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1 | @c Copyright (C) 2008-2014 Free Software Foundation, Inc. |
2 | @c Permission is granted to copy, distribute and/or modify this document | |
3 | @c under the terms of the GNU Free Documentation License, Version 1.3 or | |
4 | @c any later version published by the Free Software Foundation; with the | |
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. | |
147 | * Inferiors In Python:: Python representation of inferiors (processes) | |
148 | * Events In Python:: Listening for events from @value{GDBN}. | |
149 | * Threads In Python:: Accessing inferior threads from Python. | |
150 | * Commands In Python:: Implementing new commands in Python. | |
151 | * Parameters In Python:: Adding new @value{GDBN} parameters. | |
152 | * Functions In Python:: Writing new convenience functions. | |
153 | * Progspaces In Python:: Program spaces. | |
154 | * Objfiles In Python:: Object files. | |
155 | * Frames In Python:: Accessing inferior stack frames from Python. | |
156 | * Blocks In Python:: Accessing blocks from Python. | |
157 | * Symbols In Python:: Python representation of symbols. | |
158 | * Symbol Tables In Python:: Python representation of symbol tables. | |
159 | * Line Tables In Python:: Python representation of line tables. | |
160 | * Breakpoints In Python:: Manipulating breakpoints using Python. | |
161 | * Finish Breakpoints in Python:: Setting Breakpoints on function return | |
162 | using Python. | |
163 | * Lazy Strings In Python:: Python representation of lazy strings. | |
164 | * Architectures In Python:: Python representation of architectures. | |
165 | @end menu | |
166 | ||
167 | @node Basic Python | |
168 | @subsubsection Basic Python | |
169 | ||
170 | @cindex python stdout | |
171 | @cindex python pagination | |
172 | At startup, @value{GDBN} overrides Python's @code{sys.stdout} and | |
173 | @code{sys.stderr} to print using @value{GDBN}'s output-paging streams. | |
174 | A Python program which outputs to one of these streams may have its | |
175 | output interrupted by the user (@pxref{Screen Size}). In this | |
176 | situation, a Python @code{KeyboardInterrupt} exception is thrown. | |
177 | ||
178 | Some care must be taken when writing Python code to run in | |
179 | @value{GDBN}. Two things worth noting in particular: | |
180 | ||
181 | @itemize @bullet | |
182 | @item | |
183 | @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}. | |
184 | Python code must not override these, or even change the options using | |
185 | @code{sigaction}. If your program changes the handling of these | |
186 | signals, @value{GDBN} will most likely stop working correctly. Note | |
187 | that it is unfortunately common for GUI toolkits to install a | |
188 | @code{SIGCHLD} handler. | |
189 | ||
190 | @item | |
191 | @value{GDBN} takes care to mark its internal file descriptors as | |
192 | close-on-exec. However, this cannot be done in a thread-safe way on | |
193 | all platforms. Your Python programs should be aware of this and | |
194 | should both create new file descriptors with the close-on-exec flag | |
195 | set and arrange to close unneeded file descriptors before starting a | |
196 | child process. | |
197 | @end itemize | |
198 | ||
199 | @cindex python functions | |
200 | @cindex python module | |
201 | @cindex gdb module | |
202 | @value{GDBN} introduces a new Python module, named @code{gdb}. All | |
203 | methods and classes added by @value{GDBN} are placed in this module. | |
204 | @value{GDBN} automatically @code{import}s the @code{gdb} module for | |
205 | use in all scripts evaluated by the @code{python} command. | |
206 | ||
207 | @findex gdb.PYTHONDIR | |
208 | @defvar gdb.PYTHONDIR | |
209 | A string containing the python directory (@pxref{Python}). | |
210 | @end defvar | |
211 | ||
212 | @findex gdb.execute | |
213 | @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]}) | |
214 | Evaluate @var{command}, a string, as a @value{GDBN} CLI command. | |
215 | If a GDB exception happens while @var{command} runs, it is | |
216 | translated as described in @ref{Exception Handling,,Exception Handling}. | |
217 | ||
218 | @var{from_tty} specifies whether @value{GDBN} ought to consider this | |
219 | command as having originated from the user invoking it interactively. | |
220 | It must be a boolean value. If omitted, it defaults to @code{False}. | |
221 | ||
222 | By default, any output produced by @var{command} is sent to | |
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223 | @value{GDBN}'s standard output (and to the log output if logging is |
224 | turned on). If the @var{to_string} parameter is | |
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225 | @code{True}, then output will be collected by @code{gdb.execute} and |
226 | returned as a string. The default is @code{False}, in which case the | |
227 | return value is @code{None}. If @var{to_string} is @code{True}, the | |
228 | @value{GDBN} virtual terminal will be temporarily set to unlimited width | |
229 | and height, and its pagination will be disabled; @pxref{Screen Size}. | |
230 | @end defun | |
231 | ||
232 | @findex gdb.breakpoints | |
233 | @defun gdb.breakpoints () | |
234 | Return a sequence holding all of @value{GDBN}'s breakpoints. | |
235 | @xref{Breakpoints In Python}, for more information. | |
236 | @end defun | |
237 | ||
238 | @findex gdb.parameter | |
239 | @defun gdb.parameter (parameter) | |
240 | Return the value of a @value{GDBN} parameter. @var{parameter} is a | |
241 | string naming the parameter to look up; @var{parameter} may contain | |
242 | spaces if the parameter has a multi-part name. For example, | |
243 | @samp{print object} is a valid parameter name. | |
244 | ||
245 | If the named parameter does not exist, this function throws a | |
246 | @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the | |
247 | parameter's value is converted to a Python value of the appropriate | |
248 | type, and returned. | |
249 | @end defun | |
250 | ||
251 | @findex gdb.history | |
252 | @defun gdb.history (number) | |
253 | Return a value from @value{GDBN}'s value history (@pxref{Value | |
254 | History}). @var{number} indicates which history element to return. | |
255 | If @var{number} is negative, then @value{GDBN} will take its absolute value | |
256 | and count backward from the last element (i.e., the most recent element) to | |
257 | find the value to return. If @var{number} is zero, then @value{GDBN} will | |
258 | return the most recent element. If the element specified by @var{number} | |
259 | doesn't exist in the value history, a @code{gdb.error} exception will be | |
260 | raised. | |
261 | ||
262 | If no exception is raised, the return value is always an instance of | |
263 | @code{gdb.Value} (@pxref{Values From Inferior}). | |
264 | @end defun | |
265 | ||
266 | @findex gdb.parse_and_eval | |
267 | @defun gdb.parse_and_eval (expression) | |
268 | Parse @var{expression} as an expression in the current language, | |
269 | evaluate it, and return the result as a @code{gdb.Value}. | |
270 | @var{expression} must be a string. | |
271 | ||
272 | This function can be useful when implementing a new command | |
273 | (@pxref{Commands In Python}), as it provides a way to parse the | |
274 | command's argument as an expression. It is also useful simply to | |
275 | compute values, for example, it is the only way to get the value of a | |
276 | convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}. | |
277 | @end defun | |
278 | ||
279 | @findex gdb.find_pc_line | |
280 | @defun gdb.find_pc_line (pc) | |
281 | Return the @code{gdb.Symtab_and_line} object corresponding to the | |
282 | @var{pc} value. @xref{Symbol Tables In Python}. If an invalid | |
283 | value of @var{pc} is passed as an argument, then the @code{symtab} and | |
284 | @code{line} attributes of the returned @code{gdb.Symtab_and_line} object | |
285 | will be @code{None} and 0 respectively. | |
286 | @end defun | |
287 | ||
288 | @findex gdb.post_event | |
289 | @defun gdb.post_event (event) | |
290 | Put @var{event}, a callable object taking no arguments, into | |
291 | @value{GDBN}'s internal event queue. This callable will be invoked at | |
292 | some later point, during @value{GDBN}'s event processing. Events | |
293 | posted using @code{post_event} will be run in the order in which they | |
294 | were posted; however, there is no way to know when they will be | |
295 | processed relative to other events inside @value{GDBN}. | |
296 | ||
297 | @value{GDBN} is not thread-safe. If your Python program uses multiple | |
298 | threads, you must be careful to only call @value{GDBN}-specific | |
b3ce5e5f | 299 | functions in the @value{GDBN} thread. @code{post_event} ensures |
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300 | this. For example: |
301 | ||
302 | @smallexample | |
303 | (@value{GDBP}) python | |
304 | >import threading | |
305 | > | |
306 | >class Writer(): | |
307 | > def __init__(self, message): | |
308 | > self.message = message; | |
309 | > def __call__(self): | |
310 | > gdb.write(self.message) | |
311 | > | |
312 | >class MyThread1 (threading.Thread): | |
313 | > def run (self): | |
314 | > gdb.post_event(Writer("Hello ")) | |
315 | > | |
316 | >class MyThread2 (threading.Thread): | |
317 | > def run (self): | |
318 | > gdb.post_event(Writer("World\n")) | |
319 | > | |
320 | >MyThread1().start() | |
321 | >MyThread2().start() | |
322 | >end | |
323 | (@value{GDBP}) Hello World | |
324 | @end smallexample | |
325 | @end defun | |
326 | ||
327 | @findex gdb.write | |
328 | @defun gdb.write (string @r{[}, stream{]}) | |
329 | Print a string to @value{GDBN}'s paginated output stream. The | |
330 | optional @var{stream} determines the stream to print to. The default | |
331 | stream is @value{GDBN}'s standard output stream. Possible stream | |
332 | values are: | |
333 | ||
334 | @table @code | |
335 | @findex STDOUT | |
336 | @findex gdb.STDOUT | |
337 | @item gdb.STDOUT | |
338 | @value{GDBN}'s standard output stream. | |
339 | ||
340 | @findex STDERR | |
341 | @findex gdb.STDERR | |
342 | @item gdb.STDERR | |
343 | @value{GDBN}'s standard error stream. | |
344 | ||
345 | @findex STDLOG | |
346 | @findex gdb.STDLOG | |
347 | @item gdb.STDLOG | |
348 | @value{GDBN}'s log stream (@pxref{Logging Output}). | |
349 | @end table | |
350 | ||
351 | Writing to @code{sys.stdout} or @code{sys.stderr} will automatically | |
352 | call this function and will automatically direct the output to the | |
353 | relevant stream. | |
354 | @end defun | |
355 | ||
356 | @findex gdb.flush | |
357 | @defun gdb.flush () | |
358 | Flush the buffer of a @value{GDBN} paginated stream so that the | |
359 | contents are displayed immediately. @value{GDBN} will flush the | |
360 | contents of a stream automatically when it encounters a newline in the | |
361 | buffer. The optional @var{stream} determines the stream to flush. The | |
362 | default stream is @value{GDBN}'s standard output stream. Possible | |
363 | stream values are: | |
364 | ||
365 | @table @code | |
366 | @findex STDOUT | |
367 | @findex gdb.STDOUT | |
368 | @item gdb.STDOUT | |
369 | @value{GDBN}'s standard output stream. | |
370 | ||
371 | @findex STDERR | |
372 | @findex gdb.STDERR | |
373 | @item gdb.STDERR | |
374 | @value{GDBN}'s standard error stream. | |
375 | ||
376 | @findex STDLOG | |
377 | @findex gdb.STDLOG | |
378 | @item gdb.STDLOG | |
379 | @value{GDBN}'s log stream (@pxref{Logging Output}). | |
380 | ||
381 | @end table | |
382 | ||
383 | Flushing @code{sys.stdout} or @code{sys.stderr} will automatically | |
384 | call this function for the relevant stream. | |
385 | @end defun | |
386 | ||
387 | @findex gdb.target_charset | |
388 | @defun gdb.target_charset () | |
389 | Return the name of the current target character set (@pxref{Character | |
390 | Sets}). This differs from @code{gdb.parameter('target-charset')} in | |
391 | that @samp{auto} is never returned. | |
392 | @end defun | |
393 | ||
394 | @findex gdb.target_wide_charset | |
395 | @defun gdb.target_wide_charset () | |
396 | Return the name of the current target wide character set | |
397 | (@pxref{Character Sets}). This differs from | |
398 | @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is | |
399 | never returned. | |
400 | @end defun | |
401 | ||
402 | @findex gdb.solib_name | |
403 | @defun gdb.solib_name (address) | |
404 | Return the name of the shared library holding the given @var{address} | |
405 | as a string, or @code{None}. | |
406 | @end defun | |
407 | ||
408 | @findex gdb.decode_line | |
409 | @defun gdb.decode_line @r{[}expression@r{]} | |
410 | Return locations of the line specified by @var{expression}, or of the | |
411 | current line if no argument was given. This function returns a Python | |
412 | tuple containing two elements. The first element contains a string | |
413 | holding any unparsed section of @var{expression} (or @code{None} if | |
414 | the expression has been fully parsed). The second element contains | |
415 | either @code{None} or another tuple that contains all the locations | |
416 | that match the expression represented as @code{gdb.Symtab_and_line} | |
417 | objects (@pxref{Symbol Tables In Python}). If @var{expression} is | |
418 | provided, it is decoded the way that @value{GDBN}'s inbuilt | |
419 | @code{break} or @code{edit} commands do (@pxref{Specify Location}). | |
420 | @end defun | |
421 | ||
422 | @defun gdb.prompt_hook (current_prompt) | |
423 | @anchor{prompt_hook} | |
424 | ||
425 | If @var{prompt_hook} is callable, @value{GDBN} will call the method | |
426 | assigned to this operation before a prompt is displayed by | |
427 | @value{GDBN}. | |
428 | ||
429 | The parameter @code{current_prompt} contains the current @value{GDBN} | |
430 | prompt. This method must return a Python string, or @code{None}. If | |
431 | a string is returned, the @value{GDBN} prompt will be set to that | |
432 | string. If @code{None} is returned, @value{GDBN} will continue to use | |
433 | the current prompt. | |
434 | ||
435 | Some prompts cannot be substituted in @value{GDBN}. Secondary prompts | |
436 | such as those used by readline for command input, and annotation | |
437 | related prompts are prohibited from being changed. | |
438 | @end defun | |
439 | ||
440 | @node Exception Handling | |
441 | @subsubsection Exception Handling | |
442 | @cindex python exceptions | |
443 | @cindex exceptions, python | |
444 | ||
445 | When executing the @code{python} command, Python exceptions | |
446 | uncaught within the Python code are translated to calls to | |
447 | @value{GDBN} error-reporting mechanism. If the command that called | |
448 | @code{python} does not handle the error, @value{GDBN} will | |
449 | terminate it and print an error message containing the Python | |
450 | exception name, the associated value, and the Python call stack | |
451 | backtrace at the point where the exception was raised. Example: | |
452 | ||
453 | @smallexample | |
454 | (@value{GDBP}) python print foo | |
455 | Traceback (most recent call last): | |
456 | File "<string>", line 1, in <module> | |
457 | NameError: name 'foo' is not defined | |
458 | @end smallexample | |
459 | ||
460 | @value{GDBN} errors that happen in @value{GDBN} commands invoked by | |
461 | Python code are converted to Python exceptions. The type of the | |
462 | Python exception depends on the error. | |
463 | ||
464 | @ftable @code | |
465 | @item gdb.error | |
466 | This is the base class for most exceptions generated by @value{GDBN}. | |
467 | It is derived from @code{RuntimeError}, for compatibility with earlier | |
468 | versions of @value{GDBN}. | |
469 | ||
470 | If an error occurring in @value{GDBN} does not fit into some more | |
471 | specific category, then the generated exception will have this type. | |
472 | ||
473 | @item gdb.MemoryError | |
474 | This is a subclass of @code{gdb.error} which is thrown when an | |
475 | operation tried to access invalid memory in the inferior. | |
476 | ||
477 | @item KeyboardInterrupt | |
478 | User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination | |
479 | prompt) is translated to a Python @code{KeyboardInterrupt} exception. | |
480 | @end ftable | |
481 | ||
482 | In all cases, your exception handler will see the @value{GDBN} error | |
483 | message as its value and the Python call stack backtrace at the Python | |
484 | statement closest to where the @value{GDBN} error occured as the | |
485 | traceback. | |
486 | ||
487 | @findex gdb.GdbError | |
488 | When implementing @value{GDBN} commands in Python via @code{gdb.Command}, | |
489 | it is useful to be able to throw an exception that doesn't cause a | |
490 | traceback to be printed. For example, the user may have invoked the | |
491 | command incorrectly. Use the @code{gdb.GdbError} exception | |
492 | to handle this case. Example: | |
493 | ||
494 | @smallexample | |
495 | (gdb) python | |
496 | >class HelloWorld (gdb.Command): | |
497 | > """Greet the whole world.""" | |
498 | > def __init__ (self): | |
499 | > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) | |
500 | > def invoke (self, args, from_tty): | |
501 | > argv = gdb.string_to_argv (args) | |
502 | > if len (argv) != 0: | |
503 | > raise gdb.GdbError ("hello-world takes no arguments") | |
504 | > print "Hello, World!" | |
505 | >HelloWorld () | |
506 | >end | |
507 | (gdb) hello-world 42 | |
508 | hello-world takes no arguments | |
509 | @end smallexample | |
510 | ||
511 | @node Values From Inferior | |
512 | @subsubsection Values From Inferior | |
513 | @cindex values from inferior, with Python | |
514 | @cindex python, working with values from inferior | |
515 | ||
516 | @cindex @code{gdb.Value} | |
517 | @value{GDBN} provides values it obtains from the inferior program in | |
518 | an object of type @code{gdb.Value}. @value{GDBN} uses this object | |
519 | for its internal bookkeeping of the inferior's values, and for | |
520 | fetching values when necessary. | |
521 | ||
522 | Inferior values that are simple scalars can be used directly in | |
523 | Python expressions that are valid for the value's data type. Here's | |
524 | an example for an integer or floating-point value @code{some_val}: | |
525 | ||
526 | @smallexample | |
527 | bar = some_val + 2 | |
528 | @end smallexample | |
529 | ||
530 | @noindent | |
531 | As result of this, @code{bar} will also be a @code{gdb.Value} object | |
f7bd0f78 SC |
532 | whose values are of the same type as those of @code{some_val}. Valid |
533 | Python operations can also be performed on @code{gdb.Value} objects | |
534 | representing a @code{struct} or @code{class} object. For such cases, | |
535 | the overloaded operator (if present), is used to perform the operation. | |
536 | For example, if @code{val1} and @code{val2} are @code{gdb.Value} objects | |
537 | representing instances of a @code{class} which overloads the @code{+} | |
538 | operator, then one can use the @code{+} operator in their Python script | |
539 | as follows: | |
540 | ||
541 | @smallexample | |
542 | val3 = val1 + val2 | |
543 | @end smallexample | |
544 | ||
545 | @noindent | |
546 | The result of the operation @code{val3} is also a @code{gdb.Value} | |
547 | object corresponding to the value returned by the overloaded @code{+} | |
548 | operator. In general, overloaded operators are invoked for the | |
549 | following operations: @code{+} (binary addition), @code{-} (binary | |
550 | subtraction), @code{*} (multiplication), @code{/}, @code{%}, @code{<<}, | |
551 | @code{>>}, @code{|}, @code{&}, @code{^}. | |
329baa95 DE |
552 | |
553 | Inferior values that are structures or instances of some class can | |
554 | be accessed using the Python @dfn{dictionary syntax}. For example, if | |
555 | @code{some_val} is a @code{gdb.Value} instance holding a structure, you | |
556 | can access its @code{foo} element with: | |
557 | ||
558 | @smallexample | |
559 | bar = some_val['foo'] | |
560 | @end smallexample | |
561 | ||
562 | @cindex getting structure elements using gdb.Field objects as subscripts | |
563 | Again, @code{bar} will also be a @code{gdb.Value} object. Structure | |
564 | elements can also be accessed by using @code{gdb.Field} objects as | |
565 | subscripts (@pxref{Types In Python}, for more information on | |
566 | @code{gdb.Field} objects). For example, if @code{foo_field} is a | |
567 | @code{gdb.Field} object corresponding to element @code{foo} of the above | |
568 | structure, then @code{bar} can also be accessed as follows: | |
569 | ||
570 | @smallexample | |
571 | bar = some_val[foo_field] | |
572 | @end smallexample | |
573 | ||
574 | A @code{gdb.Value} that represents a function can be executed via | |
575 | inferior function call. Any arguments provided to the call must match | |
576 | the function's prototype, and must be provided in the order specified | |
577 | by that prototype. | |
578 | ||
579 | For example, @code{some_val} is a @code{gdb.Value} instance | |
580 | representing a function that takes two integers as arguments. To | |
581 | execute this function, call it like so: | |
582 | ||
583 | @smallexample | |
584 | result = some_val (10,20) | |
585 | @end smallexample | |
586 | ||
587 | Any values returned from a function call will be stored as a | |
588 | @code{gdb.Value}. | |
589 | ||
590 | The following attributes are provided: | |
591 | ||
592 | @defvar Value.address | |
593 | If this object is addressable, this read-only attribute holds a | |
594 | @code{gdb.Value} object representing the address. Otherwise, | |
595 | this attribute holds @code{None}. | |
596 | @end defvar | |
597 | ||
598 | @cindex optimized out value in Python | |
599 | @defvar Value.is_optimized_out | |
600 | This read-only boolean attribute is true if the compiler optimized out | |
601 | this value, thus it is not available for fetching from the inferior. | |
602 | @end defvar | |
603 | ||
604 | @defvar Value.type | |
605 | The type of this @code{gdb.Value}. The value of this attribute is a | |
606 | @code{gdb.Type} object (@pxref{Types In Python}). | |
607 | @end defvar | |
608 | ||
609 | @defvar Value.dynamic_type | |
610 | The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time | |
611 | type information (@acronym{RTTI}) to determine the dynamic type of the | |
612 | value. If this value is of class type, it will return the class in | |
613 | which the value is embedded, if any. If this value is of pointer or | |
614 | reference to a class type, it will compute the dynamic type of the | |
615 | referenced object, and return a pointer or reference to that type, | |
616 | respectively. In all other cases, it will return the value's static | |
617 | type. | |
618 | ||
619 | Note that this feature will only work when debugging a C@t{++} program | |
620 | that includes @acronym{RTTI} for the object in question. Otherwise, | |
621 | it will just return the static type of the value as in @kbd{ptype foo} | |
622 | (@pxref{Symbols, ptype}). | |
623 | @end defvar | |
624 | ||
625 | @defvar Value.is_lazy | |
626 | The value of this read-only boolean attribute is @code{True} if this | |
627 | @code{gdb.Value} has not yet been fetched from the inferior. | |
628 | @value{GDBN} does not fetch values until necessary, for efficiency. | |
629 | For example: | |
630 | ||
631 | @smallexample | |
632 | myval = gdb.parse_and_eval ('somevar') | |
633 | @end smallexample | |
634 | ||
635 | The value of @code{somevar} is not fetched at this time. It will be | |
636 | fetched when the value is needed, or when the @code{fetch_lazy} | |
637 | method is invoked. | |
638 | @end defvar | |
639 | ||
640 | The following methods are provided: | |
641 | ||
642 | @defun Value.__init__ (@var{val}) | |
643 | Many Python values can be converted directly to a @code{gdb.Value} via | |
644 | this object initializer. Specifically: | |
645 | ||
646 | @table @asis | |
647 | @item Python boolean | |
648 | A Python boolean is converted to the boolean type from the current | |
649 | language. | |
650 | ||
651 | @item Python integer | |
652 | A Python integer is converted to the C @code{long} type for the | |
653 | current architecture. | |
654 | ||
655 | @item Python long | |
656 | A Python long is converted to the C @code{long long} type for the | |
657 | current architecture. | |
658 | ||
659 | @item Python float | |
660 | A Python float is converted to the C @code{double} type for the | |
661 | current architecture. | |
662 | ||
663 | @item Python string | |
b3ce5e5f DE |
664 | A Python string is converted to a target string in the current target |
665 | language using the current target encoding. | |
666 | If a character cannot be represented in the current target encoding, | |
667 | then an exception is thrown. | |
329baa95 DE |
668 | |
669 | @item @code{gdb.Value} | |
670 | If @code{val} is a @code{gdb.Value}, then a copy of the value is made. | |
671 | ||
672 | @item @code{gdb.LazyString} | |
673 | If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In | |
674 | Python}), then the lazy string's @code{value} method is called, and | |
675 | its result is used. | |
676 | @end table | |
677 | @end defun | |
678 | ||
679 | @defun Value.cast (type) | |
680 | Return a new instance of @code{gdb.Value} that is the result of | |
681 | casting this instance to the type described by @var{type}, which must | |
682 | be a @code{gdb.Type} object. If the cast cannot be performed for some | |
683 | reason, this method throws an exception. | |
684 | @end defun | |
685 | ||
686 | @defun Value.dereference () | |
687 | For pointer data types, this method returns a new @code{gdb.Value} object | |
688 | whose contents is the object pointed to by the pointer. For example, if | |
689 | @code{foo} is a C pointer to an @code{int}, declared in your C program as | |
690 | ||
691 | @smallexample | |
692 | int *foo; | |
693 | @end smallexample | |
694 | ||
695 | @noindent | |
696 | then you can use the corresponding @code{gdb.Value} to access what | |
697 | @code{foo} points to like this: | |
698 | ||
699 | @smallexample | |
700 | bar = foo.dereference () | |
701 | @end smallexample | |
702 | ||
703 | The result @code{bar} will be a @code{gdb.Value} object holding the | |
704 | value pointed to by @code{foo}. | |
705 | ||
706 | A similar function @code{Value.referenced_value} exists which also | |
707 | returns @code{gdb.Value} objects corresonding to the values pointed to | |
708 | by pointer values (and additionally, values referenced by reference | |
709 | values). However, the behavior of @code{Value.dereference} | |
710 | differs from @code{Value.referenced_value} by the fact that the | |
711 | behavior of @code{Value.dereference} is identical to applying the C | |
712 | unary operator @code{*} on a given value. For example, consider a | |
713 | reference to a pointer @code{ptrref}, declared in your C@t{++} program | |
714 | as | |
715 | ||
716 | @smallexample | |
717 | typedef int *intptr; | |
718 | ... | |
719 | int val = 10; | |
720 | intptr ptr = &val; | |
721 | intptr &ptrref = ptr; | |
722 | @end smallexample | |
723 | ||
724 | Though @code{ptrref} is a reference value, one can apply the method | |
725 | @code{Value.dereference} to the @code{gdb.Value} object corresponding | |
726 | to it and obtain a @code{gdb.Value} which is identical to that | |
727 | corresponding to @code{val}. However, if you apply the method | |
728 | @code{Value.referenced_value}, the result would be a @code{gdb.Value} | |
729 | object identical to that corresponding to @code{ptr}. | |
730 | ||
731 | @smallexample | |
732 | py_ptrref = gdb.parse_and_eval ("ptrref") | |
733 | py_val = py_ptrref.dereference () | |
734 | py_ptr = py_ptrref.referenced_value () | |
735 | @end smallexample | |
736 | ||
737 | The @code{gdb.Value} object @code{py_val} is identical to that | |
738 | corresponding to @code{val}, and @code{py_ptr} is identical to that | |
739 | corresponding to @code{ptr}. In general, @code{Value.dereference} can | |
740 | be applied whenever the C unary operator @code{*} can be applied | |
741 | to the corresponding C value. For those cases where applying both | |
742 | @code{Value.dereference} and @code{Value.referenced_value} is allowed, | |
743 | the results obtained need not be identical (as we have seen in the above | |
744 | example). The results are however identical when applied on | |
745 | @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value} | |
746 | objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program. | |
747 | @end defun | |
748 | ||
749 | @defun Value.referenced_value () | |
750 | For pointer or reference data types, this method returns a new | |
751 | @code{gdb.Value} object corresponding to the value referenced by the | |
752 | pointer/reference value. For pointer data types, | |
753 | @code{Value.dereference} and @code{Value.referenced_value} produce | |
754 | identical results. The difference between these methods is that | |
755 | @code{Value.dereference} cannot get the values referenced by reference | |
756 | values. For example, consider a reference to an @code{int}, declared | |
757 | in your C@t{++} program as | |
758 | ||
759 | @smallexample | |
760 | int val = 10; | |
761 | int &ref = val; | |
762 | @end smallexample | |
763 | ||
764 | @noindent | |
765 | then applying @code{Value.dereference} to the @code{gdb.Value} object | |
766 | corresponding to @code{ref} will result in an error, while applying | |
767 | @code{Value.referenced_value} will result in a @code{gdb.Value} object | |
768 | identical to that corresponding to @code{val}. | |
769 | ||
770 | @smallexample | |
771 | py_ref = gdb.parse_and_eval ("ref") | |
772 | er_ref = py_ref.dereference () # Results in error | |
773 | py_val = py_ref.referenced_value () # Returns the referenced value | |
774 | @end smallexample | |
775 | ||
776 | The @code{gdb.Value} object @code{py_val} is identical to that | |
777 | corresponding to @code{val}. | |
778 | @end defun | |
779 | ||
780 | @defun Value.dynamic_cast (type) | |
781 | Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast} | |
782 | operator were used. Consult a C@t{++} reference for details. | |
783 | @end defun | |
784 | ||
785 | @defun Value.reinterpret_cast (type) | |
786 | Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast} | |
787 | operator were used. Consult a C@t{++} reference for details. | |
788 | @end defun | |
789 | ||
790 | @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]}) | |
791 | If this @code{gdb.Value} represents a string, then this method | |
792 | converts the contents to a Python string. Otherwise, this method will | |
793 | throw an exception. | |
794 | ||
b3ce5e5f DE |
795 | Values are interpreted as strings according to the rules of the |
796 | current language. If the optional length argument is given, the | |
797 | string will be converted to that length, and will include any embedded | |
798 | zeroes that the string may contain. Otherwise, for languages | |
799 | where the string is zero-terminated, the entire string will be | |
800 | converted. | |
329baa95 | 801 | |
b3ce5e5f DE |
802 | For example, in C-like languages, a value is a string if it is a pointer |
803 | to or an array of characters or ints of type @code{wchar_t}, @code{char16_t}, | |
804 | or @code{char32_t}. | |
329baa95 DE |
805 | |
806 | If the optional @var{encoding} argument is given, it must be a string | |
807 | naming the encoding of the string in the @code{gdb.Value}, such as | |
808 | @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts | |
809 | the same encodings as the corresponding argument to Python's | |
810 | @code{string.decode} method, and the Python codec machinery will be used | |
811 | to convert the string. If @var{encoding} is not given, or if | |
812 | @var{encoding} is the empty string, then either the @code{target-charset} | |
813 | (@pxref{Character Sets}) will be used, or a language-specific encoding | |
814 | will be used, if the current language is able to supply one. | |
815 | ||
816 | The optional @var{errors} argument is the same as the corresponding | |
817 | argument to Python's @code{string.decode} method. | |
818 | ||
819 | If the optional @var{length} argument is given, the string will be | |
820 | fetched and converted to the given length. | |
821 | @end defun | |
822 | ||
823 | @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]}) | |
824 | If this @code{gdb.Value} represents a string, then this method | |
825 | converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings | |
826 | In Python}). Otherwise, this method will throw an exception. | |
827 | ||
828 | If the optional @var{encoding} argument is given, it must be a string | |
829 | naming the encoding of the @code{gdb.LazyString}. Some examples are: | |
830 | @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the | |
831 | @var{encoding} argument is an encoding that @value{GDBN} does | |
832 | recognize, @value{GDBN} will raise an error. | |
833 | ||
834 | When a lazy string is printed, the @value{GDBN} encoding machinery is | |
835 | used to convert the string during printing. If the optional | |
836 | @var{encoding} argument is not provided, or is an empty string, | |
837 | @value{GDBN} will automatically select the encoding most suitable for | |
838 | the string type. For further information on encoding in @value{GDBN} | |
839 | please see @ref{Character Sets}. | |
840 | ||
841 | If the optional @var{length} argument is given, the string will be | |
842 | fetched and encoded to the length of characters specified. If | |
843 | the @var{length} argument is not provided, the string will be fetched | |
844 | and encoded until a null of appropriate width is found. | |
845 | @end defun | |
846 | ||
847 | @defun Value.fetch_lazy () | |
848 | If the @code{gdb.Value} object is currently a lazy value | |
849 | (@code{gdb.Value.is_lazy} is @code{True}), then the value is | |
850 | fetched from the inferior. Any errors that occur in the process | |
851 | will produce a Python exception. | |
852 | ||
853 | If the @code{gdb.Value} object is not a lazy value, this method | |
854 | has no effect. | |
855 | ||
856 | This method does not return a value. | |
857 | @end defun | |
858 | ||
859 | ||
860 | @node Types In Python | |
861 | @subsubsection Types In Python | |
862 | @cindex types in Python | |
863 | @cindex Python, working with types | |
864 | ||
865 | @tindex gdb.Type | |
866 | @value{GDBN} represents types from the inferior using the class | |
867 | @code{gdb.Type}. | |
868 | ||
869 | The following type-related functions are available in the @code{gdb} | |
870 | module: | |
871 | ||
872 | @findex gdb.lookup_type | |
873 | @defun gdb.lookup_type (name @r{[}, block@r{]}) | |
874 | This function looks up a type by name. @var{name} is the name of the | |
875 | type to look up. It must be a string. | |
876 | ||
877 | If @var{block} is given, then @var{name} is looked up in that scope. | |
878 | Otherwise, it is searched for globally. | |
879 | ||
880 | Ordinarily, this function will return an instance of @code{gdb.Type}. | |
881 | If the named type cannot be found, it will throw an exception. | |
882 | @end defun | |
883 | ||
884 | If the type is a structure or class type, or an enum type, the fields | |
885 | of that type can be accessed using the Python @dfn{dictionary syntax}. | |
886 | For example, if @code{some_type} is a @code{gdb.Type} instance holding | |
887 | a structure type, you can access its @code{foo} field with: | |
888 | ||
889 | @smallexample | |
890 | bar = some_type['foo'] | |
891 | @end smallexample | |
892 | ||
893 | @code{bar} will be a @code{gdb.Field} object; see below under the | |
894 | description of the @code{Type.fields} method for a description of the | |
895 | @code{gdb.Field} class. | |
896 | ||
897 | An instance of @code{Type} has the following attributes: | |
898 | ||
899 | @defvar Type.code | |
900 | The type code for this type. The type code will be one of the | |
901 | @code{TYPE_CODE_} constants defined below. | |
902 | @end defvar | |
903 | ||
904 | @defvar Type.name | |
905 | The name of this type. If this type has no name, then @code{None} | |
906 | is returned. | |
907 | @end defvar | |
908 | ||
909 | @defvar Type.sizeof | |
910 | The size of this type, in target @code{char} units. Usually, a | |
911 | target's @code{char} type will be an 8-bit byte. However, on some | |
912 | unusual platforms, this type may have a different size. | |
913 | @end defvar | |
914 | ||
915 | @defvar Type.tag | |
916 | The tag name for this type. The tag name is the name after | |
917 | @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all | |
918 | languages have this concept. If this type has no tag name, then | |
919 | @code{None} is returned. | |
920 | @end defvar | |
921 | ||
922 | The following methods are provided: | |
923 | ||
924 | @defun Type.fields () | |
925 | For structure and union types, this method returns the fields. Range | |
926 | types have two fields, the minimum and maximum values. Enum types | |
927 | have one field per enum constant. Function and method types have one | |
928 | field per parameter. The base types of C@t{++} classes are also | |
929 | represented as fields. If the type has no fields, or does not fit | |
930 | into one of these categories, an empty sequence will be returned. | |
931 | ||
932 | Each field is a @code{gdb.Field} object, with some pre-defined attributes: | |
933 | @table @code | |
934 | @item bitpos | |
935 | This attribute is not available for @code{enum} or @code{static} | |
936 | (as in C@t{++} or Java) fields. The value is the position, counting | |
937 | in bits, from the start of the containing type. | |
938 | ||
939 | @item enumval | |
940 | This attribute is only available for @code{enum} fields, and its value | |
941 | is the enumeration member's integer representation. | |
942 | ||
943 | @item name | |
944 | The name of the field, or @code{None} for anonymous fields. | |
945 | ||
946 | @item artificial | |
947 | This is @code{True} if the field is artificial, usually meaning that | |
948 | it was provided by the compiler and not the user. This attribute is | |
949 | always provided, and is @code{False} if the field is not artificial. | |
950 | ||
951 | @item is_base_class | |
952 | This is @code{True} if the field represents a base class of a C@t{++} | |
953 | structure. This attribute is always provided, and is @code{False} | |
954 | if the field is not a base class of the type that is the argument of | |
955 | @code{fields}, or if that type was not a C@t{++} class. | |
956 | ||
957 | @item bitsize | |
958 | If the field is packed, or is a bitfield, then this will have a | |
959 | non-zero value, which is the size of the field in bits. Otherwise, | |
960 | this will be zero; in this case the field's size is given by its type. | |
961 | ||
962 | @item type | |
963 | The type of the field. This is usually an instance of @code{Type}, | |
964 | but it can be @code{None} in some situations. | |
965 | ||
966 | @item parent_type | |
967 | The type which contains this field. This is an instance of | |
968 | @code{gdb.Type}. | |
969 | @end table | |
970 | @end defun | |
971 | ||
972 | @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]}) | |
973 | Return a new @code{gdb.Type} object which represents an array of this | |
974 | type. If one argument is given, it is the inclusive upper bound of | |
975 | the array; in this case the lower bound is zero. If two arguments are | |
976 | given, the first argument is the lower bound of the array, and the | |
977 | second argument is the upper bound of the array. An array's length | |
978 | must not be negative, but the bounds can be. | |
979 | @end defun | |
980 | ||
981 | @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]}) | |
982 | Return a new @code{gdb.Type} object which represents a vector of this | |
983 | type. If one argument is given, it is the inclusive upper bound of | |
984 | the vector; in this case the lower bound is zero. If two arguments are | |
985 | given, the first argument is the lower bound of the vector, and the | |
986 | second argument is the upper bound of the vector. A vector's length | |
987 | must not be negative, but the bounds can be. | |
988 | ||
989 | The difference between an @code{array} and a @code{vector} is that | |
990 | arrays behave like in C: when used in expressions they decay to a pointer | |
991 | to the first element whereas vectors are treated as first class values. | |
992 | @end defun | |
993 | ||
994 | @defun Type.const () | |
995 | Return a new @code{gdb.Type} object which represents a | |
996 | @code{const}-qualified variant of this type. | |
997 | @end defun | |
998 | ||
999 | @defun Type.volatile () | |
1000 | Return a new @code{gdb.Type} object which represents a | |
1001 | @code{volatile}-qualified variant of this type. | |
1002 | @end defun | |
1003 | ||
1004 | @defun Type.unqualified () | |
1005 | Return a new @code{gdb.Type} object which represents an unqualified | |
1006 | variant of this type. That is, the result is neither @code{const} nor | |
1007 | @code{volatile}. | |
1008 | @end defun | |
1009 | ||
1010 | @defun Type.range () | |
1011 | Return a Python @code{Tuple} object that contains two elements: the | |
1012 | low bound of the argument type and the high bound of that type. If | |
1013 | the type does not have a range, @value{GDBN} will raise a | |
1014 | @code{gdb.error} exception (@pxref{Exception Handling}). | |
1015 | @end defun | |
1016 | ||
1017 | @defun Type.reference () | |
1018 | Return a new @code{gdb.Type} object which represents a reference to this | |
1019 | type. | |
1020 | @end defun | |
1021 | ||
1022 | @defun Type.pointer () | |
1023 | Return a new @code{gdb.Type} object which represents a pointer to this | |
1024 | type. | |
1025 | @end defun | |
1026 | ||
1027 | @defun Type.strip_typedefs () | |
1028 | Return a new @code{gdb.Type} that represents the real type, | |
1029 | after removing all layers of typedefs. | |
1030 | @end defun | |
1031 | ||
1032 | @defun Type.target () | |
1033 | Return a new @code{gdb.Type} object which represents the target type | |
1034 | of this type. | |
1035 | ||
1036 | For a pointer type, the target type is the type of the pointed-to | |
1037 | object. For an array type (meaning C-like arrays), the target type is | |
1038 | the type of the elements of the array. For a function or method type, | |
1039 | the target type is the type of the return value. For a complex type, | |
1040 | the target type is the type of the elements. For a typedef, the | |
1041 | target type is the aliased type. | |
1042 | ||
1043 | If the type does not have a target, this method will throw an | |
1044 | exception. | |
1045 | @end defun | |
1046 | ||
1047 | @defun Type.template_argument (n @r{[}, block@r{]}) | |
1048 | If this @code{gdb.Type} is an instantiation of a template, this will | |
1049 | return a new @code{gdb.Type} which represents the type of the | |
1050 | @var{n}th template argument. | |
1051 | ||
1052 | If this @code{gdb.Type} is not a template type, this will throw an | |
1053 | exception. Ordinarily, only C@t{++} code will have template types. | |
1054 | ||
1055 | If @var{block} is given, then @var{name} is looked up in that scope. | |
1056 | Otherwise, it is searched for globally. | |
1057 | @end defun | |
1058 | ||
1059 | ||
1060 | Each type has a code, which indicates what category this type falls | |
1061 | into. The available type categories are represented by constants | |
1062 | defined in the @code{gdb} module: | |
1063 | ||
b3ce5e5f DE |
1064 | @vtable @code |
1065 | @vindex TYPE_CODE_PTR | |
329baa95 DE |
1066 | @item gdb.TYPE_CODE_PTR |
1067 | The type is a pointer. | |
1068 | ||
b3ce5e5f | 1069 | @vindex TYPE_CODE_ARRAY |
329baa95 DE |
1070 | @item gdb.TYPE_CODE_ARRAY |
1071 | The type is an array. | |
1072 | ||
b3ce5e5f | 1073 | @vindex TYPE_CODE_STRUCT |
329baa95 DE |
1074 | @item gdb.TYPE_CODE_STRUCT |
1075 | The type is a structure. | |
1076 | ||
b3ce5e5f | 1077 | @vindex TYPE_CODE_UNION |
329baa95 DE |
1078 | @item gdb.TYPE_CODE_UNION |
1079 | The type is a union. | |
1080 | ||
b3ce5e5f | 1081 | @vindex TYPE_CODE_ENUM |
329baa95 DE |
1082 | @item gdb.TYPE_CODE_ENUM |
1083 | The type is an enum. | |
1084 | ||
b3ce5e5f | 1085 | @vindex TYPE_CODE_FLAGS |
329baa95 DE |
1086 | @item gdb.TYPE_CODE_FLAGS |
1087 | A bit flags type, used for things such as status registers. | |
1088 | ||
b3ce5e5f | 1089 | @vindex TYPE_CODE_FUNC |
329baa95 DE |
1090 | @item gdb.TYPE_CODE_FUNC |
1091 | The type is a function. | |
1092 | ||
b3ce5e5f | 1093 | @vindex TYPE_CODE_INT |
329baa95 DE |
1094 | @item gdb.TYPE_CODE_INT |
1095 | The type is an integer type. | |
1096 | ||
b3ce5e5f | 1097 | @vindex TYPE_CODE_FLT |
329baa95 DE |
1098 | @item gdb.TYPE_CODE_FLT |
1099 | A floating point type. | |
1100 | ||
b3ce5e5f | 1101 | @vindex TYPE_CODE_VOID |
329baa95 DE |
1102 | @item gdb.TYPE_CODE_VOID |
1103 | The special type @code{void}. | |
1104 | ||
b3ce5e5f | 1105 | @vindex TYPE_CODE_SET |
329baa95 DE |
1106 | @item gdb.TYPE_CODE_SET |
1107 | A Pascal set type. | |
1108 | ||
b3ce5e5f | 1109 | @vindex TYPE_CODE_RANGE |
329baa95 DE |
1110 | @item gdb.TYPE_CODE_RANGE |
1111 | A range type, that is, an integer type with bounds. | |
1112 | ||
b3ce5e5f | 1113 | @vindex TYPE_CODE_STRING |
329baa95 DE |
1114 | @item gdb.TYPE_CODE_STRING |
1115 | A string type. Note that this is only used for certain languages with | |
1116 | language-defined string types; C strings are not represented this way. | |
1117 | ||
b3ce5e5f | 1118 | @vindex TYPE_CODE_BITSTRING |
329baa95 DE |
1119 | @item gdb.TYPE_CODE_BITSTRING |
1120 | A string of bits. It is deprecated. | |
1121 | ||
b3ce5e5f | 1122 | @vindex TYPE_CODE_ERROR |
329baa95 DE |
1123 | @item gdb.TYPE_CODE_ERROR |
1124 | An unknown or erroneous type. | |
1125 | ||
b3ce5e5f | 1126 | @vindex TYPE_CODE_METHOD |
329baa95 DE |
1127 | @item gdb.TYPE_CODE_METHOD |
1128 | A method type, as found in C@t{++} or Java. | |
1129 | ||
b3ce5e5f | 1130 | @vindex TYPE_CODE_METHODPTR |
329baa95 DE |
1131 | @item gdb.TYPE_CODE_METHODPTR |
1132 | A pointer-to-member-function. | |
1133 | ||
b3ce5e5f | 1134 | @vindex TYPE_CODE_MEMBERPTR |
329baa95 DE |
1135 | @item gdb.TYPE_CODE_MEMBERPTR |
1136 | A pointer-to-member. | |
1137 | ||
b3ce5e5f | 1138 | @vindex TYPE_CODE_REF |
329baa95 DE |
1139 | @item gdb.TYPE_CODE_REF |
1140 | A reference type. | |
1141 | ||
b3ce5e5f | 1142 | @vindex TYPE_CODE_CHAR |
329baa95 DE |
1143 | @item gdb.TYPE_CODE_CHAR |
1144 | A character type. | |
1145 | ||
b3ce5e5f | 1146 | @vindex TYPE_CODE_BOOL |
329baa95 DE |
1147 | @item gdb.TYPE_CODE_BOOL |
1148 | A boolean type. | |
1149 | ||
b3ce5e5f | 1150 | @vindex TYPE_CODE_COMPLEX |
329baa95 DE |
1151 | @item gdb.TYPE_CODE_COMPLEX |
1152 | A complex float type. | |
1153 | ||
b3ce5e5f | 1154 | @vindex TYPE_CODE_TYPEDEF |
329baa95 DE |
1155 | @item gdb.TYPE_CODE_TYPEDEF |
1156 | A typedef to some other type. | |
1157 | ||
b3ce5e5f | 1158 | @vindex TYPE_CODE_NAMESPACE |
329baa95 DE |
1159 | @item gdb.TYPE_CODE_NAMESPACE |
1160 | A C@t{++} namespace. | |
1161 | ||
b3ce5e5f | 1162 | @vindex TYPE_CODE_DECFLOAT |
329baa95 DE |
1163 | @item gdb.TYPE_CODE_DECFLOAT |
1164 | A decimal floating point type. | |
1165 | ||
b3ce5e5f | 1166 | @vindex TYPE_CODE_INTERNAL_FUNCTION |
329baa95 DE |
1167 | @item gdb.TYPE_CODE_INTERNAL_FUNCTION |
1168 | A function internal to @value{GDBN}. This is the type used to represent | |
1169 | convenience functions. | |
b3ce5e5f | 1170 | @end vtable |
329baa95 DE |
1171 | |
1172 | Further support for types is provided in the @code{gdb.types} | |
1173 | Python module (@pxref{gdb.types}). | |
1174 | ||
1175 | @node Pretty Printing API | |
1176 | @subsubsection Pretty Printing API | |
b3ce5e5f | 1177 | @cindex python pretty printing api |
329baa95 DE |
1178 | |
1179 | An example output is provided (@pxref{Pretty Printing}). | |
1180 | ||
1181 | A pretty-printer is just an object that holds a value and implements a | |
1182 | specific interface, defined here. | |
1183 | ||
1184 | @defun pretty_printer.children (self) | |
1185 | @value{GDBN} will call this method on a pretty-printer to compute the | |
1186 | children of the pretty-printer's value. | |
1187 | ||
1188 | This method must return an object conforming to the Python iterator | |
1189 | protocol. Each item returned by the iterator must be a tuple holding | |
1190 | two elements. The first element is the ``name'' of the child; the | |
1191 | second element is the child's value. The value can be any Python | |
1192 | object which is convertible to a @value{GDBN} value. | |
1193 | ||
1194 | This method is optional. If it does not exist, @value{GDBN} will act | |
1195 | as though the value has no children. | |
1196 | @end defun | |
1197 | ||
1198 | @defun pretty_printer.display_hint (self) | |
1199 | The CLI may call this method and use its result to change the | |
1200 | formatting of a value. The result will also be supplied to an MI | |
1201 | consumer as a @samp{displayhint} attribute of the variable being | |
1202 | printed. | |
1203 | ||
1204 | This method is optional. If it does exist, this method must return a | |
1205 | string. | |
1206 | ||
1207 | Some display hints are predefined by @value{GDBN}: | |
1208 | ||
1209 | @table @samp | |
1210 | @item array | |
1211 | Indicate that the object being printed is ``array-like''. The CLI | |
1212 | uses this to respect parameters such as @code{set print elements} and | |
1213 | @code{set print array}. | |
1214 | ||
1215 | @item map | |
1216 | Indicate that the object being printed is ``map-like'', and that the | |
1217 | children of this value can be assumed to alternate between keys and | |
1218 | values. | |
1219 | ||
1220 | @item string | |
1221 | Indicate that the object being printed is ``string-like''. If the | |
1222 | printer's @code{to_string} method returns a Python string of some | |
1223 | kind, then @value{GDBN} will call its internal language-specific | |
1224 | string-printing function to format the string. For the CLI this means | |
1225 | adding quotation marks, possibly escaping some characters, respecting | |
1226 | @code{set print elements}, and the like. | |
1227 | @end table | |
1228 | @end defun | |
1229 | ||
1230 | @defun pretty_printer.to_string (self) | |
1231 | @value{GDBN} will call this method to display the string | |
1232 | representation of the value passed to the object's constructor. | |
1233 | ||
1234 | When printing from the CLI, if the @code{to_string} method exists, | |
1235 | then @value{GDBN} will prepend its result to the values returned by | |
1236 | @code{children}. Exactly how this formatting is done is dependent on | |
1237 | the display hint, and may change as more hints are added. Also, | |
1238 | depending on the print settings (@pxref{Print Settings}), the CLI may | |
1239 | print just the result of @code{to_string} in a stack trace, omitting | |
1240 | the result of @code{children}. | |
1241 | ||
1242 | If this method returns a string, it is printed verbatim. | |
1243 | ||
1244 | Otherwise, if this method returns an instance of @code{gdb.Value}, | |
1245 | then @value{GDBN} prints this value. This may result in a call to | |
1246 | another pretty-printer. | |
1247 | ||
1248 | If instead the method returns a Python value which is convertible to a | |
1249 | @code{gdb.Value}, then @value{GDBN} performs the conversion and prints | |
1250 | the resulting value. Again, this may result in a call to another | |
1251 | pretty-printer. Python scalars (integers, floats, and booleans) and | |
1252 | strings are convertible to @code{gdb.Value}; other types are not. | |
1253 | ||
1254 | Finally, if this method returns @code{None} then no further operations | |
1255 | are peformed in this method and nothing is printed. | |
1256 | ||
1257 | If the result is not one of these types, an exception is raised. | |
1258 | @end defun | |
1259 | ||
1260 | @value{GDBN} provides a function which can be used to look up the | |
1261 | default pretty-printer for a @code{gdb.Value}: | |
1262 | ||
1263 | @findex gdb.default_visualizer | |
1264 | @defun gdb.default_visualizer (value) | |
1265 | This function takes a @code{gdb.Value} object as an argument. If a | |
1266 | pretty-printer for this value exists, then it is returned. If no such | |
1267 | printer exists, then this returns @code{None}. | |
1268 | @end defun | |
1269 | ||
1270 | @node Selecting Pretty-Printers | |
1271 | @subsubsection Selecting Pretty-Printers | |
b3ce5e5f | 1272 | @cindex selecting python pretty-printers |
329baa95 DE |
1273 | |
1274 | The Python list @code{gdb.pretty_printers} contains an array of | |
1275 | functions or callable objects that have been registered via addition | |
1276 | as a pretty-printer. Printers in this list are called @code{global} | |
1277 | printers, they're available when debugging all inferiors. | |
1278 | Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute. | |
1279 | Each @code{gdb.Objfile} also contains a @code{pretty_printers} | |
1280 | attribute. | |
1281 | ||
1282 | Each function on these lists is passed a single @code{gdb.Value} | |
1283 | argument and should return a pretty-printer object conforming to the | |
1284 | interface definition above (@pxref{Pretty Printing API}). If a function | |
1285 | cannot create a pretty-printer for the value, it should return | |
1286 | @code{None}. | |
1287 | ||
1288 | @value{GDBN} first checks the @code{pretty_printers} attribute of each | |
1289 | @code{gdb.Objfile} in the current program space and iteratively calls | |
1290 | each enabled lookup routine in the list for that @code{gdb.Objfile} | |
1291 | until it receives a pretty-printer object. | |
1292 | If no pretty-printer is found in the objfile lists, @value{GDBN} then | |
1293 | searches the pretty-printer list of the current program space, | |
1294 | calling each enabled function until an object is returned. | |
1295 | After these lists have been exhausted, it tries the global | |
1296 | @code{gdb.pretty_printers} list, again calling each enabled function until an | |
1297 | object is returned. | |
1298 | ||
1299 | The order in which the objfiles are searched is not specified. For a | |
1300 | given list, functions are always invoked from the head of the list, | |
1301 | and iterated over sequentially until the end of the list, or a printer | |
1302 | object is returned. | |
1303 | ||
1304 | For various reasons a pretty-printer may not work. | |
1305 | For example, the underlying data structure may have changed and | |
1306 | the pretty-printer is out of date. | |
1307 | ||
1308 | The consequences of a broken pretty-printer are severe enough that | |
1309 | @value{GDBN} provides support for enabling and disabling individual | |
1310 | printers. For example, if @code{print frame-arguments} is on, | |
1311 | a backtrace can become highly illegible if any argument is printed | |
1312 | with a broken printer. | |
1313 | ||
1314 | Pretty-printers are enabled and disabled by attaching an @code{enabled} | |
1315 | attribute to the registered function or callable object. If this attribute | |
1316 | is present and its value is @code{False}, the printer is disabled, otherwise | |
1317 | the printer is enabled. | |
1318 | ||
1319 | @node Writing a Pretty-Printer | |
1320 | @subsubsection Writing a Pretty-Printer | |
1321 | @cindex writing a pretty-printer | |
1322 | ||
1323 | A pretty-printer consists of two parts: a lookup function to detect | |
1324 | if the type is supported, and the printer itself. | |
1325 | ||
1326 | Here is an example showing how a @code{std::string} printer might be | |
1327 | written. @xref{Pretty Printing API}, for details on the API this class | |
1328 | must provide. | |
1329 | ||
1330 | @smallexample | |
1331 | class StdStringPrinter(object): | |
1332 | "Print a std::string" | |
1333 | ||
1334 | def __init__(self, val): | |
1335 | self.val = val | |
1336 | ||
1337 | def to_string(self): | |
1338 | return self.val['_M_dataplus']['_M_p'] | |
1339 | ||
1340 | def display_hint(self): | |
1341 | return 'string' | |
1342 | @end smallexample | |
1343 | ||
1344 | And here is an example showing how a lookup function for the printer | |
1345 | example above might be written. | |
1346 | ||
1347 | @smallexample | |
1348 | def str_lookup_function(val): | |
1349 | lookup_tag = val.type.tag | |
1350 | if lookup_tag == None: | |
1351 | return None | |
1352 | regex = re.compile("^std::basic_string<char,.*>$") | |
1353 | if regex.match(lookup_tag): | |
1354 | return StdStringPrinter(val) | |
1355 | return None | |
1356 | @end smallexample | |
1357 | ||
1358 | The example lookup function extracts the value's type, and attempts to | |
1359 | match it to a type that it can pretty-print. If it is a type the | |
1360 | printer can pretty-print, it will return a printer object. If not, it | |
1361 | returns @code{None}. | |
1362 | ||
1363 | We recommend that you put your core pretty-printers into a Python | |
1364 | package. If your pretty-printers are for use with a library, we | |
1365 | further recommend embedding a version number into the package name. | |
1366 | This practice will enable @value{GDBN} to load multiple versions of | |
1367 | your pretty-printers at the same time, because they will have | |
1368 | different names. | |
1369 | ||
1370 | You should write auto-loaded code (@pxref{Python Auto-loading}) such that it | |
1371 | can be evaluated multiple times without changing its meaning. An | |
1372 | ideal auto-load file will consist solely of @code{import}s of your | |
1373 | printer modules, followed by a call to a register pretty-printers with | |
1374 | the current objfile. | |
1375 | ||
1376 | Taken as a whole, this approach will scale nicely to multiple | |
1377 | inferiors, each potentially using a different library version. | |
1378 | Embedding a version number in the Python package name will ensure that | |
1379 | @value{GDBN} is able to load both sets of printers simultaneously. | |
1380 | Then, because the search for pretty-printers is done by objfile, and | |
1381 | because your auto-loaded code took care to register your library's | |
1382 | printers with a specific objfile, @value{GDBN} will find the correct | |
1383 | printers for the specific version of the library used by each | |
1384 | inferior. | |
1385 | ||
1386 | To continue the @code{std::string} example (@pxref{Pretty Printing API}), | |
1387 | this code might appear in @code{gdb.libstdcxx.v6}: | |
1388 | ||
1389 | @smallexample | |
1390 | def register_printers(objfile): | |
1391 | objfile.pretty_printers.append(str_lookup_function) | |
1392 | @end smallexample | |
1393 | ||
1394 | @noindent | |
1395 | And then the corresponding contents of the auto-load file would be: | |
1396 | ||
1397 | @smallexample | |
1398 | import gdb.libstdcxx.v6 | |
1399 | gdb.libstdcxx.v6.register_printers(gdb.current_objfile()) | |
1400 | @end smallexample | |
1401 | ||
1402 | The previous example illustrates a basic pretty-printer. | |
1403 | There are a few things that can be improved on. | |
1404 | The printer doesn't have a name, making it hard to identify in a | |
1405 | list of installed printers. The lookup function has a name, but | |
1406 | lookup functions can have arbitrary, even identical, names. | |
1407 | ||
1408 | Second, the printer only handles one type, whereas a library typically has | |
1409 | several types. One could install a lookup function for each desired type | |
1410 | in the library, but one could also have a single lookup function recognize | |
1411 | several types. The latter is the conventional way this is handled. | |
1412 | If a pretty-printer can handle multiple data types, then its | |
1413 | @dfn{subprinters} are the printers for the individual data types. | |
1414 | ||
1415 | The @code{gdb.printing} module provides a formal way of solving these | |
1416 | problems (@pxref{gdb.printing}). | |
1417 | Here is another example that handles multiple types. | |
1418 | ||
1419 | These are the types we are going to pretty-print: | |
1420 | ||
1421 | @smallexample | |
1422 | struct foo @{ int a, b; @}; | |
1423 | struct bar @{ struct foo x, y; @}; | |
1424 | @end smallexample | |
1425 | ||
1426 | Here are the printers: | |
1427 | ||
1428 | @smallexample | |
1429 | class fooPrinter: | |
1430 | """Print a foo object.""" | |
1431 | ||
1432 | def __init__(self, val): | |
1433 | self.val = val | |
1434 | ||
1435 | def to_string(self): | |
1436 | return ("a=<" + str(self.val["a"]) + | |
1437 | "> b=<" + str(self.val["b"]) + ">") | |
1438 | ||
1439 | class barPrinter: | |
1440 | """Print a bar object.""" | |
1441 | ||
1442 | def __init__(self, val): | |
1443 | self.val = val | |
1444 | ||
1445 | def to_string(self): | |
1446 | return ("x=<" + str(self.val["x"]) + | |
1447 | "> y=<" + str(self.val["y"]) + ">") | |
1448 | @end smallexample | |
1449 | ||
1450 | This example doesn't need a lookup function, that is handled by the | |
1451 | @code{gdb.printing} module. Instead a function is provided to build up | |
1452 | the object that handles the lookup. | |
1453 | ||
1454 | @smallexample | |
1455 | import gdb.printing | |
1456 | ||
1457 | def build_pretty_printer(): | |
1458 | pp = gdb.printing.RegexpCollectionPrettyPrinter( | |
1459 | "my_library") | |
1460 | pp.add_printer('foo', '^foo$', fooPrinter) | |
1461 | pp.add_printer('bar', '^bar$', barPrinter) | |
1462 | return pp | |
1463 | @end smallexample | |
1464 | ||
1465 | And here is the autoload support: | |
1466 | ||
1467 | @smallexample | |
1468 | import gdb.printing | |
1469 | import my_library | |
1470 | gdb.printing.register_pretty_printer( | |
1471 | gdb.current_objfile(), | |
1472 | my_library.build_pretty_printer()) | |
1473 | @end smallexample | |
1474 | ||
1475 | Finally, when this printer is loaded into @value{GDBN}, here is the | |
1476 | corresponding output of @samp{info pretty-printer}: | |
1477 | ||
1478 | @smallexample | |
1479 | (gdb) info pretty-printer | |
1480 | my_library.so: | |
1481 | my_library | |
1482 | foo | |
1483 | bar | |
1484 | @end smallexample | |
1485 | ||
1486 | @node Type Printing API | |
1487 | @subsubsection Type Printing API | |
1488 | @cindex type printing API for Python | |
1489 | ||
1490 | @value{GDBN} provides a way for Python code to customize type display. | |
1491 | This is mainly useful for substituting canonical typedef names for | |
1492 | types. | |
1493 | ||
1494 | @cindex type printer | |
1495 | A @dfn{type printer} is just a Python object conforming to a certain | |
1496 | protocol. A simple base class implementing the protocol is provided; | |
1497 | see @ref{gdb.types}. A type printer must supply at least: | |
1498 | ||
1499 | @defivar type_printer enabled | |
1500 | A boolean which is True if the printer is enabled, and False | |
1501 | otherwise. This is manipulated by the @code{enable type-printer} | |
1502 | and @code{disable type-printer} commands. | |
1503 | @end defivar | |
1504 | ||
1505 | @defivar type_printer name | |
1506 | The name of the type printer. This must be a string. This is used by | |
1507 | the @code{enable type-printer} and @code{disable type-printer} | |
1508 | commands. | |
1509 | @end defivar | |
1510 | ||
1511 | @defmethod type_printer instantiate (self) | |
1512 | This is called by @value{GDBN} at the start of type-printing. It is | |
1513 | only called if the type printer is enabled. This method must return a | |
1514 | new object that supplies a @code{recognize} method, as described below. | |
1515 | @end defmethod | |
1516 | ||
1517 | ||
1518 | When displaying a type, say via the @code{ptype} command, @value{GDBN} | |
1519 | will compute a list of type recognizers. This is done by iterating | |
1520 | first over the per-objfile type printers (@pxref{Objfiles In Python}), | |
1521 | followed by the per-progspace type printers (@pxref{Progspaces In | |
1522 | Python}), and finally the global type printers. | |
1523 | ||
1524 | @value{GDBN} will call the @code{instantiate} method of each enabled | |
1525 | type printer. If this method returns @code{None}, then the result is | |
1526 | ignored; otherwise, it is appended to the list of recognizers. | |
1527 | ||
1528 | Then, when @value{GDBN} is going to display a type name, it iterates | |
1529 | over the list of recognizers. For each one, it calls the recognition | |
1530 | function, stopping if the function returns a non-@code{None} value. | |
1531 | The recognition function is defined as: | |
1532 | ||
1533 | @defmethod type_recognizer recognize (self, type) | |
1534 | If @var{type} is not recognized, return @code{None}. Otherwise, | |
1535 | return a string which is to be printed as the name of @var{type}. | |
1536 | @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In | |
1537 | Python}). | |
1538 | @end defmethod | |
1539 | ||
1540 | @value{GDBN} uses this two-pass approach so that type printers can | |
1541 | efficiently cache information without holding on to it too long. For | |
1542 | example, it can be convenient to look up type information in a type | |
1543 | printer and hold it for a recognizer's lifetime; if a single pass were | |
1544 | done then type printers would have to make use of the event system in | |
1545 | order to avoid holding information that could become stale as the | |
1546 | inferior changed. | |
1547 | ||
1548 | @node Frame Filter API | |
1549 | @subsubsection Filtering Frames. | |
1550 | @cindex frame filters api | |
1551 | ||
1552 | Frame filters are Python objects that manipulate the visibility of a | |
1553 | frame or frames when a backtrace (@pxref{Backtrace}) is printed by | |
1554 | @value{GDBN}. | |
1555 | ||
1556 | Only commands that print a backtrace, or, in the case of @sc{gdb/mi} | |
1557 | commands (@pxref{GDB/MI}), those that return a collection of frames | |
1558 | are affected. The commands that work with frame filters are: | |
1559 | ||
1560 | @code{backtrace} (@pxref{backtrace-command,, The backtrace command}), | |
1561 | @code{-stack-list-frames} | |
1562 | (@pxref{-stack-list-frames,, The -stack-list-frames command}), | |
1563 | @code{-stack-list-variables} (@pxref{-stack-list-variables,, The | |
1564 | -stack-list-variables command}), @code{-stack-list-arguments} | |
1565 | @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and | |
1566 | @code{-stack-list-locals} (@pxref{-stack-list-locals,, The | |
1567 | -stack-list-locals command}). | |
1568 | ||
1569 | A frame filter works by taking an iterator as an argument, applying | |
1570 | actions to the contents of that iterator, and returning another | |
1571 | iterator (or, possibly, the same iterator it was provided in the case | |
1572 | where the filter does not perform any operations). Typically, frame | |
1573 | filters utilize tools such as the Python's @code{itertools} module to | |
1574 | work with and create new iterators from the source iterator. | |
1575 | Regardless of how a filter chooses to apply actions, it must not alter | |
1576 | the underlying @value{GDBN} frame or frames, or attempt to alter the | |
1577 | call-stack within @value{GDBN}. This preserves data integrity within | |
1578 | @value{GDBN}. Frame filters are executed on a priority basis and care | |
1579 | should be taken that some frame filters may have been executed before, | |
1580 | and that some frame filters will be executed after. | |
1581 | ||
1582 | An important consideration when designing frame filters, and well | |
1583 | worth reflecting upon, is that frame filters should avoid unwinding | |
1584 | the call stack if possible. Some stacks can run very deep, into the | |
1585 | tens of thousands in some cases. To search every frame when a frame | |
1586 | filter executes may be too expensive at that step. The frame filter | |
1587 | cannot know how many frames it has to iterate over, and it may have to | |
1588 | iterate through them all. This ends up duplicating effort as | |
1589 | @value{GDBN} performs this iteration when it prints the frames. If | |
1590 | the filter can defer unwinding frames until frame decorators are | |
1591 | executed, after the last filter has executed, it should. @xref{Frame | |
1592 | Decorator API}, for more information on decorators. Also, there are | |
1593 | examples for both frame decorators and filters in later chapters. | |
1594 | @xref{Writing a Frame Filter}, for more information. | |
1595 | ||
1596 | The Python dictionary @code{gdb.frame_filters} contains key/object | |
1597 | pairings that comprise a frame filter. Frame filters in this | |
1598 | dictionary are called @code{global} frame filters, and they are | |
1599 | available when debugging all inferiors. These frame filters must | |
1600 | register with the dictionary directly. In addition to the | |
1601 | @code{global} dictionary, there are other dictionaries that are loaded | |
1602 | with different inferiors via auto-loading (@pxref{Python | |
1603 | Auto-loading}). The two other areas where frame filter dictionaries | |
1604 | can be found are: @code{gdb.Progspace} which contains a | |
1605 | @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile} | |
1606 | object which also contains a @code{frame_filters} dictionary | |
1607 | attribute. | |
1608 | ||
1609 | When a command is executed from @value{GDBN} that is compatible with | |
1610 | frame filters, @value{GDBN} combines the @code{global}, | |
1611 | @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently | |
1612 | loaded. All of the @code{gdb.Objfile} dictionaries are combined, as | |
1613 | several frames, and thus several object files, might be in use. | |
1614 | @value{GDBN} then prunes any frame filter whose @code{enabled} | |
1615 | attribute is @code{False}. This pruned list is then sorted according | |
1616 | to the @code{priority} attribute in each filter. | |
1617 | ||
1618 | Once the dictionaries are combined, pruned and sorted, @value{GDBN} | |
1619 | creates an iterator which wraps each frame in the call stack in a | |
1620 | @code{FrameDecorator} object, and calls each filter in order. The | |
1621 | output from the previous filter will always be the input to the next | |
1622 | filter, and so on. | |
1623 | ||
1624 | Frame filters have a mandatory interface which each frame filter must | |
1625 | implement, defined here: | |
1626 | ||
1627 | @defun FrameFilter.filter (iterator) | |
1628 | @value{GDBN} will call this method on a frame filter when it has | |
1629 | reached the order in the priority list for that filter. | |
1630 | ||
1631 | For example, if there are four frame filters: | |
1632 | ||
1633 | @smallexample | |
1634 | Name Priority | |
1635 | ||
1636 | Filter1 5 | |
1637 | Filter2 10 | |
1638 | Filter3 100 | |
1639 | Filter4 1 | |
1640 | @end smallexample | |
1641 | ||
1642 | The order that the frame filters will be called is: | |
1643 | ||
1644 | @smallexample | |
1645 | Filter3 -> Filter2 -> Filter1 -> Filter4 | |
1646 | @end smallexample | |
1647 | ||
1648 | Note that the output from @code{Filter3} is passed to the input of | |
1649 | @code{Filter2}, and so on. | |
1650 | ||
1651 | This @code{filter} method is passed a Python iterator. This iterator | |
1652 | contains a sequence of frame decorators that wrap each | |
1653 | @code{gdb.Frame}, or a frame decorator that wraps another frame | |
1654 | decorator. The first filter that is executed in the sequence of frame | |
1655 | filters will receive an iterator entirely comprised of default | |
1656 | @code{FrameDecorator} objects. However, after each frame filter is | |
1657 | executed, the previous frame filter may have wrapped some or all of | |
1658 | the frame decorators with their own frame decorator. As frame | |
1659 | decorators must also conform to a mandatory interface, these | |
1660 | decorators can be assumed to act in a uniform manner (@pxref{Frame | |
1661 | Decorator API}). | |
1662 | ||
1663 | This method must return an object conforming to the Python iterator | |
1664 | protocol. Each item in the iterator must be an object conforming to | |
1665 | the frame decorator interface. If a frame filter does not wish to | |
1666 | perform any operations on this iterator, it should return that | |
1667 | iterator untouched. | |
1668 | ||
1669 | This method is not optional. If it does not exist, @value{GDBN} will | |
1670 | raise and print an error. | |
1671 | @end defun | |
1672 | ||
1673 | @defvar FrameFilter.name | |
1674 | The @code{name} attribute must be Python string which contains the | |
1675 | name of the filter displayed by @value{GDBN} (@pxref{Frame Filter | |
1676 | Management}). This attribute may contain any combination of letters | |
1677 | or numbers. Care should be taken to ensure that it is unique. This | |
1678 | attribute is mandatory. | |
1679 | @end defvar | |
1680 | ||
1681 | @defvar FrameFilter.enabled | |
1682 | The @code{enabled} attribute must be Python boolean. This attribute | |
1683 | indicates to @value{GDBN} whether the frame filter is enabled, and | |
1684 | should be considered when frame filters are executed. If | |
1685 | @code{enabled} is @code{True}, then the frame filter will be executed | |
1686 | when any of the backtrace commands detailed earlier in this chapter | |
1687 | are executed. If @code{enabled} is @code{False}, then the frame | |
1688 | filter will not be executed. This attribute is mandatory. | |
1689 | @end defvar | |
1690 | ||
1691 | @defvar FrameFilter.priority | |
1692 | The @code{priority} attribute must be Python integer. This attribute | |
1693 | controls the order of execution in relation to other frame filters. | |
1694 | There are no imposed limits on the range of @code{priority} other than | |
1695 | it must be a valid integer. The higher the @code{priority} attribute, | |
1696 | the sooner the frame filter will be executed in relation to other | |
1697 | frame filters. Although @code{priority} can be negative, it is | |
1698 | recommended practice to assume zero is the lowest priority that a | |
1699 | frame filter can be assigned. Frame filters that have the same | |
1700 | priority are executed in unsorted order in that priority slot. This | |
1701 | attribute is mandatory. | |
1702 | @end defvar | |
1703 | ||
1704 | @node Frame Decorator API | |
1705 | @subsubsection Decorating Frames. | |
1706 | @cindex frame decorator api | |
1707 | ||
1708 | Frame decorators are sister objects to frame filters (@pxref{Frame | |
1709 | Filter API}). Frame decorators are applied by a frame filter and can | |
1710 | only be used in conjunction with frame filters. | |
1711 | ||
1712 | The purpose of a frame decorator is to customize the printed content | |
1713 | of each @code{gdb.Frame} in commands where frame filters are executed. | |
1714 | This concept is called decorating a frame. Frame decorators decorate | |
1715 | a @code{gdb.Frame} with Python code contained within each API call. | |
1716 | This separates the actual data contained in a @code{gdb.Frame} from | |
1717 | the decorated data produced by a frame decorator. This abstraction is | |
1718 | necessary to maintain integrity of the data contained in each | |
1719 | @code{gdb.Frame}. | |
1720 | ||
1721 | Frame decorators have a mandatory interface, defined below. | |
1722 | ||
1723 | @value{GDBN} already contains a frame decorator called | |
1724 | @code{FrameDecorator}. This contains substantial amounts of | |
1725 | boilerplate code to decorate the content of a @code{gdb.Frame}. It is | |
1726 | recommended that other frame decorators inherit and extend this | |
1727 | object, and only to override the methods needed. | |
1728 | ||
1729 | @defun FrameDecorator.elided (self) | |
1730 | ||
1731 | The @code{elided} method groups frames together in a hierarchical | |
1732 | system. An example would be an interpreter, where multiple low-level | |
1733 | frames make up a single call in the interpreted language. In this | |
1734 | example, the frame filter would elide the low-level frames and present | |
1735 | a single high-level frame, representing the call in the interpreted | |
1736 | language, to the user. | |
1737 | ||
1738 | The @code{elided} function must return an iterable and this iterable | |
1739 | must contain the frames that are being elided wrapped in a suitable | |
1740 | frame decorator. If no frames are being elided this function may | |
1741 | return an empty iterable, or @code{None}. Elided frames are indented | |
1742 | from normal frames in a @code{CLI} backtrace, or in the case of | |
1743 | @code{GDB/MI}, are placed in the @code{children} field of the eliding | |
1744 | frame. | |
1745 | ||
1746 | It is the frame filter's task to also filter out the elided frames from | |
1747 | the source iterator. This will avoid printing the frame twice. | |
1748 | @end defun | |
1749 | ||
1750 | @defun FrameDecorator.function (self) | |
1751 | ||
1752 | This method returns the name of the function in the frame that is to | |
1753 | be printed. | |
1754 | ||
1755 | This method must return a Python string describing the function, or | |
1756 | @code{None}. | |
1757 | ||
1758 | If this function returns @code{None}, @value{GDBN} will not print any | |
1759 | data for this field. | |
1760 | @end defun | |
1761 | ||
1762 | @defun FrameDecorator.address (self) | |
1763 | ||
1764 | This method returns the address of the frame that is to be printed. | |
1765 | ||
1766 | This method must return a Python numeric integer type of sufficient | |
1767 | size to describe the address of the frame, or @code{None}. | |
1768 | ||
1769 | If this function returns a @code{None}, @value{GDBN} will not print | |
1770 | any data for this field. | |
1771 | @end defun | |
1772 | ||
1773 | @defun FrameDecorator.filename (self) | |
1774 | ||
1775 | This method returns the filename and path associated with this frame. | |
1776 | ||
1777 | This method must return a Python string containing the filename and | |
1778 | the path to the object file backing the frame, or @code{None}. | |
1779 | ||
1780 | If this function returns a @code{None}, @value{GDBN} will not print | |
1781 | any data for this field. | |
1782 | @end defun | |
1783 | ||
1784 | @defun FrameDecorator.line (self): | |
1785 | ||
1786 | This method returns the line number associated with the current | |
1787 | position within the function addressed by this frame. | |
1788 | ||
1789 | This method must return a Python integer type, or @code{None}. | |
1790 | ||
1791 | If this function returns a @code{None}, @value{GDBN} will not print | |
1792 | any data for this field. | |
1793 | @end defun | |
1794 | ||
1795 | @defun FrameDecorator.frame_args (self) | |
1796 | @anchor{frame_args} | |
1797 | ||
1798 | This method must return an iterable, or @code{None}. Returning an | |
1799 | empty iterable, or @code{None} means frame arguments will not be | |
1800 | printed for this frame. This iterable must contain objects that | |
1801 | implement two methods, described here. | |
1802 | ||
1803 | This object must implement a @code{argument} method which takes a | |
1804 | single @code{self} parameter and must return a @code{gdb.Symbol} | |
1805 | (@pxref{Symbols In Python}), or a Python string. The object must also | |
1806 | implement a @code{value} method which takes a single @code{self} | |
1807 | parameter and must return a @code{gdb.Value} (@pxref{Values From | |
1808 | Inferior}), a Python value, or @code{None}. If the @code{value} | |
1809 | method returns @code{None}, and the @code{argument} method returns a | |
1810 | @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of | |
1811 | the @code{gdb.Symbol} automatically. | |
1812 | ||
1813 | A brief example: | |
1814 | ||
1815 | @smallexample | |
1816 | class SymValueWrapper(): | |
1817 | ||
1818 | def __init__(self, symbol, value): | |
1819 | self.sym = symbol | |
1820 | self.val = value | |
1821 | ||
1822 | def value(self): | |
1823 | return self.val | |
1824 | ||
1825 | def symbol(self): | |
1826 | return self.sym | |
1827 | ||
1828 | class SomeFrameDecorator() | |
1829 | ... | |
1830 | ... | |
1831 | def frame_args(self): | |
1832 | args = [] | |
1833 | try: | |
1834 | block = self.inferior_frame.block() | |
1835 | except: | |
1836 | return None | |
1837 | ||
1838 | # Iterate over all symbols in a block. Only add | |
1839 | # symbols that are arguments. | |
1840 | for sym in block: | |
1841 | if not sym.is_argument: | |
1842 | continue | |
1843 | args.append(SymValueWrapper(sym,None)) | |
1844 | ||
1845 | # Add example synthetic argument. | |
1846 | args.append(SymValueWrapper(``foo'', 42)) | |
1847 | ||
1848 | return args | |
1849 | @end smallexample | |
1850 | @end defun | |
1851 | ||
1852 | @defun FrameDecorator.frame_locals (self) | |
1853 | ||
1854 | This method must return an iterable or @code{None}. Returning an | |
1855 | empty iterable, or @code{None} means frame local arguments will not be | |
1856 | printed for this frame. | |
1857 | ||
1858 | The object interface, the description of the various strategies for | |
1859 | reading frame locals, and the example are largely similar to those | |
1860 | described in the @code{frame_args} function, (@pxref{frame_args,,The | |
1861 | frame filter frame_args function}). Below is a modified example: | |
1862 | ||
1863 | @smallexample | |
1864 | class SomeFrameDecorator() | |
1865 | ... | |
1866 | ... | |
1867 | def frame_locals(self): | |
1868 | vars = [] | |
1869 | try: | |
1870 | block = self.inferior_frame.block() | |
1871 | except: | |
1872 | return None | |
1873 | ||
1874 | # Iterate over all symbols in a block. Add all | |
1875 | # symbols, except arguments. | |
1876 | for sym in block: | |
1877 | if sym.is_argument: | |
1878 | continue | |
1879 | vars.append(SymValueWrapper(sym,None)) | |
1880 | ||
1881 | # Add an example of a synthetic local variable. | |
1882 | vars.append(SymValueWrapper(``bar'', 99)) | |
1883 | ||
1884 | return vars | |
1885 | @end smallexample | |
1886 | @end defun | |
1887 | ||
1888 | @defun FrameDecorator.inferior_frame (self): | |
1889 | ||
1890 | This method must return the underlying @code{gdb.Frame} that this | |
1891 | frame decorator is decorating. @value{GDBN} requires the underlying | |
1892 | frame for internal frame information to determine how to print certain | |
1893 | values when printing a frame. | |
1894 | @end defun | |
1895 | ||
1896 | @node Writing a Frame Filter | |
1897 | @subsubsection Writing a Frame Filter | |
1898 | @cindex writing a frame filter | |
1899 | ||
1900 | There are three basic elements that a frame filter must implement: it | |
1901 | must correctly implement the documented interface (@pxref{Frame Filter | |
1902 | API}), it must register itself with @value{GDBN}, and finally, it must | |
1903 | decide if it is to work on the data provided by @value{GDBN}. In all | |
1904 | cases, whether it works on the iterator or not, each frame filter must | |
1905 | return an iterator. A bare-bones frame filter follows the pattern in | |
1906 | the following example. | |
1907 | ||
1908 | @smallexample | |
1909 | import gdb | |
1910 | ||
1911 | class FrameFilter(): | |
1912 | ||
1913 | def __init__(self): | |
1914 | # Frame filter attribute creation. | |
1915 | # | |
1916 | # 'name' is the name of the filter that GDB will display. | |
1917 | # | |
1918 | # 'priority' is the priority of the filter relative to other | |
1919 | # filters. | |
1920 | # | |
1921 | # 'enabled' is a boolean that indicates whether this filter is | |
1922 | # enabled and should be executed. | |
1923 | ||
1924 | self.name = "Foo" | |
1925 | self.priority = 100 | |
1926 | self.enabled = True | |
1927 | ||
1928 | # Register this frame filter with the global frame_filters | |
1929 | # dictionary. | |
1930 | gdb.frame_filters[self.name] = self | |
1931 | ||
1932 | def filter(self, frame_iter): | |
1933 | # Just return the iterator. | |
1934 | return frame_iter | |
1935 | @end smallexample | |
1936 | ||
1937 | The frame filter in the example above implements the three | |
1938 | requirements for all frame filters. It implements the API, self | |
1939 | registers, and makes a decision on the iterator (in this case, it just | |
1940 | returns the iterator untouched). | |
1941 | ||
1942 | The first step is attribute creation and assignment, and as shown in | |
1943 | the comments the filter assigns the following attributes: @code{name}, | |
1944 | @code{priority} and whether the filter should be enabled with the | |
1945 | @code{enabled} attribute. | |
1946 | ||
1947 | The second step is registering the frame filter with the dictionary or | |
1948 | dictionaries that the frame filter has interest in. As shown in the | |
1949 | comments, this filter just registers itself with the global dictionary | |
1950 | @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters} | |
1951 | is a dictionary that is initialized in the @code{gdb} module when | |
1952 | @value{GDBN} starts. What dictionary a filter registers with is an | |
1953 | important consideration. Generally, if a filter is specific to a set | |
1954 | of code, it should be registered either in the @code{objfile} or | |
1955 | @code{progspace} dictionaries as they are specific to the program | |
1956 | currently loaded in @value{GDBN}. The global dictionary is always | |
1957 | present in @value{GDBN} and is never unloaded. Any filters registered | |
1958 | with the global dictionary will exist until @value{GDBN} exits. To | |
1959 | avoid filters that may conflict, it is generally better to register | |
1960 | frame filters against the dictionaries that more closely align with | |
1961 | the usage of the filter currently in question. @xref{Python | |
1962 | Auto-loading}, for further information on auto-loading Python scripts. | |
1963 | ||
1964 | @value{GDBN} takes a hands-off approach to frame filter registration, | |
1965 | therefore it is the frame filter's responsibility to ensure | |
1966 | registration has occurred, and that any exceptions are handled | |
1967 | appropriately. In particular, you may wish to handle exceptions | |
1968 | relating to Python dictionary key uniqueness. It is mandatory that | |
1969 | the dictionary key is the same as frame filter's @code{name} | |
1970 | attribute. When a user manages frame filters (@pxref{Frame Filter | |
1971 | Management}), the names @value{GDBN} will display are those contained | |
1972 | in the @code{name} attribute. | |
1973 | ||
1974 | The final step of this example is the implementation of the | |
1975 | @code{filter} method. As shown in the example comments, we define the | |
1976 | @code{filter} method and note that the method must take an iterator, | |
1977 | and also must return an iterator. In this bare-bones example, the | |
1978 | frame filter is not very useful as it just returns the iterator | |
1979 | untouched. However this is a valid operation for frame filters that | |
1980 | have the @code{enabled} attribute set, but decide not to operate on | |
1981 | any frames. | |
1982 | ||
1983 | In the next example, the frame filter operates on all frames and | |
1984 | utilizes a frame decorator to perform some work on the frames. | |
1985 | @xref{Frame Decorator API}, for further information on the frame | |
1986 | decorator interface. | |
1987 | ||
1988 | This example works on inlined frames. It highlights frames which are | |
1989 | inlined by tagging them with an ``[inlined]'' tag. By applying a | |
1990 | frame decorator to all frames with the Python @code{itertools imap} | |
1991 | method, the example defers actions to the frame decorator. Frame | |
1992 | decorators are only processed when @value{GDBN} prints the backtrace. | |
1993 | ||
1994 | This introduces a new decision making topic: whether to perform | |
1995 | decision making operations at the filtering step, or at the printing | |
1996 | step. In this example's approach, it does not perform any filtering | |
1997 | decisions at the filtering step beyond mapping a frame decorator to | |
1998 | each frame. This allows the actual decision making to be performed | |
1999 | when each frame is printed. This is an important consideration, and | |
2000 | well worth reflecting upon when designing a frame filter. An issue | |
2001 | that frame filters should avoid is unwinding the stack if possible. | |
2002 | Some stacks can run very deep, into the tens of thousands in some | |
2003 | cases. To search every frame to determine if it is inlined ahead of | |
2004 | time may be too expensive at the filtering step. The frame filter | |
2005 | cannot know how many frames it has to iterate over, and it would have | |
2006 | to iterate through them all. This ends up duplicating effort as | |
2007 | @value{GDBN} performs this iteration when it prints the frames. | |
2008 | ||
2009 | In this example decision making can be deferred to the printing step. | |
2010 | As each frame is printed, the frame decorator can examine each frame | |
2011 | in turn when @value{GDBN} iterates. From a performance viewpoint, | |
2012 | this is the most appropriate decision to make as it avoids duplicating | |
2013 | the effort that the printing step would undertake anyway. Also, if | |
2014 | there are many frame filters unwinding the stack during filtering, it | |
2015 | can substantially delay the printing of the backtrace which will | |
2016 | result in large memory usage, and a poor user experience. | |
2017 | ||
2018 | @smallexample | |
2019 | class InlineFilter(): | |
2020 | ||
2021 | def __init__(self): | |
2022 | self.name = "InlinedFrameFilter" | |
2023 | self.priority = 100 | |
2024 | self.enabled = True | |
2025 | gdb.frame_filters[self.name] = self | |
2026 | ||
2027 | def filter(self, frame_iter): | |
2028 | frame_iter = itertools.imap(InlinedFrameDecorator, | |
2029 | frame_iter) | |
2030 | return frame_iter | |
2031 | @end smallexample | |
2032 | ||
2033 | This frame filter is somewhat similar to the earlier example, except | |
2034 | that the @code{filter} method applies a frame decorator object called | |
2035 | @code{InlinedFrameDecorator} to each element in the iterator. The | |
2036 | @code{imap} Python method is light-weight. It does not proactively | |
2037 | iterate over the iterator, but rather creates a new iterator which | |
2038 | wraps the existing one. | |
2039 | ||
2040 | Below is the frame decorator for this example. | |
2041 | ||
2042 | @smallexample | |
2043 | class InlinedFrameDecorator(FrameDecorator): | |
2044 | ||
2045 | def __init__(self, fobj): | |
2046 | super(InlinedFrameDecorator, self).__init__(fobj) | |
2047 | ||
2048 | def function(self): | |
2049 | frame = fobj.inferior_frame() | |
2050 | name = str(frame.name()) | |
2051 | ||
2052 | if frame.type() == gdb.INLINE_FRAME: | |
2053 | name = name + " [inlined]" | |
2054 | ||
2055 | return name | |
2056 | @end smallexample | |
2057 | ||
2058 | This frame decorator only defines and overrides the @code{function} | |
2059 | method. It lets the supplied @code{FrameDecorator}, which is shipped | |
2060 | with @value{GDBN}, perform the other work associated with printing | |
2061 | this frame. | |
2062 | ||
2063 | The combination of these two objects create this output from a | |
2064 | backtrace: | |
2065 | ||
2066 | @smallexample | |
2067 | #0 0x004004e0 in bar () at inline.c:11 | |
2068 | #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21 | |
2069 | #2 0x00400566 in main () at inline.c:31 | |
2070 | @end smallexample | |
2071 | ||
2072 | So in the case of this example, a frame decorator is applied to all | |
2073 | frames, regardless of whether they may be inlined or not. As | |
2074 | @value{GDBN} iterates over the iterator produced by the frame filters, | |
2075 | @value{GDBN} executes each frame decorator which then makes a decision | |
2076 | on what to print in the @code{function} callback. Using a strategy | |
2077 | like this is a way to defer decisions on the frame content to printing | |
2078 | time. | |
2079 | ||
2080 | @subheading Eliding Frames | |
2081 | ||
2082 | It might be that the above example is not desirable for representing | |
2083 | inlined frames, and a hierarchical approach may be preferred. If we | |
2084 | want to hierarchically represent frames, the @code{elided} frame | |
2085 | decorator interface might be preferable. | |
2086 | ||
2087 | This example approaches the issue with the @code{elided} method. This | |
2088 | example is quite long, but very simplistic. It is out-of-scope for | |
2089 | this section to write a complete example that comprehensively covers | |
2090 | all approaches of finding and printing inlined frames. However, this | |
2091 | example illustrates the approach an author might use. | |
2092 | ||
2093 | This example comprises of three sections. | |
2094 | ||
2095 | @smallexample | |
2096 | class InlineFrameFilter(): | |
2097 | ||
2098 | def __init__(self): | |
2099 | self.name = "InlinedFrameFilter" | |
2100 | self.priority = 100 | |
2101 | self.enabled = True | |
2102 | gdb.frame_filters[self.name] = self | |
2103 | ||
2104 | def filter(self, frame_iter): | |
2105 | return ElidingInlineIterator(frame_iter) | |
2106 | @end smallexample | |
2107 | ||
2108 | This frame filter is very similar to the other examples. The only | |
2109 | difference is this frame filter is wrapping the iterator provided to | |
2110 | it (@code{frame_iter}) with a custom iterator called | |
2111 | @code{ElidingInlineIterator}. This again defers actions to when | |
2112 | @value{GDBN} prints the backtrace, as the iterator is not traversed | |
2113 | until printing. | |
2114 | ||
2115 | The iterator for this example is as follows. It is in this section of | |
2116 | the example where decisions are made on the content of the backtrace. | |
2117 | ||
2118 | @smallexample | |
2119 | class ElidingInlineIterator: | |
2120 | def __init__(self, ii): | |
2121 | self.input_iterator = ii | |
2122 | ||
2123 | def __iter__(self): | |
2124 | return self | |
2125 | ||
2126 | def next(self): | |
2127 | frame = next(self.input_iterator) | |
2128 | ||
2129 | if frame.inferior_frame().type() != gdb.INLINE_FRAME: | |
2130 | return frame | |
2131 | ||
2132 | try: | |
2133 | eliding_frame = next(self.input_iterator) | |
2134 | except StopIteration: | |
2135 | return frame | |
2136 | return ElidingFrameDecorator(eliding_frame, [frame]) | |
2137 | @end smallexample | |
2138 | ||
2139 | This iterator implements the Python iterator protocol. When the | |
2140 | @code{next} function is called (when @value{GDBN} prints each frame), | |
2141 | the iterator checks if this frame decorator, @code{frame}, is wrapping | |
2142 | an inlined frame. If it is not, it returns the existing frame decorator | |
2143 | untouched. If it is wrapping an inlined frame, it assumes that the | |
2144 | inlined frame was contained within the next oldest frame, | |
2145 | @code{eliding_frame}, which it fetches. It then creates and returns a | |
2146 | frame decorator, @code{ElidingFrameDecorator}, which contains both the | |
2147 | elided frame, and the eliding frame. | |
2148 | ||
2149 | @smallexample | |
2150 | class ElidingInlineDecorator(FrameDecorator): | |
2151 | ||
2152 | def __init__(self, frame, elided_frames): | |
2153 | super(ElidingInlineDecorator, self).__init__(frame) | |
2154 | self.frame = frame | |
2155 | self.elided_frames = elided_frames | |
2156 | ||
2157 | def elided(self): | |
2158 | return iter(self.elided_frames) | |
2159 | @end smallexample | |
2160 | ||
2161 | This frame decorator overrides one function and returns the inlined | |
2162 | frame in the @code{elided} method. As before it lets | |
2163 | @code{FrameDecorator} do the rest of the work involved in printing | |
2164 | this frame. This produces the following output. | |
2165 | ||
2166 | @smallexample | |
2167 | #0 0x004004e0 in bar () at inline.c:11 | |
2168 | #2 0x00400529 in main () at inline.c:25 | |
2169 | #1 0x00400529 in max (b=6, a=12) at inline.c:15 | |
2170 | @end smallexample | |
2171 | ||
2172 | In that output, @code{max} which has been inlined into @code{main} is | |
2173 | printed hierarchically. Another approach would be to combine the | |
2174 | @code{function} method, and the @code{elided} method to both print a | |
2175 | marker in the inlined frame, and also show the hierarchical | |
2176 | relationship. | |
2177 | ||
2178 | @node Inferiors In Python | |
2179 | @subsubsection Inferiors In Python | |
2180 | @cindex inferiors in Python | |
2181 | ||
2182 | @findex gdb.Inferior | |
2183 | Programs which are being run under @value{GDBN} are called inferiors | |
2184 | (@pxref{Inferiors and Programs}). Python scripts can access | |
2185 | information about and manipulate inferiors controlled by @value{GDBN} | |
2186 | via objects of the @code{gdb.Inferior} class. | |
2187 | ||
2188 | The following inferior-related functions are available in the @code{gdb} | |
2189 | module: | |
2190 | ||
2191 | @defun gdb.inferiors () | |
2192 | Return a tuple containing all inferior objects. | |
2193 | @end defun | |
2194 | ||
2195 | @defun gdb.selected_inferior () | |
2196 | Return an object representing the current inferior. | |
2197 | @end defun | |
2198 | ||
2199 | A @code{gdb.Inferior} object has the following attributes: | |
2200 | ||
2201 | @defvar Inferior.num | |
2202 | ID of inferior, as assigned by GDB. | |
2203 | @end defvar | |
2204 | ||
2205 | @defvar Inferior.pid | |
2206 | Process ID of the inferior, as assigned by the underlying operating | |
2207 | system. | |
2208 | @end defvar | |
2209 | ||
2210 | @defvar Inferior.was_attached | |
2211 | Boolean signaling whether the inferior was created using `attach', or | |
2212 | started by @value{GDBN} itself. | |
2213 | @end defvar | |
2214 | ||
2215 | A @code{gdb.Inferior} object has the following methods: | |
2216 | ||
2217 | @defun Inferior.is_valid () | |
2218 | Returns @code{True} if the @code{gdb.Inferior} object is valid, | |
2219 | @code{False} if not. A @code{gdb.Inferior} object will become invalid | |
2220 | if the inferior no longer exists within @value{GDBN}. All other | |
2221 | @code{gdb.Inferior} methods will throw an exception if it is invalid | |
2222 | at the time the method is called. | |
2223 | @end defun | |
2224 | ||
2225 | @defun Inferior.threads () | |
2226 | This method returns a tuple holding all the threads which are valid | |
2227 | when it is called. If there are no valid threads, the method will | |
2228 | return an empty tuple. | |
2229 | @end defun | |
2230 | ||
2231 | @findex Inferior.read_memory | |
2232 | @defun Inferior.read_memory (address, length) | |
2233 | Read @var{length} bytes of memory from the inferior, starting at | |
2234 | @var{address}. Returns a buffer object, which behaves much like an array | |
2235 | or a string. It can be modified and given to the | |
2236 | @code{Inferior.write_memory} function. In @code{Python} 3, the return | |
2237 | value is a @code{memoryview} object. | |
2238 | @end defun | |
2239 | ||
2240 | @findex Inferior.write_memory | |
2241 | @defun Inferior.write_memory (address, buffer @r{[}, length@r{]}) | |
2242 | Write the contents of @var{buffer} to the inferior, starting at | |
2243 | @var{address}. The @var{buffer} parameter must be a Python object | |
2244 | which supports the buffer protocol, i.e., a string, an array or the | |
2245 | object returned from @code{Inferior.read_memory}. If given, @var{length} | |
2246 | determines the number of bytes from @var{buffer} to be written. | |
2247 | @end defun | |
2248 | ||
2249 | @findex gdb.search_memory | |
2250 | @defun Inferior.search_memory (address, length, pattern) | |
2251 | Search a region of the inferior memory starting at @var{address} with | |
2252 | the given @var{length} using the search pattern supplied in | |
2253 | @var{pattern}. The @var{pattern} parameter must be a Python object | |
2254 | which supports the buffer protocol, i.e., a string, an array or the | |
2255 | object returned from @code{gdb.read_memory}. Returns a Python @code{Long} | |
2256 | containing the address where the pattern was found, or @code{None} if | |
2257 | the pattern could not be found. | |
2258 | @end defun | |
2259 | ||
2260 | @node Events In Python | |
2261 | @subsubsection Events In Python | |
2262 | @cindex inferior events in Python | |
2263 | ||
2264 | @value{GDBN} provides a general event facility so that Python code can be | |
2265 | notified of various state changes, particularly changes that occur in | |
2266 | the inferior. | |
2267 | ||
2268 | An @dfn{event} is just an object that describes some state change. The | |
2269 | type of the object and its attributes will vary depending on the details | |
2270 | of the change. All the existing events are described below. | |
2271 | ||
2272 | In order to be notified of an event, you must register an event handler | |
2273 | with an @dfn{event registry}. An event registry is an object in the | |
2274 | @code{gdb.events} module which dispatches particular events. A registry | |
2275 | provides methods to register and unregister event handlers: | |
2276 | ||
2277 | @defun EventRegistry.connect (object) | |
2278 | Add the given callable @var{object} to the registry. This object will be | |
2279 | called when an event corresponding to this registry occurs. | |
2280 | @end defun | |
2281 | ||
2282 | @defun EventRegistry.disconnect (object) | |
2283 | Remove the given @var{object} from the registry. Once removed, the object | |
2284 | will no longer receive notifications of events. | |
2285 | @end defun | |
2286 | ||
2287 | Here is an example: | |
2288 | ||
2289 | @smallexample | |
2290 | def exit_handler (event): | |
2291 | print "event type: exit" | |
2292 | print "exit code: %d" % (event.exit_code) | |
2293 | ||
2294 | gdb.events.exited.connect (exit_handler) | |
2295 | @end smallexample | |
2296 | ||
2297 | In the above example we connect our handler @code{exit_handler} to the | |
2298 | registry @code{events.exited}. Once connected, @code{exit_handler} gets | |
2299 | called when the inferior exits. The argument @dfn{event} in this example is | |
2300 | of type @code{gdb.ExitedEvent}. As you can see in the example the | |
2301 | @code{ExitedEvent} object has an attribute which indicates the exit code of | |
2302 | the inferior. | |
2303 | ||
2304 | The following is a listing of the event registries that are available and | |
2305 | details of the events they emit: | |
2306 | ||
2307 | @table @code | |
2308 | ||
2309 | @item events.cont | |
2310 | Emits @code{gdb.ThreadEvent}. | |
2311 | ||
2312 | Some events can be thread specific when @value{GDBN} is running in non-stop | |
2313 | mode. When represented in Python, these events all extend | |
2314 | @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead, | |
2315 | events which are emitted by this or other modules might extend this event. | |
2316 | Examples of these events are @code{gdb.BreakpointEvent} and | |
2317 | @code{gdb.ContinueEvent}. | |
2318 | ||
2319 | @defvar ThreadEvent.inferior_thread | |
2320 | In non-stop mode this attribute will be set to the specific thread which was | |
2321 | involved in the emitted event. Otherwise, it will be set to @code{None}. | |
2322 | @end defvar | |
2323 | ||
2324 | Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}. | |
2325 | ||
2326 | This event indicates that the inferior has been continued after a stop. For | |
2327 | inherited attribute refer to @code{gdb.ThreadEvent} above. | |
2328 | ||
2329 | @item events.exited | |
2330 | Emits @code{events.ExitedEvent} which indicates that the inferior has exited. | |
2331 | @code{events.ExitedEvent} has two attributes: | |
2332 | @defvar ExitedEvent.exit_code | |
2333 | An integer representing the exit code, if available, which the inferior | |
2334 | has returned. (The exit code could be unavailable if, for example, | |
2335 | @value{GDBN} detaches from the inferior.) If the exit code is unavailable, | |
2336 | the attribute does not exist. | |
2337 | @end defvar | |
2338 | @defvar ExitedEvent inferior | |
2339 | A reference to the inferior which triggered the @code{exited} event. | |
2340 | @end defvar | |
2341 | ||
2342 | @item events.stop | |
2343 | Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}. | |
2344 | ||
2345 | Indicates that the inferior has stopped. All events emitted by this registry | |
2346 | extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent} | |
2347 | will indicate the stopped thread when @value{GDBN} is running in non-stop | |
2348 | mode. Refer to @code{gdb.ThreadEvent} above for more details. | |
2349 | ||
2350 | Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}. | |
2351 | ||
2352 | This event indicates that the inferior or one of its threads has received as | |
2353 | signal. @code{gdb.SignalEvent} has the following attributes: | |
2354 | ||
2355 | @defvar SignalEvent.stop_signal | |
2356 | A string representing the signal received by the inferior. A list of possible | |
2357 | signal values can be obtained by running the command @code{info signals} in | |
2358 | the @value{GDBN} command prompt. | |
2359 | @end defvar | |
2360 | ||
2361 | Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}. | |
2362 | ||
2363 | @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have | |
2364 | been hit, and has the following attributes: | |
2365 | ||
2366 | @defvar BreakpointEvent.breakpoints | |
2367 | A sequence containing references to all the breakpoints (type | |
2368 | @code{gdb.Breakpoint}) that were hit. | |
2369 | @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object. | |
2370 | @end defvar | |
2371 | @defvar BreakpointEvent.breakpoint | |
2372 | A reference to the first breakpoint that was hit. | |
2373 | This function is maintained for backward compatibility and is now deprecated | |
2374 | in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute. | |
2375 | @end defvar | |
2376 | ||
2377 | @item events.new_objfile | |
2378 | Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has | |
2379 | been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute: | |
2380 | ||
2381 | @defvar NewObjFileEvent.new_objfile | |
2382 | A reference to the object file (@code{gdb.Objfile}) which has been loaded. | |
2383 | @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object. | |
2384 | @end defvar | |
2385 | ||
2386 | @end table | |
2387 | ||
2388 | @node Threads In Python | |
2389 | @subsubsection Threads In Python | |
2390 | @cindex threads in python | |
2391 | ||
2392 | @findex gdb.InferiorThread | |
2393 | Python scripts can access information about, and manipulate inferior threads | |
2394 | controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class. | |
2395 | ||
2396 | The following thread-related functions are available in the @code{gdb} | |
2397 | module: | |
2398 | ||
2399 | @findex gdb.selected_thread | |
2400 | @defun gdb.selected_thread () | |
2401 | This function returns the thread object for the selected thread. If there | |
2402 | is no selected thread, this will return @code{None}. | |
2403 | @end defun | |
2404 | ||
2405 | A @code{gdb.InferiorThread} object has the following attributes: | |
2406 | ||
2407 | @defvar InferiorThread.name | |
2408 | The name of the thread. If the user specified a name using | |
2409 | @code{thread name}, then this returns that name. Otherwise, if an | |
2410 | OS-supplied name is available, then it is returned. Otherwise, this | |
2411 | returns @code{None}. | |
2412 | ||
2413 | This attribute can be assigned to. The new value must be a string | |
2414 | object, which sets the new name, or @code{None}, which removes any | |
2415 | user-specified thread name. | |
2416 | @end defvar | |
2417 | ||
2418 | @defvar InferiorThread.num | |
2419 | ID of the thread, as assigned by GDB. | |
2420 | @end defvar | |
2421 | ||
2422 | @defvar InferiorThread.ptid | |
2423 | ID of the thread, as assigned by the operating system. This attribute is a | |
2424 | tuple containing three integers. The first is the Process ID (PID); the second | |
2425 | is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID). | |
2426 | Either the LWPID or TID may be 0, which indicates that the operating system | |
2427 | does not use that identifier. | |
2428 | @end defvar | |
2429 | ||
2430 | A @code{gdb.InferiorThread} object has the following methods: | |
2431 | ||
2432 | @defun InferiorThread.is_valid () | |
2433 | Returns @code{True} if the @code{gdb.InferiorThread} object is valid, | |
2434 | @code{False} if not. A @code{gdb.InferiorThread} object will become | |
2435 | invalid if the thread exits, or the inferior that the thread belongs | |
2436 | is deleted. All other @code{gdb.InferiorThread} methods will throw an | |
2437 | exception if it is invalid at the time the method is called. | |
2438 | @end defun | |
2439 | ||
2440 | @defun InferiorThread.switch () | |
2441 | This changes @value{GDBN}'s currently selected thread to the one represented | |
2442 | by this object. | |
2443 | @end defun | |
2444 | ||
2445 | @defun InferiorThread.is_stopped () | |
2446 | Return a Boolean indicating whether the thread is stopped. | |
2447 | @end defun | |
2448 | ||
2449 | @defun InferiorThread.is_running () | |
2450 | Return a Boolean indicating whether the thread is running. | |
2451 | @end defun | |
2452 | ||
2453 | @defun InferiorThread.is_exited () | |
2454 | Return a Boolean indicating whether the thread is exited. | |
2455 | @end defun | |
2456 | ||
2457 | @node Commands In Python | |
2458 | @subsubsection Commands In Python | |
2459 | ||
2460 | @cindex commands in python | |
2461 | @cindex python commands | |
2462 | You can implement new @value{GDBN} CLI commands in Python. A CLI | |
2463 | command is implemented using an instance of the @code{gdb.Command} | |
2464 | class, most commonly using a subclass. | |
2465 | ||
2466 | @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]}) | |
2467 | The object initializer for @code{Command} registers the new command | |
2468 | with @value{GDBN}. This initializer is normally invoked from the | |
2469 | subclass' own @code{__init__} method. | |
2470 | ||
2471 | @var{name} is the name of the command. If @var{name} consists of | |
2472 | multiple words, then the initial words are looked for as prefix | |
2473 | commands. In this case, if one of the prefix commands does not exist, | |
2474 | an exception is raised. | |
2475 | ||
2476 | There is no support for multi-line commands. | |
2477 | ||
2478 | @var{command_class} should be one of the @samp{COMMAND_} constants | |
2479 | defined below. This argument tells @value{GDBN} how to categorize the | |
2480 | new command in the help system. | |
2481 | ||
2482 | @var{completer_class} is an optional argument. If given, it should be | |
2483 | one of the @samp{COMPLETE_} constants defined below. This argument | |
2484 | tells @value{GDBN} how to perform completion for this command. If not | |
2485 | given, @value{GDBN} will attempt to complete using the object's | |
2486 | @code{complete} method (see below); if no such method is found, an | |
2487 | error will occur when completion is attempted. | |
2488 | ||
2489 | @var{prefix} is an optional argument. If @code{True}, then the new | |
2490 | command is a prefix command; sub-commands of this command may be | |
2491 | registered. | |
2492 | ||
2493 | The help text for the new command is taken from the Python | |
2494 | documentation string for the command's class, if there is one. If no | |
2495 | documentation string is provided, the default value ``This command is | |
2496 | not documented.'' is used. | |
2497 | @end defun | |
2498 | ||
2499 | @cindex don't repeat Python command | |
2500 | @defun Command.dont_repeat () | |
2501 | By default, a @value{GDBN} command is repeated when the user enters a | |
2502 | blank line at the command prompt. A command can suppress this | |
2503 | behavior by invoking the @code{dont_repeat} method. This is similar | |
2504 | to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}. | |
2505 | @end defun | |
2506 | ||
2507 | @defun Command.invoke (argument, from_tty) | |
2508 | This method is called by @value{GDBN} when this command is invoked. | |
2509 | ||
2510 | @var{argument} is a string. It is the argument to the command, after | |
2511 | leading and trailing whitespace has been stripped. | |
2512 | ||
2513 | @var{from_tty} is a boolean argument. When true, this means that the | |
2514 | command was entered by the user at the terminal; when false it means | |
2515 | that the command came from elsewhere. | |
2516 | ||
2517 | If this method throws an exception, it is turned into a @value{GDBN} | |
2518 | @code{error} call. Otherwise, the return value is ignored. | |
2519 | ||
2520 | @findex gdb.string_to_argv | |
2521 | To break @var{argument} up into an argv-like string use | |
2522 | @code{gdb.string_to_argv}. This function behaves identically to | |
2523 | @value{GDBN}'s internal argument lexer @code{buildargv}. | |
2524 | It is recommended to use this for consistency. | |
2525 | Arguments are separated by spaces and may be quoted. | |
2526 | Example: | |
2527 | ||
2528 | @smallexample | |
2529 | print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"") | |
2530 | ['1', '2 "3', '4 "5', "6 '7"] | |
2531 | @end smallexample | |
2532 | ||
2533 | @end defun | |
2534 | ||
2535 | @cindex completion of Python commands | |
2536 | @defun Command.complete (text, word) | |
2537 | This method is called by @value{GDBN} when the user attempts | |
2538 | completion on this command. All forms of completion are handled by | |
2539 | this method, that is, the @key{TAB} and @key{M-?} key bindings | |
2540 | (@pxref{Completion}), and the @code{complete} command (@pxref{Help, | |
2541 | complete}). | |
2542 | ||
2543 | The arguments @var{text} and @var{word} are both strings. @var{text} | |
2544 | holds the complete command line up to the cursor's location. | |
2545 | @var{word} holds the last word of the command line; this is computed | |
2546 | using a word-breaking heuristic. | |
2547 | ||
2548 | The @code{complete} method can return several values: | |
2549 | @itemize @bullet | |
2550 | @item | |
2551 | If the return value is a sequence, the contents of the sequence are | |
2552 | used as the completions. It is up to @code{complete} to ensure that the | |
2553 | contents actually do complete the word. A zero-length sequence is | |
2554 | allowed, it means that there were no completions available. Only | |
2555 | string elements of the sequence are used; other elements in the | |
2556 | sequence are ignored. | |
2557 | ||
2558 | @item | |
2559 | If the return value is one of the @samp{COMPLETE_} constants defined | |
2560 | below, then the corresponding @value{GDBN}-internal completion | |
2561 | function is invoked, and its result is used. | |
2562 | ||
2563 | @item | |
2564 | All other results are treated as though there were no available | |
2565 | completions. | |
2566 | @end itemize | |
2567 | @end defun | |
2568 | ||
2569 | When a new command is registered, it must be declared as a member of | |
2570 | some general class of commands. This is used to classify top-level | |
2571 | commands in the on-line help system; note that prefix commands are not | |
2572 | listed under their own category but rather that of their top-level | |
2573 | command. The available classifications are represented by constants | |
2574 | defined in the @code{gdb} module: | |
2575 | ||
2576 | @table @code | |
2577 | @findex COMMAND_NONE | |
2578 | @findex gdb.COMMAND_NONE | |
2579 | @item gdb.COMMAND_NONE | |
2580 | The command does not belong to any particular class. A command in | |
2581 | this category will not be displayed in any of the help categories. | |
2582 | ||
2583 | @findex COMMAND_RUNNING | |
2584 | @findex gdb.COMMAND_RUNNING | |
2585 | @item gdb.COMMAND_RUNNING | |
2586 | The command is related to running the inferior. For example, | |
2587 | @code{start}, @code{step}, and @code{continue} are in this category. | |
2588 | Type @kbd{help running} at the @value{GDBN} prompt to see a list of | |
2589 | commands in this category. | |
2590 | ||
2591 | @findex COMMAND_DATA | |
2592 | @findex gdb.COMMAND_DATA | |
2593 | @item gdb.COMMAND_DATA | |
2594 | The command is related to data or variables. For example, | |
2595 | @code{call}, @code{find}, and @code{print} are in this category. Type | |
2596 | @kbd{help data} at the @value{GDBN} prompt to see a list of commands | |
2597 | in this category. | |
2598 | ||
2599 | @findex COMMAND_STACK | |
2600 | @findex gdb.COMMAND_STACK | |
2601 | @item gdb.COMMAND_STACK | |
2602 | The command has to do with manipulation of the stack. For example, | |
2603 | @code{backtrace}, @code{frame}, and @code{return} are in this | |
2604 | category. Type @kbd{help stack} at the @value{GDBN} prompt to see a | |
2605 | list of commands in this category. | |
2606 | ||
2607 | @findex COMMAND_FILES | |
2608 | @findex gdb.COMMAND_FILES | |
2609 | @item gdb.COMMAND_FILES | |
2610 | This class is used for file-related commands. For example, | |
2611 | @code{file}, @code{list} and @code{section} are in this category. | |
2612 | Type @kbd{help files} at the @value{GDBN} prompt to see a list of | |
2613 | commands in this category. | |
2614 | ||
2615 | @findex COMMAND_SUPPORT | |
2616 | @findex gdb.COMMAND_SUPPORT | |
2617 | @item gdb.COMMAND_SUPPORT | |
2618 | This should be used for ``support facilities'', generally meaning | |
2619 | things that are useful to the user when interacting with @value{GDBN}, | |
2620 | but not related to the state of the inferior. For example, | |
2621 | @code{help}, @code{make}, and @code{shell} are in this category. Type | |
2622 | @kbd{help support} at the @value{GDBN} prompt to see a list of | |
2623 | commands in this category. | |
2624 | ||
2625 | @findex COMMAND_STATUS | |
2626 | @findex gdb.COMMAND_STATUS | |
2627 | @item gdb.COMMAND_STATUS | |
2628 | The command is an @samp{info}-related command, that is, related to the | |
2629 | state of @value{GDBN} itself. For example, @code{info}, @code{macro}, | |
2630 | and @code{show} are in this category. Type @kbd{help status} at the | |
2631 | @value{GDBN} prompt to see a list of commands in this category. | |
2632 | ||
2633 | @findex COMMAND_BREAKPOINTS | |
2634 | @findex gdb.COMMAND_BREAKPOINTS | |
2635 | @item gdb.COMMAND_BREAKPOINTS | |
2636 | The command has to do with breakpoints. For example, @code{break}, | |
2637 | @code{clear}, and @code{delete} are in this category. Type @kbd{help | |
2638 | breakpoints} at the @value{GDBN} prompt to see a list of commands in | |
2639 | this category. | |
2640 | ||
2641 | @findex COMMAND_TRACEPOINTS | |
2642 | @findex gdb.COMMAND_TRACEPOINTS | |
2643 | @item gdb.COMMAND_TRACEPOINTS | |
2644 | The command has to do with tracepoints. For example, @code{trace}, | |
2645 | @code{actions}, and @code{tfind} are in this category. Type | |
2646 | @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of | |
2647 | commands in this category. | |
2648 | ||
2649 | @findex COMMAND_USER | |
2650 | @findex gdb.COMMAND_USER | |
2651 | @item gdb.COMMAND_USER | |
2652 | The command is a general purpose command for the user, and typically | |
2653 | does not fit in one of the other categories. | |
2654 | Type @kbd{help user-defined} at the @value{GDBN} prompt to see | |
2655 | a list of commands in this category, as well as the list of gdb macros | |
2656 | (@pxref{Sequences}). | |
2657 | ||
2658 | @findex COMMAND_OBSCURE | |
2659 | @findex gdb.COMMAND_OBSCURE | |
2660 | @item gdb.COMMAND_OBSCURE | |
2661 | The command is only used in unusual circumstances, or is not of | |
2662 | general interest to users. For example, @code{checkpoint}, | |
2663 | @code{fork}, and @code{stop} are in this category. Type @kbd{help | |
2664 | obscure} at the @value{GDBN} prompt to see a list of commands in this | |
2665 | category. | |
2666 | ||
2667 | @findex COMMAND_MAINTENANCE | |
2668 | @findex gdb.COMMAND_MAINTENANCE | |
2669 | @item gdb.COMMAND_MAINTENANCE | |
2670 | The command is only useful to @value{GDBN} maintainers. The | |
2671 | @code{maintenance} and @code{flushregs} commands are in this category. | |
2672 | Type @kbd{help internals} at the @value{GDBN} prompt to see a list of | |
2673 | commands in this category. | |
2674 | @end table | |
2675 | ||
2676 | A new command can use a predefined completion function, either by | |
2677 | specifying it via an argument at initialization, or by returning it | |
2678 | from the @code{complete} method. These predefined completion | |
2679 | constants are all defined in the @code{gdb} module: | |
2680 | ||
b3ce5e5f DE |
2681 | @vtable @code |
2682 | @vindex COMPLETE_NONE | |
329baa95 DE |
2683 | @item gdb.COMPLETE_NONE |
2684 | This constant means that no completion should be done. | |
2685 | ||
b3ce5e5f | 2686 | @vindex COMPLETE_FILENAME |
329baa95 DE |
2687 | @item gdb.COMPLETE_FILENAME |
2688 | This constant means that filename completion should be performed. | |
2689 | ||
b3ce5e5f | 2690 | @vindex COMPLETE_LOCATION |
329baa95 DE |
2691 | @item gdb.COMPLETE_LOCATION |
2692 | This constant means that location completion should be done. | |
2693 | @xref{Specify Location}. | |
2694 | ||
b3ce5e5f | 2695 | @vindex COMPLETE_COMMAND |
329baa95 DE |
2696 | @item gdb.COMPLETE_COMMAND |
2697 | This constant means that completion should examine @value{GDBN} | |
2698 | command names. | |
2699 | ||
b3ce5e5f | 2700 | @vindex COMPLETE_SYMBOL |
329baa95 DE |
2701 | @item gdb.COMPLETE_SYMBOL |
2702 | This constant means that completion should be done using symbol names | |
2703 | as the source. | |
2704 | ||
b3ce5e5f | 2705 | @vindex COMPLETE_EXPRESSION |
329baa95 DE |
2706 | @item gdb.COMPLETE_EXPRESSION |
2707 | This constant means that completion should be done on expressions. | |
2708 | Often this means completing on symbol names, but some language | |
2709 | parsers also have support for completing on field names. | |
b3ce5e5f | 2710 | @end vtable |
329baa95 DE |
2711 | |
2712 | The following code snippet shows how a trivial CLI command can be | |
2713 | implemented in Python: | |
2714 | ||
2715 | @smallexample | |
2716 | class HelloWorld (gdb.Command): | |
2717 | """Greet the whole world.""" | |
2718 | ||
2719 | def __init__ (self): | |
2720 | super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER) | |
2721 | ||
2722 | def invoke (self, arg, from_tty): | |
2723 | print "Hello, World!" | |
2724 | ||
2725 | HelloWorld () | |
2726 | @end smallexample | |
2727 | ||
2728 | The last line instantiates the class, and is necessary to trigger the | |
2729 | registration of the command with @value{GDBN}. Depending on how the | |
2730 | Python code is read into @value{GDBN}, you may need to import the | |
2731 | @code{gdb} module explicitly. | |
2732 | ||
2733 | @node Parameters In Python | |
2734 | @subsubsection Parameters In Python | |
2735 | ||
2736 | @cindex parameters in python | |
2737 | @cindex python parameters | |
2738 | @tindex gdb.Parameter | |
2739 | @tindex Parameter | |
2740 | You can implement new @value{GDBN} parameters using Python. A new | |
2741 | parameter is implemented as an instance of the @code{gdb.Parameter} | |
2742 | class. | |
2743 | ||
2744 | Parameters are exposed to the user via the @code{set} and | |
2745 | @code{show} commands. @xref{Help}. | |
2746 | ||
2747 | There are many parameters that already exist and can be set in | |
2748 | @value{GDBN}. Two examples are: @code{set follow fork} and | |
2749 | @code{set charset}. Setting these parameters influences certain | |
2750 | behavior in @value{GDBN}. Similarly, you can define parameters that | |
2751 | can be used to influence behavior in custom Python scripts and commands. | |
2752 | ||
2753 | @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]}) | |
2754 | The object initializer for @code{Parameter} registers the new | |
2755 | parameter with @value{GDBN}. This initializer is normally invoked | |
2756 | from the subclass' own @code{__init__} method. | |
2757 | ||
2758 | @var{name} is the name of the new parameter. If @var{name} consists | |
2759 | of multiple words, then the initial words are looked for as prefix | |
2760 | parameters. An example of this can be illustrated with the | |
2761 | @code{set print} set of parameters. If @var{name} is | |
2762 | @code{print foo}, then @code{print} will be searched as the prefix | |
2763 | parameter. In this case the parameter can subsequently be accessed in | |
2764 | @value{GDBN} as @code{set print foo}. | |
2765 | ||
2766 | If @var{name} consists of multiple words, and no prefix parameter group | |
2767 | can be found, an exception is raised. | |
2768 | ||
2769 | @var{command-class} should be one of the @samp{COMMAND_} constants | |
2770 | (@pxref{Commands In Python}). This argument tells @value{GDBN} how to | |
2771 | categorize the new parameter in the help system. | |
2772 | ||
2773 | @var{parameter-class} should be one of the @samp{PARAM_} constants | |
2774 | defined below. This argument tells @value{GDBN} the type of the new | |
2775 | parameter; this information is used for input validation and | |
2776 | completion. | |
2777 | ||
2778 | If @var{parameter-class} is @code{PARAM_ENUM}, then | |
2779 | @var{enum-sequence} must be a sequence of strings. These strings | |
2780 | represent the possible values for the parameter. | |
2781 | ||
2782 | If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence | |
2783 | of a fourth argument will cause an exception to be thrown. | |
2784 | ||
2785 | The help text for the new parameter is taken from the Python | |
2786 | documentation string for the parameter's class, if there is one. If | |
2787 | there is no documentation string, a default value is used. | |
2788 | @end defun | |
2789 | ||
2790 | @defvar Parameter.set_doc | |
2791 | If this attribute exists, and is a string, then its value is used as | |
2792 | the help text for this parameter's @code{set} command. The value is | |
2793 | examined when @code{Parameter.__init__} is invoked; subsequent changes | |
2794 | have no effect. | |
2795 | @end defvar | |
2796 | ||
2797 | @defvar Parameter.show_doc | |
2798 | If this attribute exists, and is a string, then its value is used as | |
2799 | the help text for this parameter's @code{show} command. The value is | |
2800 | examined when @code{Parameter.__init__} is invoked; subsequent changes | |
2801 | have no effect. | |
2802 | @end defvar | |
2803 | ||
2804 | @defvar Parameter.value | |
2805 | The @code{value} attribute holds the underlying value of the | |
2806 | parameter. It can be read and assigned to just as any other | |
2807 | attribute. @value{GDBN} does validation when assignments are made. | |
2808 | @end defvar | |
2809 | ||
2810 | There are two methods that should be implemented in any | |
2811 | @code{Parameter} class. These are: | |
2812 | ||
2813 | @defun Parameter.get_set_string (self) | |
2814 | @value{GDBN} will call this method when a @var{parameter}'s value has | |
2815 | been changed via the @code{set} API (for example, @kbd{set foo off}). | |
2816 | The @code{value} attribute has already been populated with the new | |
2817 | value and may be used in output. This method must return a string. | |
2818 | @end defun | |
2819 | ||
2820 | @defun Parameter.get_show_string (self, svalue) | |
2821 | @value{GDBN} will call this method when a @var{parameter}'s | |
2822 | @code{show} API has been invoked (for example, @kbd{show foo}). The | |
2823 | argument @code{svalue} receives the string representation of the | |
2824 | current value. This method must return a string. | |
2825 | @end defun | |
2826 | ||
2827 | When a new parameter is defined, its type must be specified. The | |
2828 | available types are represented by constants defined in the @code{gdb} | |
2829 | module: | |
2830 | ||
2831 | @table @code | |
2832 | @findex PARAM_BOOLEAN | |
2833 | @findex gdb.PARAM_BOOLEAN | |
2834 | @item gdb.PARAM_BOOLEAN | |
2835 | The value is a plain boolean. The Python boolean values, @code{True} | |
2836 | and @code{False} are the only valid values. | |
2837 | ||
2838 | @findex PARAM_AUTO_BOOLEAN | |
2839 | @findex gdb.PARAM_AUTO_BOOLEAN | |
2840 | @item gdb.PARAM_AUTO_BOOLEAN | |
2841 | The value has three possible states: true, false, and @samp{auto}. In | |
2842 | Python, true and false are represented using boolean constants, and | |
2843 | @samp{auto} is represented using @code{None}. | |
2844 | ||
2845 | @findex PARAM_UINTEGER | |
2846 | @findex gdb.PARAM_UINTEGER | |
2847 | @item gdb.PARAM_UINTEGER | |
2848 | The value is an unsigned integer. The value of 0 should be | |
2849 | interpreted to mean ``unlimited''. | |
2850 | ||
2851 | @findex PARAM_INTEGER | |
2852 | @findex gdb.PARAM_INTEGER | |
2853 | @item gdb.PARAM_INTEGER | |
2854 | The value is a signed integer. The value of 0 should be interpreted | |
2855 | to mean ``unlimited''. | |
2856 | ||
2857 | @findex PARAM_STRING | |
2858 | @findex gdb.PARAM_STRING | |
2859 | @item gdb.PARAM_STRING | |
2860 | The value is a string. When the user modifies the string, any escape | |
2861 | sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are | |
2862 | translated into corresponding characters and encoded into the current | |
2863 | host charset. | |
2864 | ||
2865 | @findex PARAM_STRING_NOESCAPE | |
2866 | @findex gdb.PARAM_STRING_NOESCAPE | |
2867 | @item gdb.PARAM_STRING_NOESCAPE | |
2868 | The value is a string. When the user modifies the string, escapes are | |
2869 | passed through untranslated. | |
2870 | ||
2871 | @findex PARAM_OPTIONAL_FILENAME | |
2872 | @findex gdb.PARAM_OPTIONAL_FILENAME | |
2873 | @item gdb.PARAM_OPTIONAL_FILENAME | |
2874 | The value is a either a filename (a string), or @code{None}. | |
2875 | ||
2876 | @findex PARAM_FILENAME | |
2877 | @findex gdb.PARAM_FILENAME | |
2878 | @item gdb.PARAM_FILENAME | |
2879 | The value is a filename. This is just like | |
2880 | @code{PARAM_STRING_NOESCAPE}, but uses file names for completion. | |
2881 | ||
2882 | @findex PARAM_ZINTEGER | |
2883 | @findex gdb.PARAM_ZINTEGER | |
2884 | @item gdb.PARAM_ZINTEGER | |
2885 | The value is an integer. This is like @code{PARAM_INTEGER}, except 0 | |
2886 | is interpreted as itself. | |
2887 | ||
2888 | @findex PARAM_ENUM | |
2889 | @findex gdb.PARAM_ENUM | |
2890 | @item gdb.PARAM_ENUM | |
2891 | The value is a string, which must be one of a collection string | |
2892 | constants provided when the parameter is created. | |
2893 | @end table | |
2894 | ||
2895 | @node Functions In Python | |
2896 | @subsubsection Writing new convenience functions | |
2897 | ||
2898 | @cindex writing convenience functions | |
2899 | @cindex convenience functions in python | |
2900 | @cindex python convenience functions | |
2901 | @tindex gdb.Function | |
2902 | @tindex Function | |
2903 | You can implement new convenience functions (@pxref{Convenience Vars}) | |
2904 | in Python. A convenience function is an instance of a subclass of the | |
2905 | class @code{gdb.Function}. | |
2906 | ||
2907 | @defun Function.__init__ (name) | |
2908 | The initializer for @code{Function} registers the new function with | |
2909 | @value{GDBN}. The argument @var{name} is the name of the function, | |
2910 | a string. The function will be visible to the user as a convenience | |
2911 | variable of type @code{internal function}, whose name is the same as | |
2912 | the given @var{name}. | |
2913 | ||
2914 | The documentation for the new function is taken from the documentation | |
2915 | string for the new class. | |
2916 | @end defun | |
2917 | ||
2918 | @defun Function.invoke (@var{*args}) | |
2919 | When a convenience function is evaluated, its arguments are converted | |
2920 | to instances of @code{gdb.Value}, and then the function's | |
2921 | @code{invoke} method is called. Note that @value{GDBN} does not | |
2922 | predetermine the arity of convenience functions. Instead, all | |
2923 | available arguments are passed to @code{invoke}, following the | |
2924 | standard Python calling convention. In particular, a convenience | |
2925 | function can have default values for parameters without ill effect. | |
2926 | ||
2927 | The return value of this method is used as its value in the enclosing | |
2928 | expression. If an ordinary Python value is returned, it is converted | |
2929 | to a @code{gdb.Value} following the usual rules. | |
2930 | @end defun | |
2931 | ||
2932 | The following code snippet shows how a trivial convenience function can | |
2933 | be implemented in Python: | |
2934 | ||
2935 | @smallexample | |
2936 | class Greet (gdb.Function): | |
2937 | """Return string to greet someone. | |
2938 | Takes a name as argument.""" | |
2939 | ||
2940 | def __init__ (self): | |
2941 | super (Greet, self).__init__ ("greet") | |
2942 | ||
2943 | def invoke (self, name): | |
2944 | return "Hello, %s!" % name.string () | |
2945 | ||
2946 | Greet () | |
2947 | @end smallexample | |
2948 | ||
2949 | The last line instantiates the class, and is necessary to trigger the | |
2950 | registration of the function with @value{GDBN}. Depending on how the | |
2951 | Python code is read into @value{GDBN}, you may need to import the | |
2952 | @code{gdb} module explicitly. | |
2953 | ||
2954 | Now you can use the function in an expression: | |
2955 | ||
2956 | @smallexample | |
2957 | (gdb) print $greet("Bob") | |
2958 | $1 = "Hello, Bob!" | |
2959 | @end smallexample | |
2960 | ||
2961 | @node Progspaces In Python | |
2962 | @subsubsection Program Spaces In Python | |
2963 | ||
2964 | @cindex progspaces in python | |
2965 | @tindex gdb.Progspace | |
2966 | @tindex Progspace | |
2967 | A program space, or @dfn{progspace}, represents a symbolic view | |
2968 | of an address space. | |
2969 | It consists of all of the objfiles of the program. | |
2970 | @xref{Objfiles In Python}. | |
2971 | @xref{Inferiors and Programs, program spaces}, for more details | |
2972 | about program spaces. | |
2973 | ||
2974 | The following progspace-related functions are available in the | |
2975 | @code{gdb} module: | |
2976 | ||
2977 | @findex gdb.current_progspace | |
2978 | @defun gdb.current_progspace () | |
2979 | This function returns the program space of the currently selected inferior. | |
2980 | @xref{Inferiors and Programs}. | |
2981 | @end defun | |
2982 | ||
2983 | @findex gdb.progspaces | |
2984 | @defun gdb.progspaces () | |
2985 | Return a sequence of all the progspaces currently known to @value{GDBN}. | |
2986 | @end defun | |
2987 | ||
2988 | Each progspace is represented by an instance of the @code{gdb.Progspace} | |
2989 | class. | |
2990 | ||
2991 | @defvar Progspace.filename | |
2992 | The file name of the progspace as a string. | |
2993 | @end defvar | |
2994 | ||
2995 | @defvar Progspace.pretty_printers | |
2996 | The @code{pretty_printers} attribute is a list of functions. It is | |
2997 | used to look up pretty-printers. A @code{Value} is passed to each | |
2998 | function in order; if the function returns @code{None}, then the | |
2999 | search continues. Otherwise, the return value should be an object | |
3000 | which is used to format the value. @xref{Pretty Printing API}, for more | |
3001 | information. | |
3002 | @end defvar | |
3003 | ||
3004 | @defvar Progspace.type_printers | |
3005 | The @code{type_printers} attribute is a list of type printer objects. | |
3006 | @xref{Type Printing API}, for more information. | |
3007 | @end defvar | |
3008 | ||
3009 | @defvar Progspace.frame_filters | |
3010 | The @code{frame_filters} attribute is a dictionary of frame filter | |
3011 | objects. @xref{Frame Filter API}, for more information. | |
3012 | @end defvar | |
3013 | ||
3014 | @node Objfiles In Python | |
3015 | @subsubsection Objfiles In Python | |
3016 | ||
3017 | @cindex objfiles in python | |
3018 | @tindex gdb.Objfile | |
3019 | @tindex Objfile | |
3020 | @value{GDBN} loads symbols for an inferior from various | |
3021 | symbol-containing files (@pxref{Files}). These include the primary | |
3022 | executable file, any shared libraries used by the inferior, and any | |
3023 | separate debug info files (@pxref{Separate Debug Files}). | |
3024 | @value{GDBN} calls these symbol-containing files @dfn{objfiles}. | |
3025 | ||
3026 | The following objfile-related functions are available in the | |
3027 | @code{gdb} module: | |
3028 | ||
3029 | @findex gdb.current_objfile | |
3030 | @defun gdb.current_objfile () | |
3031 | When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN} | |
3032 | sets the ``current objfile'' to the corresponding objfile. This | |
3033 | function returns the current objfile. If there is no current objfile, | |
3034 | this function returns @code{None}. | |
3035 | @end defun | |
3036 | ||
3037 | @findex gdb.objfiles | |
3038 | @defun gdb.objfiles () | |
3039 | Return a sequence of all the objfiles current known to @value{GDBN}. | |
3040 | @xref{Objfiles In Python}. | |
3041 | @end defun | |
3042 | ||
3043 | Each objfile is represented by an instance of the @code{gdb.Objfile} | |
3044 | class. | |
3045 | ||
3046 | @defvar Objfile.filename | |
3047 | The file name of the objfile as a string. | |
3048 | @end defvar | |
3049 | ||
3050 | @defvar Objfile.pretty_printers | |
3051 | The @code{pretty_printers} attribute is a list of functions. It is | |
3052 | used to look up pretty-printers. A @code{Value} is passed to each | |
3053 | function in order; if the function returns @code{None}, then the | |
3054 | search continues. Otherwise, the return value should be an object | |
3055 | which is used to format the value. @xref{Pretty Printing API}, for more | |
3056 | information. | |
3057 | @end defvar | |
3058 | ||
3059 | @defvar Objfile.type_printers | |
3060 | The @code{type_printers} attribute is a list of type printer objects. | |
3061 | @xref{Type Printing API}, for more information. | |
3062 | @end defvar | |
3063 | ||
3064 | @defvar Objfile.frame_filters | |
3065 | The @code{frame_filters} attribute is a dictionary of frame filter | |
3066 | objects. @xref{Frame Filter API}, for more information. | |
3067 | @end defvar | |
3068 | ||
3069 | A @code{gdb.Objfile} object has the following methods: | |
3070 | ||
3071 | @defun Objfile.is_valid () | |
3072 | Returns @code{True} if the @code{gdb.Objfile} object is valid, | |
3073 | @code{False} if not. A @code{gdb.Objfile} object can become invalid | |
3074 | if the object file it refers to is not loaded in @value{GDBN} any | |
3075 | longer. All other @code{gdb.Objfile} methods will throw an exception | |
3076 | if it is invalid at the time the method is called. | |
3077 | @end defun | |
3078 | ||
3079 | @node Frames In Python | |
3080 | @subsubsection Accessing inferior stack frames from Python. | |
3081 | ||
3082 | @cindex frames in python | |
3083 | When the debugged program stops, @value{GDBN} is able to analyze its call | |
3084 | stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class | |
3085 | represents a frame in the stack. A @code{gdb.Frame} object is only valid | |
3086 | while its corresponding frame exists in the inferior's stack. If you try | |
3087 | to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error} | |
3088 | exception (@pxref{Exception Handling}). | |
3089 | ||
3090 | Two @code{gdb.Frame} objects can be compared for equality with the @code{==} | |
3091 | operator, like: | |
3092 | ||
3093 | @smallexample | |
3094 | (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame () | |
3095 | True | |
3096 | @end smallexample | |
3097 | ||
3098 | The following frame-related functions are available in the @code{gdb} module: | |
3099 | ||
3100 | @findex gdb.selected_frame | |
3101 | @defun gdb.selected_frame () | |
3102 | Return the selected frame object. (@pxref{Selection,,Selecting a Frame}). | |
3103 | @end defun | |
3104 | ||
3105 | @findex gdb.newest_frame | |
3106 | @defun gdb.newest_frame () | |
3107 | Return the newest frame object for the selected thread. | |
3108 | @end defun | |
3109 | ||
3110 | @defun gdb.frame_stop_reason_string (reason) | |
3111 | Return a string explaining the reason why @value{GDBN} stopped unwinding | |
3112 | frames, as expressed by the given @var{reason} code (an integer, see the | |
3113 | @code{unwind_stop_reason} method further down in this section). | |
3114 | @end defun | |
3115 | ||
3116 | A @code{gdb.Frame} object has the following methods: | |
3117 | ||
3118 | @defun Frame.is_valid () | |
3119 | Returns true if the @code{gdb.Frame} object is valid, false if not. | |
3120 | A frame object can become invalid if the frame it refers to doesn't | |
3121 | exist anymore in the inferior. All @code{gdb.Frame} methods will throw | |
3122 | an exception if it is invalid at the time the method is called. | |
3123 | @end defun | |
3124 | ||
3125 | @defun Frame.name () | |
3126 | Returns the function name of the frame, or @code{None} if it can't be | |
3127 | obtained. | |
3128 | @end defun | |
3129 | ||
3130 | @defun Frame.architecture () | |
3131 | Returns the @code{gdb.Architecture} object corresponding to the frame's | |
3132 | architecture. @xref{Architectures In Python}. | |
3133 | @end defun | |
3134 | ||
3135 | @defun Frame.type () | |
3136 | Returns the type of the frame. The value can be one of: | |
3137 | @table @code | |
3138 | @item gdb.NORMAL_FRAME | |
3139 | An ordinary stack frame. | |
3140 | ||
3141 | @item gdb.DUMMY_FRAME | |
3142 | A fake stack frame that was created by @value{GDBN} when performing an | |
3143 | inferior function call. | |
3144 | ||
3145 | @item gdb.INLINE_FRAME | |
3146 | A frame representing an inlined function. The function was inlined | |
3147 | into a @code{gdb.NORMAL_FRAME} that is older than this one. | |
3148 | ||
3149 | @item gdb.TAILCALL_FRAME | |
3150 | A frame representing a tail call. @xref{Tail Call Frames}. | |
3151 | ||
3152 | @item gdb.SIGTRAMP_FRAME | |
3153 | A signal trampoline frame. This is the frame created by the OS when | |
3154 | it calls into a signal handler. | |
3155 | ||
3156 | @item gdb.ARCH_FRAME | |
3157 | A fake stack frame representing a cross-architecture call. | |
3158 | ||
3159 | @item gdb.SENTINEL_FRAME | |
3160 | This is like @code{gdb.NORMAL_FRAME}, but it is only used for the | |
3161 | newest frame. | |
3162 | @end table | |
3163 | @end defun | |
3164 | ||
3165 | @defun Frame.unwind_stop_reason () | |
3166 | Return an integer representing the reason why it's not possible to find | |
3167 | more frames toward the outermost frame. Use | |
3168 | @code{gdb.frame_stop_reason_string} to convert the value returned by this | |
3169 | function to a string. The value can be one of: | |
3170 | ||
3171 | @table @code | |
3172 | @item gdb.FRAME_UNWIND_NO_REASON | |
3173 | No particular reason (older frames should be available). | |
3174 | ||
3175 | @item gdb.FRAME_UNWIND_NULL_ID | |
3176 | The previous frame's analyzer returns an invalid result. This is no | |
3177 | longer used by @value{GDBN}, and is kept only for backward | |
3178 | compatibility. | |
3179 | ||
3180 | @item gdb.FRAME_UNWIND_OUTERMOST | |
3181 | This frame is the outermost. | |
3182 | ||
3183 | @item gdb.FRAME_UNWIND_UNAVAILABLE | |
3184 | Cannot unwind further, because that would require knowing the | |
3185 | values of registers or memory that have not been collected. | |
3186 | ||
3187 | @item gdb.FRAME_UNWIND_INNER_ID | |
3188 | This frame ID looks like it ought to belong to a NEXT frame, | |
3189 | but we got it for a PREV frame. Normally, this is a sign of | |
3190 | unwinder failure. It could also indicate stack corruption. | |
3191 | ||
3192 | @item gdb.FRAME_UNWIND_SAME_ID | |
3193 | This frame has the same ID as the previous one. That means | |
3194 | that unwinding further would almost certainly give us another | |
3195 | frame with exactly the same ID, so break the chain. Normally, | |
3196 | this is a sign of unwinder failure. It could also indicate | |
3197 | stack corruption. | |
3198 | ||
3199 | @item gdb.FRAME_UNWIND_NO_SAVED_PC | |
3200 | The frame unwinder did not find any saved PC, but we needed | |
3201 | one to unwind further. | |
3202 | ||
3203 | @item gdb.FRAME_UNWIND_FIRST_ERROR | |
3204 | Any stop reason greater or equal to this value indicates some kind | |
3205 | of error. This special value facilitates writing code that tests | |
3206 | for errors in unwinding in a way that will work correctly even if | |
3207 | the list of the other values is modified in future @value{GDBN} | |
3208 | versions. Using it, you could write: | |
3209 | @smallexample | |
3210 | reason = gdb.selected_frame().unwind_stop_reason () | |
3211 | reason_str = gdb.frame_stop_reason_string (reason) | |
3212 | if reason >= gdb.FRAME_UNWIND_FIRST_ERROR: | |
3213 | print "An error occured: %s" % reason_str | |
3214 | @end smallexample | |
3215 | @end table | |
3216 | ||
3217 | @end defun | |
3218 | ||
3219 | @defun Frame.pc () | |
3220 | Returns the frame's resume address. | |
3221 | @end defun | |
3222 | ||
3223 | @defun Frame.block () | |
3224 | Return the frame's code block. @xref{Blocks In Python}. | |
3225 | @end defun | |
3226 | ||
3227 | @defun Frame.function () | |
3228 | Return the symbol for the function corresponding to this frame. | |
3229 | @xref{Symbols In Python}. | |
3230 | @end defun | |
3231 | ||
3232 | @defun Frame.older () | |
3233 | Return the frame that called this frame. | |
3234 | @end defun | |
3235 | ||
3236 | @defun Frame.newer () | |
3237 | Return the frame called by this frame. | |
3238 | @end defun | |
3239 | ||
3240 | @defun Frame.find_sal () | |
3241 | Return the frame's symtab and line object. | |
3242 | @xref{Symbol Tables In Python}. | |
3243 | @end defun | |
3244 | ||
3245 | @defun Frame.read_var (variable @r{[}, block@r{]}) | |
3246 | Return the value of @var{variable} in this frame. If the optional | |
3247 | argument @var{block} is provided, search for the variable from that | |
3248 | block; otherwise start at the frame's current block (which is | |
3249 | determined by the frame's current program counter). @var{variable} | |
3250 | must be a string or a @code{gdb.Symbol} object. @var{block} must be a | |
3251 | @code{gdb.Block} object. | |
3252 | @end defun | |
3253 | ||
3254 | @defun Frame.select () | |
3255 | Set this frame to be the selected frame. @xref{Stack, ,Examining the | |
3256 | Stack}. | |
3257 | @end defun | |
3258 | ||
3259 | @node Blocks In Python | |
3260 | @subsubsection Accessing blocks from Python. | |
3261 | ||
3262 | @cindex blocks in python | |
3263 | @tindex gdb.Block | |
3264 | ||
3265 | In @value{GDBN}, symbols are stored in blocks. A block corresponds | |
3266 | roughly to a scope in the source code. Blocks are organized | |
3267 | hierarchically, and are represented individually in Python as a | |
3268 | @code{gdb.Block}. Blocks rely on debugging information being | |
3269 | available. | |
3270 | ||
3271 | A frame has a block. Please see @ref{Frames In Python}, for a more | |
3272 | in-depth discussion of frames. | |
3273 | ||
3274 | The outermost block is known as the @dfn{global block}. The global | |
3275 | block typically holds public global variables and functions. | |
3276 | ||
3277 | The block nested just inside the global block is the @dfn{static | |
3278 | block}. The static block typically holds file-scoped variables and | |
3279 | functions. | |
3280 | ||
3281 | @value{GDBN} provides a method to get a block's superblock, but there | |
3282 | is currently no way to examine the sub-blocks of a block, or to | |
3283 | iterate over all the blocks in a symbol table (@pxref{Symbol Tables In | |
3284 | Python}). | |
3285 | ||
3286 | Here is a short example that should help explain blocks: | |
3287 | ||
3288 | @smallexample | |
3289 | /* This is in the global block. */ | |
3290 | int global; | |
3291 | ||
3292 | /* This is in the static block. */ | |
3293 | static int file_scope; | |
3294 | ||
3295 | /* 'function' is in the global block, and 'argument' is | |
3296 | in a block nested inside of 'function'. */ | |
3297 | int function (int argument) | |
3298 | @{ | |
3299 | /* 'local' is in a block inside 'function'. It may or may | |
3300 | not be in the same block as 'argument'. */ | |
3301 | int local; | |
3302 | ||
3303 | @{ | |
3304 | /* 'inner' is in a block whose superblock is the one holding | |
3305 | 'local'. */ | |
3306 | int inner; | |
3307 | ||
3308 | /* If this call is expanded by the compiler, you may see | |
3309 | a nested block here whose function is 'inline_function' | |
3310 | and whose superblock is the one holding 'inner'. */ | |
3311 | inline_function (); | |
3312 | @} | |
3313 | @} | |
3314 | @end smallexample | |
3315 | ||
3316 | A @code{gdb.Block} is iterable. The iterator returns the symbols | |
3317 | (@pxref{Symbols In Python}) local to the block. Python programs | |
3318 | should not assume that a specific block object will always contain a | |
3319 | given symbol, since changes in @value{GDBN} features and | |
3320 | infrastructure may cause symbols move across blocks in a symbol | |
3321 | table. | |
3322 | ||
3323 | The following block-related functions are available in the @code{gdb} | |
3324 | module: | |
3325 | ||
3326 | @findex gdb.block_for_pc | |
3327 | @defun gdb.block_for_pc (pc) | |
3328 | Return the innermost @code{gdb.Block} containing the given @var{pc} | |
3329 | value. If the block cannot be found for the @var{pc} value specified, | |
3330 | the function will return @code{None}. | |
3331 | @end defun | |
3332 | ||
3333 | A @code{gdb.Block} object has the following methods: | |
3334 | ||
3335 | @defun Block.is_valid () | |
3336 | Returns @code{True} if the @code{gdb.Block} object is valid, | |
3337 | @code{False} if not. A block object can become invalid if the block it | |
3338 | refers to doesn't exist anymore in the inferior. All other | |
3339 | @code{gdb.Block} methods will throw an exception if it is invalid at | |
3340 | the time the method is called. The block's validity is also checked | |
3341 | during iteration over symbols of the block. | |
3342 | @end defun | |
3343 | ||
3344 | A @code{gdb.Block} object has the following attributes: | |
3345 | ||
3346 | @defvar Block.start | |
3347 | The start address of the block. This attribute is not writable. | |
3348 | @end defvar | |
3349 | ||
3350 | @defvar Block.end | |
3351 | The end address of the block. This attribute is not writable. | |
3352 | @end defvar | |
3353 | ||
3354 | @defvar Block.function | |
3355 | The name of the block represented as a @code{gdb.Symbol}. If the | |
3356 | block is not named, then this attribute holds @code{None}. This | |
3357 | attribute is not writable. | |
3358 | ||
3359 | For ordinary function blocks, the superblock is the static block. | |
3360 | However, you should note that it is possible for a function block to | |
3361 | have a superblock that is not the static block -- for instance this | |
3362 | happens for an inlined function. | |
3363 | @end defvar | |
3364 | ||
3365 | @defvar Block.superblock | |
3366 | The block containing this block. If this parent block does not exist, | |
3367 | this attribute holds @code{None}. This attribute is not writable. | |
3368 | @end defvar | |
3369 | ||
3370 | @defvar Block.global_block | |
3371 | The global block associated with this block. This attribute is not | |
3372 | writable. | |
3373 | @end defvar | |
3374 | ||
3375 | @defvar Block.static_block | |
3376 | The static block associated with this block. This attribute is not | |
3377 | writable. | |
3378 | @end defvar | |
3379 | ||
3380 | @defvar Block.is_global | |
3381 | @code{True} if the @code{gdb.Block} object is a global block, | |
3382 | @code{False} if not. This attribute is not | |
3383 | writable. | |
3384 | @end defvar | |
3385 | ||
3386 | @defvar Block.is_static | |
3387 | @code{True} if the @code{gdb.Block} object is a static block, | |
3388 | @code{False} if not. This attribute is not writable. | |
3389 | @end defvar | |
3390 | ||
3391 | @node Symbols In Python | |
3392 | @subsubsection Python representation of Symbols. | |
3393 | ||
3394 | @cindex symbols in python | |
3395 | @tindex gdb.Symbol | |
3396 | ||
3397 | @value{GDBN} represents every variable, function and type as an | |
3398 | entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}. | |
3399 | Similarly, Python represents these symbols in @value{GDBN} with the | |
3400 | @code{gdb.Symbol} object. | |
3401 | ||
3402 | The following symbol-related functions are available in the @code{gdb} | |
3403 | module: | |
3404 | ||
3405 | @findex gdb.lookup_symbol | |
3406 | @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]}) | |
3407 | This function searches for a symbol by name. The search scope can be | |
3408 | restricted to the parameters defined in the optional domain and block | |
3409 | arguments. | |
3410 | ||
3411 | @var{name} is the name of the symbol. It must be a string. The | |
3412 | optional @var{block} argument restricts the search to symbols visible | |
3413 | in that @var{block}. The @var{block} argument must be a | |
3414 | @code{gdb.Block} object. If omitted, the block for the current frame | |
3415 | is used. The optional @var{domain} argument restricts | |
3416 | the search to the domain type. The @var{domain} argument must be a | |
3417 | domain constant defined in the @code{gdb} module and described later | |
3418 | in this chapter. | |
3419 | ||
3420 | The result is a tuple of two elements. | |
3421 | The first element is a @code{gdb.Symbol} object or @code{None} if the symbol | |
3422 | is not found. | |
3423 | If the symbol is found, the second element is @code{True} if the symbol | |
3424 | is a field of a method's object (e.g., @code{this} in C@t{++}), | |
3425 | otherwise it is @code{False}. | |
3426 | If the symbol is not found, the second element is @code{False}. | |
3427 | @end defun | |
3428 | ||
3429 | @findex gdb.lookup_global_symbol | |
3430 | @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]}) | |
3431 | This function searches for a global symbol by name. | |
3432 | The search scope can be restricted to by the domain argument. | |
3433 | ||
3434 | @var{name} is the name of the symbol. It must be a string. | |
3435 | The optional @var{domain} argument restricts the search to the domain type. | |
3436 | The @var{domain} argument must be a domain constant defined in the @code{gdb} | |
3437 | module and described later in this chapter. | |
3438 | ||
3439 | The result is a @code{gdb.Symbol} object or @code{None} if the symbol | |
3440 | is not found. | |
3441 | @end defun | |
3442 | ||
3443 | A @code{gdb.Symbol} object has the following attributes: | |
3444 | ||
3445 | @defvar Symbol.type | |
3446 | The type of the symbol or @code{None} if no type is recorded. | |
3447 | This attribute is represented as a @code{gdb.Type} object. | |
3448 | @xref{Types In Python}. This attribute is not writable. | |
3449 | @end defvar | |
3450 | ||
3451 | @defvar Symbol.symtab | |
3452 | The symbol table in which the symbol appears. This attribute is | |
3453 | represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In | |
3454 | Python}. This attribute is not writable. | |
3455 | @end defvar | |
3456 | ||
3457 | @defvar Symbol.line | |
3458 | The line number in the source code at which the symbol was defined. | |
3459 | This is an integer. | |
3460 | @end defvar | |
3461 | ||
3462 | @defvar Symbol.name | |
3463 | The name of the symbol as a string. This attribute is not writable. | |
3464 | @end defvar | |
3465 | ||
3466 | @defvar Symbol.linkage_name | |
3467 | The name of the symbol, as used by the linker (i.e., may be mangled). | |
3468 | This attribute is not writable. | |
3469 | @end defvar | |
3470 | ||
3471 | @defvar Symbol.print_name | |
3472 | The name of the symbol in a form suitable for output. This is either | |
3473 | @code{name} or @code{linkage_name}, depending on whether the user | |
3474 | asked @value{GDBN} to display demangled or mangled names. | |
3475 | @end defvar | |
3476 | ||
3477 | @defvar Symbol.addr_class | |
3478 | The address class of the symbol. This classifies how to find the value | |
3479 | of a symbol. Each address class is a constant defined in the | |
3480 | @code{gdb} module and described later in this chapter. | |
3481 | @end defvar | |
3482 | ||
3483 | @defvar Symbol.needs_frame | |
3484 | This is @code{True} if evaluating this symbol's value requires a frame | |
3485 | (@pxref{Frames In Python}) and @code{False} otherwise. Typically, | |
3486 | local variables will require a frame, but other symbols will not. | |
3487 | @end defvar | |
3488 | ||
3489 | @defvar Symbol.is_argument | |
3490 | @code{True} if the symbol is an argument of a function. | |
3491 | @end defvar | |
3492 | ||
3493 | @defvar Symbol.is_constant | |
3494 | @code{True} if the symbol is a constant. | |
3495 | @end defvar | |
3496 | ||
3497 | @defvar Symbol.is_function | |
3498 | @code{True} if the symbol is a function or a method. | |
3499 | @end defvar | |
3500 | ||
3501 | @defvar Symbol.is_variable | |
3502 | @code{True} if the symbol is a variable. | |
3503 | @end defvar | |
3504 | ||
3505 | A @code{gdb.Symbol} object has the following methods: | |
3506 | ||
3507 | @defun Symbol.is_valid () | |
3508 | Returns @code{True} if the @code{gdb.Symbol} object is valid, | |
3509 | @code{False} if not. A @code{gdb.Symbol} object can become invalid if | |
3510 | the symbol it refers to does not exist in @value{GDBN} any longer. | |
3511 | All other @code{gdb.Symbol} methods will throw an exception if it is | |
3512 | invalid at the time the method is called. | |
3513 | @end defun | |
3514 | ||
3515 | @defun Symbol.value (@r{[}frame@r{]}) | |
3516 | Compute the value of the symbol, as a @code{gdb.Value}. For | |
3517 | functions, this computes the address of the function, cast to the | |
3518 | appropriate type. If the symbol requires a frame in order to compute | |
3519 | its value, then @var{frame} must be given. If @var{frame} is not | |
3520 | given, or if @var{frame} is invalid, then this method will throw an | |
3521 | exception. | |
3522 | @end defun | |
3523 | ||
3524 | The available domain categories in @code{gdb.Symbol} are represented | |
3525 | as constants in the @code{gdb} module: | |
3526 | ||
b3ce5e5f DE |
3527 | @vtable @code |
3528 | @vindex SYMBOL_UNDEF_DOMAIN | |
329baa95 DE |
3529 | @item gdb.SYMBOL_UNDEF_DOMAIN |
3530 | This is used when a domain has not been discovered or none of the | |
3531 | following domains apply. This usually indicates an error either | |
3532 | in the symbol information or in @value{GDBN}'s handling of symbols. | |
b3ce5e5f DE |
3533 | |
3534 | @vindex SYMBOL_VAR_DOMAIN | |
329baa95 DE |
3535 | @item gdb.SYMBOL_VAR_DOMAIN |
3536 | This domain contains variables, function names, typedef names and enum | |
3537 | type values. | |
b3ce5e5f DE |
3538 | |
3539 | @vindex SYMBOL_STRUCT_DOMAIN | |
329baa95 DE |
3540 | @item gdb.SYMBOL_STRUCT_DOMAIN |
3541 | This domain holds struct, union and enum type names. | |
b3ce5e5f DE |
3542 | |
3543 | @vindex SYMBOL_LABEL_DOMAIN | |
329baa95 DE |
3544 | @item gdb.SYMBOL_LABEL_DOMAIN |
3545 | This domain contains names of labels (for gotos). | |
b3ce5e5f DE |
3546 | |
3547 | @vindex SYMBOL_VARIABLES_DOMAIN | |
329baa95 DE |
3548 | @item gdb.SYMBOL_VARIABLES_DOMAIN |
3549 | This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it | |
3550 | contains everything minus functions and types. | |
b3ce5e5f DE |
3551 | |
3552 | @vindex SYMBOL_FUNCTIONS_DOMAIN | |
329baa95 DE |
3553 | @item gdb.SYMBOL_FUNCTION_DOMAIN |
3554 | This domain contains all functions. | |
b3ce5e5f DE |
3555 | |
3556 | @vindex SYMBOL_TYPES_DOMAIN | |
329baa95 DE |
3557 | @item gdb.SYMBOL_TYPES_DOMAIN |
3558 | This domain contains all types. | |
b3ce5e5f | 3559 | @end vtable |
329baa95 DE |
3560 | |
3561 | The available address class categories in @code{gdb.Symbol} are represented | |
3562 | as constants in the @code{gdb} module: | |
3563 | ||
b3ce5e5f DE |
3564 | @vtable @code |
3565 | @vindex SYMBOL_LOC_UNDEF | |
329baa95 DE |
3566 | @item gdb.SYMBOL_LOC_UNDEF |
3567 | If this is returned by address class, it indicates an error either in | |
3568 | the symbol information or in @value{GDBN}'s handling of symbols. | |
b3ce5e5f DE |
3569 | |
3570 | @vindex SYMBOL_LOC_CONST | |
329baa95 DE |
3571 | @item gdb.SYMBOL_LOC_CONST |
3572 | Value is constant int. | |
b3ce5e5f DE |
3573 | |
3574 | @vindex SYMBOL_LOC_STATIC | |
329baa95 DE |
3575 | @item gdb.SYMBOL_LOC_STATIC |
3576 | Value is at a fixed address. | |
b3ce5e5f DE |
3577 | |
3578 | @vindex SYMBOL_LOC_REGISTER | |
329baa95 DE |
3579 | @item gdb.SYMBOL_LOC_REGISTER |
3580 | Value is in a register. | |
b3ce5e5f DE |
3581 | |
3582 | @vindex SYMBOL_LOC_ARG | |
329baa95 DE |
3583 | @item gdb.SYMBOL_LOC_ARG |
3584 | Value is an argument. This value is at the offset stored within the | |
3585 | symbol inside the frame's argument list. | |
b3ce5e5f DE |
3586 | |
3587 | @vindex SYMBOL_LOC_REF_ARG | |
329baa95 DE |
3588 | @item gdb.SYMBOL_LOC_REF_ARG |
3589 | Value address is stored in the frame's argument list. Just like | |
3590 | @code{LOC_ARG} except that the value's address is stored at the | |
3591 | offset, not the value itself. | |
b3ce5e5f DE |
3592 | |
3593 | @vindex SYMBOL_LOC_REGPARM_ADDR | |
329baa95 DE |
3594 | @item gdb.SYMBOL_LOC_REGPARM_ADDR |
3595 | Value is a specified register. Just like @code{LOC_REGISTER} except | |
3596 | the register holds the address of the argument instead of the argument | |
3597 | itself. | |
b3ce5e5f DE |
3598 | |
3599 | @vindex SYMBOL_LOC_LOCAL | |
329baa95 DE |
3600 | @item gdb.SYMBOL_LOC_LOCAL |
3601 | Value is a local variable. | |
b3ce5e5f DE |
3602 | |
3603 | @vindex SYMBOL_LOC_TYPEDEF | |
329baa95 DE |
3604 | @item gdb.SYMBOL_LOC_TYPEDEF |
3605 | Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all | |
3606 | have this class. | |
b3ce5e5f DE |
3607 | |
3608 | @vindex SYMBOL_LOC_BLOCK | |
329baa95 DE |
3609 | @item gdb.SYMBOL_LOC_BLOCK |
3610 | Value is a block. | |
b3ce5e5f DE |
3611 | |
3612 | @vindex SYMBOL_LOC_CONST_BYTES | |
329baa95 DE |
3613 | @item gdb.SYMBOL_LOC_CONST_BYTES |
3614 | Value is a byte-sequence. | |
b3ce5e5f DE |
3615 | |
3616 | @vindex SYMBOL_LOC_UNRESOLVED | |
329baa95 DE |
3617 | @item gdb.SYMBOL_LOC_UNRESOLVED |
3618 | Value is at a fixed address, but the address of the variable has to be | |
3619 | determined from the minimal symbol table whenever the variable is | |
3620 | referenced. | |
b3ce5e5f DE |
3621 | |
3622 | @vindex SYMBOL_LOC_OPTIMIZED_OUT | |
329baa95 DE |
3623 | @item gdb.SYMBOL_LOC_OPTIMIZED_OUT |
3624 | The value does not actually exist in the program. | |
b3ce5e5f DE |
3625 | |
3626 | @vindex SYMBOL_LOC_COMPUTED | |
329baa95 DE |
3627 | @item gdb.SYMBOL_LOC_COMPUTED |
3628 | The value's address is a computed location. | |
b3ce5e5f | 3629 | @end vtable |
329baa95 DE |
3630 | |
3631 | @node Symbol Tables In Python | |
3632 | @subsubsection Symbol table representation in Python. | |
3633 | ||
3634 | @cindex symbol tables in python | |
3635 | @tindex gdb.Symtab | |
3636 | @tindex gdb.Symtab_and_line | |
3637 | ||
3638 | Access to symbol table data maintained by @value{GDBN} on the inferior | |
3639 | is exposed to Python via two objects: @code{gdb.Symtab_and_line} and | |
3640 | @code{gdb.Symtab}. Symbol table and line data for a frame is returned | |
3641 | from the @code{find_sal} method in @code{gdb.Frame} object. | |
3642 | @xref{Frames In Python}. | |
3643 | ||
3644 | For more information on @value{GDBN}'s symbol table management, see | |
3645 | @ref{Symbols, ,Examining the Symbol Table}, for more information. | |
3646 | ||
3647 | A @code{gdb.Symtab_and_line} object has the following attributes: | |
3648 | ||
3649 | @defvar Symtab_and_line.symtab | |
3650 | The symbol table object (@code{gdb.Symtab}) for this frame. | |
3651 | This attribute is not writable. | |
3652 | @end defvar | |
3653 | ||
3654 | @defvar Symtab_and_line.pc | |
3655 | Indicates the start of the address range occupied by code for the | |
3656 | current source line. This attribute is not writable. | |
3657 | @end defvar | |
3658 | ||
3659 | @defvar Symtab_and_line.last | |
3660 | Indicates the end of the address range occupied by code for the current | |
3661 | source line. This attribute is not writable. | |
3662 | @end defvar | |
3663 | ||
3664 | @defvar Symtab_and_line.line | |
3665 | Indicates the current line number for this object. This | |
3666 | attribute is not writable. | |
3667 | @end defvar | |
3668 | ||
3669 | A @code{gdb.Symtab_and_line} object has the following methods: | |
3670 | ||
3671 | @defun Symtab_and_line.is_valid () | |
3672 | Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid, | |
3673 | @code{False} if not. A @code{gdb.Symtab_and_line} object can become | |
3674 | invalid if the Symbol table and line object it refers to does not | |
3675 | exist in @value{GDBN} any longer. All other | |
3676 | @code{gdb.Symtab_and_line} methods will throw an exception if it is | |
3677 | invalid at the time the method is called. | |
3678 | @end defun | |
3679 | ||
3680 | A @code{gdb.Symtab} object has the following attributes: | |
3681 | ||
3682 | @defvar Symtab.filename | |
3683 | The symbol table's source filename. This attribute is not writable. | |
3684 | @end defvar | |
3685 | ||
3686 | @defvar Symtab.objfile | |
3687 | The symbol table's backing object file. @xref{Objfiles In Python}. | |
3688 | This attribute is not writable. | |
3689 | @end defvar | |
3690 | ||
3691 | A @code{gdb.Symtab} object has the following methods: | |
3692 | ||
3693 | @defun Symtab.is_valid () | |
3694 | Returns @code{True} if the @code{gdb.Symtab} object is valid, | |
3695 | @code{False} if not. A @code{gdb.Symtab} object can become invalid if | |
3696 | the symbol table it refers to does not exist in @value{GDBN} any | |
3697 | longer. All other @code{gdb.Symtab} methods will throw an exception | |
3698 | if it is invalid at the time the method is called. | |
3699 | @end defun | |
3700 | ||
3701 | @defun Symtab.fullname () | |
3702 | Return the symbol table's source absolute file name. | |
3703 | @end defun | |
3704 | ||
3705 | @defun Symtab.global_block () | |
3706 | Return the global block of the underlying symbol table. | |
3707 | @xref{Blocks In Python}. | |
3708 | @end defun | |
3709 | ||
3710 | @defun Symtab.static_block () | |
3711 | Return the static block of the underlying symbol table. | |
3712 | @xref{Blocks In Python}. | |
3713 | @end defun | |
3714 | ||
3715 | @defun Symtab.linetable () | |
3716 | Return the line table associated with the symbol table. | |
3717 | @xref{Line Tables In Python}. | |
3718 | @end defun | |
3719 | ||
3720 | @node Line Tables In Python | |
3721 | @subsubsection Manipulating line tables using Python | |
3722 | ||
3723 | @cindex line tables in python | |
3724 | @tindex gdb.LineTable | |
3725 | ||
3726 | Python code can request and inspect line table information from a | |
3727 | symbol table that is loaded in @value{GDBN}. A line table is a | |
3728 | mapping of source lines to their executable locations in memory. To | |
3729 | acquire the line table information for a particular symbol table, use | |
3730 | the @code{linetable} function (@pxref{Symbol Tables In Python}). | |
3731 | ||
3732 | A @code{gdb.LineTable} is iterable. The iterator returns | |
3733 | @code{LineTableEntry} objects that correspond to the source line and | |
3734 | address for each line table entry. @code{LineTableEntry} objects have | |
3735 | the following attributes: | |
3736 | ||
3737 | @defvar LineTableEntry.line | |
3738 | The source line number for this line table entry. This number | |
3739 | corresponds to the actual line of source. This attribute is not | |
3740 | writable. | |
3741 | @end defvar | |
3742 | ||
3743 | @defvar LineTableEntry.pc | |
3744 | The address that is associated with the line table entry where the | |
3745 | executable code for that source line resides in memory. This | |
3746 | attribute is not writable. | |
3747 | @end defvar | |
3748 | ||
3749 | As there can be multiple addresses for a single source line, you may | |
3750 | receive multiple @code{LineTableEntry} objects with matching | |
3751 | @code{line} attributes, but with different @code{pc} attributes. The | |
3752 | iterator is sorted in ascending @code{pc} order. Here is a small | |
3753 | example illustrating iterating over a line table. | |
3754 | ||
3755 | @smallexample | |
3756 | symtab = gdb.selected_frame().find_sal().symtab | |
3757 | linetable = symtab.linetable() | |
3758 | for line in linetable: | |
3759 | print "Line: "+str(line.line)+" Address: "+hex(line.pc) | |
3760 | @end smallexample | |
3761 | ||
3762 | This will have the following output: | |
3763 | ||
3764 | @smallexample | |
3765 | Line: 33 Address: 0x4005c8L | |
3766 | Line: 37 Address: 0x4005caL | |
3767 | Line: 39 Address: 0x4005d2L | |
3768 | Line: 40 Address: 0x4005f8L | |
3769 | Line: 42 Address: 0x4005ffL | |
3770 | Line: 44 Address: 0x400608L | |
3771 | Line: 42 Address: 0x40060cL | |
3772 | Line: 45 Address: 0x400615L | |
3773 | @end smallexample | |
3774 | ||
3775 | In addition to being able to iterate over a @code{LineTable}, it also | |
3776 | has the following direct access methods: | |
3777 | ||
3778 | @defun LineTable.line (line) | |
3779 | Return a Python @code{Tuple} of @code{LineTableEntry} objects for any | |
3780 | entries in the line table for the given @var{line}. @var{line} refers | |
3781 | to the source code line. If there are no entries for that source code | |
3782 | @var{line}, the Python @code{None} is returned. | |
3783 | @end defun | |
3784 | ||
3785 | @defun LineTable.has_line (line) | |
3786 | Return a Python @code{Boolean} indicating whether there is an entry in | |
3787 | the line table for this source line. Return @code{True} if an entry | |
3788 | is found, or @code{False} if not. | |
3789 | @end defun | |
3790 | ||
3791 | @defun LineTable.source_lines () | |
3792 | Return a Python @code{List} of the source line numbers in the symbol | |
3793 | table. Only lines with executable code locations are returned. The | |
3794 | contents of the @code{List} will just be the source line entries | |
3795 | represented as Python @code{Long} values. | |
3796 | @end defun | |
3797 | ||
3798 | @node Breakpoints In Python | |
3799 | @subsubsection Manipulating breakpoints using Python | |
3800 | ||
3801 | @cindex breakpoints in python | |
3802 | @tindex gdb.Breakpoint | |
3803 | ||
3804 | Python code can manipulate breakpoints via the @code{gdb.Breakpoint} | |
3805 | class. | |
3806 | ||
3807 | @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]}) | |
3808 | Create a new breakpoint. @var{spec} is a string naming the location | |
3809 | of the breakpoint, or an expression that defines a watchpoint. The | |
3810 | contents can be any location recognized by the @code{break} command, | |
3811 | or in the case of a watchpoint, by the @code{watch} command. The | |
3812 | optional @var{type} denotes the breakpoint to create from the types | |
3813 | defined later in this chapter. This argument can be either: | |
3814 | @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type} | |
3815 | defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} | |
3816 | argument allows the breakpoint to become invisible to the user. The | |
3817 | breakpoint will neither be reported when created, nor will it be | |
3818 | listed in the output from @code{info breakpoints} (but will be listed | |
3819 | with the @code{maint info breakpoints} command). The optional | |
3820 | @var{temporary} argument makes the breakpoint a temporary breakpoint. | |
3821 | Temporary breakpoints are deleted after they have been hit. Any | |
3822 | further access to the Python breakpoint after it has been hit will | |
3823 | result in a runtime error (as that breakpoint has now been | |
3824 | automatically deleted). The optional @var{wp_class} argument defines | |
3825 | the class of watchpoint to create, if @var{type} is | |
3826 | @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it | |
3827 | is assumed to be a @code{gdb.WP_WRITE} class. | |
3828 | @end defun | |
3829 | ||
3830 | @defun Breakpoint.stop (self) | |
3831 | The @code{gdb.Breakpoint} class can be sub-classed and, in | |
3832 | particular, you may choose to implement the @code{stop} method. | |
3833 | If this method is defined in a sub-class of @code{gdb.Breakpoint}, | |
3834 | it will be called when the inferior reaches any location of a | |
3835 | breakpoint which instantiates that sub-class. If the method returns | |
3836 | @code{True}, the inferior will be stopped at the location of the | |
3837 | breakpoint, otherwise the inferior will continue. | |
3838 | ||
3839 | If there are multiple breakpoints at the same location with a | |
3840 | @code{stop} method, each one will be called regardless of the | |
3841 | return status of the previous. This ensures that all @code{stop} | |
3842 | methods have a chance to execute at that location. In this scenario | |
3843 | if one of the methods returns @code{True} but the others return | |
3844 | @code{False}, the inferior will still be stopped. | |
3845 | ||
3846 | You should not alter the execution state of the inferior (i.e.@:, step, | |
3847 | next, etc.), alter the current frame context (i.e.@:, change the current | |
3848 | active frame), or alter, add or delete any breakpoint. As a general | |
3849 | rule, you should not alter any data within @value{GDBN} or the inferior | |
3850 | at this time. | |
3851 | ||
3852 | Example @code{stop} implementation: | |
3853 | ||
3854 | @smallexample | |
3855 | class MyBreakpoint (gdb.Breakpoint): | |
3856 | def stop (self): | |
3857 | inf_val = gdb.parse_and_eval("foo") | |
3858 | if inf_val == 3: | |
3859 | return True | |
3860 | return False | |
3861 | @end smallexample | |
3862 | @end defun | |
3863 | ||
3864 | The available watchpoint types represented by constants are defined in the | |
3865 | @code{gdb} module: | |
3866 | ||
b3ce5e5f DE |
3867 | @vtable @code |
3868 | @vindex WP_READ | |
329baa95 DE |
3869 | @item gdb.WP_READ |
3870 | Read only watchpoint. | |
3871 | ||
b3ce5e5f | 3872 | @vindex WP_WRITE |
329baa95 DE |
3873 | @item gdb.WP_WRITE |
3874 | Write only watchpoint. | |
3875 | ||
b3ce5e5f | 3876 | @vindex WP_ACCESS |
329baa95 DE |
3877 | @item gdb.WP_ACCESS |
3878 | Read/Write watchpoint. | |
b3ce5e5f | 3879 | @end vtable |
329baa95 DE |
3880 | |
3881 | @defun Breakpoint.is_valid () | |
3882 | Return @code{True} if this @code{Breakpoint} object is valid, | |
3883 | @code{False} otherwise. A @code{Breakpoint} object can become invalid | |
3884 | if the user deletes the breakpoint. In this case, the object still | |
3885 | exists, but the underlying breakpoint does not. In the cases of | |
3886 | watchpoint scope, the watchpoint remains valid even if execution of the | |
3887 | inferior leaves the scope of that watchpoint. | |
3888 | @end defun | |
3889 | ||
3890 | @defun Breakpoint.delete | |
3891 | Permanently deletes the @value{GDBN} breakpoint. This also | |
3892 | invalidates the Python @code{Breakpoint} object. Any further access | |
3893 | to this object's attributes or methods will raise an error. | |
3894 | @end defun | |
3895 | ||
3896 | @defvar Breakpoint.enabled | |
3897 | This attribute is @code{True} if the breakpoint is enabled, and | |
3898 | @code{False} otherwise. This attribute is writable. | |
3899 | @end defvar | |
3900 | ||
3901 | @defvar Breakpoint.silent | |
3902 | This attribute is @code{True} if the breakpoint is silent, and | |
3903 | @code{False} otherwise. This attribute is writable. | |
3904 | ||
3905 | Note that a breakpoint can also be silent if it has commands and the | |
3906 | first command is @code{silent}. This is not reported by the | |
3907 | @code{silent} attribute. | |
3908 | @end defvar | |
3909 | ||
3910 | @defvar Breakpoint.thread | |
3911 | If the breakpoint is thread-specific, this attribute holds the thread | |
3912 | id. If the breakpoint is not thread-specific, this attribute is | |
3913 | @code{None}. This attribute is writable. | |
3914 | @end defvar | |
3915 | ||
3916 | @defvar Breakpoint.task | |
3917 | If the breakpoint is Ada task-specific, this attribute holds the Ada task | |
3918 | id. If the breakpoint is not task-specific (or the underlying | |
3919 | language is not Ada), this attribute is @code{None}. This attribute | |
3920 | is writable. | |
3921 | @end defvar | |
3922 | ||
3923 | @defvar Breakpoint.ignore_count | |
3924 | This attribute holds the ignore count for the breakpoint, an integer. | |
3925 | This attribute is writable. | |
3926 | @end defvar | |
3927 | ||
3928 | @defvar Breakpoint.number | |
3929 | This attribute holds the breakpoint's number --- the identifier used by | |
3930 | the user to manipulate the breakpoint. This attribute is not writable. | |
3931 | @end defvar | |
3932 | ||
3933 | @defvar Breakpoint.type | |
3934 | This attribute holds the breakpoint's type --- the identifier used to | |
3935 | determine the actual breakpoint type or use-case. This attribute is not | |
3936 | writable. | |
3937 | @end defvar | |
3938 | ||
3939 | @defvar Breakpoint.visible | |
3940 | This attribute tells whether the breakpoint is visible to the user | |
3941 | when set, or when the @samp{info breakpoints} command is run. This | |
3942 | attribute is not writable. | |
3943 | @end defvar | |
3944 | ||
3945 | @defvar Breakpoint.temporary | |
3946 | This attribute indicates whether the breakpoint was created as a | |
3947 | temporary breakpoint. Temporary breakpoints are automatically deleted | |
3948 | after that breakpoint has been hit. Access to this attribute, and all | |
3949 | other attributes and functions other than the @code{is_valid} | |
3950 | function, will result in an error after the breakpoint has been hit | |
3951 | (as it has been automatically deleted). This attribute is not | |
3952 | writable. | |
3953 | @end defvar | |
3954 | ||
3955 | The available types are represented by constants defined in the @code{gdb} | |
3956 | module: | |
3957 | ||
b3ce5e5f DE |
3958 | @vtable @code |
3959 | @vindex BP_BREAKPOINT | |
329baa95 DE |
3960 | @item gdb.BP_BREAKPOINT |
3961 | Normal code breakpoint. | |
3962 | ||
b3ce5e5f | 3963 | @vindex BP_WATCHPOINT |
329baa95 DE |
3964 | @item gdb.BP_WATCHPOINT |
3965 | Watchpoint breakpoint. | |
3966 | ||
b3ce5e5f | 3967 | @vindex BP_HARDWARE_WATCHPOINT |
329baa95 DE |
3968 | @item gdb.BP_HARDWARE_WATCHPOINT |
3969 | Hardware assisted watchpoint. | |
3970 | ||
b3ce5e5f | 3971 | @vindex BP_READ_WATCHPOINT |
329baa95 DE |
3972 | @item gdb.BP_READ_WATCHPOINT |
3973 | Hardware assisted read watchpoint. | |
3974 | ||
b3ce5e5f | 3975 | @vindex BP_ACCESS_WATCHPOINT |
329baa95 DE |
3976 | @item gdb.BP_ACCESS_WATCHPOINT |
3977 | Hardware assisted access watchpoint. | |
b3ce5e5f | 3978 | @end vtable |
329baa95 DE |
3979 | |
3980 | @defvar Breakpoint.hit_count | |
3981 | This attribute holds the hit count for the breakpoint, an integer. | |
3982 | This attribute is writable, but currently it can only be set to zero. | |
3983 | @end defvar | |
3984 | ||
3985 | @defvar Breakpoint.location | |
3986 | This attribute holds the location of the breakpoint, as specified by | |
3987 | the user. It is a string. If the breakpoint does not have a location | |
3988 | (that is, it is a watchpoint) the attribute's value is @code{None}. This | |
3989 | attribute is not writable. | |
3990 | @end defvar | |
3991 | ||
3992 | @defvar Breakpoint.expression | |
3993 | This attribute holds a breakpoint expression, as specified by | |
3994 | the user. It is a string. If the breakpoint does not have an | |
3995 | expression (the breakpoint is not a watchpoint) the attribute's value | |
3996 | is @code{None}. This attribute is not writable. | |
3997 | @end defvar | |
3998 | ||
3999 | @defvar Breakpoint.condition | |
4000 | This attribute holds the condition of the breakpoint, as specified by | |
4001 | the user. It is a string. If there is no condition, this attribute's | |
4002 | value is @code{None}. This attribute is writable. | |
4003 | @end defvar | |
4004 | ||
4005 | @defvar Breakpoint.commands | |
4006 | This attribute holds the commands attached to the breakpoint. If | |
4007 | there are commands, this attribute's value is a string holding all the | |
4008 | commands, separated by newlines. If there are no commands, this | |
4009 | attribute is @code{None}. This attribute is not writable. | |
4010 | @end defvar | |
4011 | ||
4012 | @node Finish Breakpoints in Python | |
4013 | @subsubsection Finish Breakpoints | |
4014 | ||
4015 | @cindex python finish breakpoints | |
4016 | @tindex gdb.FinishBreakpoint | |
4017 | ||
4018 | A finish breakpoint is a temporary breakpoint set at the return address of | |
4019 | a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint} | |
4020 | extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled | |
4021 | and deleted when the execution will run out of the breakpoint scope (i.e.@: | |
4022 | @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered). | |
4023 | Finish breakpoints are thread specific and must be create with the right | |
4024 | thread selected. | |
4025 | ||
4026 | @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]}) | |
4027 | Create a finish breakpoint at the return address of the @code{gdb.Frame} | |
4028 | object @var{frame}. If @var{frame} is not provided, this defaults to the | |
4029 | newest frame. The optional @var{internal} argument allows the breakpoint to | |
4030 | become invisible to the user. @xref{Breakpoints In Python}, for further | |
4031 | details about this argument. | |
4032 | @end defun | |
4033 | ||
4034 | @defun FinishBreakpoint.out_of_scope (self) | |
4035 | In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN} | |
4036 | @code{return} command, @dots{}), a function may not properly terminate, and | |
4037 | thus never hit the finish breakpoint. When @value{GDBN} notices such a | |
4038 | situation, the @code{out_of_scope} callback will be triggered. | |
4039 | ||
4040 | You may want to sub-class @code{gdb.FinishBreakpoint} and override this | |
4041 | method: | |
4042 | ||
4043 | @smallexample | |
4044 | class MyFinishBreakpoint (gdb.FinishBreakpoint) | |
4045 | def stop (self): | |
4046 | print "normal finish" | |
4047 | return True | |
4048 | ||
4049 | def out_of_scope (): | |
4050 | print "abnormal finish" | |
4051 | @end smallexample | |
4052 | @end defun | |
4053 | ||
4054 | @defvar FinishBreakpoint.return_value | |
4055 | When @value{GDBN} is stopped at a finish breakpoint and the frame | |
4056 | used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this | |
4057 | attribute will contain a @code{gdb.Value} object corresponding to the return | |
4058 | value of the function. The value will be @code{None} if the function return | |
4059 | type is @code{void} or if the return value was not computable. This attribute | |
4060 | is not writable. | |
4061 | @end defvar | |
4062 | ||
4063 | @node Lazy Strings In Python | |
4064 | @subsubsection Python representation of lazy strings. | |
4065 | ||
4066 | @cindex lazy strings in python | |
4067 | @tindex gdb.LazyString | |
4068 | ||
4069 | A @dfn{lazy string} is a string whose contents is not retrieved or | |
4070 | encoded until it is needed. | |
4071 | ||
4072 | A @code{gdb.LazyString} is represented in @value{GDBN} as an | |
4073 | @code{address} that points to a region of memory, an @code{encoding} | |
4074 | that will be used to encode that region of memory, and a @code{length} | |
4075 | to delimit the region of memory that represents the string. The | |
4076 | difference between a @code{gdb.LazyString} and a string wrapped within | |
4077 | a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated | |
4078 | differently by @value{GDBN} when printing. A @code{gdb.LazyString} is | |
4079 | retrieved and encoded during printing, while a @code{gdb.Value} | |
4080 | wrapping a string is immediately retrieved and encoded on creation. | |
4081 | ||
4082 | A @code{gdb.LazyString} object has the following functions: | |
4083 | ||
4084 | @defun LazyString.value () | |
4085 | Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value | |
4086 | will point to the string in memory, but will lose all the delayed | |
4087 | retrieval, encoding and handling that @value{GDBN} applies to a | |
4088 | @code{gdb.LazyString}. | |
4089 | @end defun | |
4090 | ||
4091 | @defvar LazyString.address | |
4092 | This attribute holds the address of the string. This attribute is not | |
4093 | writable. | |
4094 | @end defvar | |
4095 | ||
4096 | @defvar LazyString.length | |
4097 | This attribute holds the length of the string in characters. If the | |
4098 | length is -1, then the string will be fetched and encoded up to the | |
4099 | first null of appropriate width. This attribute is not writable. | |
4100 | @end defvar | |
4101 | ||
4102 | @defvar LazyString.encoding | |
4103 | This attribute holds the encoding that will be applied to the string | |
4104 | when the string is printed by @value{GDBN}. If the encoding is not | |
4105 | set, or contains an empty string, then @value{GDBN} will select the | |
4106 | most appropriate encoding when the string is printed. This attribute | |
4107 | is not writable. | |
4108 | @end defvar | |
4109 | ||
4110 | @defvar LazyString.type | |
4111 | This attribute holds the type that is represented by the lazy string's | |
4112 | type. For a lazy string this will always be a pointer type. To | |
4113 | resolve this to the lazy string's character type, use the type's | |
4114 | @code{target} method. @xref{Types In Python}. This attribute is not | |
4115 | writable. | |
4116 | @end defvar | |
4117 | ||
4118 | @node Architectures In Python | |
4119 | @subsubsection Python representation of architectures | |
4120 | @cindex Python architectures | |
4121 | ||
4122 | @value{GDBN} uses architecture specific parameters and artifacts in a | |
4123 | number of its various computations. An architecture is represented | |
4124 | by an instance of the @code{gdb.Architecture} class. | |
4125 | ||
4126 | A @code{gdb.Architecture} class has the following methods: | |
4127 | ||
4128 | @defun Architecture.name () | |
4129 | Return the name (string value) of the architecture. | |
4130 | @end defun | |
4131 | ||
4132 | @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]}) | |
4133 | Return a list of disassembled instructions starting from the memory | |
4134 | address @var{start_pc}. The optional arguments @var{end_pc} and | |
4135 | @var{count} determine the number of instructions in the returned list. | |
4136 | If both the optional arguments @var{end_pc} and @var{count} are | |
4137 | specified, then a list of at most @var{count} disassembled instructions | |
4138 | whose start address falls in the closed memory address interval from | |
4139 | @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not | |
4140 | specified, but @var{count} is specified, then @var{count} number of | |
4141 | instructions starting from the address @var{start_pc} are returned. If | |
4142 | @var{count} is not specified but @var{end_pc} is specified, then all | |
4143 | instructions whose start address falls in the closed memory address | |
4144 | interval from @var{start_pc} to @var{end_pc} are returned. If neither | |
4145 | @var{end_pc} nor @var{count} are specified, then a single instruction at | |
4146 | @var{start_pc} is returned. For all of these cases, each element of the | |
4147 | returned list is a Python @code{dict} with the following string keys: | |
4148 | ||
4149 | @table @code | |
4150 | ||
4151 | @item addr | |
4152 | The value corresponding to this key is a Python long integer capturing | |
4153 | the memory address of the instruction. | |
4154 | ||
4155 | @item asm | |
4156 | The value corresponding to this key is a string value which represents | |
4157 | the instruction with assembly language mnemonics. The assembly | |
4158 | language flavor used is the same as that specified by the current CLI | |
4159 | variable @code{disassembly-flavor}. @xref{Machine Code}. | |
4160 | ||
4161 | @item length | |
4162 | The value corresponding to this key is the length (integer value) of the | |
4163 | instruction in bytes. | |
4164 | ||
4165 | @end table | |
4166 | @end defun | |
4167 | ||
4168 | @node Python Auto-loading | |
4169 | @subsection Python Auto-loading | |
4170 | @cindex Python auto-loading | |
4171 | ||
4172 | When a new object file is read (for example, due to the @code{file} | |
4173 | command, or because the inferior has loaded a shared library), | |
4174 | @value{GDBN} will look for Python support scripts in several ways: | |
4175 | @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section. | |
4176 | @xref{Auto-loading extensions}. | |
4177 | ||
4178 | The auto-loading feature is useful for supplying application-specific | |
4179 | debugging commands and scripts. | |
4180 | ||
4181 | Auto-loading can be enabled or disabled, | |
4182 | and the list of auto-loaded scripts can be printed. | |
4183 | ||
4184 | @table @code | |
4185 | @anchor{set auto-load python-scripts} | |
4186 | @kindex set auto-load python-scripts | |
4187 | @item set auto-load python-scripts [on|off] | |
4188 | Enable or disable the auto-loading of Python scripts. | |
4189 | ||
4190 | @anchor{show auto-load python-scripts} | |
4191 | @kindex show auto-load python-scripts | |
4192 | @item show auto-load python-scripts | |
4193 | Show whether auto-loading of Python scripts is enabled or disabled. | |
4194 | ||
4195 | @anchor{info auto-load python-scripts} | |
4196 | @kindex info auto-load python-scripts | |
4197 | @cindex print list of auto-loaded Python scripts | |
4198 | @item info auto-load python-scripts [@var{regexp}] | |
4199 | Print the list of all Python scripts that @value{GDBN} auto-loaded. | |
4200 | ||
4201 | Also printed is the list of Python scripts that were mentioned in | |
4202 | the @code{.debug_gdb_scripts} section and were not found | |
4203 | (@pxref{dotdebug_gdb_scripts section}). | |
4204 | This is useful because their names are not printed when @value{GDBN} | |
4205 | tries to load them and fails. There may be many of them, and printing | |
4206 | an error message for each one is problematic. | |
4207 | ||
4208 | If @var{regexp} is supplied only Python scripts with matching names are printed. | |
4209 | ||
4210 | Example: | |
4211 | ||
4212 | @smallexample | |
4213 | (gdb) info auto-load python-scripts | |
4214 | Loaded Script | |
4215 | Yes py-section-script.py | |
4216 | full name: /tmp/py-section-script.py | |
4217 | No my-foo-pretty-printers.py | |
4218 | @end smallexample | |
4219 | @end table | |
4220 | ||
4221 | When reading an auto-loaded file, @value{GDBN} sets the | |
4222 | @dfn{current objfile}. This is available via the @code{gdb.current_objfile} | |
4223 | function (@pxref{Objfiles In Python}). This can be useful for | |
4224 | registering objfile-specific pretty-printers and frame-filters. | |
4225 | ||
4226 | @node Python modules | |
4227 | @subsection Python modules | |
4228 | @cindex python modules | |
4229 | ||
4230 | @value{GDBN} comes with several modules to assist writing Python code. | |
4231 | ||
4232 | @menu | |
4233 | * gdb.printing:: Building and registering pretty-printers. | |
4234 | * gdb.types:: Utilities for working with types. | |
4235 | * gdb.prompt:: Utilities for prompt value substitution. | |
4236 | @end menu | |
4237 | ||
4238 | @node gdb.printing | |
4239 | @subsubsection gdb.printing | |
4240 | @cindex gdb.printing | |
4241 | ||
4242 | This module provides a collection of utilities for working with | |
4243 | pretty-printers. | |
4244 | ||
4245 | @table @code | |
4246 | @item PrettyPrinter (@var{name}, @var{subprinters}=None) | |
4247 | This class specifies the API that makes @samp{info pretty-printer}, | |
4248 | @samp{enable pretty-printer} and @samp{disable pretty-printer} work. | |
4249 | Pretty-printers should generally inherit from this class. | |
4250 | ||
4251 | @item SubPrettyPrinter (@var{name}) | |
4252 | For printers that handle multiple types, this class specifies the | |
4253 | corresponding API for the subprinters. | |
4254 | ||
4255 | @item RegexpCollectionPrettyPrinter (@var{name}) | |
4256 | Utility class for handling multiple printers, all recognized via | |
4257 | regular expressions. | |
4258 | @xref{Writing a Pretty-Printer}, for an example. | |
4259 | ||
4260 | @item FlagEnumerationPrinter (@var{name}) | |
4261 | A pretty-printer which handles printing of @code{enum} values. Unlike | |
4262 | @value{GDBN}'s built-in @code{enum} printing, this printer attempts to | |
4263 | work properly when there is some overlap between the enumeration | |
4264 | constants. @var{name} is the name of the printer and also the name of | |
4265 | the @code{enum} type to look up. | |
4266 | ||
4267 | @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False) | |
4268 | Register @var{printer} with the pretty-printer list of @var{obj}. | |
4269 | If @var{replace} is @code{True} then any existing copy of the printer | |
4270 | is replaced. Otherwise a @code{RuntimeError} exception is raised | |
4271 | if a printer with the same name already exists. | |
4272 | @end table | |
4273 | ||
4274 | @node gdb.types | |
4275 | @subsubsection gdb.types | |
4276 | @cindex gdb.types | |
4277 | ||
4278 | This module provides a collection of utilities for working with | |
4279 | @code{gdb.Type} objects. | |
4280 | ||
4281 | @table @code | |
4282 | @item get_basic_type (@var{type}) | |
4283 | Return @var{type} with const and volatile qualifiers stripped, | |
4284 | and with typedefs and C@t{++} references converted to the underlying type. | |
4285 | ||
4286 | C@t{++} example: | |
4287 | ||
4288 | @smallexample | |
4289 | typedef const int const_int; | |
4290 | const_int foo (3); | |
4291 | const_int& foo_ref (foo); | |
4292 | int main () @{ return 0; @} | |
4293 | @end smallexample | |
4294 | ||
4295 | Then in gdb: | |
4296 | ||
4297 | @smallexample | |
4298 | (gdb) start | |
4299 | (gdb) python import gdb.types | |
4300 | (gdb) python foo_ref = gdb.parse_and_eval("foo_ref") | |
4301 | (gdb) python print gdb.types.get_basic_type(foo_ref.type) | |
4302 | int | |
4303 | @end smallexample | |
4304 | ||
4305 | @item has_field (@var{type}, @var{field}) | |
4306 | Return @code{True} if @var{type}, assumed to be a type with fields | |
4307 | (e.g., a structure or union), has field @var{field}. | |
4308 | ||
4309 | @item make_enum_dict (@var{enum_type}) | |
4310 | Return a Python @code{dictionary} type produced from @var{enum_type}. | |
4311 | ||
4312 | @item deep_items (@var{type}) | |
4313 | Returns a Python iterator similar to the standard | |
4314 | @code{gdb.Type.iteritems} method, except that the iterator returned | |
4315 | by @code{deep_items} will recursively traverse anonymous struct or | |
4316 | union fields. For example: | |
4317 | ||
4318 | @smallexample | |
4319 | struct A | |
4320 | @{ | |
4321 | int a; | |
4322 | union @{ | |
4323 | int b0; | |
4324 | int b1; | |
4325 | @}; | |
4326 | @}; | |
4327 | @end smallexample | |
4328 | ||
4329 | @noindent | |
4330 | Then in @value{GDBN}: | |
4331 | @smallexample | |
4332 | (@value{GDBP}) python import gdb.types | |
4333 | (@value{GDBP}) python struct_a = gdb.lookup_type("struct A") | |
4334 | (@value{GDBP}) python print struct_a.keys () | |
4335 | @{['a', '']@} | |
4336 | (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)] | |
4337 | @{['a', 'b0', 'b1']@} | |
4338 | @end smallexample | |
4339 | ||
4340 | @item get_type_recognizers () | |
4341 | Return a list of the enabled type recognizers for the current context. | |
4342 | This is called by @value{GDBN} during the type-printing process | |
4343 | (@pxref{Type Printing API}). | |
4344 | ||
4345 | @item apply_type_recognizers (recognizers, type_obj) | |
4346 | Apply the type recognizers, @var{recognizers}, to the type object | |
4347 | @var{type_obj}. If any recognizer returns a string, return that | |
4348 | string. Otherwise, return @code{None}. This is called by | |
4349 | @value{GDBN} during the type-printing process (@pxref{Type Printing | |
4350 | API}). | |
4351 | ||
4352 | @item register_type_printer (locus, printer) | |
4353 | This is a convenience function to register a type printer. | |
4354 | @var{printer} is the type printer to register. It must implement the | |
4355 | type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in | |
4356 | which case the printer is registered with that objfile; a | |
4357 | @code{gdb.Progspace}, in which case the printer is registered with | |
4358 | that progspace; or @code{None}, in which case the printer is | |
4359 | registered globally. | |
4360 | ||
4361 | @item TypePrinter | |
4362 | This is a base class that implements the type printer protocol. Type | |
4363 | printers are encouraged, but not required, to derive from this class. | |
4364 | It defines a constructor: | |
4365 | ||
4366 | @defmethod TypePrinter __init__ (self, name) | |
4367 | Initialize the type printer with the given name. The new printer | |
4368 | starts in the enabled state. | |
4369 | @end defmethod | |
4370 | ||
4371 | @end table | |
4372 | ||
4373 | @node gdb.prompt | |
4374 | @subsubsection gdb.prompt | |
4375 | @cindex gdb.prompt | |
4376 | ||
4377 | This module provides a method for prompt value-substitution. | |
4378 | ||
4379 | @table @code | |
4380 | @item substitute_prompt (@var{string}) | |
4381 | Return @var{string} with escape sequences substituted by values. Some | |
4382 | escape sequences take arguments. You can specify arguments inside | |
4383 | ``@{@}'' immediately following the escape sequence. | |
4384 | ||
4385 | The escape sequences you can pass to this function are: | |
4386 | ||
4387 | @table @code | |
4388 | @item \\ | |
4389 | Substitute a backslash. | |
4390 | @item \e | |
4391 | Substitute an ESC character. | |
4392 | @item \f | |
4393 | Substitute the selected frame; an argument names a frame parameter. | |
4394 | @item \n | |
4395 | Substitute a newline. | |
4396 | @item \p | |
4397 | Substitute a parameter's value; the argument names the parameter. | |
4398 | @item \r | |
4399 | Substitute a carriage return. | |
4400 | @item \t | |
4401 | Substitute the selected thread; an argument names a thread parameter. | |
4402 | @item \v | |
4403 | Substitute the version of GDB. | |
4404 | @item \w | |
4405 | Substitute the current working directory. | |
4406 | @item \[ | |
4407 | Begin a sequence of non-printing characters. These sequences are | |
4408 | typically used with the ESC character, and are not counted in the string | |
4409 | length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a | |
4410 | blue-colored ``(gdb)'' prompt where the length is five. | |
4411 | @item \] | |
4412 | End a sequence of non-printing characters. | |
4413 | @end table | |
4414 | ||
4415 | For example: | |
4416 | ||
4417 | @smallexample | |
4418 | substitute_prompt (``frame: \f, | |
4419 | print arguments: \p@{print frame-arguments@}'') | |
4420 | @end smallexample | |
4421 | ||
4422 | @exdent will return the string: | |
4423 | ||
4424 | @smallexample | |
4425 | "frame: main, print arguments: scalars" | |
4426 | @end smallexample | |
4427 | @end table |