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 (str-lookup-function pretty-printer value)
1549 (let ((tag (type-tag (value-type value))))
1551 (string-prefix? "std::string<" tag)
1552 (make-my-string-printer value))))
1555 Then to register this printer in the global printer list:
1558 (append-pretty-printer!
1559 (make-pretty-printer "my-string" str-lookup-function))
1562 The example lookup function extracts the value's type, and attempts to
1563 match it to a type that it can pretty-print. If it is a type the
1564 printer can pretty-print, it will return a <gdb:pretty-printer-worker> object.
1565 If not, it returns @code{#f}.
1567 We recommend that you put your core pretty-printers into a Guile
1568 package. If your pretty-printers are for use with a library, we
1569 further recommend embedding a version number into the package name.
1570 This practice will enable @value{GDBN} to load multiple versions of
1571 your pretty-printers at the same time, because they will have
1574 You should write auto-loaded code (@pxref{Guile Auto-loading}) such that it
1575 can be evaluated multiple times without changing its meaning. An
1576 ideal auto-load file will consist solely of @code{import}s of your
1577 printer modules, followed by a call to a register pretty-printers with
1578 the current objfile.
1580 Taken as a whole, this approach will scale nicely to multiple
1581 inferiors, each potentially using a different library version.
1582 Embedding a version number in the Guile package name will ensure that
1583 @value{GDBN} is able to load both sets of printers simultaneously.
1584 Then, because the search for pretty-printers is done by objfile, and
1585 because your auto-loaded code took care to register your library's
1586 printers with a specific objfile, @value{GDBN} will find the correct
1587 printers for the specific version of the library used by each
1590 To continue the @code{my::string} example,
1591 this code might appear in @code{(my-project my-library v1)}:
1594 (use-modules ((gdb)))
1595 (define (register-printers objfile)
1596 (append-objfile-pretty-printer!
1597 (make-pretty-printer "my-string" str-lookup-function)))
1601 And then the corresponding contents of the auto-load file would be:
1604 (use-modules ((gdb) (my-project my-library v1)))
1605 (register-printers (current-objfile))
1608 The previous example illustrates a basic pretty-printer.
1609 There are a few things that can be improved on.
1610 The printer only handles one type, whereas a library typically has
1611 several types. One could install a lookup function for each desired type
1612 in the library, but one could also have a single lookup function recognize
1613 several types. The latter is the conventional way this is handled.
1614 If a pretty-printer can handle multiple data types, then its
1615 @dfn{subprinters} are the printers for the individual data types.
1617 The @code{(gdb printing)} module provides a formal way of solving this
1618 problem (@pxref{Guile Printing Module}).
1619 Here is another example that handles multiple types.
1621 These are the types we are going to pretty-print:
1624 struct foo @{ int a, b; @};
1625 struct bar @{ struct foo x, y; @};
1628 Here are the printers:
1631 (define (make-foo-printer value)
1632 "Print a foo object"
1633 (make-pretty-printer-worker
1636 (format #f "a=<~a> b=<~a>"
1637 (value-field value "a") (value-field value "a")))
1640 (define (make-bar-printer value)
1641 "Print a bar object"
1642 (make-pretty-printer-worker
1645 (format #f "x=<~a> y=<~a>"
1646 (value-field value "x") (value-field value "y")))
1650 This example doesn't need a lookup function, that is handled by the
1651 @code{(gdb printing)} module. Instead a function is provided to build up
1652 the object that handles the lookup.
1655 (use-modules ((gdb printing)))
1657 (define (build-pretty-printer)
1658 (let ((pp (make-pretty-printer-collection "my-library")))
1659 (pp-collection-add-tag-printer "foo" make-foo-printer)
1660 (pp-collection-add-tag-printer "bar" make-bar-printer)
1664 And here is the autoload support:
1667 (use-modules ((gdb) (my-library)))
1668 (append-objfile-pretty-printer! (current-objfile) (build-pretty-printer))
1671 Finally, when this printer is loaded into @value{GDBN}, here is the
1672 corresponding output of @samp{info pretty-printer}:
1675 (gdb) info pretty-printer
1682 @node Objfiles In Guile
1683 @subsubsection Objfiles In Guile
1685 @cindex objfiles in guile
1686 @tindex <gdb:objfile>
1687 @value{GDBN} loads symbols for an inferior from various
1688 symbol-containing files (@pxref{Files}). These include the primary
1689 executable file, any shared libraries used by the inferior, and any
1690 separate debug info files (@pxref{Separate Debug Files}).
1691 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
1693 Each objfile is represented as an object of type @code{<gdb:objfile>}.
1695 The following objfile-related procedures are provided by the
1696 @code{(gdb)} module:
1698 @deffn {Scheme Procedure} objfile? object
1699 Return @code{#t} if @var{object} is a @code{<gdb:objfile>} object.
1700 Otherwise return @code{#f}.
1703 @deffn {Scheme Procedure} objfile-valid? objfile
1704 Return @code{#t} if @var{objfile} is valid, @code{#f} if not.
1705 A @code{<gdb:objfile>} object can become invalid
1706 if the object file it refers to is not loaded in @value{GDBN} any
1707 longer. All other @code{<gdb:objfile>} procedures will throw an exception
1708 if it is invalid at the time the procedure is called.
1711 @deffn {Scheme Procedure} objfile-filename objfile
1712 Return the file name of @var{objfile} as a string.
1715 @deffn {Scheme Procedure} objfile-pretty-printers objfile
1716 Return the list of registered @code{<gdb:pretty-printer>} objects for
1717 @var{objfile}. @xref{Guile Pretty Printing API}, for more information.
1720 @deffn {Scheme Procedure} set-objfile-pretty-printers! objfile printer-list
1721 Set the list of registered @code{<gdb:pretty-printer>} objects for
1722 @var{objfile} to @var{printer-list}.
1723 @var{printer-list} must be a list of @code{<gdb:pretty-printer>} objects.
1724 @xref{Guile Pretty Printing API}, for more information.
1727 @deffn {Scheme Procedure} current-objfile
1728 When auto-loading a Guile script (@pxref{Guile Auto-loading}), @value{GDBN}
1729 sets the ``current objfile'' to the corresponding objfile. This
1730 function returns the current objfile. If there is no current objfile,
1731 this function returns @code{#f}.
1734 @deffn {Scheme Procedure} objfiles
1735 Return a list of all the objfiles in the current program space.
1738 @node Frames In Guile
1739 @subsubsection Accessing inferior stack frames from Guile.
1741 @cindex frames in guile
1742 When the debugged program stops, @value{GDBN} is able to analyze its call
1743 stack (@pxref{Frames,,Stack frames}). The @code{<gdb:frame>} class
1744 represents a frame in the stack. A @code{<gdb:frame>} object is only valid
1745 while its corresponding frame exists in the inferior's stack. If you try
1746 to use an invalid frame object, @value{GDBN} will throw a
1747 @code{gdb:invalid-object} exception (@pxref{Guile Exception Handling}).
1749 Two @code{<gdb:frame>} objects can be compared for equality with the
1750 @code{equal?} function, like:
1753 (@value{GDBP}) guile (equal? (newest-frame) (selected-frame))
1757 The following frame-related procedures are provided by the
1758 @code{(gdb)} module:
1760 @deffn {Scheme Procedure} frame? object
1761 Return @code{#t} if @var{object} is a @code{<gdb:frame>} object.
1762 Otherwise return @code{#f}.
1765 @deffn {Scheme Procedure} frame-valid? frame
1766 Returns @code{#t} if @var{frame} is valid, @code{#f} if not.
1767 A frame object can become invalid if the frame it refers to doesn't
1768 exist anymore in the inferior. All @code{<gdb:frame>} procedures will throw
1769 an exception if the frame is invalid at the time the procedure is called.
1772 @deffn {Scheme Procedure} frame-name frame
1773 Return the function name of @var{frame}, or @code{#f} if it can't be
1777 @deffn {Scheme Procedure} frame-arch frame
1778 Return the @code{<gdb:architecture>} object corresponding to @var{frame}'s
1779 architecture. @xref{Architectures In Guile}.
1782 @deffn {Scheme Procedure} frame-type frame
1783 Return the type of @var{frame}. The value can be one of:
1787 An ordinary stack frame.
1790 A fake stack frame that was created by @value{GDBN} when performing an
1791 inferior function call.
1794 A frame representing an inlined function. The function was inlined
1795 into a @code{NORMAL_FRAME} that is older than this one.
1797 @item TAILCALL_FRAME
1798 A frame representing a tail call. @xref{Tail Call Frames}.
1800 @item SIGTRAMP_FRAME
1801 A signal trampoline frame. This is the frame created by the OS when
1802 it calls into a signal handler.
1805 A fake stack frame representing a cross-architecture call.
1807 @item SENTINEL_FRAME
1808 This is like @code{NORMAL_FRAME}, but it is only used for the
1813 @deffn {Scheme Procedure} frame-unwind-stop-reason frame
1814 Return an integer representing the reason why it's not possible to find
1815 more frames toward the outermost frame. Use
1816 @code{unwind-stop-reason-string} to convert the value returned by this
1817 function to a string. The value can be one of:
1820 @item FRAME_UNWIND_NO_REASON
1821 No particular reason (older frames should be available).
1823 @item FRAME_UNWIND_NULL_ID
1824 The previous frame's analyzer returns an invalid result.
1826 @item FRAME_UNWIND_OUTERMOST
1827 This frame is the outermost.
1829 @item FRAME_UNWIND_UNAVAILABLE
1830 Cannot unwind further, because that would require knowing the
1831 values of registers or memory that have not been collected.
1833 @item FRAME_UNWIND_INNER_ID
1834 This frame ID looks like it ought to belong to a NEXT frame,
1835 but we got it for a PREV frame. Normally, this is a sign of
1836 unwinder failure. It could also indicate stack corruption.
1838 @item FRAME_UNWIND_SAME_ID
1839 This frame has the same ID as the previous one. That means
1840 that unwinding further would almost certainly give us another
1841 frame with exactly the same ID, so break the chain. Normally,
1842 this is a sign of unwinder failure. It could also indicate
1845 @item FRAME_UNWIND_NO_SAVED_PC
1846 The frame unwinder did not find any saved PC, but we needed
1847 one to unwind further.
1849 @item FRAME_UNWIND_FIRST_ERROR
1850 Any stop reason greater or equal to this value indicates some kind
1851 of error. This special value facilitates writing code that tests
1852 for errors in unwinding in a way that will work correctly even if
1853 the list of the other values is modified in future @value{GDBN}
1854 versions. Using it, you could write:
1857 (define reason (frame-unwind-stop-readon (selected-frame)))
1858 (define reason-str (unwind-stop-reason-string reason))
1859 (if (>= reason FRAME_UNWIND_FIRST_ERROR)
1860 (format #t "An error occured: ~s\n" reason-str))
1865 @deffn {Scheme Procedure} frame-pc frame
1866 Return the frame's resume address.
1869 @deffn {Scheme Procedure} frame-block frame
1870 Return the frame's code block as a @code{<gdb:block>} object.
1871 @xref{Blocks In Guile}.
1874 @deffn {Scheme Procedure} frame-function frame
1875 Return the symbol for the function corresponding to this frame
1876 as a @code{<gdb:symbol>} object, or @code{#f} if there isn't one.
1877 @xref{Symbols In Guile}.
1880 @deffn {Scheme Procedure} frame-older frame
1881 Return the frame that called @var{frame}.
1884 @deffn {Scheme Procedure} frame-newer frame
1885 Return the frame called by @var{frame}.
1888 @deffn {Scheme Procedure} frame-sal frame
1889 Return the frame's @code{<gdb:sal>} (symtab and line) object.
1890 @xref{Symbol Tables In Guile}.
1893 @deffn {Scheme Procedure} frame-read-var frame variable @r{[}#:block block@r{]}
1894 Return the value of @var{variable} in @var{frame}. If the optional
1895 argument @var{block} is provided, search for the variable from that
1896 block; otherwise start at the frame's current block (which is
1897 determined by the frame's current program counter). @var{variable}
1898 must be a string or a @code{<gdb:symbol>} object. @var{block} must be a
1899 @code{<gdb:block>} object.
1902 @deffn {Scheme Procedure} frame-select frame
1903 Set @var{frame} to be the selected frame. @xref{Stack, ,Examining the
1907 @deffn {Scheme Procedure} selected-frame
1908 Return the selected frame object. @xref{Selection,,Selecting a Frame}.
1911 @deffn {Scheme Procedure} newest-frame
1912 Return the newest frame object for the selected thread.
1915 @deffn {Scheme Procedure} unwind-stop-reason-string reason
1916 Return a string explaining the reason why @value{GDBN} stopped unwinding
1917 frames, as expressed by the given @var{reason} code (an integer, see the
1918 @code{frame-unwind-stop-reason} procedure above in this section).
1921 @node Blocks In Guile
1922 @subsubsection Accessing blocks from Guile.
1924 @cindex blocks in guile
1927 In @value{GDBN}, symbols are stored in blocks. A block corresponds
1928 roughly to a scope in the source code. Blocks are organized
1929 hierarchically, and are represented individually in Guile as an object
1930 of type @code{<gdb:block>}. Blocks rely on debugging information being
1933 A frame has a block. Please see @ref{Frames In Guile}, for a more
1934 in-depth discussion of frames.
1936 The outermost block is known as the @dfn{global block}. The global
1937 block typically holds public global variables and functions.
1939 The block nested just inside the global block is the @dfn{static
1940 block}. The static block typically holds file-scoped variables and
1943 @value{GDBN} provides a method to get a block's superblock, but there
1944 is currently no way to examine the sub-blocks of a block, or to
1945 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
1948 Here is a short example that should help explain blocks:
1951 /* This is in the global block. */
1954 /* This is in the static block. */
1955 static int file_scope;
1957 /* 'function' is in the global block, and 'argument' is
1958 in a block nested inside of 'function'. */
1959 int function (int argument)
1961 /* 'local' is in a block inside 'function'. It may or may
1962 not be in the same block as 'argument'. */
1966 /* 'inner' is in a block whose superblock is the one holding
1970 /* If this call is expanded by the compiler, you may see
1971 a nested block here whose function is 'inline_function'
1972 and whose superblock is the one holding 'inner'. */
1978 The following block-related procedures are provided by the
1979 @code{(gdb)} module:
1981 @deffn {Scheme Procedure} block? object
1982 Return @code{#t} if @var{object} is a @code{<gdb:block>} object.
1983 Otherwise return @code{#f}.
1986 @deffn {Scheme Procedure} block-valid? block
1987 Returns @code{#t} if @code{<gdb:block>} @var{block} is valid,
1988 @code{#f} if not. A block object can become invalid if the block it
1989 refers to doesn't exist anymore in the inferior. All other
1990 @code{<gdb:block>} methods will throw an exception if it is invalid at
1991 the time the procedure is called. The block's validity is also checked
1992 during iteration over symbols of the block.
1995 @deffn {Scheme Procedure} block-start block
1996 Return the start address of @code{<gdb:block>} @var{block}.
1999 @deffn {Scheme Procedure} block-end block
2000 Return the end address of @code{<gdb:block>} @var{block}.
2003 @deffn {Scheme Procedure} block-function block
2004 Return the name of @code{<gdb:block>} @var{block} represented as a
2005 @code{<gdb:symbol>} object.
2006 If the block is not named, then @code{#f} is returned.
2008 For ordinary function blocks, the superblock is the static block.
2009 However, you should note that it is possible for a function block to
2010 have a superblock that is not the static block -- for instance this
2011 happens for an inlined function.
2014 @deffn {Scheme Procedure} block-superblock block
2015 Return the block containing @code{<gdb:block>} @var{block}.
2016 If the parent block does not exist, then @code{#f} is returned.
2019 @deffn {Scheme Procedure} block-global-block block
2020 Return the global block associated with @code{<gdb:block>} @var{block}.
2023 @deffn {Scheme Procedure} block-static-block block
2024 Return the static block associated with @code{<gdb:block>} @var{block}.
2027 @deffn {Scheme Procedure} block-global? block
2028 Return @code{#t} if @code{<gdb:block>} @var{block} is a global block.
2029 Otherwise return @code{#f}.
2032 @deffn {Scheme Procedure} block-static? block
2033 Return @code{#t} if @code{<gdb:block>} @var{block} is a static block.
2034 Otherwise return @code{#f}.
2037 @deffn {Scheme Procedure} block-symbols
2038 Return a list of all symbols (as <gdb:symbol> objects) in
2039 @code{<gdb:block>} @var{block}.
2042 @deffn {Scheme Procedure} make-block-symbols-iterator block
2043 Return an object of type @code{<gdb:iterator>} that will iterate
2044 over all symbols of the block.
2045 Guile programs should not assume that a specific block object will
2046 always contain a given symbol, since changes in @value{GDBN} features and
2047 infrastructure may cause symbols move across blocks in a symbol table.
2048 @xref{Iterators In Guile}.
2051 @deffn {Scheme Procedure} block-symbols-progress?
2052 Return #t if the object is a <gdb:block-symbols-progress> object.
2053 This object would be obtained from the @code{progress} element of the
2054 @code{<gdb:iterator>} object returned by @code{make-block-symbols-iterator}.
2057 @deffn {Scheme Procedure} lookup-block pc
2058 Return the innermost @code{<gdb:block>} containing the given @var{pc}
2059 value. If the block cannot be found for the @var{pc} value specified,
2060 the function will return @code{#f}.
2063 @node Symbols In Guile
2064 @subsubsection Guile representation of Symbols.
2066 @cindex symbols in guile
2067 @tindex <gdb:symbol>
2069 @value{GDBN} represents every variable, function and type as an
2070 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
2071 Guile represents these symbols in @value{GDBN} with the
2072 @code{<gdb:symbol>} object.
2074 The following symbol-related procedures are provided by the
2075 @code{(gdb)} module:
2077 @deffn {Scheme Procedure} symbol? object
2078 Return @code{#t} if @var{object} is an object of type @code{<gdb:symbol>}.
2079 Otherwise return @code{#f}.
2082 @deffn {Scheme Procedure} symbol-valid? symbol
2083 Return @code{#t} if the @code{<gdb:symbol>} object is valid,
2084 @code{#f} if not. A @code{<gdb:symbol>} object can become invalid if
2085 the symbol it refers to does not exist in @value{GDBN} any longer.
2086 All other @code{<gdb:symbol>} procedures will throw an exception if it is
2087 invalid at the time the procedure is called.
2090 @deffn {Scheme Procedure} symbol-type symbol
2091 Return the type of @var{symbol} or @code{#f} if no type is recorded.
2092 The result is an object of type @code{<gdb:type>}.
2093 @xref{Types In Guile}.
2096 @deffn {Scheme Procedure} symbol-symtab symbol
2097 Return the symbol table in which @var{symbol} appears.
2098 The result is an object of type @code{<gdb:symtab>}.
2099 @xref{Symbol Tables In Guile}.
2102 @deffn {Scheme Procedure} symbol-line symbol
2103 Return the line number in the source code at which @var{symbol} was defined.
2107 @deffn {Scheme Procedure} symbol-name symbol
2108 Return the name of @var{symbol} as a string.
2111 @deffn {Scheme Procedure} symbol-linkage-name symbol
2112 Return the name of @var{symbol}, as used by the linker (i.e., may be mangled).
2115 @deffn {Scheme Procedure} symbol-print-name symbol
2116 Return the name of @var{symbol} in a form suitable for output. This is either
2117 @code{name} or @code{linkage_name}, depending on whether the user
2118 asked @value{GDBN} to display demangled or mangled names.
2121 @deffn {Scheme Procedure} symbol-addr-class symbol
2122 Return the address class of the symbol. This classifies how to find the value
2123 of a symbol. Each address class is a constant defined in the
2124 @code{(gdb)} module and described later in this chapter.
2127 @deffn {Scheme Procedure} symbol-needs-frame? symbol
2128 Return @code{#t} if evaluating @var{symbol}'s value requires a frame
2129 (@pxref{Frames In Guile}) and @code{#f} otherwise. Typically,
2130 local variables will require a frame, but other symbols will not.
2133 @deffn {Scheme Procedure} symbol-argument? symbol
2134 Return @code{#t} if @var{symbol} is an argument of a function.
2135 Otherwise return @code{#f}.
2138 @deffn {Scheme Procedure} symbol-constant? symbol
2139 Return @code{#t} if @var{symbol} is a constant.
2140 Otherwise return @code{#f}.
2143 @deffn {Scheme Procedure} symbol-function? symbol
2144 Return @code{#t} if @var{symbol} is a function or a method.
2145 Otherwise return @code{#f}.
2148 @deffn {Scheme Procedure} symbol-variable? symbol
2149 Return @code{#t} if @var{symbol} is a variable.
2150 Otherwise return @code{#f}.
2153 @deffn {Scheme Procedure} symbol-value symbol @r{[}#:frame frame@r{]}
2154 Compute the value of @var{symbol}, as a @code{<gdb:value>}. For
2155 functions, this computes the address of the function, cast to the
2156 appropriate type. If the symbol requires a frame in order to compute
2157 its value, then @var{frame} must be given. If @var{frame} is not
2158 given, or if @var{frame} is invalid, then an exception is thrown.
2161 @c TODO: line length
2162 @deffn {Scheme Procedure} lookup-symbol name @r{[}#:block block@r{]} @r{[}#:domain domain@r{]}
2163 This function searches for a symbol by name. The search scope can be
2164 restricted to the parameters defined in the optional domain and block
2167 @var{name} is the name of the symbol. It must be a string. The
2168 optional @var{block} argument restricts the search to symbols visible
2169 in that @var{block}. The @var{block} argument must be a
2170 @code{<gdb:block>} object. If omitted, the block for the current frame
2171 is used. The optional @var{domain} argument restricts
2172 the search to the domain type. The @var{domain} argument must be a
2173 domain constant defined in the @code{(gdb)} module and described later
2176 The result is a list of two elements.
2177 The first element is a @code{<gdb:symbol>} object or @code{#f} if the symbol
2179 If the symbol is found, the second element is @code{#t} if the symbol
2180 is a field of a method's object (e.g., @code{this} in C@t{++}),
2181 otherwise it is @code{#f}.
2182 If the symbol is not found, the second element is @code{#f}.
2185 @deffn {Scheme Procedure} lookup-global-symbol name @r{[}#:domain domain@r{]}
2186 This function searches for a global symbol by name.
2187 The search scope can be restricted by the domain argument.
2189 @var{name} is the name of the symbol. It must be a string.
2190 The optional @var{domain} argument restricts the search to the domain type.
2191 The @var{domain} argument must be a domain constant defined in the @code{(gdb)}
2192 module and described later in this chapter.
2194 The result is a @code{<gdb:symbol>} object or @code{#f} if the symbol
2198 The available domain categories in @code{<gdb:symbol>} are represented
2199 as constants in the @code{(gdb)} module:
2202 @item SYMBOL_UNDEF_DOMAIN
2203 This is used when a domain has not been discovered or none of the
2204 following domains apply. This usually indicates an error either
2205 in the symbol information or in @value{GDBN}'s handling of symbols.
2207 @item SYMBOL_VAR_DOMAIN
2208 This domain contains variables, function names, typedef names and enum
2211 @item SYMBOL_STRUCT_DOMAIN
2212 This domain holds struct, union and enum type names.
2214 @item SYMBOL_LABEL_DOMAIN
2215 This domain contains names of labels (for gotos).
2217 @item SYMBOL_VARIABLES_DOMAIN
2218 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
2219 contains everything minus functions and types.
2221 @item SYMBOL_FUNCTION_DOMAIN
2222 This domain contains all functions.
2224 @item SYMBOL_TYPES_DOMAIN
2225 This domain contains all types.
2228 The available address class categories in @code{<gdb:symbol>} are represented
2229 as constants in the @code{gdb} module:
2232 @item SYMBOL_LOC_UNDEF
2233 If this is returned by address class, it indicates an error either in
2234 the symbol information or in @value{GDBN}'s handling of symbols.
2236 @item SYMBOL_LOC_CONST
2237 Value is constant int.
2239 @item SYMBOL_LOC_STATIC
2240 Value is at a fixed address.
2242 @item SYMBOL_LOC_REGISTER
2243 Value is in a register.
2245 @item SYMBOL_LOC_ARG
2246 Value is an argument. This value is at the offset stored within the
2247 symbol inside the frame's argument list.
2249 @item SYMBOL_LOC_REF_ARG
2250 Value address is stored in the frame's argument list. Just like
2251 @code{LOC_ARG} except that the value's address is stored at the
2252 offset, not the value itself.
2254 @item SYMBOL_LOC_REGPARM_ADDR
2255 Value is a specified register. Just like @code{LOC_REGISTER} except
2256 the register holds the address of the argument instead of the argument
2259 @item SYMBOL_LOC_LOCAL
2260 Value is a local variable.
2262 @item SYMBOL_LOC_TYPEDEF
2263 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
2266 @item SYMBOL_LOC_BLOCK
2269 @item SYMBOL_LOC_CONST_BYTES
2270 Value is a byte-sequence.
2272 @item SYMBOL_LOC_UNRESOLVED
2273 Value is at a fixed address, but the address of the variable has to be
2274 determined from the minimal symbol table whenever the variable is
2277 @item SYMBOL_LOC_OPTIMIZED_OUT
2278 The value does not actually exist in the program.
2280 @item SYMBOL_LOC_COMPUTED
2281 The value's address is a computed location.
2284 @node Symbol Tables In Guile
2285 @subsubsection Symbol table representation in Guile.
2287 @cindex symbol tables in guile
2288 @tindex <gdb:symtab>
2291 Access to symbol table data maintained by @value{GDBN} on the inferior
2292 is exposed to Guile via two objects: @code{<gdb:sal>} (symtab-and-line) and
2293 @code{<gdb:symtab>}. Symbol table and line data for a frame is returned
2294 from the @code{frame-find-sal} @code{<gdb:frame>} procedure.
2295 @xref{Frames In Guile}.
2297 For more information on @value{GDBN}'s symbol table management, see
2298 @ref{Symbols, ,Examining the Symbol Table}.
2300 The following symtab-related procedures are provided by the
2301 @code{(gdb)} module:
2303 @deffn {Scheme Procedure} symtab? object
2304 Return @code{#t} if @var{object} is an object of type @code{<gdb:symtab>}.
2305 Otherwise return @code{#f}.
2308 @deffn {Scheme Procedure} symtab-valid? symtab
2309 Return @code{#t} if the @code{<gdb:symtab>} object is valid,
2310 @code{#f} if not. A @code{<gdb:symtab>} object becomes invalid when
2311 the symbol table it refers to no longer exists in @value{GDBN}.
2312 All other @code{<gdb:symtab>} procedures will throw an exception
2313 if it is invalid at the time the procedure is called.
2316 @deffn {Scheme Procedure} symtab-filename symtab
2317 Return the symbol table's source filename.
2320 @deffn {Scheme Procedure} symtab-fullname symtab
2321 Return the symbol table's source absolute file name.
2324 @deffn {Scheme Procedure} symtab-objfile symtab
2325 Return the symbol table's backing object file. @xref{Objfiles In Guile}.
2328 @deffn {Scheme Procedure} symtab-global-block symtab
2329 Return the global block of the underlying symbol table.
2330 @xref{Blocks In Guile}.
2333 @deffn {Scheme Procedure} symtab-static-block symtab
2334 Return the static block of the underlying symbol table.
2335 @xref{Blocks In Guile}.
2338 The following symtab-and-line-related procedures are provided by the
2339 @code{(gdb)} module:
2341 @deffn {Scheme Procedure} sal? object
2342 Return @code{#t} if @var{object} is an object of type @code{<gdb:sal>}.
2343 Otherwise return @code{#f}.
2346 @deffn {Scheme Procedure} sal-valid? sal
2347 Return @code{#t} if @var{sal} is valid, @code{#f} if not.
2348 A @code{<gdb:sal>} object becomes invalid when the Symbol table object
2349 it refers to no longer exists in @value{GDBN}. All other
2350 @code{<gdb:sal>} procedures will throw an exception if it is
2351 invalid at the time the procedure is called.
2354 @deffn {Scheme Procedure} sal-symtab sal
2355 Return the symbol table object (@code{<gdb:symtab>}) for @var{sal}.
2358 @deffn {Scheme Procedure} sal-line sal
2359 Return the line number for @var{sal}.
2362 @deffn {Scheme Procedure} sal-pc sal
2363 Return the start of the address range occupied by code for @var{sal}.
2366 @deffn {Scheme Procedure} sal-last sal
2367 Return the end of the address range occupied by code for @var{sal}.
2370 @deffn {Scheme Procedure} find-pc-line pc
2371 Return the @code{<gdb:sal>} object corresponding to the @var{pc} value.
2372 If an invalid value of @var{pc} is passed as an argument, then the
2373 @code{symtab} and @code{line} attributes of the returned @code{<gdb:sal>}
2374 object will be @code{#f} and 0 respectively.
2377 @node Breakpoints In Guile
2378 @subsubsection Manipulating breakpoints using Guile
2380 @cindex breakpoints in guile
2381 @tindex <gdb:breakpoint>
2383 Breakpoints in Guile are represented by objects of type
2384 @code{<gdb:breakpoint>}.
2386 The following breakpoint-related procedures are provided by the
2387 @code{(gdb)} module:
2389 @c TODO: line length
2390 @deffn {Scheme Procedure} create-breakpoint! location @r{[}#:type type@r{]} @r{[}#:wp-class wp-class@r{]} @r{[}#:internal internal@r{]}
2391 Create a new breakpoint. @var{spec} is a string naming the
2392 location of the breakpoint, or an expression that defines a watchpoint.
2393 The contents can be any location recognized by the @code{break} command,
2394 or in the case of a watchpoint, by the @code{watch} command.
2396 The optional @var{type} denotes the breakpoint to create.
2397 This argument can be either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}.
2398 @var{type} defaults to @code{BP_BREAKPOINT}.
2400 The optional @var{wp-class} argument defines the class of watchpoint to
2401 create, if @var{type} is @code{BP_WATCHPOINT}. If a watchpoint class is
2402 not provided, it is assumed to be a @code{WP_WRITE} class.
2404 The optional @var{internal} argument allows the breakpoint to become
2405 invisible to the user. The breakpoint will neither be reported when
2406 created, nor will it be listed in the output from @code{info breakpoints}
2407 (but will be listed with the @code{maint info breakpoints} command).
2408 If an internal flag is not provided, the breakpoint is visible
2411 When a watchpoint is created, @value{GDBN} will try to create a
2412 hardware assisted watchpoint. If successful, the type of the watchpoint
2413 is changed from @code{BP_WATCHPOINT} to @code{BP_HARDWARE_WATCHPOINT}
2414 for @code{WP_WRITE}, @code{BP_READ_WATCHPOINT} for @code{WP_READ},
2415 and @code{BP_ACCESS_WATCHPOINT} for @code{WP_ACCESS}.
2416 If not successful, the type of the watchpoint is left as @code{WP_WATCHPOINT}.
2418 The available types are represented by constants defined in the @code{gdb}
2423 Normal code breakpoint.
2426 Watchpoint breakpoint.
2428 @item BP_HARDWARE_WATCHPOINT
2429 Hardware assisted watchpoint.
2430 This value cannot be specified when creating the breakpoint.
2432 @item BP_READ_WATCHPOINT
2433 Hardware assisted read watchpoint.
2434 This value cannot be specified when creating the breakpoint.
2436 @item BP_ACCESS_WATCHPOINT
2437 Hardware assisted access watchpoint.
2438 This value cannot be specified when creating the breakpoint.
2441 The available watchpoint types represented by constants are defined in the
2442 @code{(gdb)} module:
2446 Read only watchpoint.
2449 Write only watchpoint.
2452 Read/Write watchpoint.
2457 @deffn {Scheme Procedure} breakpoint-delete! breakpoint
2458 Permanently delete @var{breakpoint}. This also invalidates the
2459 Guile @var{breakpoint} object. Any further attempt to access the
2460 object will throw an exception.
2463 @deffn {Scheme Procedure} breakpoints
2464 Return a list of all breakpoints.
2465 Each element of the list is a @code{<gdb:breakpoint>} object.
2468 @deffn {Scheme Procedure} breakpoint? object
2469 Return @code{#t} if @var{object} is a @code{<gdb:breakpoint>} object,
2470 and @code{#f} otherwise.
2473 @deffn {Scheme Procedure} breakpoint-valid? breakpoint
2474 Return @code{#t} if @var{breakpoint} is valid, @code{#f} otherwise.
2475 A @code{<gdb:breakpoint>} object can become invalid
2476 if the user deletes the breakpoint. In this case, the object still
2477 exists, but the underlying breakpoint does not. In the cases of
2478 watchpoint scope, the watchpoint remains valid even if execution of the
2479 inferior leaves the scope of that watchpoint.
2482 @deffn {Scheme Procedure} breakpoint-number breakpoint
2483 Return the breakpoint's number --- the identifier used by
2484 the user to manipulate the breakpoint.
2487 @deffn {Scheme Procedure} breakpoint-type breakpoint
2488 Return the breakpoint's type --- the identifier used to
2489 determine the actual breakpoint type or use-case.
2492 @deffn {Scheme Procedure} breakpoint-visible? breakpoint
2493 Return @code{#t} if the breakpoint is visible to the user
2494 when hit, or when the @samp{info breakpoints} command is run.
2495 Otherwise return @code{#f}.
2498 @deffn {Scheme Procedure} breakpoint-location breakpoint
2499 Return the location of the breakpoint, as specified by
2500 the user. It is a string. If the breakpoint does not have a location
2501 (that is, it is a watchpoint) return @code{#f}.
2504 @deffn {Scheme Procedure} breakpoint-expression breakpoint
2505 Return the breakpoint expression, as specified by the user. It is a string.
2506 If the breakpoint does not have an expression (the breakpoint is not a
2507 watchpoint) return @code{#f}.
2510 @deffn {Scheme Procedure} breakpoint-enabled? breakpoint
2511 Return @code{#t} if the breakpoint is enabled, and @code{#f} otherwise.
2514 @deffn {Scheme Procedure} set-breakpoint-enabled! breakpoint flag
2515 Set the enabled state of @var{breakpoint} to @var{flag}.
2516 If flag is @code{#f} it is disabled, otherwise it is enabled.
2519 @deffn {Scheme Procedure} breakpoint-silent? breakpoint
2520 Return @code{#t} if the breakpoint is silent, and @code{#f} otherwise.
2522 Note that a breakpoint can also be silent if it has commands and the
2523 first command is @code{silent}. This is not reported by the
2524 @code{silent} attribute.
2527 @deffn {Scheme Procedure} set-breakpoint-silent! breakpoint flag
2528 Set the silent state of @var{breakpoint} to @var{flag}.
2529 If flag is @code{#f} the breakpoint is made silent,
2530 otherwise it is made non-silent (or noisy).
2533 @deffn {Scheme Procedure} breakpoint-ignore-count breakpoint
2534 Return the ignore count for @var{breakpoint}.
2537 @deffn {Scheme Procedure} set-breakpoint-ignore-count! breakpoint count
2538 Set the ignore count for @var{breakpoint} to @var{count}.
2541 @deffn {Scheme Procedure} breakpoint-hit-count breakpoint
2542 Return hit count of @var{breakpoint}.
2545 @deffn {Scheme Procedure} set-breakpoint-hit-count! breakpoint count
2546 Set the hit count of @var{breakpoint} to @var{count}.
2547 At present, @var{count} must be zero.
2550 @deffn {Scheme Procedure} breakpoint-thread breakpoint
2551 Return the thread-id for thread-specific breakpoint @var{breakpoint}.
2552 Return #f if @var{breakpoint} is not thread-specific.
2555 @deffn {Scheme Procedure} set-breakpoint-thread! breakpoint thread-id|#f
2556 Set the thread-id for @var{breakpoint} to @var{thread-id}.
2557 If set to @code{#f}, the breakpoint is no longer thread-specific.
2560 @deffn {Scheme Procedure} breakpoint-task breakpoint
2561 If the breakpoint is Ada task-specific, return the Ada task id.
2562 If the breakpoint is not task-specific (or the underlying
2563 language is not Ada), return @code{#f}.
2566 @deffn {Scheme Procedure} set-breakpoint-task! breakpoint task
2567 Set the Ada task of @var{breakpoint} to @var{task}.
2568 If set to @code{#f}, the breakpoint is no longer task-specific.
2571 @deffn {Scheme Procedure} breakpoint-condition breakpoint
2572 Return the condition of @var{breakpoint}, as specified by the user.
2573 It is a string. If there is no condition, return @code{#f}.
2576 @deffn {Scheme Procedure} set-breakpoint-condition! breakpoint condition
2577 Set the condition of @var{breakpoint} to @var{condition},
2578 which must be a string. If set to @code{#f} then the breakpoint
2579 becomes unconditional.
2582 @deffn {Scheme Procedure} breakpoint-stop breakpoint
2583 Return the stop predicate of @var{breakpoint}.
2584 See @code{set-breakpoint-stop!} below in this section.
2587 @deffn {Scheme Procedure} set-breakpoint-stop! breakpoint procedure|#f
2588 Set the stop predicate of @var{breakpoint}.
2589 @var{procedure} takes one argument: the <gdb:breakpoint> object.
2590 If this predicate is set to a procedure then it is invoked whenever
2591 the inferior reaches this breakpoint. If it returns @code{#t},
2592 or any non-@code{#f} value, then the inferior is stopped,
2593 otherwise the inferior will continue.
2595 If there are multiple breakpoints at the same location with a
2596 @code{stop} predicate, each one will be called regardless of the
2597 return status of the previous. This ensures that all @code{stop}
2598 predicates have a chance to execute at that location. In this scenario
2599 if one of the methods returns @code{#t} but the others return
2600 @code{#f}, the inferior will still be stopped.
2602 You should not alter the execution state of the inferior (i.e.@:, step,
2603 next, etc.), alter the current frame context (i.e.@:, change the current
2604 active frame), or alter, add or delete any breakpoint. As a general
2605 rule, you should not alter any data within @value{GDBN} or the inferior
2608 Example @code{stop} implementation:
2611 (define (my-stop? bkpt)
2612 (let ((int-val (parse-and-eval "foo")))
2613 (value=? int-val 3)))
2614 (define bkpt (create-breakpoint! "main.c:42"))
2615 (set-breakpoint-stop! bkpt my-stop?)
2619 @deffn {Scheme Procedure} breakpoint-commands breakpoint
2620 Return the commands attached to @var{breakpoint} as a string,
2621 or @code{#f} if there are none.
2624 @node Lazy Strings In Guile
2625 @subsubsection Guile representation of lazy strings.
2627 @cindex lazy strings in guile
2628 @tindex <gdb:lazy-string>
2630 A @dfn{lazy string} is a string whose contents is not retrieved or
2631 encoded until it is needed.
2633 A @code{<gdb:lazy-string>} is represented in @value{GDBN} as an
2634 @code{address} that points to a region of memory, an @code{encoding}
2635 that will be used to encode that region of memory, and a @code{length}
2636 to delimit the region of memory that represents the string. The
2637 difference between a @code{<gdb:lazy-string>} and a string wrapped within
2638 a @code{<gdb:value>} is that a @code{<gdb:lazy-string>} will be treated
2639 differently by @value{GDBN} when printing. A @code{<gdb:lazy-string>} is
2640 retrieved and encoded during printing, while a @code{<gdb:value>}
2641 wrapping a string is immediately retrieved and encoded on creation.
2643 The following lazy-string-related procedures are provided by the
2644 @code{(gdb)} module:
2646 @deffn {Scheme Procedure} lazy-string? object
2647 Return @code{#t} if @var{object} is an object of type @code{<gdb:lazy-string>}.
2648 Otherwise return @code{#f}.
2651 @deffn {Scheme Procedure} lazy-string-address lazy-sring
2652 Return the address of @var{lazy-string}.
2655 @deffn {Scheme Procedure} lazy-string-length lazy-string
2656 Return the length of @var{lazy-string} in characters. If the
2657 length is -1, then the string will be fetched and encoded up to the
2658 first null of appropriate width.
2661 @deffn {Scheme Procedure} lazy-string-encoding lazy-string
2662 Return the encoding that will be applied to @var{lazy-string}
2663 when the string is printed by @value{GDBN}. If the encoding is not
2664 set, or contains an empty string, then @value{GDBN} will select the
2665 most appropriate encoding when the string is printed.
2668 @deffn {Scheme Procedure} lazy-string-type lazy-string
2669 Return the type that is represented by @var{lazy-string}'s type.
2670 For a lazy string this will always be a pointer type. To
2671 resolve this to the lazy string's character type, use @code{type-target-type}.
2672 @xref{Types In Guile}.
2675 @deffn {Scheme Procedure} lazy-string->value lazy-string
2676 Convert the @code{<gdb:lazy-string>} to a @code{<gdb:value>}. This value
2677 will point to the string in memory, but will lose all the delayed
2678 retrieval, encoding and handling that @value{GDBN} applies to a
2679 @code{<gdb:lazy-string>}.
2682 @node Architectures In Guile
2683 @subsubsection Guile representation of architectures
2685 @cindex guile architectures
2688 @value{GDBN} uses architecture specific parameters and artifacts in a
2689 number of its various computations. An architecture is represented
2690 by an instance of the @code{<gdb:arch>} class.
2692 The following architecture-related procedures are provided by the
2693 @code{(gdb)} module:
2695 @deffn {Scheme Procedure} arch? object
2696 Return @code{#t} if @var{object} is an object of type @code{<gdb:arch>}.
2697 Otherwise return @code{#f}.
2700 @deffn {Scheme Procedure} current-arch
2701 Return the current architecture as a @code{<gdb:arch>} object.
2704 @deffn {Scheme Procedure} arch-name arch
2705 Return the name (string value) of @code{<gdb:arch>} @var{arch}.
2708 @deffn {Scheme Procedure} arch-charset arch
2709 Return name of target character set of @code{<gdb:arch>} @var{arch}.
2712 @deffn {Scheme Procedure} arch-wide-charset
2713 Return name of target wide character set of @code{<gdb:arch>} @var{arch}.
2716 Each architecture provides a set of predefined types, obtained by
2717 the following functions.
2719 @deffn {Scheme Procedure} arch-void-type arch
2720 Return the @code{<gdb:type>} object for a @code{void} type
2721 of architecture @var{arch}.
2724 @deffn {Scheme Procedure} arch-char-type arch
2725 Return the @code{<gdb:type>} object for a @code{char} type
2726 of architecture @var{arch}.
2729 @deffn {Scheme Procedure} arch-short-type arch
2730 Return the @code{<gdb:type>} object for a @code{short} type
2731 of architecture @var{arch}.
2734 @deffn {Scheme Procedure} arch-int-type arch
2735 Return the @code{<gdb:type>} object for an @code{int} type
2736 of architecture @var{arch}.
2739 @deffn {Scheme Procedure} arch-long-type arch
2740 Return the @code{<gdb:type>} object for a @code{long} type
2741 of architecture @var{arch}.
2744 @deffn {Scheme Procedure} arch-schar-type arch
2745 Return the @code{<gdb:type>} object for a @code{signed char} type
2746 of architecture @var{arch}.
2749 @deffn {Scheme Procedure} arch-uchar-type arch
2750 Return the @code{<gdb:type>} object for an @code{unsigned char} type
2751 of architecture @var{arch}.
2754 @deffn {Scheme Procedure} arch-ushort-type arch
2755 Return the @code{<gdb:type>} object for an @code{unsigned short} type
2756 of architecture @var{arch}.
2759 @deffn {Scheme Procedure} arch-uint-type arch
2760 Return the @code{<gdb:type>} object for an @code{unsigned int} type
2761 of architecture @var{arch}.
2764 @deffn {Scheme Procedure} arch-ulong-type arch
2765 Return the @code{<gdb:type>} object for an @code{unsigned long} type
2766 of architecture @var{arch}.
2769 @deffn {Scheme Procedure} arch-float-type arch
2770 Return the @code{<gdb:type>} object for a @code{float} type
2771 of architecture @var{arch}.
2774 @deffn {Scheme Procedure} arch-double-type arch
2775 Return the @code{<gdb:type>} object for a @code{double} type
2776 of architecture @var{arch}.
2779 @deffn {Scheme Procedure} arch-longdouble-type arch
2780 Return the @code{<gdb:type>} object for a @code{long double} type
2781 of architecture @var{arch}.
2784 @deffn {Scheme Procedure} arch-bool-type arch
2785 Return the @code{<gdb:type>} object for a @code{bool} type
2786 of architecture @var{arch}.
2789 @deffn {Scheme Procedure} arch-longlong-type arch
2790 Return the @code{<gdb:type>} object for a @code{long long} type
2791 of architecture @var{arch}.
2794 @deffn {Scheme Procedure} arch-ulonglong-type arch
2795 Return the @code{<gdb:type>} object for an @code{unsigned long long} type
2796 of architecture @var{arch}.
2799 @deffn {Scheme Procedure} arch-int8-type arch
2800 Return the @code{<gdb:type>} object for an @code{int8} type
2801 of architecture @var{arch}.
2804 @deffn {Scheme Procedure} arch-uint8-type arch
2805 Return the @code{<gdb:type>} object for a @code{uint8} type
2806 of architecture @var{arch}.
2809 @deffn {Scheme Procedure} arch-int16-type arch
2810 Return the @code{<gdb:type>} object for an @code{int16} type
2811 of architecture @var{arch}.
2814 @deffn {Scheme Procedure} arch-uint16-type arch
2815 Return the @code{<gdb:type>} object for a @code{uint16} type
2816 of architecture @var{arch}.
2819 @deffn {Scheme Procedure} arch-int32-type arch
2820 Return the @code{<gdb:type>} object for an @code{int32} type
2821 of architecture @var{arch}.
2824 @deffn {Scheme Procedure} arch-uint32-type arch
2825 Return the @code{<gdb:type>} object for a @code{uint32} type
2826 of architecture @var{arch}.
2829 @deffn {Scheme Procedure} arch-int64-type arch
2830 Return the @code{<gdb:type>} object for an @code{int64} type
2831 of architecture @var{arch}.
2834 @deffn {Scheme Procedure} arch-uint64-type arch
2835 Return the @code{<gdb:type>} object for a @code{uint64} type
2836 of architecture @var{arch}.
2842 (gdb) guile (type-name (arch-uchar-type (current-arch)))
2846 @node Disassembly In Guile
2847 @subsubsection Disassembly In Guile
2849 The disassembler can be invoked from Scheme code.
2850 Furthermore, the disassembler can take a Guile port as input,
2851 allowing one to disassemble from any source, and not just target memory.
2853 @c TODO: line length
2854 @deffn {Scheme Procedure} arch-disassemble arch start-pc @r{[}#:port port@r{]} @r{[}#:offset offset@r{]} @r{[}#:size size@r{]} @r{[}#:count count@r{]}
2855 Return a list of disassembled instructions starting from the memory
2856 address @var{start-pc}.
2858 The optional argument @var{port} specifies the input port to read bytes from.
2859 If @var{port} is @code{#f} then bytes are read from target memory.
2861 The optional argument @var{offset} specifies the address offset of the
2862 first byte in @var{port}. This is useful, for example, when @var{port}
2863 specifies a @samp{bytevector} and you want the bytevector to be disassembled
2864 as if it came from that address. The @var{start-pc} passed to the reader
2865 for @var{port} is offset by the same amount.
2869 (gdb) guile (use-modules (rnrs io ports))
2870 (gdb) guile (define pc (value->integer (parse-and-eval "$pc")))
2871 (gdb) guile (define mem (open-memory #:start pc))
2872 (gdb) guile (define bv (get-bytevector-n mem 10))
2873 (gdb) guile (define bv-port (open-bytevector-input-port bv))
2874 (gdb) guile (define arch (current-arch))
2875 (gdb) guile (arch-disassemble arch pc #:port bv-port #:offset pc)
2876 (((address . 4195516) (asm . "mov $0x4005c8,%edi") (length . 5)))
2879 The optional arguments @var{size} and
2880 @var{count} determine the number of instructions in the returned list.
2881 If either @var{size} or @var{count} is specified as zero, then
2882 no instructions are disassembled and an empty list is returned.
2883 If both the optional arguments @var{size} and @var{count} are
2884 specified, then a list of at most @var{count} disassembled instructions
2885 whose start address falls in the closed memory address interval from
2886 @var{start-pc} to (@var{start-pc} + @var{size} - 1) are returned.
2887 If @var{size} is not specified, but @var{count} is specified,
2888 then @var{count} number of instructions starting from the address
2889 @var{start-pc} are returned. If @var{count} is not specified but
2890 @var{size} is specified, then all instructions whose start address
2891 falls in the closed memory address interval from @var{start-pc} to
2892 (@var{start-pc} + @var{size} - 1) are returned.
2893 If neither @var{size} nor @var{count} are specified, then a single
2894 instruction at @var{start-pc} is returned.
2896 Each element of the returned list is an alist (associative list)
2897 with the following keys:
2902 The value corresponding to this key is a Guile integer of
2903 the memory address of the instruction.
2906 The value corresponding to this key is a string value which represents
2907 the instruction with assembly language mnemonics. The assembly
2908 language flavor used is the same as that specified by the current CLI
2909 variable @code{disassembly-flavor}. @xref{Machine Code}.
2912 The value corresponding to this key is the length of the instruction in bytes.
2917 @node I/O Ports in Guile
2918 @subsubsection I/O Ports in Guile
2920 @deffn {Scheme Procedure} input-port
2921 Return @value{GDBN}'s input port as a Guile port object.
2924 @deffn {Scheme Procedure} output-port
2925 Return @value{GDBN}'s output port as a Guile port object.
2928 @deffn {Scheme Procedure} error-port
2929 Return @value{GDBN}'s error port as a Guile port object.
2932 @deffn {Scheme Procedure} stdio-port? object
2933 Return @code{#t} if @var{object} is a @value{GDBN} stdio port.
2934 Otherwise return @code{#f}.
2937 @node Memory Ports in Guile
2938 @subsubsection Memory Ports in Guile
2940 @value{GDBN} provides a @code{port} interface to target memory.
2941 This allows Guile code to read/write target memory using Guile's port and
2942 bytevector functionality. The main routine is @code{open-memory} which
2943 returns a port object. One can then read/write memory using that object.
2945 @deffn {Scheme Procedure} open-memory @r{[}#:mode mode{]} @r{[}#:start address{]} @r{[}#:size size{]}
2946 Return a port object that can be used for reading and writing memory.
2947 @var{mode} is the standard mode argument to Guile port open routines,
2948 except that it is restricted to one of @samp{"r"}, @samp{"w"}, or @samp{"r+"}.
2949 For compatibility @samp{"b"} (binary) may also be present,
2950 but we ignore it: memory ports are binary only.
2951 The default is @samp{"r"}, read-only.
2953 The chunk of memory that can be accessed can be bounded.
2954 If both @var{start} and @var{size} are unspecified, all of memory can be
2955 accessed. If only @var{start} is specified, all of memory from that point
2956 on can be accessed. If only @var{size} if specified, all memory in the
2957 range [0,@var{size}) can be accessed. If both are specified, all memory
2958 in the rane [@var{start},@var{start}+@var{size}) can be accessed.
2961 @deffn {Scheme Procedure} memory-port?
2962 Return @code{#t} if @var{object} is an object of type @code{<gdb:memory-port>}.
2963 Otherwise return @code{#f}.
2966 @deffn {Scheme Procedure} memory-port-range memory-port
2967 Return the range of @code{<gdb:memory-port>} @var{memory-port} as a list
2968 of two elements: @code{(start end)}. The range is @var{start} to @var{end}
2972 @deffn {Scheme Procedure} memory-port-read-buffer-size memory-port
2973 Return the size of the read buffer of @code{<gdb:memory-port>}
2977 @deffn {Scheme Procedure} set-memory-port-read-buffer-size! memory-port size
2978 Set the size of the read buffer of @code{<gdb:memory-port>}
2979 @var{memory-port} to @var{size}. The result is unspecified.
2982 @deffn {Scheme Procedure} memory-port-write-buffer-size memory-port
2983 Return the size of the write buffer of @code{<gdb:memory-port>}
2987 @deffn {Scheme Procedure} set-memory-port-write-buffer-size! memory-port size
2988 Set the size of the write buffer of @code{<gdb:memory-port>}
2989 @var{memory-port} to @var{size}. The result is unspecified.
2992 A memory port is closed like any other port, with @code{close-port}.
2994 Combined with Guile's @code{bytevectors}, memory ports provide a lot
2995 of utility. For example, to fill a buffer of 10 integers in memory,
2996 one can do something like the following.
2999 ;; In the program: int buffer[10];
3000 (use-modules (rnrs bytevectors))
3001 (use-modules (rnrs io ports))
3002 (define addr (parse-and-eval "buffer"))
3004 (define byte-size (* n 4))
3005 (define mem-port (open-memory #:mode "r+" #:start
3006 (value->integer addr) #:size byte-size))
3007 (define byte-vec (make-bytevector byte-size))
3010 (bytevector-s32-native-set! byte-vec (* i 4) (* i 42)))
3011 (put-bytevector mem-port byte-vec)
3012 (close-port mem-port)
3015 @node Iterators In Guile
3016 @subsubsection Iterators In Guile
3018 @cindex guile iterators
3019 @tindex <gdb:iterator>
3021 A simple iterator facility is provided to allow, for example,
3022 iterating over the set of program symbols without having to first
3023 construct a list of all of them. A useful contribution would be
3024 to add support for SRFI 41 and SRFI 45.
3026 @deffn {Scheme Procedure} make-iterator object progress next!
3027 A @code{<gdb:iterator>} object is constructed with the @code{make-iterator}
3028 procedure. It takes three arguments: the object to be iterated over,
3029 an object to record the progress of the iteration, and a procedure to
3030 return the next element in the iteration, or an implementation chosen value
3031 to denote the end of iteration.
3033 By convention, end of iteration is marked with @code{(end-of-iteration)},
3034 and may be tested with the @code{end-of-iteration?} predicate.
3035 The result of @code{(end-of-iteration)} is chosen so that it is not
3036 otherwise used by the @code{(gdb)} module. If you are using
3037 @code{<gdb:iterator>} in your own code it is your responsibility to
3038 maintain this invariant.
3040 A trivial example for illustration's sake:
3043 (use-modules (gdb iterator))
3044 (define my-list (list 1 2 3))
3046 (make-iterator my-list my-list
3048 (let ((l (iterator-progress iter)))
3052 (set-iterator-progress! iter (cdr l))
3056 Here is a slightly more realistic example, which computes a list of all the
3057 functions in @code{my-global-block}.
3060 (use-modules (gdb iterator))
3061 (define this-sal (find-pc-line (frame-pc (selected-frame))))
3062 (define this-symtab (sal-symtab this-sal))
3063 (define this-global-block (symtab-global-block this-symtab))
3064 (define syms-iter (make-block-symbols-iterator this-global-block))
3065 (define functions (iterator-filter symbol-function? syms-iter))
3069 @deffn {Scheme Procedure} iterator? object
3070 Return @code{#t} if @var{object} is a @code{<gdb:iterator>} object.
3071 Otherwise return @code{#f}.
3074 @deffn {Scheme Procedure} iterator-object iterator
3075 Return the first argument that was passed to @code{make-iterator}.
3076 This is the object being iterated over.
3079 @deffn {Scheme Procedure} iterator-progress iterator
3080 Return the object tracking iteration progress.
3083 @deffn {Scheme Procedure} set-iterator-progress! iterator new-value
3084 Set the object tracking iteration progress.
3087 @deffn {Scheme Procedure} iterator-next! iterator
3088 Invoke the procedure that was the third argument to @code{make-iterator},
3089 passing it one argument, the @code{<gdb:iterator>} object.
3090 The result is either the next element in the iteration, or an end
3091 marker as implemented by the @code{next!} procedure.
3092 By convention the end marker is the result of @code{(end-of-iteration)}.
3095 @deffn {Scheme Procedure} end-of-iteration
3096 Return the Scheme object that denotes end of iteration.
3099 @deffn {Scheme Procedure} end-of-iteration? object
3100 Return @code{#t} if @var{object} is the end of iteration marker.
3101 Otherwise return @code{#f}.
3104 These functions are provided by the @code{(gdb iterator)} module to
3105 assist in using iterators.
3107 @deffn {Scheme Procedure} make-list-iterator list
3108 Return a @code{<gdb:iterator>} object that will iterate over @var{list}.
3111 @deffn {Scheme Procedure} iterator->list iterator
3112 Return the elements pointed to by @var{iterator} as a list.
3115 @deffn {Scheme Procedure} iterator-map proc iterator
3116 Return the list of objects obtained by applying @var{proc} to the object
3117 pointed to by @var{iterator} and to each subsequent object.
3120 @deffn {Scheme Procedure} iterator-for-each proc iterator
3121 Apply @var{proc} to each element pointed to by @var{iterator}.
3122 The result is unspecified.
3125 @deffn {Scheme Procedure} iterator-filter pred iterator
3126 Return the list of elements pointed to by @var{iterator} that satisfy
3130 @deffn {Scheme Procedure} iterator-until pred iterator
3131 Run @var{iterator} until the result of @code{(pred element)} is true
3132 and return that as the result. Otherwise return @code{#f}.
3135 @node Guile Auto-loading
3136 @subsection Guile Auto-loading
3137 @cindex guile auto-loading
3139 When a new object file is read (for example, due to the @code{file}
3140 command, or because the inferior has loaded a shared library),
3141 @value{GDBN} will look for Guile support scripts in two ways:
3142 @file{@var{objfile}-gdb.scm} and the @code{.debug_gdb_scripts} section.
3143 @xref{Auto-loading extensions}.
3145 The auto-loading feature is useful for supplying application-specific
3146 debugging commands and scripts.
3148 Auto-loading can be enabled or disabled,
3149 and the list of auto-loaded scripts can be printed.
3152 @anchor{set auto-load guile-scripts}
3153 @kindex set auto-load guile-scripts
3154 @item set auto-load guile-scripts [on|off]
3155 Enable or disable the auto-loading of Guile scripts.
3157 @anchor{show auto-load guile-scripts}
3158 @kindex show auto-load guile-scripts
3159 @item show auto-load guile-scripts
3160 Show whether auto-loading of Guile scripts is enabled or disabled.
3162 @anchor{info auto-load guile-scripts}
3163 @kindex info auto-load guile-scripts
3164 @cindex print list of auto-loaded Guile scripts
3165 @item info auto-load guile-scripts [@var{regexp}]
3166 Print the list of all Guile scripts that @value{GDBN} auto-loaded.
3168 Also printed is the list of Guile scripts that were mentioned in
3169 the @code{.debug_gdb_scripts} section and were not found.
3170 This is useful because their names are not printed when @value{GDBN}
3171 tries to load them and fails. There may be many of them, and printing
3172 an error message for each one is problematic.
3174 If @var{regexp} is supplied only Guile scripts with matching names are printed.
3179 (gdb) info auto-load guile-scripts
3181 Yes scm-section-script.scm
3182 full name: /tmp/scm-section-script.scm
3183 No my-foo-pretty-printers.scm
3187 When reading an auto-loaded file, @value{GDBN} sets the
3188 @dfn{current objfile}. This is available via the @code{current-objfile}
3189 procedure (@pxref{Objfiles In Guile}). This can be useful for
3190 registering objfile-specific pretty-printers.
3193 @subsection Guile Modules
3194 @cindex guile modules
3196 @value{GDBN} comes with several modules to assist writing Guile code.
3199 * Guile Printing Module:: Building and registering pretty-printers
3200 * Guile Types Module:: Utilities for working with types
3203 @node Guile Printing Module
3204 @subsubsection Guile Printing Module
3206 This module provides a collection of utilities for working with
3212 (use-modules (gdb printing))
3215 @deffn {Scheme Procedure} prepend-pretty-printer! object printer
3216 Add @var{printer} to the front of the list of pretty-printers for
3217 @var{object}. @var{object} must either be a @code{<gdb:objfile>} object
3218 or @code{#f} in which case @var{printer} is added to the global list of
3222 @deffn {Scheme Procecure} append-pretty-printer! object printer
3223 Add @var{printer} to the end of the list of pretty-printers for
3224 @var{object}. @var{object} must either be a @code{<gdb:objfile>} object
3225 or @code{#f} in which case @var{printer} is added to the global list of
3229 @node Guile Types Module
3230 @subsubsection Guile Types Module
3232 This module provides a collection of utilities for working with
3233 @code{<gdb:type>} objects.
3238 (use-modules (gdb types))
3241 @deffn {Scheme Procedure} get-basic-type type
3242 Return @var{type} with const and volatile qualifiers stripped,
3243 and with typedefs and C@t{++} references converted to the underlying type.
3248 typedef const int const_int;
3250 const_int& foo_ref (foo);
3251 int main () @{ return 0; @}
3258 (gdb) guile (use-modules ((gdb) (gdb types)))
3259 (gdb) guile (define foo-ref (parse-and-eval "foo_ref"))
3260 (gdb) guile (get-basic-type (value-type foo-ref))
3265 @deffn {Scheme Procedure} type-has-field-deep? type field
3266 Return @code{#t} if @var{type}, assumed to be a type with fields
3267 (e.g., a structure or union), has field @var{field}.
3268 Otherwise return @code{#f}.
3269 This searches baseclasses, whereas @code{type-has-field?} does not.
3272 @deffn {Scheme Procedure} make-enum-hashtable enum-type
3273 Return a Guile hash table produced from @var{enum-type}.
3274 Elements in the hash table are referenced with @code{hashq-ref}.