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diff --git a/share/doc/gdb/Arrays.html b/share/doc/gdb/Arrays.html new file mode 100644 index 0000000..581111f --- /dev/null +++ b/share/doc/gdb/Arrays.html @@ -0,0 +1,151 @@ +<!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: Arrays</title> + +<meta name="description" content="Debugging with GDB: Arrays"> +<meta name="keywords" content="Debugging with GDB: Arrays"> +<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="Output-Formats.html#Output-Formats" rel="next" title="Output Formats"> +<link href="Variables.html#Variables" rel="previous" title="Variables"> +<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="Arrays"></a> +<div class="header"> +<p> +Next: <a href="Output-Formats.html#Output-Formats" accesskey="n" rel="next">Output Formats</a>, Previous: <a href="Variables.html#Variables" accesskey="p" rel="previous">Variables</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="Artificial-Arrays"></a> +<h3 class="section">10.4 Artificial Arrays</h3> + +<a name="index-artificial-array"></a> +<a name="index-arrays"></a> +<a name="index-_0040_002c-referencing-memory-as-an-array"></a> +<p>It is often useful to print out several successive objects of the +same type in memory; a section of an array, or an array of +dynamically determined size for which only a pointer exists in the +program. +</p> +<p>You can do this by referring to a contiguous span of memory as an +<em>artificial array</em>, using the binary operator ‘<samp>@</samp>’. The left +operand of ‘<samp>@</samp>’ should be the first element of the desired array +and be an individual object. The right operand should be the desired length +of the array. The result is an array value whose elements are all of +the type of the left argument. The first element is actually the left +argument; the second element comes from bytes of memory immediately +following those that hold the first element, and so on. Here is an +example. If a program says +</p> +<div class="smallexample"> +<pre class="smallexample">int *array = (int *) malloc (len * sizeof (int)); +</pre></div> + +<p>you can print the contents of <code>array</code> with +</p> +<div class="smallexample"> +<pre class="smallexample">p *array@len +</pre></div> + +<p>The left operand of ‘<samp>@</samp>’ must reside in memory. Array values made +with ‘<samp>@</samp>’ in this way behave just like other arrays in terms of +subscripting, and are coerced to pointers when used in expressions. +Artificial arrays most often appear in expressions via the value history +(see <a href="Value-History.html#Value-History">Value History</a>), after printing one out. +</p> +<p>Another way to create an artificial array is to use a cast. +This re-interprets a value as if it were an array. +The value need not be in memory: +</p><div class="smallexample"> +<pre class="smallexample">(gdb) p/x (short[2])0x12345678 +$1 = {0x1234, 0x5678} +</pre></div> + +<p>As a convenience, if you leave the array length out (as in +‘<samp>(<var>type</var>[])<var>value</var></samp>’) <small>GDB</small> calculates the size to fill +the value (as ‘<samp>sizeof(<var>value</var>)/sizeof(<var>type</var>)</samp>’: +</p><div class="smallexample"> +<pre class="smallexample">(gdb) p/x (short[])0x12345678 +$2 = {0x1234, 0x5678} +</pre></div> + +<p>Sometimes the artificial array mechanism is not quite enough; in +moderately complex data structures, the elements of interest may not +actually be adjacent—for example, if you are interested in the values +of pointers in an array. One useful work-around in this situation is +to use a convenience variable (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience +Variables</a>) as a counter in an expression that prints the first +interesting value, and then repeat that expression via <tt class="key">RET</tt>. For +instance, suppose you have an array <code>dtab</code> of pointers to +structures, and you are interested in the values of a field <code>fv</code> +in each structure. Here is an example of what you might type: +</p> +<div class="smallexample"> +<pre class="smallexample">set $i = 0 +p dtab[$i++]->fv +<span class="key">RET</span> +<span class="key">RET</span> +… +</pre></div> + +<hr> +<div class="header"> +<p> +Next: <a href="Output-Formats.html#Output-Formats" accesskey="n" rel="next">Output Formats</a>, Previous: <a href="Variables.html#Variables" accesskey="p" rel="previous">Variables</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> |