1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. 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In this 79situation, a Python <code>KeyboardInterrupt</code> exception is thrown. 80</p> 81<p>Some care must be taken when writing Python code to run in 82<small>GDB</small>. Two things worth noting in particular: 83</p> 84<ul> 85<li> <small>GDB</small> install handlers for <code>SIGCHLD</code> and <code>SIGINT</code>. 86Python code must not override these, or even change the options using 87<code>sigaction</code>. If your program changes the handling of these 88signals, <small>GDB</small> will most likely stop working correctly. Note 89that it is unfortunately common for GUI toolkits to install a 90<code>SIGCHLD</code> handler. 91 92</li><li> <small>GDB</small> takes care to mark its internal file descriptors as 93close-on-exec. However, this cannot be done in a thread-safe way on 94all platforms. Your Python programs should be aware of this and 95should both create new file descriptors with the close-on-exec flag 96set and arrange to close unneeded file descriptors before starting a 97child process. 98</li></ul> 99 100<a name="index-python-functions"></a> 101<a name="index-python-module"></a> 102<a name="index-gdb-module"></a> 103<p><small>GDB</small> introduces a new Python module, named <code>gdb</code>. All 104methods and classes added by <small>GDB</small> are placed in this module. 105<small>GDB</small> automatically <code>import</code>s the <code>gdb</code> module for 106use in all scripts evaluated by the <code>python</code> command. 107</p> 108<p>Some types of the <code>gdb</code> module come with a textual representation 109(accessible through the <code>repr</code> or <code>str</code> functions). These are 110offered for debugging purposes only, expect them to change over time. 111</p> 112<a name="index-gdb_002ePYTHONDIR"></a> 113<dl> 114<dt><a name="index-gdb_002ePYTHONDIR-1"></a>Variable: <strong>gdb.PYTHONDIR</strong></dt> 115<dd><p>A string containing the python directory (see <a href="Python.html#Python">Python</a>). 116</p></dd></dl> 117 118<a name="index-gdb_002eexecute"></a> 119<dl> 120<dt><a name="index-gdb_002eexecute-1"></a>Function: <strong>gdb.execute</strong> <em>(command <span class="roman">[</span>, from_tty <span class="roman">[</span>, to_string<span class="roman">]]</span>)</em></dt> 121<dd><p>Evaluate <var>command</var>, a string, as a <small>GDB</small> CLI command. 122If a GDB exception happens while <var>command</var> runs, it is 123translated as described in <a href="Exception-Handling.html#Exception-Handling">Exception Handling</a>. 124</p> 125<p>The <var>from_tty</var> flag specifies whether <small>GDB</small> ought to consider this 126command as having originated from the user invoking it interactively. 127It must be a boolean value. If omitted, it defaults to <code>False</code>. 128</p> 129<p>By default, any output produced by <var>command</var> is sent to 130<small>GDB</small>’s standard output (and to the log output if logging is 131turned on). If the <var>to_string</var> parameter is 132<code>True</code>, then output will be collected by <code>gdb.execute</code> and 133returned as a string. The default is <code>False</code>, in which case the 134return value is <code>None</code>. If <var>to_string</var> is <code>True</code>, the 135<small>GDB</small> virtual terminal will be temporarily set to unlimited width 136and height, and its pagination will be disabled; see <a href="Screen-Size.html#Screen-Size">Screen Size</a>. 137</p></dd></dl> 138 139<a name="index-gdb_002ebreakpoints"></a> 140<dl> 141<dt><a name="index-gdb_002ebreakpoints-1"></a>Function: <strong>gdb.breakpoints</strong> <em>()</em></dt> 142<dd><p>Return a sequence holding all of <small>GDB</small>’s breakpoints. 143See <a href="Breakpoints-In-Python.html#Breakpoints-In-Python">Breakpoints In Python</a>, for more information. In <small>GDB</small> 144version 7.11 and earlier, this function returned <code>None</code> if there 145were no breakpoints. This peculiarity was subsequently fixed, and now 146<code>gdb.breakpoints</code> returns an empty sequence in this case. 147</p></dd></dl> 148 149<dl> 150<dt><a name="index-gdb_002erbreak"></a>Function: <strong>gdb.rbreak</strong> <em>(regex <span class="roman">[</span>, minsyms <span class="roman">[</span>, throttle, <span class="roman">[</span>, symtabs <span class="roman">]]]</span>)</em></dt> 151<dd><p>Return a Python list holding a collection of newly set 152<code>gdb.Breakpoint</code> objects matching function names defined by the 153<var>regex</var> pattern. If the <var>minsyms</var> keyword is <code>True</code>, all 154system functions (those not explicitly defined in the inferior) will 155also be included in the match. The <var>throttle</var> keyword takes an 156integer that defines the maximum number of pattern matches for 157functions matched by the <var>regex</var> pattern. If the number of 158matches exceeds the integer value of <var>throttle</var>, a 159<code>RuntimeError</code> will be raised and no breakpoints will be created. 160If <var>throttle</var> is not defined then there is no imposed limit on the 161maximum number of matches and breakpoints to be created. The 162<var>symtabs</var> keyword takes a Python iterable that yields a collection 163of <code>gdb.Symtab</code> objects and will restrict the search to those 164functions only contained within the <code>gdb.Symtab</code> objects. 165</p></dd></dl> 166 167<a name="index-gdb_002eparameter"></a> 168<dl> 169<dt><a name="index-gdb_002eparameter-1"></a>Function: <strong>gdb.parameter</strong> <em>(parameter)</em></dt> 170<dd><p>Return the value of a <small>GDB</small> <var>parameter</var> given by its name, 171a string; the parameter name string may contain spaces if the parameter has a 172multi-part name. For example, ‘<samp>print object</samp>’ is a valid 173parameter name. 174</p> 175<p>If the named parameter does not exist, this function throws a 176<code>gdb.error</code> (see <a href="Exception-Handling.html#Exception-Handling">Exception Handling</a>). Otherwise, the 177parameter’s value is converted to a Python value of the appropriate 178type, and returned. 179</p></dd></dl> 180 181<a name="index-gdb_002ehistory"></a> 182<dl> 183<dt><a name="index-gdb_002ehistory-1"></a>Function: <strong>gdb.history</strong> <em>(number)</em></dt> 184<dd><p>Return a value from <small>GDB</small>’s value history (see <a href="Value-History.html#Value-History">Value History</a>). The <var>number</var> argument indicates which history element to return. 185If <var>number</var> is negative, then <small>GDB</small> will take its absolute value 186and count backward from the last element (i.e., the most recent element) to 187find the value to return. If <var>number</var> is zero, then <small>GDB</small> will 188return the most recent element. If the element specified by <var>number</var> 189doesn’t exist in the value history, a <code>gdb.error</code> exception will be 190raised. 191</p> 192<p>If no exception is raised, the return value is always an instance of 193<code>gdb.Value</code> (see <a href="Values-From-Inferior.html#Values-From-Inferior">Values From Inferior</a>). 194</p></dd></dl> 195 196<a name="index-gdb_002econvenience_005fvariable"></a> 197<dl> 198<dt><a name="index-gdb_002econvenience_005fvariable-1"></a>Function: <strong>gdb.convenience_variable</strong> <em>(name)</em></dt> 199<dd><p>Return the value of the convenience variable (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Vars</a>) named <var>name</var>. <var>name</var> must be a string. The name 200should not include the ‘<samp>$</samp>’ that is used to mark a convenience 201variable in an expression. If the convenience variable does not 202exist, then <code>None</code> is returned. 203</p></dd></dl> 204 205<a name="index-gdb_002eset_005fconvenience_005fvariable"></a> 206<dl> 207<dt><a name="index-gdb_002eset_005fconvenience_005fvariable-1"></a>Function: <strong>gdb.set_convenience_variable</strong> <em>(name, value)</em></dt> 208<dd><p>Set the value of the convenience variable (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Vars</a>) 209named <var>name</var>. <var>name</var> must be a string. The name should not 210include the ‘<samp>$</samp>’ that is used to mark a convenience variable in an 211expression. If <var>value</var> is <code>None</code>, then the convenience 212variable is removed. Otherwise, if <var>value</var> is not a 213<code>gdb.Value</code> (see <a href="Values-From-Inferior.html#Values-From-Inferior">Values From Inferior</a>), it is is converted 214using the <code>gdb.Value</code> constructor. 215</p></dd></dl> 216 217<a name="index-gdb_002eparse_005fand_005feval"></a> 218<dl> 219<dt><a name="index-gdb_002eparse_005fand_005feval-1"></a>Function: <strong>gdb.parse_and_eval</strong> <em>(expression)</em></dt> 220<dd><p>Parse <var>expression</var>, which must be a string, as an expression in 221the current language, evaluate it, and return the result as a 222<code>gdb.Value</code>. 223</p> 224<p>This function can be useful when implementing a new command 225(see <a href="Commands-In-Python.html#Commands-In-Python">Commands In Python</a>), as it provides a way to parse the 226command’s argument as an expression. It is also useful simply to 227compute values. 228</p></dd></dl> 229 230<a name="index-gdb_002efind_005fpc_005fline"></a> 231<dl> 232<dt><a name="index-gdb_002efind_005fpc_005fline-1"></a>Function: <strong>gdb.find_pc_line</strong> <em>(pc)</em></dt> 233<dd><p>Return the <code>gdb.Symtab_and_line</code> object corresponding to the 234<var>pc</var> value. See <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>. If an invalid 235value of <var>pc</var> is passed as an argument, then the <code>symtab</code> and 236<code>line</code> attributes of the returned <code>gdb.Symtab_and_line</code> object 237will be <code>None</code> and 0 respectively. This is identical to 238<code>gdb.current_progspace().find_pc_line(pc)</code> and is included for 239historical compatibility. 240</p></dd></dl> 241 242<a name="index-gdb_002epost_005fevent"></a> 243<dl> 244<dt><a name="index-gdb_002epost_005fevent-1"></a>Function: <strong>gdb.post_event</strong> <em>(event)</em></dt> 245<dd><p>Put <var>event</var>, a callable object taking no arguments, into 246<small>GDB</small>’s internal event queue. This callable will be invoked at 247some later point, during <small>GDB</small>’s event processing. Events 248posted using <code>post_event</code> will be run in the order in which they 249were posted; however, there is no way to know when they will be 250processed relative to other events inside <small>GDB</small>. 251</p> 252<p><small>GDB</small> is not thread-safe. If your Python program uses multiple 253threads, you must be careful to only call <small>GDB</small>-specific 254functions in the <small>GDB</small> thread. <code>post_event</code> ensures 255this. For example: 256</p> 257<div class="smallexample"> 258<pre class="smallexample">(gdb) python 259>import threading 260> 261>class Writer(): 262> def __init__(self, message): 263> self.message = message; 264> def __call__(self): 265> gdb.write(self.message) 266> 267>class MyThread1 (threading.Thread): 268> def run (self): 269> gdb.post_event(Writer("Hello ")) 270> 271>class MyThread2 (threading.Thread): 272> def run (self): 273> gdb.post_event(Writer("World\n")) 274> 275>MyThread1().start() 276>MyThread2().start() 277>end 278(gdb) Hello World 279</pre></div> 280</dd></dl> 281 282<a name="index-gdb_002ewrite"></a> 283<dl> 284<dt><a name="index-gdb_002ewrite-1"></a>Function: <strong>gdb.write</strong> <em>(string <span class="roman">[</span>, stream])</em></dt> 285<dd><p>Print a string to <small>GDB</small>’s paginated output stream. The 286optional <var>stream</var> determines the stream to print to. The default 287stream is <small>GDB</small>’s standard output stream. Possible stream 288values are: 289</p> 290<dl compact="compact"> 291<dd><a name="index-STDOUT"></a> 292<a name="index-gdb_002eSTDOUT"></a> 293</dd> 294<dt><code>gdb.STDOUT</code></dt> 295<dd><p><small>GDB</small>’s standard output stream. 296</p> 297<a name="index-STDERR"></a> 298<a name="index-gdb_002eSTDERR"></a> 299</dd> 300<dt><code>gdb.STDERR</code></dt> 301<dd><p><small>GDB</small>’s standard error stream. 302</p> 303<a name="index-STDLOG"></a> 304<a name="index-gdb_002eSTDLOG"></a> 305</dd> 306<dt><code>gdb.STDLOG</code></dt> 307<dd><p><small>GDB</small>’s log stream (see <a href="Logging-Output.html#Logging-Output">Logging Output</a>). 308</p></dd> 309</dl> 310 311<p>Writing to <code>sys.stdout</code> or <code>sys.stderr</code> will automatically 312call this function and will automatically direct the output to the 313relevant stream. 314</p></dd></dl> 315 316<a name="index-gdb_002eflush"></a> 317<dl> 318<dt><a name="index-gdb_002eflush-1"></a>Function: <strong>gdb.flush</strong> <em>()</em></dt> 319<dd><p>Flush the buffer of a <small>GDB</small> paginated stream so that the 320contents are displayed immediately. <small>GDB</small> will flush the 321contents of a stream automatically when it encounters a newline in the 322buffer. The optional <var>stream</var> determines the stream to flush. The 323default stream is <small>GDB</small>’s standard output stream. Possible 324stream values are: 325</p> 326<dl compact="compact"> 327<dd><a name="index-STDOUT-1"></a> 328<a name="index-gdb_002eSTDOUT-1"></a> 329</dd> 330<dt><code>gdb.STDOUT</code></dt> 331<dd><p><small>GDB</small>’s standard output stream. 332</p> 333<a name="index-STDERR-1"></a> 334<a name="index-gdb_002eSTDERR-1"></a> 335</dd> 336<dt><code>gdb.STDERR</code></dt> 337<dd><p><small>GDB</small>’s standard error stream. 338</p> 339<a name="index-STDLOG-1"></a> 340<a name="index-gdb_002eSTDLOG-1"></a> 341</dd> 342<dt><code>gdb.STDLOG</code></dt> 343<dd><p><small>GDB</small>’s log stream (see <a href="Logging-Output.html#Logging-Output">Logging Output</a>). 344</p> 345</dd> 346</dl> 347 348<p>Flushing <code>sys.stdout</code> or <code>sys.stderr</code> will automatically 349call this function for the relevant stream. 350</p></dd></dl> 351 352<a name="index-gdb_002etarget_005fcharset"></a> 353<dl> 354<dt><a name="index-gdb_002etarget_005fcharset-1"></a>Function: <strong>gdb.target_charset</strong> <em>()</em></dt> 355<dd><p>Return the name of the current target character set (see <a href="Character-Sets.html#Character-Sets">Character Sets</a>). This differs from <code>gdb.parameter('target-charset')</code> in 356that ‘<samp>auto</samp>’ is never returned. 357</p></dd></dl> 358 359<a name="index-gdb_002etarget_005fwide_005fcharset"></a> 360<dl> 361<dt><a name="index-gdb_002etarget_005fwide_005fcharset-1"></a>Function: <strong>gdb.target_wide_charset</strong> <em>()</em></dt> 362<dd><p>Return the name of the current target wide character set 363(see <a href="Character-Sets.html#Character-Sets">Character Sets</a>). This differs from 364<code>gdb.parameter('target-wide-charset')</code> in that ‘<samp>auto</samp>’ is 365never returned. 366</p></dd></dl> 367 368<a name="index-gdb_002esolib_005fname"></a> 369<dl> 370<dt><a name="index-gdb_002esolib_005fname-1"></a>Function: <strong>gdb.solib_name</strong> <em>(address)</em></dt> 371<dd><p>Return the name of the shared library holding the given <var>address</var> 372as a string, or <code>None</code>. This is identical to 373<code>gdb.current_progspace().solib_name(address)</code> and is included for 374historical compatibility. 375</p></dd></dl> 376 377<a name="index-gdb_002edecode_005fline"></a> 378<dl> 379<dt><a name="index-gdb_002edecode_005fline-1"></a>Function: <strong>gdb.decode_line</strong> <em>(<span class="roman">[</span>expression<span class="roman">]</span>)</em></dt> 380<dd><p>Return locations of the line specified by <var>expression</var>, or of the 381current line if no argument was given. This function returns a Python 382tuple containing two elements. The first element contains a string 383holding any unparsed section of <var>expression</var> (or <code>None</code> if 384the expression has been fully parsed). The second element contains 385either <code>None</code> or another tuple that contains all the locations 386that match the expression represented as <code>gdb.Symtab_and_line</code> 387objects (see <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>). If <var>expression</var> is 388provided, it is decoded the way that <small>GDB</small>’s inbuilt 389<code>break</code> or <code>edit</code> commands do (see <a href="Specify-Location.html#Specify-Location">Specify Location</a>). 390</p></dd></dl> 391 392<dl> 393<dt><a name="index-gdb_002eprompt_005fhook"></a>Function: <strong>gdb.prompt_hook</strong> <em>(current_prompt)</em></dt> 394<dd><a name="prompt_005fhook"></a> 395<p>If <var>prompt_hook</var> is callable, <small>GDB</small> will call the method 396assigned to this operation before a prompt is displayed by 397<small>GDB</small>. 398</p> 399<p>The parameter <code>current_prompt</code> contains the current <small>GDB</small> 400prompt. This method must return a Python string, or <code>None</code>. If 401a string is returned, the <small>GDB</small> prompt will be set to that 402string. If <code>None</code> is returned, <small>GDB</small> will continue to use 403the current prompt. 404</p> 405<p>Some prompts cannot be substituted in <small>GDB</small>. Secondary prompts 406such as those used by readline for command input, and annotation 407related prompts are prohibited from being changed. 408</p></dd></dl> 409 410<hr> 411<div class="header"> 412<p> 413Next: <a href="Exception-Handling.html#Exception-Handling" accesskey="n" rel="next">Exception Handling</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> 414</div> 415 416 417 418</body> 419</html> 420