diff options
Diffstat (limited to 'share/doc/gdb/Expressions.html')
| -rw-r--r-- | share/doc/gdb/Expressions.html | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/share/doc/gdb/Expressions.html b/share/doc/gdb/Expressions.html new file mode 100644 index 0000000..0069d35 --- /dev/null +++ b/share/doc/gdb/Expressions.html @@ -0,0 +1,139 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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. Buying copies from GNU Press supports the FSF in +developing GNU and promoting software freedom." --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Expressions</title> + +<meta name="description" content="Debugging with GDB: Expressions"> +<meta name="keywords" content="Debugging with GDB: Expressions"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Data.html#Data" rel="up" title="Data"> +<link href="Ambiguous-Expressions.html#Ambiguous-Expressions" rel="next" title="Ambiguous Expressions"> +<link href="Data.html#Data" rel="previous" title="Data"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Expressions"></a> +<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> +<hr> +<a name="Expressions-1"></a> +<h3 class="section">10.1 Expressions</h3> + +<a name="index-expressions"></a> +<p><code>print</code> and many other <small>GDB</small> commands accept an expression and +compute its value. 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> |