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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 30. Debug Mode</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content=" C++ , library , debug " /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part XII. Extensions" /><link rel="prev" href="ext_compile_checks.html" title="Chapter 29. Compile Time Checks" /><link rel="next" href="bk01pt12ch30s02.html" title="Semantics" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 30. Debug Mode</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><th width="60%" align="center">Part XII.
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Extensions
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</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt12ch30s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 30. Debug Mode"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.debug_mode"></a>Chapter 30. Debug Mode</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="debug_mode.html#manual.ext.debug_mode.intro">Intro</a></span></dt><dt><span class="sect1"><a href="bk01pt12ch30s02.html">Semantics</a></span></dt><dt><span class="sect1"><a href="bk01pt12ch30s03.html">Using</a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt12ch30s03.html#debug_mode.using.mode">Using the Debug Mode</a></span></dt><dt><span class="sect2"><a href="bk01pt12ch30s03.html#debug_mode.using.specific">Using a Specific Debug Container</a></span></dt></dl></dd><dt><span class="sect1"><a href="bk01pt12ch30s04.html">Design</a></span></dt><dd><dl><dt><span class="sect2"><a href="bk01pt12ch30s04.html#debug_mode.design.goals">Goals</a></span></dt><dt><span class="sect2"><a href="bk01pt12ch30s04.html#debug_mode.design.methods">Methods</a></span></dt><dt><span class="sect2"><a href="bk01pt12ch30s04.html#debug_mode.design.other">Other Implementations</a></span></dt></dl></dd></dl></div><div class="sect1" title="Intro"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.intro"></a>Intro</h2></div></div></div><p>
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By default, libstdc++ is built with efficiency in mind, and
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therefore performs little or no error checking that is not
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required by the C++ standard. This means that programs that
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incorrectly use the C++ standard library will exhibit behavior
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that is not portable and may not even be predictable, because they
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tread into implementation-specific or undefined behavior. To
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detect some of these errors before they can become problematic,
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libstdc++ offers a debug mode that provides additional checking of
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library facilities, and will report errors in the use of libstdc++
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as soon as they can be detected by emitting a description of the
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problem to standard error and aborting the program. This debug
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mode is available with GCC 3.4.0 and later versions.
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</p><p>
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The libstdc++ debug mode performs checking for many areas of the
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C++ standard, but the focus is on checking interactions among
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standard iterators, containers, and algorithms, including:
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</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>Safe iterators</em></span>: Iterators keep track of the
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container whose elements they reference, so errors such as
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incrementing a past-the-end iterator or dereferencing an iterator
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that points to a container that has been destructed are diagnosed
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immediately.</p></li><li class="listitem"><p><span class="emphasis"><em>Algorithm preconditions</em></span>: Algorithms attempt to
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validate their input parameters to detect errors as early as
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possible. For instance, the <code class="code">set_intersection</code>
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algorithm requires that its iterator
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parameters <code class="code">first1</code> and <code class="code">last1</code> form a valid
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iterator range, and that the sequence
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[<code class="code">first1</code>, <code class="code">last1</code>) is sorted according to
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the same predicate that was passed
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to <code class="code">set_intersection</code>; the libstdc++ debug mode will
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detect an error if the sequence is not sorted or was sorted by a
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different predicate.</p></li></ul></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_compile_checks.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt12ch30s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 29. Compile Time Checks </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Semantics</td></tr></table></div></body></html>
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