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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Any kind of constant, variable or operator defined 76by the programming language you are using is valid in an expression in 77<small>GDB</small>. This includes conditional expressions, function calls, 78casts, and string constants. It also includes preprocessor macros, if 79you compiled your program to include this information; see 80<a href="Compilation.html#Compilation">Compilation</a>. 81</p> 82<a name="index-arrays-in-expressions"></a> 83<p><small>GDB</small> supports array constants in expressions input by 84the user. The syntax is {<var>element</var>, <var>element</var>…}. For example, 85you can use the command <code>print {1, 2, 3}</code> to create an array 86of three integers. If you pass an array to a function or assign it 87to a program variable, <small>GDB</small> copies the array to memory that 88is <code>malloc</code>ed in the target program. 89</p> 90<p>Because C is so widespread, most of the expressions shown in examples in 91this manual are in C. See <a href="Languages.html#Languages">Using <small>GDB</small> with Different 92Languages</a>, for information on how to use expressions in other 93languages. 94</p> 95<p>In this section, we discuss operators that you can use in <small>GDB</small> 96expressions regardless of your programming language. 97</p> 98<a name="index-casts_002c-in-expressions"></a> 99<p>Casts are supported in all languages, not just in C, because it is so 100useful to cast a number into a pointer in order to examine a structure 101at that address in memory. 102</p> 103<p><small>GDB</small> supports these operators, in addition to those common 104to programming languages: 105</p> 106<dl compact="compact"> 107<dt><code>@</code></dt> 108<dd><p>‘<samp>@</samp>’ is a binary operator for treating parts of memory as arrays. 109See <a href="Arrays.html#Arrays">Artificial Arrays</a>, for more information. 110</p> 111</dd> 112<dt><code>::</code></dt> 113<dd><p>‘<samp>::</samp>’ allows you to specify a variable in terms of the file or 114function where it is defined. See <a href="Variables.html#Variables">Program Variables</a>. 115</p> 116<a name="index-_007btype_007d"></a> 117<a name="index-type-casting-memory"></a> 118<a name="index-memory_002c-viewing-as-typed-object"></a> 119<a name="index-casts_002c-to-view-memory"></a> 120</dd> 121<dt><code>{<var>type</var>} <var>addr</var></code></dt> 122<dd><p>Refers to an object of type <var>type</var> stored at address <var>addr</var> in 123memory. The address <var>addr</var> may be any expression whose value is 124an integer or pointer (but parentheses are required around binary 125operators, just as in a cast). This construct is allowed regardless 126of what kind of data is normally supposed to reside at <var>addr</var>. 127</p></dd> 128</dl> 129 130<hr> 131<div class="header"> 132<p> 133Next: <a href="Ambiguous-Expressions.html#Ambiguous-Expressions" accesskey="n" rel="next">Ambiguous Expressions</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> 134</div> 135 136 137 138</body> 139</html> 140