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618f726f | 1 | @c Copyright (C) 2008-2016 Free Software Foundation, Inc. |
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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 | |
5 | @c Invariant Sections being ``Free Software'' and ``Free Software Needs | |
6 | @c Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,'' | |
7 | @c and with the Back-Cover Texts as in (a) below. | |
8 | @c | |
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 | |
11 | @c developing GNU and promoting software freedom.'' | |
12 | ||
13 | @node Python | |
14 | @section Extending @value{GDBN} using Python | |
15 | @cindex python scripting | |
16 | @cindex scripting with python | |
17 | ||
18 | You can extend @value{GDBN} using the @uref{http://www.python.org/, | |
19 | Python programming language}. This feature is available only if | |
20 | @value{GDBN} was configured using @option{--with-python}. | |
21 | ||
22 | @cindex python directory | |
23 | Python scripts used by @value{GDBN} should be installed in | |
24 | @file{@var{data-directory}/python}, where @var{data-directory} is | |
25 | the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). | |
26 | This directory, known as the @dfn{python directory}, | |
27 | is automatically added to the Python Search Path in order to allow | |
28 | the Python interpreter to locate all scripts installed at this location. | |
29 | ||
30 | Additionally, @value{GDBN} commands and convenience functions which | |
31 | are written in Python and are located in the | |
32 | @file{@var{data-directory}/python/gdb/command} or | |
33 | @file{@var{data-directory}/python/gdb/function} directories are | |
34 | automatically imported when @value{GDBN} starts. | |
35 | ||
36 | @menu | |
37 | * Python Commands:: Accessing Python from @value{GDBN}. | |
38 | * Python API:: Accessing @value{GDBN} from Python. | |
39 | * Python Auto-loading:: Automatically loading Python code. | |
40 | * Python modules:: Python modules provided by @value{GDBN}. | |
41 | @end menu | |
42 | ||
43 | @node Python Commands | |
44 | @subsection Python Commands | |
45 | @cindex python commands | |
46 | @cindex commands to access python | |
47 | ||
48 | @value{GDBN} provides two commands for accessing the Python interpreter, | |
49 | and one related setting: | |
50 | ||
51 | @table @code | |
52 | @kindex python-interactive | |
53 | @kindex pi | |
54 | @item python-interactive @r{[}@var{command}@r{]} | |
55 | @itemx pi @r{[}@var{command}@r{]} | |
56 | Without an argument, the @code{python-interactive} command can be used | |
57 | to start an interactive Python prompt. To return to @value{GDBN}, | |
58 | type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt). | |
59 | ||
60 | Alternatively, a single-line Python command can be given as an | |
61 | argument and evaluated. If the command is an expression, the result | |
62 | will be printed; otherwise, nothing will be printed. For example: | |
63 | ||
64 | @smallexample | |
65 | (@value{GDBP}) python-interactive 2 + 3 | |
66 | 5 | |
67 | @end smallexample | |
68 | ||
69 | @kindex python | |
70 | @kindex py | |
71 | @item python @r{[}@var{command}@r{]} | |
72 | @itemx py @r{[}@var{command}@r{]} | |
73 | The @code{python} command can be used to evaluate Python code. | |
74 | ||
75 | If given an argument, the @code{python} command will evaluate the | |
76 | argument as a Python command. For example: | |
77 | ||
78 | @smallexample | |
79 | (@value{GDBP}) python print 23 | |
80 | 23 | |
81 | @end smallexample | |
82 | ||
83 | If you do not provide an argument to @code{python}, it will act as a | |
84 | multi-line command, like @code{define}. In this case, the Python | |
85 | script is made up of subsequent command lines, given after the | |
86 | @code{python} command. This command list is terminated using a line | |
87 | containing @code{end}. For example: | |
88 | ||
89 | @smallexample | |
90 | (@value{GDBP}) python | |
91 | Type python script | |
92 | End with a line saying just "end". | |
93 | >print 23 | |
94 | >end | |
95 | 23 | |
96 | @end smallexample | |
97 | ||
98 | @kindex set python print-stack | |
99 | @item set python print-stack | |
100 | By default, @value{GDBN} will print only the message component of a | |
101 | Python exception when an error occurs in a Python script. This can be | |
102 | controlled using @code{set python print-stack}: if @code{full}, then | |
103 | full Python stack printing is enabled; if @code{none}, then Python stack | |
104 | and message printing is disabled; if @code{message}, the default, only | |
105 | the message component of the error is printed. | |
106 | @end table | |
107 | ||
108 | It is also possible to execute a Python script from the @value{GDBN} | |
109 | interpreter: | |
110 | ||
111 | @table @code | |
112 | @item source @file{script-name} | |
113 | The script name must end with @samp{.py} and @value{GDBN} must be configured | |
114 | to recognize the script language based on filename extension using | |
115 | the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}. | |
116 | ||
117 | @item python execfile ("script-name") | |
118 | This method is based on the @code{execfile} Python built-in function, | |
119 | and thus is always available. | |
120 | @end table | |
121 | ||
122 | @node Python API | |
123 | @subsection Python API | |
124 | @cindex python api | |
125 | @cindex programming in python | |
126 | ||
127 | You can get quick online help for @value{GDBN}'s Python API by issuing | |
128 | the command @w{@kbd{python help (gdb)}}. | |
129 | ||
130 | Functions and methods which have two or more optional arguments allow | |
131 | them to be specified using keyword syntax. This allows passing some | |
132 | optional arguments while skipping others. Example: | |
133 | @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}. | |
134 | ||
135 | @menu | |
136 | * Basic Python:: Basic Python Functions. | |
137 | * Exception Handling:: How Python exceptions are translated. | |
138 | * Values From Inferior:: Python representation of values. | |
139 | * Types In Python:: Python representation of types. | |
140 | * Pretty Printing API:: Pretty-printing values. | |
141 | * Selecting Pretty-Printers:: How GDB chooses a pretty-printer. | |
142 | * Writing a Pretty-Printer:: Writing a Pretty-Printer. | |
143 | * Type Printing API:: Pretty-printing types. | |
144 | * Frame Filter API:: Filtering Frames. | |
145 | * Frame Decorator API:: Decorating Frames. | |
146 | * Writing a Frame Filter:: Writing a Frame Filter. | |
d11916aa | 147 | * Unwinding Frames in Python:: Writing frame unwinder. |
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148 | * Xmethods In Python:: Adding and replacing methods of C++ classes. |
149 | * Xmethod API:: Xmethod types. | |
150 | * Writing an Xmethod:: Writing an xmethod. | |
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151 | * Inferiors In Python:: Python representation of inferiors (processes) |
152 | * Events In Python:: Listening for events from @value{GDBN}. | |
153 | * Threads In Python:: Accessing inferior threads from Python. | |
154 | * Commands In Python:: Implementing new commands in Python. | |
155 | * Parameters In Python:: Adding new @value{GDBN} parameters. | |
156 | * Functions In Python:: Writing new convenience functions. | |
157 | * Progspaces In Python:: Program spaces. | |
158 | * Objfiles In Python:: Object files. | |
159 | * Frames In Python:: Accessing inferior stack frames from Python. | |
160 | * Blocks In Python:: Accessing blocks from Python. | |
161 | * Symbols In Python:: Python representation of symbols. | |
162 | * Symbol Tables In Python:: Python representation of symbol tables. | |
163 | * Line Tables In Python:: Python representation of line tables. | |
164 | * Breakpoints In Python:: Manipulating breakpoints using Python. | |
165 | * Finish Breakpoints in Python:: Setting Breakpoints on function return | |
166 | using Python. | |
167 | * Lazy Strings In Python:: Python representation of lazy strings. | |
168 | * Architectures In Python:: Python representation of architectures. | |
169 | @end menu | |
170 | ||
171 | @node Basic Python | |
172 | @subsubsection Basic Python | |
173 | ||
174 | @cindex python stdout | |
175 | @cindex python pagination | |
176 | At startup, @value{GDBN} overrides Python's @code{sys.stdout} and | |
177 | @code{sys.stderr} to print using @value{GDBN}'s output-paging streams. | |
178 | A Python program which outputs to one of these streams may have its | |
179 | output interrupted by the user (@pxref{Screen Size}). In this | |
180 | situation, a Python @code{KeyboardInterrupt} exception is thrown. | |
181 | ||
182 | Some care must be taken when writing Python code to run in | |
183 | @value{GDBN}. Two things worth noting in particular: | |
184 | ||
185 | @itemize @bullet | |
186 | @item | |
187 | @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}. | |
188 | Python code must not override these, or even change the options using | |
189 | @code{sigaction}. If your program changes the handling of these | |
190 | signals, @value{GDBN} will most likely stop working correctly. Note | |
191 | that it is unfortunately common for GUI toolkits to install a | |
192 | @code{SIGCHLD} handler. | |
193 | ||
194 | @item | |
195 | @value{GDBN} takes care to mark its internal file descriptors as | |
196 | close-on-exec. However, this cannot be done in a thread-safe way on | |
197 | all platforms. Your Python programs should be aware of this and | |
198 | should both create new file descriptors with the close-on-exec flag | |
199 | set and arrange to close unneeded file descriptors before starting a | |
200 | child process. | |
201 | @end itemize | |
202 | ||
203 | @cindex python functions | |
204 | @cindex python module | |
205 | @cindex gdb module | |
206 | @value{GDBN} introduces a new Python module, named @code{gdb}. All | |
207 | methods and classes added by @value{GDBN} are placed in this module. | |
208 | @value{GDBN} automatically @code{import}s the @code{gdb} module for | |
209 | use in all scripts evaluated by the @code{python} command. | |
210 | ||
211 | @findex gdb.PYTHONDIR | |
212 | @defvar gdb.PYTHONDIR | |
213 | A string containing the python directory (@pxref{Python}). | |
214 | @end defvar | |
215 | ||
216 | @findex gdb.execute | |
217 | @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]}) | |
218 | Evaluate @var{command}, a string, as a @value{GDBN} CLI command. | |
219 | If a GDB exception happens while @var{command} runs, it is | |
220 | translated as described in @ref{Exception Handling,,Exception Handling}. | |
221 | ||
697aa1b7 | 222 | The @var{from_tty} flag specifies whether @value{GDBN} ought to consider this |
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223 | command as having originated from the user invoking it interactively. |
224 | It must be a boolean value. If omitted, it defaults to @code{False}. | |
225 | ||
226 | By default, any output produced by @var{command} is sent to | |
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227 | @value{GDBN}'s standard output (and to the log output if logging is |
228 | turned on). If the @var{to_string} parameter is | |
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229 | @code{True}, then output will be collected by @code{gdb.execute} and |
230 | returned as a string. The default is @code{False}, in which case the | |
231 | return value is @code{None}. If @var{to_string} is @code{True}, the | |
232 | @value{GDBN} virtual terminal will be temporarily set to unlimited width | |
233 | and height, and its pagination will be disabled; @pxref{Screen Size}. | |
234 | @end defun | |
235 | ||
236 | @findex gdb.breakpoints | |
237 | @defun gdb.breakpoints () | |
238 | Return a sequence holding all of @value{GDBN}'s breakpoints. | |
239 | @xref{Breakpoints In Python}, for more information. | |
240 | @end defun | |
241 | ||
242 | @findex gdb.parameter | |
243 | @defun gdb.parameter (parameter) | |
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244 | Return the value of a @value{GDBN} @var{parameter} given by its name, |
245 | a string; the parameter name string may contain spaces if the parameter has a | |
246 | multi-part name. For example, @samp{print object} is a valid | |
247 | parameter name. | |
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248 | |
249 | If the named parameter does not exist, this function throws a | |
250 | @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the | |
251 | parameter's value is converted to a Python value of the appropriate | |
252 | type, and returned. | |
253 | @end defun | |
254 | ||
255 | @findex gdb.history | |
256 | @defun gdb.history (number) | |
257 | Return a value from @value{GDBN}'s value history (@pxref{Value | |
697aa1b7 | 258 | History}). The @var{number} argument indicates which history element to return. |
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259 | If @var{number} is negative, then @value{GDBN} will take its absolute value |
260 | and count backward from the last element (i.e., the most recent element) to | |
261 | find the value to return. If @var{number} is zero, then @value{GDBN} will | |
262 | return the most recent element. If the element specified by @var{number} | |
263 | doesn't exist in the value history, a @code{gdb.error} exception will be | |
264 | raised. | |
265 | ||
266 | If no exception is raised, the return value is always an instance of | |
267 | @code{gdb.Value} (@pxref{Values From Inferior}). | |
268 | @end defun | |
269 | ||
270 | @findex gdb.parse_and_eval | |
271 | @defun gdb.parse_and_eval (expression) | |
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272 | Parse @var{expression}, which must be a string, as an expression in |
273 | the current language, evaluate it, and return the result as a | |
274 | @code{gdb.Value}. | |
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275 | |
276 | This function can be useful when implementing a new command | |
277 | (@pxref{Commands In Python}), as it provides a way to parse the | |
278 | command's argument as an expression. It is also useful simply to | |
279 | compute values, for example, it is the only way to get the value of a | |
280 | convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}. | |
281 | @end defun | |
282 | ||
283 | @findex gdb.find_pc_line | |
284 | @defun gdb.find_pc_line (pc) | |
285 | Return the @code{gdb.Symtab_and_line} object corresponding to the | |
286 | @var{pc} value. @xref{Symbol Tables In Python}. If an invalid | |
287 | value of @var{pc} is passed as an argument, then the @code{symtab} and | |
288 | @code{line} attributes of the returned @code{gdb.Symtab_and_line} object | |
289 | will be @code{None} and 0 respectively. | |
290 | @end defun | |
291 | ||
292 | @findex gdb.post_event | |
293 | @defun gdb.post_event (event) | |
294 | Put @var{event}, a callable object taking no arguments, into | |
295 | @value{GDBN}'s internal event queue. This callable will be invoked at | |
296 | some later point, during @value{GDBN}'s event processing. Events | |
297 | posted using @code{post_event} will be run in the order in which they | |
298 | were posted; however, there is no way to know when they will be | |
299 | processed relative to other events inside @value{GDBN}. | |
300 | ||
301 | @value{GDBN} is not thread-safe. If your Python program uses multiple | |
302 | threads, you must be careful to only call @value{GDBN}-specific | |
b3ce5e5f | 303 | functions in the @value{GDBN} thread. @code{post_event} ensures |
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304 | this. For example: |
305 | ||
306 | @smallexample | |
307 | (@value{GDBP}) python | |
308 | >import threading | |
309 | > | |
310 | >class Writer(): | |
311 | > def __init__(self, message): | |
312 | > self.message = message; | |
313 | > def __call__(self): | |
314 | > gdb.write(self.message) | |
315 | > | |
316 | >class MyThread1 (threading.Thread): | |
317 | > def run (self): | |
318 | > gdb.post_event(Writer("Hello ")) | |
319 | > | |
320 | >class MyThread2 (threading.Thread): | |
321 | > def run (self): | |
322 | > gdb.post_event(Writer("World\n")) | |
323 | > | |
324 | >MyThread1().start() | |
325 | >MyThread2().start() | |
326 | >end | |
327 | (@value{GDBP}) Hello World | |
328 | @end smallexample | |
329 | @end defun | |
330 | ||
331 | @findex gdb.write | |
332 | @defun gdb.write (string @r{[}, stream{]}) | |
333 | Print a string to @value{GDBN}'s paginated output stream. The | |
334 | optional @var{stream} determines the stream to print to. The default | |
335 | stream is @value{GDBN}'s standard output stream. Possible stream | |
336 | values are: | |
337 | ||
338 | @table @code | |
339 | @findex STDOUT | |
340 | @findex gdb.STDOUT | |
341 | @item gdb.STDOUT | |
342 | @value{GDBN}'s standard output stream. | |
343 | ||
344 | @findex STDERR | |
345 | @findex gdb.STDERR | |
346 | @item gdb.STDERR | |
347 | @value{GDBN}'s standard error stream. | |
348 | ||
349 | @findex STDLOG | |
350 | @findex gdb.STDLOG | |
351 | @item gdb.STDLOG | |
352 | @value{GDBN}'s log stream (@pxref{Logging Output}). | |
353 | @end table | |
354 | ||
355 | Writing to @code{sys.stdout} or @code{sys.stderr} will automatically | |
356 | call this function and will automatically direct the output to the | |
357 | relevant stream. | |
358 | @end defun | |
359 | ||
360 | @findex gdb.flush | |
361 | @defun gdb.flush () | |
362 | Flush the buffer of a @value{GDBN} paginated stream so that the | |
363 | contents are displayed immediately. @value{GDBN} will flush the | |
364 | contents of a stream automatically when it encounters a newline in the | |
365 | buffer. The optional @var{stream} determines the stream to flush. The | |
366 | default stream is @value{GDBN}'s standard output stream. Possible | |
367 | stream values are: | |
368 | ||
369 | @table @code | |
370 | @findex STDOUT | |
371 | @findex gdb.STDOUT | |
372 | @item gdb.STDOUT | |
373 | @value{GDBN}'s standard output stream. | |
374 | ||
375 | @findex STDERR | |
376 | @findex gdb.STDERR | |
377 | @item gdb.STDERR | |
378 | @value{GDBN}'s standard error stream. | |
379 | ||
380 | @findex STDLOG | |
381 | @findex gdb.STDLOG | |
382 | @item gdb.STDLOG | |
383 | @value{GDBN}'s log stream (@pxref{Logging Output}). | |
384 | ||
385 | @end table | |
386 | ||
387 | Flushing @code{sys.stdout} or @code{sys.stderr} will automatically | |
388 | call this function for the relevant stream. | |
389 | @end defun | |
390 | ||
391 | @findex gdb.target_charset | |
392 | @defun gdb.target_charset () | |
393 | Return the name of the current target character set (@pxref{Character | |
394 | Sets}). This differs from @code{gdb.parameter('target-charset')} in | |
395 | that @samp{auto} is never returned. | |
396 | @end defun | |
397 | ||
398 | @findex gdb.target_wide_charset | |
399 | @defun gdb.target_wide_charset () | |
400 | Return the name of the current target wide character set | |
401 | (@pxref{Character Sets}). This differs from | |
402 | @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is | |
403 | never returned. | |
404 | @end defun | |
405 | ||
406 | @findex gdb.solib_name | |
407 | @defun gdb.solib_name (address) | |
408 | Return the name of the shared library holding the given @var{address} | |
409 | as a string, or @code{None}. | |
410 | @end defun | |
411 | ||
412 | @findex gdb.decode_line | |
413 | @defun gdb.decode_line @r{[}expression@r{]} | |
414 | Return locations of the line specified by @var{expression}, or of the | |
415 | current line if no argument was given. This function returns a Python | |
416 | tuple containing two elements. The first element contains a string | |
417 | holding any unparsed section of @var{expression} (or @code{None} if | |
418 | the expression has been fully parsed). The second element contains | |
419 | either @code{None} or another tuple that contains all the locations | |
420 | that match the expression represented as @code{gdb.Symtab_and_line} | |
421 | objects (@pxref{Symbol Tables In Python}). If @var{expression} is | |
422 | provided, it is decoded the way that @value{GDBN}'s inbuilt | |
423 | @code{break} or @code{edit} commands do (@pxref{Specify Location}). | |
424 | @end defun | |
425 | ||
426 | @defun gdb.prompt_hook (current_prompt) | |
427 | @anchor{prompt_hook} | |
428 | ||
429 | If @var{prompt_hook} is callable, @value{GDBN} will call the method | |
430 | assigned to this operation before a prompt is displayed by | |
431 | @value{GDBN}. | |
432 | ||
433 | The parameter @code{current_prompt} contains the current @value{GDBN} | |
434 | prompt. This method must return a Python string, or @code{None}. If | |
435 | a string is returned, the @value{GDBN} prompt will be set to that | |
436 | string. If @code{None} is returned, @value{GDBN} will continue to use | |
437 | the current prompt. | |
438 | ||
439 | Some prompts cannot be substituted in @value{GDBN}. Secondary prompts | |
440 | such as those used by readline for command input, and annotation | |
441 | related prompts are prohibited from being changed. | |
442 | @end defun | |
443 | ||
444 | @node Exception Handling | |
445 | @subsubsection Exception Handling | |
446 | @cindex python exceptions | |
447 | @cindex exceptions, python | |
448 | ||
449 | When executing the @code{python} command, Python exceptions | |
450 | uncaught within the Python code are translated to calls to | |
451 | @value{GDBN} error-reporting mechanism. If the command that called | |
452 | @code{python} does not handle the error, @value{GDBN} will | |
453 | terminate it and print an error message containing the Python | |
454 | exception name, the associated value, and the Python call stack | |
455 | backtrace at the point where the exception was raised. Example: | |
456 | ||
457 | @smallexample | |
458 | (@value{GDBP}) python print foo | |
459 | Traceback (most recent call last): | |
460 | File "<string>", line 1, in <module> | |
461 | NameError: name 'foo' is not defined | |
462 | @end smallexample | |
463 | ||
464 | @value{GDBN} errors that happen in @value{GDBN} commands invoked by | |
465 | Python code are converted to Python exceptions. The type of the | |
466 | Python exception depends on the error. | |
467 | ||
468 | @ftable @code | |
469 | @item gdb.error | |
470 | This is the base class for most exceptions generated by @value{GDBN}. | |
471 | It is derived from @code{RuntimeError}, for compatibility with earlier | |
472 | versions of @value{GDBN}. | |
473 | ||
474 | If an error occurring in @value{GDBN} does not fit into some more | |
475 | specific category, then the generated exception will have this type. | |
476 | ||
477 | @item gdb.MemoryError | |
478 | This is a subclass of @code{gdb.error} which is thrown when an | |
479 | operation tried to access invalid memory in the inferior. | |
480 | ||
481 | @item KeyboardInterrupt | |
482 | User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination | |
483 | prompt) is translated to a Python @code{KeyboardInterrupt} exception. | |
484 | @end ftable | |
485 | ||
486 | In all cases, your exception handler will see the @value{GDBN} error | |
487 | message as its value and the Python call stack backtrace at the Python | |
488 | statement closest to where the @value{GDBN} error occured as the | |
489 | traceback. | |
490 | ||
491 | @findex gdb.GdbError | |
492 | When implementing @value{GDBN} commands in Python via @code{gdb.Command}, | |
493 | it is useful to be able to throw an exception that doesn't cause a | |
494 | traceback to be printed. For example, the user may have invoked the | |
495 | command incorrectly. Use the @code{gdb.GdbError} exception | |
496 | to handle this case. Example: | |
497 | ||
498 | @smallexample | |
499 | (gdb) python | |
500 | >class HelloWorld (gdb.Command): | |
501 | > """Greet the whole world.""" | |
502 | > def __init__ (self): | |
503 | > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) | |
504 | > def invoke (self, args, from_tty): | |
505 | > argv = gdb.string_to_argv (args) | |
506 | > if len (argv) != 0: | |
507 | > raise gdb.GdbError ("hello-world takes no arguments") | |
508 | > print "Hello, World!" | |
509 | >HelloWorld () | |
510 | >end | |
511 | (gdb) hello-world 42 | |
512 | hello-world takes no arguments | |
513 | @end smallexample | |
514 | ||
515 | @node Values From Inferior | |
516 | @subsubsection Values From Inferior | |
517 | @cindex values from inferior, with Python | |
518 | @cindex python, working with values from inferior | |
519 | ||
520 | @cindex @code{gdb.Value} | |
521 | @value{GDBN} provides values it obtains from the inferior program in | |
522 | an object of type @code{gdb.Value}. @value{GDBN} uses this object | |
523 | for its internal bookkeeping of the inferior's values, and for | |
524 | fetching values when necessary. | |
525 | ||
526 | Inferior values that are simple scalars can be used directly in | |
527 | Python expressions that are valid for the value's data type. Here's | |
528 | an example for an integer or floating-point value @code{some_val}: | |
529 | ||
530 | @smallexample | |
531 | bar = some_val + 2 | |
532 | @end smallexample | |
533 | ||
534 | @noindent | |
535 | As result of this, @code{bar} will also be a @code{gdb.Value} object | |
f7bd0f78 SC |
536 | whose values are of the same type as those of @code{some_val}. Valid |
537 | Python operations can also be performed on @code{gdb.Value} objects | |
538 | representing a @code{struct} or @code{class} object. For such cases, | |
539 | the overloaded operator (if present), is used to perform the operation. | |
540 | For example, if @code{val1} and @code{val2} are @code{gdb.Value} objects | |
541 | representing instances of a @code{class} which overloads the @code{+} | |
542 | operator, then one can use the @code{+} operator in their Python script | |
543 | as follows: | |
544 | ||
545 | @smallexample | |
546 | val3 = val1 + val2 | |
547 | @end smallexample | |
548 | ||
549 | @noindent | |
550 | The result of the operation @code{val3} is also a @code{gdb.Value} | |
551 | object corresponding to the value returned by the overloaded @code{+} | |
552 | operator. In general, overloaded operators are invoked for the | |
553 | following operations: @code{+} (binary addition), @code{-} (binary | |
554 | subtraction), @code{*} (multiplication), @code{/}, @code{%}, @code{<<}, | |
555 | @code{>>}, @code{|}, @code{&}, @code{^}. | |
329baa95 DE |
556 | |
557 | Inferior values that are structures or instances of some class can | |
558 | be accessed using the Python @dfn{dictionary syntax}. For example, if | |
559 | @code{some_val} is a @code{gdb.Value} instance holding a structure, you | |
560 | can access its @code{foo} element with: | |
561 | ||
562 | @smallexample | |
563 | bar = some_val['foo'] | |
564 | @end smallexample | |
565 | ||
566 | @cindex getting structure elements using gdb.Field objects as subscripts | |
567 | Again, @code{bar} will also be a @code{gdb.Value} object. Structure | |
568 | elements can also be accessed by using @code{gdb.Field} objects as | |
569 | subscripts (@pxref{Types In Python}, for more information on | |
570 | @code{gdb.Field} objects). For example, if @code{foo_field} is a | |
571 | @code{gdb.Field} object corresponding to element @code{foo} of the above | |
572 | structure, then @code{bar} can also be accessed as follows: | |
573 | ||
574 | @smallexample | |
575 | bar = some_val[foo_field] | |
576 | @end smallexample | |
577 | ||
578 | A @code{gdb.Value} that represents a function can be executed via | |
579 | inferior function call. Any arguments provided to the call must match | |
580 | the function's prototype, and must be provided in the order specified | |
581 | by that prototype. | |
582 | ||
583 | For example, @code{some_val} is a @code{gdb.Value} instance | |
584 | representing a function that takes two integers as arguments. To | |
585 | execute this function, call it like so: | |
586 | ||
587 | @smallexample | |
588 | result = some_val (10,20) | |
589 | @end smallexample | |
590 | ||
591 | Any values returned from a function call will be stored as a | |
592 | @code{gdb.Value}. | |
593 | ||
594 | The following attributes are provided: | |
595 | ||
596 | @defvar Value.address | |
597 | If this object is addressable, this read-only attribute holds a | |
598 | @code{gdb.Value} object representing the address. Otherwise, | |
599 | this attribute holds @code{None}. | |
600 | @end defvar | |
601 | ||
602 | @cindex optimized out value in Python | |
603 | @defvar Value.is_optimized_out | |
604 | This read-only boolean attribute is true if the compiler optimized out | |
605 | this value, thus it is not available for fetching from the inferior. | |
606 | @end defvar | |
607 | ||
608 | @defvar Value.type | |
609 | The type of this @code{gdb.Value}. The value of this attribute is a | |
610 | @code{gdb.Type} object (@pxref{Types In Python}). | |
611 | @end defvar | |
612 | ||
613 | @defvar Value.dynamic_type | |
614 | The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time | |
615 | type information (@acronym{RTTI}) to determine the dynamic type of the | |
616 | value. If this value is of class type, it will return the class in | |
617 | which the value is embedded, if any. If this value is of pointer or | |
618 | reference to a class type, it will compute the dynamic type of the | |
619 | referenced object, and return a pointer or reference to that type, | |
620 | respectively. In all other cases, it will return the value's static | |
621 | type. | |
622 | ||
623 | Note that this feature will only work when debugging a C@t{++} program | |
624 | that includes @acronym{RTTI} for the object in question. Otherwise, | |
625 | it will just return the static type of the value as in @kbd{ptype foo} | |
626 | (@pxref{Symbols, ptype}). | |
627 | @end defvar | |
628 | ||
629 | @defvar Value.is_lazy | |
630 | The value of this read-only boolean attribute is @code{True} if this | |
631 | @code{gdb.Value} has not yet been fetched from the inferior. | |
632 | @value{GDBN} does not fetch values until necessary, for efficiency. | |
633 | For example: | |
634 | ||
635 | @smallexample | |
636 | myval = gdb.parse_and_eval ('somevar') | |
637 | @end smallexample | |
638 | ||
639 | The value of @code{somevar} is not fetched at this time. It will be | |
640 | fetched when the value is needed, or when the @code{fetch_lazy} | |
641 | method is invoked. | |
642 | @end defvar | |
643 | ||
644 | The following methods are provided: | |
645 | ||
646 | @defun Value.__init__ (@var{val}) | |
647 | Many Python values can be converted directly to a @code{gdb.Value} via | |
648 | this object initializer. Specifically: | |
649 | ||
650 | @table @asis | |
651 | @item Python boolean | |
652 | A Python boolean is converted to the boolean type from the current | |
653 | language. | |
654 | ||
655 | @item Python integer | |
656 | A Python integer is converted to the C @code{long} type for the | |
657 | current architecture. | |
658 | ||
659 | @item Python long | |
660 | A Python long is converted to the C @code{long long} type for the | |
661 | current architecture. | |
662 | ||
663 | @item Python float | |
664 | A Python float is converted to the C @code{double} type for the | |
665 | current architecture. | |
666 | ||
667 | @item Python string | |
b3ce5e5f DE |
668 | A Python string is converted to a target string in the current target |
669 | language using the current target encoding. | |
670 | If a character cannot be represented in the current target encoding, | |
671 | then an exception is thrown. | |
329baa95 DE |
672 | |
673 | @item @code{gdb.Value} | |
674 | If @code{val} is a @code{gdb.Value}, then a copy of the value is made. | |
675 | ||
676 | @item @code{gdb.LazyString} | |
677 | If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In | |
678 | Python}), then the lazy string's @code{value} method is called, and | |
679 | its result is used. | |
680 | @end table | |
681 | @end defun | |
682 | ||
683 | @defun Value.cast (type) | |
684 | Return a new instance of @code{gdb.Value} that is the result of | |
685 | casting this instance to the type described by @var{type}, which must | |
686 | be a @code{gdb.Type} object. If the cast cannot be performed for some | |
687 | reason, this method throws an exception. | |
688 | @end defun | |
689 | ||
690 | @defun Value.dereference () | |
691 | For pointer data types, this method returns a new @code{gdb.Value} object | |
692 | whose contents is the object pointed to by the pointer. For example, if | |
693 | @code{foo} is a C pointer to an @code{int}, declared in your C program as | |
694 | ||
695 | @smallexample | |
696 | int *foo; | |
697 | @end smallexample | |
698 | ||
699 | @noindent | |
700 | then you can use the corresponding @code{gdb.Value} to access what | |
701 | @code{foo} points to like this: | |
702 | ||
703 | @smallexample | |
704 | bar = foo.dereference () | |
705 | @end smallexample | |
706 | ||
707 | The result @code{bar} will be a @code{gdb.Value} object holding the | |
708 | value pointed to by @code{foo}. | |
709 | ||
710 | A similar function @code{Value.referenced_value} exists which also | |
711 | returns @code{gdb.Value} objects corresonding to the values pointed to | |
712 | by pointer values (and additionally, values referenced by reference | |
713 | values). However, the behavior of @code{Value.dereference} | |
714 | differs from @code{Value.referenced_value} by the fact that the | |
715 | behavior of @code{Value.dereference} is identical to applying the C | |
716 | unary operator @code{*} on a given value. For example, consider a | |
717 | reference to a pointer @code{ptrref}, declared in your C@t{++} program | |
718 | as | |
719 | ||
720 | @smallexample | |
721 | typedef int *intptr; | |
722 | ... | |
723 | int val = 10; | |
724 | intptr ptr = &val; | |
725 | intptr &ptrref = ptr; | |
726 | @end smallexample | |
727 | ||
728 | Though @code{ptrref} is a reference value, one can apply the method | |
729 | @code{Value.dereference} to the @code{gdb.Value} object corresponding | |
730 | to it and obtain a @code{gdb.Value} which is identical to that | |
731 | corresponding to @code{val}. However, if you apply the method | |
732 | @code{Value.referenced_value}, the result would be a @code{gdb.Value} | |
733 | object identical to that corresponding to @code{ptr}. | |
734 | ||
735 | @smallexample | |
736 | py_ptrref = gdb.parse_and_eval ("ptrref") | |
737 | py_val = py_ptrref.dereference () | |
738 | py_ptr = py_ptrref.referenced_value () | |
739 | @end smallexample | |
740 | ||
741 | The @code{gdb.Value} object @code{py_val} is identical to that | |
742 | corresponding to @code{val}, and @code{py_ptr} is identical to that | |
743 | corresponding to @code{ptr}. In general, @code{Value.dereference} can | |
744 | be applied whenever the C unary operator @code{*} can be applied | |
745 | to the corresponding C value. For those cases where applying both | |
746 | @code{Value.dereference} and @code{Value.referenced_value} is allowed, | |
747 | the results obtained need not be identical (as we have seen in the above | |
748 | example). The results are however identical when applied on | |
749 | @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value} | |
750 | objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program. | |
751 | @end defun | |
752 | ||
753 | @defun Value.referenced_value () | |
754 | For pointer or reference data types, this method returns a new | |
755 | @code{gdb.Value} object corresponding to the value referenced by the | |
756 | pointer/reference value. For pointer data types, | |
757 | @code{Value.dereference} and @code{Value.referenced_value} produce | |
758 | identical results. The difference between these methods is that | |
759 | @code{Value.dereference} cannot get the values referenced by reference | |
760 | values. For example, consider a reference to an @code{int}, declared | |
761 | in your C@t{++} program as | |
762 | ||
763 | @smallexample | |
764 | int val = 10; | |
765 | int &ref = val; | |
766 | @end smallexample | |
767 | ||
768 | @noindent | |
769 | then applying @code{Value.dereference} to the @code{gdb.Value} object | |
770 | corresponding to @code{ref} will result in an error, while applying | |
771 | @code{Value.referenced_value} will result in a @code{gdb.Value} object | |
772 | identical to that corresponding to @code{val}. | |
773 | ||
774 | @smallexample | |
775 | py_ref = gdb.parse_and_eval ("ref") | |
776 | er_ref = py_ref.dereference () # Results in error | |
777 | py_val = py_ref.referenced_value () # Returns the referenced value | |
778 | @end smallexample | |
779 | ||
780 | The @code{gdb.Value} object @code{py_val} is identical to that | |
781 | corresponding to @code{val}. | |
782 | @end defun | |
783 | ||
4c082a81 SC |
784 | @defun Value.reference_value () |
785 | Return a @code{gdb.Value} object which is a reference to the value | |
786 | encapsulated by this instance. | |
787 | @end defun | |
788 | ||
789 | @defun Value.const_value () | |
790 | Return a @code{gdb.Value} object which is a @code{const} version of the | |
791 | value encapsulated by this instance. | |
792 | @end defun | |
793 | ||
329baa95 DE |
794 | @defun Value.dynamic_cast (type) |
795 | Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast} | |
796 | operator were used. Consult a C@t{++} reference for details. | |
797 | @end defun | |
798 | ||
799 | @defun Value.reinterpret_cast (type) | |
800 | Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast} | |
801 | operator were used. Consult a C@t{++} reference for details. | |
802 | @end defun | |
803 | ||
804 | @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]}) | |
805 | If this @code{gdb.Value} represents a string, then this method | |
806 | converts the contents to a Python string. Otherwise, this method will | |
807 | throw an exception. | |
808 | ||
b3ce5e5f DE |
809 | Values are interpreted as strings according to the rules of the |
810 | current language. If the optional length argument is given, the | |
811 | string will be converted to that length, and will include any embedded | |
812 | zeroes that the string may contain. Otherwise, for languages | |
813 | where the string is zero-terminated, the entire string will be | |
814 | converted. | |
329baa95 | 815 | |
b3ce5e5f DE |
816 | For example, in C-like languages, a value is a string if it is a pointer |
817 | to or an array of characters or ints of type @code{wchar_t}, @code{char16_t}, | |
818 | or @code{char32_t}. | |
329baa95 DE |
819 | |
820 | If the optional @var{encoding} argument is given, it must be a string | |
821 | naming the encoding of the string in the @code{gdb.Value}, such as | |
822 | @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts | |
823 | the same encodings as the corresponding argument to Python's | |
824 | @code{string.decode} method, and the Python codec machinery will be used | |
825 | to convert the string. If @var{encoding} is not given, or if | |
826 | @var{encoding} is the empty string, then either the @code{target-charset} | |
827 | (@pxref{Character Sets}) will be used, or a language-specific encoding | |
828 | will be used, if the current language is able to supply one. | |
829 | ||
830 | The optional @var{errors} argument is the same as the corresponding | |
831 | argument to Python's @code{string.decode} method. | |
832 | ||
833 | If the optional @var{length} argument is given, the string will be | |
834 | fetched and converted to the given length. | |
835 | @end defun | |
836 | ||
837 | @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]}) | |
838 | If this @code{gdb.Value} represents a string, then this method | |
839 | converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings | |
840 | In Python}). Otherwise, this method will throw an exception. | |
841 | ||
842 | If the optional @var{encoding} argument is given, it must be a string | |
843 | naming the encoding of the @code{gdb.LazyString}. Some examples are: | |
844 | @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the | |
845 | @var{encoding} argument is an encoding that @value{GDBN} does | |
846 | recognize, @value{GDBN} will raise an error. | |
847 | ||
848 | When a lazy string is printed, the @value{GDBN} encoding machinery is | |
849 | used to convert the string during printing. If the optional | |
850 | @var{encoding} argument is not provided, or is an empty string, | |
851 | @value{GDBN} will automatically select the encoding most suitable for | |
852 | the string type. For further information on encoding in @value{GDBN} | |
853 | please see @ref{Character Sets}. | |
854 | ||
855 | If the optional @var{length} argument is given, the string will be | |
856 | fetched and encoded to the length of characters specified. If | |
857 | the @var{length} argument is not provided, the string will be fetched | |
858 | and encoded until a null of appropriate width is found. | |
859 | @end defun | |
860 | ||
861 | @defun Value.fetch_lazy () | |
862 | If the @code{gdb.Value} object is currently a lazy value | |
863 | (@code{gdb.Value.is_lazy} is @code{True}), then the value is | |
864 | fetched from the inferior. Any errors that occur in the process | |
865 | will produce a Python exception. | |
866 | ||
867 | If the @code{gdb.Value} object is not a lazy value, this method | |
868 | has no effect. | |
869 | ||
870 | This method does not return a value. | |
871 | @end defun | |
872 | ||
873 | ||
874 | @node Types In Python | |
875 | @subsubsection Types In Python | |
876 | @cindex types in Python | |
877 | @cindex Python, working with types | |
878 | ||
879 | @tindex gdb.Type | |
880 | @value{GDBN} represents types from the inferior using the class | |
881 | @code{gdb.Type}. | |
882 | ||
883 | The following type-related functions are available in the @code{gdb} | |
884 | module: | |
885 | ||
886 | @findex gdb.lookup_type | |
887 | @defun gdb.lookup_type (name @r{[}, block@r{]}) | |
697aa1b7 | 888 | This function looks up a type by its @var{name}, which must be a string. |
329baa95 DE |
889 | |
890 | If @var{block} is given, then @var{name} is looked up in that scope. | |
891 | Otherwise, it is searched for globally. | |
892 | ||
893 | Ordinarily, this function will return an instance of @code{gdb.Type}. | |
894 | If the named type cannot be found, it will throw an exception. | |
895 | @end defun | |
896 | ||
897 | If the type is a structure or class type, or an enum type, the fields | |
898 | of that type can be accessed using the Python @dfn{dictionary syntax}. | |
899 | For example, if @code{some_type} is a @code{gdb.Type} instance holding | |
900 | a structure type, you can access its @code{foo} field with: | |
901 | ||
902 | @smallexample | |
903 | bar = some_type['foo'] | |
904 | @end smallexample | |
905 | ||
906 | @code{bar} will be a @code{gdb.Field} object; see below under the | |
907 | description of the @code{Type.fields} method for a description of the | |
908 | @code{gdb.Field} class. | |
909 | ||
910 | An instance of @code{Type} has the following attributes: | |
911 | ||
912 | @defvar Type.code | |
913 | The type code for this type. The type code will be one of the | |
914 | @code{TYPE_CODE_} constants defined below. | |
915 | @end defvar | |
916 | ||
917 | @defvar Type.name | |
918 | The name of this type. If this type has no name, then @code{None} | |
919 | is returned. | |
920 | @end defvar | |
921 | ||
922 | @defvar Type.sizeof | |
923 | The size of this type, in target @code{char} units. Usually, a | |
924 | target's @code{char} type will be an 8-bit byte. However, on some | |
925 | unusual platforms, this type may have a different size. | |
926 | @end defvar | |
927 | ||
928 | @defvar Type.tag | |
929 | The tag name for this type. The tag name is the name after | |
930 | @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all | |
931 | languages have this concept. If this type has no tag name, then | |
932 | @code{None} is returned. | |
933 | @end defvar | |
934 | ||
935 | The following methods are provided: | |
936 | ||
937 | @defun Type.fields () | |
938 | For structure and union types, this method returns the fields. Range | |
939 | types have two fields, the minimum and maximum values. Enum types | |
940 | have one field per enum constant. Function and method types have one | |
941 | field per parameter. The base types of C@t{++} classes are also | |
942 | represented as fields. If the type has no fields, or does not fit | |
943 | into one of these categories, an empty sequence will be returned. | |
944 | ||
945 | Each field is a @code{gdb.Field} object, with some pre-defined attributes: | |
946 | @table @code | |
947 | @item bitpos | |
948 | This attribute is not available for @code{enum} or @code{static} | |
949 | (as in C@t{++} or Java) fields. The value is the position, counting | |
950 | in bits, from the start of the containing type. | |
951 | ||
952 | @item enumval | |
953 | This attribute is only available for @code{enum} fields, and its value | |
954 | is the enumeration member's integer representation. | |
955 | ||
956 | @item name | |
957 | The name of the field, or @code{None} for anonymous fields. | |
958 | ||
959 | @item artificial | |
960 | This is @code{True} if the field is artificial, usually meaning that | |
961 | it was provided by the compiler and not the user. This attribute is | |
962 | always provided, and is @code{False} if the field is not artificial. | |
963 | ||
964 | @item is_base_class | |
965 | This is @code{True} if the field represents a base class of a C@t{++} | |
966 | structure. This attribute is always provided, and is @code{False} | |
967 | if the field is not a base class of the type that is the argument of | |
968 | @code{fields}, or if that type was not a C@t{++} class. | |
969 | ||
970 | @item bitsize | |
971 | If the field is packed, or is a bitfield, then this will have a | |
972 | non-zero value, which is the size of the field in bits. Otherwise, | |
973 | this will be zero; in this case the field's size is given by its type. | |
974 | ||
975 | @item type | |
976 | The type of the field. This is usually an instance of @code{Type}, | |
977 | but it can be @code{None} in some situations. | |
978 | ||
979 | @item parent_type | |
980 | The type which contains this field. This is an instance of | |
981 | @code{gdb.Type}. | |
982 | @end table | |
983 | @end defun | |
984 | ||
985 | @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]}) | |
986 | Return a new @code{gdb.Type} object which represents an array of this | |
987 | type. If one argument is given, it is the inclusive upper bound of | |
988 | the array; in this case the lower bound is zero. If two arguments are | |
989 | given, the first argument is the lower bound of the array, and the | |
990 | second argument is the upper bound of the array. An array's length | |
991 | must not be negative, but the bounds can be. | |
992 | @end defun | |
993 | ||
994 | @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]}) | |
995 | Return a new @code{gdb.Type} object which represents a vector of this | |
996 | type. If one argument is given, it is the inclusive upper bound of | |
997 | the vector; in this case the lower bound is zero. If two arguments are | |
998 | given, the first argument is the lower bound of the vector, and the | |
999 | second argument is the upper bound of the vector. A vector's length | |
1000 | must not be negative, but the bounds can be. | |
1001 | ||
1002 | The difference between an @code{array} and a @code{vector} is that | |
1003 | arrays behave like in C: when used in expressions they decay to a pointer | |
1004 | to the first element whereas vectors are treated as first class values. | |
1005 | @end defun | |
1006 | ||
1007 | @defun Type.const () | |
1008 | Return a new @code{gdb.Type} object which represents a | |
1009 | @code{const}-qualified variant of this type. | |
1010 | @end defun | |
1011 | ||
1012 | @defun Type.volatile () | |
1013 | Return a new @code{gdb.Type} object which represents a | |
1014 | @code{volatile}-qualified variant of this type. | |
1015 | @end defun | |
1016 | ||
1017 | @defun Type.unqualified () | |
1018 | Return a new @code{gdb.Type} object which represents an unqualified | |
1019 | variant of this type. That is, the result is neither @code{const} nor | |
1020 | @code{volatile}. | |
1021 | @end defun | |
1022 | ||
1023 | @defun Type.range () | |
1024 | Return a Python @code{Tuple} object that contains two elements: the | |
1025 | low bound of the argument type and the high bound of that type. If | |
1026 | the type does not have a range, @value{GDBN} will raise a | |
1027 | @code{gdb.error} exception (@pxref{Exception Handling}). | |
1028 | @end defun | |
1029 | ||
1030 | @defun Type.reference () | |
1031 | Return a new @code{gdb.Type} object which represents a reference to this | |
1032 | type. | |
1033 | @end defun | |
1034 | ||
1035 | @defun Type.pointer () | |
1036 | Return a new @code{gdb.Type} object which represents a pointer to this | |
1037 | type. | |
1038 | @end defun | |
1039 | ||
1040 | @defun Type.strip_typedefs () | |
1041 | Return a new @code{gdb.Type} that represents the real type, | |
1042 | after removing all layers of typedefs. | |
1043 | @end defun | |
1044 | ||
1045 | @defun Type.target () | |
1046 | Return a new @code{gdb.Type} object which represents the target type | |
1047 | of this type. | |
1048 | ||
1049 | For a pointer type, the target type is the type of the pointed-to | |
1050 | object. For an array type (meaning C-like arrays), the target type is | |
1051 | the type of the elements of the array. For a function or method type, | |
1052 | the target type is the type of the return value. For a complex type, | |
1053 | the target type is the type of the elements. For a typedef, the | |
1054 | target type is the aliased type. | |
1055 | ||
1056 | If the type does not have a target, this method will throw an | |
1057 | exception. | |
1058 | @end defun | |
1059 | ||
1060 | @defun Type.template_argument (n @r{[}, block@r{]}) | |
1061 | If this @code{gdb.Type} is an instantiation of a template, this will | |
1a6a384b JL |
1062 | return a new @code{gdb.Value} or @code{gdb.Type} which represents the |
1063 | value of the @var{n}th template argument (indexed starting at 0). | |
329baa95 | 1064 | |
1a6a384b JL |
1065 | If this @code{gdb.Type} is not a template type, or if the type has fewer |
1066 | than @var{n} template arguments, this will throw an exception. | |
1067 | Ordinarily, only C@t{++} code will have template types. | |
329baa95 DE |
1068 | |
1069 | If @var{block} is given, then @var{name} is looked up in that scope. | |
1070 | Otherwise, it is searched for globally. | |
1071 | @end defun | |
1072 | ||
59fb7612 SS |
1073 | @defun Type.optimized_out () |
1074 | Return @code{gdb.Value} instance of this type whose value is optimized | |
1075 | out. This allows a frame decorator to indicate that the value of an | |
1076 | argument or a local variable is not known. | |
1077 | @end defun | |
329baa95 DE |
1078 | |
1079 | Each type has a code, which indicates what category this type falls | |
1080 | into. The available type categories are represented by constants | |
1081 | defined in the @code{gdb} module: | |
1082 | ||
b3ce5e5f DE |
1083 | @vtable @code |
1084 | @vindex TYPE_CODE_PTR | |
329baa95 DE |
1085 | @item gdb.TYPE_CODE_PTR |
1086 | The type is a pointer. | |
1087 | ||
b3ce5e5f | 1088 | @vindex TYPE_CODE_ARRAY |
329baa95 DE |
1089 | @item gdb.TYPE_CODE_ARRAY |
1090 | The type is an array. | |
1091 | ||
b3ce5e5f | 1092 | @vindex TYPE_CODE_STRUCT |
329baa95 DE |
1093 | @item gdb.TYPE_CODE_STRUCT |
1094 | The type is a structure. | |
1095 | ||
b3ce5e5f | 1096 | @vindex TYPE_CODE_UNION |
329baa95 DE |
1097 | @item gdb.TYPE_CODE_UNION |
1098 | The type is a union. | |
1099 | ||
b3ce5e5f | 1100 | @vindex TYPE_CODE_ENUM |
329baa95 DE |
1101 | @item gdb.TYPE_CODE_ENUM |
1102 | The type is an enum. | |
1103 | ||
b3ce5e5f | 1104 | @vindex TYPE_CODE_FLAGS |
329baa95 DE |
1105 | @item gdb.TYPE_CODE_FLAGS |
1106 | A bit flags type, used for things such as status registers. | |
1107 | ||
b3ce5e5f | 1108 | @vindex TYPE_CODE_FUNC |
329baa95 DE |
1109 | @item gdb.TYPE_CODE_FUNC |
1110 | The type is a function. | |
1111 | ||
b3ce5e5f | 1112 | @vindex TYPE_CODE_INT |
329baa95 DE |
1113 | @item gdb.TYPE_CODE_INT |
1114 | The type is an integer type. | |
1115 | ||
b3ce5e5f | 1116 | @vindex TYPE_CODE_FLT |
329baa95 DE |
1117 | @item gdb.TYPE_CODE_FLT |
1118 | A floating point type. | |
1119 | ||
b3ce5e5f | 1120 | @vindex TYPE_CODE_VOID |
329baa95 DE |
1121 | @item gdb.TYPE_CODE_VOID |
1122 | The special type @code{void}. | |
1123 | ||
b3ce5e5f | 1124 | @vindex TYPE_CODE_SET |
329baa95 DE |
1125 | @item gdb.TYPE_CODE_SET |
1126 | A Pascal set type. | |
1127 | ||
b3ce5e5f | 1128 | @vindex TYPE_CODE_RANGE |
329baa95 DE |
1129 | @item gdb.TYPE_CODE_RANGE |
1130 | A range type, that is, an integer type with bounds. | |
1131 | ||
b3ce5e5f | 1132 | @vindex TYPE_CODE_STRING |
329baa95 DE |
1133 | @item gdb.TYPE_CODE_STRING |
1134 | A string type. Note that this is only used for certain languages with | |
1135 | language-defined string types; C strings are not represented this way. | |
1136 | ||
b3ce5e5f | 1137 | @vindex TYPE_CODE_BITSTRING |
329baa95 DE |
1138 | @item gdb.TYPE_CODE_BITSTRING |
1139 | A string of bits. It is deprecated. | |
1140 | ||
b3ce5e5f | 1141 | @vindex TYPE_CODE_ERROR |
329baa95 DE |
1142 | @item gdb.TYPE_CODE_ERROR |
1143 | An unknown or erroneous type. | |
1144 | ||
b3ce5e5f | 1145 | @vindex TYPE_CODE_METHOD |
329baa95 DE |
1146 | @item gdb.TYPE_CODE_METHOD |
1147 | A method type, as found in C@t{++} or Java. | |
1148 | ||
b3ce5e5f | 1149 | @vindex TYPE_CODE_METHODPTR |
329baa95 DE |
1150 | @item gdb.TYPE_CODE_METHODPTR |
1151 | A pointer-to-member-function. | |
1152 | ||
b3ce5e5f | 1153 | @vindex TYPE_CODE_MEMBERPTR |
329baa95 DE |
1154 | @item gdb.TYPE_CODE_MEMBERPTR |
1155 | A pointer-to-member. | |
1156 | ||
b3ce5e5f | 1157 | @vindex TYPE_CODE_REF |
329baa95 DE |
1158 | @item gdb.TYPE_CODE_REF |
1159 | A reference type. | |
1160 | ||
b3ce5e5f | 1161 | @vindex TYPE_CODE_CHAR |
329baa95 DE |
1162 | @item gdb.TYPE_CODE_CHAR |
1163 | A character type. | |
1164 | ||
b3ce5e5f | 1165 | @vindex TYPE_CODE_BOOL |
329baa95 DE |
1166 | @item gdb.TYPE_CODE_BOOL |
1167 | A boolean type. | |
1168 | ||
b3ce5e5f | 1169 | @vindex TYPE_CODE_COMPLEX |
329baa95 DE |
1170 | @item gdb.TYPE_CODE_COMPLEX |
1171 | A complex float type. | |
1172 | ||
b3ce5e5f | 1173 | @vindex TYPE_CODE_TYPEDEF |
329baa95 DE |
1174 | @item gdb.TYPE_CODE_TYPEDEF |
1175 | A typedef to some other type. | |
1176 | ||
b3ce5e5f | 1177 | @vindex TYPE_CODE_NAMESPACE |
329baa95 DE |
1178 | @item gdb.TYPE_CODE_NAMESPACE |
1179 | A C@t{++} namespace. | |
1180 | ||
b3ce5e5f | 1181 | @vindex TYPE_CODE_DECFLOAT |
329baa95 DE |
1182 | @item gdb.TYPE_CODE_DECFLOAT |
1183 | A decimal floating point type. | |
1184 | ||
b3ce5e5f | 1185 | @vindex TYPE_CODE_INTERNAL_FUNCTION |
329baa95 DE |
1186 | @item gdb.TYPE_CODE_INTERNAL_FUNCTION |
1187 | A function internal to @value{GDBN}. This is the type used to represent | |
1188 | convenience functions. | |
b3ce5e5f | 1189 | @end vtable |
329baa95 DE |
1190 | |
1191 | Further support for types is provided in the @code{gdb.types} | |
1192 | Python module (@pxref{gdb.types}). | |
1193 | ||
1194 | @node Pretty Printing API | |
1195 | @subsubsection Pretty Printing API | |
b3ce5e5f | 1196 | @cindex python pretty printing api |
329baa95 DE |
1197 | |
1198 | An example output is provided (@pxref{Pretty Printing}). | |
1199 | ||
1200 | A pretty-printer is just an object that holds a value and implements a | |
1201 | specific interface, defined here. | |
1202 | ||
1203 | @defun pretty_printer.children (self) | |
1204 | @value{GDBN} will call this method on a pretty-printer to compute the | |
1205 | children of the pretty-printer's value. | |
1206 | ||
1207 | This method must return an object conforming to the Python iterator | |
1208 | protocol. Each item returned by the iterator must be a tuple holding | |
1209 | two elements. The first element is the ``name'' of the child; the | |
1210 | second element is the child's value. The value can be any Python | |
1211 | object which is convertible to a @value{GDBN} value. | |
1212 | ||
1213 | This method is optional. If it does not exist, @value{GDBN} will act | |
1214 | as though the value has no children. | |
1215 | @end defun | |
1216 | ||
1217 | @defun pretty_printer.display_hint (self) | |
1218 | The CLI may call this method and use its result to change the | |
1219 | formatting of a value. The result will also be supplied to an MI | |
1220 | consumer as a @samp{displayhint} attribute of the variable being | |
1221 | printed. | |
1222 | ||
1223 | This method is optional. If it does exist, this method must return a | |
1224 | string. | |
1225 | ||
1226 | Some display hints are predefined by @value{GDBN}: | |
1227 | ||
1228 | @table @samp | |
1229 | @item array | |
1230 | Indicate that the object being printed is ``array-like''. The CLI | |
1231 | uses this to respect parameters such as @code{set print elements} and | |
1232 | @code{set print array}. | |
1233 | ||
1234 | @item map | |
1235 | Indicate that the object being printed is ``map-like'', and that the | |
1236 | children of this value can be assumed to alternate between keys and | |
1237 | values. | |
1238 | ||
1239 | @item string | |
1240 | Indicate that the object being printed is ``string-like''. If the | |
1241 | printer's @code{to_string} method returns a Python string of some | |
1242 | kind, then @value{GDBN} will call its internal language-specific | |
1243 | string-printing function to format the string. For the CLI this means | |
1244 | adding quotation marks, possibly escaping some characters, respecting | |
1245 | @code{set print elements}, and the like. | |
1246 | @end table | |
1247 | @end defun | |
1248 | ||
1249 | @defun pretty_printer.to_string (self) | |
1250 | @value{GDBN} will call this method to display the string | |
1251 | representation of the value passed to the object's constructor. | |
1252 | ||
1253 | When printing from the CLI, if the @code{to_string} method exists, | |
1254 | then @value{GDBN} will prepend its result to the values returned by | |
1255 | @code{children}. Exactly how this formatting is done is dependent on | |
1256 | the display hint, and may change as more hints are added. Also, | |
1257 | depending on the print settings (@pxref{Print Settings}), the CLI may | |
1258 | print just the result of @code{to_string} in a stack trace, omitting | |
1259 | the result of @code{children}. | |
1260 | ||
1261 | If this method returns a string, it is printed verbatim. | |
1262 | ||
1263 | Otherwise, if this method returns an instance of @code{gdb.Value}, | |
1264 | then @value{GDBN} prints this value. This may result in a call to | |
1265 | another pretty-printer. | |
1266 | ||
1267 | If instead the method returns a Python value which is convertible to a | |
1268 | @code{gdb.Value}, then @value{GDBN} performs the conversion and prints | |
1269 | the resulting value. Again, this may result in a call to another | |
1270 | pretty-printer. Python scalars (integers, floats, and booleans) and | |
1271 | strings are convertible to @code{gdb.Value}; other types are not. | |
1272 | ||
1273 | Finally, if this method returns @code{None} then no further operations | |
1274 | are peformed in this method and nothing is printed. | |
1275 | ||
1276 | If the result is not one of these types, an exception is raised. | |
1277 | @end defun | |
1278 | ||
1279 | @value{GDBN} provides a function which can be used to look up the | |
1280 | default pretty-printer for a @code{gdb.Value}: | |
1281 | ||
1282 | @findex gdb.default_visualizer | |
1283 | @defun gdb.default_visualizer (value) | |
1284 | This function takes a @code{gdb.Value} object as an argument. If a | |
1285 | pretty-printer for this value exists, then it is returned. If no such | |
1286 | printer exists, then this returns @code{None}. | |
1287 | @end defun | |
1288 | ||
1289 | @node Selecting Pretty-Printers | |
1290 | @subsubsection Selecting Pretty-Printers | |
b3ce5e5f | 1291 | @cindex selecting python pretty-printers |
329baa95 DE |
1292 | |
1293 | The Python list @code{gdb.pretty_printers} contains an array of | |
1294 | functions or callable objects that have been registered via addition | |
1295 | as a pretty-printer. Printers in this list are called @code{global} | |
1296 | printers, they're available when debugging all inferiors. | |
1297 | Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute. | |
1298 | Each @code{gdb.Objfile} also contains a @code{pretty_printers} | |
1299 | attribute. | |
1300 | ||
1301 | Each function on these lists is passed a single @code{gdb.Value} | |
1302 | argument and should return a pretty-printer object conforming to the | |
1303 | interface definition above (@pxref{Pretty Printing API}). If a function | |
1304 | cannot create a pretty-printer for the value, it should return | |
1305 | @code{None}. | |
1306 | ||
1307 | @value{GDBN} first checks the @code{pretty_printers} attribute of each | |
1308 | @code{gdb.Objfile} in the current program space and iteratively calls | |
1309 | each enabled lookup routine in the list for that @code{gdb.Objfile} | |
1310 | until it receives a pretty-printer object. | |
1311 | If no pretty-printer is found in the objfile lists, @value{GDBN} then | |
1312 | searches the pretty-printer list of the current program space, | |
1313 | calling each enabled function until an object is returned. | |
1314 | After these lists have been exhausted, it tries the global | |
1315 | @code{gdb.pretty_printers} list, again calling each enabled function until an | |
1316 | object is returned. | |
1317 | ||
1318 | The order in which the objfiles are searched is not specified. For a | |
1319 | given list, functions are always invoked from the head of the list, | |
1320 | and iterated over sequentially until the end of the list, or a printer | |
1321 | object is returned. | |
1322 | ||
1323 | For various reasons a pretty-printer may not work. | |
1324 | For example, the underlying data structure may have changed and | |
1325 | the pretty-printer is out of date. | |
1326 | ||
1327 | The consequences of a broken pretty-printer are severe enough that | |
1328 | @value{GDBN} provides support for enabling and disabling individual | |
1329 | printers. For example, if @code{print frame-arguments} is on, | |
1330 | a backtrace can become highly illegible if any argument is printed | |
1331 | with a broken printer. | |
1332 | ||
1333 | Pretty-printers are enabled and disabled by attaching an @code{enabled} | |
1334 | attribute to the registered function or callable object. If this attribute | |
1335 | is present and its value is @code{False}, the printer is disabled, otherwise | |
1336 | the printer is enabled. | |
1337 | ||
1338 | @node Writing a Pretty-Printer | |
1339 | @subsubsection Writing a Pretty-Printer | |
1340 | @cindex writing a pretty-printer | |
1341 | ||
1342 | A pretty-printer consists of two parts: a lookup function to detect | |
1343 | if the type is supported, and the printer itself. | |
1344 | ||
1345 | Here is an example showing how a @code{std::string} printer might be | |
1346 | written. @xref{Pretty Printing API}, for details on the API this class | |
1347 | must provide. | |
1348 | ||
1349 | @smallexample | |
1350 | class StdStringPrinter(object): | |
1351 | "Print a std::string" | |
1352 | ||
1353 | def __init__(self, val): | |
1354 | self.val = val | |
1355 | ||
1356 | def to_string(self): | |
1357 | return self.val['_M_dataplus']['_M_p'] | |
1358 | ||
1359 | def display_hint(self): | |
1360 | return 'string' | |
1361 | @end smallexample | |
1362 | ||
1363 | And here is an example showing how a lookup function for the printer | |
1364 | example above might be written. | |
1365 | ||
1366 | @smallexample | |
1367 | def str_lookup_function(val): | |
1368 | lookup_tag = val.type.tag | |
1369 | if lookup_tag == None: | |
1370 | return None | |
1371 | regex = re.compile("^std::basic_string<char,.*>$") | |
1372 | if regex.match(lookup_tag): | |
1373 | return StdStringPrinter(val) | |
1374 | return None | |
1375 | @end smallexample | |
1376 | ||
1377 | The example lookup function extracts the value's type, and attempts to | |
1378 | match it to a type that it can pretty-print. If it is a type the | |
1379 | printer can pretty-print, it will return a printer object. If not, it | |
1380 | returns @code{None}. | |
1381 | ||
1382 | We recommend that you put your core pretty-printers into a Python | |
1383 | package. If your pretty-printers are for use with a library, we | |
1384 | further recommend embedding a version number into the package name. | |
1385 | This practice will enable @value{GDBN} to load multiple versions of | |
1386 | your pretty-printers at the same time, because they will have | |
1387 | different names. | |
1388 | ||
1389 | You should write auto-loaded code (@pxref{Python Auto-loading}) such that it | |
1390 | can be evaluated multiple times without changing its meaning. An | |
1391 | ideal auto-load file will consist solely of @code{import}s of your | |
1392 | printer modules, followed by a call to a register pretty-printers with | |
1393 | the current objfile. | |
1394 | ||
1395 | Taken as a whole, this approach will scale nicely to multiple | |
1396 | inferiors, each potentially using a different library version. | |
1397 | Embedding a version number in the Python package name will ensure that | |
1398 | @value{GDBN} is able to load both sets of printers simultaneously. | |
1399 | Then, because the search for pretty-printers is done by objfile, and | |
1400 | because your auto-loaded code took care to register your library's | |
1401 | printers with a specific objfile, @value{GDBN} will find the correct | |
1402 | printers for the specific version of the library used by each | |
1403 | inferior. | |
1404 | ||
1405 | To continue the @code{std::string} example (@pxref{Pretty Printing API}), | |
1406 | this code might appear in @code{gdb.libstdcxx.v6}: | |
1407 | ||
1408 | @smallexample | |
1409 | def register_printers(objfile): | |
1410 | objfile.pretty_printers.append(str_lookup_function) | |
1411 | @end smallexample | |
1412 | ||
1413 | @noindent | |
1414 | And then the corresponding contents of the auto-load file would be: | |
1415 | ||
1416 | @smallexample | |
1417 | import gdb.libstdcxx.v6 | |
1418 | gdb.libstdcxx.v6.register_printers(gdb.current_objfile()) | |
1419 | @end smallexample | |
1420 | ||
1421 | The previous example illustrates a basic pretty-printer. | |
1422 | There are a few things that can be improved on. | |
1423 | The printer doesn't have a name, making it hard to identify in a | |
1424 | list of installed printers. The lookup function has a name, but | |
1425 | lookup functions can have arbitrary, even identical, names. | |
1426 | ||
1427 | Second, the printer only handles one type, whereas a library typically has | |
1428 | several types. One could install a lookup function for each desired type | |
1429 | in the library, but one could also have a single lookup function recognize | |
1430 | several types. The latter is the conventional way this is handled. | |
1431 | If a pretty-printer can handle multiple data types, then its | |
1432 | @dfn{subprinters} are the printers for the individual data types. | |
1433 | ||
1434 | The @code{gdb.printing} module provides a formal way of solving these | |
1435 | problems (@pxref{gdb.printing}). | |
1436 | Here is another example that handles multiple types. | |
1437 | ||
1438 | These are the types we are going to pretty-print: | |
1439 | ||
1440 | @smallexample | |
1441 | struct foo @{ int a, b; @}; | |
1442 | struct bar @{ struct foo x, y; @}; | |
1443 | @end smallexample | |
1444 | ||
1445 | Here are the printers: | |
1446 | ||
1447 | @smallexample | |
1448 | class fooPrinter: | |
1449 | """Print a foo object.""" | |
1450 | ||
1451 | def __init__(self, val): | |
1452 | self.val = val | |
1453 | ||
1454 | def to_string(self): | |
1455 | return ("a=<" + str(self.val["a"]) + | |
1456 | "> b=<" + str(self.val["b"]) + ">") | |
1457 | ||
1458 | class barPrinter: | |
1459 | """Print a bar object.""" | |
1460 | ||
1461 | def __init__(self, val): | |
1462 | self.val = val | |
1463 | ||
1464 | def to_string(self): | |
1465 | return ("x=<" + str(self.val["x"]) + | |
1466 | "> y=<" + str(self.val["y"]) + ">") | |
1467 | @end smallexample | |
1468 | ||
1469 | This example doesn't need a lookup function, that is handled by the | |
1470 | @code{gdb.printing} module. Instead a function is provided to build up | |
1471 | the object that handles the lookup. | |
1472 | ||
1473 | @smallexample | |
1474 | import gdb.printing | |
1475 | ||
1476 | def build_pretty_printer(): | |
1477 | pp = gdb.printing.RegexpCollectionPrettyPrinter( | |
1478 | "my_library") | |
1479 | pp.add_printer('foo', '^foo$', fooPrinter) | |
1480 | pp.add_printer('bar', '^bar$', barPrinter) | |
1481 | return pp | |
1482 | @end smallexample | |
1483 | ||
1484 | And here is the autoload support: | |
1485 | ||
1486 | @smallexample | |
1487 | import gdb.printing | |
1488 | import my_library | |
1489 | gdb.printing.register_pretty_printer( | |
1490 | gdb.current_objfile(), | |
1491 | my_library.build_pretty_printer()) | |
1492 | @end smallexample | |
1493 | ||
1494 | Finally, when this printer is loaded into @value{GDBN}, here is the | |
1495 | corresponding output of @samp{info pretty-printer}: | |
1496 | ||
1497 | @smallexample | |
1498 | (gdb) info pretty-printer | |
1499 | my_library.so: | |
1500 | my_library | |
1501 | foo | |
1502 | bar | |
1503 | @end smallexample | |
1504 | ||
1505 | @node Type Printing API | |
1506 | @subsubsection Type Printing API | |
1507 | @cindex type printing API for Python | |
1508 | ||
1509 | @value{GDBN} provides a way for Python code to customize type display. | |
1510 | This is mainly useful for substituting canonical typedef names for | |
1511 | types. | |
1512 | ||
1513 | @cindex type printer | |
1514 | A @dfn{type printer} is just a Python object conforming to a certain | |
1515 | protocol. A simple base class implementing the protocol is provided; | |
1516 | see @ref{gdb.types}. A type printer must supply at least: | |
1517 | ||
1518 | @defivar type_printer enabled | |
1519 | A boolean which is True if the printer is enabled, and False | |
1520 | otherwise. This is manipulated by the @code{enable type-printer} | |
1521 | and @code{disable type-printer} commands. | |
1522 | @end defivar | |
1523 | ||
1524 | @defivar type_printer name | |
1525 | The name of the type printer. This must be a string. This is used by | |
1526 | the @code{enable type-printer} and @code{disable type-printer} | |
1527 | commands. | |
1528 | @end defivar | |
1529 | ||
1530 | @defmethod type_printer instantiate (self) | |
1531 | This is called by @value{GDBN} at the start of type-printing. It is | |
1532 | only called if the type printer is enabled. This method must return a | |
1533 | new object that supplies a @code{recognize} method, as described below. | |
1534 | @end defmethod | |
1535 | ||
1536 | ||
1537 | When displaying a type, say via the @code{ptype} command, @value{GDBN} | |
1538 | will compute a list of type recognizers. This is done by iterating | |
1539 | first over the per-objfile type printers (@pxref{Objfiles In Python}), | |
1540 | followed by the per-progspace type printers (@pxref{Progspaces In | |
1541 | Python}), and finally the global type printers. | |
1542 | ||
1543 | @value{GDBN} will call the @code{instantiate} method of each enabled | |
1544 | type printer. If this method returns @code{None}, then the result is | |
1545 | ignored; otherwise, it is appended to the list of recognizers. | |
1546 | ||
1547 | Then, when @value{GDBN} is going to display a type name, it iterates | |
1548 | over the list of recognizers. For each one, it calls the recognition | |
1549 | function, stopping if the function returns a non-@code{None} value. | |
1550 | The recognition function is defined as: | |
1551 | ||
1552 | @defmethod type_recognizer recognize (self, type) | |
1553 | If @var{type} is not recognized, return @code{None}. Otherwise, | |
1554 | return a string which is to be printed as the name of @var{type}. | |
697aa1b7 EZ |
1555 | The @var{type} argument will be an instance of @code{gdb.Type} |
1556 | (@pxref{Types In Python}). | |
329baa95 DE |
1557 | @end defmethod |
1558 | ||
1559 | @value{GDBN} uses this two-pass approach so that type printers can | |
1560 | efficiently cache information without holding on to it too long. For | |
1561 | example, it can be convenient to look up type information in a type | |
1562 | printer and hold it for a recognizer's lifetime; if a single pass were | |
1563 | done then type printers would have to make use of the event system in | |
1564 | order to avoid holding information that could become stale as the | |
1565 | inferior changed. | |
1566 | ||
1567 | @node Frame Filter API | |
1568 | @subsubsection Filtering Frames. | |
1569 | @cindex frame filters api | |
1570 | ||
1571 | Frame filters are Python objects that manipulate the visibility of a | |
1572 | frame or frames when a backtrace (@pxref{Backtrace}) is printed by | |
1573 | @value{GDBN}. | |
1574 | ||
1575 | Only commands that print a backtrace, or, in the case of @sc{gdb/mi} | |
1576 | commands (@pxref{GDB/MI}), those that return a collection of frames | |
1577 | are affected. The commands that work with frame filters are: | |
1578 | ||
1579 | @code{backtrace} (@pxref{backtrace-command,, The backtrace command}), | |
1580 | @code{-stack-list-frames} | |
1581 | (@pxref{-stack-list-frames,, The -stack-list-frames command}), | |
1582 | @code{-stack-list-variables} (@pxref{-stack-list-variables,, The | |
1583 | -stack-list-variables command}), @code{-stack-list-arguments} | |
1584 | @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and | |
1585 | @code{-stack-list-locals} (@pxref{-stack-list-locals,, The | |
1586 | -stack-list-locals command}). | |
1587 | ||
1588 | A frame filter works by taking an iterator as an argument, applying | |
1589 | actions to the contents of that iterator, and returning another | |
1590 | iterator (or, possibly, the same iterator it was provided in the case | |
1591 | where the filter does not perform any operations). Typically, frame | |
1592 | filters utilize tools such as the Python's @code{itertools} module to | |
1593 | work with and create new iterators from the source iterator. | |
1594 | Regardless of how a filter chooses to apply actions, it must not alter | |
1595 | the underlying @value{GDBN} frame or frames, or attempt to alter the | |
1596 | call-stack within @value{GDBN}. This preserves data integrity within | |
1597 | @value{GDBN}. Frame filters are executed on a priority basis and care | |
1598 | should be taken that some frame filters may have been executed before, | |
1599 | and that some frame filters will be executed after. | |
1600 | ||
1601 | An important consideration when designing frame filters, and well | |
1602 | worth reflecting upon, is that frame filters should avoid unwinding | |
1603 | the call stack if possible. Some stacks can run very deep, into the | |
1604 | tens of thousands in some cases. To search every frame when a frame | |
1605 | filter executes may be too expensive at that step. The frame filter | |
1606 | cannot know how many frames it has to iterate over, and it may have to | |
1607 | iterate through them all. This ends up duplicating effort as | |
1608 | @value{GDBN} performs this iteration when it prints the frames. If | |
1609 | the filter can defer unwinding frames until frame decorators are | |
1610 | executed, after the last filter has executed, it should. @xref{Frame | |
1611 | Decorator API}, for more information on decorators. Also, there are | |
1612 | examples for both frame decorators and filters in later chapters. | |
1613 | @xref{Writing a Frame Filter}, for more information. | |
1614 | ||
1615 | The Python dictionary @code{gdb.frame_filters} contains key/object | |
1616 | pairings that comprise a frame filter. Frame filters in this | |
1617 | dictionary are called @code{global} frame filters, and they are | |
1618 | available when debugging all inferiors. These frame filters must | |
1619 | register with the dictionary directly. In addition to the | |
1620 | @code{global} dictionary, there are other dictionaries that are loaded | |
1621 | with different inferiors via auto-loading (@pxref{Python | |
1622 | Auto-loading}). The two other areas where frame filter dictionaries | |
1623 | can be found are: @code{gdb.Progspace} which contains a | |
1624 | @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile} | |
1625 | object which also contains a @code{frame_filters} dictionary | |
1626 | attribute. | |
1627 | ||
1628 | When a command is executed from @value{GDBN} that is compatible with | |
1629 | frame filters, @value{GDBN} combines the @code{global}, | |
1630 | @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently | |
1631 | loaded. All of the @code{gdb.Objfile} dictionaries are combined, as | |
1632 | several frames, and thus several object files, might be in use. | |
1633 | @value{GDBN} then prunes any frame filter whose @code{enabled} | |
1634 | attribute is @code{False}. This pruned list is then sorted according | |
1635 | to the @code{priority} attribute in each filter. | |
1636 | ||
1637 | Once the dictionaries are combined, pruned and sorted, @value{GDBN} | |
1638 | creates an iterator which wraps each frame in the call stack in a | |
1639 | @code{FrameDecorator} object, and calls each filter in order. The | |
1640 | output from the previous filter will always be the input to the next | |
1641 | filter, and so on. | |
1642 | ||
1643 | Frame filters have a mandatory interface which each frame filter must | |
1644 | implement, defined here: | |
1645 | ||
1646 | @defun FrameFilter.filter (iterator) | |
1647 | @value{GDBN} will call this method on a frame filter when it has | |
1648 | reached the order in the priority list for that filter. | |
1649 | ||
1650 | For example, if there are four frame filters: | |
1651 | ||
1652 | @smallexample | |
1653 | Name Priority | |
1654 | ||
1655 | Filter1 5 | |
1656 | Filter2 10 | |
1657 | Filter3 100 | |
1658 | Filter4 1 | |
1659 | @end smallexample | |
1660 | ||
1661 | The order that the frame filters will be called is: | |
1662 | ||
1663 | @smallexample | |
1664 | Filter3 -> Filter2 -> Filter1 -> Filter4 | |
1665 | @end smallexample | |
1666 | ||
1667 | Note that the output from @code{Filter3} is passed to the input of | |
1668 | @code{Filter2}, and so on. | |
1669 | ||
1670 | This @code{filter} method is passed a Python iterator. This iterator | |
1671 | contains a sequence of frame decorators that wrap each | |
1672 | @code{gdb.Frame}, or a frame decorator that wraps another frame | |
1673 | decorator. The first filter that is executed in the sequence of frame | |
1674 | filters will receive an iterator entirely comprised of default | |
1675 | @code{FrameDecorator} objects. However, after each frame filter is | |
1676 | executed, the previous frame filter may have wrapped some or all of | |
1677 | the frame decorators with their own frame decorator. As frame | |
1678 | decorators must also conform to a mandatory interface, these | |
1679 | decorators can be assumed to act in a uniform manner (@pxref{Frame | |
1680 | Decorator API}). | |
1681 | ||
1682 | This method must return an object conforming to the Python iterator | |
1683 | protocol. Each item in the iterator must be an object conforming to | |
1684 | the frame decorator interface. If a frame filter does not wish to | |
1685 | perform any operations on this iterator, it should return that | |
1686 | iterator untouched. | |
1687 | ||
1688 | This method is not optional. If it does not exist, @value{GDBN} will | |
1689 | raise and print an error. | |
1690 | @end defun | |
1691 | ||
1692 | @defvar FrameFilter.name | |
1693 | The @code{name} attribute must be Python string which contains the | |
1694 | name of the filter displayed by @value{GDBN} (@pxref{Frame Filter | |
1695 | Management}). This attribute may contain any combination of letters | |
1696 | or numbers. Care should be taken to ensure that it is unique. This | |
1697 | attribute is mandatory. | |
1698 | @end defvar | |
1699 | ||
1700 | @defvar FrameFilter.enabled | |
1701 | The @code{enabled} attribute must be Python boolean. This attribute | |
1702 | indicates to @value{GDBN} whether the frame filter is enabled, and | |
1703 | should be considered when frame filters are executed. If | |
1704 | @code{enabled} is @code{True}, then the frame filter will be executed | |
1705 | when any of the backtrace commands detailed earlier in this chapter | |
1706 | are executed. If @code{enabled} is @code{False}, then the frame | |
1707 | filter will not be executed. This attribute is mandatory. | |
1708 | @end defvar | |
1709 | ||
1710 | @defvar FrameFilter.priority | |
1711 | The @code{priority} attribute must be Python integer. This attribute | |
1712 | controls the order of execution in relation to other frame filters. | |
1713 | There are no imposed limits on the range of @code{priority} other than | |
1714 | it must be a valid integer. The higher the @code{priority} attribute, | |
1715 | the sooner the frame filter will be executed in relation to other | |
1716 | frame filters. Although @code{priority} can be negative, it is | |
1717 | recommended practice to assume zero is the lowest priority that a | |
1718 | frame filter can be assigned. Frame filters that have the same | |
1719 | priority are executed in unsorted order in that priority slot. This | |
1720 | attribute is mandatory. | |
1721 | @end defvar | |
1722 | ||
1723 | @node Frame Decorator API | |
1724 | @subsubsection Decorating Frames. | |
1725 | @cindex frame decorator api | |
1726 | ||
1727 | Frame decorators are sister objects to frame filters (@pxref{Frame | |
1728 | Filter API}). Frame decorators are applied by a frame filter and can | |
1729 | only be used in conjunction with frame filters. | |
1730 | ||
1731 | The purpose of a frame decorator is to customize the printed content | |
1732 | of each @code{gdb.Frame} in commands where frame filters are executed. | |
1733 | This concept is called decorating a frame. Frame decorators decorate | |
1734 | a @code{gdb.Frame} with Python code contained within each API call. | |
1735 | This separates the actual data contained in a @code{gdb.Frame} from | |
1736 | the decorated data produced by a frame decorator. This abstraction is | |
1737 | necessary to maintain integrity of the data contained in each | |
1738 | @code{gdb.Frame}. | |
1739 | ||
1740 | Frame decorators have a mandatory interface, defined below. | |
1741 | ||
1742 | @value{GDBN} already contains a frame decorator called | |
1743 | @code{FrameDecorator}. This contains substantial amounts of | |
1744 | boilerplate code to decorate the content of a @code{gdb.Frame}. It is | |
1745 | recommended that other frame decorators inherit and extend this | |
1746 | object, and only to override the methods needed. | |
1747 | ||
1748 | @defun FrameDecorator.elided (self) | |
1749 | ||
1750 | The @code{elided} method groups frames together in a hierarchical | |
1751 | system. An example would be an interpreter, where multiple low-level | |
1752 | frames make up a single call in the interpreted language. In this | |
1753 | example, the frame filter would elide the low-level frames and present | |
1754 | a single high-level frame, representing the call in the interpreted | |
1755 | language, to the user. | |
1756 | ||
1757 | The @code{elided} function must return an iterable and this iterable | |
1758 | must contain the frames that are being elided wrapped in a suitable | |
1759 | frame decorator. If no frames are being elided this function may | |
1760 | return an empty iterable, or @code{None}. Elided frames are indented | |
1761 | from normal frames in a @code{CLI} backtrace, or in the case of | |
1762 | @code{GDB/MI}, are placed in the @code{children} field of the eliding | |
1763 | frame. | |
1764 | ||
1765 | It is the frame filter's task to also filter out the elided frames from | |
1766 | the source iterator. This will avoid printing the frame twice. | |
1767 | @end defun | |
1768 | ||
1769 | @defun FrameDecorator.function (self) | |
1770 | ||
1771 | This method returns the name of the function in the frame that is to | |
1772 | be printed. | |
1773 | ||
1774 | This method must return a Python string describing the function, or | |
1775 | @code{None}. | |
1776 | ||
1777 | If this function returns @code{None}, @value{GDBN} will not print any | |
1778 | data for this field. | |
1779 | @end defun | |
1780 | ||
1781 | @defun FrameDecorator.address (self) | |
1782 | ||
1783 | This method returns the address of the frame that is to be printed. | |
1784 | ||
1785 | This method must return a Python numeric integer type of sufficient | |
1786 | size to describe the address of the frame, or @code{None}. | |
1787 | ||
1788 | If this function returns a @code{None}, @value{GDBN} will not print | |
1789 | any data for this field. | |
1790 | @end defun | |
1791 | ||
1792 | @defun FrameDecorator.filename (self) | |
1793 | ||
1794 | This method returns the filename and path associated with this frame. | |
1795 | ||
1796 | This method must return a Python string containing the filename and | |
1797 | the path to the object file backing the frame, or @code{None}. | |
1798 | ||
1799 | If this function returns a @code{None}, @value{GDBN} will not print | |
1800 | any data for this field. | |
1801 | @end defun | |
1802 | ||
1803 | @defun FrameDecorator.line (self): | |
1804 | ||
1805 | This method returns the line number associated with the current | |
1806 | position within the function addressed by this frame. | |
1807 | ||
1808 | This method must return a Python integer type, or @code{None}. | |
1809 | ||
1810 | If this function returns a @code{None}, @value{GDBN} will not print | |
1811 | any data for this field. | |
1812 | @end defun | |
1813 | ||
1814 | @defun FrameDecorator.frame_args (self) | |
1815 | @anchor{frame_args} | |
1816 | ||
1817 | This method must return an iterable, or @code{None}. Returning an | |
1818 | empty iterable, or @code{None} means frame arguments will not be | |
1819 | printed for this frame. This iterable must contain objects that | |
1820 | implement two methods, described here. | |
1821 | ||
1822 | This object must implement a @code{argument} method which takes a | |
1823 | single @code{self} parameter and must return a @code{gdb.Symbol} | |
1824 | (@pxref{Symbols In Python}), or a Python string. The object must also | |
1825 | implement a @code{value} method which takes a single @code{self} | |
1826 | parameter and must return a @code{gdb.Value} (@pxref{Values From | |
1827 | Inferior}), a Python value, or @code{None}. If the @code{value} | |
1828 | method returns @code{None}, and the @code{argument} method returns a | |
1829 | @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of | |
1830 | the @code{gdb.Symbol} automatically. | |
1831 | ||
1832 | A brief example: | |
1833 | ||
1834 | @smallexample | |
1835 | class SymValueWrapper(): | |
1836 | ||
1837 | def __init__(self, symbol, value): | |
1838 | self.sym = symbol | |
1839 | self.val = value | |
1840 | ||
1841 | def value(self): | |
1842 | return self.val | |
1843 | ||
1844 | def symbol(self): | |
1845 | return self.sym | |
1846 | ||
1847 | class SomeFrameDecorator() | |
1848 | ... | |
1849 | ... | |
1850 | def frame_args(self): | |
1851 | args = [] | |
1852 | try: | |
1853 | block = self.inferior_frame.block() | |
1854 | except: | |
1855 | return None | |
1856 | ||
1857 | # Iterate over all symbols in a block. Only add | |
1858 | # symbols that are arguments. | |
1859 | for sym in block: | |
1860 | if not sym.is_argument: | |
1861 | continue | |
1862 | args.append(SymValueWrapper(sym,None)) | |
1863 | ||
1864 | # Add example synthetic argument. | |
1865 | args.append(SymValueWrapper(``foo'', 42)) | |
1866 | ||
1867 | return args | |
1868 | @end smallexample | |
1869 | @end defun | |
1870 | ||
1871 | @defun FrameDecorator.frame_locals (self) | |
1872 | ||
1873 | This method must return an iterable or @code{None}. Returning an | |
1874 | empty iterable, or @code{None} means frame local arguments will not be | |
1875 | printed for this frame. | |
1876 | ||
1877 | The object interface, the description of the various strategies for | |
1878 | reading frame locals, and the example are largely similar to those | |
1879 | described in the @code{frame_args} function, (@pxref{frame_args,,The | |
1880 | frame filter frame_args function}). Below is a modified example: | |
1881 | ||
1882 | @smallexample | |
1883 | class SomeFrameDecorator() | |
1884 | ... | |
1885 | ... | |
1886 | def frame_locals(self): | |
1887 | vars = [] | |
1888 | try: | |
1889 | block = self.inferior_frame.block() | |
1890 | except: | |
1891 | return None | |
1892 | ||
1893 | # Iterate over all symbols in a block. Add all | |
1894 | # symbols, except arguments. | |
1895 | for sym in block: | |
1896 | if sym.is_argument: | |
1897 | continue | |
1898 | vars.append(SymValueWrapper(sym,None)) | |
1899 | ||
1900 | # Add an example of a synthetic local variable. | |
1901 | vars.append(SymValueWrapper(``bar'', 99)) | |
1902 | ||
1903 | return vars | |
1904 | @end smallexample | |
1905 | @end defun | |
1906 | ||
1907 | @defun FrameDecorator.inferior_frame (self): | |
1908 | ||
1909 | This method must return the underlying @code{gdb.Frame} that this | |
1910 | frame decorator is decorating. @value{GDBN} requires the underlying | |
1911 | frame for internal frame information to determine how to print certain | |
1912 | values when printing a frame. | |
1913 | @end defun | |
1914 | ||
1915 | @node Writing a Frame Filter | |
1916 | @subsubsection Writing a Frame Filter | |
1917 | @cindex writing a frame filter | |
1918 | ||
1919 | There are three basic elements that a frame filter must implement: it | |
1920 | must correctly implement the documented interface (@pxref{Frame Filter | |
1921 | API}), it must register itself with @value{GDBN}, and finally, it must | |
1922 | decide if it is to work on the data provided by @value{GDBN}. In all | |
1923 | cases, whether it works on the iterator or not, each frame filter must | |
1924 | return an iterator. A bare-bones frame filter follows the pattern in | |
1925 | the following example. | |
1926 | ||
1927 | @smallexample | |
1928 | import gdb | |
1929 | ||
1930 | class FrameFilter(): | |
1931 | ||
1932 | def __init__(self): | |
1933 | # Frame filter attribute creation. | |
1934 | # | |
1935 | # 'name' is the name of the filter that GDB will display. | |
1936 | # | |
1937 | # 'priority' is the priority of the filter relative to other | |
1938 | # filters. | |
1939 | # | |
1940 | # 'enabled' is a boolean that indicates whether this filter is | |
1941 | # enabled and should be executed. | |
1942 | ||
1943 | self.name = "Foo" | |
1944 | self.priority = 100 | |
1945 | self.enabled = True | |
1946 | ||
1947 | # Register this frame filter with the global frame_filters | |
1948 | # dictionary. | |
1949 | gdb.frame_filters[self.name] = self | |
1950 | ||
1951 | def filter(self, frame_iter): | |
1952 | # Just return the iterator. | |
1953 | return frame_iter | |
1954 | @end smallexample | |
1955 | ||
1956 | The frame filter in the example above implements the three | |
1957 | requirements for all frame filters. It implements the API, self | |
1958 | registers, and makes a decision on the iterator (in this case, it just | |
1959 | returns the iterator untouched). | |
1960 | ||
1961 | The first step is attribute creation and assignment, and as shown in | |
1962 | the comments the filter assigns the following attributes: @code{name}, | |
1963 | @code{priority} and whether the filter should be enabled with the | |
1964 | @code{enabled} attribute. | |
1965 | ||
1966 | The second step is registering the frame filter with the dictionary or | |
1967 | dictionaries that the frame filter has interest in. As shown in the | |
1968 | comments, this filter just registers itself with the global dictionary | |
1969 | @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters} | |
1970 | is a dictionary that is initialized in the @code{gdb} module when | |
1971 | @value{GDBN} starts. What dictionary a filter registers with is an | |
1972 | important consideration. Generally, if a filter is specific to a set | |
1973 | of code, it should be registered either in the @code{objfile} or | |
1974 | @code{progspace} dictionaries as they are specific to the program | |
1975 | currently loaded in @value{GDBN}. The global dictionary is always | |
1976 | present in @value{GDBN} and is never unloaded. Any filters registered | |
1977 | with the global dictionary will exist until @value{GDBN} exits. To | |
1978 | avoid filters that may conflict, it is generally better to register | |
1979 | frame filters against the dictionaries that more closely align with | |
1980 | the usage of the filter currently in question. @xref{Python | |
1981 | Auto-loading}, for further information on auto-loading Python scripts. | |
1982 | ||
1983 | @value{GDBN} takes a hands-off approach to frame filter registration, | |
1984 | therefore it is the frame filter's responsibility to ensure | |
1985 | registration has occurred, and that any exceptions are handled | |
1986 | appropriately. In particular, you may wish to handle exceptions | |
1987 | relating to Python dictionary key uniqueness. It is mandatory that | |
1988 | the dictionary key is the same as frame filter's @code{name} | |
1989 | attribute. When a user manages frame filters (@pxref{Frame Filter | |
1990 | Management}), the names @value{GDBN} will display are those contained | |
1991 | in the @code{name} attribute. | |
1992 | ||
1993 | The final step of this example is the implementation of the | |
1994 | @code{filter} method. As shown in the example comments, we define the | |
1995 | @code{filter} method and note that the method must take an iterator, | |
1996 | and also must return an iterator. In this bare-bones example, the | |
1997 | frame filter is not very useful as it just returns the iterator | |
1998 | untouched. However this is a valid operation for frame filters that | |
1999 | have the @code{enabled} attribute set, but decide not to operate on | |
2000 | any frames. | |
2001 | ||
2002 | In the next example, the frame filter operates on all frames and | |
2003 | utilizes a frame decorator to perform some work on the frames. | |
2004 | @xref{Frame Decorator API}, for further information on the frame | |
2005 | decorator interface. | |
2006 | ||
2007 | This example works on inlined frames. It highlights frames which are | |
2008 | inlined by tagging them with an ``[inlined]'' tag. By applying a | |
2009 | frame decorator to all frames with the Python @code{itertools imap} | |
2010 | method, the example defers actions to the frame decorator. Frame | |
2011 | decorators are only processed when @value{GDBN} prints the backtrace. | |
2012 | ||
2013 | This introduces a new decision making topic: whether to perform | |
2014 | decision making operations at the filtering step, or at the printing | |
2015 | step. In this example's approach, it does not perform any filtering | |
2016 | decisions at the filtering step beyond mapping a frame decorator to | |
2017 | each frame. This allows the actual decision making to be performed | |
2018 | when each frame is printed. This is an important consideration, and | |
2019 | well worth reflecting upon when designing a frame filter. An issue | |
2020 | that frame filters should avoid is unwinding the stack if possible. | |
2021 | Some stacks can run very deep, into the tens of thousands in some | |
2022 | cases. To search every frame to determine if it is inlined ahead of | |
2023 | time may be too expensive at the filtering step. The frame filter | |
2024 | cannot know how many frames it has to iterate over, and it would have | |
2025 | to iterate through them all. This ends up duplicating effort as | |
2026 | @value{GDBN} performs this iteration when it prints the frames. | |
2027 | ||
2028 | In this example decision making can be deferred to the printing step. | |
2029 | As each frame is printed, the frame decorator can examine each frame | |
2030 | in turn when @value{GDBN} iterates. From a performance viewpoint, | |
2031 | this is the most appropriate decision to make as it avoids duplicating | |
2032 | the effort that the printing step would undertake anyway. Also, if | |
2033 | there are many frame filters unwinding the stack during filtering, it | |
2034 | can substantially delay the printing of the backtrace which will | |
2035 | result in large memory usage, and a poor user experience. | |
2036 | ||
2037 | @smallexample | |
2038 | class InlineFilter(): | |
2039 | ||
2040 | def __init__(self): | |
2041 | self.name = "InlinedFrameFilter" | |
2042 | self.priority = 100 | |
2043 | self.enabled = True | |
2044 | gdb.frame_filters[self.name] = self | |
2045 | ||
2046 | def filter(self, frame_iter): | |
2047 | frame_iter = itertools.imap(InlinedFrameDecorator, | |
2048 | frame_iter) | |
2049 | return frame_iter | |
2050 | @end smallexample | |
2051 | ||
2052 | This frame filter is somewhat similar to the earlier example, except | |
2053 | that the @code{filter} method applies a frame decorator object called | |
2054 | @code{InlinedFrameDecorator} to each element in the iterator. The | |
2055 | @code{imap} Python method is light-weight. It does not proactively | |
2056 | iterate over the iterator, but rather creates a new iterator which | |
2057 | wraps the existing one. | |
2058 | ||
2059 | Below is the frame decorator for this example. | |
2060 | ||
2061 | @smallexample | |
2062 | class InlinedFrameDecorator(FrameDecorator): | |
2063 | ||
2064 | def __init__(self, fobj): | |
2065 | super(InlinedFrameDecorator, self).__init__(fobj) | |
2066 | ||
2067 | def function(self): | |
2068 | frame = fobj.inferior_frame() | |
2069 | name = str(frame.name()) | |
2070 | ||
2071 | if frame.type() == gdb.INLINE_FRAME: | |
2072 | name = name + " [inlined]" | |
2073 | ||
2074 | return name | |
2075 | @end smallexample | |
2076 | ||
2077 | This frame decorator only defines and overrides the @code{function} | |
2078 | method. It lets the supplied @code{FrameDecorator}, which is shipped | |
2079 | with @value{GDBN}, perform the other work associated with printing | |
2080 | this frame. | |
2081 | ||
2082 | The combination of these two objects create this output from a | |
2083 | backtrace: | |
2084 | ||
2085 | @smallexample | |
2086 | #0 0x004004e0 in bar () at inline.c:11 | |
2087 | #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21 | |
2088 | #2 0x00400566 in main () at inline.c:31 | |
2089 | @end smallexample | |
2090 | ||
2091 | So in the case of this example, a frame decorator is applied to all | |
2092 | frames, regardless of whether they may be inlined or not. As | |
2093 | @value{GDBN} iterates over the iterator produced by the frame filters, | |
2094 | @value{GDBN} executes each frame decorator which then makes a decision | |
2095 | on what to print in the @code{function} callback. Using a strategy | |
2096 | like this is a way to defer decisions on the frame content to printing | |
2097 | time. | |
2098 | ||
2099 | @subheading Eliding Frames | |
2100 | ||
2101 | It might be that the above example is not desirable for representing | |
2102 | inlined frames, and a hierarchical approach may be preferred. If we | |
2103 | want to hierarchically represent frames, the @code{elided} frame | |
2104 | decorator interface might be preferable. | |
2105 | ||
2106 | This example approaches the issue with the @code{elided} method. This | |
2107 | example is quite long, but very simplistic. It is out-of-scope for | |
2108 | this section to write a complete example that comprehensively covers | |
2109 | all approaches of finding and printing inlined frames. However, this | |
2110 | example illustrates the approach an author might use. | |
2111 | ||
2112 | This example comprises of three sections. | |
2113 | ||
2114 | @smallexample | |
2115 | class InlineFrameFilter(): | |
2116 | ||
2117 | def __init__(self): | |
2118 | self.name = "InlinedFrameFilter" | |
2119 | self.priority = 100 | |
2120 | self.enabled = True | |
2121 | gdb.frame_filters[self.name] = self | |
2122 | ||
2123 | def filter(self, frame_iter): | |
2124 | return ElidingInlineIterator(frame_iter) | |
2125 | @end smallexample | |
2126 | ||
2127 | This frame filter is very similar to the other examples. The only | |
2128 | difference is this frame filter is wrapping the iterator provided to | |
2129 | it (@code{frame_iter}) with a custom iterator called | |
2130 | @code{ElidingInlineIterator}. This again defers actions to when | |
2131 | @value{GDBN} prints the backtrace, as the iterator is not traversed | |
2132 | until printing. | |
2133 | ||
2134 | The iterator for this example is as follows. It is in this section of | |
2135 | the example where decisions are made on the content of the backtrace. | |
2136 | ||
2137 | @smallexample | |
2138 | class ElidingInlineIterator: | |
2139 | def __init__(self, ii): | |
2140 | self.input_iterator = ii | |
2141 | ||
2142 | def __iter__(self): | |
2143 | return self | |
2144 | ||
2145 | def next(self): | |
2146 | frame = next(self.input_iterator) | |
2147 | ||
2148 | if frame.inferior_frame().type() != gdb.INLINE_FRAME: | |
2149 | return frame | |
2150 | ||
2151 | try: | |
2152 | eliding_frame = next(self.input_iterator) | |
2153 | except StopIteration: | |
2154 | return frame | |
2155 | return ElidingFrameDecorator(eliding_frame, [frame]) | |
2156 | @end smallexample | |
2157 | ||
2158 | This iterator implements the Python iterator protocol. When the | |
2159 | @code{next} function is called (when @value{GDBN} prints each frame), | |
2160 | the iterator checks if this frame decorator, @code{frame}, is wrapping | |
2161 | an inlined frame. If it is not, it returns the existing frame decorator | |
2162 | untouched. If it is wrapping an inlined frame, it assumes that the | |
2163 | inlined frame was contained within the next oldest frame, | |
2164 | @code{eliding_frame}, which it fetches. It then creates and returns a | |
2165 | frame decorator, @code{ElidingFrameDecorator}, which contains both the | |
2166 | elided frame, and the eliding frame. | |
2167 | ||
2168 | @smallexample | |
2169 | class ElidingInlineDecorator(FrameDecorator): | |
2170 | ||
2171 | def __init__(self, frame, elided_frames): | |
2172 | super(ElidingInlineDecorator, self).__init__(frame) | |
2173 | self.frame = frame | |
2174 | self.elided_frames = elided_frames | |
2175 | ||
2176 | def elided(self): | |
2177 | return iter(self.elided_frames) | |
2178 | @end smallexample | |
2179 | ||
2180 | This frame decorator overrides one function and returns the inlined | |
2181 | frame in the @code{elided} method. As before it lets | |
2182 | @code{FrameDecorator} do the rest of the work involved in printing | |
2183 | this frame. This produces the following output. | |
2184 | ||
2185 | @smallexample | |
2186 | #0 0x004004e0 in bar () at inline.c:11 | |
2187 | #2 0x00400529 in main () at inline.c:25 | |
2188 | #1 0x00400529 in max (b=6, a=12) at inline.c:15 | |
2189 | @end smallexample | |
2190 | ||
2191 | In that output, @code{max} which has been inlined into @code{main} is | |
2192 | printed hierarchically. Another approach would be to combine the | |
2193 | @code{function} method, and the @code{elided} method to both print a | |
2194 | marker in the inlined frame, and also show the hierarchical | |
2195 | relationship. | |
2196 | ||
d11916aa SS |
2197 | @node Unwinding Frames in Python |
2198 | @subsubsection Unwinding Frames in Python | |
2199 | @cindex unwinding frames in Python | |
2200 | ||
2201 | In @value{GDBN} terminology ``unwinding'' is the process of finding | |
2202 | the previous frame (that is, caller's) from the current one. An | |
2203 | unwinder has three methods. The first one checks if it can handle | |
2204 | given frame (``sniff'' it). For the frames it can sniff an unwinder | |
2205 | provides two additional methods: it can return frame's ID, and it can | |
2206 | fetch registers from the previous frame. A running @value{GDBN} | |
2207 | mantains a list of the unwinders and calls each unwinder's sniffer in | |
2208 | turn until it finds the one that recognizes the current frame. There | |
2209 | is an API to register an unwinder. | |
2210 | ||
2211 | The unwinders that come with @value{GDBN} handle standard frames. | |
2212 | However, mixed language applications (for example, an application | |
2213 | running Java Virtual Machine) sometimes use frame layouts that cannot | |
2214 | be handled by the @value{GDBN} unwinders. You can write Python code | |
2215 | that can handle such custom frames. | |
2216 | ||
2217 | You implement a frame unwinder in Python as a class with which has two | |
2218 | attributes, @code{name} and @code{enabled}, with obvious meanings, and | |
2219 | a single method @code{__call__}, which examines a given frame and | |
2220 | returns an object (an instance of @code{gdb.UnwindInfo class)} | |
2221 | describing it. If an unwinder does not recognize a frame, it should | |
2222 | return @code{None}. The code in @value{GDBN} that enables writing | |
2223 | unwinders in Python uses this object to return frame's ID and previous | |
2224 | frame registers when @value{GDBN} core asks for them. | |
2225 | ||
2226 | @subheading Unwinder Input | |
2227 | ||
2228 | An object passed to an unwinder (a @code{gdb.PendingFrame} instance) | |
2229 | provides a method to read frame's registers: | |
2230 | ||
2231 | @defun PendingFrame.read_register (reg) | |
2232 | This method returns the contents of the register @var{regn} in the | |
2233 | frame as a @code{gdb.Value} object. @var{reg} can be either a | |
2234 | register number or a register name; the values are platform-specific. | |
2235 | They are usually found in the corresponding | |
2236 | @file{@var{platform}-tdep.h} file in the @value{GDBN} source tree. | |
2237 | @end defun | |
2238 | ||
2239 | It also provides a factory method to create a @code{gdb.UnwindInfo} | |
2240 | instance to be returned to @value{GDBN}: | |
2241 | ||
2242 | @defun PendingFrame.create_unwind_info (frame_id) | |
2243 | Returns a new @code{gdb.UnwindInfo} instance identified by given | |
2244 | @var{frame_id}. The argument is used to build @value{GDBN}'s frame ID | |
2245 | using one of functions provided by @value{GDBN}. @var{frame_id}'s attributes | |
2246 | determine which function will be used, as follows: | |
2247 | ||
2248 | @table @code | |
2249 | @item sp, pc, special | |
2250 | @code{frame_id_build_special (@var{frame_id}.sp, @var{frame_id}.pc, @var{frame_id}.special)} | |
2251 | ||
2252 | @item sp, pc | |
2253 | @code{frame_id_build (@var{frame_id}.sp, @var{frame_id}.pc)} | |
2254 | ||
2255 | This is the most common case. | |
2256 | ||
2257 | @item sp | |
2258 | @code{frame_id_build_wild (@var{frame_id}.sp)} | |
2259 | @end table | |
2260 | The attribute values should be @code{gdb.Value} | |
2261 | ||
2262 | @end defun | |
2263 | ||
2264 | @subheading Unwinder Output: UnwindInfo | |
2265 | ||
2266 | Use @code{PendingFrame.create_unwind_info} method described above to | |
2267 | create a @code{gdb.UnwindInfo} instance. Use the following method to | |
2268 | specify caller registers that have been saved in this frame: | |
2269 | ||
2270 | @defun gdb.UnwindInfo.add_saved_register (reg, value) | |
2271 | @var{reg} identifies the register. It can be a number or a name, just | |
2272 | as for the @code{PendingFrame.read_register} method above. | |
2273 | @var{value} is a register value (a @code{gdb.Value} object). | |
2274 | @end defun | |
2275 | ||
2276 | @subheading Unwinder Skeleton Code | |
2277 | ||
2278 | @value{GDBN} comes with the module containing the base @code{Unwinder} | |
2279 | class. Derive your unwinder class from it and structure the code as | |
2280 | follows: | |
2281 | ||
2282 | @smallexample | |
2283 | from gdb.unwinders import Unwinder | |
2284 | ||
2285 | class FrameId(object): | |
2286 | def __init__(self, sp, pc): | |
2287 | self.sp = sp | |
2288 | self.pc = pc | |
2289 | ||
2290 | ||
2291 | class MyUnwinder(Unwinder): | |
2292 | def __init__(....): | |
2293 | supe(MyUnwinder, self).__init___(<expects unwinder name argument>) | |
2294 | ||
2295 | def __call__(pending_frame): | |
2296 | if not <we recognize frame>: | |
2297 | return None | |
2298 | # Create UnwindInfo. Usually the frame is identified by the stack | |
2299 | # pointer and the program counter. | |
2300 | sp = pending_frame.read_register(<SP number>) | |
2301 | pc = pending_frame.read_register(<PC number>) | |
2302 | unwind_info = pending_frame.create_unwind_info(FrameId(sp, pc)) | |
2303 | ||
2304 | # Find the values of the registers in the caller's frame and | |
2305 | # save them in the result: | |
2306 | unwind_info.add_saved_register(<register>, <value>) | |
2307 | .... | |
2308 | ||
2309 | # Return the result: | |
2310 | return unwind_info | |
2311 | ||
2312 | @end smallexample | |
2313 | ||
2314 | @subheading Registering a Unwinder | |
2315 | ||
2316 | An object file, a program space, and the @value{GDBN} proper can have | |
2317 | unwinders registered with it. | |
2318 | ||
2319 | The @code{gdb.unwinders} module provides the function to register a | |
2320 | unwinder: | |
2321 | ||
2322 | @defun gdb.unwinder.register_unwinder (locus, unwinder, replace=False) | |
2323 | @var{locus} is specifies an object file or a program space to which | |
2324 | @var{unwinder} is added. Passing @code{None} or @code{gdb} adds | |
2325 | @var{unwinder} to the @value{GDBN}'s global unwinder list. The newly | |
2326 | added @var{unwinder} will be called before any other unwinder from the | |
2327 | same locus. Two unwinders in the same locus cannot have the same | |
2328 | name. An attempt to add a unwinder with already existing name raises | |
2329 | an exception unless @var{replace} is @code{True}, in which case the | |
2330 | old unwinder is deleted. | |
2331 | @end defun | |
2332 | ||
2333 | @subheading Unwinder Precedence | |
2334 | ||
2335 | @value{GDBN} first calls the unwinders from all the object files in no | |
2336 | particular order, then the unwinders from the current program space, | |
2337 | and finally the unwinders from @value{GDBN}. | |
2338 | ||
0c6e92a5 SC |
2339 | @node Xmethods In Python |
2340 | @subsubsection Xmethods In Python | |
2341 | @cindex xmethods in Python | |
2342 | ||
2343 | @dfn{Xmethods} are additional methods or replacements for existing | |
2344 | methods of a C@t{++} class. This feature is useful for those cases | |
2345 | where a method defined in C@t{++} source code could be inlined or | |
2346 | optimized out by the compiler, making it unavailable to @value{GDBN}. | |
2347 | For such cases, one can define an xmethod to serve as a replacement | |
2348 | for the method defined in the C@t{++} source code. @value{GDBN} will | |
2349 | then invoke the xmethod, instead of the C@t{++} method, to | |
2350 | evaluate expressions. One can also use xmethods when debugging | |
2351 | with core files. Moreover, when debugging live programs, invoking an | |
2352 | xmethod need not involve running the inferior (which can potentially | |
2353 | perturb its state). Hence, even if the C@t{++} method is available, it | |
2354 | is better to use its replacement xmethod if one is defined. | |
2355 | ||
2356 | The xmethods feature in Python is available via the concepts of an | |
2357 | @dfn{xmethod matcher} and an @dfn{xmethod worker}. To | |
2358 | implement an xmethod, one has to implement a matcher and a | |
2359 | corresponding worker for it (more than one worker can be | |
2360 | implemented, each catering to a different overloaded instance of the | |
2361 | method). Internally, @value{GDBN} invokes the @code{match} method of a | |
2362 | matcher to match the class type and method name. On a match, the | |
2363 | @code{match} method returns a list of matching @emph{worker} objects. | |
2364 | Each worker object typically corresponds to an overloaded instance of | |
2365 | the xmethod. They implement a @code{get_arg_types} method which | |
2366 | returns a sequence of types corresponding to the arguments the xmethod | |
2367 | requires. @value{GDBN} uses this sequence of types to perform | |
2368 | overload resolution and picks a winning xmethod worker. A winner | |
2369 | is also selected from among the methods @value{GDBN} finds in the | |
2370 | C@t{++} source code. Next, the winning xmethod worker and the | |
2371 | winning C@t{++} method are compared to select an overall winner. In | |
2372 | case of a tie between a xmethod worker and a C@t{++} method, the | |
2373 | xmethod worker is selected as the winner. That is, if a winning | |
2374 | xmethod worker is found to be equivalent to the winning C@t{++} | |
2375 | method, then the xmethod worker is treated as a replacement for | |
2376 | the C@t{++} method. @value{GDBN} uses the overall winner to invoke the | |
2377 | method. If the winning xmethod worker is the overall winner, then | |
897c3d32 | 2378 | the corresponding xmethod is invoked via the @code{__call__} method |
0c6e92a5 SC |
2379 | of the worker object. |
2380 | ||
2381 | If one wants to implement an xmethod as a replacement for an | |
2382 | existing C@t{++} method, then they have to implement an equivalent | |
2383 | xmethod which has exactly the same name and takes arguments of | |
2384 | exactly the same type as the C@t{++} method. If the user wants to | |
2385 | invoke the C@t{++} method even though a replacement xmethod is | |
2386 | available for that method, then they can disable the xmethod. | |
2387 | ||
2388 | @xref{Xmethod API}, for API to implement xmethods in Python. | |
2389 | @xref{Writing an Xmethod}, for implementing xmethods in Python. | |
2390 | ||
2391 | @node Xmethod API | |
2392 | @subsubsection Xmethod API | |
2393 | @cindex xmethod API | |
2394 | ||
2395 | The @value{GDBN} Python API provides classes, interfaces and functions | |
2396 | to implement, register and manipulate xmethods. | |
2397 | @xref{Xmethods In Python}. | |
2398 | ||
2399 | An xmethod matcher should be an instance of a class derived from | |
2400 | @code{XMethodMatcher} defined in the module @code{gdb.xmethod}, or an | |
2401 | object with similar interface and attributes. An instance of | |
2402 | @code{XMethodMatcher} has the following attributes: | |
2403 | ||
2404 | @defvar name | |
2405 | The name of the matcher. | |
2406 | @end defvar | |
2407 | ||
2408 | @defvar enabled | |
2409 | A boolean value indicating whether the matcher is enabled or disabled. | |
2410 | @end defvar | |
2411 | ||
2412 | @defvar methods | |
2413 | A list of named methods managed by the matcher. Each object in the list | |
2414 | is an instance of the class @code{XMethod} defined in the module | |
2415 | @code{gdb.xmethod}, or any object with the following attributes: | |
2416 | ||
2417 | @table @code | |
2418 | ||
2419 | @item name | |
2420 | Name of the xmethod which should be unique for each xmethod | |
2421 | managed by the matcher. | |
2422 | ||
2423 | @item enabled | |
2424 | A boolean value indicating whether the xmethod is enabled or | |
2425 | disabled. | |
2426 | ||
2427 | @end table | |
2428 | ||
2429 | The class @code{XMethod} is a convenience class with same | |
2430 | attributes as above along with the following constructor: | |
2431 | ||
dd5d5494 | 2432 | @defun XMethod.__init__ (self, name) |
0c6e92a5 SC |
2433 | Constructs an enabled xmethod with name @var{name}. |
2434 | @end defun | |
2435 | @end defvar | |
2436 | ||
2437 | @noindent | |
2438 | The @code{XMethodMatcher} class has the following methods: | |
2439 | ||
dd5d5494 | 2440 | @defun XMethodMatcher.__init__ (self, name) |
0c6e92a5 SC |
2441 | Constructs an enabled xmethod matcher with name @var{name}. The |
2442 | @code{methods} attribute is initialized to @code{None}. | |
2443 | @end defun | |
2444 | ||
dd5d5494 | 2445 | @defun XMethodMatcher.match (self, class_type, method_name) |
0c6e92a5 SC |
2446 | Derived classes should override this method. It should return a |
2447 | xmethod worker object (or a sequence of xmethod worker | |
2448 | objects) matching the @var{class_type} and @var{method_name}. | |
2449 | @var{class_type} is a @code{gdb.Type} object, and @var{method_name} | |
2450 | is a string value. If the matcher manages named methods as listed in | |
2451 | its @code{methods} attribute, then only those worker objects whose | |
2452 | corresponding entries in the @code{methods} list are enabled should be | |
2453 | returned. | |
2454 | @end defun | |
2455 | ||
2456 | An xmethod worker should be an instance of a class derived from | |
2457 | @code{XMethodWorker} defined in the module @code{gdb.xmethod}, | |
2458 | or support the following interface: | |
2459 | ||
dd5d5494 | 2460 | @defun XMethodWorker.get_arg_types (self) |
0c6e92a5 SC |
2461 | This method returns a sequence of @code{gdb.Type} objects corresponding |
2462 | to the arguments that the xmethod takes. It can return an empty | |
2463 | sequence or @code{None} if the xmethod does not take any arguments. | |
2464 | If the xmethod takes a single argument, then a single | |
2465 | @code{gdb.Type} object corresponding to it can be returned. | |
2466 | @end defun | |
2467 | ||
2ce1cdbf DE |
2468 | @defun XMethodWorker.get_result_type (self, *args) |
2469 | This method returns a @code{gdb.Type} object representing the type | |
2470 | of the result of invoking this xmethod. | |
2471 | The @var{args} argument is the same tuple of arguments that would be | |
2472 | passed to the @code{__call__} method of this worker. | |
2473 | @end defun | |
2474 | ||
dd5d5494 | 2475 | @defun XMethodWorker.__call__ (self, *args) |
0c6e92a5 SC |
2476 | This is the method which does the @emph{work} of the xmethod. The |
2477 | @var{args} arguments is the tuple of arguments to the xmethod. Each | |
2478 | element in this tuple is a gdb.Value object. The first element is | |
2479 | always the @code{this} pointer value. | |
2480 | @end defun | |
2481 | ||
2482 | For @value{GDBN} to lookup xmethods, the xmethod matchers | |
2483 | should be registered using the following function defined in the module | |
2484 | @code{gdb.xmethod}: | |
2485 | ||
dd5d5494 | 2486 | @defun register_xmethod_matcher (locus, matcher, replace=False) |
0c6e92a5 SC |
2487 | The @code{matcher} is registered with @code{locus}, replacing an |
2488 | existing matcher with the same name as @code{matcher} if | |
2489 | @code{replace} is @code{True}. @code{locus} can be a | |
2490 | @code{gdb.Objfile} object (@pxref{Objfiles In Python}), or a | |
1e47491b | 2491 | @code{gdb.Progspace} object (@pxref{Progspaces In Python}), or |
0c6e92a5 SC |
2492 | @code{None}. If it is @code{None}, then @code{matcher} is registered |
2493 | globally. | |
2494 | @end defun | |
2495 | ||
2496 | @node Writing an Xmethod | |
2497 | @subsubsection Writing an Xmethod | |
2498 | @cindex writing xmethods in Python | |
2499 | ||
2500 | Implementing xmethods in Python will require implementing xmethod | |
2501 | matchers and xmethod workers (@pxref{Xmethods In Python}). Consider | |
2502 | the following C@t{++} class: | |
2503 | ||
2504 | @smallexample | |
2505 | class MyClass | |
2506 | @{ | |
2507 | public: | |
2508 | MyClass (int a) : a_(a) @{ @} | |
2509 | ||
2510 | int geta (void) @{ return a_; @} | |
2511 | int operator+ (int b); | |
2512 | ||
2513 | private: | |
2514 | int a_; | |
2515 | @}; | |
2516 | ||
2517 | int | |
2518 | MyClass::operator+ (int b) | |
2519 | @{ | |
2520 | return a_ + b; | |
2521 | @} | |
2522 | @end smallexample | |
2523 | ||
2524 | @noindent | |
2525 | Let us define two xmethods for the class @code{MyClass}, one | |
2526 | replacing the method @code{geta}, and another adding an overloaded | |
2527 | flavor of @code{operator+} which takes a @code{MyClass} argument (the | |
2528 | C@t{++} code above already has an overloaded @code{operator+} | |
2529 | which takes an @code{int} argument). The xmethod matcher can be | |
2530 | defined as follows: | |
2531 | ||
2532 | @smallexample | |
2533 | class MyClass_geta(gdb.xmethod.XMethod): | |
2534 | def __init__(self): | |
2535 | gdb.xmethod.XMethod.__init__(self, 'geta') | |
2536 | ||
2537 | def get_worker(self, method_name): | |
2538 | if method_name == 'geta': | |
2539 | return MyClassWorker_geta() | |
2540 | ||
2541 | ||
2542 | class MyClass_sum(gdb.xmethod.XMethod): | |
2543 | def __init__(self): | |
2544 | gdb.xmethod.XMethod.__init__(self, 'sum') | |
2545 | ||
2546 | def get_worker(self, method_name): | |
2547 | if method_name == 'operator+': | |
2548 | return MyClassWorker_plus() | |
2549 | ||
2550 | ||
2551 | class MyClassMatcher(gdb.xmethod.XMethodMatcher): | |
2552 | def __init__(self): | |
2553 | gdb.xmethod.XMethodMatcher.__init__(self, 'MyClassMatcher') | |
2554 | # List of methods 'managed' by this matcher | |
2555 | self.methods = [MyClass_geta(), MyClass_sum()] | |
2556 | ||
2557 | def match(self, class_type, method_name): | |
2558 | if class_type.tag != 'MyClass': | |
2559 | return None | |
2560 | workers = [] | |
2561 | for method in self.methods: | |
2562 | if method.enabled: | |
2563 | worker = method.get_worker(method_name) | |
2564 | if worker: | |
2565 | workers.append(worker) | |
2566 | ||
2567 | return workers | |
2568 | @end smallexample | |
2569 | ||
2570 | @noindent | |
2571 | Notice that the @code{match} method of @code{MyClassMatcher} returns | |
2572 | a worker object of type @code{MyClassWorker_geta} for the @code{geta} | |
2573 | method, and a worker object of type @code{MyClassWorker_plus} for the | |
2574 | @code{operator+} method. This is done indirectly via helper classes | |
2575 | derived from @code{gdb.xmethod.XMethod}. One does not need to use the | |
2576 | @code{methods} attribute in a matcher as it is optional. However, if a | |
2577 | matcher manages more than one xmethod, it is a good practice to list the | |
2578 | xmethods in the @code{methods} attribute of the matcher. This will then | |
2579 | facilitate enabling and disabling individual xmethods via the | |
2580 | @code{enable/disable} commands. Notice also that a worker object is | |
2581 | returned only if the corresponding entry in the @code{methods} attribute | |
2582 | of the matcher is enabled. | |
2583 | ||
2584 | The implementation of the worker classes returned by the matcher setup | |
2585 | above is as follows: | |
2586 | ||
2587 | @smallexample | |
2588 | class MyClassWorker_geta(gdb.xmethod.XMethodWorker): | |
2589 | def get_arg_types(self): | |
2590 | return None | |
2ce1cdbf DE |
2591 | |
2592 | def get_result_type(self, obj): | |
2593 | return gdb.lookup_type('int') | |
0c6e92a5 SC |
2594 | |
2595 | def __call__(self, obj): | |
2596 | return obj['a_'] | |
2597 | ||
2598 | ||
2599 | class MyClassWorker_plus(gdb.xmethod.XMethodWorker): | |
2600 | def get_arg_types(self): | |
2601 | return gdb.lookup_type('MyClass') | |
2ce1cdbf DE |
2602 | |
2603 | def get_result_type(self, obj): | |
2604 | return gdb.lookup_type('int') | |
0c6e92a5 SC |
2605 | |
2606 | def __call__(self, obj, other): | |
2607 | return obj['a_'] + other['a_'] | |
2608 | @end smallexample | |
2609 | ||
2610 | For @value{GDBN} to actually lookup a xmethod, it has to be | |
2611 | registered with it. The matcher defined above is registered with | |
2612 | @value{GDBN} globally as follows: | |
2613 | ||
2614 | @smallexample | |
2615 | gdb.xmethod.register_xmethod_matcher(None, MyClassMatcher()) | |
2616 | @end smallexample | |
2617 | ||
2618 | If an object @code{obj} of type @code{MyClass} is initialized in C@t{++} | |
2619 | code as follows: | |
2620 | ||
2621 | @smallexample | |
2622 | MyClass obj(5); | |
2623 | @end smallexample | |
2624 | ||
2625 | @noindent | |
2626 | then, after loading the Python script defining the xmethod matchers | |
2627 | and workers into @code{GDBN}, invoking the method @code{geta} or using | |
2628 | the operator @code{+} on @code{obj} will invoke the xmethods | |
2629 | defined above: | |
2630 | ||
2631 | @smallexample | |
2632 | (gdb) p obj.geta() | |
2633 | $1 = 5 | |
2634 | ||
2635 | (gdb) p obj + obj | |
2636 | $2 = 10 | |
2637 | @end smallexample | |
2638 | ||
2639 | Consider another example with a C++ template class: | |
2640 | ||
2641 | @smallexample | |
2642 | template <class T> | |
2643 | class MyTemplate | |
2644 | @{ | |
2645 | public: | |
2646 | MyTemplate () : dsize_(10), data_ (new T [10]) @{ @} | |
2647 | ~MyTemplate () @{ delete [] data_; @} | |
2648 | ||
2649 | int footprint (void) | |
2650 | @{ | |
2651 | return sizeof (T) * dsize_ + sizeof (MyTemplate<T>); | |
2652 | @} | |
2653 | ||
2654 | private: | |
2655 | int dsize_; | |
2656 | T *data_; | |
2657 | @}; | |
2658 | @end smallexample | |
2659 | ||
2660 | Let us implement an xmethod for the above class which serves as a | |
2661 | replacement for the @code{footprint} method. The full code listing | |
2662 | of the xmethod workers and xmethod matchers is as follows: | |
2663 | ||
2664 | @smallexample | |
2665 | class MyTemplateWorker_footprint(gdb.xmethod.XMethodWorker): | |
2666 | def __init__(self, class_type): | |
2667 | self.class_type = class_type | |
2ce1cdbf | 2668 | |
0c6e92a5 SC |
2669 | def get_arg_types(self): |
2670 | return None | |
2ce1cdbf DE |
2671 | |
2672 | def get_result_type(self): | |
2673 | return gdb.lookup_type('int') | |
2674 | ||
0c6e92a5 SC |
2675 | def __call__(self, obj): |
2676 | return (self.class_type.sizeof + | |
2677 | obj['dsize_'] * | |
2678 | self.class_type.template_argument(0).sizeof) | |
2679 | ||
2680 | ||
2681 | class MyTemplateMatcher_footprint(gdb.xmethod.XMethodMatcher): | |
2682 | def __init__(self): | |
2683 | gdb.xmethod.XMethodMatcher.__init__(self, 'MyTemplateMatcher') | |
2684 | ||
2685 | def match(self, class_type, method_name): | |
2686 | if (re.match('MyTemplate<[ \t\n]*[_a-zA-Z][ _a-zA-Z0-9]*>', | |
2687 | class_type.tag) and | |
2688 | method_name == 'footprint'): | |
2689 | return MyTemplateWorker_footprint(class_type) | |
2690 | @end smallexample | |
2691 | ||
2692 | Notice that, in this example, we have not used the @code{methods} | |
2693 | attribute of the matcher as the matcher manages only one xmethod. The | |
2694 | user can enable/disable this xmethod by enabling/disabling the matcher | |
2695 | itself. | |
2696 | ||
329baa95 DE |
2697 | @node Inferiors In Python |
2698 | @subsubsection Inferiors In Python | |
2699 | @cindex inferiors in Python | |
2700 | ||
2701 | @findex gdb.Inferior | |
2702 | Programs which are being run under @value{GDBN} are called inferiors | |
2703 | (@pxref{Inferiors and Programs}). Python scripts can access | |
2704 | information about and manipulate inferiors controlled by @value{GDBN} | |
2705 | via objects of the @code{gdb.Inferior} class. | |
2706 | ||
2707 | The following inferior-related functions are available in the @code{gdb} | |
2708 | module: | |
2709 | ||
2710 | @defun gdb.inferiors () | |
2711 | Return a tuple containing all inferior objects. | |
2712 | @end defun | |
2713 | ||
2714 | @defun gdb.selected_inferior () | |
2715 | Return an object representing the current inferior. | |
2716 | @end defun | |
2717 | ||
2718 | A @code{gdb.Inferior} object has the following attributes: | |
2719 | ||
2720 | @defvar Inferior.num | |
2721 | ID of inferior, as assigned by GDB. | |
2722 | @end defvar | |
2723 | ||
2724 | @defvar Inferior.pid | |
2725 | Process ID of the inferior, as assigned by the underlying operating | |
2726 | system. | |
2727 | @end defvar | |
2728 | ||
2729 | @defvar Inferior.was_attached | |
2730 | Boolean signaling whether the inferior was created using `attach', or | |
2731 | started by @value{GDBN} itself. | |
2732 | @end defvar | |
2733 | ||
2734 | A @code{gdb.Inferior} object has the following methods: | |
2735 | ||
2736 | @defun Inferior.is_valid () | |
2737 | Returns @code{True} if the @code{gdb.Inferior} object is valid, | |
2738 | @code{False} if not. A @code{gdb.Inferior} object will become invalid | |
2739 | if the inferior no longer exists within @value{GDBN}. All other | |
2740 | @code{gdb.Inferior} methods will throw an exception if it is invalid | |
2741 | at the time the method is called. | |
2742 | @end defun | |
2743 | ||
2744 | @defun Inferior.threads () | |
2745 | This method returns a tuple holding all the threads which are valid | |
2746 | when it is called. If there are no valid threads, the method will | |
2747 | return an empty tuple. | |
2748 | @end defun | |
2749 | ||
2750 | @findex Inferior.read_memory | |
2751 | @defun Inferior.read_memory (address, length) | |
a86c90e6 | 2752 | Read @var{length} addressable memory units from the inferior, starting at |
329baa95 DE |
2753 | @var{address}. Returns a buffer object, which behaves much like an array |
2754 | or a string. It can be modified and given to the | |
2755 | @code{Inferior.write_memory} function. In @code{Python} 3, the return | |
2756 | value is a @code{memoryview} object. | |
2757 | @end defun | |
2758 | ||
2759 | @findex Inferior.write_memory | |
2760 | @defun Inferior.write_memory (address, buffer @r{[}, length@r{]}) | |
2761 | Write the contents of @var{buffer} to the inferior, starting at | |
2762 | @var{address}. The @var{buffer} parameter must be a Python object | |
2763 | which supports the buffer protocol, i.e., a string, an array or the | |
2764 | object returned from @code{Inferior.read_memory}. If given, @var{length} | |
a86c90e6 SM |
2765 | determines the number of addressable memory units from @var{buffer} to be |
2766 | written. | |
329baa95 DE |
2767 | @end defun |
2768 | ||
2769 | @findex gdb.search_memory | |
2770 | @defun Inferior.search_memory (address, length, pattern) | |
2771 | Search a region of the inferior memory starting at @var{address} with | |
2772 | the given @var{length} using the search pattern supplied in | |
2773 | @var{pattern}. The @var{pattern} parameter must be a Python object | |
2774 | which supports the buffer protocol, i.e., a string, an array or the | |
2775 | object returned from @code{gdb.read_memory}. Returns a Python @code{Long} | |
2776 | containing the address where the pattern was found, or @code{None} if | |
2777 | the pattern could not be found. | |
2778 | @end defun | |
2779 | ||
2780 | @node Events In Python | |
2781 | @subsubsection Events In Python | |
2782 | @cindex inferior events in Python | |
2783 | ||
2784 | @value{GDBN} provides a general event facility so that Python code can be | |
2785 | notified of various state changes, particularly changes that occur in | |
2786 | the inferior. | |
2787 | ||
2788 | An @dfn{event} is just an object that describes some state change. The | |
2789 | type of the object and its attributes will vary depending on the details | |
2790 | of the change. All the existing events are described below. | |
2791 | ||
2792 | In order to be notified of an event, you must register an event handler | |
2793 | with an @dfn{event registry}. An event registry is an object in the | |
2794 | @code{gdb.events} module which dispatches particular events. A registry | |
2795 | provides methods to register and unregister event handlers: | |
2796 | ||
2797 | @defun EventRegistry.connect (object) | |
2798 | Add the given callable @var{object} to the registry. This object will be | |
2799 | called when an event corresponding to this registry occurs. | |
2800 | @end defun | |
2801 | ||
2802 | @defun EventRegistry.disconnect (object) | |
2803 | Remove the given @var{object} from the registry. Once removed, the object | |
2804 | will no longer receive notifications of events. | |
2805 | @end defun | |
2806 | ||
2807 | Here is an example: | |
2808 | ||
2809 | @smallexample | |
2810 | def exit_handler (event): | |
2811 | print "event type: exit" | |
2812 | print "exit code: %d" % (event.exit_code) | |
2813 | ||
2814 | gdb.events.exited.connect (exit_handler) | |
2815 | @end smallexample | |
2816 | ||
2817 | In the above example we connect our handler @code{exit_handler} to the | |
2818 | registry @code{events.exited}. Once connected, @code{exit_handler} gets | |
2819 | called when the inferior exits. The argument @dfn{event} in this example is | |
2820 | of type @code{gdb.ExitedEvent}. As you can see in the example the | |
2821 | @code{ExitedEvent} object has an attribute which indicates the exit code of | |
2822 | the inferior. | |
2823 | ||
2824 | The following is a listing of the event registries that are available and | |
2825 | details of the events they emit: | |
2826 | ||
2827 | @table @code | |
2828 | ||
2829 | @item events.cont | |
2830 | Emits @code{gdb.ThreadEvent}. | |
2831 | ||
2832 | Some events can be thread specific when @value{GDBN} is running in non-stop | |
2833 | mode. When represented in Python, these events all extend | |
2834 | @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead, | |
2835 | events which are emitted by this or other modules might extend this event. | |
2836 | Examples of these events are @code{gdb.BreakpointEvent} and | |
2837 | @code{gdb.ContinueEvent}. | |
2838 | ||
2839 | @defvar ThreadEvent.inferior_thread | |
2840 | In non-stop mode this attribute will be set to the specific thread which was | |
2841 | involved in the emitted event. Otherwise, it will be set to @code{None}. | |
2842 | @end defvar | |
2843 | ||
2844 | Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}. | |
2845 | ||
2846 | This event indicates that the inferior has been continued after a stop. For | |
2847 | inherited attribute refer to @code{gdb.ThreadEvent} above. | |
2848 | ||
2849 | @item events.exited | |
2850 | Emits @code{events.ExitedEvent} which indicates that the inferior has exited. | |
2851 | @code{events.ExitedEvent} has two attributes: | |
2852 | @defvar ExitedEvent.exit_code | |
2853 | An integer representing the exit code, if available, which the inferior | |
2854 | has returned. (The exit code could be unavailable if, for example, | |
2855 | @value{GDBN} detaches from the inferior.) If the exit code is unavailable, | |
2856 | the attribute does not exist. | |
2857 | @end defvar | |
2858 | @defvar ExitedEvent inferior | |
2859 | A reference to the inferior which triggered the @code{exited} event. | |
2860 | @end defvar | |
2861 | ||
2862 | @item events.stop | |
2863 | Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}. | |
2864 | ||
2865 | Indicates that the inferior has stopped. All events emitted by this registry | |
2866 | extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent} | |
2867 | will indicate the stopped thread when @value{GDBN} is running in non-stop | |
2868 | mode. Refer to @code{gdb.ThreadEvent} above for more details. | |
2869 | ||
2870 | Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}. | |
2871 | ||
2872 | This event indicates that the inferior or one of its threads has received as | |
2873 | signal. @code{gdb.SignalEvent} has the following attributes: | |
2874 | ||
2875 | @defvar SignalEvent.stop_signal | |
2876 | A string representing the signal received by the inferior. A list of possible | |
2877 | signal values can be obtained by running the command @code{info signals} in | |
2878 | the @value{GDBN} command prompt. | |
2879 | @end defvar | |
2880 | ||
2881 | Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}. | |
2882 | ||
2883 | @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have | |
2884 | been hit, and has the following attributes: | |
2885 | ||
2886 | @defvar BreakpointEvent.breakpoints | |
2887 | A sequence containing references to all the breakpoints (type | |
2888 | @code{gdb.Breakpoint}) that were hit. | |
2889 | @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object. | |
2890 | @end defvar | |
2891 | @defvar BreakpointEvent.breakpoint | |
2892 | A reference to the first breakpoint that was hit. | |
2893 | This function is maintained for backward compatibility and is now deprecated | |
2894 | in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute. | |
2895 | @end defvar | |
2896 | ||
2897 | @item events.new_objfile | |
2898 | Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has | |
2899 | been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute: | |
2900 | ||
2901 | @defvar NewObjFileEvent.new_objfile | |
2902 | A reference to the object file (@code{gdb.Objfile}) which has been loaded. | |
2903 | @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object. | |
2904 | @end defvar | |
2905 | ||
4ffbba72 DE |
2906 | @item events.clear_objfiles |
2907 | Emits @code{gdb.ClearObjFilesEvent} which indicates that the list of object | |
2908 | files for a program space has been reset. | |
2909 | @code{gdb.ClearObjFilesEvent} has one attribute: | |
2910 | ||
2911 | @defvar ClearObjFilesEvent.progspace | |
2912 | A reference to the program space (@code{gdb.Progspace}) whose objfile list has | |
2913 | been cleared. @xref{Progspaces In Python}. | |
2914 | @end defvar | |
2915 | ||
162078c8 NB |
2916 | @item events.inferior_call_pre |
2917 | Emits @code{gdb.InferiorCallPreEvent} which indicates that a function in | |
2918 | the inferior is about to be called. | |
2919 | ||
2920 | @defvar InferiorCallPreEvent.ptid | |
2921 | The thread in which the call will be run. | |
2922 | @end defvar | |
2923 | ||
2924 | @defvar InferiorCallPreEvent.address | |
2925 | The location of the function to be called. | |
2926 | @end defvar | |
2927 | ||
2928 | @item events.inferior_call_post | |
2929 | Emits @code{gdb.InferiorCallPostEvent} which indicates that a function in | |
2930 | the inferior has returned. | |
2931 | ||
2932 | @defvar InferiorCallPostEvent.ptid | |
2933 | The thread in which the call was run. | |
2934 | @end defvar | |
2935 | ||
2936 | @defvar InferiorCallPostEvent.address | |
2937 | The location of the function that was called. | |
2938 | @end defvar | |
2939 | ||
2940 | @item events.memory_changed | |
2941 | Emits @code{gdb.MemoryChangedEvent} which indicates that the memory of the | |
2942 | inferior has been modified by the @value{GDBN} user, for instance via a | |
2943 | command like @w{@code{set *addr = value}}. The event has the following | |
2944 | attributes: | |
2945 | ||
2946 | @defvar MemoryChangedEvent.address | |
2947 | The start address of the changed region. | |
2948 | @end defvar | |
2949 | ||
2950 | @defvar MemoryChangedEvent.length | |
2951 | Length in bytes of the changed region. | |
2952 | @end defvar | |
2953 | ||
2954 | @item events.register_changed | |
2955 | Emits @code{gdb.RegisterChangedEvent} which indicates that a register in the | |
2956 | inferior has been modified by the @value{GDBN} user. | |
2957 | ||
2958 | @defvar RegisterChangedEvent.frame | |
2959 | A gdb.Frame object representing the frame in which the register was modified. | |
2960 | @end defvar | |
2961 | @defvar RegisterChangedEvent.regnum | |
2962 | Denotes which register was modified. | |
2963 | @end defvar | |
2964 | ||
329baa95 DE |
2965 | @end table |
2966 | ||
2967 | @node Threads In Python | |
2968 | @subsubsection Threads In Python | |
2969 | @cindex threads in python | |
2970 | ||
2971 | @findex gdb.InferiorThread | |
2972 | Python scripts can access information about, and manipulate inferior threads | |
2973 | controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class. | |
2974 | ||
2975 | The following thread-related functions are available in the @code{gdb} | |
2976 | module: | |
2977 | ||
2978 | @findex gdb.selected_thread | |
2979 | @defun gdb.selected_thread () | |
2980 | This function returns the thread object for the selected thread. If there | |
2981 | is no selected thread, this will return @code{None}. | |
2982 | @end defun | |
2983 | ||
2984 | A @code{gdb.InferiorThread} object has the following attributes: | |
2985 | ||
2986 | @defvar InferiorThread.name | |
2987 | The name of the thread. If the user specified a name using | |
2988 | @code{thread name}, then this returns that name. Otherwise, if an | |
2989 | OS-supplied name is available, then it is returned. Otherwise, this | |
2990 | returns @code{None}. | |
2991 | ||
2992 | This attribute can be assigned to. The new value must be a string | |
2993 | object, which sets the new name, or @code{None}, which removes any | |
2994 | user-specified thread name. | |
2995 | @end defvar | |
2996 | ||
2997 | @defvar InferiorThread.num | |
5d5658a1 | 2998 | The per-inferior number of the thread, as assigned by GDB. |
329baa95 DE |
2999 | @end defvar |
3000 | ||
22a02324 PA |
3001 | @defvar InferiorThread.global_num |
3002 | The global ID of the thread, as assigned by GDB. You can use this to | |
3003 | make Python breakpoints thread-specific, for example | |
3004 | (@pxref{python_breakpoint_thread,,The Breakpoint.thread attribute}). | |
3005 | @end defvar | |
3006 | ||
329baa95 DE |
3007 | @defvar InferiorThread.ptid |
3008 | ID of the thread, as assigned by the operating system. This attribute is a | |
3009 | tuple containing three integers. The first is the Process ID (PID); the second | |
3010 | is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID). | |
3011 | Either the LWPID or TID may be 0, which indicates that the operating system | |
3012 | does not use that identifier. | |
3013 | @end defvar | |
3014 | ||
84654457 PA |
3015 | @defvar InferiorThread.inferior |
3016 | The inferior this thread belongs to. This attribute is represented as | |
3017 | a @code{gdb.Inferior} object. This attribute is not writable. | |
3018 | @end defvar | |
3019 | ||
329baa95 DE |
3020 | A @code{gdb.InferiorThread} object has the following methods: |
3021 | ||
3022 | @defun InferiorThread.is_valid () | |
3023 | Returns @code{True} if the @code{gdb.InferiorThread} object is valid, | |
3024 | @code{False} if not. A @code{gdb.InferiorThread} object will become | |
3025 | invalid if the thread exits, or the inferior that the thread belongs | |
3026 | is deleted. All other @code{gdb.InferiorThread} methods will throw an | |
3027 | exception if it is invalid at the time the method is called. | |
3028 | @end defun | |
3029 | ||
3030 | @defun InferiorThread.switch () | |
3031 | This changes @value{GDBN}'s currently selected thread to the one represented | |
3032 | by this object. | |
3033 | @end defun | |
3034 | ||
3035 | @defun InferiorThread.is_stopped () | |
3036 | Return a Boolean indicating whether the thread is stopped. | |
3037 | @end defun | |
3038 | ||
3039 | @defun InferiorThread.is_running () | |
3040 | Return a Boolean indicating whether the thread is running. | |
3041 | @end defun | |
3042 | ||
3043 | @defun InferiorThread.is_exited () | |
3044 | Return a Boolean indicating whether the thread is exited. | |
3045 | @end defun | |
3046 | ||
3047 | @node Commands In Python | |
3048 | @subsubsection Commands In Python | |
3049 | ||
3050 | @cindex commands in python | |
3051 | @cindex python commands | |
3052 | You can implement new @value{GDBN} CLI commands in Python. A CLI | |
3053 | command is implemented using an instance of the @code{gdb.Command} | |
3054 | class, most commonly using a subclass. | |
3055 | ||
3056 | @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]}) | |
3057 | The object initializer for @code{Command} registers the new command | |
3058 | with @value{GDBN}. This initializer is normally invoked from the | |
3059 | subclass' own @code{__init__} method. | |
3060 | ||
3061 | @var{name} is the name of the command. If @var{name} consists of | |
3062 | multiple words, then the initial words are looked for as prefix | |
3063 | commands. In this case, if one of the prefix commands does not exist, | |
3064 | an exception is raised. | |
3065 | ||
3066 | There is no support for multi-line commands. | |
3067 | ||
3068 | @var{command_class} should be one of the @samp{COMMAND_} constants | |
3069 | defined below. This argument tells @value{GDBN} how to categorize the | |
3070 | new command in the help system. | |
3071 | ||
3072 | @var{completer_class} is an optional argument. If given, it should be | |
3073 | one of the @samp{COMPLETE_} constants defined below. This argument | |
3074 | tells @value{GDBN} how to perform completion for this command. If not | |
3075 | given, @value{GDBN} will attempt to complete using the object's | |
3076 | @code{complete} method (see below); if no such method is found, an | |
3077 | error will occur when completion is attempted. | |
3078 | ||
3079 | @var{prefix} is an optional argument. If @code{True}, then the new | |
3080 | command is a prefix command; sub-commands of this command may be | |
3081 | registered. | |
3082 | ||
3083 | The help text for the new command is taken from the Python | |
3084 | documentation string for the command's class, if there is one. If no | |
3085 | documentation string is provided, the default value ``This command is | |
3086 | not documented.'' is used. | |
3087 | @end defun | |
3088 | ||
3089 | @cindex don't repeat Python command | |
3090 | @defun Command.dont_repeat () | |
3091 | By default, a @value{GDBN} command is repeated when the user enters a | |
3092 | blank line at the command prompt. A command can suppress this | |
3093 | behavior by invoking the @code{dont_repeat} method. This is similar | |
3094 | to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}. | |
3095 | @end defun | |
3096 | ||
3097 | @defun Command.invoke (argument, from_tty) | |
3098 | This method is called by @value{GDBN} when this command is invoked. | |
3099 | ||
3100 | @var{argument} is a string. It is the argument to the command, after | |
3101 | leading and trailing whitespace has been stripped. | |
3102 | ||
3103 | @var{from_tty} is a boolean argument. When true, this means that the | |
3104 | command was entered by the user at the terminal; when false it means | |
3105 | that the command came from elsewhere. | |
3106 | ||
3107 | If this method throws an exception, it is turned into a @value{GDBN} | |
3108 | @code{error} call. Otherwise, the return value is ignored. | |
3109 | ||
3110 | @findex gdb.string_to_argv | |
3111 | To break @var{argument} up into an argv-like string use | |
3112 | @code{gdb.string_to_argv}. This function behaves identically to | |
3113 | @value{GDBN}'s internal argument lexer @code{buildargv}. | |
3114 | It is recommended to use this for consistency. | |
3115 | Arguments are separated by spaces and may be quoted. | |
3116 | Example: | |
3117 | ||
3118 | @smallexample | |
3119 | print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"") | |
3120 | ['1', '2 "3', '4 "5', "6 '7"] | |
3121 | @end smallexample | |
3122 | ||
3123 | @end defun | |
3124 | ||
3125 | @cindex completion of Python commands | |
3126 | @defun Command.complete (text, word) | |
3127 | This method is called by @value{GDBN} when the user attempts | |
3128 | completion on this command. All forms of completion are handled by | |
3129 | this method, that is, the @key{TAB} and @key{M-?} key bindings | |
3130 | (@pxref{Completion}), and the @code{complete} command (@pxref{Help, | |
3131 | complete}). | |
3132 | ||
697aa1b7 EZ |
3133 | The arguments @var{text} and @var{word} are both strings; @var{text} |
3134 | holds the complete command line up to the cursor's location, while | |
329baa95 DE |
3135 | @var{word} holds the last word of the command line; this is computed |
3136 | using a word-breaking heuristic. | |
3137 | ||
3138 | The @code{complete} method can return several values: | |
3139 | @itemize @bullet | |
3140 | @item | |
3141 | If the return value is a sequence, the contents of the sequence are | |
3142 | used as the completions. It is up to @code{complete} to ensure that the | |
3143 | contents actually do complete the word. A zero-length sequence is | |
3144 | allowed, it means that there were no completions available. Only | |
3145 | string elements of the sequence are used; other elements in the | |
3146 | sequence are ignored. | |
3147 | ||
3148 | @item | |
3149 | If the return value is one of the @samp{COMPLETE_} constants defined | |
3150 | below, then the corresponding @value{GDBN}-internal completion | |
3151 | function is invoked, and its result is used. | |
3152 | ||
3153 | @item | |
3154 | All other results are treated as though there were no available | |
3155 | completions. | |
3156 | @end itemize | |
3157 | @end defun | |
3158 | ||
3159 | When a new command is registered, it must be declared as a member of | |
3160 | some general class of commands. This is used to classify top-level | |
3161 | commands in the on-line help system; note that prefix commands are not | |
3162 | listed under their own category but rather that of their top-level | |
3163 | command. The available classifications are represented by constants | |
3164 | defined in the @code{gdb} module: | |
3165 | ||
3166 | @table @code | |
3167 | @findex COMMAND_NONE | |
3168 | @findex gdb.COMMAND_NONE | |
3169 | @item gdb.COMMAND_NONE | |
3170 | The command does not belong to any particular class. A command in | |
3171 | this category will not be displayed in any of the help categories. | |
3172 | ||
3173 | @findex COMMAND_RUNNING | |
3174 | @findex gdb.COMMAND_RUNNING | |
3175 | @item gdb.COMMAND_RUNNING | |
3176 | The command is related to running the inferior. For example, | |
3177 | @code{start}, @code{step}, and @code{continue} are in this category. | |
3178 | Type @kbd{help running} at the @value{GDBN} prompt to see a list of | |
3179 | commands in this category. | |
3180 | ||
3181 | @findex COMMAND_DATA | |
3182 | @findex gdb.COMMAND_DATA | |
3183 | @item gdb.COMMAND_DATA | |
3184 | The command is related to data or variables. For example, | |
3185 | @code{call}, @code{find}, and @code{print} are in this category. Type | |
3186 | @kbd{help data} at the @value{GDBN} prompt to see a list of commands | |
3187 | in this category. | |
3188 | ||
3189 | @findex COMMAND_STACK | |
3190 | @findex gdb.COMMAND_STACK | |
3191 | @item gdb.COMMAND_STACK | |
3192 | The command has to do with manipulation of the stack. For example, | |
3193 | @code{backtrace}, @code{frame}, and @code{return} are in this | |
3194 | category. Type @kbd{help stack} at the @value{GDBN} prompt to see a | |
3195 | list of commands in this category. | |
3196 | ||
3197 | @findex COMMAND_FILES | |
3198 | @findex gdb.COMMAND_FILES | |
3199 | @item gdb.COMMAND_FILES | |
3200 | This class is used for file-related commands. For example, | |
3201 | @code{file}, @code{list} and @code{section} are in this category. | |
3202 | Type @kbd{help files} at the @value{GDBN} prompt to see a list of | |
3203 | commands in this category. | |
3204 | ||
3205 | @findex COMMAND_SUPPORT | |
3206 | @findex gdb.COMMAND_SUPPORT | |
3207 | @item gdb.COMMAND_SUPPORT | |
3208 | This should be used for ``support facilities'', generally meaning | |
3209 | things that are useful to the user when interacting with @value{GDBN}, | |
3210 | but not related to the state of the inferior. For example, | |
3211 | @code{help}, @code{make}, and @code{shell} are in this category. Type | |
3212 | @kbd{help support} at the @value{GDBN} prompt to see a list of | |
3213 | commands in this category. | |
3214 | ||
3215 | @findex COMMAND_STATUS | |
3216 | @findex gdb.COMMAND_STATUS | |
3217 | @item gdb.COMMAND_STATUS | |
3218 | The command is an @samp{info}-related command, that is, related to the | |
3219 | state of @value{GDBN} itself. For example, @code{info}, @code{macro}, | |
3220 | and @code{show} are in this category. Type @kbd{help status} at the | |
3221 | @value{GDBN} prompt to see a list of commands in this category. | |
3222 | ||
3223 | @findex COMMAND_BREAKPOINTS | |
3224 | @findex gdb.COMMAND_BREAKPOINTS | |
3225 | @item gdb.COMMAND_BREAKPOINTS | |
3226 | The command has to do with breakpoints. For example, @code{break}, | |
3227 | @code{clear}, and @code{delete} are in this category. Type @kbd{help | |
3228 | breakpoints} at the @value{GDBN} prompt to see a list of commands in | |
3229 | this category. | |
3230 | ||
3231 | @findex COMMAND_TRACEPOINTS | |
3232 | @findex gdb.COMMAND_TRACEPOINTS | |
3233 | @item gdb.COMMAND_TRACEPOINTS | |
3234 | The command has to do with tracepoints. For example, @code{trace}, | |
3235 | @code{actions}, and @code{tfind} are in this category. Type | |
3236 | @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of | |
3237 | commands in this category. | |
3238 | ||
3239 | @findex COMMAND_USER | |
3240 | @findex gdb.COMMAND_USER | |
3241 | @item gdb.COMMAND_USER | |
3242 | The command is a general purpose command for the user, and typically | |
3243 | does not fit in one of the other categories. | |
3244 | Type @kbd{help user-defined} at the @value{GDBN} prompt to see | |
3245 | a list of commands in this category, as well as the list of gdb macros | |
3246 | (@pxref{Sequences}). | |
3247 | ||
3248 | @findex COMMAND_OBSCURE | |
3249 | @findex gdb.COMMAND_OBSCURE | |
3250 | @item gdb.COMMAND_OBSCURE | |
3251 | The command is only used in unusual circumstances, or is not of | |
3252 | general interest to users. For example, @code{checkpoint}, | |
3253 | @code{fork}, and @code{stop} are in this category. Type @kbd{help | |
3254 | obscure} at the @value{GDBN} prompt to see a list of commands in this | |
3255 | category. | |
3256 | ||
3257 | @findex COMMAND_MAINTENANCE | |
3258 | @findex gdb.COMMAND_MAINTENANCE | |
3259 | @item gdb.COMMAND_MAINTENANCE | |
3260 | The command is only useful to @value{GDBN} maintainers. The | |
3261 | @code{maintenance} and @code{flushregs} commands are in this category. | |
3262 | Type @kbd{help internals} at the @value{GDBN} prompt to see a list of | |
3263 | commands in this category. | |
3264 | @end table | |
3265 | ||
3266 | A new command can use a predefined completion function, either by | |
3267 | specifying it via an argument at initialization, or by returning it | |
3268 | from the @code{complete} method. These predefined completion | |
3269 | constants are all defined in the @code{gdb} module: | |
3270 | ||
b3ce5e5f DE |
3271 | @vtable @code |
3272 | @vindex COMPLETE_NONE | |
329baa95 DE |
3273 | @item gdb.COMPLETE_NONE |
3274 | This constant means that no completion should be done. | |
3275 | ||
b3ce5e5f | 3276 | @vindex COMPLETE_FILENAME |
329baa95 DE |
3277 | @item gdb.COMPLETE_FILENAME |
3278 | This constant means that filename completion should be performed. | |
3279 | ||
b3ce5e5f | 3280 | @vindex COMPLETE_LOCATION |
329baa95 DE |
3281 | @item gdb.COMPLETE_LOCATION |
3282 | This constant means that location completion should be done. | |
3283 | @xref{Specify Location}. | |
3284 | ||
b3ce5e5f | 3285 | @vindex COMPLETE_COMMAND |
329baa95 DE |
3286 | @item gdb.COMPLETE_COMMAND |
3287 | This constant means that completion should examine @value{GDBN} | |
3288 | command names. | |
3289 | ||
b3ce5e5f | 3290 | @vindex COMPLETE_SYMBOL |
329baa95 DE |
3291 | @item gdb.COMPLETE_SYMBOL |
3292 | This constant means that completion should be done using symbol names | |
3293 | as the source. | |
3294 | ||
b3ce5e5f | 3295 | @vindex COMPLETE_EXPRESSION |
329baa95 DE |
3296 | @item gdb.COMPLETE_EXPRESSION |
3297 | This constant means that completion should be done on expressions. | |
3298 | Often this means completing on symbol names, but some language | |
3299 | parsers also have support for completing on field names. | |
b3ce5e5f | 3300 | @end vtable |
329baa95 DE |
3301 | |
3302 | The following code snippet shows how a trivial CLI command can be | |
3303 | implemented in Python: | |
3304 | ||
3305 | @smallexample | |
3306 | class HelloWorld (gdb.Command): | |
3307 | """Greet the whole world.""" | |
3308 | ||
3309 | def __init__ (self): | |
3310 | super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) | |
3311 | ||
3312 | def invoke (self, arg, from_tty): | |
3313 | print "Hello, World!" | |
3314 | ||
3315 | HelloWorld () | |
3316 | @end smallexample | |
3317 | ||
3318 | The last line instantiates the class, and is necessary to trigger the | |
3319 | registration of the command with @value{GDBN}. Depending on how the | |
3320 | Python code is read into @value{GDBN}, you may need to import the | |
3321 | @code{gdb} module explicitly. | |
3322 | ||
3323 | @node Parameters In Python | |
3324 | @subsubsection Parameters In Python | |
3325 | ||
3326 | @cindex parameters in python | |
3327 | @cindex python parameters | |
3328 | @tindex gdb.Parameter | |
3329 | @tindex Parameter | |
3330 | You can implement new @value{GDBN} parameters using Python. A new | |
3331 | parameter is implemented as an instance of the @code{gdb.Parameter} | |
3332 | class. | |
3333 | ||
3334 | Parameters are exposed to the user via the @code{set} and | |
3335 | @code{show} commands. @xref{Help}. | |
3336 | ||
3337 | There are many parameters that already exist and can be set in | |
3338 | @value{GDBN}. Two examples are: @code{set follow fork} and | |
3339 | @code{set charset}. Setting these parameters influences certain | |
3340 | behavior in @value{GDBN}. Similarly, you can define parameters that | |
3341 | can be used to influence behavior in custom Python scripts and commands. | |
3342 | ||
3343 | @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]}) | |
3344 | The object initializer for @code{Parameter} registers the new | |
3345 | parameter with @value{GDBN}. This initializer is normally invoked | |
3346 | from the subclass' own @code{__init__} method. | |
3347 | ||
3348 | @var{name} is the name of the new parameter. If @var{name} consists | |
3349 | of multiple words, then the initial words are looked for as prefix | |
3350 | parameters. An example of this can be illustrated with the | |
3351 | @code{set print} set of parameters. If @var{name} is | |
3352 | @code{print foo}, then @code{print} will be searched as the prefix | |
3353 | parameter. In this case the parameter can subsequently be accessed in | |
3354 | @value{GDBN} as @code{set print foo}. | |
3355 | ||
3356 | If @var{name} consists of multiple words, and no prefix parameter group | |
3357 | can be found, an exception is raised. | |
3358 | ||
3359 | @var{command-class} should be one of the @samp{COMMAND_} constants | |
3360 | (@pxref{Commands In Python}). This argument tells @value{GDBN} how to | |
3361 | categorize the new parameter in the help system. | |
3362 | ||
3363 | @var{parameter-class} should be one of the @samp{PARAM_} constants | |
3364 | defined below. This argument tells @value{GDBN} the type of the new | |
3365 | parameter; this information is used for input validation and | |
3366 | completion. | |
3367 | ||
3368 | If @var{parameter-class} is @code{PARAM_ENUM}, then | |
3369 | @var{enum-sequence} must be a sequence of strings. These strings | |
3370 | represent the possible values for the parameter. | |
3371 | ||
3372 | If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence | |
3373 | of a fourth argument will cause an exception to be thrown. | |
3374 | ||
3375 | The help text for the new parameter is taken from the Python | |
3376 | documentation string for the parameter's class, if there is one. If | |
3377 | there is no documentation string, a default value is used. | |
3378 | @end defun | |
3379 | ||
3380 | @defvar Parameter.set_doc | |
3381 | If this attribute exists, and is a string, then its value is used as | |
3382 | the help text for this parameter's @code{set} command. The value is | |
3383 | examined when @code{Parameter.__init__} is invoked; subsequent changes | |
3384 | have no effect. | |
3385 | @end defvar | |
3386 | ||
3387 | @defvar Parameter.show_doc | |
3388 | If this attribute exists, and is a string, then its value is used as | |
3389 | the help text for this parameter's @code{show} command. The value is | |
3390 | examined when @code{Parameter.__init__} is invoked; subsequent changes | |
3391 | have no effect. | |
3392 | @end defvar | |
3393 | ||
3394 | @defvar Parameter.value | |
3395 | The @code{value} attribute holds the underlying value of the | |
3396 | parameter. It can be read and assigned to just as any other | |
3397 | attribute. @value{GDBN} does validation when assignments are made. | |
3398 | @end defvar | |
3399 | ||
3400 | There are two methods that should be implemented in any | |
3401 | @code{Parameter} class. These are: | |
3402 | ||
3403 | @defun Parameter.get_set_string (self) | |
3404 | @value{GDBN} will call this method when a @var{parameter}'s value has | |
3405 | been changed via the @code{set} API (for example, @kbd{set foo off}). | |
3406 | The @code{value} attribute has already been populated with the new | |
3407 | value and may be used in output. This method must return a string. | |
3408 | @end defun | |
3409 | ||
3410 | @defun Parameter.get_show_string (self, svalue) | |
3411 | @value{GDBN} will call this method when a @var{parameter}'s | |
3412 | @code{show} API has been invoked (for example, @kbd{show foo}). The | |
3413 | argument @code{svalue} receives the string representation of the | |
3414 | current value. This method must return a string. | |
3415 | @end defun | |
3416 | ||
3417 | When a new parameter is defined, its type must be specified. The | |
3418 | available types are represented by constants defined in the @code{gdb} | |
3419 | module: | |
3420 | ||
3421 | @table @code | |
3422 | @findex PARAM_BOOLEAN | |
3423 | @findex gdb.PARAM_BOOLEAN | |
3424 | @item gdb.PARAM_BOOLEAN | |
3425 | The value is a plain boolean. The Python boolean values, @code{True} | |
3426 | and @code{False} are the only valid values. | |
3427 | ||
3428 | @findex PARAM_AUTO_BOOLEAN | |
3429 | @findex gdb.PARAM_AUTO_BOOLEAN | |
3430 | @item gdb.PARAM_AUTO_BOOLEAN | |
3431 | The value has three possible states: true, false, and @samp{auto}. In | |
3432 | Python, true and false are represented using boolean constants, and | |
3433 | @samp{auto} is represented using @code{None}. | |
3434 | ||
3435 | @findex PARAM_UINTEGER | |
3436 | @findex gdb.PARAM_UINTEGER | |
3437 | @item gdb.PARAM_UINTEGER | |
3438 | The value is an unsigned integer. The value of 0 should be | |
3439 | interpreted to mean ``unlimited''. | |
3440 | ||
3441 | @findex PARAM_INTEGER | |
3442 | @findex gdb.PARAM_INTEGER | |
3443 | @item gdb.PARAM_INTEGER | |
3444 | The value is a signed integer. The value of 0 should be interpreted | |
3445 | to mean ``unlimited''. | |
3446 | ||
3447 | @findex PARAM_STRING | |
3448 | @findex gdb.PARAM_STRING | |
3449 | @item gdb.PARAM_STRING | |
3450 | The value is a string. When the user modifies the string, any escape | |
3451 | sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are | |
3452 | translated into corresponding characters and encoded into the current | |
3453 | host charset. | |
3454 | ||
3455 | @findex PARAM_STRING_NOESCAPE | |
3456 | @findex gdb.PARAM_STRING_NOESCAPE | |
3457 | @item gdb.PARAM_STRING_NOESCAPE | |
3458 | The value is a string. When the user modifies the string, escapes are | |
3459 | passed through untranslated. | |
3460 | ||
3461 | @findex PARAM_OPTIONAL_FILENAME | |
3462 | @findex gdb.PARAM_OPTIONAL_FILENAME | |
3463 | @item gdb.PARAM_OPTIONAL_FILENAME | |
3464 | The value is a either a filename (a string), or @code{None}. | |
3465 | ||
3466 | @findex PARAM_FILENAME | |
3467 | @findex gdb.PARAM_FILENAME | |
3468 | @item gdb.PARAM_FILENAME | |
3469 | The value is a filename. This is just like | |
3470 | @code{PARAM_STRING_NOESCAPE}, but uses file names for completion. | |
3471 | ||
3472 | @findex PARAM_ZINTEGER | |
3473 | @findex gdb.PARAM_ZINTEGER | |
3474 | @item gdb.PARAM_ZINTEGER | |
3475 | The value is an integer. This is like @code{PARAM_INTEGER}, except 0 | |
3476 | is interpreted as itself. | |
3477 | ||
3478 | @findex PARAM_ENUM | |
3479 | @findex gdb.PARAM_ENUM | |
3480 | @item gdb.PARAM_ENUM | |
3481 | The value is a string, which must be one of a collection string | |
3482 | constants provided when the parameter is created. | |
3483 | @end table | |
3484 | ||
3485 | @node Functions In Python | |
3486 | @subsubsection Writing new convenience functions | |
3487 | ||
3488 | @cindex writing convenience functions | |
3489 | @cindex convenience functions in python | |
3490 | @cindex python convenience functions | |
3491 | @tindex gdb.Function | |
3492 | @tindex Function | |
3493 | You can implement new convenience functions (@pxref{Convenience Vars}) | |
3494 | in Python. A convenience function is an instance of a subclass of the | |
3495 | class @code{gdb.Function}. | |
3496 | ||
3497 | @defun Function.__init__ (name) | |
3498 | The initializer for @code{Function} registers the new function with | |
3499 | @value{GDBN}. The argument @var{name} is the name of the function, | |
3500 | a string. The function will be visible to the user as a convenience | |
3501 | variable of type @code{internal function}, whose name is the same as | |
3502 | the given @var{name}. | |
3503 | ||
3504 | The documentation for the new function is taken from the documentation | |
3505 | string for the new class. | |
3506 | @end defun | |
3507 | ||
3508 | @defun Function.invoke (@var{*args}) | |
3509 | When a convenience function is evaluated, its arguments are converted | |
3510 | to instances of @code{gdb.Value}, and then the function's | |
3511 | @code{invoke} method is called. Note that @value{GDBN} does not | |
3512 | predetermine the arity of convenience functions. Instead, all | |
3513 | available arguments are passed to @code{invoke}, following the | |
3514 | standard Python calling convention. In particular, a convenience | |
3515 | function can have default values for parameters without ill effect. | |
3516 | ||
3517 | The return value of this method is used as its value in the enclosing | |
3518 | expression. If an ordinary Python value is returned, it is converted | |
3519 | to a @code{gdb.Value} following the usual rules. | |
3520 | @end defun | |
3521 | ||
3522 | The following code snippet shows how a trivial convenience function can | |
3523 | be implemented in Python: | |
3524 | ||
3525 | @smallexample | |
3526 | class Greet (gdb.Function): | |
3527 | """Return string to greet someone. | |
3528 | Takes a name as argument.""" | |
3529 | ||
3530 | def __init__ (self): | |
3531 | super (Greet, self).__init__ ("greet") | |
3532 | ||
3533 | def invoke (self, name): | |
3534 | return "Hello, %s!" % name.string () | |
3535 | ||
3536 | Greet () | |
3537 | @end smallexample | |
3538 | ||
3539 | The last line instantiates the class, and is necessary to trigger the | |
3540 | registration of the function with @value{GDBN}. Depending on how the | |
3541 | Python code is read into @value{GDBN}, you may need to import the | |
3542 | @code{gdb} module explicitly. | |
3543 | ||
3544 | Now you can use the function in an expression: | |
3545 | ||
3546 | @smallexample | |
3547 | (gdb) print $greet("Bob") | |
3548 | $1 = "Hello, Bob!" | |
3549 | @end smallexample | |
3550 | ||
3551 | @node Progspaces In Python | |
3552 | @subsubsection Program Spaces In Python | |
3553 | ||
3554 | @cindex progspaces in python | |
3555 | @tindex gdb.Progspace | |
3556 | @tindex Progspace | |
3557 | A program space, or @dfn{progspace}, represents a symbolic view | |
3558 | of an address space. | |
3559 | It consists of all of the objfiles of the program. | |
3560 | @xref{Objfiles In Python}. | |
3561 | @xref{Inferiors and Programs, program spaces}, for more details | |
3562 | about program spaces. | |
3563 | ||
3564 | The following progspace-related functions are available in the | |
3565 | @code{gdb} module: | |
3566 | ||
3567 | @findex gdb.current_progspace | |
3568 | @defun gdb.current_progspace () | |
3569 | This function returns the program space of the currently selected inferior. | |
3570 | @xref{Inferiors and Programs}. | |
3571 | @end defun | |
3572 | ||
3573 | @findex gdb.progspaces | |
3574 | @defun gdb.progspaces () | |
3575 | Return a sequence of all the progspaces currently known to @value{GDBN}. | |
3576 | @end defun | |
3577 | ||
3578 | Each progspace is represented by an instance of the @code{gdb.Progspace} | |
3579 | class. | |
3580 | ||
3581 | @defvar Progspace.filename | |
3582 | The file name of the progspace as a string. | |
3583 | @end defvar | |
3584 | ||
3585 | @defvar Progspace.pretty_printers | |
3586 | The @code{pretty_printers} attribute is a list of functions. It is | |
3587 | used to look up pretty-printers. A @code{Value} is passed to each | |
3588 | function in order; if the function returns @code{None}, then the | |
3589 | search continues. Otherwise, the return value should be an object | |
3590 | which is used to format the value. @xref{Pretty Printing API}, for more | |
3591 | information. | |
3592 | @end defvar | |
3593 | ||
3594 | @defvar Progspace.type_printers | |
3595 | The @code{type_printers} attribute is a list of type printer objects. | |
3596 | @xref{Type Printing API}, for more information. | |
3597 | @end defvar | |
3598 | ||
3599 | @defvar Progspace.frame_filters | |
3600 | The @code{frame_filters} attribute is a dictionary of frame filter | |
3601 | objects. @xref{Frame Filter API}, for more information. | |
3602 | @end defvar | |
3603 | ||
02be9a71 DE |
3604 | One may add arbitrary attributes to @code{gdb.Progspace} objects |
3605 | in the usual Python way. | |
3606 | This is useful if, for example, one needs to do some extra record keeping | |
3607 | associated with the program space. | |
3608 | ||
3609 | In this contrived example, we want to perform some processing when | |
3610 | an objfile with a certain symbol is loaded, but we only want to do | |
3611 | this once because it is expensive. To achieve this we record the results | |
3612 | with the program space because we can't predict when the desired objfile | |
3613 | will be loaded. | |
3614 | ||
3615 | @smallexample | |
3616 | (gdb) python | |
3617 | def clear_objfiles_handler(event): | |
3618 | event.progspace.expensive_computation = None | |
3619 | def expensive(symbol): | |
3620 | """A mock routine to perform an "expensive" computation on symbol.""" | |
3621 | print "Computing the answer to the ultimate question ..." | |
3622 | return 42 | |
3623 | def new_objfile_handler(event): | |
3624 | objfile = event.new_objfile | |
3625 | progspace = objfile.progspace | |
3626 | if not hasattr(progspace, 'expensive_computation') or \ | |
3627 | progspace.expensive_computation is None: | |
3628 | # We use 'main' for the symbol to keep the example simple. | |
3629 | # Note: There's no current way to constrain the lookup | |
3630 | # to one objfile. | |
3631 | symbol = gdb.lookup_global_symbol('main') | |
3632 | if symbol is not None: | |
3633 | progspace.expensive_computation = expensive(symbol) | |
3634 | gdb.events.clear_objfiles.connect(clear_objfiles_handler) | |
3635 | gdb.events.new_objfile.connect(new_objfile_handler) | |
3636 | end | |
3637 | (gdb) file /tmp/hello | |
3638 | Reading symbols from /tmp/hello...done. | |
3639 | Computing the answer to the ultimate question ... | |
3640 | (gdb) python print gdb.current_progspace().expensive_computation | |
3641 | 42 | |
3642 | (gdb) run | |
3643 | Starting program: /tmp/hello | |
3644 | Hello. | |
3645 | [Inferior 1 (process 4242) exited normally] | |
3646 | @end smallexample | |
3647 | ||
329baa95 DE |
3648 | @node Objfiles In Python |
3649 | @subsubsection Objfiles In Python | |
3650 | ||
3651 | @cindex objfiles in python | |
3652 | @tindex gdb.Objfile | |
3653 | @tindex Objfile | |
3654 | @value{GDBN} loads symbols for an inferior from various | |
3655 | symbol-containing files (@pxref{Files}). These include the primary | |
3656 | executable file, any shared libraries used by the inferior, and any | |
3657 | separate debug info files (@pxref{Separate Debug Files}). | |
3658 | @value{GDBN} calls these symbol-containing files @dfn{objfiles}. | |
3659 | ||
3660 | The following objfile-related functions are available in the | |
3661 | @code{gdb} module: | |
3662 | ||
3663 | @findex gdb.current_objfile | |
3664 | @defun gdb.current_objfile () | |
3665 | When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN} | |
3666 | sets the ``current objfile'' to the corresponding objfile. This | |
3667 | function returns the current objfile. If there is no current objfile, | |
3668 | this function returns @code{None}. | |
3669 | @end defun | |
3670 | ||
3671 | @findex gdb.objfiles | |
3672 | @defun gdb.objfiles () | |
3673 | Return a sequence of all the objfiles current known to @value{GDBN}. | |
3674 | @xref{Objfiles In Python}. | |
3675 | @end defun | |
3676 | ||
6dddd6a5 DE |
3677 | @findex gdb.lookup_objfile |
3678 | @defun gdb.lookup_objfile (name @r{[}, by_build_id{]}) | |
3679 | Look up @var{name}, a file name or build ID, in the list of objfiles | |
3680 | for the current program space (@pxref{Progspaces In Python}). | |
3681 | If the objfile is not found throw the Python @code{ValueError} exception. | |
3682 | ||
3683 | If @var{name} is a relative file name, then it will match any | |
3684 | source file name with the same trailing components. For example, if | |
3685 | @var{name} is @samp{gcc/expr.c}, then it will match source file | |
3686 | name of @file{/build/trunk/gcc/expr.c}, but not | |
3687 | @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}. | |
3688 | ||
3689 | If @var{by_build_id} is provided and is @code{True} then @var{name} | |
3690 | is the build ID of the objfile. Otherwise, @var{name} is a file name. | |
3691 | This is supported only on some operating systems, notably those which use | |
3692 | the ELF format for binary files and the @sc{gnu} Binutils. For more details | |
3693 | about this feature, see the description of the @option{--build-id} | |
3694 | command-line option in @ref{Options, , Command Line Options, ld.info, | |
3695 | The GNU Linker}. | |
3696 | @end defun | |
3697 | ||
329baa95 DE |
3698 | Each objfile is represented by an instance of the @code{gdb.Objfile} |
3699 | class. | |
3700 | ||
3701 | @defvar Objfile.filename | |
1b549396 DE |
3702 | The file name of the objfile as a string, with symbolic links resolved. |
3703 | ||
3704 | The value is @code{None} if the objfile is no longer valid. | |
3705 | See the @code{gdb.Objfile.is_valid} method, described below. | |
329baa95 DE |
3706 | @end defvar |
3707 | ||
3a8b707a DE |
3708 | @defvar Objfile.username |
3709 | The file name of the objfile as specified by the user as a string. | |
3710 | ||
3711 | The value is @code{None} if the objfile is no longer valid. | |
3712 | See the @code{gdb.Objfile.is_valid} method, described below. | |
3713 | @end defvar | |
3714 | ||
a0be3e44 DE |
3715 | @defvar Objfile.owner |
3716 | For separate debug info objfiles this is the corresponding @code{gdb.Objfile} | |
3717 | object that debug info is being provided for. | |
3718 | Otherwise this is @code{None}. | |
3719 | Separate debug info objfiles are added with the | |
3720 | @code{gdb.Objfile.add_separate_debug_file} method, described below. | |
3721 | @end defvar | |
3722 | ||
7c50a931 DE |
3723 | @defvar Objfile.build_id |
3724 | The build ID of the objfile as a string. | |
3725 | If the objfile does not have a build ID then the value is @code{None}. | |
3726 | ||
3727 | This is supported only on some operating systems, notably those which use | |
3728 | the ELF format for binary files and the @sc{gnu} Binutils. For more details | |
3729 | about this feature, see the description of the @option{--build-id} | |
3730 | command-line option in @ref{Options, , Command Line Options, ld.info, | |
3731 | The GNU Linker}. | |
3732 | @end defvar | |
3733 | ||
d096d8c1 DE |
3734 | @defvar Objfile.progspace |
3735 | The containing program space of the objfile as a @code{gdb.Progspace} | |
3736 | object. @xref{Progspaces In Python}. | |
3737 | @end defvar | |
3738 | ||
329baa95 DE |
3739 | @defvar Objfile.pretty_printers |
3740 | The @code{pretty_printers} attribute is a list of functions. It is | |
3741 | used to look up pretty-printers. A @code{Value} is passed to each | |
3742 | function in order; if the function returns @code{None}, then the | |
3743 | search continues. Otherwise, the return value should be an object | |
3744 | which is used to format the value. @xref{Pretty Printing API}, for more | |
3745 | information. | |
3746 | @end defvar | |
3747 | ||
3748 | @defvar Objfile.type_printers | |
3749 | The @code{type_printers} attribute is a list of type printer objects. | |
3750 | @xref{Type Printing API}, for more information. | |
3751 | @end defvar | |
3752 | ||
3753 | @defvar Objfile.frame_filters | |
3754 | The @code{frame_filters} attribute is a dictionary of frame filter | |
3755 | objects. @xref{Frame Filter API}, for more information. | |
3756 | @end defvar | |
3757 | ||
02be9a71 DE |
3758 | One may add arbitrary attributes to @code{gdb.Objfile} objects |
3759 | in the usual Python way. | |
3760 | This is useful if, for example, one needs to do some extra record keeping | |
3761 | associated with the objfile. | |
3762 | ||
3763 | In this contrived example we record the time when @value{GDBN} | |
3764 | loaded the objfile. | |
3765 | ||
3766 | @smallexample | |
3767 | (gdb) python | |
3768 | import datetime | |
3769 | def new_objfile_handler(event): | |
3770 | # Set the time_loaded attribute of the new objfile. | |
3771 | event.new_objfile.time_loaded = datetime.datetime.today() | |
3772 | gdb.events.new_objfile.connect(new_objfile_handler) | |
3773 | end | |
3774 | (gdb) file ./hello | |
3775 | Reading symbols from ./hello...done. | |
3776 | (gdb) python print gdb.objfiles()[0].time_loaded | |
3777 | 2014-10-09 11:41:36.770345 | |
3778 | @end smallexample | |
3779 | ||
329baa95 DE |
3780 | A @code{gdb.Objfile} object has the following methods: |
3781 | ||
3782 | @defun Objfile.is_valid () | |
3783 | Returns @code{True} if the @code{gdb.Objfile} object is valid, | |
3784 | @code{False} if not. A @code{gdb.Objfile} object can become invalid | |
3785 | if the object file it refers to is not loaded in @value{GDBN} any | |
3786 | longer. All other @code{gdb.Objfile} methods will throw an exception | |
3787 | if it is invalid at the time the method is called. | |
3788 | @end defun | |
3789 | ||
86e4ed39 DE |
3790 | @defun Objfile.add_separate_debug_file (file) |
3791 | Add @var{file} to the list of files that @value{GDBN} will search for | |
3792 | debug information for the objfile. | |
3793 | This is useful when the debug info has been removed from the program | |
3794 | and stored in a separate file. @value{GDBN} has built-in support for | |
3795 | finding separate debug info files (@pxref{Separate Debug Files}), but if | |
3796 | the file doesn't live in one of the standard places that @value{GDBN} | |
3797 | searches then this function can be used to add a debug info file | |
3798 | from a different place. | |
3799 | @end defun | |
3800 | ||
329baa95 DE |
3801 | @node Frames In Python |
3802 | @subsubsection Accessing inferior stack frames from Python. | |
3803 | ||
3804 | @cindex frames in python | |
3805 | When the debugged program stops, @value{GDBN} is able to analyze its call | |
3806 | stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class | |
3807 | represents a frame in the stack. A @code{gdb.Frame} object is only valid | |
3808 | while its corresponding frame exists in the inferior's stack. If you try | |
3809 | to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error} | |
3810 | exception (@pxref{Exception Handling}). | |
3811 | ||
3812 | Two @code{gdb.Frame} objects can be compared for equality with the @code{==} | |
3813 | operator, like: | |
3814 | ||
3815 | @smallexample | |
3816 | (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame () | |
3817 | True | |
3818 | @end smallexample | |
3819 | ||
3820 | The following frame-related functions are available in the @code{gdb} module: | |
3821 | ||
3822 | @findex gdb.selected_frame | |
3823 | @defun gdb.selected_frame () | |
3824 | Return the selected frame object. (@pxref{Selection,,Selecting a Frame}). | |
3825 | @end defun | |
3826 | ||
3827 | @findex gdb.newest_frame | |
3828 | @defun gdb.newest_frame () | |
3829 | Return the newest frame object for the selected thread. | |
3830 | @end defun | |
3831 | ||
3832 | @defun gdb.frame_stop_reason_string (reason) | |
3833 | Return a string explaining the reason why @value{GDBN} stopped unwinding | |
3834 | frames, as expressed by the given @var{reason} code (an integer, see the | |
3835 | @code{unwind_stop_reason} method further down in this section). | |
3836 | @end defun | |
3837 | ||
3838 | A @code{gdb.Frame} object has the following methods: | |
3839 | ||
3840 | @defun Frame.is_valid () | |
3841 | Returns true if the @code{gdb.Frame} object is valid, false if not. | |
3842 | A frame object can become invalid if the frame it refers to doesn't | |
3843 | exist anymore in the inferior. All @code{gdb.Frame} methods will throw | |
3844 | an exception if it is invalid at the time the method is called. | |
3845 | @end defun | |
3846 | ||
3847 | @defun Frame.name () | |
3848 | Returns the function name of the frame, or @code{None} if it can't be | |
3849 | obtained. | |
3850 | @end defun | |
3851 | ||
3852 | @defun Frame.architecture () | |
3853 | Returns the @code{gdb.Architecture} object corresponding to the frame's | |
3854 | architecture. @xref{Architectures In Python}. | |
3855 | @end defun | |
3856 | ||
3857 | @defun Frame.type () | |
3858 | Returns the type of the frame. The value can be one of: | |
3859 | @table @code | |
3860 | @item gdb.NORMAL_FRAME | |
3861 | An ordinary stack frame. | |
3862 | ||
3863 | @item gdb.DUMMY_FRAME | |
3864 | A fake stack frame that was created by @value{GDBN} when performing an | |
3865 | inferior function call. | |
3866 | ||
3867 | @item gdb.INLINE_FRAME | |
3868 | A frame representing an inlined function. The function was inlined | |
3869 | into a @code{gdb.NORMAL_FRAME} that is older than this one. | |
3870 | ||
3871 | @item gdb.TAILCALL_FRAME | |
3872 | A frame representing a tail call. @xref{Tail Call Frames}. | |
3873 | ||
3874 | @item gdb.SIGTRAMP_FRAME | |
3875 | A signal trampoline frame. This is the frame created by the OS when | |
3876 | it calls into a signal handler. | |
3877 | ||
3878 | @item gdb.ARCH_FRAME | |
3879 | A fake stack frame representing a cross-architecture call. | |
3880 | ||
3881 | @item gdb.SENTINEL_FRAME | |
3882 | This is like @code{gdb.NORMAL_FRAME}, but it is only used for the | |
3883 | newest frame. | |
3884 | @end table | |
3885 | @end defun | |
3886 | ||
3887 | @defun Frame.unwind_stop_reason () | |
3888 | Return an integer representing the reason why it's not possible to find | |
3889 | more frames toward the outermost frame. Use | |
3890 | @code{gdb.frame_stop_reason_string} to convert the value returned by this | |
3891 | function to a string. The value can be one of: | |
3892 | ||
3893 | @table @code | |
3894 | @item gdb.FRAME_UNWIND_NO_REASON | |
3895 | No particular reason (older frames should be available). | |
3896 | ||
3897 | @item gdb.FRAME_UNWIND_NULL_ID | |
3898 | The previous frame's analyzer returns an invalid result. This is no | |
3899 | longer used by @value{GDBN}, and is kept only for backward | |
3900 | compatibility. | |
3901 | ||
3902 | @item gdb.FRAME_UNWIND_OUTERMOST | |
3903 | This frame is the outermost. | |
3904 | ||
3905 | @item gdb.FRAME_UNWIND_UNAVAILABLE | |
3906 | Cannot unwind further, because that would require knowing the | |
3907 | values of registers or memory that have not been collected. | |
3908 | ||
3909 | @item gdb.FRAME_UNWIND_INNER_ID | |
3910 | This frame ID looks like it ought to belong to a NEXT frame, | |
3911 | but we got it for a PREV frame. Normally, this is a sign of | |
3912 | unwinder failure. It could also indicate stack corruption. | |
3913 | ||
3914 | @item gdb.FRAME_UNWIND_SAME_ID | |
3915 | This frame has the same ID as the previous one. That means | |
3916 | that unwinding further would almost certainly give us another | |
3917 | frame with exactly the same ID, so break the chain. Normally, | |
3918 | this is a sign of unwinder failure. It could also indicate | |
3919 | stack corruption. | |
3920 | ||
3921 | @item gdb.FRAME_UNWIND_NO_SAVED_PC | |
3922 | The frame unwinder did not find any saved PC, but we needed | |
3923 | one to unwind further. | |
3924 | ||
53e8a631 AB |
3925 | @item gdb.FRAME_UNWIND_MEMORY_ERROR |
3926 | The frame unwinder caused an error while trying to access memory. | |
3927 | ||
329baa95 DE |
3928 | @item gdb.FRAME_UNWIND_FIRST_ERROR |
3929 | Any stop reason greater or equal to this value indicates some kind | |
3930 | of error. This special value facilitates writing code that tests | |
3931 | for errors in unwinding in a way that will work correctly even if | |
3932 | the list of the other values is modified in future @value{GDBN} | |
3933 | versions. Using it, you could write: | |
3934 | @smallexample | |
3935 | reason = gdb.selected_frame().unwind_stop_reason () | |
3936 | reason_str = gdb.frame_stop_reason_string (reason) | |
3937 | if reason >= gdb.FRAME_UNWIND_FIRST_ERROR: | |
3938 | print "An error occured: %s" % reason_str | |
3939 | @end smallexample | |
3940 | @end table | |
3941 | ||
3942 | @end defun | |
3943 | ||
3944 | @defun Frame.pc () | |
3945 | Returns the frame's resume address. | |
3946 | @end defun | |
3947 | ||
3948 | @defun Frame.block () | |
3949 | Return the frame's code block. @xref{Blocks In Python}. | |
3950 | @end defun | |
3951 | ||
3952 | @defun Frame.function () | |
3953 | Return the symbol for the function corresponding to this frame. | |
3954 | @xref{Symbols In Python}. | |
3955 | @end defun | |
3956 | ||
3957 | @defun Frame.older () | |
3958 | Return the frame that called this frame. | |
3959 | @end defun | |
3960 | ||
3961 | @defun Frame.newer () | |
3962 | Return the frame called by this frame. | |
3963 | @end defun | |
3964 | ||
3965 | @defun Frame.find_sal () | |
3966 | Return the frame's symtab and line object. | |
3967 | @xref{Symbol Tables In Python}. | |
3968 | @end defun | |
3969 | ||
5f3b99cf SS |
3970 | @defun Frame.read_register (register) |
3971 | Return the value of @var{register} in this frame. The @var{register} | |
3972 | argument must be a string (e.g., @code{'sp'} or @code{'rax'}). | |
3973 | Returns a @code{Gdb.Value} object. Throws an exception if @var{register} | |
3974 | does not exist. | |
3975 | @end defun | |
3976 | ||
329baa95 DE |
3977 | @defun Frame.read_var (variable @r{[}, block@r{]}) |
3978 | Return the value of @var{variable} in this frame. If the optional | |
3979 | argument @var{block} is provided, search for the variable from that | |
3980 | block; otherwise start at the frame's current block (which is | |
697aa1b7 EZ |
3981 | determined by the frame's current program counter). The @var{variable} |
3982 | argument must be a string or a @code{gdb.Symbol} object; @var{block} must be a | |
329baa95 DE |
3983 | @code{gdb.Block} object. |
3984 | @end defun | |
3985 | ||
3986 | @defun Frame.select () | |
3987 | Set this frame to be the selected frame. @xref{Stack, ,Examining the | |
3988 | Stack}. | |
3989 | @end defun | |
3990 | ||
3991 | @node Blocks In Python | |
3992 | @subsubsection Accessing blocks from Python. | |
3993 | ||
3994 | @cindex blocks in python | |
3995 | @tindex gdb.Block | |
3996 | ||
3997 | In @value{GDBN}, symbols are stored in blocks. A block corresponds | |
3998 | roughly to a scope in the source code. Blocks are organized | |
3999 | hierarchically, and are represented individually in Python as a | |
4000 | @code{gdb.Block}. Blocks rely on debugging information being | |
4001 | available. | |
4002 | ||
4003 | A frame has a block. Please see @ref{Frames In Python}, for a more | |
4004 | in-depth discussion of frames. | |
4005 | ||
4006 | The outermost block is known as the @dfn{global block}. The global | |
4007 | block typically holds public global variables and functions. | |
4008 | ||
4009 | The block nested just inside the global block is the @dfn{static | |
4010 | block}. The static block typically holds file-scoped variables and | |
4011 | functions. | |
4012 | ||
4013 | @value{GDBN} provides a method to get a block's superblock, but there | |
4014 | is currently no way to examine the sub-blocks of a block, or to | |
4015 | iterate over all the blocks in a symbol table (@pxref{Symbol Tables In | |
4016 | Python}). | |
4017 | ||
4018 | Here is a short example that should help explain blocks: | |
4019 | ||
4020 | @smallexample | |
4021 | /* This is in the global block. */ | |
4022 | int global; | |
4023 | ||
4024 | /* This is in the static block. */ | |
4025 | static int file_scope; | |
4026 | ||
4027 | /* 'function' is in the global block, and 'argument' is | |
4028 | in a block nested inside of 'function'. */ | |
4029 | int function (int argument) | |
4030 | @{ | |
4031 | /* 'local' is in a block inside 'function'. It may or may | |
4032 | not be in the same block as 'argument'. */ | |
4033 | int local; | |
4034 | ||
4035 | @{ | |
4036 | /* 'inner' is in a block whose superblock is the one holding | |
4037 | 'local'. */ | |
4038 | int inner; | |
4039 | ||
4040 | /* If this call is expanded by the compiler, you may see | |
4041 | a nested block here whose function is 'inline_function' | |
4042 | and whose superblock is the one holding 'inner'. */ | |
4043 | inline_function (); | |
4044 | @} | |
4045 | @} | |
4046 | @end smallexample | |
4047 | ||
4048 | A @code{gdb.Block} is iterable. The iterator returns the symbols | |
4049 | (@pxref{Symbols In Python}) local to the block. Python programs | |
4050 | should not assume that a specific block object will always contain a | |
4051 | given symbol, since changes in @value{GDBN} features and | |
4052 | infrastructure may cause symbols move across blocks in a symbol | |
4053 | table. | |
4054 | ||
4055 | The following block-related functions are available in the @code{gdb} | |
4056 | module: | |
4057 | ||
4058 | @findex gdb.block_for_pc | |
4059 | @defun gdb.block_for_pc (pc) | |
4060 | Return the innermost @code{gdb.Block} containing the given @var{pc} | |
4061 | value. If the block cannot be found for the @var{pc} value specified, | |
4062 | the function will return @code{None}. | |
4063 | @end defun | |
4064 | ||
4065 | A @code{gdb.Block} object has the following methods: | |
4066 | ||
4067 | @defun Block.is_valid () | |
4068 | Returns @code{True} if the @code{gdb.Block} object is valid, | |
4069 | @code{False} if not. A block object can become invalid if the block it | |
4070 | refers to doesn't exist anymore in the inferior. All other | |
4071 | @code{gdb.Block} methods will throw an exception if it is invalid at | |
4072 | the time the method is called. The block's validity is also checked | |
4073 | during iteration over symbols of the block. | |
4074 | @end defun | |
4075 | ||
4076 | A @code{gdb.Block} object has the following attributes: | |
4077 | ||
4078 | @defvar Block.start | |
4079 | The start address of the block. This attribute is not writable. | |
4080 | @end defvar | |
4081 | ||
4082 | @defvar Block.end | |
4083 | The end address of the block. This attribute is not writable. | |
4084 | @end defvar | |
4085 | ||
4086 | @defvar Block.function | |
4087 | The name of the block represented as a @code{gdb.Symbol}. If the | |
4088 | block is not named, then this attribute holds @code{None}. This | |
4089 | attribute is not writable. | |
4090 | ||
4091 | For ordinary function blocks, the superblock is the static block. | |
4092 | However, you should note that it is possible for a function block to | |
4093 | have a superblock that is not the static block -- for instance this | |
4094 | happens for an inlined function. | |
4095 | @end defvar | |
4096 | ||
4097 | @defvar Block.superblock | |
4098 | The block containing this block. If this parent block does not exist, | |
4099 | this attribute holds @code{None}. This attribute is not writable. | |
4100 | @end defvar | |
4101 | ||
4102 | @defvar Block.global_block | |
4103 | The global block associated with this block. This attribute is not | |
4104 | writable. | |
4105 | @end defvar | |
4106 | ||
4107 | @defvar Block.static_block | |
4108 | The static block associated with this block. This attribute is not | |
4109 | writable. | |
4110 | @end defvar | |
4111 | ||
4112 | @defvar Block.is_global | |
4113 | @code{True} if the @code{gdb.Block} object is a global block, | |
4114 | @code{False} if not. This attribute is not | |
4115 | writable. | |
4116 | @end defvar | |
4117 | ||
4118 | @defvar Block.is_static | |
4119 | @code{True} if the @code{gdb.Block} object is a static block, | |
4120 | @code{False} if not. This attribute is not writable. | |
4121 | @end defvar | |
4122 | ||
4123 | @node Symbols In Python | |
4124 | @subsubsection Python representation of Symbols. | |
4125 | ||
4126 | @cindex symbols in python | |
4127 | @tindex gdb.Symbol | |
4128 | ||
4129 | @value{GDBN} represents every variable, function and type as an | |
4130 | entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}. | |
4131 | Similarly, Python represents these symbols in @value{GDBN} with the | |
4132 | @code{gdb.Symbol} object. | |
4133 | ||
4134 | The following symbol-related functions are available in the @code{gdb} | |
4135 | module: | |
4136 | ||
4137 | @findex gdb.lookup_symbol | |
4138 | @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]}) | |
4139 | This function searches for a symbol by name. The search scope can be | |
4140 | restricted to the parameters defined in the optional domain and block | |
4141 | arguments. | |
4142 | ||
4143 | @var{name} is the name of the symbol. It must be a string. The | |
4144 | optional @var{block} argument restricts the search to symbols visible | |
4145 | in that @var{block}. The @var{block} argument must be a | |
4146 | @code{gdb.Block} object. If omitted, the block for the current frame | |
4147 | is used. The optional @var{domain} argument restricts | |
4148 | the search to the domain type. The @var{domain} argument must be a | |
4149 | domain constant defined in the @code{gdb} module and described later | |
4150 | in this chapter. | |
4151 | ||
4152 | The result is a tuple of two elements. | |
4153 | The first element is a @code{gdb.Symbol} object or @code{None} if the symbol | |
4154 | is not found. | |
4155 | If the symbol is found, the second element is @code{True} if the symbol | |
4156 | is a field of a method's object (e.g., @code{this} in C@t{++}), | |
4157 | otherwise it is @code{False}. | |
4158 | If the symbol is not found, the second element is @code{False}. | |
4159 | @end defun | |
4160 | ||
4161 | @findex gdb.lookup_global_symbol | |
4162 | @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]}) | |
4163 | This function searches for a global symbol by name. | |
4164 | The search scope can be restricted to by the domain argument. | |
4165 | ||
4166 | @var{name} is the name of the symbol. It must be a string. | |
4167 | The optional @var{domain} argument restricts the search to the domain type. | |
4168 | The @var{domain} argument must be a domain constant defined in the @code{gdb} | |
4169 | module and described later in this chapter. | |
4170 | ||
4171 | The result is a @code{gdb.Symbol} object or @code{None} if the symbol | |
4172 | is not found. | |
4173 | @end defun | |
4174 | ||
4175 | A @code{gdb.Symbol} object has the following attributes: | |
4176 | ||
4177 | @defvar Symbol.type | |
4178 | The type of the symbol or @code{None} if no type is recorded. | |
4179 | This attribute is represented as a @code{gdb.Type} object. | |
4180 | @xref{Types In Python}. This attribute is not writable. | |
4181 | @end defvar | |
4182 | ||
4183 | @defvar Symbol.symtab | |
4184 | The symbol table in which the symbol appears. This attribute is | |
4185 | represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In | |
4186 | Python}. This attribute is not writable. | |
4187 | @end defvar | |
4188 | ||
4189 | @defvar Symbol.line | |
4190 | The line number in the source code at which the symbol was defined. | |
4191 | This is an integer. | |
4192 | @end defvar | |
4193 | ||
4194 | @defvar Symbol.name | |
4195 | The name of the symbol as a string. This attribute is not writable. | |
4196 | @end defvar | |
4197 | ||
4198 | @defvar Symbol.linkage_name | |
4199 | The name of the symbol, as used by the linker (i.e., may be mangled). | |
4200 | This attribute is not writable. | |
4201 | @end defvar | |
4202 | ||
4203 | @defvar Symbol.print_name | |
4204 | The name of the symbol in a form suitable for output. This is either | |
4205 | @code{name} or @code{linkage_name}, depending on whether the user | |
4206 | asked @value{GDBN} to display demangled or mangled names. | |
4207 | @end defvar | |
4208 | ||
4209 | @defvar Symbol.addr_class | |
4210 | The address class of the symbol. This classifies how to find the value | |
4211 | of a symbol. Each address class is a constant defined in the | |
4212 | @code{gdb} module and described later in this chapter. | |
4213 | @end defvar | |
4214 | ||
4215 | @defvar Symbol.needs_frame | |
4216 | This is @code{True} if evaluating this symbol's value requires a frame | |
4217 | (@pxref{Frames In Python}) and @code{False} otherwise. Typically, | |
4218 | local variables will require a frame, but other symbols will not. | |
4219 | @end defvar | |
4220 | ||
4221 | @defvar Symbol.is_argument | |
4222 | @code{True} if the symbol is an argument of a function. | |
4223 | @end defvar | |
4224 | ||
4225 | @defvar Symbol.is_constant | |
4226 | @code{True} if the symbol is a constant. | |
4227 | @end defvar | |
4228 | ||
4229 | @defvar Symbol.is_function | |
4230 | @code{True} if the symbol is a function or a method. | |
4231 | @end defvar | |
4232 | ||
4233 | @defvar Symbol.is_variable | |
4234 | @code{True} if the symbol is a variable. | |
4235 | @end defvar | |
4236 | ||
4237 | A @code{gdb.Symbol} object has the following methods: | |
4238 | ||
4239 | @defun Symbol.is_valid () | |
4240 | Returns @code{True} if the @code{gdb.Symbol} object is valid, | |
4241 | @code{False} if not. A @code{gdb.Symbol} object can become invalid if | |
4242 | the symbol it refers to does not exist in @value{GDBN} any longer. | |
4243 | All other @code{gdb.Symbol} methods will throw an exception if it is | |
4244 | invalid at the time the method is called. | |
4245 | @end defun | |
4246 | ||
4247 | @defun Symbol.value (@r{[}frame@r{]}) | |
4248 | Compute the value of the symbol, as a @code{gdb.Value}. For | |
4249 | functions, this computes the address of the function, cast to the | |
4250 | appropriate type. If the symbol requires a frame in order to compute | |
4251 | its value, then @var{frame} must be given. If @var{frame} is not | |
4252 | given, or if @var{frame} is invalid, then this method will throw an | |
4253 | exception. | |
4254 | @end defun | |
4255 | ||
4256 | The available domain categories in @code{gdb.Symbol} are represented | |
4257 | as constants in the @code{gdb} module: | |
4258 | ||
b3ce5e5f DE |
4259 | @vtable @code |
4260 | @vindex SYMBOL_UNDEF_DOMAIN | |
329baa95 DE |
4261 | @item gdb.SYMBOL_UNDEF_DOMAIN |
4262 | This is used when a domain has not been discovered or none of the | |
4263 | following domains apply. This usually indicates an error either | |
4264 | in the symbol information or in @value{GDBN}'s handling of symbols. | |
b3ce5e5f DE |
4265 | |
4266 | @vindex SYMBOL_VAR_DOMAIN | |
329baa95 DE |
4267 | @item gdb.SYMBOL_VAR_DOMAIN |
4268 | This domain contains variables, function names, typedef names and enum | |
4269 | type values. | |
b3ce5e5f DE |
4270 | |
4271 | @vindex SYMBOL_STRUCT_DOMAIN | |
329baa95 DE |
4272 | @item gdb.SYMBOL_STRUCT_DOMAIN |
4273 | This domain holds struct, union and enum type names. | |
b3ce5e5f DE |
4274 | |
4275 | @vindex SYMBOL_LABEL_DOMAIN | |
329baa95 DE |
4276 | @item gdb.SYMBOL_LABEL_DOMAIN |
4277 | This domain contains names of labels (for gotos). | |
b3ce5e5f DE |
4278 | |
4279 | @vindex SYMBOL_VARIABLES_DOMAIN | |
329baa95 DE |
4280 | @item gdb.SYMBOL_VARIABLES_DOMAIN |
4281 | This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it | |
4282 | contains everything minus functions and types. | |
b3ce5e5f DE |
4283 | |
4284 | @vindex SYMBOL_FUNCTIONS_DOMAIN | |
329baa95 DE |
4285 | @item gdb.SYMBOL_FUNCTION_DOMAIN |
4286 | This domain contains all functions. | |
b3ce5e5f DE |
4287 | |
4288 | @vindex SYMBOL_TYPES_DOMAIN | |
329baa95 DE |
4289 | @item gdb.SYMBOL_TYPES_DOMAIN |
4290 | This domain contains all types. | |
b3ce5e5f | 4291 | @end vtable |
329baa95 DE |
4292 | |
4293 | The available address class categories in @code{gdb.Symbol} are represented | |
4294 | as constants in the @code{gdb} module: | |
4295 | ||
b3ce5e5f DE |
4296 | @vtable @code |
4297 | @vindex SYMBOL_LOC_UNDEF | |
329baa95 DE |
4298 | @item gdb.SYMBOL_LOC_UNDEF |
4299 | If this is returned by address class, it indicates an error either in | |
4300 | the symbol information or in @value{GDBN}'s handling of symbols. | |
b3ce5e5f DE |
4301 | |
4302 | @vindex SYMBOL_LOC_CONST | |
329baa95 DE |
4303 | @item gdb.SYMBOL_LOC_CONST |
4304 | Value is constant int. | |
b3ce5e5f DE |
4305 | |
4306 | @vindex SYMBOL_LOC_STATIC | |
329baa95 DE |
4307 | @item gdb.SYMBOL_LOC_STATIC |
4308 | Value is at a fixed address. | |
b3ce5e5f DE |
4309 | |
4310 | @vindex SYMBOL_LOC_REGISTER | |
329baa95 DE |
4311 | @item gdb.SYMBOL_LOC_REGISTER |
4312 | Value is in a register. | |
b3ce5e5f DE |
4313 | |
4314 | @vindex SYMBOL_LOC_ARG | |
329baa95 DE |
4315 | @item gdb.SYMBOL_LOC_ARG |
4316 | Value is an argument. This value is at the offset stored within the | |
4317 | symbol inside the frame's argument list. | |
b3ce5e5f DE |
4318 | |
4319 | @vindex SYMBOL_LOC_REF_ARG | |
329baa95 DE |
4320 | @item gdb.SYMBOL_LOC_REF_ARG |
4321 | Value address is stored in the frame's argument list. Just like | |
4322 | @code{LOC_ARG} except that the value's address is stored at the | |
4323 | offset, not the value itself. | |
b3ce5e5f DE |
4324 | |
4325 | @vindex SYMBOL_LOC_REGPARM_ADDR | |
329baa95 DE |
4326 | @item gdb.SYMBOL_LOC_REGPARM_ADDR |
4327 | Value is a specified register. Just like @code{LOC_REGISTER} except | |
4328 | the register holds the address of the argument instead of the argument | |
4329 | itself. | |
b3ce5e5f DE |
4330 | |
4331 | @vindex SYMBOL_LOC_LOCAL | |
329baa95 DE |
4332 | @item gdb.SYMBOL_LOC_LOCAL |
4333 | Value is a local variable. | |
b3ce5e5f DE |
4334 | |
4335 | @vindex SYMBOL_LOC_TYPEDEF | |
329baa95 DE |
4336 | @item gdb.SYMBOL_LOC_TYPEDEF |
4337 | Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all | |
4338 | have this class. | |
b3ce5e5f DE |
4339 | |
4340 | @vindex SYMBOL_LOC_BLOCK | |
329baa95 DE |
4341 | @item gdb.SYMBOL_LOC_BLOCK |
4342 | Value is a block. | |
b3ce5e5f DE |
4343 | |
4344 | @vindex SYMBOL_LOC_CONST_BYTES | |
329baa95 DE |
4345 | @item gdb.SYMBOL_LOC_CONST_BYTES |
4346 | Value is a byte-sequence. | |
b3ce5e5f DE |
4347 | |
4348 | @vindex SYMBOL_LOC_UNRESOLVED | |
329baa95 DE |
4349 | @item gdb.SYMBOL_LOC_UNRESOLVED |
4350 | Value is at a fixed address, but the address of the variable has to be | |
4351 | determined from the minimal symbol table whenever the variable is | |
4352 | referenced. | |
b3ce5e5f DE |
4353 | |
4354 | @vindex SYMBOL_LOC_OPTIMIZED_OUT | |
329baa95 DE |
4355 | @item gdb.SYMBOL_LOC_OPTIMIZED_OUT |
4356 | The value does not actually exist in the program. | |
b3ce5e5f DE |
4357 | |
4358 | @vindex SYMBOL_LOC_COMPUTED | |
329baa95 DE |
4359 | @item gdb.SYMBOL_LOC_COMPUTED |
4360 | The value's address is a computed location. | |
b3ce5e5f | 4361 | @end vtable |
329baa95 DE |
4362 | |
4363 | @node Symbol Tables In Python | |
4364 | @subsubsection Symbol table representation in Python. | |
4365 | ||
4366 | @cindex symbol tables in python | |
4367 | @tindex gdb.Symtab | |
4368 | @tindex gdb.Symtab_and_line | |
4369 | ||
4370 | Access to symbol table data maintained by @value{GDBN} on the inferior | |
4371 | is exposed to Python via two objects: @code{gdb.Symtab_and_line} and | |
4372 | @code{gdb.Symtab}. Symbol table and line data for a frame is returned | |
4373 | from the @code{find_sal} method in @code{gdb.Frame} object. | |
4374 | @xref{Frames In Python}. | |
4375 | ||
4376 | For more information on @value{GDBN}'s symbol table management, see | |
4377 | @ref{Symbols, ,Examining the Symbol Table}, for more information. | |
4378 | ||
4379 | A @code{gdb.Symtab_and_line} object has the following attributes: | |
4380 | ||
4381 | @defvar Symtab_and_line.symtab | |
4382 | The symbol table object (@code{gdb.Symtab}) for this frame. | |
4383 | This attribute is not writable. | |
4384 | @end defvar | |
4385 | ||
4386 | @defvar Symtab_and_line.pc | |
4387 | Indicates the start of the address range occupied by code for the | |
4388 | current source line. This attribute is not writable. | |
4389 | @end defvar | |
4390 | ||
4391 | @defvar Symtab_and_line.last | |
4392 | Indicates the end of the address range occupied by code for the current | |
4393 | source line. This attribute is not writable. | |
4394 | @end defvar | |
4395 | ||
4396 | @defvar Symtab_and_line.line | |
4397 | Indicates the current line number for this object. This | |
4398 | attribute is not writable. | |
4399 | @end defvar | |
4400 | ||
4401 | A @code{gdb.Symtab_and_line} object has the following methods: | |
4402 | ||
4403 | @defun Symtab_and_line.is_valid () | |
4404 | Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid, | |
4405 | @code{False} if not. A @code{gdb.Symtab_and_line} object can become | |
4406 | invalid if the Symbol table and line object it refers to does not | |
4407 | exist in @value{GDBN} any longer. All other | |
4408 | @code{gdb.Symtab_and_line} methods will throw an exception if it is | |
4409 | invalid at the time the method is called. | |
4410 | @end defun | |
4411 | ||
4412 | A @code{gdb.Symtab} object has the following attributes: | |
4413 | ||
4414 | @defvar Symtab.filename | |
4415 | The symbol table's source filename. This attribute is not writable. | |
4416 | @end defvar | |
4417 | ||
4418 | @defvar Symtab.objfile | |
4419 | The symbol table's backing object file. @xref{Objfiles In Python}. | |
4420 | This attribute is not writable. | |
4421 | @end defvar | |
4422 | ||
2b4fd423 DE |
4423 | @defvar Symtab.producer |
4424 | The name and possibly version number of the program that | |
4425 | compiled the code in the symbol table. | |
4426 | The contents of this string is up to the compiler. | |
4427 | If no producer information is available then @code{None} is returned. | |
4428 | This attribute is not writable. | |
4429 | @end defvar | |
4430 | ||
329baa95 DE |
4431 | A @code{gdb.Symtab} object has the following methods: |
4432 | ||
4433 | @defun Symtab.is_valid () | |
4434 | Returns @code{True} if the @code{gdb.Symtab} object is valid, | |
4435 | @code{False} if not. A @code{gdb.Symtab} object can become invalid if | |
4436 | the symbol table it refers to does not exist in @value{GDBN} any | |
4437 | longer. All other @code{gdb.Symtab} methods will throw an exception | |
4438 | if it is invalid at the time the method is called. | |
4439 | @end defun | |
4440 | ||
4441 | @defun Symtab.fullname () | |
4442 | Return the symbol table's source absolute file name. | |
4443 | @end defun | |
4444 | ||
4445 | @defun Symtab.global_block () | |
4446 | Return the global block of the underlying symbol table. | |
4447 | @xref{Blocks In Python}. | |
4448 | @end defun | |
4449 | ||
4450 | @defun Symtab.static_block () | |
4451 | Return the static block of the underlying symbol table. | |
4452 | @xref{Blocks In Python}. | |
4453 | @end defun | |
4454 | ||
4455 | @defun Symtab.linetable () | |
4456 | Return the line table associated with the symbol table. | |
4457 | @xref{Line Tables In Python}. | |
4458 | @end defun | |
4459 | ||
4460 | @node Line Tables In Python | |
4461 | @subsubsection Manipulating line tables using Python | |
4462 | ||
4463 | @cindex line tables in python | |
4464 | @tindex gdb.LineTable | |
4465 | ||
4466 | Python code can request and inspect line table information from a | |
4467 | symbol table that is loaded in @value{GDBN}. A line table is a | |
4468 | mapping of source lines to their executable locations in memory. To | |
4469 | acquire the line table information for a particular symbol table, use | |
4470 | the @code{linetable} function (@pxref{Symbol Tables In Python}). | |
4471 | ||
4472 | A @code{gdb.LineTable} is iterable. The iterator returns | |
4473 | @code{LineTableEntry} objects that correspond to the source line and | |
4474 | address for each line table entry. @code{LineTableEntry} objects have | |
4475 | the following attributes: | |
4476 | ||
4477 | @defvar LineTableEntry.line | |
4478 | The source line number for this line table entry. This number | |
4479 | corresponds to the actual line of source. This attribute is not | |
4480 | writable. | |
4481 | @end defvar | |
4482 | ||
4483 | @defvar LineTableEntry.pc | |
4484 | The address that is associated with the line table entry where the | |
4485 | executable code for that source line resides in memory. This | |
4486 | attribute is not writable. | |
4487 | @end defvar | |
4488 | ||
4489 | As there can be multiple addresses for a single source line, you may | |
4490 | receive multiple @code{LineTableEntry} objects with matching | |
4491 | @code{line} attributes, but with different @code{pc} attributes. The | |
4492 | iterator is sorted in ascending @code{pc} order. Here is a small | |
4493 | example illustrating iterating over a line table. | |
4494 | ||
4495 | @smallexample | |
4496 | symtab = gdb.selected_frame().find_sal().symtab | |
4497 | linetable = symtab.linetable() | |
4498 | for line in linetable: | |
4499 | print "Line: "+str(line.line)+" Address: "+hex(line.pc) | |
4500 | @end smallexample | |
4501 | ||
4502 | This will have the following output: | |
4503 | ||
4504 | @smallexample | |
4505 | Line: 33 Address: 0x4005c8L | |
4506 | Line: 37 Address: 0x4005caL | |
4507 | Line: 39 Address: 0x4005d2L | |
4508 | Line: 40 Address: 0x4005f8L | |
4509 | Line: 42 Address: 0x4005ffL | |
4510 | Line: 44 Address: 0x400608L | |
4511 | Line: 42 Address: 0x40060cL | |
4512 | Line: 45 Address: 0x400615L | |
4513 | @end smallexample | |
4514 | ||
4515 | In addition to being able to iterate over a @code{LineTable}, it also | |
4516 | has the following direct access methods: | |
4517 | ||
4518 | @defun LineTable.line (line) | |
4519 | Return a Python @code{Tuple} of @code{LineTableEntry} objects for any | |
697aa1b7 EZ |
4520 | entries in the line table for the given @var{line}, which specifies |
4521 | the source code line. If there are no entries for that source code | |
329baa95 DE |
4522 | @var{line}, the Python @code{None} is returned. |
4523 | @end defun | |
4524 | ||
4525 | @defun LineTable.has_line (line) | |
4526 | Return a Python @code{Boolean} indicating whether there is an entry in | |
4527 | the line table for this source line. Return @code{True} if an entry | |
4528 | is found, or @code{False} if not. | |
4529 | @end defun | |
4530 | ||
4531 | @defun LineTable.source_lines () | |
4532 | Return a Python @code{List} of the source line numbers in the symbol | |
4533 | table. Only lines with executable code locations are returned. The | |
4534 | contents of the @code{List} will just be the source line entries | |
4535 | represented as Python @code{Long} values. | |
4536 | @end defun | |
4537 | ||
4538 | @node Breakpoints In Python | |
4539 | @subsubsection Manipulating breakpoints using Python | |
4540 | ||
4541 | @cindex breakpoints in python | |
4542 | @tindex gdb.Breakpoint | |
4543 | ||
4544 | Python code can manipulate breakpoints via the @code{gdb.Breakpoint} | |
4545 | class. | |
4546 | ||
4547 | @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]}) | |
697aa1b7 EZ |
4548 | Create a new breakpoint according to @var{spec}, which is a string |
4549 | naming the location of the breakpoint, or an expression that defines a | |
4550 | watchpoint. The contents can be any location recognized by the | |
4551 | @code{break} command, or in the case of a watchpoint, by the | |
4552 | @code{watch} command. The optional @var{type} denotes the breakpoint | |
4553 | to create from the types defined later in this chapter. This argument | |
4554 | can be either @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}; it | |
329baa95 DE |
4555 | defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} |
4556 | argument allows the breakpoint to become invisible to the user. The | |
4557 | breakpoint will neither be reported when created, nor will it be | |
4558 | listed in the output from @code{info breakpoints} (but will be listed | |
4559 | with the @code{maint info breakpoints} command). The optional | |
4560 | @var{temporary} argument makes the breakpoint a temporary breakpoint. | |
4561 | Temporary breakpoints are deleted after they have been hit. Any | |
4562 | further access to the Python breakpoint after it has been hit will | |
4563 | result in a runtime error (as that breakpoint has now been | |
4564 | automatically deleted). The optional @var{wp_class} argument defines | |
4565 | the class of watchpoint to create, if @var{type} is | |
4566 | @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it | |
4567 | is assumed to be a @code{gdb.WP_WRITE} class. | |
4568 | @end defun | |
4569 | ||
4570 | @defun Breakpoint.stop (self) | |
4571 | The @code{gdb.Breakpoint} class can be sub-classed and, in | |
4572 | particular, you may choose to implement the @code{stop} method. | |
4573 | If this method is defined in a sub-class of @code{gdb.Breakpoint}, | |
4574 | it will be called when the inferior reaches any location of a | |
4575 | breakpoint which instantiates that sub-class. If the method returns | |
4576 | @code{True}, the inferior will be stopped at the location of the | |
4577 | breakpoint, otherwise the inferior will continue. | |
4578 | ||
4579 | If there are multiple breakpoints at the same location with a | |
4580 | @code{stop} method, each one will be called regardless of the | |
4581 | return status of the previous. This ensures that all @code{stop} | |
4582 | methods have a chance to execute at that location. In this scenario | |
4583 | if one of the methods returns @code{True} but the others return | |
4584 | @code{False}, the inferior will still be stopped. | |
4585 | ||
4586 | You should not alter the execution state of the inferior (i.e.@:, step, | |
4587 | next, etc.), alter the current frame context (i.e.@:, change the current | |
4588 | active frame), or alter, add or delete any breakpoint. As a general | |
4589 | rule, you should not alter any data within @value{GDBN} or the inferior | |
4590 | at this time. | |
4591 | ||
4592 | Example @code{stop} implementation: | |
4593 | ||
4594 | @smallexample | |
4595 | class MyBreakpoint (gdb.Breakpoint): | |
4596 | def stop (self): | |
4597 | inf_val = gdb.parse_and_eval("foo") | |
4598 | if inf_val == 3: | |
4599 | return True | |
4600 | return False | |
4601 | @end smallexample | |
4602 | @end defun | |
4603 | ||
4604 | The available watchpoint types represented by constants are defined in the | |
4605 | @code{gdb} module: | |
4606 | ||
b3ce5e5f DE |
4607 | @vtable @code |
4608 | @vindex WP_READ | |
329baa95 DE |
4609 | @item gdb.WP_READ |
4610 | Read only watchpoint. | |
4611 | ||
b3ce5e5f | 4612 | @vindex WP_WRITE |
329baa95 DE |
4613 | @item gdb.WP_WRITE |
4614 | Write only watchpoint. | |
4615 | ||
b3ce5e5f | 4616 | @vindex WP_ACCESS |
329baa95 DE |
4617 | @item gdb.WP_ACCESS |
4618 | Read/Write watchpoint. | |
b3ce5e5f | 4619 | @end vtable |
329baa95 DE |
4620 | |
4621 | @defun Breakpoint.is_valid () | |
4622 | Return @code{True} if this @code{Breakpoint} object is valid, | |
4623 | @code{False} otherwise. A @code{Breakpoint} object can become invalid | |
4624 | if the user deletes the breakpoint. In this case, the object still | |
4625 | exists, but the underlying breakpoint does not. In the cases of | |
4626 | watchpoint scope, the watchpoint remains valid even if execution of the | |
4627 | inferior leaves the scope of that watchpoint. | |
4628 | @end defun | |
4629 | ||
fab3a15d | 4630 | @defun Breakpoint.delete () |
329baa95 DE |
4631 | Permanently deletes the @value{GDBN} breakpoint. This also |
4632 | invalidates the Python @code{Breakpoint} object. Any further access | |
4633 | to this object's attributes or methods will raise an error. | |
4634 | @end defun | |
4635 | ||
4636 | @defvar Breakpoint.enabled | |
4637 | This attribute is @code{True} if the breakpoint is enabled, and | |
fab3a15d SM |
4638 | @code{False} otherwise. This attribute is writable. You can use it to enable |
4639 | or disable the breakpoint. | |
329baa95 DE |
4640 | @end defvar |
4641 | ||
4642 | @defvar Breakpoint.silent | |
4643 | This attribute is @code{True} if the breakpoint is silent, and | |
4644 | @code{False} otherwise. This attribute is writable. | |
4645 | ||
4646 | Note that a breakpoint can also be silent if it has commands and the | |
4647 | first command is @code{silent}. This is not reported by the | |
4648 | @code{silent} attribute. | |
4649 | @end defvar | |
4650 | ||
22a02324 | 4651 | @anchor{python_breakpoint_thread} |
329baa95 | 4652 | @defvar Breakpoint.thread |
5d5658a1 PA |
4653 | If the breakpoint is thread-specific, this attribute holds the |
4654 | thread's global id. If the breakpoint is not thread-specific, this | |
4655 | attribute is @code{None}. This attribute is writable. | |
329baa95 DE |
4656 | @end defvar |
4657 | ||
4658 | @defvar Breakpoint.task | |
4659 | If the breakpoint is Ada task-specific, this attribute holds the Ada task | |
4660 | id. If the breakpoint is not task-specific (or the underlying | |
4661 | language is not Ada), this attribute is @code{None}. This attribute | |
4662 | is writable. | |
4663 | @end defvar | |
4664 | ||
4665 | @defvar Breakpoint.ignore_count | |
4666 | This attribute holds the ignore count for the breakpoint, an integer. | |
4667 | This attribute is writable. | |
4668 | @end defvar | |
4669 | ||
4670 | @defvar Breakpoint.number | |
4671 | This attribute holds the breakpoint's number --- the identifier used by | |
4672 | the user to manipulate the breakpoint. This attribute is not writable. | |
4673 | @end defvar | |
4674 | ||
4675 | @defvar Breakpoint.type | |
4676 | This attribute holds the breakpoint's type --- the identifier used to | |
4677 | determine the actual breakpoint type or use-case. This attribute is not | |
4678 | writable. | |
4679 | @end defvar | |
4680 | ||
4681 | @defvar Breakpoint.visible | |
4682 | This attribute tells whether the breakpoint is visible to the user | |
4683 | when set, or when the @samp{info breakpoints} command is run. This | |
4684 | attribute is not writable. | |
4685 | @end defvar | |
4686 | ||
4687 | @defvar Breakpoint.temporary | |
4688 | This attribute indicates whether the breakpoint was created as a | |
4689 | temporary breakpoint. Temporary breakpoints are automatically deleted | |
4690 | after that breakpoint has been hit. Access to this attribute, and all | |
4691 | other attributes and functions other than the @code{is_valid} | |
4692 | function, will result in an error after the breakpoint has been hit | |
4693 | (as it has been automatically deleted). This attribute is not | |
4694 | writable. | |
4695 | @end defvar | |
4696 | ||
4697 | The available types are represented by constants defined in the @code{gdb} | |
4698 | module: | |
4699 | ||
b3ce5e5f DE |
4700 | @vtable @code |
4701 | @vindex BP_BREAKPOINT | |
329baa95 DE |
4702 | @item gdb.BP_BREAKPOINT |
4703 | Normal code breakpoint. | |
4704 | ||
b3ce5e5f | 4705 | @vindex BP_WATCHPOINT |
329baa95 DE |
4706 | @item gdb.BP_WATCHPOINT |
4707 | Watchpoint breakpoint. | |
4708 | ||
b3ce5e5f | 4709 | @vindex BP_HARDWARE_WATCHPOINT |
329baa95 DE |
4710 | @item gdb.BP_HARDWARE_WATCHPOINT |
4711 | Hardware assisted watchpoint. | |
4712 | ||
b3ce5e5f | 4713 | @vindex BP_READ_WATCHPOINT |
329baa95 DE |
4714 | @item gdb.BP_READ_WATCHPOINT |
4715 | Hardware assisted read watchpoint. | |
4716 | ||
b3ce5e5f | 4717 | @vindex BP_ACCESS_WATCHPOINT |
329baa95 DE |
4718 | @item gdb.BP_ACCESS_WATCHPOINT |
4719 | Hardware assisted access watchpoint. | |
b3ce5e5f | 4720 | @end vtable |
329baa95 DE |
4721 | |
4722 | @defvar Breakpoint.hit_count | |
4723 | This attribute holds the hit count for the breakpoint, an integer. | |
4724 | This attribute is writable, but currently it can only be set to zero. | |
4725 | @end defvar | |
4726 | ||
4727 | @defvar Breakpoint.location | |
4728 | This attribute holds the location of the breakpoint, as specified by | |
4729 | the user. It is a string. If the breakpoint does not have a location | |
4730 | (that is, it is a watchpoint) the attribute's value is @code{None}. This | |
4731 | attribute is not writable. | |
4732 | @end defvar | |
4733 | ||
4734 | @defvar Breakpoint.expression | |
4735 | This attribute holds a breakpoint expression, as specified by | |
4736 | the user. It is a string. If the breakpoint does not have an | |
4737 | expression (the breakpoint is not a watchpoint) the attribute's value | |
4738 | is @code{None}. This attribute is not writable. | |
4739 | @end defvar | |
4740 | ||
4741 | @defvar Breakpoint.condition | |
4742 | This attribute holds the condition of the breakpoint, as specified by | |
4743 | the user. It is a string. If there is no condition, this attribute's | |
4744 | value is @code{None}. This attribute is writable. | |
4745 | @end defvar | |
4746 | ||
4747 | @defvar Breakpoint.commands | |
4748 | This attribute holds the commands attached to the breakpoint. If | |
4749 | there are commands, this attribute's value is a string holding all the | |
4750 | commands, separated by newlines. If there are no commands, this | |
4751 | attribute is @code{None}. This attribute is not writable. | |
4752 | @end defvar | |
4753 | ||
4754 | @node Finish Breakpoints in Python | |
4755 | @subsubsection Finish Breakpoints | |
4756 | ||
4757 | @cindex python finish breakpoints | |
4758 | @tindex gdb.FinishBreakpoint | |
4759 | ||
4760 | A finish breakpoint is a temporary breakpoint set at the return address of | |
4761 | a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint} | |
4762 | extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled | |
4763 | and deleted when the execution will run out of the breakpoint scope (i.e.@: | |
4764 | @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered). | |
4765 | Finish breakpoints are thread specific and must be create with the right | |
4766 | thread selected. | |
4767 | ||
4768 | @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]}) | |
4769 | Create a finish breakpoint at the return address of the @code{gdb.Frame} | |
4770 | object @var{frame}. If @var{frame} is not provided, this defaults to the | |
4771 | newest frame. The optional @var{internal} argument allows the breakpoint to | |
4772 | become invisible to the user. @xref{Breakpoints In Python}, for further | |
4773 | details about this argument. | |
4774 | @end defun | |
4775 | ||
4776 | @defun FinishBreakpoint.out_of_scope (self) | |
4777 | In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN} | |
4778 | @code{return} command, @dots{}), a function may not properly terminate, and | |
4779 | thus never hit the finish breakpoint. When @value{GDBN} notices such a | |
4780 | situation, the @code{out_of_scope} callback will be triggered. | |
4781 | ||
4782 | You may want to sub-class @code{gdb.FinishBreakpoint} and override this | |
4783 | method: | |
4784 | ||
4785 | @smallexample | |
4786 | class MyFinishBreakpoint (gdb.FinishBreakpoint) | |
4787 | def stop (self): | |
4788 | print "normal finish" | |
4789 | return True | |
4790 | ||
4791 | def out_of_scope (): | |
4792 | print "abnormal finish" | |
4793 | @end smallexample | |
4794 | @end defun | |
4795 | ||
4796 | @defvar FinishBreakpoint.return_value | |
4797 | When @value{GDBN} is stopped at a finish breakpoint and the frame | |
4798 | used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this | |
4799 | attribute will contain a @code{gdb.Value} object corresponding to the return | |
4800 | value of the function. The value will be @code{None} if the function return | |
4801 | type is @code{void} or if the return value was not computable. This attribute | |
4802 | is not writable. | |
4803 | @end defvar | |
4804 | ||
4805 | @node Lazy Strings In Python | |
4806 | @subsubsection Python representation of lazy strings. | |
4807 | ||
4808 | @cindex lazy strings in python | |
4809 | @tindex gdb.LazyString | |
4810 | ||
4811 | A @dfn{lazy string} is a string whose contents is not retrieved or | |
4812 | encoded until it is needed. | |
4813 | ||
4814 | A @code{gdb.LazyString} is represented in @value{GDBN} as an | |
4815 | @code{address} that points to a region of memory, an @code{encoding} | |
4816 | that will be used to encode that region of memory, and a @code{length} | |
4817 | to delimit the region of memory that represents the string. The | |
4818 | difference between a @code{gdb.LazyString} and a string wrapped within | |
4819 | a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated | |
4820 | differently by @value{GDBN} when printing. A @code{gdb.LazyString} is | |
4821 | retrieved and encoded during printing, while a @code{gdb.Value} | |
4822 | wrapping a string is immediately retrieved and encoded on creation. | |
4823 | ||
4824 | A @code{gdb.LazyString} object has the following functions: | |
4825 | ||
4826 | @defun LazyString.value () | |
4827 | Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value | |
4828 | will point to the string in memory, but will lose all the delayed | |
4829 | retrieval, encoding and handling that @value{GDBN} applies to a | |
4830 | @code{gdb.LazyString}. | |
4831 | @end defun | |
4832 | ||
4833 | @defvar LazyString.address | |
4834 | This attribute holds the address of the string. This attribute is not | |
4835 | writable. | |
4836 | @end defvar | |
4837 | ||
4838 | @defvar LazyString.length | |
4839 | This attribute holds the length of the string in characters. If the | |
4840 | length is -1, then the string will be fetched and encoded up to the | |
4841 | first null of appropriate width. This attribute is not writable. | |
4842 | @end defvar | |
4843 | ||
4844 | @defvar LazyString.encoding | |
4845 | This attribute holds the encoding that will be applied to the string | |
4846 | when the string is printed by @value{GDBN}. If the encoding is not | |
4847 | set, or contains an empty string, then @value{GDBN} will select the | |
4848 | most appropriate encoding when the string is printed. This attribute | |
4849 | is not writable. | |
4850 | @end defvar | |
4851 | ||
4852 | @defvar LazyString.type | |
4853 | This attribute holds the type that is represented by the lazy string's | |
4854 | type. For a lazy string this will always be a pointer type. To | |
4855 | resolve this to the lazy string's character type, use the type's | |
4856 | @code{target} method. @xref{Types In Python}. This attribute is not | |
4857 | writable. | |
4858 | @end defvar | |
4859 | ||
4860 | @node Architectures In Python | |
4861 | @subsubsection Python representation of architectures | |
4862 | @cindex Python architectures | |
4863 | ||
4864 | @value{GDBN} uses architecture specific parameters and artifacts in a | |
4865 | number of its various computations. An architecture is represented | |
4866 | by an instance of the @code{gdb.Architecture} class. | |
4867 | ||
4868 | A @code{gdb.Architecture} class has the following methods: | |
4869 | ||
4870 | @defun Architecture.name () | |
4871 | Return the name (string value) of the architecture. | |
4872 | @end defun | |
4873 | ||
4874 | @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]}) | |
4875 | Return a list of disassembled instructions starting from the memory | |
4876 | address @var{start_pc}. The optional arguments @var{end_pc} and | |
4877 | @var{count} determine the number of instructions in the returned list. | |
4878 | If both the optional arguments @var{end_pc} and @var{count} are | |
4879 | specified, then a list of at most @var{count} disassembled instructions | |
4880 | whose start address falls in the closed memory address interval from | |
4881 | @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not | |
4882 | specified, but @var{count} is specified, then @var{count} number of | |
4883 | instructions starting from the address @var{start_pc} are returned. If | |
4884 | @var{count} is not specified but @var{end_pc} is specified, then all | |
4885 | instructions whose start address falls in the closed memory address | |
4886 | interval from @var{start_pc} to @var{end_pc} are returned. If neither | |
4887 | @var{end_pc} nor @var{count} are specified, then a single instruction at | |
4888 | @var{start_pc} is returned. For all of these cases, each element of the | |
4889 | returned list is a Python @code{dict} with the following string keys: | |
4890 | ||
4891 | @table @code | |
4892 | ||
4893 | @item addr | |
4894 | The value corresponding to this key is a Python long integer capturing | |
4895 | the memory address of the instruction. | |
4896 | ||
4897 | @item asm | |
4898 | The value corresponding to this key is a string value which represents | |
4899 | the instruction with assembly language mnemonics. The assembly | |
4900 | language flavor used is the same as that specified by the current CLI | |
4901 | variable @code{disassembly-flavor}. @xref{Machine Code}. | |
4902 | ||
4903 | @item length | |
4904 | The value corresponding to this key is the length (integer value) of the | |
4905 | instruction in bytes. | |
4906 | ||
4907 | @end table | |
4908 | @end defun | |
4909 | ||
4910 | @node Python Auto-loading | |
4911 | @subsection Python Auto-loading | |
4912 | @cindex Python auto-loading | |
4913 | ||
4914 | When a new object file is read (for example, due to the @code{file} | |
4915 | command, or because the inferior has loaded a shared library), | |
4916 | @value{GDBN} will look for Python support scripts in several ways: | |
4917 | @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section. | |
4918 | @xref{Auto-loading extensions}. | |
4919 | ||
4920 | The auto-loading feature is useful for supplying application-specific | |
4921 | debugging commands and scripts. | |
4922 | ||
4923 | Auto-loading can be enabled or disabled, | |
4924 | and the list of auto-loaded scripts can be printed. | |
4925 | ||
4926 | @table @code | |
4927 | @anchor{set auto-load python-scripts} | |
4928 | @kindex set auto-load python-scripts | |
4929 | @item set auto-load python-scripts [on|off] | |
4930 | Enable or disable the auto-loading of Python scripts. | |
4931 | ||
4932 | @anchor{show auto-load python-scripts} | |
4933 | @kindex show auto-load python-scripts | |
4934 | @item show auto-load python-scripts | |
4935 | Show whether auto-loading of Python scripts is enabled or disabled. | |
4936 | ||
4937 | @anchor{info auto-load python-scripts} | |
4938 | @kindex info auto-load python-scripts | |
4939 | @cindex print list of auto-loaded Python scripts | |
4940 | @item info auto-load python-scripts [@var{regexp}] | |
4941 | Print the list of all Python scripts that @value{GDBN} auto-loaded. | |
4942 | ||
4943 | Also printed is the list of Python scripts that were mentioned in | |
9f050062 DE |
4944 | the @code{.debug_gdb_scripts} section and were either not found |
4945 | (@pxref{dotdebug_gdb_scripts section}) or were not auto-loaded due to | |
4946 | @code{auto-load safe-path} rejection (@pxref{Auto-loading}). | |
329baa95 DE |
4947 | This is useful because their names are not printed when @value{GDBN} |
4948 | tries to load them and fails. There may be many of them, and printing | |
4949 | an error message for each one is problematic. | |
4950 | ||
4951 | If @var{regexp} is supplied only Python scripts with matching names are printed. | |
4952 | ||
4953 | Example: | |
4954 | ||
4955 | @smallexample | |
4956 | (gdb) info auto-load python-scripts | |
4957 | Loaded Script | |
4958 | Yes py-section-script.py | |
4959 | full name: /tmp/py-section-script.py | |
4960 | No my-foo-pretty-printers.py | |
4961 | @end smallexample | |
4962 | @end table | |
4963 | ||
9f050062 | 4964 | When reading an auto-loaded file or script, @value{GDBN} sets the |
329baa95 DE |
4965 | @dfn{current objfile}. This is available via the @code{gdb.current_objfile} |
4966 | function (@pxref{Objfiles In Python}). This can be useful for | |
4967 | registering objfile-specific pretty-printers and frame-filters. | |
4968 | ||
4969 | @node Python modules | |
4970 | @subsection Python modules | |
4971 | @cindex python modules | |
4972 | ||
4973 | @value{GDBN} comes with several modules to assist writing Python code. | |
4974 | ||
4975 | @menu | |
4976 | * gdb.printing:: Building and registering pretty-printers. | |
4977 | * gdb.types:: Utilities for working with types. | |
4978 | * gdb.prompt:: Utilities for prompt value substitution. | |
4979 | @end menu | |
4980 | ||
4981 | @node gdb.printing | |
4982 | @subsubsection gdb.printing | |
4983 | @cindex gdb.printing | |
4984 | ||
4985 | This module provides a collection of utilities for working with | |
4986 | pretty-printers. | |
4987 | ||
4988 | @table @code | |
4989 | @item PrettyPrinter (@var{name}, @var{subprinters}=None) | |
4990 | This class specifies the API that makes @samp{info pretty-printer}, | |
4991 | @samp{enable pretty-printer} and @samp{disable pretty-printer} work. | |
4992 | Pretty-printers should generally inherit from this class. | |
4993 | ||
4994 | @item SubPrettyPrinter (@var{name}) | |
4995 | For printers that handle multiple types, this class specifies the | |
4996 | corresponding API for the subprinters. | |
4997 | ||
4998 | @item RegexpCollectionPrettyPrinter (@var{name}) | |
4999 | Utility class for handling multiple printers, all recognized via | |
5000 | regular expressions. | |
5001 | @xref{Writing a Pretty-Printer}, for an example. | |
5002 | ||
5003 | @item FlagEnumerationPrinter (@var{name}) | |
5004 | A pretty-printer which handles printing of @code{enum} values. Unlike | |
5005 | @value{GDBN}'s built-in @code{enum} printing, this printer attempts to | |
5006 | work properly when there is some overlap between the enumeration | |
697aa1b7 EZ |
5007 | constants. The argument @var{name} is the name of the printer and |
5008 | also the name of the @code{enum} type to look up. | |
329baa95 DE |
5009 | |
5010 | @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False) | |
5011 | Register @var{printer} with the pretty-printer list of @var{obj}. | |
5012 | If @var{replace} is @code{True} then any existing copy of the printer | |
5013 | is replaced. Otherwise a @code{RuntimeError} exception is raised | |
5014 | if a printer with the same name already exists. | |
5015 | @end table | |
5016 | ||
5017 | @node gdb.types | |
5018 | @subsubsection gdb.types | |
5019 | @cindex gdb.types | |
5020 | ||
5021 | This module provides a collection of utilities for working with | |
5022 | @code{gdb.Type} objects. | |
5023 | ||
5024 | @table @code | |
5025 | @item get_basic_type (@var{type}) | |
5026 | Return @var{type} with const and volatile qualifiers stripped, | |
5027 | and with typedefs and C@t{++} references converted to the underlying type. | |
5028 | ||
5029 | C@t{++} example: | |
5030 | ||
5031 | @smallexample | |
5032 | typedef const int const_int; | |
5033 | const_int foo (3); | |
5034 | const_int& foo_ref (foo); | |
5035 | int main () @{ return 0; @} | |
5036 | @end smallexample | |
5037 | ||
5038 | Then in gdb: | |
5039 | ||
5040 | @smallexample | |
5041 | (gdb) start | |
5042 | (gdb) python import gdb.types | |
5043 | (gdb) python foo_ref = gdb.parse_and_eval("foo_ref") | |
5044 | (gdb) python print gdb.types.get_basic_type(foo_ref.type) | |
5045 | int | |
5046 | @end smallexample | |
5047 | ||
5048 | @item has_field (@var{type}, @var{field}) | |
5049 | Return @code{True} if @var{type}, assumed to be a type with fields | |
5050 | (e.g., a structure or union), has field @var{field}. | |
5051 | ||
5052 | @item make_enum_dict (@var{enum_type}) | |
5053 | Return a Python @code{dictionary} type produced from @var{enum_type}. | |
5054 | ||
5055 | @item deep_items (@var{type}) | |
5056 | Returns a Python iterator similar to the standard | |
5057 | @code{gdb.Type.iteritems} method, except that the iterator returned | |
5058 | by @code{deep_items} will recursively traverse anonymous struct or | |
5059 | union fields. For example: | |
5060 | ||
5061 | @smallexample | |
5062 | struct A | |
5063 | @{ | |
5064 | int a; | |
5065 | union @{ | |
5066 | int b0; | |
5067 | int b1; | |
5068 | @}; | |
5069 | @}; | |
5070 | @end smallexample | |
5071 | ||
5072 | @noindent | |
5073 | Then in @value{GDBN}: | |
5074 | @smallexample | |
5075 | (@value{GDBP}) python import gdb.types | |
5076 | (@value{GDBP}) python struct_a = gdb.lookup_type("struct A") | |
5077 | (@value{GDBP}) python print struct_a.keys () | |
5078 | @{['a', '']@} | |
5079 | (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)] | |
5080 | @{['a', 'b0', 'b1']@} | |
5081 | @end smallexample | |
5082 | ||
5083 | @item get_type_recognizers () | |
5084 | Return a list of the enabled type recognizers for the current context. | |
5085 | This is called by @value{GDBN} during the type-printing process | |
5086 | (@pxref{Type Printing API}). | |
5087 | ||
5088 | @item apply_type_recognizers (recognizers, type_obj) | |
5089 | Apply the type recognizers, @var{recognizers}, to the type object | |
5090 | @var{type_obj}. If any recognizer returns a string, return that | |
5091 | string. Otherwise, return @code{None}. This is called by | |
5092 | @value{GDBN} during the type-printing process (@pxref{Type Printing | |
5093 | API}). | |
5094 | ||
5095 | @item register_type_printer (locus, printer) | |
697aa1b7 EZ |
5096 | This is a convenience function to register a type printer |
5097 | @var{printer}. The printer must implement the type printer protocol. | |
5098 | The @var{locus} argument is either a @code{gdb.Objfile}, in which case | |
5099 | the printer is registered with that objfile; a @code{gdb.Progspace}, | |
5100 | in which case the printer is registered with that progspace; or | |
5101 | @code{None}, in which case the printer is registered globally. | |
329baa95 DE |
5102 | |
5103 | @item TypePrinter | |
5104 | This is a base class that implements the type printer protocol. Type | |
5105 | printers are encouraged, but not required, to derive from this class. | |
5106 | It defines a constructor: | |
5107 | ||
5108 | @defmethod TypePrinter __init__ (self, name) | |
5109 | Initialize the type printer with the given name. The new printer | |
5110 | starts in the enabled state. | |
5111 | @end defmethod | |
5112 | ||
5113 | @end table | |
5114 | ||
5115 | @node gdb.prompt | |
5116 | @subsubsection gdb.prompt | |
5117 | @cindex gdb.prompt | |
5118 | ||
5119 | This module provides a method for prompt value-substitution. | |
5120 | ||
5121 | @table @code | |
5122 | @item substitute_prompt (@var{string}) | |
5123 | Return @var{string} with escape sequences substituted by values. Some | |
5124 | escape sequences take arguments. You can specify arguments inside | |
5125 | ``@{@}'' immediately following the escape sequence. | |
5126 | ||
5127 | The escape sequences you can pass to this function are: | |
5128 | ||
5129 | @table @code | |
5130 | @item \\ | |
5131 | Substitute a backslash. | |
5132 | @item \e | |
5133 | Substitute an ESC character. | |
5134 | @item \f | |
5135 | Substitute the selected frame; an argument names a frame parameter. | |
5136 | @item \n | |
5137 | Substitute a newline. | |
5138 | @item \p | |
5139 | Substitute a parameter's value; the argument names the parameter. | |
5140 | @item \r | |
5141 | Substitute a carriage return. | |
5142 | @item \t | |
5143 | Substitute the selected thread; an argument names a thread parameter. | |
5144 | @item \v | |
5145 | Substitute the version of GDB. | |
5146 | @item \w | |
5147 | Substitute the current working directory. | |
5148 | @item \[ | |
5149 | Begin a sequence of non-printing characters. These sequences are | |
5150 | typically used with the ESC character, and are not counted in the string | |
5151 | length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a | |
5152 | blue-colored ``(gdb)'' prompt where the length is five. | |
5153 | @item \] | |
5154 | End a sequence of non-printing characters. | |
5155 | @end table | |
5156 | ||
5157 | For example: | |
5158 | ||
5159 | @smallexample | |
5160 | substitute_prompt (``frame: \f, | |
5161 | print arguments: \p@{print frame-arguments@}'') | |
5162 | @end smallexample | |
5163 | ||
5164 | @exdent will return the string: | |
5165 | ||
5166 | @smallexample | |
5167 | "frame: main, print arguments: scalars" | |
5168 | @end smallexample | |
5169 | @end table |