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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These 75have a syntax similar to convenience variables. A convenience 76function can be used in an expression just like an ordinary function; 77however, a convenience function is implemented internally to 78<small>GDB</small>. 79</p> 80<p>These functions do not require <small>GDB</small> to be configured with 81<code>Python</code> support, which means that they are always available. 82</p> 83<dl compact="compact"> 84<dt><code>$_isvoid (<var>expr</var>)</code></dt> 85<dd><a name="index-_0024_005fisvoid_002c-convenience-function"></a> 86<p>Return one if the expression <var>expr</var> is <code>void</code>. Otherwise it 87returns zero. 88</p> 89<p>A <code>void</code> expression is an expression where the type of the result 90is <code>void</code>. For example, you can examine a convenience variable 91(see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Variables</a>) to check whether 92it is <code>void</code>: 93</p> 94<div class="smallexample"> 95<pre class="smallexample">(gdb) print $_exitcode 96$1 = void 97(gdb) print $_isvoid ($_exitcode) 98$2 = 1 99(gdb) run 100Starting program: ./a.out 101[Inferior 1 (process 29572) exited normally] 102(gdb) print $_exitcode 103$3 = 0 104(gdb) print $_isvoid ($_exitcode) 105$4 = 0 106</pre></div> 107 108<p>In the example above, we used <code>$_isvoid</code> to check whether 109<code>$_exitcode</code> is <code>void</code> before and after the execution of the 110program being debugged. Before the execution there is no exit code to 111be examined, therefore <code>$_exitcode</code> is <code>void</code>. After the 112execution the program being debugged returned zero, therefore 113<code>$_exitcode</code> is zero, which means that it is not <code>void</code> 114anymore. 115</p> 116<p>The <code>void</code> expression can also be a call of a function from the 117program being debugged. For example, given the following function: 118</p> 119<div class="smallexample"> 120<pre class="smallexample">void 121foo (void) 122{ 123} 124</pre></div> 125 126<p>The result of calling it inside <small>GDB</small> is <code>void</code>: 127</p> 128<div class="smallexample"> 129<pre class="smallexample">(gdb) print foo () 130$1 = void 131(gdb) print $_isvoid (foo ()) 132$2 = 1 133(gdb) set $v = foo () 134(gdb) print $v 135$3 = void 136(gdb) print $_isvoid ($v) 137$4 = 1 138</pre></div> 139 140</dd> 141<dt><code>$_gdb_setting_str (<var>setting</var>)</code></dt> 142<dd><a name="index-_0024_005fgdb_005fsetting_005fstr_002c-convenience-function"></a> 143<p>Return the value of the <small>GDB</small> <var>setting</var> as a string. 144<var>setting</var> is any setting that can be used in a <code>set</code> or 145<code>show</code> command (see <a href="Controlling-GDB.html#Controlling-GDB">Controlling GDB</a>). 146</p> 147<div class="smallexample"> 148<pre class="smallexample">(gdb) show print frame-arguments 149Printing of non-scalar frame arguments is "scalars". 150(gdb) p $_gdb_setting_str("print frame-arguments") 151$1 = "scalars" 152(gdb) p $_gdb_setting_str("height") 153$2 = "30" 154(gdb) 155</pre></div> 156 157</dd> 158<dt><code>$_gdb_setting (<var>setting</var>)</code></dt> 159<dd><a name="index-_0024_005fgdb_005fsetting_002c-convenience-function"></a> 160<p>Return the value of the <small>GDB</small> <var>setting</var>. 161The type of the returned value depends on the setting. 162</p> 163<p>The value type for boolean and auto boolean settings is <code>int</code>. 164The boolean values <code>off</code> and <code>on</code> are converted to 165the integer values <code>0</code> and <code>1</code>. The value <code>auto</code> is 166converted to the value <code>-1</code>. 167</p> 168<p>The value type for integer settings is either <code>unsigned int</code> 169or <code>int</code>, depending on the setting. 170</p> 171<p>Some integer settings accept an <code>unlimited</code> value. 172Depending on the setting, the <code>set</code> command also accepts 173the value <code>0</code> or the value <code>-1</code> as a synonym for 174<code>unlimited</code>. 175For example, <code>set height unlimited</code> is equivalent to 176<code>set height 0</code>. 177</p> 178<p>Some other settings that accept the <code>unlimited</code> value 179use the value <code>0</code> to literally mean zero. 180For example, <code>set history size 0</code> indicates to not 181record any <small>GDB</small> commands in the command history. 182For such settings, <code>-1</code> is the synonym 183for <code>unlimited</code>. 184</p> 185<p>See the documentation of the corresponding <code>set</code> command for 186the numerical value equivalent to <code>unlimited</code>. 187</p> 188<p>The <code>$_gdb_setting</code> function converts the unlimited value 189to a <code>0</code> or a <code>-1</code> value according to what the 190<code>set</code> command uses. 191</p> 192<div class="smallexample"> 193<pre class="smallexample">(gdb) p $_gdb_setting_str("height") 194$1 = "30" 195(gdb) p $_gdb_setting("height") 196$2 = 30 197(gdb) set height unlimited 198(gdb) p $_gdb_setting_str("height") 199$3 = "unlimited" 200(gdb) p $_gdb_setting("height") 201$4 = 0 202</pre><pre class="smallexample">(gdb) p $_gdb_setting_str("history size") 203$5 = "unlimited" 204(gdb) p $_gdb_setting("history size") 205$6 = -1 206(gdb) p $_gdb_setting_str("disassemble-next-line") 207$7 = "auto" 208(gdb) p $_gdb_setting("disassemble-next-line") 209$8 = -1 210(gdb) 211</pre></div> 212 213<p>Other setting types (enum, filename, optional filename, string, string noescape) 214are returned as string values. 215</p> 216 217</dd> 218<dt><code>$_gdb_maint_setting_str (<var>setting</var>)</code></dt> 219<dd><a name="index-_0024_005fgdb_005fmaint_005fsetting_005fstr_002c-convenience-function"></a> 220<p>Like the <code>$_gdb_setting_str</code> function, but works with 221<code>maintenance set</code> variables. 222</p> 223</dd> 224<dt><code>$_gdb_maint_setting (<var>setting</var>)</code></dt> 225<dd><a name="index-_0024_005fgdb_005fmaint_005fsetting_002c-convenience-function"></a> 226<p>Like the <code>$_gdb_setting</code> function, but works with 227<code>maintenance set</code> variables. 228</p> 229</dd> 230</dl> 231 232<p>The following functions require <small>GDB</small> to be configured with 233<code>Python</code> support. 234</p> 235<dl compact="compact"> 236<dt><code>$_memeq(<var>buf1</var>, <var>buf2</var>, <var>length</var>)</code></dt> 237<dd><a name="index-_0024_005fmemeq_002c-convenience-function"></a> 238<p>Returns one if the <var>length</var> bytes at the addresses given by 239<var>buf1</var> and <var>buf2</var> are equal. 240Otherwise it returns zero. 241</p> 242</dd> 243<dt><code>$_regex(<var>str</var>, <var>regex</var>)</code></dt> 244<dd><a name="index-_0024_005fregex_002c-convenience-function"></a> 245<p>Returns one if the string <var>str</var> matches the regular expression 246<var>regex</var>. Otherwise it returns zero. 247The syntax of the regular expression is that specified by <code>Python</code>’s 248regular expression support. 249</p> 250</dd> 251<dt><code>$_streq(<var>str1</var>, <var>str2</var>)</code></dt> 252<dd><a name="index-_0024_005fstreq_002c-convenience-function"></a> 253<p>Returns one if the strings <var>str1</var> and <var>str2</var> are equal. 254Otherwise it returns zero. 255</p> 256</dd> 257<dt><code>$_strlen(<var>str</var>)</code></dt> 258<dd><a name="index-_0024_005fstrlen_002c-convenience-function"></a> 259<p>Returns the length of string <var>str</var>. 260</p> 261</dd> 262<dt><code>$_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt> 263<dd><a name="index-_0024_005fcaller_005fis_002c-convenience-function"></a> 264<p>Returns one if the calling function’s name is equal to <var>name</var>. 265Otherwise it returns zero. 266</p> 267<p>If the optional argument <var>number_of_frames</var> is provided, 268it is the number of frames up in the stack to look. 269The default is 1. 270</p> 271<p>Example: 272</p> 273<div class="smallexample"> 274<pre class="smallexample">(gdb) backtrace 275#0 bottom_func () 276 at testsuite/gdb.python/py-caller-is.c:21 277#1 0x00000000004005a0 in middle_func () 278 at testsuite/gdb.python/py-caller-is.c:27 279#2 0x00000000004005ab in top_func () 280 at testsuite/gdb.python/py-caller-is.c:33 281#3 0x00000000004005b6 in main () 282 at testsuite/gdb.python/py-caller-is.c:39 283(gdb) print $_caller_is ("middle_func") 284$1 = 1 285(gdb) print $_caller_is ("top_func", 2) 286$1 = 1 287</pre></div> 288 289</dd> 290<dt><code>$_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt> 291<dd><a name="index-_0024_005fcaller_005fmatches_002c-convenience-function"></a> 292<p>Returns one if the calling function’s name matches the regular expression 293<var>regexp</var>. Otherwise it returns zero. 294</p> 295<p>If the optional argument <var>number_of_frames</var> is provided, 296it is the number of frames up in the stack to look. 297The default is 1. 298</p> 299</dd> 300<dt><code>$_any_caller_is(<var>name</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt> 301<dd><a name="index-_0024_005fany_005fcaller_005fis_002c-convenience-function"></a> 302<p>Returns one if any calling function’s name is equal to <var>name</var>. 303Otherwise it returns zero. 304</p> 305<p>If the optional argument <var>number_of_frames</var> is provided, 306it is the number of frames up in the stack to look. 307The default is 1. 308</p> 309<p>This function differs from <code>$_caller_is</code> in that this function 310checks all stack frames from the immediate caller to the frame specified 311by <var>number_of_frames</var>, whereas <code>$_caller_is</code> only checks the 312frame specified by <var>number_of_frames</var>. 313</p> 314</dd> 315<dt><code>$_any_caller_matches(<var>regexp</var><span class="roman">[</span>, <var>number_of_frames</var><span class="roman">]</span>)</code></dt> 316<dd><a name="index-_0024_005fany_005fcaller_005fmatches_002c-convenience-function"></a> 317<p>Returns one if any calling function’s name matches the regular expression 318<var>regexp</var>. Otherwise it returns zero. 319</p> 320<p>If the optional argument <var>number_of_frames</var> is provided, 321it is the number of frames up in the stack to look. 322The default is 1. 323</p> 324<p>This function differs from <code>$_caller_matches</code> in that this function 325checks all stack frames from the immediate caller to the frame specified 326by <var>number_of_frames</var>, whereas <code>$_caller_matches</code> only checks the 327frame specified by <var>number_of_frames</var>. 328</p> 329</dd> 330<dt><code>$_as_string(<var>value</var>)</code></dt> 331<dd><a name="index-_0024_005fas_005fstring_002c-convenience-function"></a> 332<p>Return the string representation of <var>value</var>. 333</p> 334<p>This function is useful to obtain the textual label (enumerator) of an 335enumeration value. For example, assuming the variable <var>node</var> is of 336an enumerated type: 337</p> 338<div class="smallexample"> 339<pre class="smallexample">(gdb) printf "Visiting node of type %s\n", $_as_string(node) 340Visiting node of type NODE_INTEGER 341</pre></div> 342 343</dd> 344<dt><code>$_cimag(<var>value</var>)</code></dt> 345<dt><code>$_creal(<var>value</var>)</code></dt> 346<dd><a name="index-_0024_005fcimag_002c-convenience-function"></a> 347<a name="index-_0024_005fcreal_002c-convenience-function"></a> 348<p>Return the imaginary (<code>$_cimag</code>) or real (<code>$_creal</code>) part of 349the complex number <var>value</var>. 350</p> 351<p>The type of the imaginary or real part depends on the type of the 352complex number, e.g., using <code>$_cimag</code> on a <code>float complex</code> 353will return an imaginary part of type <code>float</code>. 354</p> 355</dd> 356</dl> 357 358<p><small>GDB</small> provides the ability to list and get help on 359convenience functions. 360</p> 361<dl compact="compact"> 362<dt><code>help function</code></dt> 363<dd><a name="index-help-function"></a> 364<a name="index-show-all-convenience-functions"></a> 365<p>Print a list of all convenience functions. 366</p></dd> 367</dl> 368 369<hr> 370<div class="header"> 371<p> 372Next: <a href="Registers.html#Registers" accesskey="n" rel="next">Registers</a>, Previous: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="p" rel="previous">Convenience Vars</a>, Up: <a href="Data.html#Data" accesskey="u" rel="up">Data</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> 373</div> 374 375 376 377</body> 378</html> 379