1 @c Copyright (C) 2008-2014 Free Software Foundation, Inc.
2 @c Permission is granted to copy, distribute and/or modify this document
3 @c under the terms of the GNU Free Documentation License, Version 1.3 or
4 @c any later version published by the Free Software Foundation; with the
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7 @c and with the Back-Cover Texts as in (a) below.
9 @c (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
10 @c this GNU Manual. Buying copies from GNU Press supports the FSF in
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14 @section Extending @value{GDBN} using Guile
15 @cindex guile scripting
16 @cindex scripting with guile
18 You can extend @value{GDBN} using the @uref{http://www.gnu.org/software/guile/,
19 Guile implementation of the Scheme programming language}.
20 This feature is available only if @value{GDBN} was configured using
21 @option{--with-guile}.
24 * Guile Introduction:: Introduction to Guile scripting in @value{GDBN}
25 * Guile Commands:: Accessing Guile from @value{GDBN}
26 * Guile API:: Accessing @value{GDBN} from Guile
27 * Guile Auto-loading:: Automatically loading Guile code
28 * Guile Modules:: Guile modules provided by @value{GDBN}
31 @node Guile Introduction
32 @subsection Guile Introduction
34 Guile is an implementation of the Scheme programming language
35 and is the GNU project's official extension language.
37 Guile support in @value{GDBN} follows the Python support in @value{GDBN}
38 reasonably closely, so concepts there should carry over.
39 However, some things are done differently where it makes sense.
41 @value{GDBN} requires Guile version 2.0 or greater.
42 Older versions are not supported.
44 @cindex guile scripts directory
45 Guile scripts used by @value{GDBN} should be installed in
46 @file{@var{data-directory}/guile}, where @var{data-directory} is
47 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
48 This directory, known as the @dfn{guile directory},
49 is automatically added to the Guile Search Path in order to allow
50 the Guile interpreter to locate all scripts installed at this location.
53 @subsection Guile Commands
54 @cindex guile commands
55 @cindex commands to access guile
57 @value{GDBN} provides two commands for accessing the Guile interpreter:
64 The @code{guile-repl} command can be used to start an interactive
65 Guile prompt or @dfn{repl}. To return to @value{GDBN},
66 type @kbd{,q} or the @code{EOF} character (e.g., @kbd{Ctrl-D} on
67 an empty prompt). These commands do not take any arguments.
71 @item guile @r{[}@var{scheme-expression}@r{]}
72 @itemx gu @r{[}@var{scheme-expression}@r{]}
73 The @code{guile} command can be used to evaluate a Scheme expression.
75 If given an argument, @value{GDBN} will pass the argument to the Guile
76 interpreter for evaluation.
79 (@value{GDBP}) guile (display (+ 20 3)) (newline)
83 The result of the Scheme expression is displayed using normal Guile rules.
86 (@value{GDBP}) guile (+ 20 3)
90 If you do not provide an argument to @code{guile}, it will act as a
91 multi-line command, like @code{define}. In this case, the Guile
92 script is made up of subsequent command lines, given after the
93 @code{guile} command. This command list is terminated using a line
94 containing @code{end}. For example:
105 It is also possible to execute a Guile script from the @value{GDBN}
109 @item source @file{script-name}
110 The script name must end with @samp{.scm} and @value{GDBN} must be configured
111 to recognize the script language based on filename extension using
112 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
114 @item guile (load "script-name")
115 This method uses the @code{load} Guile function.
116 It takes a string argument that is the name of the script to load.
117 See the Guile documentation for a description of this function.
118 (@pxref{Loading,,, guile, GNU Guile Reference Manual}).
122 @subsection Guile API
124 @cindex programming in guile
126 You can get quick online help for @value{GDBN}'s Guile API by issuing
127 the command @w{@kbd{help guile}}, or by issuing the command @kbd{,help}
128 from an interactive Guile session. Furthermore, most Guile procedures
129 provided by @value{GDBN} have doc strings which can be obtained with
130 @kbd{,describe @var{procedure-name}} or @kbd{,d @var{procedure-name}}
131 from the Guile interactive prompt.
134 * Basic Guile:: Basic Guile Functions
135 * Guile Configuration:: Guile configuration variables
136 * GDB Scheme Data Types:: Scheme representations of GDB objects
137 * Guile Exception Handling:: How Guile exceptions are translated
138 * Values From Inferior In Guile:: Guile representation of values
139 * Arithmetic In Guile:: Arithmetic in Guile
140 * Types In Guile:: Guile representation of types
141 * Guile Pretty Printing API:: Pretty-printing values with Guile
142 * Selecting Guile Pretty-Printers:: How GDB chooses a pretty-printer
143 * Writing a Guile Pretty-Printer:: Writing a pretty-printer
144 * Objfiles In Guile:: Object files in Guile
145 * Frames In Guile:: Accessing inferior stack frames from Guile
146 * Blocks In Guile:: Accessing blocks from Guile
147 * Symbols In Guile:: Guile representation of symbols
148 * Symbol Tables In Guile:: Guile representation of symbol tables
149 * Breakpoints In Guile:: Manipulating breakpoints using Guile
150 * Lazy Strings In Guile:: Guile representation of lazy strings
151 * Architectures In Guile:: Guile representation of architectures
152 * Disassembly In Guile:: Disassembling instructions from Guile
153 * I/O Ports in Guile:: GDB I/O ports
154 * Memory Ports in Guile:: Accessing memory through ports and bytevectors
155 * Iterators In Guile:: Basic iterator support
159 @subsubsection Basic Guile
162 @cindex guile pagination
163 At startup, @value{GDBN} overrides Guile's @code{current-output-port} and
164 @code{current-error-port} to print using @value{GDBN}'s output-paging streams.
165 A Guile program which outputs to one of these streams may have its
166 output interrupted by the user (@pxref{Screen Size}). In this
167 situation, a Guile @code{signal} exception is thrown with value @code{SIGINT}.
169 Guile's history mechanism uses the same naming as @value{GDBN}'s,
170 namely the user of dollar-variables (e.g., $1, $2, etc.).
171 The results of evaluations in Guile and in GDB are counted separately,
172 @code{$1} in Guile is not the same value as @code{$1} in @value{GDBN}.
174 @value{GDBN} is not thread-safe. If your Guile program uses multiple
175 threads, you must be careful to only call @value{GDBN}-specific
176 functions in the @value{GDBN} thread.
178 Some care must be taken when writing Guile code to run in
179 @value{GDBN}. Two things are worth noting in particular:
183 @value{GDBN} installs handlers for @code{SIGCHLD} and @code{SIGINT}.
184 Guile code must not override these, or even change the options using
185 @code{sigaction}. If your program changes the handling of these
186 signals, @value{GDBN} will most likely stop working correctly. Note
187 that it is unfortunately common for GUI toolkits to install a
188 @code{SIGCHLD} handler.
191 @value{GDBN} takes care to mark its internal file descriptors as
192 close-on-exec. However, this cannot be done in a thread-safe way on
193 all platforms. Your Guile programs should be aware of this and
194 should both create new file descriptors with the close-on-exec flag
195 set and arrange to close unneeded file descriptors before starting a
199 @cindex guile gdb module
200 @value{GDBN} introduces a new Guile module, named @code{gdb}. All
201 methods and classes added by @value{GDBN} are placed in this module.
202 @value{GDBN} does not automatically @code{import} the @code{gdb} module,
203 scripts must do this themselves. There are various options for how to
204 import a module, so @value{GDBN} leaves the choice of how the @code{gdb}
205 module is imported to the user.
206 To simplify interactive use, it is recommended to add one of the following
210 guile (use-modules (gdb))
214 guile (use-modules ((gdb) #:renamer (symbol-prefix-proc 'gdb:)))
217 Which one to choose depends on your preference.
218 The second one adds @code{gdb:} as a prefix to all module functions
221 The rest of this manual assumes the @code{gdb} module has been imported
222 without any prefix. See the Guile documentation for @code{use-modules}
224 (@pxref{Using Guile Modules,,, guile, GNU Guile Reference Manual}).
229 (gdb) guile (value-type (make-value 1))
230 ERROR: Unbound variable: value-type
231 Error while executing Scheme code.
232 (gdb) guile (use-modules (gdb))
233 (gdb) guile (value-type (make-value 1))
238 The @code{(gdb)} module provides these basic Guile functions.
241 @deffn {Scheme Procedure} execute command @r{[}#:from-tty boolean@r{]}@r{[}#:to-string boolean@r{]}
242 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
243 If a @value{GDBN} exception happens while @var{command} runs, it is
244 translated as described in
245 @ref{Guile Exception Handling,,Guile Exception Handling}.
247 @var{from-tty} specifies whether @value{GDBN} ought to consider this
248 command as having originated from the user invoking it interactively.
249 It must be a boolean value. If omitted, it defaults to @code{#f}.
251 By default, any output produced by @var{command} is sent to
252 @value{GDBN}'s standard output (and to the log output if logging is
253 turned on). If the @var{to-string} parameter is
254 @code{#t}, then output will be collected by @code{gdb.execute} and
255 returned as a string. The default is @code{#f}, in which case the
256 return value is unspecified. If @var{to-string} is @code{#t}, the
257 @value{GDBN} virtual terminal will be temporarily set to unlimited width
258 and height, and its pagination will be disabled; @pxref{Screen Size}.
261 @deffn {Scheme Procedure} history-ref number
262 Return a value from @value{GDBN}'s value history (@pxref{Value
263 History}). @var{number} indicates which history element to return.
264 If @var{number} is negative, then @value{GDBN} will take its absolute value
265 and count backward from the last element (i.e., the most recent element) to
266 find the value to return. If @var{number} is zero, then @value{GDBN} will
267 return the most recent element. If the element specified by @var{number}
268 doesn't exist in the value history, a @code{gdb:error} exception will be
271 If no exception is raised, the return value is always an instance of
272 @code{<gdb:value>} (@pxref{Values From Inferior In Guile}).
274 @emph{Note:} @value{GDBN}'s value history is independent of Guile's.
275 @code{$1} in @value{GDBN}'s value history contains the result of evaluating
276 an expression from @value{GDBN}'s command line and @code{$1} from Guile's
277 history contains the result of evaluating an expression from Guile's
281 @deffn {Scheme Procedure} parse-and-eval expression
282 Parse @var{expression} as an expression in the current language,
283 evaluate it, and return the result as a @code{<gdb:value>}.
284 @var{expression} must be a string.
286 This function is useful when computing values.
287 For example, it is the only way to get the value of a
288 convenience variable (@pxref{Convenience Vars}) as a @code{<gdb:value>}.
291 @deffn {Scheme Procedure} string->argv string
292 Convert a string to a list of strings split up according to
293 @value{GDBN}'s argv parsing rules.
296 @node Guile Configuration
297 @subsubsection Guile Configuration
298 @cindex guile configuration
300 @value{GDBN} provides these Scheme functions to access various configuration
303 @deffn {Scheme Procedure} data-directory
304 Return a string containing @value{GDBN}'s data directory.
305 This directory contains @value{GDBN}'s ancillary files, including
306 the Guile modules provided by @value{GDBN}.
309 @deffn {Scheme Procedure} gdb-version
310 Return a string containing the @value{GDBN} version.
313 @deffn {Scheme Procedure} host-config
314 Return a string containing the host configuration.
315 This is the string passed to @code{--host} when @value{GDBN} was configured.
318 @deffn {Scheme Procedure} target-config
319 Return a string containing the target configuration.
320 This is the string passed to @code{--target} when @value{GDBN} was configured.
323 @node GDB Scheme Data Types
324 @subsubsection GDB Scheme Data Types
327 @value{GDBN} uses Guile's @dfn{smob} (small object)
328 data type for all @value{GDBN} objects
329 (@pxref{Defining New Types (Smobs),,, guile, GNU Guile Reference Manual}).
330 The smobs that @value{GDBN} provides are called @dfn{gsmobs}.
332 @deffn {Scheme Procedure} gsmob-kind gsmob
333 Return the kind of the gsmob, e.g., @code{<gdb:breakpoint>},
337 Every @code{gsmob} provides a common set of functions for extending
338 them in simple ways. Each @code{gsmob} has a list of properties,
339 initially empty. These properties are akin to Guile's object properties,
340 but are stored with the @code{gsmob}
341 (@pxref{Object Properties,,, guile, GNU Guile Reference Manual}).
342 Property names can be any @code{eq?}-able value, but it is recommended
343 that they be symbols.
345 @deffn {Scheme Procedure} set-gsmob-property! gsmob property-name value
346 Set the value of property @code{property-name} to value @code{value}.
347 The result is unspecified.
350 @deffn {Scheme Procedure} gsmob-property gsmob property-name
351 Return the value of property @code{property-name}.
352 If the property isn't present then @code{#f} is returned.
355 @deffn {Scheme Procedure} gsmob-has-property? gsmob property-name
356 Return @code{#t} if @code{gsmob} has property @code{property-name}.
357 Otherwise return @code{#f}.
360 @deffn {Scheme Procedure} gsmob-properties gsmob
361 Return an unsorted list of names of properties.
364 @value{GDBN} defines the following Scheme smobs:
368 @xref{Architectures In Guile}.
371 @xref{Blocks In Guile}.
373 @item <gdb:block-symbols-iterator>
374 @xref{Blocks In Guile}.
376 @item <gdb:breakpoint>
377 @xref{Breakpoints In Guile}.
379 @item <gdb:exception>
380 @xref{Guile Exception Handling}.
383 @xref{Frames In Guile}.
386 @xref{Iterators In Guile}.
388 @item <gdb:lazy-string>
389 @xref{Lazy Strings In Guile}.
392 @xref{Objfiles In Guile}.
394 @item <gdb:pretty-printer>
395 @xref{Guile Pretty Printing API}.
397 @item <gdb:pretty-printer-worker>
398 @xref{Guile Pretty Printing API}.
401 @xref{Symbols In Guile}.
404 @xref{Symbol Tables In Guile}.
407 @xref{Symbol Tables In Guile}.
410 @xref{Types In Guile}.
413 @xref{Types In Guile}.
416 @xref{Values From Inferior In Guile}.
419 The following gsmobs are managed internally so that the Scheme function
420 @code{eq?} may be applied to them.
425 @item <gdb:breakpoint>
433 @node Guile Exception Handling
434 @subsubsection Guile Exception Handling
435 @cindex guile exceptions
436 @cindex exceptions, guile
437 @kindex set guile print-stack
439 When executing the @code{guile} command, Guile exceptions
440 uncaught within the Guile code are translated to calls to the
441 @value{GDBN} error-reporting mechanism. If the command that called
442 @code{guile} does not handle the error, @value{GDBN} will
443 terminate it and report the error according to the setting of
444 the @code{guile print-stack} parameter.
446 The @code{guile print-stack} parameter has three settings:
453 An error message is printed containing the Guile exception name,
454 the associated value, and the Guile call stack backtrace at the
455 point where the exception was raised. Example:
458 (@value{GDBP}) guile (display foo)
459 ERROR: In procedure memoize-variable-access!:
460 ERROR: Unbound variable: foo
461 Error while executing Scheme code.
465 In addition to an error message a full backtrace is printed.
468 (@value{GDBP}) set guile print-stack full
469 (@value{GDBP}) guile (display foo)
472 157: 10 [catch #t #<catch-closure 2c76e20> ...]
474 ?: 9 [apply-smob/1 #<catch-closure 2c76e20>]
476 157: 8 [catch #t #<catch-closure 2c76d20> ...]
478 ?: 7 [apply-smob/1 #<catch-closure 2c76d20>]
479 ?: 6 [call-with-input-string "(display foo)" ...]
481 2320: 5 [save-module-excursion #<procedure 2c2dc30 ... ()>]
482 In ice-9/eval-string.scm:
483 44: 4 [read-and-eval #<input: string 27cb410> #:lang ...]
484 37: 3 [lp (display foo)]
487 393: 1 [eval #<memoized foo> ()]
489 ?: 0 [memoize-variable-access! #<memoized foo> ...]
491 ERROR: In procedure memoize-variable-access!:
492 ERROR: Unbound variable: foo
493 Error while executing Scheme code.
497 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
498 Guile code are converted to Guile exceptions. The type of the
499 Guile exception depends on the error.
501 Guile procedures provided by @value{GDBN} can throw the standard
502 Guile exceptions like @code{wrong-type-arg} and @code{out-of-range}.
504 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
505 prompt) is translated to a Guile @code{signal} exception with value
508 @value{GDBN} Guile procedures can also throw these exceptions:
512 This exception is a catch-all for errors generated from within @value{GDBN}.
514 @item gdb:invalid-object
515 This exception is thrown when accessing Guile objects that wrap underlying
516 @value{GDBN} objects have become invalid. For example, a
517 @code{<gdb:breakpoint>} object becomes invalid if the user deletes it
518 from the command line. The object still exists in Guile, but the
519 object it represents is gone. Further operations on this breakpoint
520 will throw this exception.
522 @item gdb:memory-error
523 This exception is thrown when an operation tried to access invalid
524 memory in the inferior.
526 @item gdb:pp-type-error
527 This exception is thrown when a Guile pretty-printer passes a bad object
531 The following exception-related procedures are provided by the
534 @deffn {Scheme Procedure} make-exception key args
535 Return a @code{<gdb:exception>} object.
536 @var{key} and @var{args} are the standard Guile parameters of an exception.
537 See the Guile documentation for more information
538 (@pxref{Exceptions,,, guile, GNU Guile Reference Manual}).
541 @deffn {Scheme Procedure} exception? object
542 Return @code{#t} if @var{object} is a @code{<gdb:exception>} object.
543 Otherwise return @code{#f}.
546 @deffn {Scheme Procedure} exception-key exception
547 Return the @var{args} field of a @code{<gdb:exception>} object.
550 @deffn {Scheme Procedure} exception-args exception
551 Return the @var{args} field of a @code{<gdb:exception>} object.
554 @node Values From Inferior In Guile
555 @subsubsection Values From Inferior In Guile
556 @cindex values from inferior, in guile
557 @cindex guile, working with values from inferior
559 @tindex @code{<gdb:value>}
560 @value{GDBN} provides values it obtains from the inferior program in
561 an object of type @code{<gdb:value>}. @value{GDBN} uses this object
562 for its internal bookkeeping of the inferior's values, and for
563 fetching values when necessary.
565 @value{GDBN} does not memoize @code{<gdb:value>} objects.
566 @code{make-value} always returns a fresh object.
569 (gdb) guile (eq? (make-value 1) (make-value 1))
571 (gdb) guile (equal? (make-value 1) (make-value 1))
575 A @code{<gdb:value>} that represents a function can be executed via
576 inferior function call with @code{value-call}.
577 Any arguments provided to the call must match the function's prototype,
578 and must be provided in the order specified by that prototype.
580 For example, @code{some-val} is a @code{<gdb:value>} instance
581 representing a function that takes two integers as arguments. To
582 execute this function, call it like so:
585 (define result (value-call some-val 10 20))
588 Any values returned from a function call are @code{<gdb:value>} objects.
590 Note: Unlike Python scripting in @value{GDBN},
591 inferior values that are simple scalars cannot be used directly in
592 Scheme expressions that are valid for the value's data type.
593 For example, @code{(+ (parse-and-eval "int_variable") 2)} does not work.
594 And inferior values that are structures or instances of some class cannot
595 be accessed using any special syntax, instead @code{value-field} must be used.
597 The following value-related procedures are provided by the
600 @deffn {Scheme Procedure} value? object
601 Return @code{#t} if @var{object} is a @code{<gdb:value>} object.
602 Otherwise return @code{#f}.
605 @deffn {Scheme Procedure} make-value value @r{[}#:type type@r{]}
606 Many Scheme values can be converted directly to a @code{<gdb:value>}
607 with this procedure. If @var{type} is specified, the result is a value
608 of this type, and if @var{value} can't be represented with this type
609 an exception is thrown. Otherwise the type of the result is determined from
610 @var{value} as described below.
612 @xref{Architectures In Guile}, for a list of the builtin
613 types for an architecture.
615 Here's how Scheme values are converted when @var{type} argument to
616 @code{make-value} is not specified:
620 A Scheme boolean is converted the boolean type for the current language.
623 A Scheme integer is converted to the first of a C @code{int},
624 @code{unsigned int}, @code{long}, @code{unsigned long},
625 @code{long long} or @code{unsigned long long} type
626 for the current architecture that can represent the value.
628 If the Scheme integer cannot be represented as a target integer
629 an @code{out-of-range} exception is thrown.
632 A Scheme real is converted to the C @code{double} type for the
633 current architecture.
636 A Scheme string is converted to a string in the current target
637 language using the current target encoding.
638 Characters that cannot be represented in the current target encoding
639 are replaced with the corresponding escape sequence. This is Guile's
640 @code{SCM_FAILED_CONVERSION_ESCAPE_SEQUENCE} conversion strategy
641 (@pxref{Strings,,, guile, GNU Guile Reference Manual}).
643 Passing @var{type} is not supported in this case,
644 if it is provided a @code{wrong-type-arg} exception is thrown.
646 @item @code{<gdb:lazy-string>}
647 If @var{value} is a @code{<gdb:lazy-string>} object (@pxref{Lazy Strings In
648 Guile}), then the @code{lazy-string->value} procedure is called, and
651 Passing @var{type} is not supported in this case,
652 if it is provided a @code{wrong-type-arg} exception is thrown.
654 @item Scheme bytevector
655 If @var{value} is a Scheme bytevector and @var{type} is provided,
656 @var{value} must be the same size, in bytes, of values of type @var{type},
657 and the result is essentially created by using @code{memcpy}.
659 If @var{value} is a Scheme bytevector and @var{type} is not provided,
660 the result is an array of type @code{uint8} of the same length.
664 @cindex optimized out value in guile
665 @deffn {Scheme Procedure} value-optimized-out? value
666 Return @code{#t} if the compiler optimized out @var{value},
667 thus it is not available for fetching from the inferior.
668 Otherwise return @code{#f}.
671 @deffn {Scheme Procedure} value-address value
672 If @var{value} is addressable, returns a
673 @code{<gdb:value>} object representing the address.
674 Otherwise, @code{#f} is returned.
677 @deffn {Scheme Procedure} value-type value
678 Return the type of @var{value} as a @code{<gdb:type>} object
679 (@pxref{Types In Guile}).
682 @deffn {Scheme Procedure} value-dynamic-type value
683 Return the dynamic type of @var{value}. This uses C@t{++} run-time
684 type information (@acronym{RTTI}) to determine the dynamic type of the
685 value. If the value is of class type, it will return the class in
686 which the value is embedded, if any. If the value is of pointer or
687 reference to a class type, it will compute the dynamic type of the
688 referenced object, and return a pointer or reference to that type,
689 respectively. In all other cases, it will return the value's static
692 Note that this feature will only work when debugging a C@t{++} program
693 that includes @acronym{RTTI} for the object in question. Otherwise,
694 it will just return the static type of the value as in @kbd{ptype foo}.
695 @xref{Symbols, ptype}.
698 @deffn {Scheme Procedure} value-cast value type
699 Return a new instance of @code{<gdb:value>} that is the result of
700 casting @var{value} to the type described by @var{type}, which must
701 be a @code{<gdb:type>} object. If the cast cannot be performed for some
702 reason, this method throws an exception.
705 @deffn {Scheme Procedure} value-dynamic-cast value type
706 Like @code{value-cast}, but works as if the C@t{++} @code{dynamic_cast}
707 operator were used. Consult a C@t{++} reference for details.
710 @deffn {Scheme Procedure} value-reinterpret-cast value type
711 Like @code{value-cast}, but works as if the C@t{++} @code{reinterpret_cast}
712 operator were used. Consult a C@t{++} reference for details.
715 @deffn {Scheme Procedure} value-dereference value
716 For pointer data types, this method returns a new @code{<gdb:value>} object
717 whose contents is the object pointed to by @var{value}. For example, if
718 @code{foo} is a C pointer to an @code{int}, declared in your C program as
725 then you can use the corresponding @code{<gdb:value>} to access what
726 @code{foo} points to like this:
729 (define bar (value-dereference foo))
732 The result @code{bar} will be a @code{<gdb:value>} object holding the
733 value pointed to by @code{foo}.
735 A similar function @code{value-referenced-value} exists which also
736 returns @code{<gdb:value>} objects corresonding to the values pointed to
737 by pointer values (and additionally, values referenced by reference
738 values). However, the behavior of @code{value-dereference}
739 differs from @code{value-referenced-value} by the fact that the
740 behavior of @code{value-dereference} is identical to applying the C
741 unary operator @code{*} on a given value. For example, consider a
742 reference to a pointer @code{ptrref}, declared in your C@t{++} program
750 intptr &ptrref = ptr;
753 Though @code{ptrref} is a reference value, one can apply the method
754 @code{value-dereference} to the @code{<gdb:value>} object corresponding
755 to it and obtain a @code{<gdb:value>} which is identical to that
756 corresponding to @code{val}. However, if you apply the method
757 @code{value-referenced-value}, the result would be a @code{<gdb:value>}
758 object identical to that corresponding to @code{ptr}.
761 (define scm-ptrref (parse-and-eval "ptrref"))
762 (define scm-val (value-dereference scm-ptrref))
763 (define scm-ptr (value-referenced-value scm-ptrref))
766 The @code{<gdb:value>} object @code{scm-val} is identical to that
767 corresponding to @code{val}, and @code{scm-ptr} is identical to that
768 corresponding to @code{ptr}. In general, @code{value-dereference} can
769 be applied whenever the C unary operator @code{*} can be applied
770 to the corresponding C value. For those cases where applying both
771 @code{value-dereference} and @code{value-referenced-value} is allowed,
772 the results obtained need not be identical (as we have seen in the above
773 example). The results are however identical when applied on
774 @code{<gdb:value>} objects corresponding to pointers (@code{<gdb:value>}
775 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
778 @deffn {Scheme Procedure} value-referenced-value value
779 For pointer or reference data types, this method returns a new
780 @code{<gdb:value>} object corresponding to the value referenced by the
781 pointer/reference value. For pointer data types,
782 @code{value-dereference} and @code{value-referenced-value} produce
783 identical results. The difference between these methods is that
784 @code{value-dereference} cannot get the values referenced by reference
785 values. For example, consider a reference to an @code{int}, declared
786 in your C@t{++} program as
794 then applying @code{value-dereference} to the @code{<gdb:value>} object
795 corresponding to @code{ref} will result in an error, while applying
796 @code{value-referenced-value} will result in a @code{<gdb:value>} object
797 identical to that corresponding to @code{val}.
800 (define scm-ref (parse-and-eval "ref"))
801 (define err-ref (value-dereference scm-ref)) ;; error
802 (define scm-val (value-referenced-value scm-ref)) ;; ok
805 The @code{<gdb:value>} object @code{scm-val} is identical to that
806 corresponding to @code{val}.
809 @deffn {Scheme Procedure} value-field value field-name
810 Return field @var{field-name} from @code{<gdb:value>} object @var{value}.
813 @deffn {Scheme Procedure} value-subscript value index
814 Return the value of array @var{value} at index @var{index}.
815 @var{value} must be a subscriptable @code{<gdb:value>} object.
818 @deffn {Scheme Procedure} value-call value arg-list
819 Perform an inferior function call, taking @var{value} as a pointer
820 to the function to call.
821 Each element of list @var{arg-list} must be a <gdb:value> object or an object
822 that can be converted to a value.
823 The result is the value returned by the function.
826 @deffn {Scheme Procedure} value->bool value
827 Return the Scheme boolean representing @code{<gdb:value>} @var{value}.
828 The value must be ``integer like''. Pointers are ok.
831 @deffn {Scheme Procedure} value->integer
832 Return the Scheme integer representing @code{<gdb:value>} @var{value}.
833 The value must be ``integer like''. Pointers are ok.
836 @deffn {Scheme Procedure} value->real
837 Return the Scheme real number representing @code{<gdb:value>} @var{value}.
838 The value must be a number.
841 @deffn {Scheme Procedure} value->bytevector
842 Return a Scheme bytevector with the raw contents of @code{<gdb:value>}
843 @var{value}. No transformation, endian or otherwise, is performed.
847 @deffn {Scheme Procedure} value->string value @r{[}#:encoding encoding@r{]} @r{[}#:errors errors@r{]} @r{[}#:length length@r{]}
848 If @var{value>} represents a string, then this method
849 converts the contents to a Guile string. Otherwise, this method will
852 Values are interpreted as strings according to the rules of the
853 current language. If the optional length argument is given, the
854 string will be converted to that length, and will include any embedded
855 zeroes that the string may contain. Otherwise, for languages
856 where the string is zero-terminated, the entire string will be
859 For example, in C-like languages, a value is a string if it is a pointer
860 to or an array of characters or ints of type @code{wchar_t}, @code{char16_t},
863 If the optional @var{encoding} argument is given, it must be a string
864 naming the encoding of the string in the @code{<gdb:value>}, such as
865 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
866 the same encodings as the corresponding argument to Guile's
867 @code{scm_from_stringn} function, and the Guile codec machinery will be used
868 to convert the string. If @var{encoding} is not given, or if
869 @var{encoding} is the empty string, then either the @code{target-charset}
870 (@pxref{Character Sets}) will be used, or a language-specific encoding
871 will be used, if the current language is able to supply one.
873 The optional @var{errors} argument is one of @code{#f}, @code{error} or
874 @code{substitute}. @code{error} and @code{substitute} must be symbols.
875 If @var{errors} is not specified, or if its value is @code{#f}, then the
876 default conversion strategy is used, which is set with the Scheme function
877 @code{set-port-conversion-strategy!}.
878 If the value is @code{'error} then an exception is thrown if there is any
879 conversion error. If the value is @code{'substitute} then any conversion
880 error is replaced with question marks.
881 @xref{Strings,,, guile, GNU Guile Reference Manual}.
883 If the optional @var{length} argument is given, the string will be
884 fetched and converted to the given length.
885 The length must be a Scheme integer and not a @code{<gdb:value>} integer.
889 @deffn {Scheme Procedure} value->lazy-string value @r{[}#:encoding encoding@r{]} @r{[}#:length length@r{]})
890 If this @code{<gdb:value>} represents a string, then this method
891 converts @var{value} to a @code{<gdb:lazy-string} (@pxref{Lazy Strings
892 In Guile}). Otherwise, this method will throw an exception.
894 If the optional @var{encoding} argument is given, it must be a string
895 naming the encoding of the @code{<gdb:lazy-string}. Some examples are:
896 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. If the
897 @var{encoding} argument is an encoding that @value{GDBN} does not
898 recognize, @value{GDBN} will raise an error.
900 When a lazy string is printed, the @value{GDBN} encoding machinery is
901 used to convert the string during printing. If the optional
902 @var{encoding} argument is not provided, or is an empty string,
903 @value{GDBN} will automatically select the encoding most suitable for
904 the string type. For further information on encoding in @value{GDBN}
905 please see @ref{Character Sets}.
907 If the optional @var{length} argument is given, the string will be
908 fetched and encoded to the length of characters specified. If
909 the @var{length} argument is not provided, the string will be fetched
910 and encoded until a null of appropriate width is found.
911 The length must be a Scheme integer and not a @code{<gdb:value>} integer.
914 @deffn {Scheme Procedure} value-lazy? value
915 Return @code{#t} if @var{value} has not yet been fetched
917 Otherwise return @code{#f}.
918 @value{GDBN} does not fetch values until necessary, for efficiency.
922 (define myval (parse-and-eval "somevar"))
925 The value of @code{somevar} is not fetched at this time. It will be
926 fetched when the value is needed, or when the @code{fetch-lazy}
927 procedure is invoked.
930 @deffn {Scheme Procedure} make-lazy-value type address
931 Return a @code{<gdb:value>} that will be lazily fetched from the target.
932 @var{type} is an object of type @code{<gdb:type>} and @var{address} is
933 a Scheme integer of the address of the object in target memory.
936 @deffn {Scheme Procedure} value-fetch-lazy! value
937 If @var{value} is a lazy value (@code{(value-lazy? value)} is @code{#t}),
938 then the value is fetched from the inferior.
939 Any errors that occur in the process will produce a Guile exception.
941 If @var{value} is not a lazy value, this method has no effect.
943 The result of this function is unspecified.
946 @deffn {Scheme Procedure} value-print value
947 Return the string representation (print form) of @code{<gdb:value>}
951 @node Arithmetic In Guile
952 @subsubsection Arithmetic In Guile
954 The @code{(gdb)} module provides several functions for performing
955 arithmetic on @code{<gdb:value>} objects.
956 The arithmetic is performed as if it were done by the target,
957 and therefore has target semantics which are not necessarily
958 those of Scheme. For example operations work with a fixed precision,
959 not the arbitrary precision of Scheme.
961 Wherever a function takes an integer or pointer as an operand,
962 @value{GDBN} will convert appropriate Scheme values to perform
965 @deffn {Scheme Procedure} value-add a b
968 @deffn {Scheme Procedure} value-sub a b
971 @deffn {Scheme Procedure} value-mul a b
974 @deffn {Scheme Procedure} value-div a b
977 @deffn {Scheme Procedure} value-rem a b
980 @deffn {Scheme Procedure} value-mod a b
983 @deffn {Scheme Procedure} value-pow a b
986 @deffn {Scheme Procedure} value-not a
989 @deffn {Scheme Procedure} value-neg a
992 @deffn {Scheme Procedure} value-pos a
995 @deffn {Scheme Procedure} value-abs a
998 @deffn {Scheme Procedure} value-lsh a b
1001 @deffn {Scheme Procedure} value-rsh a b
1004 @deffn {Scheme Procedure} value-min a b
1007 @deffn {Scheme Procedure} value-max a b
1010 @deffn {Scheme Procedure} value-lognot a
1013 @deffn {Scheme Procedure} value-logand a b
1016 @deffn {Scheme Procedure} value-logior a b
1019 @deffn {Scheme Procedure} value-logxor a b
1022 @deffn {Scheme Procedure} value=? a b
1025 @deffn {Scheme Procedure} value<? a b
1028 @deffn {Scheme Procedure} value<=? a b
1031 @deffn {Scheme Procedure} value>? a b
1034 @deffn {Scheme Procedure} value>=? a b
1037 Scheme does not provide a @code{not-equal} function,
1038 and thus Guile support in @value{GDBN} does not either.
1040 @node Types In Guile
1041 @subsubsection Types In Guile
1042 @cindex types in guile
1043 @cindex guile, working with types
1046 @value{GDBN} represents types from the inferior in objects of type
1049 The following type-related procedures are provided by the
1050 @code{(gdb)} module.
1052 @deffn {Scheme Procedure} type? object
1053 Return @code{#t} if @var{object} is an object of type @code{<gdb:type>}.
1054 Otherwise return @code{#f}.
1057 @deffn {Scheme Procedure} lookup-type name @r{[}#:block block@r{]}
1058 This function looks up a type by name. @var{name} is the name of the
1059 type to look up. It must be a string.
1061 If @var{block} is given, it is an object of type @code{<gdb:block>},
1062 and @var{name} is looked up in that scope.
1063 Otherwise, it is searched for globally.
1065 Ordinarily, this function will return an instance of @code{<gdb:type>}.
1066 If the named type cannot be found, it will throw an exception.
1069 @deffn {Scheme Procedure} type-code type
1070 Return the type code of @var{type}. The type code will be one of the
1071 @code{TYPE_CODE_} constants defined below.
1074 @deffn {Scheme Procedure} type-tag type
1075 Return the tag name of @var{type}. The tag name is the name after
1076 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
1077 languages have this concept. If this type has no tag name, then
1078 @code{#f} is returned.
1081 @deffn {Scheme Procedure} type-name type
1082 Return the name of @var{type}.
1083 If this type has no name, then @code{#f} is returned.
1086 @deffn {Scheme Procedure} type-print-name type
1087 Return the print name of @var{type}.
1088 This returns something even for anonymous types.
1089 For example, for an anonymous C struct @code{"struct @{...@}"} is returned.
1092 @deffn {Scheme Procedure} type-sizeof type
1093 Return the size of this type, in target @code{char} units. Usually, a
1094 target's @code{char} type will be an 8-bit byte. However, on some
1095 unusual platforms, this type may have a different size.
1098 @deffn {Scheme Procedure} type-strip-typedefs type
1099 Return a new @code{<gdb:type>} that represents the real type of @var{type},
1100 after removing all layers of typedefs.
1103 @deffn {Scheme Procedure} type-array type n1 @r{[}n2@r{]}
1104 Return a new @code{<gdb:type>} object which represents an array of this
1105 type. If one argument is given, it is the inclusive upper bound of
1106 the array; in this case the lower bound is zero. If two arguments are
1107 given, the first argument is the lower bound of the array, and the
1108 second argument is the upper bound of the array. An array's length
1109 must not be negative, but the bounds can be.
1112 @deffn {Scheme Procedure} type-vector type n1 @r{[}n2@r{]}
1113 Return a new @code{<gdb:type>} object which represents a vector of this
1114 type. If one argument is given, it is the inclusive upper bound of
1115 the vector; in this case the lower bound is zero. If two arguments are
1116 given, the first argument is the lower bound of the vector, and the
1117 second argument is the upper bound of the vector. A vector's length
1118 must not be negative, but the bounds can be.
1120 The difference between an @code{array} and a @code{vector} is that
1121 arrays behave like in C: when used in expressions they decay to a pointer
1122 to the first element whereas vectors are treated as first class values.
1125 @deffn {Scheme Procedure} type-pointer type
1126 Return a new @code{<gdb:type>} object which represents a pointer to
1130 @deffn {Scheme Procedure} type-range type
1131 Return a list of two elements: the low bound and high bound of @var{type}.
1132 If @var{type} does not have a range, an exception is thrown.
1135 @deffn {Scheme Procedure} type-reference type
1136 Return a new @code{<gdb:type>} object which represents a reference to
1140 @deffn {Scheme Procedure} type-target type
1141 Return a new @code{<gdb:type>} object which represents the target type
1144 For a pointer type, the target type is the type of the pointed-to
1145 object. For an array type (meaning C-like arrays), the target type is
1146 the type of the elements of the array. For a function or method type,
1147 the target type is the type of the return value. For a complex type,
1148 the target type is the type of the elements. For a typedef, the
1149 target type is the aliased type.
1151 If the type does not have a target, this method will throw an
1155 @deffn {Scheme Procedure} type-const type
1156 Return a new @code{<gdb:type>} object which represents a
1157 @code{const}-qualified variant of @var{type}.
1160 @deffn {Scheme Procedure} type-volatile type
1161 Return a new @code{<gdb:type>} object which represents a
1162 @code{volatile}-qualified variant of @var{type}.
1165 @deffn {Scheme Procedure} type-unqualified type
1166 Return a new @code{<gdb:type>} object which represents an unqualified
1167 variant of @var{type}. That is, the result is neither @code{const} nor
1171 @deffn {Scheme Procedure} type-num-fields
1172 Return the number of fields of @code{<gdb:type>} @var{type}.
1175 @deffn {Scheme Procedure} type-fields type
1176 Return the fields of @var{type} as a list.
1177 For structure and union types, @code{fields} has the usual meaning.
1178 Range types have two fields, the minimum and maximum values. Enum types
1179 have one field per enum constant. Function and method types have one
1180 field per parameter. The base types of C@t{++} classes are also
1181 represented as fields. If the type has no fields, or does not fit
1182 into one of these categories, an empty list will be returned.
1183 @xref{Fields of a type in Guile}.
1186 @deffn {Scheme Procedure} make-field-iterator type
1187 Return the fields of @var{type} as a <gdb:iterator> object.
1188 @xref{Iterators In Guile}.
1191 @deffn {Scheme Procedure} type-field type field-name
1192 Return field named @var{field-name} in @var{type}.
1193 The result is an object of type @code{<gdb:field>}.
1194 @xref{Fields of a type in Guile}.
1195 If the type does not have fields, or @var{field-name} is not a field
1196 of @var{type}, an exception is thrown.
1198 For example, if @code{some-type} is a @code{<gdb:type>} instance holding
1199 a structure type, you can access its @code{foo} field with:
1202 (define bar (type-field some-type "foo"))
1205 @code{bar} will be a @code{<gdb:field>} object.
1208 @deffn {Scheme Procedure} type-has-field? type name
1209 Return @code{#t} if @code{<gdb:type>} @var{type} has field named @var{name}.
1210 Otherwise return @code{#f}.
1213 Each type has a code, which indicates what category this type falls
1214 into. The available type categories are represented by constants
1215 defined in the @code{(gdb)} module:
1219 The type is a pointer.
1221 @item TYPE_CODE_ARRAY
1222 The type is an array.
1224 @item TYPE_CODE_STRUCT
1225 The type is a structure.
1227 @item TYPE_CODE_UNION
1228 The type is a union.
1230 @item TYPE_CODE_ENUM
1231 The type is an enum.
1233 @item TYPE_CODE_FLAGS
1234 A bit flags type, used for things such as status registers.
1236 @item TYPE_CODE_FUNC
1237 The type is a function.
1240 The type is an integer type.
1243 A floating point type.
1245 @item TYPE_CODE_VOID
1246 The special type @code{void}.
1251 @item TYPE_CODE_RANGE
1252 A range type, that is, an integer type with bounds.
1254 @item TYPE_CODE_STRING
1255 A string type. Note that this is only used for certain languages with
1256 language-defined string types; C strings are not represented this way.
1258 @item TYPE_CODE_BITSTRING
1259 A string of bits. It is deprecated.
1261 @item TYPE_CODE_ERROR
1262 An unknown or erroneous type.
1264 @item TYPE_CODE_METHOD
1265 A method type, as found in C@t{++} or Java.
1267 @item TYPE_CODE_METHODPTR
1268 A pointer-to-member-function.
1270 @item TYPE_CODE_MEMBERPTR
1271 A pointer-to-member.
1276 @item TYPE_CODE_CHAR
1279 @item TYPE_CODE_BOOL
1282 @item TYPE_CODE_COMPLEX
1283 A complex float type.
1285 @item TYPE_CODE_TYPEDEF
1286 A typedef to some other type.
1288 @item TYPE_CODE_NAMESPACE
1289 A C@t{++} namespace.
1291 @item TYPE_CODE_DECFLOAT
1292 A decimal floating point type.
1294 @item TYPE_CODE_INTERNAL_FUNCTION
1295 A function internal to @value{GDBN}. This is the type used to represent
1296 convenience functions (@pxref{Convenience Funs}).
1299 Further support for types is provided in the @code{(gdb types)}
1300 Guile module (@pxref{Guile Types Module}).
1302 @anchor{Fields of a type in Guile}
1303 Each field is represented as an object of type @code{<gdb:field>}.
1305 The following field-related procedures are provided by the
1306 @code{(gdb)} module:
1308 @deffn {Scheme Procedure} field? object
1309 Return @code{#t} if @var{object} is an object of type @code{<gdb:field>}.
1310 Otherwise return @code{#f}.
1313 @deffn {Scheme Procedure} field-name field
1314 Return the name of the field, or @code{#f} for anonymous fields.
1317 @deffn {Scheme Procedure} field-type field
1318 Return the type of the field. This is usually an instance of
1319 @code{<gdb:type>}, but it can be @code{#f} in some situations.
1322 @deffn {Scheme Procedure} field-enumval field
1323 Return the enum value represented by @code{<gdb:field>} @var{field}.
1326 @deffn {Scheme Procedure} field-bitpos field
1327 Return the bit position of @code{<gdb:field>} @var{field}.
1328 This attribute is not available for @code{static} fields (as in
1332 @deffn {Scheme Procedure} field-bitsize field
1333 If the field is packed, or is a bitfield, return the size of
1334 @code{<gdb:field>} @var{field} in bits. Otherwise, zero is returned;
1335 in which case the field's size is given by its type.
1338 @deffn {Scheme Procedure} field-artificial? field
1339 Return @code{#t} if the field is artificial, usually meaning that
1340 it was provided by the compiler and not the user.
1341 Otherwise return @code{#f}.
1344 @deffn {Scheme Procedure} field-base-class? field
1345 Return @code{#t} if the field represents a base class of a C@t{++}
1347 Otherwise return @code{#f}.
1350 @node Guile Pretty Printing API
1351 @subsubsection Guile Pretty Printing API
1352 @cindex guile pretty printing api
1354 An example output is provided (@pxref{Pretty Printing}).
1356 A pretty-printer is represented by an object of type <gdb:pretty-printer>.
1357 Pretty-printer objects are created with @code{make-pretty-printer}.
1359 The following pretty-printer-related procedures are provided by the
1360 @code{(gdb)} module:
1362 @deffn {Scheme Procedure} make-pretty-printer name lookup-function
1363 Return a @code{<gdb:pretty-printer>} object named @var{name}.
1365 @var{lookup-function} is a function of one parameter: the value to
1366 be printed. If the value is handled by this pretty-printer, then
1367 @var{lookup-function} returns an object of type
1368 <gdb:pretty-printer-worker> to perform the actual pretty-printing.
1369 Otherwise @var{lookup-function} returns @code{#f}.
1372 @deffn {Scheme Procedure} pretty-printer? object
1373 Return @code{#t} if @var{object} is a @code{<gdb:pretty-printer>} object.
1374 Otherwise return @code{#f}.
1377 @deffn {Scheme Procedure} pretty-printer-enabled? pretty-printer
1378 Return @code{#t} if @var{pretty-printer} is enabled.
1379 Otherwise return @code{#f}.
1382 @deffn {Scheme Procedure} set-pretty-printer-enabled! pretty-printer flag
1383 Set the enabled flag of @var{pretty-printer} to @var{flag}.
1384 The value returned in unspecified.
1387 @deffn {Scheme Procedure} make-pretty-printer-worker display-hint to-string children
1388 Return an object of type @code{<gdb:pretty-printer-worker>}.
1390 This function takes three parameters:
1394 @var{display-hint} provides a hint to @value{GDBN} or @value{GDBN}
1395 front end via MI to change the formatting of the value being printed.
1396 The value must be a string or @code{#f} (meaning there is no hint).
1397 Several values for @var{display-hint}
1398 are predefined by @value{GDBN}:
1402 Indicate that the object being printed is ``array-like''. The CLI
1403 uses this to respect parameters such as @code{set print elements} and
1404 @code{set print array}.
1407 Indicate that the object being printed is ``map-like'', and that the
1408 children of this value can be assumed to alternate between keys and
1412 Indicate that the object being printed is ``string-like''. If the
1413 printer's @code{to-string} function returns a Guile string of some
1414 kind, then @value{GDBN} will call its internal language-specific
1415 string-printing function to format the string. For the CLI this means
1416 adding quotation marks, possibly escaping some characters, respecting
1417 @code{set print elements}, and the like.
1421 @var{to-string} is either a function of one parameter, the
1422 @code{<gdb:pretty-printer-worker>} object, or @code{#f}.
1424 When printing from the CLI, if the @code{to-string} method exists,
1425 then @value{GDBN} will prepend its result to the values returned by
1426 @code{children}. Exactly how this formatting is done is dependent on
1427 the display hint, and may change as more hints are added. Also,
1428 depending on the print settings (@pxref{Print Settings}), the CLI may
1429 print just the result of @code{to-string} in a stack trace, omitting
1430 the result of @code{children}.
1432 If this method returns a string, it is printed verbatim.
1434 Otherwise, if this method returns an instance of @code{<gdb:value>},
1435 then @value{GDBN} prints this value. This may result in a call to
1436 another pretty-printer.
1438 If instead the method returns a Guile value which is convertible to a
1439 @code{<gdb:value>}, then @value{GDBN} performs the conversion and prints
1440 the resulting value. Again, this may result in a call to another
1441 pretty-printer. Guile scalars (integers, floats, and booleans) and
1442 strings are convertible to @code{<gdb:value>}; other types are not.
1444 Finally, if this method returns @code{#f} then no further operations
1445 are peformed in this method and nothing is printed.
1447 If the result is not one of these types, an exception is raised.
1449 @var{to-string} may also be @code{#f} in which case it is left to
1450 @var{children} to print the value.
1453 @var{children} is either a function of one parameter, the
1454 @code{<gdb:pretty-printer-worker>} object, or @code{#f}.
1456 @value{GDBN} will call this function on a pretty-printer to compute the
1457 children of the pretty-printer's value.
1459 This function must return a <gdb:iterator> object.
1460 Each item returned by the iterator must be a tuple holding
1461 two elements. The first element is the ``name'' of the child; the
1462 second element is the child's value. The value can be any Guile
1463 object which is convertible to a @value{GDBN} value.
1465 If @var{children} is @code{#f}, @value{GDBN} will act
1466 as though the value has no children.
1470 @value{GDBN} provides a function which can be used to look up the
1471 default pretty-printer for a @code{<gdb:value>}:
1473 @deffn {Scheme Procedure} default-visualizer value
1474 This function takes a @code{<gdb:value>} object as an argument. If a
1475 pretty-printer for this value exists, then it is returned. If no such
1476 printer exists, then this returns @code{#f}.
1479 @node Selecting Guile Pretty-Printers
1480 @subsubsection Selecting Guile Pretty-Printers
1481 @cindex selecting guile pretty-printers
1483 The Guile list @code{*pretty-printers*} contains a set of
1484 @code{<gdb:pretty-printer>} registered objects.
1485 Printers in this list are called @code{global}
1486 printers, they're available when debugging any inferior.
1487 In addition to this, each @code{<gdb:objfile>} object contains its
1488 own set of pretty-printers (@pxref{Objfiles In Guile}).
1490 Pretty-printer lookup is done by passing the value to be printed to the
1491 lookup function of each enabled object in turn.
1492 Lookup stops when a lookup function returns a non-@code{#f} value
1493 or when the list is exhausted.
1495 @value{GDBN} first checks the result of @code{objfile-pretty-printers}
1496 of each @code{<gdb:objfile>} in the current program space and iteratively
1497 calls each enabled lookup function in the list for that @code{<gdb:objfile>}
1498 until a non-@code{#f} object is returned.
1499 Lookup functions must return either a @code{<gdb:pretty-printer-worker>}
1500 object or @code{#f}. Otherwise an exception is thrown.
1501 If no pretty-printer is found in the objfile lists, @value{GDBN} then
1502 searches the global pretty-printer list, calling each enabled function
1503 until a non-@code{#f} object is returned.
1505 The order in which the objfiles are searched is not specified. For a
1506 given list, functions are always invoked from the head of the list,
1507 and iterated over sequentially until the end of the list, or a
1508 @code{<gdb:pretty-printer-worker>} object is returned.
1510 For various reasons a pretty-printer may not work.
1511 For example, the underlying data structure may have changed and
1512 the pretty-printer is out of date.
1514 The consequences of a broken pretty-printer are severe enough that
1515 @value{GDBN} provides support for enabling and disabling individual
1516 printers. For example, if @code{print frame-arguments} is on,
1517 a backtrace can become highly illegible if any argument is printed
1518 with a broken printer.
1520 Pretty-printers are enabled and disabled from Scheme by calling
1521 @code{set-pretty-printer-enabled!}.
1522 @xref{Guile Pretty Printing API}.
1524 @node Writing a Guile Pretty-Printer
1525 @subsubsection Writing a Guile Pretty-Printer
1526 @cindex writing a Guile pretty-printer
1528 A pretty-printer consists of two basic parts: a lookup function to determine
1529 if the type is supported, and the printer itself.
1531 Here is an example showing how a @code{std::string} printer might be
1532 written. @xref{Guile Pretty Printing API}, for details.
1535 (define (make-my-string-printer value)
1536 "Print a my::string string"
1537 (make-pretty-printer-worker
1540 (value-field value "_data"))
1544 And here is an example showing how a lookup function for the printer
1545 example above might be written.
1548 (define (string-begins-with str prefix)
1549 (= (string-prefix-length str prefix) (string-length prefix)))
1551 (define (str-lookup-function value)
1552 (let ((tag (type-tag (value-type value))))
1554 (string-begins-with tag "my::string<")
1555 (make-std-string-printer value))))
1558 Then to register this printer in the global printer list:
1561 (append-pretty-printer!
1562 (make-pretty-printer "my-string" str-lookup-function))
1565 The example lookup function extracts the value's type, and attempts to
1566 match it to a type that it can pretty-print. If it is a type the
1567 printer can pretty-print, it will return a <gdb:pretty-printer-worker> object.
1568 If not, it returns @code{#f}.
1570 We recommend that you put your core pretty-printers into a Guile
1571 package. If your pretty-printers are for use with a library, we
1572 further recommend embedding a version number into the package name.
1573 This practice will enable @value{GDBN} to load multiple versions of
1574 your pretty-printers at the same time, because they will have
1577 You should write auto-loaded code (@pxref{Guile Auto-loading}) such that it
1578 can be evaluated multiple times without changing its meaning. An
1579 ideal auto-load file will consist solely of @code{import}s of your
1580 printer modules, followed by a call to a register pretty-printers with
1581 the current objfile.
1583 Taken as a whole, this approach will scale nicely to multiple
1584 inferiors, each potentially using a different library version.
1585 Embedding a version number in the Guile package name will ensure that
1586 @value{GDBN} is able to load both sets of printers simultaneously.
1587 Then, because the search for pretty-printers is done by objfile, and
1588 because your auto-loaded code took care to register your library's
1589 printers with a specific objfile, @value{GDBN} will find the correct
1590 printers for the specific version of the library used by each
1593 To continue the @code{my::string} example,
1594 this code might appear in @code{(my-project my-library v1)}:
1597 (use-modules ((gdb)))
1598 (define (register-printers objfile)
1599 (append-objfile-pretty-printer!
1600 (make-pretty-printer "my-string" str-lookup-function)))
1604 And then the corresponding contents of the auto-load file would be:
1607 (use-modules ((gdb) (my-project my-library v1)))
1608 (register-printers (current-objfile))
1611 The previous example illustrates a basic pretty-printer.
1612 There are a few things that can be improved on.
1613 The printer only handles one type, whereas a library typically has
1614 several types. One could install a lookup function for each desired type
1615 in the library, but one could also have a single lookup function recognize
1616 several types. The latter is the conventional way this is handled.
1617 If a pretty-printer can handle multiple data types, then its
1618 @dfn{subprinters} are the printers for the individual data types.
1620 The @code{(gdb printing)} module provides a formal way of solving this
1621 problem (@pxref{Guile Printing Module}).
1622 Here is another example that handles multiple types.
1624 These are the types we are going to pretty-print:
1627 struct foo @{ int a, b; @};
1628 struct bar @{ struct foo x, y; @};
1631 Here are the printers:
1634 (define (make-foo-printer value)
1635 "Print a foo object"
1636 (make-pretty-printer-worker
1639 (format #f "a=<~a> b=<~a>"
1640 (value-field value "a") (value-field value "a")))
1643 (define (make-bar-printer value)
1644 "Print a bar object"
1645 (make-pretty-printer-worker
1648 (format #f "x=<~a> y=<~a>"
1649 (value-field value "x") (value-field value "y")))
1653 This example doesn't need a lookup function, that is handled by the
1654 @code{(gdb printing)} module. Instead a function is provided to build up
1655 the object that handles the lookup.
1658 (use-modules ((gdb printing)))
1660 (define (build-pretty-printer)
1661 (let ((pp (make-pretty-printer-collection "my-library")))
1662 (pp-collection-add-tag-printer "foo" make-foo-printer)
1663 (pp-collection-add-tag-printer "bar" make-bar-printer)
1667 And here is the autoload support:
1670 (use-modules ((gdb) (my-library)))
1671 (append-objfile-pretty-printer! (current-objfile) (build-pretty-printer))
1674 Finally, when this printer is loaded into @value{GDBN}, here is the
1675 corresponding output of @samp{info pretty-printer}:
1678 (gdb) info pretty-printer
1685 @node Objfiles In Guile
1686 @subsubsection Objfiles In Guile
1688 @cindex objfiles in guile
1689 @tindex <gdb:objfile>
1690 @value{GDBN} loads symbols for an inferior from various
1691 symbol-containing files (@pxref{Files}). These include the primary
1692 executable file, any shared libraries used by the inferior, and any
1693 separate debug info files (@pxref{Separate Debug Files}).
1694 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
1696 Each objfile is represented as an object of type @code{<gdb:objfile>}.
1698 The following objfile-related procedures are provided by the
1699 @code{(gdb)} module:
1701 @deffn {Scheme Procedure} objfile? object
1702 Return @code{#t} if @var{object} is a @code{<gdb:objfile>} object.
1703 Otherwise return @code{#f}.
1706 @deffn {Scheme Procedure} objfile-valid? objfile
1707 Return @code{#t} if @var{objfile} is valid, @code{#f} if not.
1708 A @code{<gdb:objfile>} object can become invalid
1709 if the object file it refers to is not loaded in @value{GDBN} any
1710 longer. All other @code{<gdb:objfile>} procedures will throw an exception
1711 if it is invalid at the time the procedure is called.
1714 @deffn {Scheme Procedure} objfile-filename objfile
1715 Return the file name of @var{objfile} as a string.
1718 @deffn {Scheme Procedure} objfile-pretty-printers objfile
1719 Return the list of registered @code{<gdb:pretty-printer>} objects for
1720 @var{objfile}. @xref{Guile Pretty Printing API}, for more information.
1723 @deffn {Scheme Procedure} set-objfile-pretty-printers! objfile printer-list
1724 Set the list of registered @code{<gdb:pretty-printer>} objects for
1725 @var{objfile} to @var{printer-list}.
1726 @var{printer-list} must be a list of @code{<gdb:pretty-printer>} objects.
1727 @xref{Guile Pretty Printing API}, for more information.
1730 @deffn {Scheme Procedure} current-objfile
1731 When auto-loading a Guile script (@pxref{Guile Auto-loading}), @value{GDBN}
1732 sets the ``current objfile'' to the corresponding objfile. This
1733 function returns the current objfile. If there is no current objfile,
1734 this function returns @code{#f}.
1737 @deffn {Scheme Procedure} objfiles
1738 Return a list of all the objfiles in the current program space.
1741 @node Frames In Guile
1742 @subsubsection Accessing inferior stack frames from Guile.
1744 @cindex frames in guile
1745 When the debugged program stops, @value{GDBN} is able to analyze its call
1746 stack (@pxref{Frames,,Stack frames}). The @code{<gdb:frame>} class
1747 represents a frame in the stack. A @code{<gdb:frame>} object is only valid
1748 while its corresponding frame exists in the inferior's stack. If you try
1749 to use an invalid frame object, @value{GDBN} will throw a
1750 @code{gdb:invalid-object} exception (@pxref{Guile Exception Handling}).
1752 Two @code{<gdb:frame>} objects can be compared for equality with the
1753 @code{equal?} function, like:
1756 (@value{GDBP}) guile (equal? (newest-frame) (selected-frame))
1760 The following frame-related procedures are provided by the
1761 @code{(gdb)} module:
1763 @deffn {Scheme Procedure} frame? object
1764 Return @code{#t} if @var{object} is a @code{<gdb:frame>} object.
1765 Otherwise return @code{#f}.
1768 @deffn {Scheme Procedure} frame-valid? frame
1769 Returns @code{#t} if @var{frame} is valid, @code{#f} if not.
1770 A frame object can become invalid if the frame it refers to doesn't
1771 exist anymore in the inferior. All @code{<gdb:frame>} procedures will throw
1772 an exception if the frame is invalid at the time the procedure is called.
1775 @deffn {Scheme Procedure} frame-name frame
1776 Return the function name of @var{frame}, or @code{#f} if it can't be
1780 @deffn {Scheme Procedure} frame-arch frame
1781 Return the @code{<gdb:architecture>} object corresponding to @var{frame}'s
1782 architecture. @xref{Architectures In Guile}.
1785 @deffn {Scheme Procedure} frame-type frame
1786 Return the type of @var{frame}. The value can be one of:
1790 An ordinary stack frame.
1793 A fake stack frame that was created by @value{GDBN} when performing an
1794 inferior function call.
1797 A frame representing an inlined function. The function was inlined
1798 into a @code{NORMAL_FRAME} that is older than this one.
1800 @item TAILCALL_FRAME
1801 A frame representing a tail call. @xref{Tail Call Frames}.
1803 @item SIGTRAMP_FRAME
1804 A signal trampoline frame. This is the frame created by the OS when
1805 it calls into a signal handler.
1808 A fake stack frame representing a cross-architecture call.
1810 @item SENTINEL_FRAME
1811 This is like @code{NORMAL_FRAME}, but it is only used for the
1816 @deffn {Scheme Procedure} frame-unwind-stop-reason frame
1817 Return an integer representing the reason why it's not possible to find
1818 more frames toward the outermost frame. Use
1819 @code{unwind-stop-reason-string} to convert the value returned by this
1820 function to a string. The value can be one of:
1823 @item FRAME_UNWIND_NO_REASON
1824 No particular reason (older frames should be available).
1826 @item FRAME_UNWIND_NULL_ID
1827 The previous frame's analyzer returns an invalid result.
1829 @item FRAME_UNWIND_OUTERMOST
1830 This frame is the outermost.
1832 @item FRAME_UNWIND_UNAVAILABLE
1833 Cannot unwind further, because that would require knowing the
1834 values of registers or memory that have not been collected.
1836 @item FRAME_UNWIND_INNER_ID
1837 This frame ID looks like it ought to belong to a NEXT frame,
1838 but we got it for a PREV frame. Normally, this is a sign of
1839 unwinder failure. It could also indicate stack corruption.
1841 @item FRAME_UNWIND_SAME_ID
1842 This frame has the same ID as the previous one. That means
1843 that unwinding further would almost certainly give us another
1844 frame with exactly the same ID, so break the chain. Normally,
1845 this is a sign of unwinder failure. It could also indicate
1848 @item FRAME_UNWIND_NO_SAVED_PC
1849 The frame unwinder did not find any saved PC, but we needed
1850 one to unwind further.
1852 @item FRAME_UNWIND_FIRST_ERROR
1853 Any stop reason greater or equal to this value indicates some kind
1854 of error. This special value facilitates writing code that tests
1855 for errors in unwinding in a way that will work correctly even if
1856 the list of the other values is modified in future @value{GDBN}
1857 versions. Using it, you could write:
1860 (define reason (frame-unwind-stop-readon (selected-frame)))
1861 (define reason-str (unwind-stop-reason-string reason))
1862 (if (>= reason FRAME_UNWIND_FIRST_ERROR)
1863 (format #t "An error occured: ~s\n" reason-str))
1868 @deffn {Scheme Procedure} frame-pc frame
1869 Return the frame's resume address.
1872 @deffn {Scheme Procedure} frame-block frame
1873 Return the frame's code block as a @code{<gdb:block>} object.
1874 @xref{Blocks In Guile}.
1877 @deffn {Scheme Procedure} frame-function frame
1878 Return the symbol for the function corresponding to this frame
1879 as a @code{<gdb:symbol>} object, or @code{#f} if there isn't one.
1880 @xref{Symbols In Guile}.
1883 @deffn {Scheme Procedure} frame-older frame
1884 Return the frame that called @var{frame}.
1887 @deffn {Scheme Procedure} frame-newer frame
1888 Return the frame called by @var{frame}.
1891 @deffn {Scheme Procedure} frame-sal frame
1892 Return the frame's @code{<gdb:sal>} (symtab and line) object.
1893 @xref{Symbol Tables In Guile}.
1896 @deffn {Scheme Procedure} frame-read-var variable @r{[}#:block block@r{]}
1897 Return the value of @var{variable} in this frame. If the optional
1898 argument @var{block} is provided, search for the variable from that
1899 block; otherwise start at the frame's current block (which is
1900 determined by the frame's current program counter). @var{variable}
1901 must be a string or a @code{<gdb:symbol>} object. @var{block} must be a
1902 @code{<gdb:block>} object.
1905 @deffn {Scheme Procedure} frame-select frame
1906 Set @var{frame} to be the selected frame. @xref{Stack, ,Examining the
1910 @deffn {Scheme Procedure} selected-frame
1911 Return the selected frame object. @xref{Selection,,Selecting a Frame}.
1914 @deffn {Scheme Procedure} newest-frame
1915 Return the newest frame object for the selected thread.
1918 @deffn {Scheme Procedure} unwind-stop-reason-string reason
1919 Return a string explaining the reason why @value{GDBN} stopped unwinding
1920 frames, as expressed by the given @var{reason} code (an integer, see the
1921 @code{frame-unwind-stop-reason} procedure above in this section).
1924 @node Blocks In Guile
1925 @subsubsection Accessing blocks from Guile.
1927 @cindex blocks in guile
1930 In @value{GDBN}, symbols are stored in blocks. A block corresponds
1931 roughly to a scope in the source code. Blocks are organized
1932 hierarchically, and are represented individually in Guile as an object
1933 of type @code{<gdb:block>}. Blocks rely on debugging information being
1936 A frame has a block. Please see @ref{Frames In Guile}, for a more
1937 in-depth discussion of frames.
1939 The outermost block is known as the @dfn{global block}. The global
1940 block typically holds public global variables and functions.
1942 The block nested just inside the global block is the @dfn{static
1943 block}. The static block typically holds file-scoped variables and
1946 @value{GDBN} provides a method to get a block's superblock, but there
1947 is currently no way to examine the sub-blocks of a block, or to
1948 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
1951 Here is a short example that should help explain blocks:
1954 /* This is in the global block. */
1957 /* This is in the static block. */
1958 static int file_scope;
1960 /* 'function' is in the global block, and 'argument' is
1961 in a block nested inside of 'function'. */
1962 int function (int argument)
1964 /* 'local' is in a block inside 'function'. It may or may
1965 not be in the same block as 'argument'. */
1969 /* 'inner' is in a block whose superblock is the one holding
1973 /* If this call is expanded by the compiler, you may see
1974 a nested block here whose function is 'inline_function'
1975 and whose superblock is the one holding 'inner'. */
1981 The following block-related procedures are provided by the
1982 @code{(gdb)} module:
1984 @deffn {Scheme Procedure} block? object
1985 Return @code{#t} if @var{object} is a @code{<gdb:block>} object.
1986 Otherwise return @code{#f}.
1989 @deffn {Scheme Procedure} block-valid? block
1990 Returns @code{#t} if @code{<gdb:block>} @var{block} is valid,
1991 @code{#f} if not. A block object can become invalid if the block it
1992 refers to doesn't exist anymore in the inferior. All other
1993 @code{<gdb:block>} methods will throw an exception if it is invalid at
1994 the time the procedure is called. The block's validity is also checked
1995 during iteration over symbols of the block.
1998 @deffn {Scheme Procedure} block-start block
1999 Return the start address of @code{<gdb:block>} @var{block}.
2002 @deffn {Scheme Procedure} block-end block
2003 Return the end address of @code{<gdb:block>} @var{block}.
2006 @deffn {Scheme Procedure} block-function block
2007 Return the name of @code{<gdb:block>} @var{block} represented as a
2008 @code{<gdb:symbol>} object.
2009 If the block is not named, then @code{#f} is returned.
2011 For ordinary function blocks, the superblock is the static block.
2012 However, you should note that it is possible for a function block to
2013 have a superblock that is not the static block -- for instance this
2014 happens for an inlined function.
2017 @deffn {Scheme Procedure} block-superblock block
2018 Return the block containing @code{<gdb:block>} @var{block}.
2019 If the parent block does not exist, then @code{#f} is returned.
2022 @deffn {Scheme Procedure} block-global-block block
2023 Return the global block associated with @code{<gdb:block>} @var{block}.
2026 @deffn {Scheme Procedure} block-static-block block
2027 Return the static block associated with @code{<gdb:block>} @var{block}.
2030 @deffn {Scheme Procedure} block-global? block
2031 Return @code{#t} if @code{<gdb:block>} @var{block} is a global block.
2032 Otherwise return @code{#f}.
2035 @deffn {Scheme Procedure} block-static? block
2036 Return @code{#t} if @code{<gdb:block>} @var{block} is a static block.
2037 Otherwise return @code{#f}.
2040 @deffn {Scheme Procedure} block-symbols
2041 Return a list of all symbols (as <gdb:symbol> objects) in
2042 @code{<gdb:block>} @var{block}.
2045 @deffn {Scheme Procedure} make-block-symbols-iterator block
2046 Return an object of type @code{<gdb:iterator>} that will iterate
2047 over all symbols of the block.
2048 Guile programs should not assume that a specific block object will
2049 always contain a given symbol, since changes in @value{GDBN} features and
2050 infrastructure may cause symbols move across blocks in a symbol table.
2051 @xref{Iterators In Guile}.
2054 @deffn {Scheme Procedure} block-symbols-progress?
2055 Return #t if the object is a <gdb:block-symbols-progress> object.
2056 This object would be obtained from the @code{progress} element of the
2057 @code{<gdb:iterator>} object returned by @code{make-block-symbols-iterator}.
2060 @deffn {Scheme Procedure} lookup-block pc
2061 Return the innermost @code{<gdb:block>} containing the given @var{pc}
2062 value. If the block cannot be found for the @var{pc} value specified,
2063 the function will return @code{#f}.
2066 @node Symbols In Guile
2067 @subsubsection Guile representation of Symbols.
2069 @cindex symbols in guile
2070 @tindex <gdb:symbol>
2072 @value{GDBN} represents every variable, function and type as an
2073 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
2074 Guile represents these symbols in @value{GDBN} with the
2075 @code{<gdb:symbol>} object.
2077 The following symbol-related procedures are provided by the
2078 @code{(gdb)} module:
2080 @deffn {Scheme Procedure} symbol? object
2081 Return @code{#t} if @var{object} is an object of type @code{<gdb:symbol>}.
2082 Otherwise return @code{#f}.
2085 @deffn {Scheme Procedure} symbol-valid? symbol
2086 Return @code{#t} if the @code{<gdb:symbol>} object is valid,
2087 @code{#f} if not. A @code{<gdb:symbol>} object can become invalid if
2088 the symbol it refers to does not exist in @value{GDBN} any longer.
2089 All other @code{<gdb:symbol>} procedures will throw an exception if it is
2090 invalid at the time the procedure is called.
2093 @deffn {Scheme Procedure} symbol-type symbol
2094 Return the type of @var{symbol} or @code{#f} if no type is recorded.
2095 The result is an object of type @code{<gdb:type>}.
2096 @xref{Types In Guile}.
2099 @deffn {Scheme Procedure} symbol-symtab symbol
2100 Return the symbol table in which @var{symbol} appears.
2101 The result is an object of type @code{<gdb:symtab>}.
2102 @xref{Symbol Tables In Guile}.
2105 @deffn {Scheme Procedure} symbol-line symbol
2106 Return the line number in the source code at which @var{symbol} was defined.
2110 @deffn {Scheme Procedure} symbol-name symbol
2111 Return the name of @var{symbol} as a string.
2114 @deffn {Scheme Procedure} symbol-linkage-name symbol
2115 Return the name of @var{symbol}, as used by the linker (i.e., may be mangled).
2118 @deffn {Scheme Procedure} symbol-print-name symbol
2119 Return the name of @var{symbol} in a form suitable for output. This is either
2120 @code{name} or @code{linkage_name}, depending on whether the user
2121 asked @value{GDBN} to display demangled or mangled names.
2124 @deffn {Scheme Procedure} symbol-addr-class symbol
2125 Return the address class of the symbol. This classifies how to find the value
2126 of a symbol. Each address class is a constant defined in the
2127 @code{(gdb)} module and described later in this chapter.
2130 @deffn {Scheme Procedure} symbol-needs-frame? symbol
2131 Return @code{#t} if evaluating @var{symbol}'s value requires a frame
2132 (@pxref{Frames In Guile}) and @code{#f} otherwise. Typically,
2133 local variables will require a frame, but other symbols will not.
2136 @deffn {Scheme Procedure} symbol-argument? symbol
2137 Return @code{#t} if @var{symbol} is an argument of a function.
2138 Otherwise return @code{#f}.
2141 @deffn {Scheme Procedure} symbol-constant? symbol
2142 Return @code{#t} if @var{symbol} is a constant.
2143 Otherwise return @code{#f}.
2146 @deffn {Scheme Procedure} symbol-function? symbol
2147 Return @code{#t} if @var{symbol} is a function or a method.
2148 Otherwise return @code{#f}.
2151 @deffn {Scheme Procedure} symbol-variable? symbol
2152 Return @code{#t} if @var{symbol} is a variable.
2153 Otherwise return @code{#f}.
2156 @deffn {Scheme Procedure} symbol-value symbol @r{[}#:frame frame@r{]}
2157 Compute the value of @var{symbol}, as a @code{<gdb:value>}. For
2158 functions, this computes the address of the function, cast to the
2159 appropriate type. If the symbol requires a frame in order to compute
2160 its value, then @var{frame} must be given. If @var{frame} is not
2161 given, or if @var{frame} is invalid, then an exception is thrown.
2164 @c TODO: line length
2165 @deffn {Scheme Procedure} lookup-symbol name @r{[}#:block block@r{]} @r{[}#:domain domain@r{]}
2166 This function searches for a symbol by name. The search scope can be
2167 restricted to the parameters defined in the optional domain and block
2170 @var{name} is the name of the symbol. It must be a string. The
2171 optional @var{block} argument restricts the search to symbols visible
2172 in that @var{block}. The @var{block} argument must be a
2173 @code{<gdb:block>} object. If omitted, the block for the current frame
2174 is used. The optional @var{domain} argument restricts
2175 the search to the domain type. The @var{domain} argument must be a
2176 domain constant defined in the @code{(gdb)} module and described later
2179 The result is a list of two elements.
2180 The first element is a @code{<gdb:symbol>} object or @code{#f} if the symbol
2182 If the symbol is found, the second element is @code{#t} if the symbol
2183 is a field of a method's object (e.g., @code{this} in C@t{++}),
2184 otherwise it is @code{#f}.
2185 If the symbol is not found, the second element is @code{#f}.
2188 @deffn {Scheme Procedure} lookup-global-symbol name @r{[}#:domain domain@r{]}
2189 This function searches for a global symbol by name.
2190 The search scope can be restricted by the domain argument.
2192 @var{name} is the name of the symbol. It must be a string.
2193 The optional @var{domain} argument restricts the search to the domain type.
2194 The @var{domain} argument must be a domain constant defined in the @code{(gdb)}
2195 module and described later in this chapter.
2197 The result is a @code{<gdb:symbol>} object or @code{#f} if the symbol
2201 The available domain categories in @code{<gdb:symbol>} are represented
2202 as constants in the @code{(gdb)} module:
2205 @item SYMBOL_UNDEF_DOMAIN
2206 This is used when a domain has not been discovered or none of the
2207 following domains apply. This usually indicates an error either
2208 in the symbol information or in @value{GDBN}'s handling of symbols.
2210 @item SYMBOL_VAR_DOMAIN
2211 This domain contains variables, function names, typedef names and enum
2214 @item SYMBOL_STRUCT_DOMAIN
2215 This domain holds struct, union and enum type names.
2217 @item SYMBOL_LABEL_DOMAIN
2218 This domain contains names of labels (for gotos).
2220 @item SYMBOL_VARIABLES_DOMAIN
2221 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
2222 contains everything minus functions and types.
2224 @item SYMBOL_FUNCTION_DOMAIN
2225 This domain contains all functions.
2227 @item SYMBOL_TYPES_DOMAIN
2228 This domain contains all types.
2231 The available address class categories in @code{<gdb:symbol>} are represented
2232 as constants in the @code{gdb} module:
2235 @item SYMBOL_LOC_UNDEF
2236 If this is returned by address class, it indicates an error either in
2237 the symbol information or in @value{GDBN}'s handling of symbols.
2239 @item SYMBOL_LOC_CONST
2240 Value is constant int.
2242 @item SYMBOL_LOC_STATIC
2243 Value is at a fixed address.
2245 @item SYMBOL_LOC_REGISTER
2246 Value is in a register.
2248 @item SYMBOL_LOC_ARG
2249 Value is an argument. This value is at the offset stored within the
2250 symbol inside the frame's argument list.
2252 @item SYMBOL_LOC_REF_ARG
2253 Value address is stored in the frame's argument list. Just like
2254 @code{LOC_ARG} except that the value's address is stored at the
2255 offset, not the value itself.
2257 @item SYMBOL_LOC_REGPARM_ADDR
2258 Value is a specified register. Just like @code{LOC_REGISTER} except
2259 the register holds the address of the argument instead of the argument
2262 @item SYMBOL_LOC_LOCAL
2263 Value is a local variable.
2265 @item SYMBOL_LOC_TYPEDEF
2266 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
2269 @item SYMBOL_LOC_BLOCK
2272 @item SYMBOL_LOC_CONST_BYTES
2273 Value is a byte-sequence.
2275 @item SYMBOL_LOC_UNRESOLVED
2276 Value is at a fixed address, but the address of the variable has to be
2277 determined from the minimal symbol table whenever the variable is
2280 @item SYMBOL_LOC_OPTIMIZED_OUT
2281 The value does not actually exist in the program.
2283 @item SYMBOL_LOC_COMPUTED
2284 The value's address is a computed location.
2287 @node Symbol Tables In Guile
2288 @subsubsection Symbol table representation in Guile.
2290 @cindex symbol tables in guile
2291 @tindex <gdb:symtab>
2294 Access to symbol table data maintained by @value{GDBN} on the inferior
2295 is exposed to Guile via two objects: @code{<gdb:sal>} (symtab-and-line) and
2296 @code{<gdb:symtab>}. Symbol table and line data for a frame is returned
2297 from the @code{frame-find-sal} @code{<gdb:frame>} procedure.
2298 @xref{Frames In Guile}.
2300 For more information on @value{GDBN}'s symbol table management, see
2301 @ref{Symbols, ,Examining the Symbol Table}.
2303 The following symtab-related procedures are provided by the
2304 @code{(gdb)} module:
2306 @deffn {Scheme Procedure} symtab? object
2307 Return @code{#t} if @var{object} is an object of type @code{<gdb:symtab>}.
2308 Otherwise return @code{#f}.
2311 @deffn {Scheme Procedure} symtab-valid? symtab
2312 Return @code{#t} if the @code{<gdb:symtab>} object is valid,
2313 @code{#f} if not. A @code{<gdb:symtab>} object becomes invalid when
2314 the symbol table it refers to no longer exists in @value{GDBN}.
2315 All other @code{<gdb:symtab>} procedures will throw an exception
2316 if it is invalid at the time the procedure is called.
2319 @deffn {Scheme Procedure} symtab-filename symtab
2320 Return the symbol table's source filename.
2323 @deffn {Scheme Procedure} symtab-fullname symtab
2324 Return the symbol table's source absolute file name.
2327 @deffn {Scheme Procedure} symtab-objfile symtab
2328 Return the symbol table's backing object file. @xref{Objfiles In Guile}.
2331 @deffn {Scheme Procedure} symtab-global-block symtab
2332 Return the global block of the underlying symbol table.
2333 @xref{Blocks In Guile}.
2336 @deffn {Scheme Procedure} symtab-static-block symtab
2337 Return the static block of the underlying symbol table.
2338 @xref{Blocks In Guile}.
2341 The following symtab-and-line-related procedures are provided by the
2342 @code{(gdb)} module:
2344 @deffn {Scheme Procedure} sal? object
2345 Return @code{#t} if @var{object} is an object of type @code{<gdb:sal>}.
2346 Otherwise return @code{#f}.
2349 @deffn {Scheme Procedure} sal-valid? sal
2350 Return @code{#t} if @var{sal} is valid, @code{#f} if not.
2351 A @code{<gdb:sal>} object becomes invalid when the Symbol table object
2352 it refers to no longer exists in @value{GDBN}. All other
2353 @code{<gdb:sal>} procedures will throw an exception if it is
2354 invalid at the time the procedure is called.
2357 @deffn {Scheme Procedure} sal-symtab sal
2358 Return the symbol table object (@code{<gdb:symtab>}) for @var{sal}.
2361 @deffn {Scheme Procedure} sal-line sal
2362 Return the line number for @var{sal}.
2365 @deffn {Scheme Procedure} sal-pc sal
2366 Return the start of the address range occupied by code for @var{sal}.
2369 @deffn {Scheme Procedure} sal-last sal
2370 Return the end of the address range occupied by code for @var{sal}.
2373 @deffn {Scheme Procedure} find-pc-line pc
2374 Return the @code{<gdb:sal>} object corresponding to the @var{pc} value.
2375 If an invalid value of @var{pc} is passed as an argument, then the
2376 @code{symtab} and @code{line} attributes of the returned @code{<gdb:sal>}
2377 object will be @code{#f} and 0 respectively.
2380 @node Breakpoints In Guile
2381 @subsubsection Manipulating breakpoints using Guile
2383 @cindex breakpoints in guile
2384 @tindex <gdb:breakpoint>
2386 Breakpoints in Guile are represented by objects of type
2387 @code{<gdb:breakpoint>}.
2389 The following breakpoint-related procedures are provided by the
2390 @code{(gdb)} module:
2392 @c TODO: line length
2393 @deffn {Scheme Procedure} create-breakpoint! location @r{[}#:type type@r{]} @r{[}#:wp-class wp-class@r{]} @r{[}#:internal internal@r{]}
2394 Create a new breakpoint. @var{spec} is a string naming the
2395 location of the breakpoint, or an expression that defines a watchpoint.
2396 The contents can be any location recognized by the @code{break} command,
2397 or in the case of a watchpoint, by the @code{watch} command.
2399 The optional @var{type} denotes the breakpoint to create.
2400 This argument can be either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}.
2401 @var{type} defaults to @code{BP_BREAKPOINT}.
2403 The optional @var{wp-class} argument defines the class of watchpoint to
2404 create, if @var{type} is @code{BP_WATCHPOINT}. If a watchpoint class is
2405 not provided, it is assumed to be a @code{WP_WRITE} class.
2407 The optional @var{internal} argument allows the breakpoint to become
2408 invisible to the user. The breakpoint will neither be reported when
2409 created, nor will it be listed in the output from @code{info breakpoints}
2410 (but will be listed with the @code{maint info breakpoints} command).
2411 If an internal flag is not provided, the breakpoint is visible
2414 When a watchpoint is created, @value{GDBN} will try to create a
2415 hardware assisted watchpoint. If successful, the type of the watchpoint
2416 is changed from @code{BP_WATCHPOINT} to @code{BP_HARDWARE_WATCHPOINT}
2417 for @code{WP_WRITE}, @code{BP_READ_WATCHPOINT} for @code{WP_READ},
2418 and @code{BP_ACCESS_WATCHPOINT} for @code{WP_ACCESS}.
2419 If not successful, the type of the watchpoint is left as @code{WP_WATCHPOINT}.
2421 The available types are represented by constants defined in the @code{gdb}
2426 Normal code breakpoint.
2429 Watchpoint breakpoint.
2431 @item BP_HARDWARE_WATCHPOINT
2432 Hardware assisted watchpoint.
2433 This value cannot be specified when creating the breakpoint.
2435 @item BP_READ_WATCHPOINT
2436 Hardware assisted read watchpoint.
2437 This value cannot be specified when creating the breakpoint.
2439 @item BP_ACCESS_WATCHPOINT
2440 Hardware assisted access watchpoint.
2441 This value cannot be specified when creating the breakpoint.
2444 The available watchpoint types represented by constants are defined in the
2445 @code{(gdb)} module:
2449 Read only watchpoint.
2452 Write only watchpoint.
2455 Read/Write watchpoint.
2460 @deffn {Scheme Procedure} breakpoint-delete! breakpoint
2461 Permanently delete @var{breakpoint}. This also invalidates the
2462 Guile @var{breakpoint} object. Any further attempt to access the
2463 object will throw an exception.
2466 @deffn {Scheme Procedure} breakpoints
2467 Return a list of all breakpoints.
2468 Each element of the list is a @code{<gdb:breakpoint>} object.
2471 @deffn {Scheme Procedure} breakpoint? object
2472 Return @code{#t} if @var{object} is a @code{<gdb:breakpoint>} object,
2473 and @code{#f} otherwise.
2476 @deffn {Scheme Procedure} breakpoint-valid? breakpoint
2477 Return @code{#t} if @var{breakpoint} is valid, @code{#f} otherwise.
2478 A @code{<gdb:breakpoint>} object can become invalid
2479 if the user deletes the breakpoint. In this case, the object still
2480 exists, but the underlying breakpoint does not. In the cases of
2481 watchpoint scope, the watchpoint remains valid even if execution of the
2482 inferior leaves the scope of that watchpoint.
2485 @deffn {Scheme Procedure} breakpoint-number breakpoint
2486 Return the breakpoint's number --- the identifier used by
2487 the user to manipulate the breakpoint.
2490 @deffn {Scheme Procedure} breakpoint-type breakpoint
2491 Return the breakpoint's type --- the identifier used to
2492 determine the actual breakpoint type or use-case.
2495 @deffn {Scheme Procedure} breakpoint-visible? breakpoint
2496 Return @code{#t} if the breakpoint is visible to the user
2497 when hit, or when the @samp{info breakpoints} command is run.
2498 Otherwise return @code{#f}.
2501 @deffn {Scheme Procedure} breakpoint-location breakpoint
2502 Return the location of the breakpoint, as specified by
2503 the user. It is a string. If the breakpoint does not have a location
2504 (that is, it is a watchpoint) return @code{#f}.
2507 @deffn {Scheme Procedure} breakpoint-expression breakpoint
2508 Return the breakpoint expression, as specified by the user. It is a string.
2509 If the breakpoint does not have an expression (the breakpoint is not a
2510 watchpoint) return @code{#f}.
2513 @deffn {Scheme Procedure} breakpoint-enabled? breakpoint
2514 Return @code{#t} if the breakpoint is enabled, and @code{#f} otherwise.
2517 @deffn {Scheme Procedure} set-breakpoint-enabled! breakpoint flag
2518 Set the enabled state of @var{breakpoint} to @var{flag}.
2519 If flag is @code{#f} it is disabled, otherwise it is enabled.
2522 @deffn {Scheme Procedure} breakpoint-silent? breakpoint
2523 Return @code{#t} if the breakpoint is silent, and @code{#f} otherwise.
2525 Note that a breakpoint can also be silent if it has commands and the
2526 first command is @code{silent}. This is not reported by the
2527 @code{silent} attribute.
2530 @deffn {Scheme Procedure} set-breakpoint-silent! breakpoint flag
2531 Set the silent state of @var{breakpoint} to @var{flag}.
2532 If flag is @code{#f} the breakpoint is made silent,
2533 otherwise it is made non-silent (or noisy).
2536 @deffn {Scheme Procedure} breakpoint-ignore-count breakpoint
2537 Return the ignore count for @var{breakpoint}.
2540 @deffn {Scheme Procedure} set-breakpoint-ignore-count! breakpoint count
2541 Set the ignore count for @var{breakpoint} to @var{count}.
2544 @deffn {Scheme Procedure} breakpoint-hit-count breakpoint
2545 Return hit count of @var{breakpoint}.
2548 @deffn {Scheme Procedure} set-breakpoint-hit-count! breakpoint count
2549 Set the hit count of @var{breakpoint} to @var{count}.
2550 At present, @var{count} must be zero.
2553 @deffn {Scheme Procedure} breakpoint-thread breakpoint
2554 Return the thread-id for thread-specific breakpoint @var{breakpoint}.
2555 Return #f if @var{breakpoint} is not thread-specific.
2558 @deffn {Scheme Procedure} set-breakpoint-thread! breakpoint thread-id|#f
2559 Set the thread-id for @var{breakpoint} to @var{thread-id}.
2560 If set to @code{#f}, the breakpoint is no longer thread-specific.
2563 @deffn {Scheme Procedure} breakpoint-task breakpoint
2564 If the breakpoint is Ada task-specific, return the Ada task id.
2565 If the breakpoint is not task-specific (or the underlying
2566 language is not Ada), return @code{#f}.
2569 @deffn {Scheme Procedure} set-breakpoint-task! breakpoint task
2570 Set the Ada task of @var{breakpoint} to @var{task}.
2571 If set to @code{#f}, the breakpoint is no longer task-specific.
2574 @deffn {Scheme Procedure} breakpoint-condition breakpoint
2575 Return the condition of @var{breakpoint}, as specified by the user.
2576 It is a string. If there is no condition, return @code{#f}.
2579 @deffn {Scheme Procedure} set-breakpoint-condition! breakpoint condition
2580 Set the condition of @var{breakpoint} to @var{condition},
2581 which must be a string. If set to @code{#f} then the breakpoint
2582 becomes unconditional.
2585 @deffn {Scheme Procedure} breakpoint-stop breakpoint
2586 Return the stop predicate of @var{breakpoint}.
2587 See @code{set-breakpoint-stop!} below in this section.
2590 @deffn {Scheme Procedure} set-breakpoint-stop! breakpoint procedure|#f
2591 Set the stop predicate of @var{breakpoint}.
2592 @var{procedure} takes one argument: the <gdb:breakpoint> object.
2593 If this predicate is set to a procedure then it is invoked whenever
2594 the inferior reaches this breakpoint. If it returns @code{#t},
2595 or any non-@code{#f} value, then the inferior is stopped,
2596 otherwise the inferior will continue.
2598 If there are multiple breakpoints at the same location with a
2599 @code{stop} predicate, each one will be called regardless of the
2600 return status of the previous. This ensures that all @code{stop}
2601 predicates have a chance to execute at that location. In this scenario
2602 if one of the methods returns @code{#t} but the others return
2603 @code{#f}, the inferior will still be stopped.
2605 You should not alter the execution state of the inferior (i.e.@:, step,
2606 next, etc.), alter the current frame context (i.e.@:, change the current
2607 active frame), or alter, add or delete any breakpoint. As a general
2608 rule, you should not alter any data within @value{GDBN} or the inferior
2611 Example @code{stop} implementation:
2614 (define (my-stop? bkpt)
2615 (let ((int-val (parse-and-eval "foo")))
2616 (value=? int-val 3)))
2617 (define bkpt (create-breakpoint! "main.c:42"))
2618 (set-breakpoint-stop! bkpt my-stop?)
2622 @deffn {Scheme Procedure} breakpoint-commands breakpoint
2623 Return the commands attached to @var{breakpoint} as a string,
2624 or @code{#f} if there are none.
2627 @node Lazy Strings In Guile
2628 @subsubsection Guile representation of lazy strings.
2630 @cindex lazy strings in guile
2631 @tindex <gdb:lazy-string>
2633 A @dfn{lazy string} is a string whose contents is not retrieved or
2634 encoded until it is needed.
2636 A @code{<gdb:lazy-string>} is represented in @value{GDBN} as an
2637 @code{address} that points to a region of memory, an @code{encoding}
2638 that will be used to encode that region of memory, and a @code{length}
2639 to delimit the region of memory that represents the string. The
2640 difference between a @code{<gdb:lazy-string>} and a string wrapped within
2641 a @code{<gdb:value>} is that a @code{<gdb:lazy-string>} will be treated
2642 differently by @value{GDBN} when printing. A @code{<gdb:lazy-string>} is
2643 retrieved and encoded during printing, while a @code{<gdb:value>}
2644 wrapping a string is immediately retrieved and encoded on creation.
2646 The following lazy-string-related procedures are provided by the
2647 @code{(gdb)} module:
2649 @deffn {Scheme Procedure} lazy-string? object
2650 Return @code{#t} if @var{object} is an object of type @code{<gdb:lazy-string>}.
2651 Otherwise return @code{#f}.
2654 @deffn {Scheme Procedure} lazy-string-address lazy-sring
2655 Return the address of @var{lazy-string}.
2658 @deffn {Scheme Procedure} lazy-string-length lazy-string
2659 Return the length of @var{lazy-string} in characters. If the
2660 length is -1, then the string will be fetched and encoded up to the
2661 first null of appropriate width.
2664 @deffn {Scheme Procedure} lazy-string-encoding lazy-string
2665 Return the encoding that will be applied to @var{lazy-string}
2666 when the string is printed by @value{GDBN}. If the encoding is not
2667 set, or contains an empty string, then @value{GDBN} will select the
2668 most appropriate encoding when the string is printed.
2671 @deffn {Scheme Procedure} lazy-string-type lazy-string
2672 Return the type that is represented by @var{lazy-string}'s type.
2673 For a lazy string this will always be a pointer type. To
2674 resolve this to the lazy string's character type, use @code{type-target-type}.
2675 @xref{Types In Guile}.
2678 @deffn {Scheme Procedure} lazy-string->value lazy-string
2679 Convert the @code{<gdb:lazy-string>} to a @code{<gdb:value>}. This value
2680 will point to the string in memory, but will lose all the delayed
2681 retrieval, encoding and handling that @value{GDBN} applies to a
2682 @code{<gdb:lazy-string>}.
2685 @node Architectures In Guile
2686 @subsubsection Guile representation of architectures
2688 @cindex guile architectures
2691 @value{GDBN} uses architecture specific parameters and artifacts in a
2692 number of its various computations. An architecture is represented
2693 by an instance of the @code{<gdb:arch>} class.
2695 The following architecture-related procedures are provided by the
2696 @code{(gdb)} module:
2698 @deffn {Scheme Procedure} arch? object
2699 Return @code{#t} if @var{object} is an object of type @code{<gdb:arch>}.
2700 Otherwise return @code{#f}.
2703 @deffn {Scheme Procedure} current-arch
2704 Return the current architecture as a @code{<gdb:arch>} object.
2707 @deffn {Scheme Procedure} arch-name arch
2708 Return the name (string value) of @code{<gdb:arch>} @var{arch}.
2711 @deffn {Scheme Procedure} arch-charset arch
2712 Return name of target character set of @code{<gdb:arch>} @var{arch}.
2715 @deffn {Scheme Procedure} arch-wide-charset
2716 Return name of target wide character set of @code{<gdb:arch>} @var{arch}.
2719 Each architecture provides a set of predefined types, obtained by
2720 the following functions.
2722 @deffn {Scheme Procedure} arch-void-type arch
2723 Return the @code{<gdb:type>} object for a @code{void} type
2724 of architecture @var{arch}.
2727 @deffn {Scheme Procedure} arch-char-type arch
2728 Return the @code{<gdb:type>} object for a @code{char} type
2729 of architecture @var{arch}.
2732 @deffn {Scheme Procedure} arch-short-type arch
2733 Return the @code{<gdb:type>} object for a @code{short} type
2734 of architecture @var{arch}.
2737 @deffn {Scheme Procedure} arch-int-type arch
2738 Return the @code{<gdb:type>} object for an @code{int} type
2739 of architecture @var{arch}.
2742 @deffn {Scheme Procedure} arch-long-type arch
2743 Return the @code{<gdb:type>} object for a @code{long} type
2744 of architecture @var{arch}.
2747 @deffn {Scheme Procedure} arch-schar-type arch
2748 Return the @code{<gdb:type>} object for a @code{signed char} type
2749 of architecture @var{arch}.
2752 @deffn {Scheme Procedure} arch-uchar-type arch
2753 Return the @code{<gdb:type>} object for an @code{unsigned char} type
2754 of architecture @var{arch}.
2757 @deffn {Scheme Procedure} arch-ushort-type arch
2758 Return the @code{<gdb:type>} object for an @code{unsigned short} type
2759 of architecture @var{arch}.
2762 @deffn {Scheme Procedure} arch-uint-type arch
2763 Return the @code{<gdb:type>} object for an @code{unsigned int} type
2764 of architecture @var{arch}.
2767 @deffn {Scheme Procedure} arch-ulong-type arch
2768 Return the @code{<gdb:type>} object for an @code{unsigned long} type
2769 of architecture @var{arch}.
2772 @deffn {Scheme Procedure} arch-float-type arch
2773 Return the @code{<gdb:type>} object for a @code{float} type
2774 of architecture @var{arch}.
2777 @deffn {Scheme Procedure} arch-double-type arch
2778 Return the @code{<gdb:type>} object for a @code{double} type
2779 of architecture @var{arch}.
2782 @deffn {Scheme Procedure} arch-longdouble-type arch
2783 Return the @code{<gdb:type>} object for a @code{long double} type
2784 of architecture @var{arch}.
2787 @deffn {Scheme Procedure} arch-bool-type arch
2788 Return the @code{<gdb:type>} object for a @code{bool} type
2789 of architecture @var{arch}.
2792 @deffn {Scheme Procedure} arch-longlong-type arch
2793 Return the @code{<gdb:type>} object for a @code{long long} type
2794 of architecture @var{arch}.
2797 @deffn {Scheme Procedure} arch-ulonglong-type arch
2798 Return the @code{<gdb:type>} object for an @code{unsigned long long} type
2799 of architecture @var{arch}.
2802 @deffn {Scheme Procedure} arch-int8-type arch
2803 Return the @code{<gdb:type>} object for an @code{int8} type
2804 of architecture @var{arch}.
2807 @deffn {Scheme Procedure} arch-uint8-type arch
2808 Return the @code{<gdb:type>} object for a @code{uint8} type
2809 of architecture @var{arch}.
2812 @deffn {Scheme Procedure} arch-int16-type arch
2813 Return the @code{<gdb:type>} object for an @code{int16} type
2814 of architecture @var{arch}.
2817 @deffn {Scheme Procedure} arch-uint16-type arch
2818 Return the @code{<gdb:type>} object for a @code{uint16} type
2819 of architecture @var{arch}.
2822 @deffn {Scheme Procedure} arch-int32-type arch
2823 Return the @code{<gdb:type>} object for an @code{int32} type
2824 of architecture @var{arch}.
2827 @deffn {Scheme Procedure} arch-uint32-type arch
2828 Return the @code{<gdb:type>} object for a @code{uint32} type
2829 of architecture @var{arch}.
2832 @deffn {Scheme Procedure} arch-int64-type arch
2833 Return the @code{<gdb:type>} object for an @code{int64} type
2834 of architecture @var{arch}.
2837 @deffn {Scheme Procedure} arch-uint64-type arch
2838 Return the @code{<gdb:type>} object for a @code{uint64} type
2839 of architecture @var{arch}.
2845 (gdb) guile (type-name (arch-uchar-type (current-arch)))
2849 @node Disassembly In Guile
2850 @subsubsection Disassembly In Guile
2852 The disassembler can be invoked from Scheme code.
2853 Furthermore, the disassembler can take a Guile port as input,
2854 allowing one to disassemble from any source, and not just target memory.
2856 @c TODO: line length
2857 @deffn {Scheme Procedure} arch-disassemble arch start-pc @r{[}#:port port@r{]} @r{[}#:offset offset@r{]} @r{[}#:size size@r{]} @r{[}#:count count@r{]})
2858 Return a list of disassembled instructions starting from the memory
2859 address @var{start-pc}.
2861 The optional argument @var{port} specifies the input port to read bytes from.
2862 If @var{port} is @code{#f} then bytes are read from target memory.
2864 The optional argument @var{offset} specifies the address offset of the
2865 first byte in @var{port}. This is useful, for example, when @var{port}
2866 specifies a @samp{bytevector} and you want the bytevector to be disassembled
2867 as if it came from that address. The @var{start-pc} passed to the reader
2868 for @var{port} is offset by the same amount.
2872 (gdb) guile (use-modules (rnrs io ports))
2873 (gdb) guile (define pc (value->integer (parse-and-eval "$pc")))
2874 (gdb) guile (define mem (open-memory #:start pc))
2875 (gdb) guile (define bv (get-bytevector-n mem 10))
2876 (gdb) guile (define bv-port (open-bytevector-input-port bv))
2877 (gdb) guile (define arch (current-arch))
2878 (gdb) guile (arch-disassemble arch pc #:port bv-port #:offset pc)
2879 (((address . 4195516) (asm . "mov $0x4005c8,%edi") (length . 5)))
2882 The optional arguments @var{size} and
2883 @var{count} determine the number of instructions in the returned list.
2884 If either @var{size} or @var{count} is specified as zero, then
2885 no instructions are disassembled and an empty list is returned.
2886 If both the optional arguments @var{size} and @var{count} are
2887 specified, then a list of at most @var{count} disassembled instructions
2888 whose start address falls in the closed memory address interval from
2889 @var{start-pc} to (@var{start-pc} + @var{size} - 1) are returned.
2890 If @var{size} is not specified, but @var{count} is specified,
2891 then @var{count} number of instructions starting from the address
2892 @var{start-pc} are returned. If @var{count} is not specified but
2893 @var{size} is specified, then all instructions whose start address
2894 falls in the closed memory address interval from @var{start-pc} to
2895 (@var{start-pc} + @var{size} - 1) are returned.
2896 If neither @var{size} nor @var{count} are specified, then a single
2897 instruction at @var{start-pc} is returned.
2899 Each element of the returned list is an alist (associative list)
2900 with the following keys:
2905 The value corresponding to this key is a Guile integer of
2906 the memory address of the instruction.
2909 The value corresponding to this key is a string value which represents
2910 the instruction with assembly language mnemonics. The assembly
2911 language flavor used is the same as that specified by the current CLI
2912 variable @code{disassembly-flavor}. @xref{Machine Code}.
2915 The value corresponding to this key is the length of the instruction in bytes.
2920 @node I/O Ports in Guile
2921 @subsubsection I/O Ports in Guile
2923 @deffn {Scheme Procedure} input-port
2924 Return @value{GDBN}'s input port as a Guile port object.
2927 @deffn {Scheme Procedure} output-port
2928 Return @value{GDBN}'s output port as a Guile port object.
2931 @deffn {Scheme Procedure} error-port
2932 Return @value{GDBN}'s error port as a Guile port object.
2935 @deffn {Scheme Procedure} stdio-port? object
2936 Return @code{#t} if @var{object} is a @value{GDBN} stdio port.
2937 Otherwise return @code{#f}.
2940 @node Memory Ports in Guile
2941 @subsubsection Memory Ports in Guile
2943 @value{GDBN} provides a @code{port} interface to target memory.
2944 This allows Guile code to read/write target memory using Guile's port and
2945 bytevector functionality. The main routine is @code{open-memory} which
2946 returns a port object. One can then read/write memory using that object.
2948 @deffn {Scheme Procedure} open-memory @r{[}#:mode mode{]} @r{[}#:start address{]} @r{[}#:size size{]}
2949 Return a port object that can be used for reading and writing memory.
2950 @var{mode} is the standard mode argument to Guile port open routines,
2951 except that it is restricted to one of @samp{"r"}, @samp{"w"}, or @samp{"r+"}.
2952 For compatibility @samp{"b"} (binary) may also be present,
2953 but we ignore it: memory ports are binary only.
2954 The default is @samp{"r"}, read-only.
2956 The chunk of memory that can be accessed can be bounded.
2957 If both @var{start} and @var{size} are unspecified, all of memory can be
2958 accessed. If only @var{start} is specified, all of memory from that point
2959 on can be accessed. If only @var{size} if specified, all memory in the
2960 range [0,@var{size}) can be accessed. If both are specified, all memory
2961 in the rane [@var{start},@var{start}+@var{size}) can be accessed.
2964 @deffn {Scheme Procedure} memory-port?
2965 Return @code{#t} if @var{object} is an object of type @code{<gdb:memory-port>}.
2966 Otherwise return @code{#f}.
2969 @deffn {Scheme Procedure} memory-port-range memory-port
2970 Return the range of @code{<gdb:memory-port>} @var{memory-port} as a list
2971 of two elements: @code{(start end)}. The range is @var{start} to @var{end}
2975 @deffn {Scheme Procedure} memory-port-read-buffer-size memory-port
2976 Return the size of the read buffer of @code{<gdb:memory-port>}
2980 @deffn {Scheme Procedure} set-memory-port-read-buffer-size! memory-port size
2981 Set the size of the read buffer of @code{<gdb:memory-port>}
2982 @var{memory-port} to @var{size}. The result is unspecified.
2985 @deffn {Scheme Procedure} memory-port-write-buffer-size memory-port
2986 Return the size of the write buffer of @code{<gdb:memory-port>}
2990 @deffn {Scheme Procedure} set-memory-port-write-buffer-size! memory-port size
2991 Set the size of the write buffer of @code{<gdb:memory-port>}
2992 @var{memory-port} to @var{size}. The result is unspecified.
2995 A memory port is closed like any other port, with @code{close-port}.
2997 Combined with Guile's @code{bytevectors}, memory ports provide a lot
2998 of utility. For example, to fill a buffer of 10 integers in memory,
2999 one can do something like the following.
3002 ;; In the program: int buffer[10];
3003 (use-modules (rnrs bytevectors))
3004 (use-modules (rnrs io ports))
3005 (define addr (parse-and-eval "buffer"))
3007 (define byte-size (* n 4))
3008 (define mem-port (open-memory #:mode "r+" #:start
3009 (value->integer addr) #:size byte-size))
3010 (define byte-vec (make-bytevector byte-size))
3013 (bytevector-s32-native-set! byte-vec (* i 4) (* i 42)))
3014 (put-bytevector mem-port byte-vec)
3015 (close-port mem-port)
3018 @node Iterators In Guile
3019 @subsubsection Iterators In Guile
3021 @cindex guile iterators
3022 @tindex <gdb:iterator>
3024 A simple iterator facility is provided to allow, for example,
3025 iterating over the set of program symbols without having to first
3026 construct a list of all of them. A useful contribution would be
3027 to add support for SRFI 41 and SRFI 45.
3029 @deffn {Scheme Procedure} make-iterator object progress next!
3030 A @code{<gdb:iterator>} object is constructed with the @code{make-iterator}
3031 procedure. It takes three arguments: the object to be iterated over,
3032 an object to record the progress of the iteration, and a procedure to
3033 return the next element in the iteration, or an implementation chosen value
3034 to denote the end of iteration.
3036 By convention, end of iteration is marked with @code{(end-of-iteration)},
3037 and may be tested with the @code{end-of-iteration?} predicate.
3038 The result of @code{(end-of-iteration)} is chosen so that it is not
3039 otherwise used by the @code{(gdb)} module. If you are using
3040 @code{<gdb:iterator>} in your own code it is your responsibility to
3041 maintain this invariant.
3043 A trivial example for illustration's sake:
3046 (use-modules (gdb iterator))
3047 (define my-list (list 1 2 3))
3049 (make-iterator my-list my-list
3051 (let ((l (iterator-progress iter)))
3055 (set-iterator-progress! iter (cdr l))
3059 Here is a slightly more realistic example, which computes a list of all the
3060 functions in @code{my-global-block}.
3063 (use-modules (gdb iterator))
3064 (define this-sal (find-pc-line (frame-pc (selected-frame))))
3065 (define this-symtab (sal-symtab this-sal))
3066 (define this-global-block (symtab-global-block this-symtab))
3067 (define syms-iter (make-block-symbols-iterator this-global-block))
3068 (define functions (iterator-filter symbol-function? syms-iter))
3072 @deffn {Scheme Procedure} iterator? object
3073 Return @code{#t} if @var{object} is a @code{<gdb:iterator>} object.
3074 Otherwise return @code{#f}.
3077 @deffn {Scheme Procedure} iterator-object iterator
3078 Return the first argument that was passed to @code{make-iterator}.
3079 This is the object being iterated over.
3082 @deffn {Scheme Procedure} iterator-progress iterator
3083 Return the object tracking iteration progress.
3086 @deffn {Scheme Procedure} set-iterator-progress! iterator new-value
3087 Set the object tracking iteration progress.
3090 @deffn {Scheme Procedure} iterator-next! iterator
3091 Invoke the procedure that was the third argument to @code{make-iterator},
3092 passing it one argument, the @code{<gdb:iterator>} object.
3093 The result is either the next element in the iteration, or an end
3094 marker as implemented by the @code{next!} procedure.
3095 By convention the end marker is the result of @code{(end-of-iteration)}.
3098 @deffn {Scheme Procedure} end-of-iteration
3099 Return the Scheme object that denotes end of iteration.
3102 @deffn {Scheme Procedure} end-of-iteration? object
3103 Return @code{#t} if @var{object} is the end of iteration marker.
3104 Otherwise return @code{#f}.
3107 These functions are provided by the @code{(gdb iterator)} module to
3108 assist in using iterators.
3110 @deffn {Scheme Procedure} make-list-iterator list
3111 Return a @code{<gdb:iterator>} object that will iterate over @var{list}.
3114 @deffn {Scheme Procedure} iterator->list iterator
3115 Return the elements pointed to by @var{iterator} as a list.
3118 @deffn {Scheme Procedure} iterator-map proc iterator
3119 Return the list of objects obtained by applying @var{proc} to the object
3120 pointed to by @var{iterator} and to each subsequent object.
3123 @deffn {Scheme Procedure} iterator-for-each proc iterator
3124 Apply @var{proc} to each element pointed to by @var{iterator}.
3125 The result is unspecified.
3128 @deffn {Scheme Procedure} iterator-filter pred iterator
3129 Return the list of elements pointed to by @var{iterator} that satisfy
3133 @deffn {Scheme Procedure} iterator-until pred iterator
3134 Run @var{iterator} until the result of @code{(pred element)} is true
3135 and return that as the result. Otherwise return @code{#f}.
3138 @node Guile Auto-loading
3139 @subsection Guile Auto-loading
3140 @cindex guile auto-loading
3142 When a new object file is read (for example, due to the @code{file}
3143 command, or because the inferior has loaded a shared library),
3144 @value{GDBN} will look for Guile support scripts in two ways:
3145 @file{@var{objfile}-gdb.scm} and the @code{.debug_gdb_scripts} section.
3146 @xref{Auto-loading extensions}.
3148 The auto-loading feature is useful for supplying application-specific
3149 debugging commands and scripts.
3151 Auto-loading can be enabled or disabled,
3152 and the list of auto-loaded scripts can be printed.
3155 @anchor{set auto-load guile-scripts}
3156 @kindex set auto-load guile-scripts
3157 @item set auto-load guile-scripts [on|off]
3158 Enable or disable the auto-loading of Guile scripts.
3160 @anchor{show auto-load guile-scripts}
3161 @kindex show auto-load guile-scripts
3162 @item show auto-load guile-scripts
3163 Show whether auto-loading of Guile scripts is enabled or disabled.
3165 @anchor{info auto-load guile-scripts}
3166 @kindex info auto-load guile-scripts
3167 @cindex print list of auto-loaded Guile scripts
3168 @item info auto-load guile-scripts [@var{regexp}]
3169 Print the list of all Guile scripts that @value{GDBN} auto-loaded.
3171 Also printed is the list of Guile scripts that were mentioned in
3172 the @code{.debug_gdb_scripts} section and were not found.
3173 This is useful because their names are not printed when @value{GDBN}
3174 tries to load them and fails. There may be many of them, and printing
3175 an error message for each one is problematic.
3177 If @var{regexp} is supplied only Guile scripts with matching names are printed.
3182 (gdb) info auto-load guile-scripts
3184 Yes scm-section-script.scm
3185 full name: /tmp/scm-section-script.scm
3186 No my-foo-pretty-printers.scm
3190 When reading an auto-loaded file, @value{GDBN} sets the
3191 @dfn{current objfile}. This is available via the @code{current-objfile}
3192 procedure (@pxref{Objfiles In Guile}). This can be useful for
3193 registering objfile-specific pretty-printers.
3196 @subsection Guile Modules
3197 @cindex guile modules
3199 @value{GDBN} comes with several modules to assist writing Guile code.
3202 * Guile Printing Module:: Building and registering pretty-printers
3203 * Guile Types Module:: Utilities for working with types
3206 @node Guile Printing Module
3207 @subsubsection Guile Printing Module
3209 This module provides a collection of utilities for working with
3215 (use-modules (gdb printing))
3218 @deffn {Scheme Procedure} prepend-pretty-printer! object printer
3219 Add @var{printer} to the front of the list of pretty-printers for
3220 @var{object}. @var{object} must either be a @code{<gdb:objfile>} object
3221 or @code{#f} in which case @var{printer} is added to the global list of
3225 @deffn {Scheme Procecure} append-pretty-printer! object printer
3226 Add @var{printer} to the end of the list of pretty-printers for
3227 @var{object}. @var{object} must either be a @code{<gdb:objfile>} object
3228 or @code{#f} in which case @var{printer} is added to the global list of
3232 @node Guile Types Module
3233 @subsubsection Guile Types Module
3235 This module provides a collection of utilities for working with
3236 @code{<gdb:type>} objects.
3241 (use-modules (gdb types))
3244 @deffn {Scheme Procedure} get-basic-type type
3245 Return @var{type} with const and volatile qualifiers stripped,
3246 and with typedefs and C@t{++} references converted to the underlying type.
3251 typedef const int const_int;
3253 const_int& foo_ref (foo);
3254 int main () @{ return 0; @}
3261 (gdb) guile (use-modules ((gdb) (gdb types)))
3262 (gdb) guile (define foo-ref (parse-and-eval "foo_ref"))
3263 (gdb) guile (get-basic-type (value-type foo-ref))
3268 @deffn {Scheme Procedure} type-has-field-deep? type field
3269 Return @code{#t} if @var{type}, assumed to be a type with fields
3270 (e.g., a structure or union), has field @var{field}.
3271 Otherwise return @code{#f}.
3272 This searches baseclasses, whereas @code{type-has-field?} does not.
3275 @deffn {Scheme Procedure} make-enum-hashtable enum-type
3276 Return a Guile hash table produced from @var{enum-type}.
3277 Elements in the hash table are referenced with @code{hashq-ref}.