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diff --git a/share/doc/gdb/Value-History.html b/share/doc/gdb/Value-History.html new file mode 100644 index 0000000..719014f --- /dev/null +++ b/share/doc/gdb/Value-History.html @@ -0,0 +1,159 @@ +<!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: Value History</title> + +<meta name="description" content="Debugging with GDB: Value History"> +<meta name="keywords" content="Debugging with GDB: Value History"> +<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="Convenience-Vars.html#Convenience-Vars" rel="next" title="Convenience Vars"> +<link href="Pretty_002dPrinter-Commands.html#Pretty_002dPrinter-Commands" rel="previous" title="Pretty-Printer Commands"> +<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="Value-History"></a> +<div class="header"> +<p> +Next: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="n" rel="next">Convenience Vars</a>, Previous: <a href="Pretty-Printing.html#Pretty-Printing" accesskey="p" rel="previous">Pretty Printing</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="Value-History-1"></a> +<h3 class="section">10.11 Value History</h3> + +<a name="index-value-history"></a> +<a name="index-history-of-values-printed-by-GDB"></a> +<p>Values printed by the <code>print</code> command are saved in the <small>GDB</small> +<em>value history</em>. This allows you to refer to them in other expressions. +Values are kept until the symbol table is re-read or discarded +(for example with the <code>file</code> or <code>symbol-file</code> commands). +When the symbol table changes, the value history is discarded, +since the values may contain pointers back to the types defined in the +symbol table. +</p> +<a name="index-_0024"></a> +<a name="index-_0024_0024"></a> +<a name="index-history-number"></a> +<p>The values printed are given <em>history numbers</em> by which you can +refer to them. These are successive integers starting with one. +<code>print</code> shows you the history number assigned to a value by +printing ‘<samp>$<var>num</var> = </samp>’ before the value; here <var>num</var> is the +history number. +</p> +<p>To refer to any previous value, use ‘<samp>$</samp>’ followed by the value’s +history number. The way <code>print</code> labels its output is designed to +remind you of this. Just <code>$</code> refers to the most recent value in +the history, and <code>$$</code> refers to the value before that. +<code>$$<var>n</var></code> refers to the <var>n</var>th value from the end; <code>$$2</code> +is the value just prior to <code>$$</code>, <code>$$1</code> is equivalent to +<code>$$</code>, and <code>$$0</code> is equivalent to <code>$</code>. +</p> +<p>For example, suppose you have just printed a pointer to a structure and +want to see the contents of the structure. It suffices to type +</p> +<div class="smallexample"> +<pre class="smallexample">p *$ +</pre></div> + +<p>If you have a chain of structures where the component <code>next</code> points +to the next one, you can print the contents of the next one with this: +</p> +<div class="smallexample"> +<pre class="smallexample">p *$.next +</pre></div> + +<p>You can print successive links in the chain by repeating this +command—which you can do by just typing <tt class="key">RET</tt>. +</p> +<p>Note that the history records values, not expressions. If the value of +<code>x</code> is 4 and you type these commands: +</p> +<div class="smallexample"> +<pre class="smallexample">print x +set x=5 +</pre></div> + +<p>then the value recorded in the value history by the <code>print</code> command +remains 4 even though the value of <code>x</code> has changed. +</p> +<dl compact="compact"> +<dd><a name="index-show-values"></a> +</dd> +<dt><code>show values</code></dt> +<dd><p>Print the last ten values in the value history, with their item numbers. +This is like ‘<samp>p $$9</samp>’ repeated ten times, except that <code>show +values</code> does not change the history. +</p> +</dd> +<dt><code>show values <var>n</var></code></dt> +<dd><p>Print ten history values centered on history item number <var>n</var>. +</p> +</dd> +<dt><code>show values +</code></dt> +<dd><p>Print ten history values just after the values last printed. If no more +values are available, <code>show values +</code> produces no display. +</p></dd> +</dl> + +<p>Pressing <tt class="key">RET</tt> to repeat <code>show values <var>n</var></code> has exactly the +same effect as ‘<samp>show values +</samp>’. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Convenience-Vars.html#Convenience-Vars" accesskey="n" rel="next">Convenience Vars</a>, Previous: <a href="Pretty-Printing.html#Pretty-Printing" accesskey="p" rel="previous">Pretty Printing</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> |