<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <!-- Copyright (C) 1988-2020 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being "Free Software" and "Free Software Needs Free Documentation", with the Front-Cover Texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. (a) The FSF's Back-Cover Text is: "You are free to copy and modify this GNU Manual. 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Any kind of constant, variable or operator defined by the programming language you are using is valid in an expression in <small>GDB</small>. This includes conditional expressions, function calls, casts, and string constants. It also includes preprocessor macros, if you compiled your program to include this information; see <a href="Compilation.html#Compilation">Compilation</a>. </p> <a name="index-arrays-in-expressions"></a> <p><small>GDB</small> supports array constants in expressions input by the user. The syntax is {<var>element</var>, <var>element</var>…}. For example, you can use the command <code>print {1, 2, 3}</code> to create an array of three integers. If you pass an array to a function or assign it to a program variable, <small>GDB</small> copies the array to memory that is <code>malloc</code>ed in the target program. </p> <p>Because C is so widespread, most of the expressions shown in examples in this manual are in C. See <a href="Languages.html#Languages">Using <small>GDB</small> with Different Languages</a>, for information on how to use expressions in other languages. </p> <p>In this section, we discuss operators that you can use in <small>GDB</small> expressions regardless of your programming language. </p> <a name="index-casts_002c-in-expressions"></a> <p>Casts are supported in all languages, not just in C, because it is so useful to cast a number into a pointer in order to examine a structure at that address in memory. </p> <p><small>GDB</small> supports these operators, in addition to those common to programming languages: </p> <dl compact="compact"> <dt><code>@</code></dt> <dd><p>‘<samp>@</samp>’ is a binary operator for treating parts of memory as arrays. See <a href="Arrays.html#Arrays">Artificial Arrays</a>, for more information. </p> </dd> <dt><code>::</code></dt> <dd><p>‘<samp>::</samp>’ allows you to specify a variable in terms of the file or function where it is defined. See <a href="Variables.html#Variables">Program Variables</a>. </p> <a name="index-_007btype_007d"></a> <a name="index-type-casting-memory"></a> <a name="index-memory_002c-viewing-as-typed-object"></a> <a name="index-casts_002c-to-view-memory"></a> </dd> <dt><code>{<var>type</var>} <var>addr</var></code></dt> <dd><p>Refers to an object of type <var>type</var> stored at address <var>addr</var> in memory. The address <var>addr</var> may be any expression whose value is an integer or pointer (but parentheses are required around binary operators, just as in a cast). This construct is allowed regardless of what kind of data is normally supposed to reside at <var>addr</var>. </p></dd> </dl> <hr> <div class="header"> <p> Next: <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> </div> </body> </html>