Interpreter
733 @cindex command interpreter
735 The command interpreter in @value{GDBN} is fairly simple. It is designed to
736 allow for the set of commands to be augmented dynamically, and also
737 has a recursive subcommand capability, where the first argument to
738 a command may itself direct a lookup on a different command list.
740 For instance, the @samp{set} command just starts a lookup on the
741 @code{setlist} command list, while @samp{set thread} recurses
742 to the @code{set_thread_cmd_list}.
746 To add commands in general, use @code{add_cmd}. @code{add_com} adds to
747 the main command list, and should be used for those commands. The usual
748 place to add commands is in the @code{_initialize_@var{xyz}} routines at
749 the ends of most source files.
751 @findex add_setshow_cmd
752 @findex add_setshow_cmd_full
753 To add paired @samp{set} and @samp{show} commands, use
754 @code{add_setshow_cmd} or @code{add_setshow_cmd_full}. The former is
755 a slightly simpler interface which is useful when you don't need to
756 further modify the new command structures, while the latter returns
757 the new command structures for manipulation.
759 @cindex deprecating commands
760 @findex deprecate_cmd
761 Before removing commands from the command set it is a good idea to
762 deprecate them for some time. Use @code{deprecate_cmd} on commands or
763 aliases to set the deprecated flag. @code{deprecate_cmd} takes a
764 @code{struct cmd_list_element} as it's first argument. You can use the
765 return value from @code{add_com} or @code{add_cmd} to deprecate the
766 command immediately after it is created.
768 The first time a command is used the user will be warned and offered a
769 replacement (if one exists). Note that the replacement string passed to
770 @code{deprecate_cmd} should be the full name of the command, i.e. the
771 entire string the user should type at the command line.
773 @section UI-Independent Output---the @code{ui_out} Functions
774 @c This section is based on the documentation written by Fernando
775 @c Nasser <fnasser@redhat.com>.
777 @cindex @code{ui_out} functions
778 The @code{ui_out} functions present an abstraction level for the
779 @value{GDBN} output code. They hide the specifics of different user
780 interfaces supported by @value{GDBN}, and thus free the programmer
781 from the need to write several versions of the same code, one each for
782 every UI, to produce output.
784 @subsection Overview and Terminology
786 In general, execution of each @value{GDBN} command produces some sort
787 of output, and can even generate an input request.
789 Output can be generated for the following purposes:
793 to display a @emph{result} of an operation;
796 to convey @emph{info} or produce side-effects of a requested
800 to provide a @emph{notification} of an asynchronous event (including
801 progress indication of a prolonged asynchronous operation);
804 to display @emph{error messages} (including warnings);
807 to show @emph{debug data};
810 to @emph{query} or prompt a user for input (a special case).
814 This section mainly concentrates on how to build result output,
815 although some of it also applies to other kinds of output.
817 Generation of output that displays the results of an operation
818 involves one or more of the following:
822 output of the actual data
825 formatting the output as appropriate for console output, to make it
826 easily readable by humans
829 machine oriented formatting--a more terse formatting to allow for easy
830 parsing by programs which read @value{GDBN}'s output
833 annotation, whose purpose is to help legacy GUIs to identify interesting
837 The @code{ui_out} routines take care of the first three aspects.
838 Annotations are provided by separate annotation routines. Note that use
839 of annotations for an interface between a GUI and @value{GDBN} is
842 Output can be in the form of a single item, which we call a @dfn{field};
843 a @dfn{list} consisting of identical fields; a @dfn{tuple} consisting of
844 non-identical fields; or a @dfn{table}, which is a tuple consisting of a
845 header and a body. In a BNF-like form:
848 @item <table> @expansion{}
849 @code{<header> <body>}
850 @item <header> @expansion{}
851 @code{@{ <column> @}}
852 @item <column> @expansion{}
853 @code{<width> <alignment> <title>}
854 @item <body> @expansion{}
859 @subsection General Conventions
861 Most @code{ui_out} routines are of type @code{void}, the exceptions are
862 @code{ui_out_stream_new} (which returns a pointer to the newly created
863 object) and the @code{make_cleanup} routines.
865 The first parameter is always the @code{ui_out} vector object, a pointer
866 to a @code{struct ui_out}.
868 The @var{format} parameter is like in @code{printf} family of functions.
869 When it is present, there must also be a variable list of arguments
870 sufficient used to satisfy the @code{%} specifiers in the supplied
873 When a character string argument is not used in a @code{ui_out} function
874 call, a @code{NULL} pointer has to be supplied instead.
877 @subsection Table, Tuple and List Functions
879 @cindex list output functions
880 @cindex table output functions
881 @cindex tuple output functions
882 This section introduces @code{ui_out} routines for building lists,
883 tuples and tables. The routines to output the actual data items
884 (fields) are presented in the next section.
886 To recap: A @dfn{tuple} is a sequence of @dfn{fields}, each field
887 containing information about an object; a @dfn{list} is a sequence of
888 fields where each field describes an identical object.
890 Use the @dfn{table} functions when your output consists of a list of
891 rows (tuples) and the console output should include a heading. Use this
892 even when you are listing just one object but you still want the header.
894 @cindex nesting level in @code{ui_out} functions
895 Tables can not be nested. Tuples and lists can be nested up to a
896 maximum of five levels.
898 The overall structure of the table output code is something like this:
913 Here is the description of table-, tuple- and list-related @code{ui_out}
916 @deftypefun void ui_out_table_begin (struct ui_out *@var{uiout}, int @var{nbrofcols}, int @var{nr_rows}, const char *@var{tblid})
917 The function @code{ui_out_table_begin} marks the beginning of the output
918 of a table. It should always be called before any other @code{ui_out}
919 function for a given table. @var{nbrofcols} is the number of columns in
920 the table. @var{nr_rows} is the number of rows in the table.
921 @var{tblid} is an optional string identifying the table. The string
922 pointed to by @var{tblid} is copied by the implementation of
923 @code{ui_out_table_begin}, so the application can free the string if it
926 The companion function @code{ui_out_table_end}, described below, marks
927 the end of the table's output.
930 @deftypefun void ui_out_table_header (struct ui_out *@var{uiout}, int @var{width}, enum ui_align @var{alignment}, const char *@var{colhdr})
931 @code{ui_out_table_header} provides the header information for a single
932 table column. You call this function several times, one each for every
933 column of the table, after @code{ui_out_table_begin}, but before
934 @code{ui_out_table_body}.
936 The value of @var{width} gives the column width in characters. The
937 value of @var{alignment} is one of @code{left}, @code{center}, and
938 @code{right}, and it specifies how to align the header: left-justify,
939 center, or right-justify it. @var{colhdr} points to a string that
940 specifies the column header; the implementation copies that string, so
941 column header strings in @code{malloc}ed storage can be freed after the
945 @deftypefun void ui_out_table_body (struct ui_out *@var{uiout})
946 This function delimits the table header from the table body.
949 @deftypefun void ui_out_table_end (struct ui_out *@var{uiout})
950 This function signals the end of a table's output. It should be called
951 after the table body has been produced by the list and field output
954 There should be exactly one call to @code{ui_out_table_end} for each
955 call to @code{ui_out_table_begin}, otherwise the @code{ui_out} functions
956 will signal an internal error.
959 The output of the tuples that represent the table rows must follow the
960 call to @code{ui_out_table_body} and precede the call to
961 @code{ui_out_table_end}. You build a tuple by calling
962 @code{ui_out_tuple_begin} and @code{ui_out_tuple_end}, with suitable
963 calls to functions which actually output fields between them.
965 @deftypefun void ui_out_tuple_begin (struct ui_out *@var{uiout}, const char *@var{id})
966 This function marks the beginning of a tuple output. @var{id} points
967 to an optional string that identifies the tuple; it is copied by the
968 implementation, and so strings in @code{malloc}ed storage can be freed
972 @deftypefun void ui_out_tuple_end (struct ui_out *@var{uiout})
973 This function signals an end of a tuple output. There should be exactly
974 one call to @code{ui_out_tuple_end} for each call to
975 @code{ui_out_tuple_begin}, otherwise an internal @value{GDBN} error will
979 @deftypefun struct cleanup *make_cleanup_ui_out_tuple_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
980 This function first opens the tuple and then establishes a cleanup
981 (@pxref{Coding, Cleanups}) to close the tuple. It provides a convenient
982 and correct implementation of the non-portable@footnote{The function
983 cast is not portable ISO C.} code sequence:
985 struct cleanup *old_cleanup;
986 ui_out_tuple_begin (uiout, "...");
987 old_cleanup = make_cleanup ((void(*)(void *)) ui_out_tuple_end,
992 @deftypefun void ui_out_list_begin (struct ui_out *@var{uiout}, const char *@var{id})
993 This function marks the beginning of a list output. @var{id} points to
994 an optional string that identifies the list; it is copied by the
995 implementation, and so strings in @code{malloc}ed storage can be freed
999 @deftypefun void ui_out_list_end (struct ui_out *@var{uiout})
1000 This function signals an end of a list output. There should be exactly
1001 one call to @code{ui_out_list_end} for each call to
1002 @code{ui_out_list_begin}, otherwise an internal @value{GDBN} error will
1006 @deftypefun struct cleanup *make_cleanup_ui_out_list_begin_end (struct ui_out *@var{uiout}, const char *@var{id})
1007 Similar to @code{make_cleanup_ui_out_tuple_begin_end}, this function
1008 opens a list and then establishes cleanup (@pxref{Coding, Cleanups})
1009 that will close the list.list.
1012 @subsection Item Output Functions
1014 @cindex item output functions
1015 @cindex field output functions
1017 The functions described below produce output for the actual data
1018 items, or fields, which contain information about the object.
1020 Choose the appropriate function accordingly to your particular needs.
1022 @deftypefun void ui_out_field_fmt (struct ui_out *@var{uiout}, char *@var{fldname}, char *@var{format}, ...)
1023 This is the most general output function. It produces the
1024 representation of the data in the variable-length argument list
1025 according to formatting specifications in @var{format}, a
1026 @code{printf}-like format string. The optional argument @var{fldname}
1027 supplies the name of the field. The data items themselves are
1028 supplied as additional arguments after @var{format}.
1030 This generic function should be used only when it is not possible to
1031 use one of the specialized versions (see below).
1034 @deftypefun void ui_out_field_int (struct ui_out *@var{uiout}, const char *@var{fldname}, int @var{value})
1035 This function outputs a value of an @code{int} variable. It uses the
1036 @code{"%d"} output conversion specification. @var{fldname} specifies
1037 the name of the field.
1040 @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})
1041 This function outputs a value of an @code{int} variable. It differs from
1042 @code{ui_out_field_int} in that the caller specifies the desired @var{width} and @var{alignment} of the output.
1043 @var{fldname} specifies
1044 the name of the field.
1047 @deftypefun void ui_out_field_core_addr (struct ui_out *@var{uiout}, const char *@var{fldname}, CORE_ADDR @var{address})
1048 This function outputs an address.
1051 @deftypefun void ui_out_field_string (struct ui_out *@var{uiout}, const char *@var{fldname}, const char *@var{string})
1052 This function outputs a string using the @code{"%s"} conversion
1056 Sometimes, there's a need to compose your output piece by piece using
1057 functions that operate on a stream, such as @code{value_print} or
1058 @code{fprintf_symbol_filtered}. These functions accept an argument of
1059 the type @code{struct ui_file *}, a pointer to a @code{ui_file} object
1060 used to store the data stream used for the output. When you use one
1061 of these functions, you need a way to pass their results stored in a
1062 @code{ui_file} object to the @code{ui_out} functions. To this end,
1063 you first create a @code{ui_stream} object by calling
1064 @code{ui_out_stream_new}, pass the @code{stream} member of that
1065 @code{ui_stream} object to @code{value_print} and similar functions,
1066 and finally call @code{ui_out_field_stream} to output the field you
1067 constructed. When the @code{ui_stream} object is no longer needed,
1068 you should destroy it and free its memory by calling
1069 @code{ui_out_stream_delete}.
1071 @deftypefun struct ui_stream *ui_out_stream_new (struct ui_out *@var{uiout})
1072 This function creates a new @code{ui_stream} object which uses the
1073 same output methods as the @code{ui_out} object whose pointer is
1074 passed in @var{uiout}. It returns a pointer to the newly created
1075 @code{ui_stream} object.
1078 @deftypefun void ui_out_stream_delete (struct ui_stream *@var{streambuf})
1079 This functions destroys a @code{ui_stream} object specified by
1083 @deftypefun void ui_out_field_stream (struct ui_out *@var{uiout}, const char *@var{fieldname}, struct ui_stream *@var{streambuf})
1084 This function consumes all the data accumulated in
1085 @code{streambuf->stream} and outputs it like
1086 @code{ui_out_field_string} does. After a call to
1087 @code{ui_out_field_stream}, the accumulated data no longer exists, but
1088 the stream is still valid and may be used for producing more fields.
1091 @strong{Important:} If there is any chance that your code could bail
1092 out before completing output generation and reaching the point where
1093 @code{ui_out_stream_delete} is called, it is necessary to set up a
1094 cleanup, to avoid leaking memory and other resources. Here's a
1095 skeleton code to do that:
1098 struct ui_stream *mybuf = ui_out_stream_new (uiout);
1099 struct cleanup *old = make_cleanup (ui_out_stream_delete, mybuf);
1104 If the function already has the old cleanup chain set (for other kinds
1105 of cleanups), you just have to add your cleanup to it:
1108 mybuf = ui_out_stream_new (uiout);
1109 make_cleanup (ui_out_stream_delete, mybuf);
1112 Note that with cleanups in place, you should not call
1113 @code{ui_out_stream_delete} directly, or you would attempt to free the
1116 @subsection Utility Output Functions
1118 @deftypefun void ui_out_field_skip (struct ui_out *@var{uiout}, const char *@var{fldname})
1119 This function skips a field in a table. Use it if you have to leave
1120 an empty field without disrupting the table alignment. The argument
1121 @var{fldname} specifies a name for the (missing) filed.
1124 @deftypefun void ui_out_text (struct ui_out *@var{uiout}, const char *@var{string})
1125 This function outputs the text in @var{string} in a way that makes it
1126 easy to be read by humans. For example, the console implementation of
1127 this method filters the text through a built-in pager, to prevent it
1128 from scrolling off the visible portion of the screen.
1130 Use this function for printing relatively long chunks of text around
1131 the actual field data: the text it produces is not aligned according
1132 to the table's format. Use @code{ui_out_field_string} to output a
1133 string field, and use @code{ui_out_message}, described below, to
1134 output short messages.
1137 @deftypefun void ui_out_spaces (struct ui_out *@var{uiout}, int @var{nspaces})
1138 This function outputs @var{nspaces} spaces. It is handy to align the
1139 text produced by @code{ui_out_text} with the rest of the table or
1143 @deftypefun void ui_out_message (struct ui_out *@var{uiout}, int @var{verbosity}, const char *@var{format}, ...)
1144 This function produces a formatted message, provided that the current
1145 verbosity level is at least as large as given by @var{verbosity}. The
1146 current verbosity level is specified by the user with the @samp{set
1147 verbositylevel} command.@footnote{As of this writing (April 2001),
1148 setting verbosity level is not yet implemented, and is always returned
1149 as zero. So calling @code{ui_out_message} with a @var{verbosity}
1150 argument more than zero will cause the message to never be printed.}
1153 @deftypefun void ui_out_wrap_hint (struct ui_out *@var{uiout}, char *@var{indent})
1154 This function gives the console output filter (a paging filter) a hint
1155 of where to break lines which are too long. Ignored for all other
1156 output consumers. @var{indent}, if non-@code{NULL}, is the string to
1157 be printed to indent the wrapped text on the next line; it must remain
1158 accessible until the next call to @code{ui_out_wrap_hint}, or until an
1159 explicit newline is produced by one of the other functions. If
1160 @var{indent} is @code{NULL}, the wrapped text will not be indented.
1163 @deftypefun void ui_out_flush (struct ui_out *@var{uiout})
1164 This function flushes whatever output has been accumulated so far, if
1165 the UI buffers output.
1169 @subsection Examples of Use of @code{ui_out} functions
1171 @cindex using @code{ui_out} functions
1172 @cindex @code{ui_out} functions, usage examples
1173 This section gives some practical examples of using the @code{ui_out}
1174 functions to generalize the old console-oriented code in
1175 @value{GDBN}. The examples all come from functions defined on the
1176 @file{breakpoints.c} file.
1178 This example, from the @code{breakpoint_1} function, shows how to
1181 The original code was:
1184 if (!found_a_breakpoint++)
1186 annotate_breakpoints_headers ();
1189 printf_filtered ("Num ");
1191 printf_filtered ("Type ");
1193 printf_filtered ("Disp ");
1195 printf_filtered ("Enb ");
1199 printf_filtered ("Address ");
1202 printf_filtered ("What\n");
1204 annotate_breakpoints_table ();
1208 Here's the new version:
1211 nr_printable_breakpoints = @dots{};
1214 ui_out_table_begin (ui, 6, nr_printable_breakpoints, "BreakpointTable");
1216 ui_out_table_begin (ui, 5, nr_printable_breakpoints, "BreakpointTable");
1218 if (nr_printable_breakpoints > 0)
1219 annotate_breakpoints_headers ();
1220 if (nr_printable_breakpoints > 0)
1222 ui_out_table_header (uiout, 3, ui_left, "number", "Num"); /* 1 */
1223 if (nr_printable_breakpoints > 0)
1225 ui_out_table_header (uiout, 14, ui_left, "type", "Type"); /* 2 */
1226 if (nr_printable_breakpoints > 0)
1228 ui_out_table_header (uiout, 4, ui_left, "disp", "Disp"); /* 3 */
1229 if (nr_printable_breakpoints > 0)
1231 ui_out_table_header (uiout, 3, ui_left, "enabled", "Enb"); /* 4 */
1234 if (nr_printable_breakpoints > 0)
1236 if (TARGET_ADDR_BIT <= 32)
1237 ui_out_table_header (uiout, 10, ui_left, "addr", "Address");/* 5 */
1239 ui_out_table_header (uiout, 18, ui_left, "addr", "Address");/* 5 */
1241 if (nr_printable_breakpoints > 0)
1243 ui_out_table_header (uiout, 40, ui_noalign, "what", "What"); /* 6 */
1244 ui_out_table_body (uiout);
1245 if (nr_printable_breakpoints > 0)
1246 annotate_breakpoints_table ();
1249 This example, from the @code{print_one_breakpoint} function, shows how
1250 to produce the actual data for the table whose structure was defined
1251 in the above example. The original code was:
1256 printf_filtered ("%-3d ", b->number);
1258 if ((int)b->type > (sizeof(bptypes)/sizeof(bptypes[0]))
1259 || ((int) b->type != bptypes[(int) b->type].type))
1260 internal_error ("bptypes table does not describe type #%d.",
1262 printf_filtered ("%-14s ", bptypes[(int)b->type].description);
1264 printf_filtered ("%-4s ", bpdisps[(int)b->disposition]);
1266 printf_filtered ("%-3c ", bpenables[(int)b->enable]);
1270 This is the new version:
1274 ui_out_tuple_begin (uiout, "bkpt");
1276 ui_out_field_int (uiout, "number", b->number);
1278 if (((int) b->type > (sizeof (bptypes) / sizeof (bptypes[0])))
1279 || ((int) b->type != bptypes[(int) b->type].type))
1280 internal_error ("bptypes table does not describe type #%d.",
1282 ui_out_field_string (uiout, "type", bptypes[(int)b->type].description);
1284 ui_out_field_string (uiout, "disp", bpdisps[(int)b->disposition]);
1286 ui_out_field_fmt (uiout, "enabled", "%c", bpenables[(int)b->enable]);
1290 This example, also from @code{print_one_breakpoint}, shows how to
1291 produce a complicated output field using the @code{print_expression}
1292 functions which requires a stream to be passed. It also shows how to
1293 automate stream destruction with cleanups. The original code was:
1297 print_expression (b->exp, gdb_stdout);
1303 struct ui_stream *stb = ui_out_stream_new (uiout);
1304 struct cleanup *old_chain = make_cleanup_ui_out_stream_delete (stb);
1307 print_expression (b->exp, stb->stream);
1308 ui_out_field_stream (uiout, "what", local_stream);
1311 This example, also from @code{print_one_breakpoint}, shows how to use
1312 @code{ui_out_text} and @code{ui_out_field_string}. The original code
1317 if (b->dll_pathname == NULL)
1318 printf_filtered ("<any library> ");
1320 printf_filtered ("library \"%s\" ", b->dll_pathname);
1327 if (b->dll_pathname == NULL)
1329 ui_out_field_string (uiout, "what", "<any library>");
1330 ui_out_spaces (uiout, 1);
1334 ui_out_text (uiout, "library \"");
1335 ui_out_field_string (uiout, "what", b->dll_pathname);
1336 ui_out_text (uiout, "\" ");
1340 The following example from @code{print_one_breakpoint} shows how to
1341 use @code{ui_out_field_int} and @code{ui_out_spaces}. The original
1346 if (b->forked_inferior_pid != 0)
1347 printf_filtered ("process %d ", b->forked_inferior_pid);
1354 if (b->forked_inferior_pid != 0)
1356 ui_out_text (uiout, "process ");
1357 ui_out_field_int (uiout, "what", b->forked_inferior_pid);
1358 ui_out_spaces (uiout, 1);
1362 Here's an example of using @code{ui_out_field_string}. The original
1367 if (b->exec_pathname != NULL)
1368 printf_filtered ("program \"%s\" ", b->exec_pathname);
1375 if (b->exec_pathname != NULL)
1377 ui_out_text (uiout, "program \"");
1378 ui_out_field_string (uiout, "what", b->exec_pathname);
1379 ui_out_text (uiout, "\" ");
1383 Finally, here's an example of printing an address. The original code:
1387 printf_filtered ("%s ",
1388 local_hex_string_custom ((unsigned long) b->address, "08l"));
1395 ui_out_field_core_addr (uiout, "Address", b->address);
1399 @section Console Printing
1408 @cindex @code{libgdb}
1409 @code{libgdb} 1.0 was an abortive project of years ago. The theory was
1410 to provide an API to @value{GDBN}'s functionality.
1413 @cindex @code{libgdb}
1414 @code{libgdb} 2.0 is an ongoing effort to update @value{GDBN} so that is
1415 better able to support graphical and other environments.
1417 Since @code{libgdb} development is on-going, its architecture is still
1418 evolving. The following components have so far been identified:
1422 Observer - @file{gdb-events.h}.
1424 Builder - @file{ui-out.h}
1426 Event Loop - @file{event-loop.h}
1428 Library - @file{gdb.h}
1431 The model that ties these components together is described below.
1433 @section The @code{libgdb} Model
1435 A client of @code{libgdb} interacts with the library in two ways.
1439 As an observer (using @file{gdb-events}) receiving notifications from
1440 @code{libgdb} of any internal state changes (break point changes, run
1443 As a client querying @code{libgdb} (using the @file{ui-out} builder) to
1444 obtain various status values from @value{GDBN}.
1447 Since @code{libgdb} could have multiple clients (e.g. a GUI supporting
1448 the existing @value{GDBN} CLI), those clients must co-operate when
1449 controlling @code{libgdb}. In particular, a client must ensure that
1450 @code{libgdb} is idle (i.e. no other client is using @code{libgdb})
1451 before responding to a @file{gdb-event} by making a query.
1453 @section CLI support
1455 At present @value{GDBN}'s CLI is very much entangled in with the core of
1456 @code{libgdb}. Consequently, a client wishing to include the CLI in
1457 their interface needs to carefully co-ordinate its own and the CLI's
1460 It is suggested that the client set @code{libgdb} up to be bi-modal
1461 (alternate between CLI and client query modes). The notes below sketch
1466 The client registers itself as an observer of @code{libgdb}.
1468 The client create and install @code{cli-out} builder using its own
1469 versions of the @code{ui-file} @code{gdb_stderr}, @code{gdb_stdtarg} and
1470 @code{gdb_stdout} streams.
1472 The client creates a separate custom @code{ui-out} builder that is only
1473 used while making direct queries to @code{libgdb}.
1476 When the client receives input intended for the CLI, it simply passes it
1477 along. Since the @code{cli-out} builder is installed by default, all
1478 the CLI output in response to that command is routed (pronounced rooted)
1479 through to the client controlled @code{gdb_stdout} et.@: al.@: streams.
1480 At the same time, the client is kept abreast of internal changes by
1481 virtue of being a @code{libgdb} observer.
1483 The only restriction on the client is that it must wait until
1484 @code{libgdb} becomes idle before initiating any queries (using the
1485 client's custom builder).
1487 @section @code{libgdb} components
1489 @subheading Observer - @file{gdb-events.h}
1490 @file{gdb-events} provides the client with a very raw mechanism that can
1491 be used to implement an observer. At present it only allows for one
1492 observer and that observer must, internally, handle the need to delay
1493 the processing of any event notifications until after @code{libgdb} has
1494 finished the current command.
1496 @subheading Builder - @file{ui-out.h}
1497 @file{ui-out} provides the infrastructure necessary for a client to
1498 create a builder. That builder is then passed down to @code{libgdb}
1499 when doing any queries.
1501 @subheading Event Loop - @file{event-loop.h}
1502 @c There could be an entire section on the event-loop
1503 @file{event-loop}, currently non-re-entrant, provides a simple event
1504 loop. A client would need to either plug its self into this loop or,
1505 implement a new event-loop that GDB would use.
1507 The event-loop will eventually be made re-entrant. This is so that
1508 @value{GDB} can better handle the problem of some commands blocking
1509 instead of returning.
1511 @subheading Library - @file{gdb.h}
1512 @file{libgdb} is the most obvious component of this system. It provides
1513 the query interface. Each function is parameterized by a @code{ui-out}
1514 builder. The result of the query is constructed using that builder
1515 before the query function returns.
1517 @node Symbol Handling
1519 @chapter Symbol Handling
1521 Symbols are a key part of @value{GDBN}'s operation. Symbols include variables,
1522 functions, and types.
1524 @section Symbol Reading
1526 @cindex symbol reading
1527 @cindex reading of symbols
1528 @cindex symbol files
1529 @value{GDBN} reads symbols from @dfn{symbol files}. The usual symbol
1530 file is the file containing the program which @value{GDBN} is
1531 debugging. @value{GDBN} can be directed to use a different file for
1532 symbols (with the @samp{symbol-file} command), and it can also read
1533 more symbols via the @samp{add-file} and @samp{load} commands, or while
1534 reading symbols from shared libraries.
1536 @findex find_sym_fns
1537 Symbol files are initially opened by code in @file{symfile.c} using
1538 the BFD library (@pxref{Support Libraries}). BFD identifies the type
1539 of the file by examining its header. @code{find_sym_fns} then uses
1540 this identification to locate a set of symbol-reading functions.
1542 @findex add_symtab_fns
1543 @cindex @code{sym_fns} structure
1544 @cindex adding a symbol-reading module
1545 Symbol-reading modules identify themselves to @value{GDBN} by calling
1546 @code{add_symtab_fns} during their module initialization. The argument
1547 to @code{add_symtab_fns} is a @code{struct sym_fns} which contains the
1548 name (or name prefix) of the symbol format, the length of the prefix,
1549 and pointers to four functions. These functions are called at various
1550 times to process symbol files whose identification matches the specified
1553 The functions supplied by each module are:
1556 @item @var{xyz}_symfile_init(struct sym_fns *sf)
1558 @cindex secondary symbol file
1559 Called from @code{symbol_file_add} when we are about to read a new
1560 symbol file. This function should clean up any internal state (possibly
1561 resulting from half-read previous files, for example) and prepare to
1562 read a new symbol file. Note that the symbol file which we are reading
1563 might be a new ``main'' symbol file, or might be a secondary symbol file
1564 whose symbols are being added to the existing symbol table.
1566 The argument to @code{@var{xyz}_symfile_init} is a newly allocated
1567 @code{struct sym_fns} whose @code{bfd} field contains the BFD for the
1568 new symbol file being read. Its @code{private} field has been zeroed,
1569 and can be modified as desired. Typically, a struct of private
1570 information will be @code{malloc}'d, and a pointer to it will be placed
1571 in the @code{private} field.
1573 There is no result from @code{@var{xyz}_symfile_init}, but it can call
1574 @code{error} if it detects an unavoidable problem.
1576 @item @var{xyz}_new_init()
1578 Called from @code{symbol_file_add} when discarding existing symbols.
1579 This function needs only handle the symbol-reading module's internal
1580 state; the symbol table data structures visible to the rest of
1581 @value{GDBN} will be discarded by @code{symbol_file_add}. It has no
1582 arguments and no result. It may be called after
1583 @code{@var{xyz}_symfile_init}, if a new symbol table is being read, or
1584 may be called alone if all symbols are simply being discarded.
1586 @item @var{xyz}_symfile_read(struct sym_fns *sf, CORE_ADDR addr, int mainline)
1588 Called from @code{symbol_file_add} to actually read the symbols from a
1589 symbol-file into a set of psymtabs or symtabs.
1591 @code{sf} points to the @code{struct sym_fns} originally passed to
1592 @code{@var{xyz}_sym_init} for possible initialization. @code{addr} is
1593 the offset between the file's specified start address and its true
1594 address in memory. @code{mainline} is 1 if this is the main symbol
1595 table being read, and 0 if a secondary symbol file (e.g. shared library
1596 or dynamically loaded file) is being read.@refill
1599 In addition, if a symbol-reading module creates psymtabs when
1600 @var{xyz}_symfile_read is called, these psymtabs will contain a pointer
1601 to a function @code{@var{xyz}_psymtab_to_symtab}, which can be called
1602 from any point in the @value{GDBN} symbol-handling code.
1605 @item @var{xyz}_psymtab_to_symtab (struct partial_symtab *pst)
1607 Called from @code{psymtab_to_symtab} (or the @code{PSYMTAB_TO_SYMTAB} macro) if
1608 the psymtab has not already been read in and had its @code{pst->symtab}
1609 pointer set. The argument is the psymtab to be fleshed-out into a
1610 symtab. Upon return, @code{pst->readin} should have been set to 1, and
1611 @code{pst->symtab} should contain a pointer to the new corresponding symtab, or
1612 zero if there were no symbols in that part of the symbol file.
1615 @section Partial Symbol Tables
1617 @value{GDBN} has three types of symbol tables:
1620 @cindex full symbol table
1623 Full symbol tables (@dfn{symtabs}). These contain the main
1624 information about symbols and addresses.
1628 Partial symbol tables (@dfn{psymtabs}). These contain enough
1629 information to know when to read the corresponding part of the full
1632 @cindex minimal symbol table
1635 Minimal symbol tables (@dfn{msymtabs}). These contain information
1636 gleaned from non-debugging symbols.
1639 @cindex partial symbol table
1640 This section describes partial symbol tables.
1642 A psymtab is constructed by doing a very quick pass over an executable
1643 file's debugging information. Small amounts of information are
1644 extracted---enough to identify which parts of the symbol table will
1645 need to be re-read and fully digested later, when the user needs the
1646 information. The speed of this pass causes @value{GDBN} to start up very
1647 quickly. Later, as the detailed rereading occurs, it occurs in small
1648 pieces, at various times, and the delay therefrom is mostly invisible to
1650 @c (@xref{Symbol Reading}.)
1652 The symbols that show up in a file's psymtab should be, roughly, those
1653 visible to the debugger's user when the program is not running code from
1654 that file. These include external symbols and types, static symbols and
1655 types, and @code{enum} values declared at file scope.
1657 The psymtab also contains the range of instruction addresses that the
1658 full symbol table would represent.
1660 @cindex finding a symbol
1661 @cindex symbol lookup
1662 The idea is that there are only two ways for the user (or much of the
1663 code in the debugger) to reference a symbol:
1666 @findex find_pc_function
1667 @findex find_pc_line
1669 By its address (e.g. execution stops at some address which is inside a
1670 function in this file). The address will be noticed to be in the
1671 range of this psymtab, and the full symtab will be read in.
1672 @code{find_pc_function}, @code{find_pc_line}, and other
1673 @code{find_pc_@dots{}} functions handle this.
1675 @cindex lookup_symbol
1678 (e.g. the user asks to print a variable, or set a breakpoint on a
1679 function). Global names and file-scope names will be found in the
1680 psymtab, which will cause the symtab to be pulled in. Local names will
1681 have to be qualified by a global name, or a file-scope name, in which
1682 case we will have already read in the symtab as we evaluated the
1683 qualifier. Or, a local symbol can be referenced when we are ``in'' a
1684 local scope, in which case the first case applies. @code{lookup_symbol}
1685 does most of the work here.
1688 The only reason that psymtabs exist is to cause a symtab to be read in
1689 at the right moment. Any symbol that can be elided from a psymtab,
1690 while still causing that to happen, should not appear in it. Since
1691 psymtabs don't have the idea of scope, you can't put local symbols in
1692 them anyway. Psymtabs don't have the idea of the type of a symbol,
1693 either, so types need not appear, unless they will be referenced by
1696 It is a bug for @value{GDBN} to behave one way when only a psymtab has
1697 been read, and another way if the corresponding symtab has been read
1698 in. Such bugs are typically caused by a psymtab that does not contain
1699 all the visible symbols, or which has the wrong instruction address
1702 The psymtab for a particular section of a symbol file (objfile) could be
1703 thrown away after the symtab has been read in. The symtab should always
1704 be searched before the psymtab, so the psymtab will never be used (in a
1705 bug-free environment). Currently, psymtabs are allocated on an obstack,
1706 and all the psymbols themselves are allocated in a pair of large arrays
1707 on an obstack, so there is little to be gained by trying to free them
1708 unless you want to do a lot more work.
1712 @unnumberedsubsec Fundamental Types (e.g., @code{FT_VOID}, @code{FT_BOOLEAN}).
1714 @cindex fundamental types
1715 These are the fundamental types that @value{GDBN} uses internally. Fundamental
1716 types from the various debugging formats (stabs, ELF, etc) are mapped
1717 into one of these. They are basically a union of all fundamental types
1718 that @value{GDBN} knows about for all the languages that @value{GDBN}
1721 @unnumberedsubsec Type Codes (e.g., @code{TYPE_CODE_PTR}, @code{TYPE_CODE_ARRAY}).
1724 Each time @value{GDBN} builds an internal type, it marks it with one
1725 of these types. The type may be a fundamental type, such as
1726 @code{TYPE_CODE_INT}, or a derived type, such as @code{TYPE_CODE_PTR}
1727 which is a pointer to another type. Typically, several @code{FT_*}
1728 types map to one @code{TYPE_CODE_*} type, and are distinguished by
1729 other members of the type struct, such as whether the type is signed
1730 or unsigned, and how many bits it uses.
1732 @unnumberedsubsec Builtin Types (e.g., @code{builtin_type_void}, @code{builtin_type_char}).
1734 These are instances of type structs that roughly correspond to
1735 fundamental types and are created as global types for @value{GDBN} to
1736 use for various ugly historical reasons. We eventually want to
1737 eliminate these. Note for example that @code{builtin_type_int}
1738 initialized in @file{gdbtypes.c} is basically the same as a
1739 @code{TYPE_CODE_INT} type that is initialized in @file{c-lang.c} for
1740 an @code{FT_INTEGER} fundamental type. The difference is that the
1741 @code{builtin_type} is not associated with any particular objfile, and
1742 only one instance exists, while @file{c-lang.c} builds as many
1743 @code{TYPE_CODE_INT} types as needed, with each one associated with
1744 some particular objfile.
1746 @section Object File Formats
1747 @cindex object file formats
1751 @cindex @code{a.out} format
1752 The @code{a.out} format is the original file format for Unix. It
1753 consists of three sections: @code{text}, @code{data}, and @code{bss},
1754 which are for program code, initialized data, and uninitialized data,
1757 The @code{a.out} format is so simple that it doesn't have any reserved
1758 place for debugging information. (Hey, the original Unix hackers used
1759 @samp{adb}, which is a machine-language debugger!) The only debugging
1760 format for @code{a.out} is stabs, which is encoded as a set of normal
1761 symbols with distinctive attributes.
1763 The basic @code{a.out} reader is in @file{dbxread.c}.
1768 The COFF format was introduced with System V Release 3 (SVR3) Unix.
1769 COFF files may have multiple sections, each prefixed by a header. The
1770 number of sections is limited.
1772 The COFF specification includes support for debugging. Although this
1773 was a step forward, the debugging information was woefully limited. For
1774 instance, it was not possible to represent code that came from an
1777 The COFF reader is in @file{coffread.c}.
1781 @cindex ECOFF format
1782 ECOFF is an extended COFF originally introduced for Mips and Alpha
1785 The basic ECOFF reader is in @file{mipsread.c}.
1789 @cindex XCOFF format
1790 The IBM RS/6000 running AIX uses an object file format called XCOFF.
1791 The COFF sections, symbols, and line numbers are used, but debugging
1792 symbols are @code{dbx}-style stabs whose strings are located in the
1793 @code{.debug} section (rather than the string table). For more
1794 information, see @ref{Top,,,stabs,The Stabs Debugging Format}.
1796 The shared library scheme has a clean interface for figuring out what
1797 shared libraries are in use, but the catch is that everything which
1798 refers to addresses (symbol tables and breakpoints at least) needs to be
1799 relocated for both shared libraries and the main executable. At least
1800 using the standard mechanism this can only be done once the program has
1801 been run (or the core file has been read).
1805 @cindex PE-COFF format
1806 Windows 95 and NT use the PE (@dfn{Portable Executable}) format for their
1807 executables. PE is basically COFF with additional headers.
1809 While BFD includes special PE support, @value{GDBN} needs only the basic
1815 The ELF format came with System V Release 4 (SVR4) Unix. ELF is similar
1816 to COFF in being organized into a number of sections, but it removes
1817 many of COFF's limitations.
1819 The basic ELF reader is in @file{elfread.c}.
1824 SOM is HP's object file and debug format (not to be confused with IBM's
1825 SOM, which is a cross-language ABI).
1827 The SOM reader is in @file{hpread.c}.
1829 @subsection Other File Formats
1831 @cindex Netware Loadable Module format
1832 Other file formats that have been supported by @value{GDBN} include Netware
1833 Loadable Modules (@file{nlmread.c}).
1835 @section Debugging File Formats
1837 This section describes characteristics of debugging information that
1838 are independent of the object file format.
1842 @cindex stabs debugging info
1843 @code{stabs} started out as special symbols within the @code{a.out}
1844 format. Since then, it has been encapsulated into other file
1845 formats, such as COFF and ELF.
1847 While @file{dbxread.c} does some of the basic stab processing,
1848 including for encapsulated versions, @file{stabsread.c} does
1853 @cindex COFF debugging info
1854 The basic COFF definition includes debugging information. The level
1855 of support is minimal and non-extensible, and is not often used.
1857 @subsection Mips debug (Third Eye)
1859 @cindex ECOFF debugging info
1860 ECOFF includes a definition of a special debug format.
1862 The file @file{mdebugread.c} implements reading for this format.
1866 @cindex DWARF 1 debugging info
1867 DWARF 1 is a debugging format that was originally designed to be
1868 used with ELF in SVR4 systems.
1873 @c If defined, these are the producer strings in a DWARF 1 file. All of
1874 @c these have reasonable defaults already.
1876 The DWARF 1 reader is in @file{dwarfread.c}.
1880 @cindex DWARF 2 debugging info
1881 DWARF 2 is an improved but incompatible version of DWARF 1.
1883 The DWARF 2 reader is in @file{dwarf2read.c}.
1887 @cindex SOM debugging info
1888 Like COFF, the SOM definition includes debugging information.
1890 @section Adding a New Symbol Reader to @value{GDBN}
1892 @cindex adding debugging info reader
1893 If you are using an existing object file format (@code{a.out}, COFF, ELF, etc),
1894 there is probably little to be done.
1896 If you need to add a new object file format, you must first add it to
1897 BFD. This is beyond the scope of this document.
1899 You must then arrange for the BFD code to provide access to the
1900 debugging symbols. Generally @value{GDBN} will have to call swapping routines
1901 from BFD and a few other BFD internal routines to locate the debugging
1902 information. As much as possible, @value{GDBN} should not depend on the BFD
1903 internal data structures.
1905 For some targets (e.g., COFF), there is a special transfer vector used
1906 to call swapping routines, since the external data structures on various
1907 platforms have different sizes and layouts. Specialized routines that
1908 will only ever be implemented by one object file format may be called
1909 directly. This interface should be described in a file
1910 @file{bfd/lib@var{xyz}.h}, which is included by @value{GDBN}.
1913 @node Language Support
1915 @chapter Language Support
1917 @cindex language support
1918 @value{GDBN}'s language support is mainly driven by the symbol reader,
1919 although it is possible for the user to set the source language
1922 @value{GDBN} chooses the source language by looking at the extension
1923 of the file recorded in the debug info; @file{.c} means C, @file{.f}
1924 means Fortran, etc. It may also use a special-purpose language
1925 identifier if the debug format supports it, like with DWARF.
1927 @section Adding a Source Language to @value{GDBN}
1929 @cindex adding source language
1930 To add other languages to @value{GDBN}'s expression parser, follow the
1934 @item Create the expression parser.
1936 @cindex expression parser
1937 This should reside in a file @file{@var{lang}-exp.y}. Routines for
1938 building parsed expressions into a @code{union exp_element} list are in
1941 @cindex language parser
1942 Since we can't depend upon everyone having Bison, and YACC produces
1943 parsers that define a bunch of global names, the following lines
1944 @strong{must} be included at the top of the YACC parser, to prevent the
1945 various parsers from defining the same global names:
1948 #define yyparse @var{lang}_parse
1949 #define yylex @var{lang}_lex
1950 #define yyerror @var{lang}_error
1951 #define yylval @var{lang}_lval
1952 #define yychar @var{lang}_char
1953 #define yydebug @var{lang}_debug
1954 #define yypact @var{lang}_pact
1955 #define yyr1 @var{lang}_r1
1956 #define yyr2 @var{lang}_r2
1957 #define yydef @var{lang}_def
1958 #define yychk @var{lang}_chk
1959 #define yypgo @var{lang}_pgo
1960 #define yyact @var{lang}_act
1961 #define yyexca @var{lang}_exca
1962 #define yyerrflag @var{lang}_errflag
1963 #define yynerrs @var{lang}_nerrs
1966 At the bottom of your parser, define a @code{struct language_defn} and
1967 initialize it with the right values for your language. Define an
1968 @code{initialize_@var{lang}} routine and have it call
1969 @samp{add_language(@var{lang}_language_defn)} to tell the rest of @value{GDBN}
1970 that your language exists. You'll need some other supporting variables
1971 and functions, which will be used via pointers from your
1972 @code{@var{lang}_language_defn}. See the declaration of @code{struct
1973 language_defn} in @file{language.h}, and the other @file{*-exp.y} files,
1974 for more information.
1976 @item Add any evaluation routines, if necessary
1978 @cindex expression evaluation routines
1979 @findex evaluate_subexp
1980 @findex prefixify_subexp
1981 @findex length_of_subexp
1982 If you need new opcodes (that represent the operations of the language),
1983 add them to the enumerated type in @file{expression.h}. Add support
1984 code for these operations in the @code{evaluate_subexp} function
1985 defined in the file @file{eval.c}. Add cases
1986 for new opcodes in two functions from @file{parse.c}:
1987 @code{prefixify_subexp} and @code{length_of_subexp}. These compute
1988 the number of @code{exp_element}s that a given operation takes up.
1990 @item Update some existing code
1992 Add an enumerated identifier for your language to the enumerated type
1993 @code{enum language} in @file{defs.h}.
1995 Update the routines in @file{language.c} so your language is included.
1996 These routines include type predicates and such, which (in some cases)
1997 are language dependent. If your language does not appear in the switch
1998 statement, an error is reported.
2000 @vindex current_language
2001 Also included in @file{language.c} is the code that updates the variable
2002 @code{current_language}, and the routines that translate the
2003 @code{language_@var{lang}} enumerated identifier into a printable
2006 @findex _initialize_language
2007 Update the function @code{_initialize_language} to include your
2008 language. This function picks the default language upon startup, so is
2009 dependent upon which languages that @value{GDBN} is built for.
2011 @findex allocate_symtab
2012 Update @code{allocate_symtab} in @file{symfile.c} and/or symbol-reading
2013 code so that the language of each symtab (source file) is set properly.
2014 This is used to determine the language to use at each stack frame level.
2015 Currently, the language is set based upon the extension of the source
2016 file. If the language can be better inferred from the symbol
2017 information, please set the language of the symtab in the symbol-reading
2020 @findex print_subexp
2021 @findex op_print_tab
2022 Add helper code to @code{print_subexp} (in @file{expprint.c}) to handle any new
2023 expression opcodes you have added to @file{expression.h}. Also, add the
2024 printed representations of your operators to @code{op_print_tab}.
2026 @item Add a place of call
2029 Add a call to @code{@var{lang}_parse()} and @code{@var{lang}_error} in
2030 @code{parse_exp_1} (defined in @file{parse.c}).
2032 @item Use macros to trim code
2034 @cindex trimming language-dependent code
2035 The user has the option of building @value{GDBN} for some or all of the
2036 languages. If the user decides to build @value{GDBN} for the language
2037 @var{lang}, then every file dependent on @file{language.h} will have the
2038 macro @code{_LANG_@var{lang}} defined in it. Use @code{#ifdef}s to
2039 leave out large routines that the user won't need if he or she is not
2040 using your language.
2042 Note that you do not need to do this in your YACC parser, since if @value{GDBN}
2043 is not build for @var{lang}, then @file{@var{lang}-exp.tab.o} (the
2044 compiled form of your parser) is not linked into @value{GDBN} at all.
2046 See the file @file{configure.in} for how @value{GDBN} is configured
2047 for different languages.
2049 @item Edit @file{Makefile.in}
2051 Add dependencies in @file{Makefile.in}. Make sure you update the macro
2052 variables such as @code{HFILES} and @code{OBJS}, otherwise your code may
2053 not get linked in, or, worse yet, it may not get @code{tar}red into the
2058 @node Host Definition
2060 @chapter Host Definition
2062 With the advent of Autoconf, it's rarely necessary to have host
2063 definition machinery anymore. The following information is provided,
2064 mainly, as an historical reference.
2066 @section Adding a New Host
2068 @cindex adding a new host
2069 @cindex host, adding
2070 @value{GDBN}'s host configuration support normally happens via Autoconf.
2071 New host-specific definitions should not be needed. Older hosts
2072 @value{GDBN} still use the host-specific definitions and files listed
2073 below, but these mostly exist for historical reasons, and will
2074 eventually disappear.
2077 @item gdb/config/@var{arch}/@var{xyz}.mh
2078 This file once contained both host and native configuration information
2079 (@pxref{Native Debugging}) for the machine @var{xyz}. The host
2080 configuration information is now handed by Autoconf.
2082 Host configuration information included a definition of
2083 @code{XM_FILE=xm-@var{xyz}.h} and possibly definitions for @code{CC},
2084 @code{SYSV_DEFINE}, @code{XM_CFLAGS}, @code{XM_ADD_FILES},
2085 @code{XM_CLIBS}, @code{XM_CDEPS}, etc.; see @file{Makefile.in}.
2087 New host only configurations do not need this file.
2089 @item gdb/config/@var{arch}/xm-@var{xyz}.h
2090 This file once contained definitions and includes required when hosting
2091 gdb on machine @var{xyz}. Those definitions and includes are now
2092 handled by Autoconf.
2094 New host and native configurations do not need this file.
2096 @emph{Maintainer's note: Some hosts continue to use the @file{xm-xyz.h}
2097 file to define the macros @var{HOST_FLOAT_FORMAT},
2098 @var{HOST_DOUBLE_FORMAT} and @var{HOST_LONG_DOUBLE_FORMAT}. That code
2099 also needs to be replaced with either an Autoconf or run-time test.}
2103 @subheading Generic Host Support Files
2105 @cindex generic host support
2106 There are some ``generic'' versions of routines that can be used by
2107 various systems. These can be customized in various ways by macros
2108 defined in your @file{xm-@var{xyz}.h} file. If these routines work for
2109 the @var{xyz} host, you can just include the generic file's name (with
2110 @samp{.o}, not @samp{.c}) in @code{XDEPFILES}.
2112 Otherwise, if your machine needs custom support routines, you will need
2113 to write routines that perform the same functions as the generic file.
2114 Put them into @code{@var{xyz}-xdep.c}, and put @code{@var{xyz}-xdep.o}
2115 into @code{XDEPFILES}.
2118 @cindex remote debugging support
2119 @cindex serial line support
2121 This contains serial line support for Unix systems. This is always
2122 included, via the makefile variable @code{SER_HARDWIRE}; override this
2123 variable in the @file{.mh} file to avoid it.
2126 This contains serial line support for 32-bit programs running under DOS,
2127 using the DJGPP (a.k.a.@: GO32) execution environment.
2129 @cindex TCP remote support
2131 This contains generic TCP support using sockets.
2134 @section Host Conditionals
2136 When @value{GDBN} is configured and compiled, various macros are
2137 defined or left undefined, to control compilation based on the
2138 attributes of the host system. These macros and their meanings (or if
2139 the meaning is not documented here, then one of the source files where
2140 they are used is indicated) are:
2143 @item @value{GDBN}INIT_FILENAME
2144 The default name of @value{GDBN}'s initialization file (normally
2148 This macro is deprecated.
2151 Define this if your system does not have a @code{<sys/file.h>}.
2153 @item SIGWINCH_HANDLER
2154 If your host defines @code{SIGWINCH}, you can define this to be the name
2155 of a function to be called if @code{SIGWINCH} is received.
2157 @item SIGWINCH_HANDLER_BODY
2158 Define this to expand into code that will define the function named by
2159 the expansion of @code{SIGWINCH_HANDLER}.
2161 @item ALIGN_STACK_ON_STARTUP
2162 @cindex stack alignment
2163 Define this if your system is of a sort that will crash in
2164 @code{tgetent} if the stack happens not to be longword-aligned when
2165 @code{main} is called. This is a rare situation, but is known to occur
2166 on several different types of systems.
2168 @item CRLF_SOURCE_FILES
2169 @cindex DOS text files
2170 Define this if host files use @code{\r\n} rather than @code{\n} as a
2171 line terminator. This will cause source file listings to omit @code{\r}
2172 characters when printing and it will allow @code{\r\n} line endings of files
2173 which are ``sourced'' by gdb. It must be possible to open files in binary
2174 mode using @code{O_BINARY} or, for fopen, @code{"rb"}.
2176 @item DEFAULT_PROMPT
2178 The default value of the prompt string (normally @code{"(gdb) "}).
2181 @cindex terminal device
2182 The name of the generic TTY device, defaults to @code{"/dev/tty"}.
2184 @item FCLOSE_PROVIDED
2185 Define this if the system declares @code{fclose} in the headers included
2186 in @code{defs.h}. This isn't needed unless your compiler is unusually
2190 Define this if binary files are opened the same way as text files.
2192 @item GETENV_PROVIDED
2193 Define this if the system declares @code{getenv} in its headers included
2194 in @code{defs.h}. This isn't needed unless your compiler is unusually
2199 In some cases, use the system call @code{mmap} for reading symbol
2200 tables. For some machines this allows for sharing and quick updates.
2203 Define this if the host system has @code{termio.h}.
2210 Values for host-side constants.
2213 Substitute for isatty, if not available.
2216 This is the longest integer type available on the host. If not defined,
2217 it will default to @code{long long} or @code{long}, depending on
2218 @code{CC_HAS_LONG_LONG}.
2220 @item CC_HAS_LONG_LONG
2221 @cindex @code{long long} data type
2222 Define this if the host C compiler supports @code{long long}. This is set
2223 by the @code{configure} script.
2225 @item PRINTF_HAS_LONG_LONG
2226 Define this if the host can handle printing of long long integers via
2227 the printf format conversion specifier @code{ll}. This is set by the
2228 @code{configure} script.
2230 @item HAVE_LONG_DOUBLE
2231 Define this if the host C compiler supports @code{long double}. This is
2232 set by the @code{configure} script.
2234 @item PRINTF_HAS_LONG_DOUBLE
2235 Define this if the host can handle printing of long double float-point
2236 numbers via the printf format conversion specifier @code{Lg}. This is
2237 set by the @code{configure} script.
2239 @item SCANF_HAS_LONG_DOUBLE
2240 Define this if the host can handle the parsing of long double
2241 float-point numbers via the scanf format conversion specifier
2242 @code{Lg}. This is set by the @code{configure} script.
2244 @item LSEEK_NOT_LINEAR
2245 Define this if @code{lseek (n)} does not necessarily move to byte number
2246 @code{n} in the file. This is only used when reading source files. It
2247 is normally faster to define @code{CRLF_SOURCE_FILES} when possible.
2250 This macro is used as the argument to @code{lseek} (or, most commonly,
2251 @code{bfd_seek}). FIXME, should be replaced by SEEK_SET instead,
2252 which is the POSIX equivalent.
2254 @item MMAP_BASE_ADDRESS
2255 When using HAVE_MMAP, the first mapping should go at this address.
2257 @item MMAP_INCREMENT
2258 when using HAVE_MMAP, this is the increment between mappings.
2261 If defined, this should be one or more tokens, such as @code{volatile},
2262 that can be used in both the declaration and definition of functions to
2263 indicate that they never return. The default is already set correctly
2264 if compiling with GCC. This will almost never need to be defined.
2267 If defined, this should be one or more tokens, such as
2268 @code{__attribute__ ((noreturn))}, that can be used in the declarations
2269 of functions to indicate that they never return. The default is already
2270 set correctly if compiling with GCC. This will almost never need to be
2275 @value{GDBN} will use the @code{mmalloc} library for memory allocation
2276 for symbol reading if this symbol is defined. Be careful defining it
2277 since there are systems on which @code{mmalloc} does not work for some
2278 reason. One example is the DECstation, where its RPC library can't
2279 cope with our redefinition of @code{malloc} to call @code{mmalloc}.
2280 When defining @code{USE_MMALLOC}, you will also have to set
2281 @code{MMALLOC} in the Makefile, to point to the @code{mmalloc} library. This
2282 define is set when you configure with @samp{--with-mmalloc}.
2286 Define this if you are using @code{mmalloc}, but don't want the overhead
2287 of checking the heap with @code{mmcheck}. Note that on some systems,
2288 the C runtime makes calls to @code{malloc} prior to calling @code{main}, and if
2289 @code{free} is ever called with these pointers after calling
2290 @code{mmcheck} to enable checking, a memory corruption abort is certain
2291 to occur. These systems can still use @code{mmalloc}, but must define
2295 Define this to 1 if the C runtime allocates memory prior to
2296 @code{mmcheck} being called, but that memory is never freed so we don't
2297 have to worry about it triggering a memory corruption abort. The
2298 default is 0, which means that @code{mmcheck} will only install the heap
2299 checking functions if there has not yet been any memory allocation
2300 calls, and if it fails to install the functions, @value{GDBN} will issue a
2301 warning. This is currently defined if you configure using
2302 @samp{--with-mmalloc}.
2304 @item NO_SIGINTERRUPT
2305 @findex siginterrupt
2306 Define this to indicate that @code{siginterrupt} is not available.
2310 Define these to appropriate value for the system @code{lseek}, if not already
2314 This is the signal for stopping @value{GDBN}. Defaults to
2315 @code{SIGTSTP}. (Only redefined for the Convex.)
2318 Define this if the interior's tty should be opened with the @code{O_NOCTTY}
2319 flag. (FIXME: This should be a native-only flag, but @file{inflow.c} is
2323 Means that System V (prior to SVR4) include files are in use. (FIXME:
2324 This symbol is abused in @file{infrun.c}, @file{regex.c}, and
2325 @file{utils.c} for other things, at the moment.)
2328 Define this to help placate @code{lint} in some situations.
2331 Define this to override the defaults of @code{__volatile__} or
2336 @node Target Architecture Definition
2338 @chapter Target Architecture Definition
2340 @cindex target architecture definition
2341 @value{GDBN}'s target architecture defines what sort of
2342 machine-language programs @value{GDBN} can work with, and how it works
2345 The target architecture object is implemented as the C structure
2346 @code{struct gdbarch *}. The structure, and its methods, are generated
2347 using the Bourne shell script @file{gdbarch.sh}.
2349 @section Operating System ABI Variant Handling
2350 @cindex OS ABI variants
2352 @value{GDBN} provides a mechanism for handling variations in OS
2353 ABIs. An OS ABI variant may have influence over any number of
2354 variables in the target architecture definition. There are two major
2355 components in the OS ABI mechanism: sniffers and handlers.
2357 A @dfn{sniffer} examines a file matching a BFD architecture/flavour pair
2358 (the architecture may be wildcarded) in an attempt to determine the
2359 OS ABI of that file. Sniffers with a wildcarded architecture are considered
2360 to be @dfn{generic}, while sniffers for a specific architecture are
2361 considered to be @dfn{specific}. A match from a specific sniffer
2362 overrides a match from a generic sniffer. Multiple sniffers for an
2363 architecture/flavour may exist, in order to differentiate between two
2364 different operating systems which use the same basic file format. The
2365 OS ABI framework provides a generic sniffer for ELF-format files which
2366 examines the @code{EI_OSABI} field of the ELF header, as well as note
2367 sections known to be used by several operating systems.
2369 @cindex fine-tuning @code{gdbarch} structure
2370 A @dfn{handler} is used to fine-tune the @code{gdbarch} structure for the
2371 selected OS ABI. There may be only one handler for a given OS ABI
2372 for each BFD architecture.
2374 The following OS ABI variants are defined in @file{osabi.h}:
2378 @findex GDB_OSABI_UNKNOWN
2379 @item GDB_OSABI_UNKNOWN
2380 The ABI of the inferior is unknown. The default @code{gdbarch}
2381 settings for the architecture will be used.
2383 @findex GDB_OSABI_SVR4
2384 @item GDB_OSABI_SVR4
2385 UNIX System V Release 4
2387 @findex GDB_OSABI_HURD
2388 @item GDB_OSABI_HURD
2389 GNU using the Hurd kernel
2391 @findex GDB_OSABI_SOLARIS
2392 @item GDB_OSABI_SOLARIS
2395 @findex GDB_OSABI_OSF1
2396 @item GDB_OSABI_OSF1
2397 OSF/1, including Digital UNIX and Compaq Tru64 UNIX
2399 @findex GDB_OSABI_LINUX
2400 @item GDB_OSABI_LINUX
2401 GNU using the Linux kernel
2403 @findex GDB_OSABI_FREEBSD_AOUT
2404 @item GDB_OSABI_FREEBSD_AOUT
2405 FreeBSD using the a.out executable format
2407 @findex GDB_OSABI_FREEBSD_ELF
2408 @item GDB_OSABI_FREEBSD_ELF
2409 FreeBSD using the ELF executable format
2411 @findex GDB_OSABI_NETBSD_AOUT
2412 @item GDB_OSABI_NETBSD_AOUT
2413 NetBSD using the a.out executable format
2415 @findex GDB_OSABI_NETBSD_ELF
2416 @item GDB_OSABI_NETBSD_ELF
2417 NetBSD using the ELF executable format
2419 @findex GDB_OSABI_WINCE
2420 @item GDB_OSABI_WINCE
2423 @findex GDB_OSABI_GO32
2424 @item GDB_OSABI_GO32
2427 @findex GDB_OSABI_NETWARE
2428 @item GDB_OSABI_NETWARE
2431 @findex GDB_OSABI_ARM_EABI_V1
2432 @item GDB_OSABI_ARM_EABI_V1
2433 ARM Embedded ABI version 1
2435 @findex GDB_OSABI_ARM_EABI_V2
2436 @item GDB_OSABI_ARM_EABI_V2
2437 ARM Embedded ABI version 2
2439 @findex GDB_OSABI_ARM_APCS
2440 @item GDB_OSABI_ARM_APCS
2441 Generic ARM Procedure Call Standard
2445 Here are the functions that make up the OS ABI framework:
2447 @deftypefun const char *gdbarch_osabi_name (enum gdb_osabi @var{osabi})
2448 Return the name of the OS ABI corresponding to @var{osabi}.
2451 @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}))
2452 Register the OS ABI handler specified by @var{init_osabi} for the
2453 architecture, machine type and OS ABI specified by @var{arch},
2454 @var{machine} and @var{osabi}. In most cases, a value of zero for the
2455 machine type, which implies the architecture's default machine type,
2459 @deftypefun void gdbarch_register_osabi_sniffer (enum bfd_architecture @var{arch}, enum bfd_flavour @var{flavour}, enum gdb_osabi (*@var{sniffer})(bfd *@var{abfd}))
2460 Register the OS ABI file sniffer specified by @var{sniffer} for the
2461 BFD architecture/flavour pair specified by @var{arch} and @var{flavour}.
2462 If @var{arch} is @code{bfd_arch_unknown}, the sniffer is considered to
2463 be generic, and is allowed to examine @var{flavour}-flavoured files for
2467 @deftypefun enum gdb_osabi gdbarch_lookup_osabi (bfd *@var{abfd})
2468 Examine the file described by @var{abfd} to determine its OS ABI.
2469 The value @code{GDB_OSABI_UNKNOWN} is returned if the OS ABI cannot
2473 @deftypefun void gdbarch_init_osabi (struct gdbarch info @var{info}, struct gdbarch *@var{gdbarch}, enum gdb_osabi @var{osabi})
2474 Invoke the OS ABI handler corresponding to @var{osabi} to fine-tune the
2475 @code{gdbarch} structure specified by @var{gdbarch}. If a handler
2476 corresponding to @var{osabi} has not been registered for @var{gdbarch}'s
2477 architecture, a warning will be issued and the debugging session will continue
2478 with the defaults already established for @var{gdbarch}.
2481 @section Registers and Memory
2483 @value{GDBN}'s model of the target machine is rather simple.
2484 @value{GDBN} assumes the machine includes a bank of registers and a
2485 block of memory. Each register may have a different size.
2487 @value{GDBN} does not have a magical way to match up with the
2488 compiler's idea of which registers are which; however, it is critical
2489 that they do match up accurately. The only way to make this work is
2490 to get accurate information about the order that the compiler uses,
2491 and to reflect that in the @code{REGISTER_NAME} and related macros.
2493 @value{GDBN} can handle big-endian, little-endian, and bi-endian architectures.
2495 @section Pointers Are Not Always Addresses
2496 @cindex pointer representation
2497 @cindex address representation
2498 @cindex word-addressed machines
2499 @cindex separate data and code address spaces
2500 @cindex spaces, separate data and code address
2501 @cindex address spaces, separate data and code
2502 @cindex code pointers, word-addressed
2503 @cindex converting between pointers and addresses
2504 @cindex D10V addresses
2506 On almost all 32-bit architectures, the representation of a pointer is
2507 indistinguishable from the representation of some fixed-length number
2508 whose value is the byte address of the object pointed to. On such
2509 machines, the words ``pointer'' and ``address'' can be used interchangeably.
2510 However, architectures with smaller word sizes are often cramped for
2511 address space, so they may choose a pointer representation that breaks this
2512 identity, and allows a larger code address space.
2514 For example, the Mitsubishi D10V is a 16-bit VLIW processor whose
2515 instructions are 32 bits long@footnote{Some D10V instructions are
2516 actually pairs of 16-bit sub-instructions. However, since you can't
2517 jump into the middle of such a pair, code addresses can only refer to
2518 full 32 bit instructions, which is what matters in this explanation.}.
2519 If the D10V used ordinary byte addresses to refer to code locations,
2520 then the processor would only be able to address 64kb of instructions.
2521 However, since instructions must be aligned on four-byte boundaries, the
2522 low two bits of any valid instruction's byte address are always
2523 zero---byte addresses waste two bits. So instead of byte addresses,
2524 the D10V uses word addresses---byte addresses shifted right two bits---to
2525 refer to code. Thus, the D10V can use 16-bit words to address 256kb of
2528 However, this means that code pointers and data pointers have different
2529 forms on the D10V. The 16-bit word @code{0xC020} refers to byte address
2530 @code{0xC020} when used as a data address, but refers to byte address
2531 @code{0x30080} when used as a code address.
2533 (The D10V also uses separate code and data address spaces, which also
2534 affects the correspondence between pointers and addresses, but we're
2535 going to ignore that here; this example is already too long.)
2537 To cope with architectures like this---the D10V is not the only
2538 one!---@value{GDBN} tries to distinguish between @dfn{addresses}, which are
2539 byte numbers, and @dfn{pointers}, which are the target's representation
2540 of an address of a particular type of data. In the example above,
2541 @code{0xC020} is the pointer, which refers to one of the addresses
2542 @code{0xC020} or @code{0x30080}, depending on the type imposed upon it.
2543 @value{GDBN} provides functions for turning a pointer into an address
2544 and vice versa, in the appropriate way for the current architecture.
2546 Unfortunately, since addresses and pointers are identical on almost all
2547 processors, this distinction tends to bit-rot pretty quickly. Thus,
2548 each time you port @value{GDBN} to an architecture which does
2549 distinguish between pointers and addresses, you'll probably need to
2550 clean up some architecture-independent code.
2552 Here are functions which convert between pointers and addresses:
2554 @deftypefun CORE_ADDR extract_typed_address (void *@var{buf}, struct type *@var{type})
2555 Treat the bytes at @var{buf} as a pointer or reference of type
2556 @var{type}, and return the address it represents, in a manner
2557 appropriate for the current architecture. This yields an address
2558 @value{GDBN} can use to read target memory, disassemble, etc. Note that
2559 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2562 For example, if the current architecture is the Intel x86, this function
2563 extracts a little-endian integer of the appropriate length from
2564 @var{buf} and returns it. However, if the current architecture is the
2565 D10V, this function will return a 16-bit integer extracted from
2566 @var{buf}, multiplied by four if @var{type} is a pointer to a function.
2568 If @var{type} is not a pointer or reference type, then this function
2569 will signal an internal error.
2572 @deftypefun CORE_ADDR store_typed_address (void *@var{buf}, struct type *@var{type}, CORE_ADDR @var{addr})
2573 Store the address @var{addr} in @var{buf}, in the proper format for a
2574 pointer of type @var{type} in the current architecture. Note that
2575 @var{buf} refers to a buffer in @value{GDBN}'s memory, not the
2578 For example, if the current architecture is the Intel x86, this function
2579 stores @var{addr} unmodified as a little-endian integer of the
2580 appropriate length in @var{buf}. However, if the current architecture
2581 is the D10V, this function divides @var{addr} by four if @var{type} is
2582 a pointer to a function, and then stores it in @var{buf}.
2584 If @var{type} is not a pointer or reference type, then this function
2585 will signal an internal error.
2588 @deftypefun CORE_ADDR value_as_address (struct value *@var{val})
2589 Assuming that @var{val} is a pointer, return the address it represents,
2590 as appropriate for the current architecture.
2592 This function actually works on integral values, as well as pointers.
2593 For pointers, it performs architecture-specific conversions as
2594 described above for @code{extract_typed_address}.
2597 @deftypefun CORE_ADDR value_from_pointer (struct type *@var{type}, CORE_ADDR @var{addr})
2598 Create and return a value representing a pointer of type @var{type} to
2599 the address @var{addr}, as appropriate for the current architecture.
2600 This function performs architecture-specific conversions as described
2601 above for @code{store_typed_address}.
2605 @value{GDBN} also provides functions that do the same tasks, but assume
2606 that pointers are simply byte addresses; they aren't sensitive to the
2607 current architecture, beyond knowing the appropriate endianness.
2609 @deftypefun CORE_ADDR extract_address (void *@var{addr}, int len)
2610 Extract a @var{len}-byte number from @var{addr} in the appropriate
2611 endianness for the current architecture, and return it. Note that
2612 @var{addr} refers to @value{GDBN}'s memory, not the inferior's.
2614 This function should only be used in architecture-specific code; it
2615 doesn't have enough information to turn bits into a true address in the
2616 appropriate way for the current architecture. If you can, use
2617 @code{extract_typed_address} instead.
2620 @deftypefun void store_address (void *@var{addr}, int @var{len}, LONGEST @var{val})
2621 Store @var{val} at @var{addr} as a @var{len}-byte integer, in the
2622 appropriate endianness for the current architecture. Note that
2623 @var{addr} refers to a buffer in @value{GDBN}'s memory, not the
2626 This function should only be used in architecture-specific code; it
2627 doesn't have enough information to turn a true address into bits in the
2628 appropriate way for the current architecture. If you can, use
2629 @code{store_typed_address} instead.
2633 Here are some macros which architectures can define to indicate the
2634 relationship between pointers and addresses. These have default
2635 definitions, appropriate for architectures on which all pointers are
2636 simple unsigned byte addresses.
2638 @deftypefn {Target Macro} CORE_ADDR POINTER_TO_ADDRESS (struct type *@var{type}, char *@var{buf})
2639 Assume that @var{buf} holds a pointer of type @var{type}, in the
2640 appropriate format for the current architecture. Return the byte
2641 address the pointer refers to.
2643 This function may safely assume that @var{type} is either a pointer or a
2644 C@t{++} reference type.
2647 @deftypefn {Target Macro} void ADDRESS_TO_POINTER (struct type *@var{type}, char *@var{buf}, CORE_ADDR @var{addr})
2648 Store in @var{buf} a pointer of type @var{type} representing the address
2649 @var{addr}, in the appropriate format for the current architecture.
2651 This function may safely assume that @var{type} is either a pointer or a
2652 C@t{++} reference type.
2655 @section Address Classes
2656 @cindex address classes
2657 @cindex DW_AT_byte_size
2658 @cindex DW_AT_address_class
2660 Sometimes information about different kinds of addresses is available
2661 via the debug information. For example, some programming environments
2662 define addresses of several different sizes. If the debug information
2663 distinguishes these kinds of address classes through either the size
2664 info (e.g, @code{DW_AT_byte_size} in @w{DWARF 2}) or through an explicit
2665 address class attribute (e.g, @code{DW_AT_address_class} in @w{DWARF 2}), the
2666 following macros should be defined in order to disambiguate these
2667 types within @value{GDBN} as well as provide the added information to
2668 a @value{GDBN} user when printing type expressions.
2670 @deftypefn {Target Macro} int ADDRESS_CLASS_TYPE_FLAGS (int @var{byte_size}, int @var{dwarf2_addr_class})
2671 Returns the type flags needed to construct a pointer type whose size
2672 is @var{byte_size} and whose address class is @var{dwarf2_addr_class}.
2673 This function is normally called from within a symbol reader. See
2674 @file{dwarf2read.c}.
2677 @deftypefn {Target Macro} char *ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (int @var{type_flags})
2678 Given the type flags representing an address class qualifier, return
2681 @deftypefn {Target Macro} int ADDRESS_CLASS_NAME_to_TYPE_FLAGS (int @var{name}, int *var{type_flags_ptr})
2682 Given an address qualifier name, set the @code{int} refererenced by @var{type_flags_ptr} to the type flags
2683 for that address class qualifier.
2686 Since the need for address classes is rather rare, none of
2687 the address class macros defined by default. Predicate
2688 macros are provided to detect when they are defined.
2690 Consider a hypothetical architecture in which addresses are normally
2691 32-bits wide, but 16-bit addresses are also supported. Furthermore,
2692 suppose that the @w{DWARF 2} information for this architecture simply
2693 uses a @code{DW_AT_byte_size} value of 2 to indicate the use of one
2694 of these "short" pointers. The following functions could be defined
2695 to implement the address class macros:
2698 somearch_address_class_type_flags (int byte_size,
2699 int dwarf2_addr_class)
2702 return TYPE_FLAG_ADDRESS_CLASS_1;
2708 somearch_address_class_type_flags_to_name (int type_flags)
2710 if (type_flags & TYPE_FLAG_ADDRESS_CLASS_1)
2717 somearch_address_class_name_to_type_flags (char *name,
2718 int *type_flags_ptr)
2720 if (strcmp (name, "short") == 0)
2722 *type_flags_ptr = TYPE_FLAG_ADDRESS_CLASS_1;
2730 The qualifier @code{@@short} is used in @value{GDBN}'s type expressions
2731 to indicate the presence of one of these "short" pointers. E.g, if
2732 the debug information indicates that @code{short_ptr_var} is one of these
2733 short pointers, @value{GDBN} might show the following behavior:
2736 (gdb) ptype short_ptr_var
2737 type = int * @@short
2741 @section Raw and Virtual Register Representations
2742 @cindex raw register representation
2743 @cindex virtual register representation
2744 @cindex representations, raw and virtual registers
2746 @emph{Maintainer note: This section is pretty much obsolete. The
2747 functionality described here has largely been replaced by
2748 pseudo-registers and the mechanisms described in @ref{Target
2749 Architecture Definition, , Using Different Register and Memory Data
2750 Representations}. See also @uref{http://www.gnu.org/software/gdb/bugs/,
2751 Bug Tracking Database} and
2752 @uref{http://sources.redhat.com/gdb/current/ari/, ARI Index} for more
2753 up-to-date information.}
2755 Some architectures use one representation for a value when it lives in a
2756 register, but use a different representation when it lives in memory.
2757 In @value{GDBN}'s terminology, the @dfn{raw} representation is the one used in
2758 the target registers, and the @dfn{virtual} representation is the one
2759 used in memory, and within @value{GDBN} @code{struct value} objects.
2761 @emph{Maintainer note: Notice that the same mechanism is being used to
2762 both convert a register to a @code{struct value} and alternative
2765 For almost all data types on almost all architectures, the virtual and
2766 raw representations are identical, and no special handling is needed.
2767 However, they do occasionally differ. For example:
2771 The x86 architecture supports an 80-bit @code{long double} type. However, when
2772 we store those values in memory, they occupy twelve bytes: the
2773 floating-point number occupies the first ten, and the final two bytes
2774 are unused. This keeps the values aligned on four-byte boundaries,
2775 allowing more efficient access. Thus, the x86 80-bit floating-point
2776 type is the raw representation, and the twelve-byte loosely-packed
2777 arrangement is the virtual representation.
2780 Some 64-bit MIPS targets present 32-bit registers to @value{GDBN} as 64-bit
2781 registers, with garbage in their upper bits. @value{GDBN} ignores the top 32
2782 bits. Thus, the 64-bit form, with garbage in the upper 32 bits, is the
2783 raw representation, and the trimmed 32-bit representation is the
2784 virtual representation.
2787 In general, the raw representation is determined by the architecture, or
2788 @value{GDBN}'s interface to the architecture, while the virtual representation
2789 can be chosen for @value{GDBN}'s convenience. @value{GDBN}'s register file,
2790 @code{registers}, holds the register contents in raw format, and the
2791 @value{GDBN} remote protocol transmits register values in raw format.
2793 Your architecture may define the following macros to request
2794 conversions between the raw and virtual format:
2796 @deftypefn {Target Macro} int REGISTER_CONVERTIBLE (int @var{reg})
2797 Return non-zero if register number @var{reg}'s value needs different raw
2798 and virtual formats.
2800 You should not use @code{REGISTER_CONVERT_TO_VIRTUAL} for a register
2801 unless this macro returns a non-zero value for that register.
2804 @deftypefn {Target Macro} int REGISTER_RAW_SIZE (int @var{reg})
2805 The size of register number @var{reg}'s raw value. This is the number
2806 of bytes the register will occupy in @code{registers}, or in a @value{GDBN}
2807 remote protocol packet.
2810 @deftypefn {Target Macro} int REGISTER_VIRTUAL_SIZE (int @var{reg})
2811 The size of register number @var{reg}'s value, in its virtual format.
2812 This is the size a @code{struct value}'s buffer will have, holding that
2816 @deftypefn {Target Macro} struct type *REGISTER_VIRTUAL_TYPE (int @var{reg})
2817 This is the type of the virtual representation of register number
2818 @var{reg}. Note that there is no need for a macro giving a type for the
2819 register's raw form; once the register's value has been obtained, @value{GDBN}
2820 always uses the virtual form.
2823 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_VIRTUAL (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2824 Convert the value of register number @var{reg} to @var{type}, which
2825 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2826 at @var{from} holds the register's value in raw format; the macro should
2827 convert the value to virtual format, and place it at @var{to}.
2829 Note that @code{REGISTER_CONVERT_TO_VIRTUAL} and
2830 @code{REGISTER_CONVERT_TO_RAW} take their @var{reg} and @var{type}
2831 arguments in different orders.
2833 You should only use @code{REGISTER_CONVERT_TO_VIRTUAL} with registers
2834 for which the @code{REGISTER_CONVERTIBLE} macro returns a non-zero
2838 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_RAW (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2839 Convert the value of register number @var{reg} to @var{type}, which
2840 should always be @code{REGISTER_VIRTUAL_TYPE (@var{reg})}. The buffer
2841 at @var{from} holds the register's value in raw format; the macro should
2842 convert the value to virtual format, and place it at @var{to}.
2844 Note that REGISTER_CONVERT_TO_VIRTUAL and REGISTER_CONVERT_TO_RAW take
2845 their @var{reg} and @var{type} arguments in different orders.
2849 @section Using Different Register and Memory Data Representations
2850 @cindex register representation
2851 @cindex memory representation
2852 @cindex representations, register and memory
2853 @cindex register data formats, converting
2854 @cindex @code{struct value}, converting register contents to
2856 @emph{Maintainer's note: The way GDB manipulates registers is undergoing
2857 significant change. Many of the macros and functions refered to in this
2858 section are likely to be subject to further revision. See
2859 @uref{http://sources.redhat.com/gdb/current/ari/, A.R. Index} and
2860 @uref{http://www.gnu.org/software/gdb/bugs, Bug Tracking Database} for
2861 further information. cagney/2002-05-06.}
2863 Some architectures can represent a data object in a register using a
2864 form that is different to the objects more normal memory representation.
2870 The Alpha architecture can represent 32 bit integer values in
2871 floating-point registers.
2874 The x86 architecture supports 80-bit floating-point registers. The
2875 @code{long double} data type occupies 96 bits in memory but only 80 bits
2876 when stored in a register.
2880 In general, the register representation of a data type is determined by
2881 the architecture, or @value{GDBN}'s interface to the architecture, while
2882 the memory representation is determined by the Application Binary
2885 For almost all data types on almost all architectures, the two
2886 representations are identical, and no special handling is needed.
2887 However, they do occasionally differ. Your architecture may define the
2888 following macros to request conversions between the register and memory
2889 representations of a data type:
2891 @deftypefn {Target Macro} int CONVERT_REGISTER_P (int @var{reg})
2892 Return non-zero if the representation of a data value stored in this
2893 register may be different to the representation of that same data value
2894 when stored in memory.
2896 When non-zero, the macros @code{REGISTER_TO_VALUE} and
2897 @code{VALUE_TO_REGISTER} are used to perform any necessary conversion.
2900 @deftypefn {Target Macro} void REGISTER_TO_VALUE (int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
2901 Convert the value of register number @var{reg} to a data object of type
2902 @var{type}. The buffer at @var{from} holds the register's value in raw
2903 format; the converted value should be placed in the buffer at @var{to}.
2905 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2906 their @var{reg} and @var{type} arguments in different orders.
2908 You should only use @code{REGISTER_TO_VALUE} with registers for which
2909 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2912 @deftypefn {Target Macro} void VALUE_TO_REGISTER (struct type *@var{type}, int @var{reg}, char *@var{from}, char *@var{to})
2913 Convert a data value of type @var{type} to register number @var{reg}'
2916 Note that @code{REGISTER_TO_VALUE} and @code{VALUE_TO_REGISTER} take
2917 their @var{reg} and @var{type} arguments in different orders.
2919 You should only use @code{VALUE_TO_REGISTER} with registers for which
2920 the @code{CONVERT_REGISTER_P} macro returns a non-zero value.
2923 @deftypefn {Target Macro} void REGISTER_CONVERT_TO_TYPE (int @var{regnum}, struct type *@var{type}, char *@var{buf})
2924 See @file{mips-tdep.c}. It does not do what you want.
2928 @section Frame Interpretation
2930 @section Inferior Call Setup
2932 @section Compiler Characteristics
2934 @section Target Conditionals
2936 This section describes the macros that you can use to define the target
2941 @item ADDR_BITS_REMOVE (addr)
2942 @findex ADDR_BITS_REMOVE
2943 If a raw machine instruction address includes any bits that are not
2944 really part of the address, then define this macro to expand into an
2945 expression that zeroes those bits in @var{addr}. This is only used for
2946 addresses of instructions, and even then not in all contexts.
2948 For example, the two low-order bits of the PC on the Hewlett-Packard PA
2949 2.0 architecture contain the privilege level of the corresponding
2950 instruction. Since instructions must always be aligned on four-byte
2951 boundaries, the processor masks out these bits to generate the actual
2952 address of the instruction. ADDR_BITS_REMOVE should filter out these
2953 bits with an expression such as @code{((addr) & ~3)}.
2955 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS (@var{name}, @var{type_flags_ptr})
2956 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS
2957 If @var{name} is a valid address class qualifier name, set the @code{int}
2958 referenced by @var{type_flags_ptr} to the mask representing the qualifier
2959 and return 1. If @var{name} is not a valid address class qualifier name,
2962 The value for @var{type_flags_ptr} should be one of
2963 @code{TYPE_FLAG_ADDRESS_CLASS_1}, @code{TYPE_FLAG_ADDRESS_CLASS_2}, or
2964 possibly some combination of these values or'd together.
2965 @xref{Target Architecture Definition, , Address Classes}.
2967 @item ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P ()
2968 @findex ADDRESS_CLASS_NAME_TO_TYPE_FLAGS_P
2969 Predicate which indicates whether @code{ADDRESS_CLASS_NAME_TO_TYPE_FLAGS}
2972 @item ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2973 @findex ADDRESS_CLASS_TYPE_FLAGS (@var{byte_size}, @var{dwarf2_addr_class})
2974 Given a pointers byte size (as described by the debug information) and
2975 the possible @code{DW_AT_address_class} value, return the type flags
2976 used by @value{GDBN} to represent this address class. The value
2977 returned should be one of @code{TYPE_FLAG_ADDRESS_CLASS_1},
2978 @code{TYPE_FLAG_ADDRESS_CLASS_2}, or possibly some combination of these
2979 values or'd together.
2980 @xref{Target Architecture Definition, , Address Classes}.
2982 @item ADDRESS_CLASS_TYPE_FLAGS_P ()
2983 @findex ADDRESS_CLASS_TYPE_FLAGS_P
2984 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS} has
2987 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME (@var{type_flags})
2988 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME
2989 Return the name of the address class qualifier associated with the type
2990 flags given by @var{type_flags}.
2992 @item ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P ()
2993 @findex ADDRESS_CLASS_TYPE_FLAGS_TO_NAME_P
2994 Predicate which indicates whether @code{ADDRESS_CLASS_TYPE_FLAGS_TO_NAME} has
2996 @xref{Target Architecture Definition, , Address Classes}.
2998 @item ADDRESS_TO_POINTER (@var{type}, @var{buf}, @var{addr})
2999 @findex ADDRESS_TO_POINTER
3000 Store in @var{buf} a pointer of type @var{type} representing the address
3001 @var{addr}, in the appropriate format for the current architecture.
3002 This macro may safely assume that @var{type} is either a pointer or a
3003 C@t{++} reference type.
3004 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3006 @item BELIEVE_PCC_PROMOTION
3007 @findex BELIEVE_PCC_PROMOTION
3008 Define if the compiler promotes a @code{short} or @code{char}
3009 parameter to an @code{int}, but still reports the parameter as its
3010 original type, rather than the promoted type.
3012 @item BELIEVE_PCC_PROMOTION_TYPE
3013 @findex BELIEVE_PCC_PROMOTION_TYPE
3014 Define this if @value{GDBN} should believe the type of a @code{short}
3015 argument when compiled by @code{pcc}, but look within a full int space to get
3016 its value. Only defined for Sun-3 at present.
3018 @item BITS_BIG_ENDIAN
3019 @findex BITS_BIG_ENDIAN
3020 Define this if the numbering of bits in the targets does @strong{not} match the
3021 endianness of the target byte order. A value of 1 means that the bits
3022 are numbered in a big-endian bit order, 0 means little-endian.
3026 This is the character array initializer for the bit pattern to put into
3027 memory where a breakpoint is set. Although it's common to use a trap
3028 instruction for a breakpoint, it's not required; for instance, the bit
3029 pattern could be an invalid instruction. The breakpoint must be no
3030 longer than the shortest instruction of the architecture.
3032 @code{BREAKPOINT} has been deprecated in favor of
3033 @code{BREAKPOINT_FROM_PC}.
3035 @item BIG_BREAKPOINT
3036 @itemx LITTLE_BREAKPOINT
3037 @findex LITTLE_BREAKPOINT
3038 @findex BIG_BREAKPOINT
3039 Similar to BREAKPOINT, but used for bi-endian targets.
3041 @code{BIG_BREAKPOINT} and @code{LITTLE_BREAKPOINT} have been deprecated in
3042 favor of @code{BREAKPOINT_FROM_PC}.
3044 @item REMOTE_BREAKPOINT
3045 @itemx LITTLE_REMOTE_BREAKPOINT
3046 @itemx BIG_REMOTE_BREAKPOINT
3047 @findex BIG_REMOTE_BREAKPOINT
3048 @findex LITTLE_REMOTE_BREAKPOINT
3049 @findex REMOTE_BREAKPOINT
3050 Similar to BREAKPOINT, but used for remote targets.
3052 @code{BIG_REMOTE_BREAKPOINT} and @code{LITTLE_REMOTE_BREAKPOINT} have been
3053 deprecated in favor of @code{BREAKPOINT_FROM_PC}.
3055 @item BREAKPOINT_FROM_PC (@var{pcptr}, @var{lenptr})
3056 @findex BREAKPOINT_FROM_PC
3057 Use the program counter to determine the contents and size of a
3058 breakpoint instruction. It returns a pointer to a string of bytes
3059 that encode a breakpoint instruction, stores the length of the string
3060 to *@var{lenptr}, and adjusts pc (if necessary) to point to the actual
3061 memory location where the breakpoint should be inserted.
3063 Although it is common to use a trap instruction for a breakpoint, it's
3064 not required; for instance, the bit pattern could be an invalid
3065 instruction. The breakpoint must be no longer than the shortest
3066 instruction of the architecture.
3068 Replaces all the other @var{BREAKPOINT} macros.
3070 @item MEMORY_INSERT_BREAKPOINT (@var{addr}, @var{contents_cache})
3071 @itemx MEMORY_REMOVE_BREAKPOINT (@var{addr}, @var{contents_cache})
3072 @findex MEMORY_REMOVE_BREAKPOINT
3073 @findex MEMORY_INSERT_BREAKPOINT
3074 Insert or remove memory based breakpoints. Reasonable defaults
3075 (@code{default_memory_insert_breakpoint} and
3076 @code{default_memory_remove_breakpoint} respectively) have been
3077 provided so that it is not necessary to define these for most
3078 architectures. Architectures which may want to define
3079 @code{MEMORY_INSERT_BREAKPOINT} and @code{MEMORY_REMOVE_BREAKPOINT} will
3080 likely have instructions that are oddly sized or are not stored in a
3081 conventional manner.
3083 It may also be desirable (from an efficiency standpoint) to define
3084 custom breakpoint insertion and removal routines if
3085 @code{BREAKPOINT_FROM_PC} needs to read the target's memory for some
3088 @item CALL_DUMMY_WORDS
3089 @findex CALL_DUMMY_WORDS
3090 Pointer to an array of @code{LONGEST} words of data containing
3091 host-byte-ordered @code{REGISTER_BYTES} sized values that partially
3092 specify the sequence of instructions needed for an inferior function
3095 Should be deprecated in favor of a macro that uses target-byte-ordered
3098 @item SIZEOF_CALL_DUMMY_WORDS
3099 @findex SIZEOF_CALL_DUMMY_WORDS
3100 The size of @code{CALL_DUMMY_WORDS}. This must return a positive value.
3101 See also @code{CALL_DUMMY_LENGTH}.
3105 A static initializer for @code{CALL_DUMMY_WORDS}. Deprecated.
3107 @item CALL_DUMMY_LOCATION
3108 @findex CALL_DUMMY_LOCATION
3109 See the file @file{inferior.h}.
3111 @item DEPRECATED_CALL_DUMMY_STACK_ADJUST
3112 @findex DEPRECATED_CALL_DUMMY_STACK_ADJUST
3113 Stack adjustment needed when performing an inferior function call. This
3114 function is no longer needed. @xref{push_dummy_call}, which can handle
3115 all alignment directly.
3117 @item CANNOT_FETCH_REGISTER (@var{regno})
3118 @findex CANNOT_FETCH_REGISTER
3119 A C expression that should be nonzero if @var{regno} cannot be fetched
3120 from an inferior process. This is only relevant if
3121 @code{FETCH_INFERIOR_REGISTERS} is not defined.
3123 @item CANNOT_STORE_REGISTER (@var{regno})
3124 @findex CANNOT_STORE_REGISTER
3125 A C expression that should be nonzero if @var{regno} should not be
3126 written to the target. This is often the case for program counters,
3127 status words, and other special registers. If this is not defined,
3128 @value{GDBN} will assume that all registers may be written.
3130 @item DO_DEFERRED_STORES
3131 @itemx CLEAR_DEFERRED_STORES
3132 @findex CLEAR_DEFERRED_STORES
3133 @findex DO_DEFERRED_STORES
3134 Define this to execute any deferred stores of registers into the inferior,
3135 and to cancel any deferred stores.
3137 Currently only implemented correctly for native Sparc configurations?
3139 @item int CONVERT_REGISTER_P(@var{regnum})
3140 @findex CONVERT_REGISTER_P
3141 Return non-zero if register @var{regnum} can represent data values in a
3143 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3145 @item DECR_PC_AFTER_BREAK
3146 @findex DECR_PC_AFTER_BREAK
3147 Define this to be the amount by which to decrement the PC after the
3148 program encounters a breakpoint. This is often the number of bytes in
3149 @code{BREAKPOINT}, though not always. For most targets this value will be 0.
3151 @item DECR_PC_AFTER_HW_BREAK
3152 @findex DECR_PC_AFTER_HW_BREAK
3153 Similarly, for hardware breakpoints.
3155 @item DISABLE_UNSETTABLE_BREAK (@var{addr})
3156 @findex DISABLE_UNSETTABLE_BREAK
3157 If defined, this should evaluate to 1 if @var{addr} is in a shared
3158 library in which breakpoints cannot be set and so should be disabled.
3160 @item PRINT_FLOAT_INFO()
3161 @findex PRINT_FLOAT_INFO
3162 If defined, then the @samp{info float} command will print information about
3163 the processor's floating point unit.
3165 @item print_registers_info (@var{gdbarch}, @var{frame}, @var{regnum}, @var{all})
3166 @findex print_registers_info
3167 If defined, pretty print the value of the register @var{regnum} for the
3168 specified @var{frame}. If the value of @var{regnum} is -1, pretty print
3169 either all registers (@var{all} is non zero) or a select subset of
3170 registers (@var{all} is zero).
3172 The default method prints one register per line, and if @var{all} is
3173 zero omits floating-point registers.
3175 @item PRINT_VECTOR_INFO()
3176 @findex PRINT_VECTOR_INFO
3177 If defined, then the @samp{info vector} command will call this function
3178 to print information about the processor's vector unit.
3180 By default, the @samp{info vector} command will print all vector
3181 registers (the register's type having the vector attribute).
3183 @item DWARF_REG_TO_REGNUM
3184 @findex DWARF_REG_TO_REGNUM
3185 Convert DWARF register number into @value{GDBN} regnum. If not defined,
3186 no conversion will be performed.
3188 @item DWARF2_REG_TO_REGNUM
3189 @findex DWARF2_REG_TO_REGNUM
3190 Convert DWARF2 register number into @value{GDBN} regnum. If not
3191 defined, no conversion will be performed.
3193 @item ECOFF_REG_TO_REGNUM
3194 @findex ECOFF_REG_TO_REGNUM
3195 Convert ECOFF register number into @value{GDBN} regnum. If not defined,
3196 no conversion will be performed.
3198 @item END_OF_TEXT_DEFAULT
3199 @findex END_OF_TEXT_DEFAULT
3200 This is an expression that should designate the end of the text section.
3203 @item EXTRACT_RETURN_VALUE(@var{type}, @var{regbuf}, @var{valbuf})
3204 @findex EXTRACT_RETURN_VALUE
3205 Define this to extract a function's return value of type @var{type} from
3206 the raw register state @var{regbuf} and copy that, in virtual format,
3209 @item EXTRACT_STRUCT_VALUE_ADDRESS(@var{regbuf})
3210 @findex EXTRACT_STRUCT_VALUE_ADDRESS
3211 When defined, extract from the array @var{regbuf} (containing the raw
3212 register state) the @code{CORE_ADDR} at which a function should return
3213 its structure value.
3215 If not defined, @code{EXTRACT_RETURN_VALUE} is used.
3217 @item EXTRACT_STRUCT_VALUE_ADDRESS_P()
3218 @findex EXTRACT_STRUCT_VALUE_ADDRESS_P
3219 Predicate for @code{EXTRACT_STRUCT_VALUE_ADDRESS}.
3221 @item DEPRECATED_FP_REGNUM
3222 @findex DEPRECATED_FP_REGNUM
3223 If the virtual frame pointer is kept in a register, then define this
3224 macro to be the number (greater than or equal to zero) of that register.
3226 This should only need to be defined if @code{DEPRECATED_TARGET_READ_FP}
3229 @item FRAMELESS_FUNCTION_INVOCATION(@var{fi})
3230 @findex FRAMELESS_FUNCTION_INVOCATION
3231 Define this to an expression that returns 1 if the function invocation
3232 represented by @var{fi} does not have a stack frame associated with it.
3235 @item frame_align (@var{address})
3236 @anchor{frame_align}
3238 Define this to adjust @var{address} so that it meets the alignment
3239 requirements for the start of a new stack frame. A stack frame's
3240 alignment requirements are typically stronger than a target processors
3241 stack alignment requirements (@pxref{STACK_ALIGN}).
3243 This function is used to ensure that, when creating a dummy frame, both
3244 the initial stack pointer and (if needed) the address of the return
3245 value are correctly aligned.
3247 Unlike @code{STACK_ALIGN}, this function always adjusts the address in
3248 the direction of stack growth.
3250 By default, no frame based stack alignment is performed.
3252 @item FRAME_ARGS_ADDRESS_CORRECT
3253 @findex FRAME_ARGS_ADDRESS_CORRECT
3256 @item DEPRECATED_FRAME_CHAIN(@var{frame})
3257 @findex DEPRECATED_FRAME_CHAIN
3258 Given @var{frame}, return a pointer to the calling frame.
3260 @item DEPRECATED_FRAME_CHAIN_VALID(@var{chain}, @var{thisframe})
3261 @findex DEPRECATED_FRAME_CHAIN_VALID
3262 Define this to be an expression that returns zero if the given frame is an
3263 outermost frame, with no caller, and nonzero otherwise. Most normal
3264 situations can be handled without defining this macro, including @code{NULL}
3265 chain pointers, dummy frames, and frames whose PC values are inside the
3266 startup file (e.g.@: @file{crt0.o}), inside @code{main}, or inside
3269 @item DEPRECATED_FRAME_INIT_SAVED_REGS(@var{frame})
3270 @findex DEPRECATED_FRAME_INIT_SAVED_REGS
3271 See @file{frame.h}. Determines the address of all registers in the
3272 current stack frame storing each in @code{frame->saved_regs}. Space for
3273 @code{frame->saved_regs} shall be allocated by
3274 @code{DEPRECATED_FRAME_INIT_SAVED_REGS} using
3275 @code{frame_saved_regs_zalloc}.
3277 @code{FRAME_FIND_SAVED_REGS} is deprecated.
3279 @item FRAME_NUM_ARGS (@var{fi})
3280 @findex FRAME_NUM_ARGS
3281 For the frame described by @var{fi} return the number of arguments that
3282 are being passed. If the number of arguments is not known, return
3285 @item DEPRECATED_FRAME_SAVED_PC(@var{frame})
3286 @findex DEPRECATED_FRAME_SAVED_PC
3287 @anchor{DEPRECATED_FRAME_SAVED_PC} Given @var{frame}, return the pc
3288 saved there. This is the return address.
3290 This method is deprecated. @xref{unwind_pc}.
3292 @item CORE_ADDR unwind_pc (struct frame_info *@var{this_frame})
3294 @anchor{unwind_pc} Return the instruction address, in @var{this_frame}'s
3295 caller, at which execution will resume after @var{this_frame} returns.
3296 This is commonly refered to as the return address.
3298 The implementation, which must be frame agnostic (work with any frame),
3299 is typically no more than:
3303 frame_unwind_unsigned_register (this_frame, D10V_PC_REGNUM, &pc);
3304 return d10v_make_iaddr (pc);
3308 @xref{DEPRECATED_FRAME_SAVED_PC}, which this method replaces.
3310 @item FUNCTION_EPILOGUE_SIZE
3311 @findex FUNCTION_EPILOGUE_SIZE
3312 For some COFF targets, the @code{x_sym.x_misc.x_fsize} field of the
3313 function end symbol is 0. For such targets, you must define
3314 @code{FUNCTION_EPILOGUE_SIZE} to expand into the standard size of a
3315 function's epilogue.
3317 @item FUNCTION_START_OFFSET
3318 @findex FUNCTION_START_OFFSET
3319 An integer, giving the offset in bytes from a function's address (as
3320 used in the values of symbols, function pointers, etc.), and the
3321 function's first genuine instruction.
3323 This is zero on almost all machines: the function's address is usually
3324 the address of its first instruction. However, on the VAX, for example,
3325 each function starts with two bytes containing a bitmask indicating
3326 which registers to save upon entry to the function. The VAX @code{call}
3327 instructions check this value, and save the appropriate registers
3328 automatically. Thus, since the offset from the function's address to
3329 its first instruction is two bytes, @code{FUNCTION_START_OFFSET} would
3332 @item GCC_COMPILED_FLAG_SYMBOL
3333 @itemx GCC2_COMPILED_FLAG_SYMBOL
3334 @findex GCC2_COMPILED_FLAG_SYMBOL
3335 @findex GCC_COMPILED_FLAG_SYMBOL
3336 If defined, these are the names of the symbols that @value{GDBN} will
3337 look for to detect that GCC compiled the file. The default symbols
3338 are @code{gcc_compiled.} and @code{gcc2_compiled.},
3339 respectively. (Currently only defined for the Delta 68.)
3341 @item @value{GDBN}_MULTI_ARCH
3342 @findex @value{GDBN}_MULTI_ARCH
3343 If defined and non-zero, enables support for multiple architectures
3344 within @value{GDBN}.
3346 This support can be enabled at two levels. At level one, only
3347 definitions for previously undefined macros are provided; at level two,
3348 a multi-arch definition of all architecture dependent macros will be
3351 @item @value{GDBN}_TARGET_IS_HPPA
3352 @findex @value{GDBN}_TARGET_IS_HPPA
3353 This determines whether horrible kludge code in @file{dbxread.c} and
3354 @file{partial-stab.h} is used to mangle multiple-symbol-table files from
3355 HPPA's. This should all be ripped out, and a scheme like @file{elfread.c}
3358 @item GET_LONGJMP_TARGET
3359 @findex GET_LONGJMP_TARGET
3360 For most machines, this is a target-dependent parameter. On the
3361 DECstation and the Iris, this is a native-dependent parameter, since
3362 the header file @file{setjmp.h} is needed to define it.
3364 This macro determines the target PC address that @code{longjmp} will jump to,
3365 assuming that we have just stopped at a @code{longjmp} breakpoint. It takes a
3366 @code{CORE_ADDR *} as argument, and stores the target PC value through this
3367 pointer. It examines the current state of the machine as needed.
3369 @item DEPRECATED_GET_SAVED_REGISTER
3370 @findex DEPRECATED_GET_SAVED_REGISTER
3371 Define this if you need to supply your own definition for the function
3372 @code{DEPRECATED_GET_SAVED_REGISTER}.
3374 @item IBM6000_TARGET
3375 @findex IBM6000_TARGET
3376 Shows that we are configured for an IBM RS/6000 target. This
3377 conditional should be eliminated (FIXME) and replaced by
3378 feature-specific macros. It was introduced in a haste and we are
3379 repenting at leisure.
3381 @item I386_USE_GENERIC_WATCHPOINTS
3382 An x86-based target can define this to use the generic x86 watchpoint
3383 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
3385 @item SYMBOLS_CAN_START_WITH_DOLLAR
3386 @findex SYMBOLS_CAN_START_WITH_DOLLAR
3387 Some systems have routines whose names start with @samp{$}. Giving this
3388 macro a non-zero value tells @value{GDBN}'s expression parser to check for such
3389 routines when parsing tokens that begin with @samp{$}.
3391 On HP-UX, certain system routines (millicode) have names beginning with
3392 @samp{$} or @samp{$$}. For example, @code{$$dyncall} is a millicode
3393 routine that handles inter-space procedure calls on PA-RISC.
3395 @item DEPRECATED_INIT_EXTRA_FRAME_INFO (@var{fromleaf}, @var{frame})
3396 @findex DEPRECATED_INIT_EXTRA_FRAME_INFO
3397 If additional information about the frame is required this should be
3398 stored in @code{frame->extra_info}. Space for @code{frame->extra_info}
3399 is allocated using @code{frame_extra_info_zalloc}.
3401 @item DEPRECATED_INIT_FRAME_PC (@var{fromleaf}, @var{prev})
3402 @findex DEPRECATED_INIT_FRAME_PC
3403 This is a C statement that sets the pc of the frame pointed to by
3404 @var{prev}. [By default...]
3406 @item INNER_THAN (@var{lhs}, @var{rhs})
3408 Returns non-zero if stack address @var{lhs} is inner than (nearer to the
3409 stack top) stack address @var{rhs}. Define this as @code{lhs < rhs} if
3410 the target's stack grows downward in memory, or @code{lhs > rsh} if the
3413 @item gdbarch_in_function_epilogue_p (@var{gdbarch}, @var{pc})
3414 @findex gdbarch_in_function_epilogue_p
3415 Returns non-zero if the given @var{pc} is in the epilogue of a function.
3416 The epilogue of a function is defined as the part of a function where
3417 the stack frame of the function already has been destroyed up to the
3418 final `return from function call' instruction.
3420 @item SIGTRAMP_START (@var{pc})
3421 @findex SIGTRAMP_START
3422 @itemx SIGTRAMP_END (@var{pc})
3423 @findex SIGTRAMP_END
3424 Define these to be the start and end address of the @code{sigtramp} for the
3425 given @var{pc}. On machines where the address is just a compile time
3426 constant, the macro expansion will typically just ignore the supplied
3429 @item IN_SOLIB_CALL_TRAMPOLINE (@var{pc}, @var{name})
3430 @findex IN_SOLIB_CALL_TRAMPOLINE
3431 Define this to evaluate to nonzero if the program is stopped in the
3432 trampoline that connects to a shared library.
3434 @item IN_SOLIB_RETURN_TRAMPOLINE (@var{pc}, @var{name})
3435 @findex IN_SOLIB_RETURN_TRAMPOLINE
3436 Define this to evaluate to nonzero if the program is stopped in the
3437 trampoline that returns from a shared library.
3439 @item IN_SOLIB_DYNSYM_RESOLVE_CODE (@var{pc})
3440 @findex IN_SOLIB_DYNSYM_RESOLVE_CODE
3441 Define this to evaluate to nonzero if the program is stopped in the
3444 @item SKIP_SOLIB_RESOLVER (@var{pc})
3445 @findex SKIP_SOLIB_RESOLVER
3446 Define this to evaluate to the (nonzero) address at which execution
3447 should continue to get past the dynamic linker's symbol resolution
3448 function. A zero value indicates that it is not important or necessary
3449 to set a breakpoint to get through the dynamic linker and that single
3450 stepping will suffice.
3452 @item INTEGER_TO_ADDRESS (@var{type}, @var{buf})
3453 @findex INTEGER_TO_ADDRESS
3454 @cindex converting integers to addresses
3455 Define this when the architecture needs to handle non-pointer to address
3456 conversions specially. Converts that value to an address according to
3457 the current architectures conventions.
3459 @emph{Pragmatics: When the user copies a well defined expression from
3460 their source code and passes it, as a parameter, to @value{GDBN}'s
3461 @code{print} command, they should get the same value as would have been
3462 computed by the target program. Any deviation from this rule can cause
3463 major confusion and annoyance, and needs to be justified carefully. In
3464 other words, @value{GDBN} doesn't really have the freedom to do these
3465 conversions in clever and useful ways. It has, however, been pointed
3466 out that users aren't complaining about how @value{GDBN} casts integers
3467 to pointers; they are complaining that they can't take an address from a
3468 disassembly listing and give it to @code{x/i}. Adding an architecture
3469 method like @code{INTEGER_TO_ADDRESS} certainly makes it possible for
3470 @value{GDBN} to ``get it right'' in all circumstances.}
3472 @xref{Target Architecture Definition, , Pointers Are Not Always
3475 @item NEED_TEXT_START_END
3476 @findex NEED_TEXT_START_END
3477 Define this if @value{GDBN} should determine the start and end addresses of the
3478 text section. (Seems dubious.)
3480 @item NO_HIF_SUPPORT
3481 @findex NO_HIF_SUPPORT
3482 (Specific to the a29k.)
3484 @item POINTER_TO_ADDRESS (@var{type}, @var{buf})
3485 @findex POINTER_TO_ADDRESS
3486 Assume that @var{buf} holds a pointer of type @var{type}, in the
3487 appropriate format for the current architecture. Return the byte
3488 address the pointer refers to.
3489 @xref{Target Architecture Definition, , Pointers Are Not Always Addresses}.
3491 @item REGISTER_CONVERTIBLE (@var{reg})
3492 @findex REGISTER_CONVERTIBLE
3493 Return non-zero if @var{reg} uses different raw and virtual formats.
3494 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3496 @item REGISTER_TO_VALUE(@var{regnum}, @var{type}, @var{from}, @var{to})
3497 @findex REGISTER_TO_VALUE
3498 Convert the raw contents of register @var{regnum} into a value of type
3500 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3502 @item REGISTER_RAW_SIZE (@var{reg})
3503 @findex REGISTER_RAW_SIZE
3504 Return the raw size of @var{reg}; defaults to the size of the register's
3506 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3508 @item register_reggroup_p (@var{gdbarch}, @var{regnum}, @var{reggroup})
3509 @findex register_reggroup_p
3510 @cindex register groups
3511 Return non-zero if register @var{regnum} is a member of the register
3512 group @var{reggroup}.
3514 By default, registers are grouped as follows:
3517 @item float_reggroup
3518 Any register with a valid name and a floating-point type.
3519 @item vector_reggroup
3520 Any register with a valid name and a vector type.
3521 @item general_reggroup
3522 Any register with a valid name and a type other than vector or
3523 floating-point. @samp{float_reggroup}.
3525 @itemx restore_reggroup
3527 Any register with a valid name.
3530 @item REGISTER_VIRTUAL_SIZE (@var{reg})
3531 @findex REGISTER_VIRTUAL_SIZE
3532 Return the virtual size of @var{reg}; defaults to the size of the
3533 register's virtual type.
3534 Return the virtual size of @var{reg}.
3535 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3537 @item REGISTER_VIRTUAL_TYPE (@var{reg})
3538 @findex REGISTER_VIRTUAL_TYPE
3539 Return the virtual type of @var{reg}.
3540 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3542 @item struct type *register_type (@var{gdbarch}, @var{reg})
3543 @findex register_type
3544 If defined, return the type of register @var{reg}. This function
3545 superseeds @code{REGISTER_VIRTUAL_TYPE}. @xref{Target Architecture
3546 Definition, , Raw and Virtual Register Representations}.
3548 @item REGISTER_CONVERT_TO_VIRTUAL(@var{reg}, @var{type}, @var{from}, @var{to})
3549 @findex REGISTER_CONVERT_TO_VIRTUAL
3550 Convert the value of register @var{reg} from its raw form to its virtual
3552 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3554 @item REGISTER_CONVERT_TO_RAW(@var{type}, @var{reg}, @var{from}, @var{to})
3555 @findex REGISTER_CONVERT_TO_RAW
3556 Convert the value of register @var{reg} from its virtual form to its raw
3558 @xref{Target Architecture Definition, , Raw and Virtual Register Representations}.
3560 @item RETURN_VALUE_ON_STACK(@var{type})
3561 @findex RETURN_VALUE_ON_STACK
3562 @cindex returning structures by value
3563 @cindex structures, returning by value
3565 Return non-zero if values of type TYPE are returned on the stack, using
3566 the ``struct convention'' (i.e., the caller provides a pointer to a
3567 buffer in which the callee should store the return value). This
3568 controls how the @samp{finish} command finds a function's return value,
3569 and whether an inferior function call reserves space on the stack for
3572 The full logic @value{GDBN} uses here is kind of odd.
3576 If the type being returned by value is not a structure, union, or array,
3577 and @code{RETURN_VALUE_ON_STACK} returns zero, then @value{GDBN}
3578 concludes the value is not returned using the struct convention.
3581 Otherwise, @value{GDBN} calls @code{USE_STRUCT_CONVENTION} (see below).
3582 If that returns non-zero, @value{GDBN} assumes the struct convention is
3586 In other words, to indicate that a given type is returned by value using
3587 the struct convention, that type must be either a struct, union, array,
3588 or something @code{RETURN_VALUE_ON_STACK} likes, @emph{and} something
3589 that @code{USE_STRUCT_CONVENTION} likes.
3591 Note that, in C and C@t{++}, arrays are never returned by value. In those
3592 languages, these predicates will always see a pointer type, never an
3593 array type. All the references above to arrays being returned by value
3594 apply only to other languages.
3596 @item SOFTWARE_SINGLE_STEP_P()
3597 @findex SOFTWARE_SINGLE_STEP_P
3598 Define this as 1 if the target does not have a hardware single-step
3599 mechanism. The macro @code{SOFTWARE_SINGLE_STEP} must also be defined.
3601 @item SOFTWARE_SINGLE_STEP(@var{signal}, @var{insert_breapoints_p})
3602 @findex SOFTWARE_SINGLE_STEP
3603 A function that inserts or removes (depending on
3604 @var{insert_breapoints_p}) breakpoints at each possible destinations of
3605 the next instruction. See @file{sparc-tdep.c} and @file{rs6000-tdep.c}
3608 @item SOFUN_ADDRESS_MAYBE_MISSING
3609 @findex SOFUN_ADDRESS_MAYBE_MISSING
3610 Somebody clever observed that, the more actual addresses you have in the
3611 debug information, the more time the linker has to spend relocating
3612 them. So whenever there's some other way the debugger could find the
3613 address it needs, you should omit it from the debug info, to make
3616 @code{SOFUN_ADDRESS_MAYBE_MISSING} indicates that a particular set of
3617 hacks of this sort are in use, affecting @code{N_SO} and @code{N_FUN}
3618 entries in stabs-format debugging information. @code{N_SO} stabs mark
3619 the beginning and ending addresses of compilation units in the text
3620 segment. @code{N_FUN} stabs mark the starts and ends of functions.
3622 @code{SOFUN_ADDRESS_MAYBE_MISSING} means two things:
3626 @code{N_FUN} stabs have an address of zero. Instead, you should find the
3627 addresses where the function starts by taking the function name from
3628 the stab, and then looking that up in the minsyms (the
3629 linker/assembler symbol table). In other words, the stab has the
3630 name, and the linker/assembler symbol table is the only place that carries
3634 @code{N_SO} stabs have an address of zero, too. You just look at the
3635 @code{N_FUN} stabs that appear before and after the @code{N_SO} stab,
3636 and guess the starting and ending addresses of the compilation unit from
3640 @item PCC_SOL_BROKEN
3641 @findex PCC_SOL_BROKEN
3642 (Used only in the Convex target.)
3644 @item PC_IN_SIGTRAMP (@var{pc}, @var{name})
3645 @findex PC_IN_SIGTRAMP
3647 The @dfn{sigtramp} is a routine that the kernel calls (which then calls
3648 the signal handler). On most machines it is a library routine that is
3649 linked into the executable.
3651 This function, given a program counter value in @var{pc} and the
3652 (possibly NULL) name of the function in which that @var{pc} resides,
3653 returns nonzero if the @var{pc} and/or @var{name} show that we are in
3656 @item PC_LOAD_SEGMENT
3657 @findex PC_LOAD_SEGMENT
3658 If defined, print information about the load segment for the program
3659 counter. (Defined only for the RS/6000.)
3663 If the program counter is kept in a register, then define this macro to
3664 be the number (greater than or equal to zero) of that register.
3666 This should only need to be defined if @code{TARGET_READ_PC} and
3667 @code{TARGET_WRITE_PC} are not defined.
3671 The number of the ``next program counter'' register, if defined.
3674 @findex PARM_BOUNDARY
3675 If non-zero, round arguments to a boundary of this many bits before
3676 pushing them on the stack.
3678 @item PROCESS_LINENUMBER_HOOK
3679 @findex PROCESS_LINENUMBER_HOOK
3680 A hook defined for XCOFF reading.
3682 @item PROLOGUE_FIRSTLINE_OVERLAP
3683 @findex PROLOGUE_FIRSTLINE_OVERLAP
3684 (Only used in unsupported Convex configuration.)
3688 If defined, this is the number of the processor status register. (This
3689 definition is only used in generic code when parsing "$ps".)
3691 @item DEPRECATED_POP_FRAME
3692 @findex DEPRECATED_POP_FRAME
3694 If defined, used by @code{frame_pop} to remove a stack frame. This
3695 method has been superseeded by generic code.
3697 @item push_dummy_call (@var{gdbarch}, @var{regcache}, @var{dummy_addr}, @var{nargs}, @var{args}, @var{sp}, @var{struct_return}, @var{struct_addr})
3698 @findex push_dummy_call
3699 @findex DEPRECATED_PUSH_ARGUMENTS.
3700 @anchor{push_dummy_call}
3701 Define this to push the dummy frame's call to the inferior function onto
3702 the stack. In addition to pushing @var{nargs}, the code should push
3703 @var{struct_addr} (when @var{struct_return}), and the return value (in
3704 the call dummy at @var{dummy_addr}).
3706 Returns the updated top-of-stack pointer.
3708 This method replaces @code{DEPRECATED_PUSH_ARGUMENTS}.
3710 @item DEPRECATED_PUSH_DUMMY_FRAME
3711 @findex DEPRECATED_PUSH_DUMMY_FRAME
3712 Used in @samp{call_function_by_hand} to create an artificial stack frame.
3714 @item REGISTER_BYTES
3715 @findex REGISTER_BYTES
3716 The total amount of space needed to store @value{GDBN}'s copy of the machine's
3719 @item REGISTER_NAME(@var{i})
3720 @findex REGISTER_NAME
3721 Return the name of register @var{i} as a string. May return @code{NULL}
3722 or @code{NUL} to indicate that register @var{i} is not valid.
3724 @item REGISTER_NAMES
3725 @findex REGISTER_NAMES
3726 Deprecated in favor of @code{REGISTER_NAME}.
3728 @item REG_STRUCT_HAS_ADDR (@var{gcc_p}, @var{type})
3729 @findex REG_STRUCT_HAS_ADDR
3730 Define this to return 1 if the given type will be passed by pointer
3731 rather than directly.
3733 @item SAVE_DUMMY_FRAME_TOS (@var{sp})
3734 @findex SAVE_DUMMY_FRAME_TOS
3735 @anchor{SAVE_DUMMY_FRAME_TOS} Used in @samp{call_function_by_hand} to
3736 notify the target dependent code of the top-of-stack value that will be
3737 passed to the the inferior code. This is the value of the @code{SP}
3738 after both the dummy frame and space for parameters/results have been
3739 allocated on the stack. @xref{unwind_dummy_id}.
3741 @item SDB_REG_TO_REGNUM
3742 @findex SDB_REG_TO_REGNUM
3743 Define this to convert sdb register numbers into @value{GDBN} regnums. If not
3744 defined, no conversion will be done.
3746 @item SKIP_PERMANENT_BREAKPOINT
3747 @findex SKIP_PERMANENT_BREAKPOINT
3748 Advance the inferior's PC past a permanent breakpoint. @value{GDBN} normally
3749 steps over a breakpoint by removing it, stepping one instruction, and
3750 re-inserting the breakpoint. However, permanent breakpoints are
3751 hardwired into the inferior, and can't be removed, so this strategy
3752 doesn't work. Calling @code{SKIP_PERMANENT_BREAKPOINT} adjusts the processor's
3753 state so that execution will resume just after the breakpoint. This
3754 macro does the right thing even when the breakpoint is in the delay slot
3755 of a branch or jump.
3757 @item SKIP_PROLOGUE (@var{pc})
3758 @findex SKIP_PROLOGUE
3759 A C expression that returns the address of the ``real'' code beyond the
3760 function entry prologue found at @var{pc}.
3762 @item SKIP_TRAMPOLINE_CODE (@var{pc})
3763 @findex SKIP_TRAMPOLINE_CODE
3764 If the target machine has trampoline code that sits between callers and
3765 the functions being called, then define this macro to return a new PC
3766 that is at the start of the real function.
3770 If the stack-pointer is kept in a register, then define this macro to be
3771 the number (greater than or equal to zero) of that register, or -1 if
3772 there is no such register.
3774 @item STAB_REG_TO_REGNUM
3775 @findex STAB_REG_TO_REGNUM
3776 Define this to convert stab register numbers (as gotten from `r'
3777 declarations) into @value{GDBN} regnums. If not defined, no conversion will be
3780 @item STACK_ALIGN (@var{addr})
3781 @anchor{STACK_ALIGN}
3783 Define this to increase @var{addr} so that it meets the alignment
3784 requirements for the processor's stack.
3786 Unlike @ref{frame_align}, this function always adjusts @var{addr}
3789 By default, no stack alignment is performed.
3791 @item STEP_SKIPS_DELAY (@var{addr})
3792 @findex STEP_SKIPS_DELAY
3793 Define this to return true if the address is of an instruction with a
3794 delay slot. If a breakpoint has been placed in the instruction's delay
3795 slot, @value{GDBN} will single-step over that instruction before resuming
3796 normally. Currently only defined for the Mips.
3798 @item STORE_RETURN_VALUE (@var{type}, @var{regcache}, @var{valbuf})
3799 @findex STORE_RETURN_VALUE
3800 A C expression that writes the function return value, found in
3801 @var{valbuf}, into the @var{regcache}. @var{type} is the type of the
3802 value that is to be returned.
3804 @item SUN_FIXED_LBRAC_BUG
3805 @findex SUN_FIXED_LBRAC_BUG
3806 (Used only for Sun-3 and Sun-4 targets.)
3808 @item SYMBOL_RELOADING_DEFAULT
3809 @findex SYMBOL_RELOADING_DEFAULT
3810 The default value of the ``symbol-reloading'' variable. (Never defined in
3813 @item TARGET_CHAR_BIT
3814 @findex TARGET_CHAR_BIT
3815 Number of bits in a char; defaults to 8.
3817 @item TARGET_CHAR_SIGNED
3818 @findex TARGET_CHAR_SIGNED
3819 Non-zero if @code{char} is normally signed on this architecture; zero if
3820 it should be unsigned.
3822 The ISO C standard requires the compiler to treat @code{char} as
3823 equivalent to either @code{signed char} or @code{unsigned char}; any
3824 character in the standard execution set is supposed to be positive.
3825 Most compilers treat @code{char} as signed, but @code{char} is unsigned
3826 on the IBM S/390, RS6000, and PowerPC targets.
3828 @item TARGET_COMPLEX_BIT
3829 @findex TARGET_COMPLEX_BIT
3830 Number of bits in a complex number; defaults to @code{2 * TARGET_FLOAT_BIT}.
3832 At present this macro is not used.
3834 @item TARGET_DOUBLE_BIT
3835 @findex TARGET_DOUBLE_BIT
3836 Number of bits in a double float; defaults to @code{8 * TARGET_CHAR_BIT}.
3838 @item TARGET_DOUBLE_COMPLEX_BIT
3839 @findex TARGET_DOUBLE_COMPLEX_BIT
3840 Number of bits in a double complex; defaults to @code{2 * TARGET_DOUBLE_BIT}.
3842 At present this macro is not used.
3844 @item TARGET_FLOAT_BIT
3845 @findex TARGET_FLOAT_BIT
3846 Number of bits in a float; defaults to @code{4 * TARGET_CHAR_BIT}.
3848 @item TARGET_INT_BIT
3849 @findex TARGET_INT_BIT
3850 Number of bits in an integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3852 @item TARGET_LONG_BIT
3853 @findex TARGET_LONG_BIT
3854 Number of bits in a long integer; defaults to @code{4 * TARGET_CHAR_BIT}.
3856 @item TARGET_LONG_DOUBLE_BIT
3857 @findex TARGET_LONG_DOUBLE_BIT
3858 Number of bits in a long double float;
3859 defaults to @code{2 * TARGET_DOUBLE_BIT}.
3861 @item TARGET_LONG_LONG_BIT
3862 @findex TARGET_LONG_LONG_BIT
3863 Number of bits in a long long integer; defaults to @code{2 * TARGET_LONG_BIT}.
3865 @item TARGET_PTR_BIT
3866 @findex TARGET_PTR_BIT
3867 Number of bits in a pointer; defaults to @code{TARGET_INT_BIT}.
3869 @item TARGET_SHORT_BIT
3870 @findex TARGET_SHORT_BIT
3871 Number of bits in a short integer; defaults to @code{2 * TARGET_CHAR_BIT}.
3873 @item TARGET_READ_PC
3874 @findex TARGET_READ_PC
3875 @itemx TARGET_WRITE_PC (@var{val}, @var{pid})
3876 @findex TARGET_WRITE_PC
3877 @itemx TARGET_READ_SP
3878 @findex TARGET_READ_SP
3879 @itemx TARGET_READ_FP
3880 @findex TARGET_READ_FP
3885 These change the behavior of @code{read_pc}, @code{write_pc},
3886 @code{read_sp} and @code{deprecated_read_fp}. For most targets, these
3887 may be left undefined. @value{GDBN} will call the read and write
3888 register functions with the relevant @code{_REGNUM} argument.
3890 These macros are useful when a target keeps one of these registers in a
3891 hard to get at place; for example, part in a segment register and part
3892 in an ordinary register.
3894 @item TARGET_VIRTUAL_FRAME_POINTER(@var{pc}, @var{regp}, @var{offsetp})
3895 @findex TARGET_VIRTUAL_FRAME_POINTER
3896 Returns a @code{(register, offset)} pair representing the virtual frame
3897 pointer in use at the code address @var{pc}. If virtual frame pointers
3898 are not used, a default definition simply returns
3899 @code{DEPRECATED_FP_REGNUM}, with an offset of zero.
3901 @item TARGET_HAS_HARDWARE_WATCHPOINTS
3902 If non-zero, the target has support for hardware-assisted
3903 watchpoints. @xref{Algorithms, watchpoints}, for more details and
3904 other related macros.
3906 @item TARGET_PRINT_INSN (@var{addr}, @var{info})
3907 @findex TARGET_PRINT_INSN
3908 This is the function used by @value{GDBN} to print an assembly
3909 instruction. It prints the instruction at address @var{addr} in
3910 debugged memory and returns the length of the instruction, in bytes. If
3911 a target doesn't define its own printing routine, it defaults to an
3912 accessor function for the global pointer
3913 @code{deprecated_tm_print_insn}. This usually points to a function in
3914 the @code{opcodes} library (@pxref{Support Libraries, ,Opcodes}).
3915 @var{info} is a structure (of type @code{disassemble_info}) defined in
3916 @file{include/dis-asm.h} used to pass information to the instruction
3919 @item struct frame_id unwind_dummy_id (struct frame_info *@var{frame})
3920 @findex unwind_dummy_id
3921 @anchor{unwind_dummy_id} Given @var{frame} return a @code{struct
3922 frame_id} that uniquely identifies an inferior function call's dummy
3923 frame. The value returned must match the dummy frame stack value
3924 previously saved using @code{SAVE_DUMMY_FRAME_TOS}.
3925 @xref{SAVE_DUMMY_FRAME_TOS}.
3927 @item USE_STRUCT_CONVENTION (@var{gcc_p}, @var{type})
3928 @findex USE_STRUCT_CONVENTION
3929 If defined, this must be an expression that is nonzero if a value of the
3930 given @var{type} being returned from a function must have space
3931 allocated for it on the stack. @var{gcc_p} is true if the function
3932 being considered is known to have been compiled by GCC; this is helpful
3933 for systems where GCC is known to use different calling convention than
3936 @item VALUE_TO_REGISTER(@var{type}, @var{regnum}, @var{from}, @var{to})
3937 @findex VALUE_TO_REGISTER
3938 Convert a value of type @var{type} into the raw contents of register
3940 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
3942 @item VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3943 @findex VARIABLES_INSIDE_BLOCK
3944 For dbx-style debugging information, if the compiler puts variable
3945 declarations inside LBRAC/RBRAC blocks, this should be defined to be
3946 nonzero. @var{desc} is the value of @code{n_desc} from the
3947 @code{N_RBRAC} symbol, and @var{gcc_p} is true if @value{GDBN} has noticed the
3948 presence of either the @code{GCC_COMPILED_SYMBOL} or the
3949 @code{GCC2_COMPILED_SYMBOL}. By default, this is 0.
3951 @item OS9K_VARIABLES_INSIDE_BLOCK (@var{desc}, @var{gcc_p})
3952 @findex OS9K_VARIABLES_INSIDE_BLOCK
3953 Similarly, for OS/9000. Defaults to 1.
3956 Motorola M68K target conditionals.
3960 Define this to be the 4-bit location of the breakpoint trap vector. If
3961 not defined, it will default to @code{0xf}.
3963 @item REMOTE_BPT_VECTOR
3964 Defaults to @code{1}.
3966 @item NAME_OF_MALLOC
3967 @findex NAME_OF_MALLOC
3968 A string containing the name of the function to call in order to
3969 allocate some memory in the inferior. The default value is "malloc".
3973 @section Adding a New Target
3975 @cindex adding a target
3976 The following files add a target to @value{GDBN}:
3980 @item gdb/config/@var{arch}/@var{ttt}.mt
3981 Contains a Makefile fragment specific to this target. Specifies what
3982 object files are needed for target @var{ttt}, by defining
3983 @samp{TDEPFILES=@dots{}} and @samp{TDEPLIBS=@dots{}}. Also specifies
3984 the header file which describes @var{ttt}, by defining @samp{TM_FILE=
3987 You can also define @samp{TM_CFLAGS}, @samp{TM_CLIBS}, @samp{TM_CDEPS},
3988 but these are now deprecated, replaced by autoconf, and may go away in
3989 future versions of @value{GDBN}.
3991 @item gdb/@var{ttt}-tdep.c
3992 Contains any miscellaneous code required for this target machine. On
3993 some machines it doesn't exist at all. Sometimes the macros in
3994 @file{tm-@var{ttt}.h} become very complicated, so they are implemented
3995 as functions here instead, and the macro is simply defined to call the
3996 function. This is vastly preferable, since it is easier to understand
3999 @item gdb/@var{arch}-tdep.c
4000 @itemx gdb/@var{arch}-tdep.h
4001 This often exists to describe the basic layout of the target machine's
4002 processor chip (registers, stack, etc.). If used, it is included by
4003 @file{@var{ttt}-tdep.h}. It can be shared among many targets that use
4006 @item gdb/config/@var{arch}/tm-@var{ttt}.h
4007 (@file{tm.h} is a link to this file, created by @code{configure}). Contains
4008 macro definitions about the target machine's registers, stack frame
4009 format and instructions.
4011 New targets do not need this file and should not create it.
4013 @item gdb/config/@var{arch}/tm-@var{arch}.h
4014 This often exists to describe the basic layout of the target machine's
4015 processor chip (registers, stack, etc.). If used, it is included by
4016 @file{tm-@var{ttt}.h}. It can be shared among many targets that use the
4019 New targets do not need this file and should not create it.
4023 If you are adding a new operating system for an existing CPU chip, add a
4024 @file{config/tm-@var{os}.h} file that describes the operating system
4025 facilities that are unusual (extra symbol table info; the breakpoint
4026 instruction needed; etc.). Then write a @file{@var{arch}/tm-@var{os}.h}
4027 that just @code{#include}s @file{tm-@var{arch}.h} and
4028 @file{config/tm-@var{os}.h}.
4031 @section Converting an existing Target Architecture to Multi-arch
4032 @cindex converting targets to multi-arch
4034 This section describes the current accepted best practice for converting
4035 an existing target architecture to the multi-arch framework.
4037 The process consists of generating, testing, posting and committing a
4038 sequence of patches. Each patch must contain a single change, for
4044 Directly convert a group of functions into macros (the conversion does
4045 not change the behavior of any of the functions).
4048 Replace a non-multi-arch with a multi-arch mechanism (e.g.,
4052 Enable multi-arch level one.
4055 Delete one or more files.
4060 There isn't a size limit on a patch, however, a developer is strongly
4061 encouraged to keep the patch size down.
4063 Since each patch is well defined, and since each change has been tested
4064 and shows no regressions, the patches are considered @emph{fairly}
4065 obvious. Such patches, when submitted by developers listed in the
4066 @file{MAINTAINERS} file, do not need approval. Occasional steps in the
4067 process may be more complicated and less clear. The developer is
4068 expected to use their judgment and is encouraged to seek advice as
4071 @subsection Preparation
4073 The first step is to establish control. Build (with @option{-Werror}
4074 enabled) and test the target so that there is a baseline against which
4075 the debugger can be compared.
4077 At no stage can the test results regress or @value{GDBN} stop compiling
4078 with @option{-Werror}.
4080 @subsection Add the multi-arch initialization code
4082 The objective of this step is to establish the basic multi-arch
4083 framework. It involves
4088 The addition of a @code{@var{arch}_gdbarch_init} function@footnote{The
4089 above is from the original example and uses K&R C. @value{GDBN}
4090 has since converted to ISO C but lets ignore that.} that creates
4093 static struct gdbarch *
4094 d10v_gdbarch_init (info, arches)
4095 struct gdbarch_info info;
4096 struct gdbarch_list *arches;
4098 struct gdbarch *gdbarch;
4099 /* there is only one d10v architecture */
4101 return arches->gdbarch;
4102 gdbarch = gdbarch_alloc (&info, NULL);
4110 A per-architecture dump function to print any architecture specific
4114 mips_dump_tdep (struct gdbarch *current_gdbarch,
4115 struct ui_file *file)
4117 @dots{} code to print architecture specific info @dots{}
4122 A change to @code{_initialize_@var{arch}_tdep} to register this new
4126 _initialize_mips_tdep (void)
4128 gdbarch_register (bfd_arch_mips, mips_gdbarch_init,
4133 Add the macro @code{GDB_MULTI_ARCH}, defined as 0 (zero), to the file@*
4134 @file{config/@var{arch}/tm-@var{arch}.h}.
4138 @subsection Update multi-arch incompatible mechanisms
4140 Some mechanisms do not work with multi-arch. They include:
4143 @item FRAME_FIND_SAVED_REGS
4144 Replaced with @code{DEPRECATED_FRAME_INIT_SAVED_REGS}
4148 At this stage you could also consider converting the macros into
4151 @subsection Prepare for multi-arch level to one
4153 Temporally set @code{GDB_MULTI_ARCH} to @code{GDB_MULTI_ARCH_PARTIAL}
4154 and then build and start @value{GDBN} (the change should not be
4155 committed). @value{GDBN} may not build, and once built, it may die with
4156 an internal error listing the architecture methods that must be
4159 Fix any build problems (patch(es)).
4161 Convert all the architecture methods listed, which are only macros, into
4162 functions (patch(es)).
4164 Update @code{@var{arch}_gdbarch_init} to set all the missing
4165 architecture methods and wrap the corresponding macros in @code{#if
4166 !GDB_MULTI_ARCH} (patch(es)).
4168 @subsection Set multi-arch level one
4170 Change the value of @code{GDB_MULTI_ARCH} to GDB_MULTI_ARCH_PARTIAL (a
4173 Any problems with throwing ``the switch'' should have been fixed
4176 @subsection Convert remaining macros
4178 Suggest converting macros into functions (and setting the corresponding
4179 architecture method) in small batches.
4181 @subsection Set multi-arch level to two
4183 This should go smoothly.
4185 @subsection Delete the TM file
4187 The @file{tm-@var{arch}.h} can be deleted. @file{@var{arch}.mt} and
4188 @file{configure.in} updated.
4191 @node Target Vector Definition
4193 @chapter Target Vector Definition
4194 @cindex target vector
4196 The target vector defines the interface between @value{GDBN}'s
4197 abstract handling of target systems, and the nitty-gritty code that
4198 actually exercises control over a process or a serial port.
4199 @value{GDBN} includes some 30-40 different target vectors; however,
4200 each configuration of @value{GDBN} includes only a few of them.
4202 @section File Targets
4204 Both executables and core files have target vectors.
4206 @section Standard Protocol and Remote Stubs
4208 @value{GDBN}'s file @file{remote.c} talks a serial protocol to code
4209 that runs in the target system. @value{GDBN} provides several sample
4210 @dfn{stubs} that can be integrated into target programs or operating
4211 systems for this purpose; they are named @file{*-stub.c}.
4213 The @value{GDBN} user's manual describes how to put such a stub into
4214 your target code. What follows is a discussion of integrating the
4215 SPARC stub into a complicated operating system (rather than a simple
4216 program), by Stu Grossman, the author of this stub.
4218 The trap handling code in the stub assumes the following upon entry to
4223 %l1 and %l2 contain pc and npc respectively at the time of the trap;
4229 you are in the correct trap window.
4232 As long as your trap handler can guarantee those conditions, then there
4233 is no reason why you shouldn't be able to ``share'' traps with the stub.
4234 The stub has no requirement that it be jumped to directly from the
4235 hardware trap vector. That is why it calls @code{exceptionHandler()},
4236 which is provided by the external environment. For instance, this could
4237 set up the hardware traps to actually execute code which calls the stub
4238 first, and then transfers to its own trap handler.
4240 For the most point, there probably won't be much of an issue with
4241 ``sharing'' traps, as the traps we use are usually not used by the kernel,
4242 and often indicate unrecoverable error conditions. Anyway, this is all
4243 controlled by a table, and is trivial to modify. The most important
4244 trap for us is for @code{ta 1}. Without that, we can't single step or
4245 do breakpoints. Everything else is unnecessary for the proper operation
4246 of the debugger/stub.
4248 From reading the stub, it's probably not obvious how breakpoints work.
4249 They are simply done by deposit/examine operations from @value{GDBN}.
4251 @section ROM Monitor Interface
4253 @section Custom Protocols
4255 @section Transport Layer
4257 @section Builtin Simulator
4260 @node Native Debugging
4262 @chapter Native Debugging
4263 @cindex native debugging
4265 Several files control @value{GDBN}'s configuration for native support:
4269 @item gdb/config/@var{arch}/@var{xyz}.mh
4270 Specifies Makefile fragments needed by a @emph{native} configuration on
4271 machine @var{xyz}. In particular, this lists the required
4272 native-dependent object files, by defining @samp{NATDEPFILES=@dots{}}.
4273 Also specifies the header file which describes native support on
4274 @var{xyz}, by defining @samp{NAT_FILE= nm-@var{xyz}.h}. You can also
4275 define @samp{NAT_CFLAGS}, @samp{NAT_ADD_FILES}, @samp{NAT_CLIBS},
4276 @samp{NAT_CDEPS}, etc.; see @file{Makefile.in}.
4278 @emph{Maintainer's note: The @file{.mh} suffix is because this file
4279 originally contained @file{Makefile} fragments for hosting @value{GDBN}
4280 on machine @var{xyz}. While the file is no longer used for this
4281 purpose, the @file{.mh} suffix remains. Perhaps someone will
4282 eventually rename these fragments so that they have a @file{.mn}
4285 @item gdb/config/@var{arch}/nm-@var{xyz}.h
4286 (@file{nm.h} is a link to this file, created by @code{configure}). Contains C
4287 macro definitions describing the native system environment, such as
4288 child process control and core file support.
4290 @item gdb/@var{xyz}-nat.c
4291 Contains any miscellaneous C code required for this native support of
4292 this machine. On some machines it doesn't exist at all.
4295 There are some ``generic'' versions of routines that can be used by
4296 various systems. These can be customized in various ways by macros
4297 defined in your @file{nm-@var{xyz}.h} file. If these routines work for
4298 the @var{xyz} host, you can just include the generic file's name (with
4299 @samp{.o}, not @samp{.c}) in @code{NATDEPFILES}.
4301 Otherwise, if your machine needs custom support routines, you will need
4302 to write routines that perform the same functions as the generic file.
4303 Put them into @file{@var{xyz}-nat.c}, and put @file{@var{xyz}-nat.o}
4304 into @code{NATDEPFILES}.
4308 This contains the @emph{target_ops vector} that supports Unix child
4309 processes on systems which use ptrace and wait to control the child.
4312 This contains the @emph{target_ops vector} that supports Unix child
4313 processes on systems which use /proc to control the child.
4316 This does the low-level grunge that uses Unix system calls to do a ``fork
4317 and exec'' to start up a child process.
4320 This is the low level interface to inferior processes for systems using
4321 the Unix @code{ptrace} call in a vanilla way.
4324 @section Native core file Support
4325 @cindex native core files
4328 @findex fetch_core_registers
4329 @item core-aout.c::fetch_core_registers()
4330 Support for reading registers out of a core file. This routine calls
4331 @code{register_addr()}, see below. Now that BFD is used to read core
4332 files, virtually all machines should use @code{core-aout.c}, and should
4333 just provide @code{fetch_core_registers} in @code{@var{xyz}-nat.c} (or
4334 @code{REGISTER_U_ADDR} in @code{nm-@var{xyz}.h}).
4336 @item core-aout.c::register_addr()
4337 If your @code{nm-@var{xyz}.h} file defines the macro
4338 @code{REGISTER_U_ADDR(addr, blockend, regno)}, it should be defined to
4339 set @code{addr} to the offset within the @samp{user} struct of @value{GDBN}
4340 register number @code{regno}. @code{blockend} is the offset within the
4341 ``upage'' of @code{u.u_ar0}. If @code{REGISTER_U_ADDR} is defined,
4342 @file{core-aout.c} will define the @code{register_addr()} function and
4343 use the macro in it. If you do not define @code{REGISTER_U_ADDR}, but
4344 you are using the standard @code{fetch_core_registers()}, you will need
4345 to define your own version of @code{register_addr()}, put it into your
4346 @code{@var{xyz}-nat.c} file, and be sure @code{@var{xyz}-nat.o} is in
4347 the @code{NATDEPFILES} list. If you have your own
4348 @code{fetch_core_registers()}, you may not need a separate
4349 @code{register_addr()}. Many custom @code{fetch_core_registers()}
4350 implementations simply locate the registers themselves.@refill
4353 When making @value{GDBN} run native on a new operating system, to make it
4354 possible to debug core files, you will need to either write specific
4355 code for parsing your OS's core files, or customize
4356 @file{bfd/trad-core.c}. First, use whatever @code{#include} files your
4357 machine uses to define the struct of registers that is accessible
4358 (possibly in the u-area) in a core file (rather than
4359 @file{machine/reg.h}), and an include file that defines whatever header
4360 exists on a core file (e.g. the u-area or a @code{struct core}). Then
4361 modify @code{trad_unix_core_file_p} to use these values to set up the
4362 section information for the data segment, stack segment, any other
4363 segments in the core file (perhaps shared library contents or control
4364 information), ``registers'' segment, and if there are two discontiguous
4365 sets of registers (e.g. integer and float), the ``reg2'' segment. This
4366 section information basically delimits areas in the core file in a
4367 standard way, which the section-reading routines in BFD know how to seek
4370 Then back in @value{GDBN}, you need a matching routine called
4371 @code{fetch_core_registers}. If you can use the generic one, it's in
4372 @file{core-aout.c}; if not, it's in your @file{@var{xyz}-nat.c} file.
4373 It will be passed a char pointer to the entire ``registers'' segment,
4374 its length, and a zero; or a char pointer to the entire ``regs2''
4375 segment, its length, and a 2. The routine should suck out the supplied
4376 register values and install them into @value{GDBN}'s ``registers'' array.
4378 If your system uses @file{/proc} to control processes, and uses ELF
4379 format core files, then you may be able to use the same routines for
4380 reading the registers out of processes and out of core files.
4388 @section shared libraries
4390 @section Native Conditionals
4391 @cindex native conditionals
4393 When @value{GDBN} is configured and compiled, various macros are
4394 defined or left undefined, to control compilation when the host and
4395 target systems are the same. These macros should be defined (or left
4396 undefined) in @file{nm-@var{system}.h}.
4400 @findex ATTACH_DETACH
4401 If defined, then @value{GDBN} will include support for the @code{attach} and
4402 @code{detach} commands.
4404 @item CHILD_PREPARE_TO_STORE
4405 @findex CHILD_PREPARE_TO_STORE
4406 If the machine stores all registers at once in the child process, then
4407 define this to ensure that all values are correct. This usually entails
4408 a read from the child.
4410 [Note that this is incorrectly defined in @file{xm-@var{system}.h} files
4413 @item FETCH_INFERIOR_REGISTERS
4414 @findex FETCH_INFERIOR_REGISTERS
4415 Define this if the native-dependent code will provide its own routines
4416 @code{fetch_inferior_registers} and @code{store_inferior_registers} in
4417 @file{@var{host}-nat.c}. If this symbol is @emph{not} defined, and
4418 @file{infptrace.c} is included in this configuration, the default
4419 routines in @file{infptrace.c} are used for these functions.
4421 @item FILES_INFO_HOOK
4422 @findex FILES_INFO_HOOK
4423 (Only defined for Convex.)
4427 This macro is normally defined to be the number of the first floating
4428 point register, if the machine has such registers. As such, it would
4429 appear only in target-specific code. However, @file{/proc} support uses this
4430 to decide whether floats are in use on this target.
4432 @item GET_LONGJMP_TARGET
4433 @findex GET_LONGJMP_TARGET
4434 For most machines, this is a target-dependent parameter. On the
4435 DECstation and the Iris, this is a native-dependent parameter, since
4436 @file{setjmp.h} is needed to define it.
4438 This macro determines the target PC address that @code{longjmp} will jump to,
4439 assuming that we have just stopped at a longjmp breakpoint. It takes a
4440 @code{CORE_ADDR *} as argument, and stores the target PC value through this
4441 pointer. It examines the current state of the machine as needed.
4443 @item I386_USE_GENERIC_WATCHPOINTS
4444 An x86-based machine can define this to use the generic x86 watchpoint
4445 support; see @ref{Algorithms, I386_USE_GENERIC_WATCHPOINTS}.
4448 @findex KERNEL_U_ADDR
4449 Define this to the address of the @code{u} structure (the ``user
4450 struct'', also known as the ``u-page'') in kernel virtual memory. @value{GDBN}
4451 needs to know this so that it can subtract this address from absolute
4452 addresses in the upage, that are obtained via ptrace or from core files.
4453 On systems that don't need this value, set it to zero.
4455 @item KERNEL_U_ADDR_BSD
4456 @findex KERNEL_U_ADDR_BSD
4457 Define this to cause @value{GDBN} to determine the address of @code{u} at
4458 runtime, by using Berkeley-style @code{nlist} on the kernel's image in
4461 @item KERNEL_U_ADDR_HPUX
4462 @findex KERNEL_U_ADDR_HPUX
4463 Define this to cause @value{GDBN} to determine the address of @code{u} at
4464 runtime, by using HP-style @code{nlist} on the kernel's image in the
4467 @item ONE_PROCESS_WRITETEXT
4468 @findex ONE_PROCESS_WRITETEXT
4469 Define this to be able to, when a breakpoint insertion fails, warn the
4470 user that another process may be running with the same executable.
4472 @item PREPARE_TO_PROCEED (@var{select_it})
4473 @findex PREPARE_TO_PROCEED
4474 This (ugly) macro allows a native configuration to customize the way the
4475 @code{proceed} function in @file{infrun.c} deals with switching between
4478 In a multi-threaded task we may select another thread and then continue
4479 or step. But if the old thread was stopped at a breakpoint, it will
4480 immediately cause another breakpoint stop without any execution (i.e. it
4481 will report a breakpoint hit incorrectly). So @value{GDBN} must step over it
4484 If defined, @code{PREPARE_TO_PROCEED} should check the current thread
4485 against the thread that reported the most recent event. If a step-over
4486 is required, it returns TRUE. If @var{select_it} is non-zero, it should
4487 reselect the old thread.
4490 @findex PROC_NAME_FMT
4491 Defines the format for the name of a @file{/proc} device. Should be
4492 defined in @file{nm.h} @emph{only} in order to override the default
4493 definition in @file{procfs.c}.
4496 @findex PTRACE_FP_BUG
4497 See @file{mach386-xdep.c}.
4499 @item PTRACE_ARG3_TYPE
4500 @findex PTRACE_ARG3_TYPE
4501 The type of the third argument to the @code{ptrace} system call, if it
4502 exists and is different from @code{int}.
4504 @item REGISTER_U_ADDR
4505 @findex REGISTER_U_ADDR
4506 Defines the offset of the registers in the ``u area''.
4508 @item SHELL_COMMAND_CONCAT
4509 @findex SHELL_COMMAND_CONCAT
4510 If defined, is a string to prefix on the shell command used to start the
4515 If defined, this is the name of the shell to use to run the inferior.
4516 Defaults to @code{"/bin/sh"}.
4518 @item SOLIB_ADD (@var{filename}, @var{from_tty}, @var{targ}, @var{readsyms})
4520 Define this to expand into an expression that will cause the symbols in
4521 @var{filename} to be added to @value{GDBN}'s symbol table. If
4522 @var{readsyms} is zero symbols are not read but any necessary low level
4523 processing for @var{filename} is still done.
4525 @item SOLIB_CREATE_INFERIOR_HOOK
4526 @findex SOLIB_CREATE_INFERIOR_HOOK
4527 Define this to expand into any shared-library-relocation code that you
4528 want to be run just after the child process has been forked.
4530 @item START_INFERIOR_TRAPS_EXPECTED
4531 @findex START_INFERIOR_TRAPS_EXPECTED
4532 When starting an inferior, @value{GDBN} normally expects to trap
4534 the shell execs, and once when the program itself execs. If the actual
4535 number of traps is something other than 2, then define this macro to
4536 expand into the number expected.
4538 @item SVR4_SHARED_LIBS
4539 @findex SVR4_SHARED_LIBS
4540 Define this to indicate that SVR4-style shared libraries are in use.
4544 This determines whether small routines in @file{*-tdep.c}, which
4545 translate register values between @value{GDBN}'s internal
4546 representation and the @file{/proc} representation, are compiled.
4549 @findex U_REGS_OFFSET
4550 This is the offset of the registers in the upage. It need only be
4551 defined if the generic ptrace register access routines in
4552 @file{infptrace.c} are being used (that is, @file{infptrace.c} is
4553 configured in, and @code{FETCH_INFERIOR_REGISTERS} is not defined). If
4554 the default value from @file{infptrace.c} is good enough, leave it
4557 The default value means that u.u_ar0 @emph{points to} the location of
4558 the registers. I'm guessing that @code{#define U_REGS_OFFSET 0} means
4559 that @code{u.u_ar0} @emph{is} the location of the registers.
4563 See @file{objfiles.c}.
4566 @findex DEBUG_PTRACE
4567 Define this to debug @code{ptrace} calls.
4571 @node Support Libraries
4573 @chapter Support Libraries
4578 BFD provides support for @value{GDBN} in several ways:
4581 @item identifying executable and core files
4582 BFD will identify a variety of file types, including a.out, coff, and
4583 several variants thereof, as well as several kinds of core files.
4585 @item access to sections of files
4586 BFD parses the file headers to determine the names, virtual addresses,
4587 sizes, and file locations of all the various named sections in files
4588 (such as the text section or the data section). @value{GDBN} simply
4589 calls BFD to read or write section @var{x} at byte offset @var{y} for
4592 @item specialized core file support
4593 BFD provides routines to determine the failing command name stored in a
4594 core file, the signal with which the program failed, and whether a core
4595 file matches (i.e.@: could be a core dump of) a particular executable
4598 @item locating the symbol information
4599 @value{GDBN} uses an internal interface of BFD to determine where to find the
4600 symbol information in an executable file or symbol-file. @value{GDBN} itself
4601 handles the reading of symbols, since BFD does not ``understand'' debug
4602 symbols, but @value{GDBN} uses BFD's cached information to find the symbols,
4607 @cindex opcodes library
4609 The opcodes library provides @value{GDBN}'s disassembler. (It's a separate
4610 library because it's also used in binutils, for @file{objdump}).
4619 @cindex regular expressions library
4630 @item SIGN_EXTEND_CHAR
4632 @item SWITCH_ENUM_BUG
4647 This chapter covers topics that are lower-level than the major
4648 algorithms of @value{GDBN}.
4653 Cleanups are a structured way to deal with things that need to be done
4656 When your code does something (e.g., @code{xmalloc} some memory, or
4657 @code{open} a file) that needs to be undone later (e.g., @code{xfree}
4658 the memory or @code{close} the file), it can make a cleanup. The
4659 cleanup will be done at some future point: when the command is finished
4660 and control returns to the top level; when an error occurs and the stack
4661 is unwound; or when your code decides it's time to explicitly perform
4662 cleanups. Alternatively you can elect to discard the cleanups you
4668 @item struct cleanup *@var{old_chain};
4669 Declare a variable which will hold a cleanup chain handle.
4671 @findex make_cleanup
4672 @item @var{old_chain} = make_cleanup (@var{function}, @var{arg});
4673 Make a cleanup which will cause @var{function} to be called with
4674 @var{arg} (a @code{char *}) later. The result, @var{old_chain}, is a
4675 handle that can later be passed to @code{do_cleanups} or
4676 @code{discard_cleanups}. Unless you are going to call
4677 @code{do_cleanups} or @code{discard_cleanups}, you can ignore the result
4678 from @code{make_cleanup}.
4681 @item do_cleanups (@var{old_chain});
4682 Do all cleanups added to the chain since the corresponding
4683 @code{make_cleanup} call was made.
4685 @findex discard_cleanups
4686 @item discard_cleanups (@var{old_chain});
4687 Same as @code{do_cleanups} except that it just removes the cleanups from
4688 the chain and does not call the specified functions.
4691 Cleanups are implemented as a chain. The handle returned by
4692 @code{make_cleanups} includes the cleanup passed to the call and any
4693 later cleanups appended to the chain (but not yet discarded or
4697 make_cleanup (a, 0);
4699 struct cleanup *old = make_cleanup (b, 0);
4707 will call @code{c()} and @code{b()} but will not call @code{a()}. The
4708 cleanup that calls @code{a()} will remain in the cleanup chain, and will
4709 be done later unless otherwise discarded.@refill
4711 Your function should explicitly do or discard the cleanups it creates.
4712 Failing to do this leads to non-deterministic behavior since the caller
4713 will arbitrarily do or discard your functions cleanups. This need leads
4714 to two common cleanup styles.
4716 The first style is try/finally. Before it exits, your code-block calls
4717 @code{do_cleanups} with the old cleanup chain and thus ensures that your
4718 code-block's cleanups are always performed. For instance, the following
4719 code-segment avoids a memory leak problem (even when @code{error} is
4720 called and a forced stack unwind occurs) by ensuring that the
4721 @code{xfree} will always be called:
4724 struct cleanup *old = make_cleanup (null_cleanup, 0);
4725 data = xmalloc (sizeof blah);
4726 make_cleanup (xfree, data);
4731 The second style is try/except. Before it exits, your code-block calls
4732 @code{discard_cleanups} with the old cleanup chain and thus ensures that
4733 any created cleanups are not performed. For instance, the following
4734 code segment, ensures that the file will be closed but only if there is
4738 FILE *file = fopen ("afile", "r");
4739 struct cleanup *old = make_cleanup (close_file, file);
4741 discard_cleanups (old);
4745 Some functions, e.g. @code{fputs_filtered()} or @code{error()}, specify
4746 that they ``should not be called when cleanups are not in place''. This
4747 means that any actions you need to reverse in the case of an error or
4748 interruption must be on the cleanup chain before you call these
4749 functions, since they might never return to your code (they
4750 @samp{longjmp} instead).
4752 @section Per-architecture module data
4753 @cindex per-architecture module data
4754 @cindex multi-arch data
4755 @cindex data-pointer, per-architecture/per-module
4757 The multi-arch framework includes a mechanism for adding module specific
4758 per-architecture data-pointers to the @code{struct gdbarch} architecture
4761 A module registers one or more per-architecture data-pointers using the
4762 function @code{register_gdbarch_data}:
4764 @deftypefun struct gdbarch_data *register_gdbarch_data (gdbarch_data_init_ftype *@var{init}, gdbarch_data_free_ftype *@var{free})
4766 The @var{init} function is used to obtain an initial value for a
4767 per-architecture data-pointer. The function is called, after the
4768 architecture has been created, when the data-pointer is still
4769 uninitialized (@code{NULL}) and its value has been requested via a call
4770 to @code{gdbarch_data}. A data-pointer can also be initialize
4771 explicitly using @code{set_gdbarch_data}.
4773 The @var{free} function is called when a data-pointer needs to be
4774 destroyed. This occurs when either the corresponding @code{struct
4775 gdbarch} object is being destroyed or when @code{set_gdbarch_data} is
4776 overriding a non-@code{NULL} data-pointer value.
4778 The function @code{register_gdbarch_data} returns a @code{struct
4779 gdbarch_data} that is used to identify the data-pointer that was added
4784 A typical module has @code{init} and @code{free} functions of the form:
4787 static struct gdbarch_data *nozel_handle;
4789 nozel_init (struct gdbarch *gdbarch)
4791 struct nozel *data = XMALLOC (struct nozel);
4797 nozel_free (struct gdbarch *gdbarch, void *data)
4803 Since uninitialized (@code{NULL}) data-pointers are initialized
4804 on-demand, an @code{init} function is free to call other modules that
4805 use data-pointers. Those modules data-pointers will be initialized as
4806 needed. Care should be taken to ensure that the @code{init} call graph
4807 does not contain cycles.
4809 The data-pointer is registered with the call:
4813 _initialize_nozel (void)
4815 nozel_handle = register_gdbarch_data (nozel_init, nozel_free);
4819 The per-architecture data-pointer is accessed using the function:
4821 @deftypefun void *gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *@var{data_handle})
4822 Given the architecture @var{arch} and module data handle
4823 @var{data_handle} (returned by @code{register_gdbarch_data}, this
4824 function returns the current value of the per-architecture data-pointer.
4827 The non-@code{NULL} data-pointer returned by @code{gdbarch_data} should
4828 be saved in a local variable and then used directly:
4832 nozel_total (struct gdbarch *gdbarch)
4835 struct nozel *data = gdbarch_data (gdbarch, nozel_handle);
4841 It is also possible to directly initialize the data-pointer using:
4843 @deftypefun void set_gdbarch_data (struct gdbarch *@var{gdbarch}, struct gdbarch_data *handle, void *@var{pointer})
4844 Update the data-pointer corresponding to @var{handle} with the value of
4845 @var{pointer}. If the previous data-pointer value is non-NULL, then it
4846 is freed using data-pointers @var{free} function.
4849 This function is used by modules that require a mechanism for explicitly
4850 setting the per-architecture data-pointer during architecture creation:
4853 /* Called during architecture creation. */
4855 set_gdbarch_nozel (struct gdbarch *gdbarch,
4858 struct nozel *data = XMALLOC (struct nozel);
4860 set_gdbarch_data (gdbarch, nozel_handle, nozel);
4865 /* Default, called when nozel not set by set_gdbarch_nozel(). */
4867 nozel_init (struct gdbarch *gdbarch)
4869 struct nozel *default_nozel = XMALLOC (struc nozel);
4871 return default_nozel;
4877 _initialize_nozel (void)
4879 nozel_handle = register_gdbarch_data (nozel_init, NULL);
4884 Note that an @code{init} function still needs to be registered. It is
4885 used to initialize the data-pointer when the architecture creation phase
4886 fail to set an initial value.
4889 @section Wrapping Output Lines
4890 @cindex line wrap in output
4893 Output that goes through @code{printf_filtered} or @code{fputs_filtered}
4894 or @code{fputs_demangled} needs only to have calls to @code{wrap_here}
4895 added in places that would be good breaking points. The utility
4896 routines will take care of actually wrapping if the line width is
4899 The argument to @code{wrap_here} is an indentation string which is
4900 printed @emph{only} if the line breaks there. This argument is saved
4901 away and used later. It must remain valid until the next call to
4902 @code{wrap_here} or until a newline has been printed through the
4903 @code{*_filtered} functions. Don't pass in a local variable and then
4906 It is usually best to call @code{wrap_here} after printing a comma or
4907 space. If you call it before printing a space, make sure that your
4908 indentation properly accounts for the leading space that will print if
4909 the line wraps there.
4911 Any function or set of functions that produce filtered output must
4912 finish by printing a newline, to flush the wrap buffer, before switching
4913 to unfiltered (@code{printf}) output. Symbol reading routines that
4914 print warnings are a good example.
4916 @section @value{GDBN} Coding Standards
4917 @cindex coding standards
4919 @value{GDBN} follows the GNU coding standards, as described in
4920 @file{etc/standards.texi}. This file is also available for anonymous
4921 FTP from GNU archive sites. @value{GDBN} takes a strict interpretation
4922 of the standard; in general, when the GNU standard recommends a practice
4923 but does not require it, @value{GDBN} requires it.
4925 @value{GDBN} follows an additional set of coding standards specific to
4926 @value{GDBN}, as described in the following sections.
4931 @value{GDBN} assumes an ISO/IEC 9899:1990 (a.k.a.@: ISO C90) compliant
4934 @value{GDBN} does not assume an ISO C or POSIX compliant C library.
4937 @subsection Memory Management
4939 @value{GDBN} does not use the functions @code{malloc}, @code{realloc},
4940 @code{calloc}, @code{free} and @code{asprintf}.
4942 @value{GDBN} uses the functions @code{xmalloc}, @code{xrealloc} and
4943 @code{xcalloc} when allocating memory. Unlike @code{malloc} et.al.@:
4944 these functions do not return when the memory pool is empty. Instead,
4945 they unwind the stack using cleanups. These functions return
4946 @code{NULL} when requested to allocate a chunk of memory of size zero.
4948 @emph{Pragmatics: By using these functions, the need to check every
4949 memory allocation is removed. These functions provide portable
4952 @value{GDBN} does not use the function @code{free}.
4954 @value{GDBN} uses the function @code{xfree} to return memory to the
4955 memory pool. Consistent with ISO-C, this function ignores a request to
4956 free a @code{NULL} pointer.
4958 @emph{Pragmatics: On some systems @code{free} fails when passed a
4959 @code{NULL} pointer.}
4961 @value{GDBN} can use the non-portable function @code{alloca} for the
4962 allocation of small temporary values (such as strings).
4964 @emph{Pragmatics: This function is very non-portable. Some systems
4965 restrict the memory being allocated to no more than a few kilobytes.}
4967 @value{GDBN} uses the string function @code{xstrdup} and the print
4968 function @code{xasprintf}.
4970 @emph{Pragmatics: @code{asprintf} and @code{strdup} can fail. Print
4971 functions such as @code{sprintf} are very prone to buffer overflow
4975 @subsection Compiler Warnings
4976 @cindex compiler warnings
4978 With few exceptions, developers should include the configuration option
4979 @samp{--enable-gdb-build-warnings=,-Werror} when building @value{GDBN}.
4980 The exceptions are listed in the file @file{gdb/MAINTAINERS}.
4982 This option causes @value{GDBN} (when built using GCC) to be compiled
4983 with a carefully selected list of compiler warning flags. Any warnings
4984 from those flags being treated as errors.
4986 The current list of warning flags includes:
4990 Since @value{GDBN} coding standard requires all functions to be declared
4991 using a prototype, the flag has the side effect of ensuring that
4992 prototyped functions are always visible with out resorting to
4993 @samp{-Wstrict-prototypes}.
4996 Such code often appears to work except on instruction set architectures
4997 that use register windows.
5004 Since @value{GDBN} uses the @code{format printf} attribute on all
5005 @code{printf} like functions this checks not just @code{printf} calls
5006 but also calls to functions such as @code{fprintf_unfiltered}.
5009 This warning includes uses of the assignment operator within an
5010 @code{if} statement.
5012 @item -Wpointer-arith
5014 @item -Wuninitialized
5017 @emph{Pragmatics: Due to the way that @value{GDBN} is implemented most
5018 functions have unused parameters. Consequently the warning
5019 @samp{-Wunused-parameter} is precluded from the list. The macro
5020 @code{ATTRIBUTE_UNUSED} is not used as it leads to false negatives ---
5021 it is not an error to have @code{ATTRIBUTE_UNUSED} on a parameter that
5022 is being used. The options @samp{-Wall} and @samp{-Wunused} are also
5023 precluded because they both include @samp{-Wunused-parameter}.}
5025 @emph{Pragmatics: @value{GDBN} has not simply accepted the warnings
5026 enabled by @samp{-Wall -Werror -W...}. Instead it is selecting warnings
5027 when and where their benefits can be demonstrated.}
5029 @subsection Formatting
5031 @cindex source code formatting
5032 The standard GNU recommendations for formatting must be followed
5035 A function declaration should not have its name in column zero. A
5036 function definition should have its name in column zero.
5040 static void foo (void);
5048 @emph{Pragmatics: This simplifies scripting. Function definitions can
5049 be found using @samp{^function-name}.}
5051 There must be a space between a function or macro name and the opening
5052 parenthesis of its argument list (except for macro definitions, as
5053 required by C). There must not be a space after an open paren/bracket
5054 or before a close paren/bracket.
5056 While additional whitespace is generally helpful for reading, do not use
5057 more than one blank line to separate blocks, and avoid adding whitespace
5058 after the end of a program line (as of 1/99, some 600 lines had
5059 whitespace after the semicolon). Excess whitespace causes difficulties
5060 for @code{diff} and @code{patch} utilities.
5062 Pointers are declared using the traditional K&R C style:
5076 @subsection Comments
5078 @cindex comment formatting
5079 The standard GNU requirements on comments must be followed strictly.
5081 Block comments must appear in the following form, with no @code{/*}- or
5082 @code{*/}-only lines, and no leading @code{*}:
5085 /* Wait for control to return from inferior to debugger. If inferior
5086 gets a signal, we may decide to start it up again instead of
5087 returning. That is why there is a loop in this function. When
5088 this function actually returns it means the inferior should be left
5089 stopped and @value{GDBN} should read more commands. */
5092 (Note that this format is encouraged by Emacs; tabbing for a multi-line
5093 comment works correctly, and @kbd{M-q} fills the block consistently.)
5095 Put a blank line between the block comments preceding function or
5096 variable definitions, and the definition itself.
5098 In general, put function-body comments on lines by themselves, rather
5099 than trying to fit them into the 20 characters left at the end of a
5100 line, since either the comment or the code will inevitably get longer
5101 than will fit, and then somebody will have to move it anyhow.
5105 @cindex C data types
5106 Code must not depend on the sizes of C data types, the format of the
5107 host's floating point numbers, the alignment of anything, or the order
5108 of evaluation of expressions.
5110 @cindex function usage
5111 Use functions freely. There are only a handful of compute-bound areas
5112 in @value{GDBN} that might be affected by the overhead of a function
5113 call, mainly in symbol reading. Most of @value{GDBN}'s performance is
5114 limited by the target interface (whether serial line or system call).
5116 However, use functions with moderation. A thousand one-line functions
5117 are just as hard to understand as a single thousand-line function.
5119 @emph{Macros are bad, M'kay.}
5120 (But if you have to use a macro, make sure that the macro arguments are
5121 protected with parentheses.)
5125 Declarations like @samp{struct foo *} should be used in preference to
5126 declarations like @samp{typedef struct foo @{ @dots{} @} *foo_ptr}.
5129 @subsection Function Prototypes
5130 @cindex function prototypes
5132 Prototypes must be used when both @emph{declaring} and @emph{defining}
5133 a function. Prototypes for @value{GDBN} functions must include both the
5134 argument type and name, with the name matching that used in the actual
5135 function definition.
5137 All external functions should have a declaration in a header file that
5138 callers include, except for @code{_initialize_*} functions, which must
5139 be external so that @file{init.c} construction works, but shouldn't be
5140 visible to random source files.
5142 Where a source file needs a forward declaration of a static function,
5143 that declaration must appear in a block near the top of the source file.
5146 @subsection Internal Error Recovery
5148 During its execution, @value{GDBN} can encounter two types of errors.
5149 User errors and internal errors. User errors include not only a user
5150 entering an incorrect command but also problems arising from corrupt
5151 object files and system errors when interacting with the target.
5152 Internal errors include situations where @value{GDBN} has detected, at
5153 run time, a corrupt or erroneous situation.
5155 When reporting an internal error, @value{GDBN} uses
5156 @code{internal_error} and @code{gdb_assert}.
5158 @value{GDBN} must not call @code{abort} or @code{assert}.
5160 @emph{Pragmatics: There is no @code{internal_warning} function. Either
5161 the code detected a user error, recovered from it and issued a
5162 @code{warning} or the code failed to correctly recover from the user
5163 error and issued an @code{internal_error}.}
5165 @subsection File Names
5167 Any file used when building the core of @value{GDBN} must be in lower
5168 case. Any file used when building the core of @value{GDBN} must be 8.3
5169 unique. These requirements apply to both source and generated files.
5171 @emph{Pragmatics: The core of @value{GDBN} must be buildable on many
5172 platforms including DJGPP and MacOS/HFS. Every time an unfriendly file
5173 is introduced to the build process both @file{Makefile.in} and
5174 @file{configure.in} need to be modified accordingly. Compare the
5175 convoluted conversion process needed to transform @file{COPYING} into
5176 @file{copying.c} with the conversion needed to transform
5177 @file{version.in} into @file{version.c}.}
5179 Any file non 8.3 compliant file (that is not used when building the core
5180 of @value{GDBN}) must be added to @file{gdb/config/djgpp/fnchange.lst}.
5182 @emph{Pragmatics: This is clearly a compromise.}
5184 When @value{GDBN} has a local version of a system header file (ex
5185 @file{string.h}) the file name based on the POSIX header prefixed with
5186 @file{gdb_} (@file{gdb_string.h}).
5188 For other files @samp{-} is used as the separator.
5191 @subsection Include Files
5193 A @file{.c} file should include @file{defs.h} first.
5195 A @file{.c} file should directly include the @code{.h} file of every
5196 declaration and/or definition it directly refers to. It cannot rely on
5199 A @file{.h} file should directly include the @code{.h} file of every
5200 declaration and/or definition it directly refers to. It cannot rely on
5201 indirect inclusion. Exception: The file @file{defs.h} does not need to
5202 be directly included.
5204 An external declaration should only appear in one include file.
5206 An external declaration should never appear in a @code{.c} file.
5207 Exception: a declaration for the @code{_initialize} function that
5208 pacifies @option{-Wmissing-declaration}.
5210 A @code{typedef} definition should only appear in one include file.
5212 An opaque @code{struct} declaration can appear in multiple @file{.h}
5213 files. Where possible, a @file{.h} file should use an opaque
5214 @code{struct} declaration instead of an include.
5216 All @file{.h} files should be wrapped in:
5219 #ifndef INCLUDE_FILE_NAME_H
5220 #define INCLUDE_FILE_NAME_H
5226 @subsection Clean Design and Portable Implementation
5229 In addition to getting the syntax right, there's the little question of
5230 semantics. Some things are done in certain ways in @value{GDBN} because long
5231 experience has shown that the more obvious ways caused various kinds of
5234 @cindex assumptions about targets
5235 You can't assume the byte order of anything that comes from a target
5236 (including @var{value}s, object files, and instructions). Such things
5237 must be byte-swapped using @code{SWAP_TARGET_AND_HOST} in
5238 @value{GDBN}, or one of the swap routines defined in @file{bfd.h},
5239 such as @code{bfd_get_32}.
5241 You can't assume that you know what interface is being used to talk to
5242 the target system. All references to the target must go through the
5243 current @code{target_ops} vector.
5245 You can't assume that the host and target machines are the same machine
5246 (except in the ``native'' support modules). In particular, you can't
5247 assume that the target machine's header files will be available on the
5248 host machine. Target code must bring along its own header files --
5249 written from scratch or explicitly donated by their owner, to avoid
5253 Insertion of new @code{#ifdef}'s will be frowned upon. It's much better
5254 to write the code portably than to conditionalize it for various
5257 @cindex system dependencies
5258 New @code{#ifdef}'s which test for specific compilers or manufacturers
5259 or operating systems are unacceptable. All @code{#ifdef}'s should test
5260 for features. The information about which configurations contain which
5261 features should be segregated into the configuration files. Experience
5262 has proven far too often that a feature unique to one particular system
5263 often creeps into other systems; and that a conditional based on some
5264 predefined macro for your current system will become worthless over
5265 time, as new versions of your system come out that behave differently
5266 with regard to this feature.
5268 Adding code that handles specific architectures, operating systems,
5269 target interfaces, or hosts, is not acceptable in generic code.
5271 @cindex portable file name handling
5272 @cindex file names, portability
5273 One particularly notorious area where system dependencies tend to
5274 creep in is handling of file names. The mainline @value{GDBN} code
5275 assumes Posix semantics of file names: absolute file names begin with
5276 a forward slash @file{/}, slashes are used to separate leading
5277 directories, case-sensitive file names. These assumptions are not
5278 necessarily true on non-Posix systems such as MS-Windows. To avoid
5279 system-dependent code where you need to take apart or construct a file
5280 name, use the following portable macros:
5283 @findex HAVE_DOS_BASED_FILE_SYSTEM
5284 @item HAVE_DOS_BASED_FILE_SYSTEM
5285 This preprocessing symbol is defined to a non-zero value on hosts
5286 whose filesystems belong to the MS-DOS/MS-Windows family. Use this
5287 symbol to write conditional code which should only be compiled for
5290 @findex IS_DIR_SEPARATOR
5291 @item IS_DIR_SEPARATOR (@var{c})
5292 Evaluates to a non-zero value if @var{c} is a directory separator
5293 character. On Unix and GNU/Linux systems, only a slash @file{/} is
5294 such a character, but on Windows, both @file{/} and @file{\} will
5297 @findex IS_ABSOLUTE_PATH
5298 @item IS_ABSOLUTE_PATH (@var{file})
5299 Evaluates to a non-zero value if @var{file} is an absolute file name.
5300 For Unix and GNU/Linux hosts, a name which begins with a slash
5301 @file{/} is absolute. On DOS and Windows, @file{d:/foo} and
5302 @file{x:\bar} are also absolute file names.
5304 @findex FILENAME_CMP
5305 @item FILENAME_CMP (@var{f1}, @var{f2})
5306 Calls a function which compares file names @var{f1} and @var{f2} as
5307 appropriate for the underlying host filesystem. For Posix systems,
5308 this simply calls @code{strcmp}; on case-insensitive filesystems it
5309 will call @code{strcasecmp} instead.
5311 @findex DIRNAME_SEPARATOR
5312 @item DIRNAME_SEPARATOR
5313 Evaluates to a character which separates directories in
5314 @code{PATH}-style lists, typically held in environment variables.
5315 This character is @samp{:} on Unix, @samp{;} on DOS and Windows.
5317 @findex SLASH_STRING
5319 This evaluates to a constant string you should use to produce an
5320 absolute filename from leading directories and the file's basename.
5321 @code{SLASH_STRING} is @code{"/"} on most systems, but might be
5322 @code{"\\"} for some Windows-based ports.
5325 In addition to using these macros, be sure to use portable library
5326 functions whenever possible. For example, to extract a directory or a
5327 basename part from a file name, use the @code{dirname} and
5328 @code{basename} library functions (available in @code{libiberty} for
5329 platforms which don't provide them), instead of searching for a slash
5330 with @code{strrchr}.
5332 Another way to generalize @value{GDBN} along a particular interface is with an
5333 attribute struct. For example, @value{GDBN} has been generalized to handle
5334 multiple kinds of remote interfaces---not by @code{#ifdef}s everywhere, but
5335 by defining the @code{target_ops} structure and having a current target (as
5336 well as a stack of targets below it, for memory references). Whenever
5337 something needs to be done that depends on which remote interface we are
5338 using, a flag in the current target_ops structure is tested (e.g.,
5339 @code{target_has_stack}), or a function is called through a pointer in the
5340 current target_ops structure. In this way, when a new remote interface
5341 is added, only one module needs to be touched---the one that actually
5342 implements the new remote interface. Other examples of
5343 attribute-structs are BFD access to multiple kinds of object file
5344 formats, or @value{GDBN}'s access to multiple source languages.
5346 Please avoid duplicating code. For example, in @value{GDBN} 3.x all
5347 the code interfacing between @code{ptrace} and the rest of
5348 @value{GDBN} was duplicated in @file{*-dep.c}, and so changing
5349 something was very painful. In @value{GDBN} 4.x, these have all been
5350 consolidated into @file{infptrace.c}. @file{infptrace.c} can deal
5351 with variations between systems the same way any system-independent
5352 file would (hooks, @code{#if defined}, etc.), and machines which are
5353 radically different don't need to use @file{infptrace.c} at all.
5355 All debugging code must be controllable using the @samp{set debug
5356 @var{module}} command. Do not use @code{printf} to print trace
5357 messages. Use @code{fprintf_unfiltered(gdb_stdlog, ...}. Do not use
5358 @code{#ifdef DEBUG}.
5363 @chapter Porting @value{GDBN}
5364 @cindex porting to new machines
5366 Most of the work in making @value{GDBN} compile on a new machine is in
5367 specifying the configuration of the machine. This is done in a
5368 dizzying variety of header files and configuration scripts, which we
5369 hope to make more sensible soon. Let's say your new host is called an
5370 @var{xyz} (e.g., @samp{sun4}), and its full three-part configuration
5371 name is @code{@var{arch}-@var{xvend}-@var{xos}} (e.g.,
5372 @samp{sparc-sun-sunos4}). In particular:
5376 In the top level directory, edit @file{config.sub} and add @var{arch},
5377 @var{xvend}, and @var{xos} to the lists of supported architectures,
5378 vendors, and operating systems near the bottom of the file. Also, add
5379 @var{xyz} as an alias that maps to
5380 @code{@var{arch}-@var{xvend}-@var{xos}}. You can test your changes by
5384 ./config.sub @var{xyz}
5391 ./config.sub @code{@var{arch}-@var{xvend}-@var{xos}}
5395 which should both respond with @code{@var{arch}-@var{xvend}-@var{xos}}
5396 and no error messages.
5399 You need to port BFD, if that hasn't been done already. Porting BFD is
5400 beyond the scope of this manual.
5403 To configure @value{GDBN} itself, edit @file{gdb/configure.host} to recognize
5404 your system and set @code{gdb_host} to @var{xyz}, and (unless your
5405 desired target is already available) also edit @file{gdb/configure.tgt},
5406 setting @code{gdb_target} to something appropriate (for instance,
5409 @emph{Maintainer's note: Work in progress. The file
5410 @file{gdb/configure.host} originally needed to be modified when either a
5411 new native target or a new host machine was being added to @value{GDBN}.
5412 Recent changes have removed this requirement. The file now only needs
5413 to be modified when adding a new native configuration. This will likely
5414 changed again in the future.}
5417 Finally, you'll need to specify and define @value{GDBN}'s host-, native-, and
5418 target-dependent @file{.h} and @file{.c} files used for your
5424 @chapter Releasing @value{GDBN}
5425 @cindex making a new release of gdb
5427 @section Versions and Branches
5429 @subsection Version Identifiers
5431 @value{GDBN}'s version is determined by the file @file{gdb/version.in}.
5433 @value{GDBN}'s mainline uses ISO dates to differentiate between
5434 versions. The CVS repository uses @var{YYYY}-@var{MM}-@var{DD}-cvs
5435 while the corresponding snapshot uses @var{YYYYMMDD}.
5437 @value{GDBN}'s release branch uses a slightly more complicated scheme.
5438 When the branch is first cut, the mainline version identifier is
5439 prefixed with the @var{major}.@var{minor} from of the previous release
5440 series but with .90 appended. As draft releases are drawn from the
5441 branch, the minor minor number (.90) is incremented. Once the first
5442 release (@var{M}.@var{N}) has been made, the version prefix is updated
5443 to @var{M}.@var{N}.0.90 (dot zero, dot ninety). Follow on releases have
5444 an incremented minor minor version number (.0).
5446 Using 5.1 (previous) and 5.2 (current), the example below illustrates a
5447 typical sequence of version identifiers:
5451 final release from previous branch
5452 @item 2002-03-03-cvs
5453 main-line the day the branch is cut
5454 @item 5.1.90-2002-03-03-cvs
5455 corresponding branch version
5457 first draft release candidate
5458 @item 5.1.91-2002-03-17-cvs
5459 updated branch version
5461 second draft release candidate
5462 @item 5.1.92-2002-03-31-cvs
5463 updated branch version
5465 final release candidate (see below)
5468 @item 5.2.0.90-2002-04-07-cvs
5469 updated CVS branch version
5471 second official release
5478 Minor minor minor draft release candidates such as 5.2.0.91 have been
5479 omitted from the example. Such release candidates are, typically, never
5482 For 5.1.93 the bziped tar ball @file{gdb-5.1.93.tar.bz2} is just the
5483 official @file{gdb-5.2.tar} renamed and compressed.
5486 To avoid version conflicts, vendors are expected to modify the file
5487 @file{gdb/version.in} to include a vendor unique alphabetic identifier
5488 (an official @value{GDBN} release never uses alphabetic characters in
5489 its version identifer).
5491 Since @value{GDBN} does not make minor minor minor releases (e.g.,
5492 5.1.0.1) the conflict between that and a minor minor draft release
5493 identifier (e.g., 5.1.0.90) is avoided.
5496 @subsection Branches
5498 @value{GDBN} draws a release series (5.2, 5.2.1, @dots{}) from a single
5499 release branch (gdb_5_2-branch). Since minor minor minor releases
5500 (5.1.0.1) are not made, the need to branch the release branch is avoided
5501 (it also turns out that the effort required for such a a branch and
5502 release is significantly greater than the effort needed to create a new
5503 release from the head of the release branch).
5505 Releases 5.0 and 5.1 used branch and release tags of the form:
5508 gdb_N_M-YYYY-MM-DD-branchpoint
5509 gdb_N_M-YYYY-MM-DD-branch
5510 gdb_M_N-YYYY-MM-DD-release
5513 Release 5.2 is trialing the branch and release tags:
5516 gdb_N_M-YYYY-MM-DD-branchpoint
5518 gdb_M_N-YYYY-MM-DD-release
5521 @emph{Pragmatics: The branchpoint and release tags need to identify when
5522 a branch and release are made. The branch tag, denoting the head of the
5523 branch, does not have this criteria.}
5526 @section Branch Commit Policy
5528 The branch commit policy is pretty slack. @value{GDBN} releases 5.0,
5529 5.1 and 5.2 all used the below:
5533 The @file{gdb/MAINTAINERS} file still holds.
5535 Don't fix something on the branch unless/until it is also fixed in the
5536 trunk. If this isn't possible, mentioning it in the @file{gdb/PROBLEMS}
5537 file is better than committing a hack.
5539 When considering a patch for the branch, suggested criteria include:
5540 Does it fix a build? Does it fix the sequence @kbd{break main; run}
5541 when debugging a static binary?
5543 The further a change is from the core of @value{GDBN}, the less likely
5544 the change will worry anyone (e.g., target specific code).
5546 Only post a proposal to change the core of @value{GDBN} after you've
5547 sent individual bribes to all the people listed in the
5548 @file{MAINTAINERS} file @t{;-)}
5551 @emph{Pragmatics: Provided updates are restricted to non-core
5552 functionality there is little chance that a broken change will be fatal.
5553 This means that changes such as adding a new architectures or (within
5554 reason) support for a new host are considered acceptable.}
5557 @section Obsoleting code
5559 Before anything else, poke the other developers (and around the source
5560 code) to see if there is anything that can be removed from @value{GDBN}
5561 (an old target, an unused file).
5563 Obsolete code is identified by adding an @code{OBSOLETE} prefix to every
5564 line. Doing this means that it is easy to identify something that has
5565 been obsoleted when greping through the sources.
5567 The process is done in stages --- this is mainly to ensure that the
5568 wider @value{GDBN} community has a reasonable opportunity to respond.
5569 Remember, everything on the Internet takes a week.
5573 Post the proposal on @email{gdb@@sources.redhat.com, the GDB mailing
5574 list} Creating a bug report to track the task's state, is also highly
5579 Post the proposal on @email{gdb-announce@@sources.redhat.com, the GDB
5580 Announcement mailing list}.
5584 Go through and edit all relevant files and lines so that they are
5585 prefixed with the word @code{OBSOLETE}.
5587 Wait until the next GDB version, containing this obsolete code, has been
5590 Remove the obsolete code.
5594 @emph{Maintainer note: While removing old code is regrettable it is
5595 hopefully better for @value{GDBN}'s long term development. Firstly it
5596 helps the developers by removing code that is either no longer relevant
5597 or simply wrong. Secondly since it removes any history associated with
5598 the file (effectively clearing the slate) the developer has a much freer
5599 hand when it comes to fixing broken files.}
5603 @section Before the Branch
5605 The most important objective at this stage is to find and fix simple
5606 changes that become a pain to track once the branch is created. For
5607 instance, configuration problems that stop @value{GDBN} from even
5608 building. If you can't get the problem fixed, document it in the
5609 @file{gdb/PROBLEMS} file.
5611 @subheading Prompt for @file{gdb/NEWS}
5613 People always forget. Send a post reminding them but also if you know
5614 something interesting happened add it yourself. The @code{schedule}
5615 script will mention this in its e-mail.
5617 @subheading Review @file{gdb/README}
5619 Grab one of the nightly snapshots and then walk through the
5620 @file{gdb/README} looking for anything that can be improved. The
5621 @code{schedule} script will mention this in its e-mail.
5623 @subheading Refresh any imported files.
5625 A number of files are taken from external repositories. They include:
5629 @file{texinfo/texinfo.tex}
5631 @file{config.guess} et.@: al.@: (see the top-level @file{MAINTAINERS}
5634 @file{etc/standards.texi}, @file{etc/make-stds.texi}
5637 @subheading Check the ARI
5639 @uref{http://sources.redhat.com/gdb/ari,,A.R.I.} is an @code{awk} script
5640 (Awk Regression Index ;-) that checks for a number of errors and coding
5641 conventions. The checks include things like using @code{malloc} instead
5642 of @code{xmalloc} and file naming problems. There shouldn't be any
5645 @subsection Review the bug data base
5647 Close anything obviously fixed.
5649 @subsection Check all cross targets build
5651 The targets are listed in @file{gdb/MAINTAINERS}.
5654 @section Cut the Branch
5656 @subheading Create the branch
5661 $ V=`echo $v | sed 's/\./_/g'`
5662 $ D=`date -u +%Y-%m-%d`
5665 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5666 -D $D-gmt gdb_$V-$D-branchpoint insight+dejagnu
5667 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag
5668 -D 2002-03-03-gmt gdb_5_2-2002-03-03-branchpoint insight+dejagnu
5671 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5672 -b -r gdb_$V-$D-branchpoint gdb_$V-branch insight+dejagnu
5673 cvs -f -d :ext:sources.redhat.com:/cvs/src rtag \
5674 -b -r gdb_5_2-2002-03-03-branchpoint gdb_5_2-branch insight+dejagnu
5682 by using @kbd{-D YYYY-MM-DD-gmt} the branch is forced to an exact
5685 the trunk is first taged so that the branch point can easily be found
5687 Insight (which includes GDB) and dejagnu are all tagged at the same time
5689 @file{version.in} gets bumped to avoid version number conflicts
5691 the reading of @file{.cvsrc} is disabled using @file{-f}
5694 @subheading Update @file{version.in}
5699 $ V=`echo $v | sed 's/\./_/g'`
5703 $ echo cvs -f -d :ext:sources.redhat.com:/cvs/src co \
5704 -r gdb_$V-branch src/gdb/version.in
5705 cvs -f -d :ext:sources.redhat.com:/cvs/src co
5706 -r gdb_5_2-branch src/gdb/version.in
5708 U src/gdb/version.in
5710 $ echo $u.90-0000-00-00-cvs > version.in
5712 5.1.90-0000-00-00-cvs
5713 $ cvs -f commit version.in
5718 @file{0000-00-00} is used as a date to pump prime the version.in update
5721 @file{.90} and the previous branch version are used as fairly arbitrary
5722 initial branch version number
5726 @subheading Update the web and news pages
5730 @subheading Tweak cron to track the new branch
5732 The file @file{gdbadmin/cron/crontab} contains gdbadmin's cron table.
5733 This file needs to be updated so that:
5737 a daily timestamp is added to the file @file{version.in}
5739 the new branch is included in the snapshot process
5743 See the file @file{gdbadmin/cron/README} for how to install the updated
5746 The file @file{gdbadmin/ss/README} should also be reviewed to reflect
5747 any changes. That file is copied to both the branch/ and current/
5748 snapshot directories.
5751 @subheading Update the NEWS and README files
5753 The @file{NEWS} file needs to be updated so that on the branch it refers
5754 to @emph{changes in the current release} while on the trunk it also
5755 refers to @emph{changes since the current release}.
5757 The @file{README} file needs to be updated so that it refers to the
5760 @subheading Post the branch info
5762 Send an announcement to the mailing lists:
5766 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
5768 @email{gdb@@sources.redhat.com, GDB Discsussion mailing list} and
5769 @email{gdb-testers@@sources.redhat.com, GDB Discsussion mailing list}
5772 @emph{Pragmatics: The branch creation is sent to the announce list to
5773 ensure that people people not subscribed to the higher volume discussion
5776 The announcement should include:
5782 how to check out the branch using CVS
5784 the date/number of weeks until the release
5786 the branch commit policy
5790 @section Stabilize the branch
5792 Something goes here.
5794 @section Create a Release
5796 The process of creating and then making available a release is broken
5797 down into a number of stages. The first part addresses the technical
5798 process of creating a releasable tar ball. The later stages address the
5799 process of releasing that tar ball.
5801 When making a release candidate just the first section is needed.
5803 @subsection Create a release candidate
5805 The objective at this stage is to create a set of tar balls that can be
5806 made available as a formal release (or as a less formal release
5809 @subsubheading Freeze the branch
5811 Send out an e-mail notifying everyone that the branch is frozen to
5812 @email{gdb-patches@@sources.redhat.com}.
5814 @subsubheading Establish a few defaults.
5819 $ t=/sourceware/snapshot-tmp/gdbadmin-tmp
5821 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5825 /sourceware/snapshot-tmp/gdbadmin-tmp/gdb_5_2-branch/5.2
5827 /home/gdbadmin/bin/autoconf
5836 Check the @code{autoconf} version carefully. You want to be using the
5837 version taken from the @file{binutils} snapshot directory, which can be
5838 found at @uref{ftp://sources.redhat.com/pub/binutils/}. It is very
5839 unlikely that a system installed version of @code{autoconf} (e.g.,
5840 @file{/usr/bin/autoconf}) is correct.
5843 @subsubheading Check out the relevant modules:
5846 $ for m in gdb insight dejagnu
5848 ( mkdir -p $m && cd $m && cvs -q -f -d /cvs/src co -P -r $b $m )
5858 The reading of @file{.cvsrc} is disabled (@file{-f}) so that there isn't
5859 any confusion between what is written here and what your local
5860 @code{cvs} really does.
5863 @subsubheading Update relevant files.
5869 Major releases get their comments added as part of the mainline. Minor
5870 releases should probably mention any significant bugs that were fixed.
5872 Don't forget to include the @file{ChangeLog} entry.
5875 $ emacs gdb/src/gdb/NEWS
5880 $ cp gdb/src/gdb/NEWS insight/src/gdb/NEWS
5881 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5886 You'll need to update:
5898 $ emacs gdb/src/gdb/README
5903 $ cp gdb/src/gdb/README insight/src/gdb/README
5904 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5907 @emph{Maintainer note: Hopefully the @file{README} file was reviewed
5908 before the initial branch was cut so just a simple substitute is needed
5911 @emph{Maintainer note: Other projects generate @file{README} and
5912 @file{INSTALL} from the core documentation. This might be worth
5915 @item gdb/version.in
5918 $ echo $v > gdb/src/gdb/version.in
5919 $ cat gdb/src/gdb/version.in
5921 $ emacs gdb/src/gdb/version.in
5924 ... Bump to version ...
5926 $ cp gdb/src/gdb/version.in insight/src/gdb/version.in
5927 $ cp gdb/src/gdb/ChangeLog insight/src/gdb/ChangeLog
5930 @item dejagnu/src/dejagnu/configure.in
5932 Dejagnu is more complicated. The version number is a parameter to
5933 @code{AM_INIT_AUTOMAKE}. Tweak it to read something like gdb-5.1.91.
5935 Don't forget to re-generate @file{configure}.
5937 Don't forget to include a @file{ChangeLog} entry.
5940 $ emacs dejagnu/src/dejagnu/configure.in
5945 $ ( cd dejagnu/src/dejagnu && autoconf )
5950 @subsubheading Do the dirty work
5952 This is identical to the process used to create the daily snapshot.
5955 $ for m in gdb insight
5957 ( cd $m/src && gmake -f src-release $m.tar )
5959 $ ( m=dejagnu; cd $m/src && gmake -f src-release $m.tar.bz2 )
5962 If the top level source directory does not have @file{src-release}
5963 (@value{GDBN} version 5.3.1 or earlier), try these commands instead:
5966 $ for m in gdb insight
5968 ( cd $m/src && gmake -f Makefile.in $m.tar )
5970 $ ( m=dejagnu; cd $m/src && gmake -f Makefile.in $m.tar.bz2 )
5973 @subsubheading Check the source files
5975 You're looking for files that have mysteriously disappeared.
5976 @kbd{distclean} has the habit of deleting files it shouldn't. Watch out
5977 for the @file{version.in} update @kbd{cronjob}.
5980 $ ( cd gdb/src && cvs -f -q -n update )
5984 @dots{} lots of generated files @dots{}
5989 @dots{} lots of generated files @dots{}
5994 @emph{Don't worry about the @file{gdb.info-??} or
5995 @file{gdb/p-exp.tab.c}. They were generated (and yes @file{gdb.info-1}
5996 was also generated only something strange with CVS means that they
5997 didn't get supressed). Fixing it would be nice though.}
5999 @subsubheading Create compressed versions of the release
6005 dejagnu/ dejagnu-gdb-5.2.tar.bz2 gdb/ gdb-5.2.tar insight/ insight-5.2.tar
6006 $ for m in gdb insight
6008 bzip2 -v -9 -c $m-$v.tar > $m-$v.tar.bz2
6009 gzip -v -9 -c $m-$v.tar > $m-$v.tar.gz
6019 A pipe such as @kbd{bunzip2 < xxx.bz2 | gzip -9 > xxx.gz} is not since,
6020 in that mode, @code{gzip} does not know the name of the file and, hence,
6021 can not include it in the compressed file. This is also why the release
6022 process runs @code{tar} and @code{bzip2} as separate passes.
6025 @subsection Sanity check the tar ball
6027 Pick a popular machine (Solaris/PPC?) and try the build on that.
6030 $ bunzip2 < gdb-5.2.tar.bz2 | tar xpf -
6035 $ ./gdb/gdb ./gdb/gdb
6039 Breakpoint 1 at 0x80732bc: file main.c, line 734.
6041 Starting program: /tmp/gdb-5.2/gdb/gdb
6043 Breakpoint 1, main (argc=1, argv=0xbffff8b4) at main.c:734
6044 734 catch_errors (captured_main, &args, "", RETURN_MASK_ALL);
6046 $1 = @{argc = 136426532, argv = 0x821b7f0@}
6050 @subsection Make a release candidate available
6052 If this is a release candidate then the only remaining steps are:
6056 Commit @file{version.in} and @file{ChangeLog}
6058 Tweak @file{version.in} (and @file{ChangeLog} to read
6059 @var{L}.@var{M}.@var{N}-0000-00-00-cvs so that the version update
6060 process can restart.
6062 Make the release candidate available in
6063 @uref{ftp://sources.redhat.com/pub/gdb/snapshots/branch}
6065 Notify the relevant mailing lists ( @email{gdb@@sources.redhat.com} and
6066 @email{gdb-testers@@sources.redhat.com} that the candidate is available.
6069 @subsection Make a formal release available
6071 (And you thought all that was required was to post an e-mail.)
6073 @subsubheading Install on sware
6075 Copy the new files to both the release and the old release directory:
6078 $ cp *.bz2 *.gz ~ftp/pub/gdb/old-releases/
6079 $ cp *.bz2 *.gz ~ftp/pub/gdb/releases
6083 Clean up the releases directory so that only the most recent releases
6084 are available (e.g. keep 5.2 and 5.2.1 but remove 5.1):
6087 $ cd ~ftp/pub/gdb/releases
6092 Update the file @file{README} and @file{.message} in the releases
6099 $ ln README .message
6102 @subsubheading Update the web pages.
6106 @item htdocs/download/ANNOUNCEMENT
6107 This file, which is posted as the official announcement, includes:
6110 General announcement
6112 News. If making an @var{M}.@var{N}.1 release, retain the news from
6113 earlier @var{M}.@var{N} release.
6118 @item htdocs/index.html
6119 @itemx htdocs/news/index.html
6120 @itemx htdocs/download/index.html
6121 These files include:
6124 announcement of the most recent release
6126 news entry (remember to update both the top level and the news directory).
6128 These pages also need to be regenerate using @code{index.sh}.
6130 @item download/onlinedocs/
6131 You need to find the magic command that is used to generate the online
6132 docs from the @file{.tar.bz2}. The best way is to look in the output
6133 from one of the nightly @code{cron} jobs and then just edit accordingly.
6137 $ ~/ss/update-web-docs \
6138 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6140 /www/sourceware/htdocs/gdb/download/onlinedocs \
6145 Just like the online documentation. Something like:
6148 $ /bin/sh ~/ss/update-web-ari \
6149 ~ftp/pub/gdb/releases/gdb-5.2.tar.bz2 \
6151 /www/sourceware/htdocs/gdb/download/ari \
6157 @subsubheading Shadow the pages onto gnu
6159 Something goes here.
6162 @subsubheading Install the @value{GDBN} tar ball on GNU
6164 At the time of writing, the GNU machine was @kbd{gnudist.gnu.org} in
6165 @file{~ftp/gnu/gdb}.
6167 @subsubheading Make the @file{ANNOUNCEMENT}
6169 Post the @file{ANNOUNCEMENT} file you created above to:
6173 @email{gdb-announce@@sources.redhat.com, GDB Announcement mailing list}
6175 @email{info-gnu@@gnu.org, General GNU Announcement list} (but delay it a
6176 day or so to let things get out)
6178 @email{bug-gdb@@gnu.org, GDB Bug Report mailing list}
6183 The release is out but you're still not finished.
6185 @subsubheading Commit outstanding changes
6187 In particular you'll need to commit any changes to:
6191 @file{gdb/ChangeLog}
6193 @file{gdb/version.in}
6200 @subsubheading Tag the release
6205 $ d=`date -u +%Y-%m-%d`
6208 $ ( cd insight/src/gdb && cvs -f -q update )
6209 $ ( cd insight/src && cvs -f -q tag gdb_5_2-$d-release )
6212 Insight is used since that contains more of the release than
6213 @value{GDBN} (@code{dejagnu} doesn't get tagged but I think we can live
6216 @subsubheading Mention the release on the trunk
6218 Just put something in the @file{ChangeLog} so that the trunk also
6219 indicates when the release was made.
6221 @subsubheading Restart @file{gdb/version.in}
6223 If @file{gdb/version.in} does not contain an ISO date such as
6224 @kbd{2002-01-24} then the daily @code{cronjob} won't update it. Having
6225 committed all the release changes it can be set to
6226 @file{5.2.0_0000-00-00-cvs} which will restart things (yes the @kbd{_}
6227 is important - it affects the snapshot process).
6229 Don't forget the @file{ChangeLog}.
6231 @subsubheading Merge into trunk
6233 The files committed to the branch may also need changes merged into the
6236 @subsubheading Revise the release schedule
6238 Post a revised release schedule to @email{gdb@@sources.redhat.com, GDB
6239 Discussion List} with an updated announcement. The schedule can be
6240 generated by running:
6243 $ ~/ss/schedule `date +%s` schedule
6247 The first parameter is approximate date/time in seconds (from the epoch)
6248 of the most recent release.
6250 Also update the schedule @code{cronjob}.
6252 @section Post release
6254 Remove any @code{OBSOLETE} code.
6261 The testsuite is an important component of the @value{GDBN} package.
6262 While it is always worthwhile to encourage user testing, in practice
6263 this is rarely sufficient; users typically use only a small subset of
6264 the available commands, and it has proven all too common for a change
6265 to cause a significant regression that went unnoticed for some time.
6267 The @value{GDBN} testsuite uses the DejaGNU testing framework.
6268 DejaGNU is built using @code{Tcl} and @code{expect}. The tests
6269 themselves are calls to various @code{Tcl} procs; the framework runs all the
6270 procs and summarizes the passes and fails.
6272 @section Using the Testsuite
6274 @cindex running the test suite
6275 To run the testsuite, simply go to the @value{GDBN} object directory (or to the
6276 testsuite's objdir) and type @code{make check}. This just sets up some
6277 environment variables and invokes DejaGNU's @code{runtest} script. While
6278 the testsuite is running, you'll get mentions of which test file is in use,
6279 and a mention of any unexpected passes or fails. When the testsuite is
6280 finished, you'll get a summary that looks like this:
6285 # of expected passes 6016
6286 # of unexpected failures 58
6287 # of unexpected successes 5
6288 # of expected failures 183
6289 # of unresolved testcases 3
6290 # of untested testcases 5
6293 The ideal test run consists of expected passes only; however, reality
6294 conspires to keep us from this ideal. Unexpected failures indicate
6295 real problems, whether in @value{GDBN} or in the testsuite. Expected
6296 failures are still failures, but ones which have been decided are too
6297 hard to deal with at the time; for instance, a test case might work
6298 everywhere except on AIX, and there is no prospect of the AIX case
6299 being fixed in the near future. Expected failures should not be added
6300 lightly, since you may be masking serious bugs in @value{GDBN}.
6301 Unexpected successes are expected fails that are passing for some
6302 reason, while unresolved and untested cases often indicate some minor
6303 catastrophe, such as the compiler being unable to deal with a test
6306 When making any significant change to @value{GDBN}, you should run the
6307 testsuite before and after the change, to confirm that there are no
6308 regressions. Note that truly complete testing would require that you
6309 run the testsuite with all supported configurations and a variety of
6310 compilers; however this is more than really necessary. In many cases
6311 testing with a single configuration is sufficient. Other useful
6312 options are to test one big-endian (Sparc) and one little-endian (x86)
6313 host, a cross config with a builtin simulator (powerpc-eabi,
6314 mips-elf), or a 64-bit host (Alpha).
6316 If you add new functionality to @value{GDBN}, please consider adding
6317 tests for it as well; this way future @value{GDBN} hackers can detect
6318 and fix their changes that break the functionality you added.
6319 Similarly, if you fix a bug that was not previously reported as a test
6320 failure, please add a test case for it. Some cases are extremely
6321 difficult to test, such as code that handles host OS failures or bugs
6322 in particular versions of compilers, and it's OK not to try to write
6323 tests for all of those.
6325 @section Testsuite Organization
6327 @cindex test suite organization
6328 The testsuite is entirely contained in @file{gdb/testsuite}. While the
6329 testsuite includes some makefiles and configury, these are very minimal,
6330 and used for little besides cleaning up, since the tests themselves
6331 handle the compilation of the programs that @value{GDBN} will run. The file
6332 @file{testsuite/lib/gdb.exp} contains common utility procs useful for
6333 all @value{GDBN} tests, while the directory @file{testsuite/config} contains
6334 configuration-specific files, typically used for special-purpose
6335 definitions of procs like @code{gdb_load} and @code{gdb_start}.
6337 The tests themselves are to be found in @file{testsuite/gdb.*} and
6338 subdirectories of those. The names of the test files must always end
6339 with @file{.exp}. DejaGNU collects the test files by wildcarding
6340 in the test directories, so both subdirectories and individual files
6341 get chosen and run in alphabetical order.
6343 The following table lists the main types of subdirectories and what they
6344 are for. Since DejaGNU finds test files no matter where they are
6345 located, and since each test file sets up its own compilation and
6346 execution environment, this organization is simply for convenience and
6351 This is the base testsuite. The tests in it should apply to all
6352 configurations of @value{GDBN} (but generic native-only tests may live here).
6353 The test programs should be in the subset of C that is valid K&R,
6354 ANSI/ISO, and C++ (@code{#ifdef}s are allowed if necessary, for instance
6357 @item gdb.@var{lang}
6358 Language-specific tests for any language @var{lang} besides C. Examples are
6359 @file{gdb.c++} and @file{gdb.java}.
6361 @item gdb.@var{platform}
6362 Non-portable tests. The tests are specific to a specific configuration
6363 (host or target), such as HP-UX or eCos. Example is @file{gdb.hp}, for
6366 @item gdb.@var{compiler}
6367 Tests specific to a particular compiler. As of this writing (June
6368 1999), there aren't currently any groups of tests in this category that
6369 couldn't just as sensibly be made platform-specific, but one could
6370 imagine a @file{gdb.gcc}, for tests of @value{GDBN}'s handling of GCC
6373 @item gdb.@var{subsystem}
6374 Tests that exercise a specific @value{GDBN} subsystem in more depth. For
6375 instance, @file{gdb.disasm} exercises various disassemblers, while
6376 @file{gdb.stabs} tests pathways through the stabs symbol reader.
6379 @section Writing Tests
6380 @cindex writing tests
6382 In many areas, the @value{GDBN} tests are already quite comprehensive; you
6383 should be able to copy existing tests to handle new cases.
6385 You should try to use @code{gdb_test} whenever possible, since it
6386 includes cases to handle all the unexpected errors that might happen.
6387 However, it doesn't cost anything to add new test procedures; for
6388 instance, @file{gdb.base/exprs.exp} defines a @code{test_expr} that
6389 calls @code{gdb_test} multiple times.
6391 Only use @code{send_gdb} and @code{gdb_expect} when absolutely
6392 necessary, such as when @value{GDBN} has several valid responses to a command.
6394 The source language programs do @emph{not} need to be in a consistent
6395 style. Since @value{GDBN} is used to debug programs written in many different
6396 styles, it's worth having a mix of styles in the testsuite; for
6397 instance, some @value{GDBN} bugs involving the display of source lines would
6398 never manifest themselves if the programs used GNU coding style
6405 Check the @file{README} file, it often has useful information that does not
6406 appear anywhere else in the directory.
6409 * Getting Started:: Getting started working on @value{GDBN}
6410 * Debugging GDB:: Debugging @value{GDBN} with itself
6413 @node Getting Started,,, Hints
6415 @section Getting Started
6417 @value{GDBN} is a large and complicated program, and if you first starting to
6418 work on it, it can be hard to know where to start. Fortunately, if you
6419 know how to go about it, there are ways to figure out what is going on.
6421 This manual, the @value{GDBN} Internals manual, has information which applies
6422 generally to many parts of @value{GDBN}.
6424 Information about particular functions or data structures are located in
6425 comments with those functions or data structures. If you run across a
6426 function or a global variable which does not have a comment correctly
6427 explaining what is does, this can be thought of as a bug in @value{GDBN}; feel
6428 free to submit a bug report, with a suggested comment if you can figure
6429 out what the comment should say. If you find a comment which is
6430 actually wrong, be especially sure to report that.
6432 Comments explaining the function of macros defined in host, target, or
6433 native dependent files can be in several places. Sometimes they are
6434 repeated every place the macro is defined. Sometimes they are where the
6435 macro is used. Sometimes there is a header file which supplies a
6436 default definition of the macro, and the comment is there. This manual
6437 also documents all the available macros.
6438 @c (@pxref{Host Conditionals}, @pxref{Target
6439 @c Conditionals}, @pxref{Native Conditionals}, and @pxref{Obsolete
6442 Start with the header files. Once you have some idea of how
6443 @value{GDBN}'s internal symbol tables are stored (see @file{symtab.h},
6444 @file{gdbtypes.h}), you will find it much easier to understand the
6445 code which uses and creates those symbol tables.
6447 You may wish to process the information you are getting somehow, to
6448 enhance your understanding of it. Summarize it, translate it to another
6449 language, add some (perhaps trivial or non-useful) feature to @value{GDBN}, use
6450 the code to predict what a test case would do and write the test case
6451 and verify your prediction, etc. If you are reading code and your eyes
6452 are starting to glaze over, this is a sign you need to use a more active
6455 Once you have a part of @value{GDBN} to start with, you can find more
6456 specifically the part you are looking for by stepping through each
6457 function with the @code{next} command. Do not use @code{step} or you
6458 will quickly get distracted; when the function you are stepping through
6459 calls another function try only to get a big-picture understanding
6460 (perhaps using the comment at the beginning of the function being
6461 called) of what it does. This way you can identify which of the
6462 functions being called by the function you are stepping through is the
6463 one which you are interested in. You may need to examine the data
6464 structures generated at each stage, with reference to the comments in
6465 the header files explaining what the data structures are supposed to
6468 Of course, this same technique can be used if you are just reading the
6469 code, rather than actually stepping through it. The same general
6470 principle applies---when the code you are looking at calls something
6471 else, just try to understand generally what the code being called does,
6472 rather than worrying about all its details.
6474 @cindex command implementation
6475 A good place to start when tracking down some particular area is with
6476 a command which invokes that feature. Suppose you want to know how
6477 single-stepping works. As a @value{GDBN} user, you know that the
6478 @code{step} command invokes single-stepping. The command is invoked
6479 via command tables (see @file{command.h}); by convention the function
6480 which actually performs the command is formed by taking the name of
6481 the command and adding @samp{_command}, or in the case of an
6482 @code{info} subcommand, @samp{_info}. For example, the @code{step}
6483 command invokes the @code{step_command} function and the @code{info
6484 display} command invokes @code{display_info}. When this convention is
6485 not followed, you might have to use @code{grep} or @kbd{M-x
6486 tags-search} in emacs, or run @value{GDBN} on itself and set a
6487 breakpoint in @code{execute_command}.
6489 @cindex @code{bug-gdb} mailing list
6490 If all of the above fail, it may be appropriate to ask for information
6491 on @code{bug-gdb}. But @emph{never} post a generic question like ``I was
6492 wondering if anyone could give me some tips about understanding
6493 @value{GDBN}''---if we had some magic secret we would put it in this manual.
6494 Suggestions for improving the manual are always welcome, of course.
6496 @node Debugging GDB,,,Hints
6498 @section Debugging @value{GDBN} with itself
6499 @cindex debugging @value{GDBN}
6501 If @value{GDBN} is limping on your machine, this is the preferred way to get it
6502 fully functional. Be warned that in some ancient Unix systems, like
6503 Ultrix 4.2, a program can't be running in one process while it is being
6504 debugged in another. Rather than typing the command @kbd{@w{./gdb
6505 ./gdb}}, which works on Suns and such, you can copy @file{gdb} to
6506 @file{gdb2} and then type @kbd{@w{./gdb ./gdb2}}.
6508 When you run @value{GDBN} in the @value{GDBN} source directory, it will read a
6509 @file{.gdbinit} file that sets up some simple things to make debugging
6510 gdb easier. The @code{info} command, when executed without a subcommand
6511 in a @value{GDBN} being debugged by gdb, will pop you back up to the top level
6512 gdb. See @file{.gdbinit} for details.
6514 If you use emacs, you will probably want to do a @code{make TAGS} after
6515 you configure your distribution; this will put the machine dependent
6516 routines for your local machine where they will be accessed first by
6519 Also, make sure that you've either compiled @value{GDBN} with your local cc, or
6520 have run @code{fixincludes} if you are compiling with gcc.
6522 @section Submitting Patches
6524 @cindex submitting patches
6525 Thanks for thinking of offering your changes back to the community of
6526 @value{GDBN} users. In general we like to get well designed enhancements.
6527 Thanks also for checking in advance about the best way to transfer the
6530 The @value{GDBN} maintainers will only install ``cleanly designed'' patches.
6531 This manual summarizes what we believe to be clean design for @value{GDBN}.
6533 If the maintainers don't have time to put the patch in when it arrives,
6534 or if there is any question about a patch, it goes into a large queue
6535 with everyone else's patches and bug reports.
6537 @cindex legal papers for code contributions
6538 The legal issue is that to incorporate substantial changes requires a
6539 copyright assignment from you and/or your employer, granting ownership
6540 of the changes to the Free Software Foundation. You can get the
6541 standard documents for doing this by sending mail to @code{gnu@@gnu.org}
6542 and asking for it. We recommend that people write in "All programs
6543 owned by the Free Software Foundation" as "NAME OF PROGRAM", so that
6544 changes in many programs (not just @value{GDBN}, but GAS, Emacs, GCC,
6546 contributed with only one piece of legalese pushed through the
6547 bureaucracy and filed with the FSF. We can't start merging changes until
6548 this paperwork is received by the FSF (their rules, which we follow
6549 since we maintain it for them).
6551 Technically, the easiest way to receive changes is to receive each
6552 feature as a small context diff or unidiff, suitable for @code{patch}.
6553 Each message sent to me should include the changes to C code and
6554 header files for a single feature, plus @file{ChangeLog} entries for
6555 each directory where files were modified, and diffs for any changes
6556 needed to the manuals (@file{gdb/doc/gdb.texinfo} or
6557 @file{gdb/doc/gdbint.texinfo}). If there are a lot of changes for a
6558 single feature, they can be split down into multiple messages.
6560 In this way, if we read and like the feature, we can add it to the
6561 sources with a single patch command, do some testing, and check it in.
6562 If you leave out the @file{ChangeLog}, we have to write one. If you leave
6563 out the doc, we have to puzzle out what needs documenting. Etc., etc.
6565 The reason to send each change in a separate message is that we will not
6566 install some of the changes. They'll be returned to you with questions
6567 or comments. If we're doing our job correctly, the message back to you
6568 will say what you have to fix in order to make the change acceptable.
6569 The reason to have separate messages for separate features is so that
6570 the acceptable changes can be installed while one or more changes are
6571 being reworked. If multiple features are sent in a single message, we
6572 tend to not put in the effort to sort out the acceptable changes from
6573 the unacceptable, so none of the features get installed until all are
6576 If this sounds painful or authoritarian, well, it is. But we get a lot
6577 of bug reports and a lot of patches, and many of them don't get
6578 installed because we don't have the time to finish the job that the bug
6579 reporter or the contributor could have done. Patches that arrive
6580 complete, working, and well designed, tend to get installed on the day
6581 they arrive. The others go into a queue and get installed as time
6582 permits, which, since the maintainers have many demands to meet, may not
6583 be for quite some time.
6585 Please send patches directly to
6586 @email{gdb-patches@@sources.redhat.com, the @value{GDBN} maintainers}.
6588 @section Obsolete Conditionals
6589 @cindex obsolete code
6591 Fragments of old code in @value{GDBN} sometimes reference or set the following
6592 configuration macros. They should not be used by new code, and old uses
6593 should be removed as those parts of the debugger are otherwise touched.
6596 @item STACK_END_ADDR
6597 This macro used to define where the end of the stack appeared, for use
6598 in interpreting core file formats that don't record this address in the
6599 core file itself. This information is now configured in BFD, and @value{GDBN}
6600 gets the info portably from there. The values in @value{GDBN}'s configuration
6601 files should be moved into BFD configuration files (if needed there),
6602 and deleted from all of @value{GDBN}'s config files.
6604 Any @file{@var{foo}-xdep.c} file that references STACK_END_ADDR
6605 is so old that it has never been converted to use BFD. Now that's old!
6609 @include observer.texi