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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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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>Frequently Asked Questions</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="bk03.html" title="" /><link rel="prev" href="bk03.html" title="" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Frequently Asked Questions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk03.html">Prev</a> </td><th width="60%" align="center"></th><td width="20%" align="right"> </td></tr></table><hr /></div><div class="article" title="Frequently Asked Questions"><div class="titlepage"><div><div><h2 class="title"><a id="faq"></a>Frequently Asked Questions</h2></div><div><p class="copyright">Copyright ©
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      2008
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      <a class="ulink" href="http://www.fsf.org" target="_top">FSF</a>
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    </p></div></div><hr /></div><div class="qandaset" title="Frequently Asked Questions"><a id="id571249"></a><dl><dt>1.  <a href="faq.html#faq.info">General Information</a></dt><dd><dl><dt>1.1. <a href="faq.html#faq.what">
8 
      What is libstdc++?
9 
    </a></dt><dt>1.2. <a href="faq.html#faq.why">
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      Why should I use libstdc++?
11 
    </a></dt><dt>1.3. <a href="faq.html#faq.who">
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      Who's in charge of it?
13 
    </a></dt><dt>1.4. <a href="faq.html#faq.when">
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      When is libstdc++ going to be finished?
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    </a></dt><dt>1.5. <a href="faq.html#faq.how">
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      How do I contribute to the effort?
17 
    </a></dt><dt>1.6. <a href="faq.html#faq.whereis_old">
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      What happened to the older libg++? I need that!
19 
    </a></dt><dt>1.7. <a href="faq.html#faq.more_questions">
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      What if I have more questions?
21 
    </a></dt></dl></dd><dt>2.  <a href="faq.html#faq.license">License</a></dt><dd><dl><dt>2.1. <a href="faq.html#faq.license.what">
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      What are the license terms for libstdc++?
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    </a></dt><dt>2.2. <a href="faq.html#faq.license.any_program">
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      So any program which uses libstdc++ falls under the GPL?
25 
    </a></dt><dt>2.3. <a href="faq.html#faq.license.lgpl">
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      How is that different from the GNU {Lesser,Library} GPL?
27 
    </a></dt><dt>2.4. <a href="faq.html#faq.license.what_restrictions">
28 
      I see. So, what restrictions are there on programs that use the library?
29 
    </a></dt></dl></dd><dt>3.  <a href="faq.html#faq.installation">Installation</a></dt><dd><dl><dt>3.1. <a href="faq.html#faq.how_to_install">How do I install libstdc++?
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    </a></dt><dt>3.2. <a href="faq.html#faq.how_to_get_sources">How does one get current libstdc++ sources?
31 
    </a></dt><dt>3.3. <a href="faq.html#faq.how_to_test">How do I know if it works?
32 
    </a></dt><dt>3.4. <a href="faq.html#faq.how_to_set_paths">How do I insure that the dynamically linked library will be found?
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    </a></dt><dt>3.5. <a href="faq.html#faq.what_is_libsupcxx">
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      What's libsupc++?
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    </a></dt><dt>3.6. <a href="faq.html#faq.size">
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      This library is HUGE!
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    </a></dt></dl></dd><dt>4.  <a href="faq.html#faq.platform-specific">Platform-Specific Issues</a></dt><dd><dl><dt>4.1. <a href="faq.html#faq.other_compilers">
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      Can libstdc++ be used with non-GNU compilers?
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    </a></dt><dt>4.2. <a href="faq.html#faq.solaris_long_long">
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      No 'long long' type on Solaris?
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    </a></dt><dt>4.3. <a href="faq.html#faq.predefined">
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      _XOPEN_SOURCE and _GNU_SOURCE are always defined?
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    </a></dt><dt>4.4. <a href="faq.html#faq.darwin_ctype">
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      Mac OS X ctype.h is broken! How can I fix it?
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    </a></dt><dt>4.5. <a href="faq.html#faq.threads_i386">
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      Threading is broken on i386?
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    </a></dt><dt>4.6. <a href="faq.html#faq.atomic_mips">
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      MIPS atomic operations
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    </a></dt><dt>4.7. <a href="faq.html#faq.linux_glibc">
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      Recent GNU/Linux glibc required?
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    </a></dt><dt>4.8. <a href="faq.html#faq.freebsd_wchar">
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      Can't use wchar_t/wstring on FreeBSD
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    </a></dt></dl></dd><dt>5.  <a href="faq.html#faq.known_bugs">Known Bugs</a></dt><dd><dl><dt>5.1. <a href="faq.html#faq.what_works">
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      What works already?
55 
    </a></dt><dt>5.2. <a href="faq.html#faq.standard_bugs">
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      Bugs in the ISO C++ language or library specification
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    </a></dt><dt>5.3. <a href="faq.html#faq.compiler_bugs">
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      Bugs in the compiler (gcc/g++) and not libstdc++
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    </a></dt></dl></dd><dt>6.  <a href="faq.html#faq.known_non-bugs">Known Non-Bugs</a></dt><dd><dl><dt>6.1. <a href="faq.html#faq.stream_reopening_fails">
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      Reopening a stream fails
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    </a></dt><dt>6.2. <a href="faq.html#faq.wefcxx_verbose">
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      -Weffc++ complains too much
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    </a></dt><dt>6.3. <a href="faq.html#faq.ambiguous_overloads">
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      Ambiguous overloads after including an old-style header
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    </a></dt><dt>6.4. <a href="faq.html#faq.v2_headers">
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      The g++-3 headers are not ours
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    </a></dt><dt>6.5. <a href="faq.html#faq.boost_concept_checks">
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      Errors about *Concept and
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      constraints in the STL
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    </a></dt><dt>6.6. <a href="faq.html#faq.dlopen_crash">
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      Program crashes when using library code in a
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      dynamically-loaded library
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    </a></dt><dt>6.7. <a href="faq.html#faq.memory_leaks">
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      “Memory leaks” in containers
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    </a></dt><dt>6.8. <a href="faq.html#faq.list_size_on">
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      list::size() is O(n)!
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    </a></dt><dt>6.9. <a href="faq.html#faq.easy_to_fix">
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      Aw, that's easy to fix!
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    </a></dt></dl></dd><dt>7.  <a href="faq.html#faq.misc">Miscellaneous</a></dt><dd><dl><dt>7.1. <a href="faq.html#faq.iterator_as_pod">
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      string::iterator is not char*; vector&lt;T&gt;::iterator is not T*
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    </a></dt><dt>7.2. <a href="faq.html#faq.what_is_next">
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      What's next after libstdc++?
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    </a></dt><dt>7.3. <a href="faq.html#faq.sgi_stl">
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      What about the STL from SGI?
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    </a></dt><dt>7.4. <a href="faq.html#faq.extensions_and_backwards_compat">
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      Extensions and Backward Compatibility
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    </a></dt><dt>7.5. <a href="faq.html#faq.tr1_support">
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      Does libstdc++ support TR1?
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    </a></dt><dt>7.6. <a href="faq.html#faq.get_iso_cxx">How do I get a copy of the ISO C++ Standard?
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    </a></dt><dt>7.7. <a href="faq.html#faq.what_is_abi">
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      What's an ABI and why is it so messy?
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    </a></dt><dt>7.8. <a href="faq.html#faq.size_equals_capacity">
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      How do I make std::vector&lt;T&gt;::capacity() == std::vector&lt;T&gt;::size?
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    </a></dt></dl></dd></dl><table border="0" width="100%" summary="Q and A Set"><col align="left" width="1%" /><col /><tbody><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.info"></a>1. General Information</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>1.1. <a href="faq.html#faq.what">
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      What is libstdc++?
96 
    </a></dt><dt>1.2. <a href="faq.html#faq.why">
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      Why should I use libstdc++?
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    </a></dt><dt>1.3. <a href="faq.html#faq.who">
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      Who's in charge of it?
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    </a></dt><dt>1.4. <a href="faq.html#faq.when">
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      When is libstdc++ going to be finished?
102 
    </a></dt><dt>1.5. <a href="faq.html#faq.how">
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      How do I contribute to the effort?
104 
    </a></dt><dt>1.6. <a href="faq.html#faq.whereis_old">
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      What happened to the older libg++? I need that!
106 
    </a></dt><dt>1.7. <a href="faq.html#faq.more_questions">
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      What if I have more questions?
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    </a></dt></dl></td></tr><tr class="question" title="1.1."><td align="left" valign="top"><a id="faq.what"></a><a id="faq.what.q"></a><p><b>1.1.</b></p></td><td align="left" valign="top"><p>
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      What is libstdc++?
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    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="faq.what.a"></a></td><td align="left" valign="top"><p>
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     The GNU Standard C++ Library v3 is an ongoing project to
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     implement the ISO 14882 Standard C++ library as described in
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     chapters 17 through 27 and annex D.  For those who want to see
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     exactly how far the project has come, or just want the latest
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     bleeding-edge code, the up-to-date source is available over
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     anonymous SVN, and can even be browsed over
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     the <a class="ulink" href="http://gcc.gnu.org/svn.html" target="_top">web</a>.
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    </p></td></tr><tr class="question" title="1.2."><td align="left" valign="top"><a id="faq.why"></a><a id="q-why"></a><p><b>1.2.</b></p></td><td align="left" valign="top"><p>
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      Why should I use libstdc++?
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    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-why"></a></td><td align="left" valign="top"><p>
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    The completion of the ISO C++ standardization gave the C++
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    community a powerful set of reuseable tools in the form of the C++
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    Standard Library.  However, all existing C++ implementations are
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    (as the Draft Standard used to say) <span class="quote">“<span class="quote">incomplet and
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    incorrekt</span>”</span>, and many suffer from limitations of the compilers
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    that use them.
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    </p><p>
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    The GNU compiler collection
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    (<span class="command"><strong>gcc</strong></span>, <span class="command"><strong>g++</strong></span>, etc) is widely
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    considered to be one of the leading compilers in the world.  Its
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    development is overseen by the
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    <a class="ulink" href="http://gcc.gnu.org/" target="_top">GCC team</a>.  All of
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    the rapid development and near-legendary
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    <a class="ulink" href="http://gcc.gnu.org/buildstat.html" target="_top">portability</a>
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    that are the hallmarks of an open-source project are being
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    applied to libstdc++.
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    </p><p>
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    That means that all of the Standard classes and functions will be
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    freely available and fully compliant. (Such as
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    <code class="classname">string</code>,
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    <code class="classname">vector&lt;&gt;</code>, iostreams, and algorithms.)
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    Programmers will no longer need to <span class="quote">“<span class="quote">roll their own</span>”</span>
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    nor be worried about platform-specific incompatibilities.
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    </p></td></tr><tr class="question" title="1.3."><td align="left" valign="top"><a id="faq.who"></a><a id="q-who"></a><p><b>1.3.</b></p></td><td align="left" valign="top"><p>
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      Who's in charge of it?
146 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-who"></a></td><td align="left" valign="top"><p>
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     The libstdc++ project is contributed to by several developers
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     all over the world, in the same way as GCC or Linux.
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     Benjamin Kosnik, Gabriel Dos Reis, Phil Edwards, Ulrich Drepper,
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     Loren James Rittle, and Paolo Carlini are the lead maintainers of
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     the SVN archive.
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    </p><p>
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    Development and discussion is held on the libstdc++ mailing
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    list.  Subscribing to the list, or searching the list
155 
    archives, is open to everyone.  You can read instructions for
156 
    doing so on the <a class="ulink" href="http://gcc.gnu.org/libstdc++/" target="_top">homepage</a>.
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    If you have questions, ideas, code, or are just curious, sign up!
158 
    </p></td></tr><tr class="question" title="1.4."><td align="left" valign="top"><a id="faq.when"></a><a id="q-when"></a><p><b>1.4.</b></p></td><td align="left" valign="top"><p>
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      When is libstdc++ going to be finished?
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    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-when"></a></td><td align="left" valign="top"><p>
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    Nathan Myers gave the best of all possible answers, responding to
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    a Usenet article asking this question: <span class="emphasis"><em>Sooner, if you
163 
    help.</em></span>
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    </p></td></tr><tr class="question" title="1.5."><td align="left" valign="top"><a id="faq.how"></a><a id="q-how"></a><p><b>1.5.</b></p></td><td align="left" valign="top"><p>
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      How do I contribute to the effort?
166 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-how"></a></td><td align="left" valign="top"><p>
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    Here is <a class="link" href="manual/appendix_contributing.html" title="Appendix A.  Contributing">a page devoted to
168 
    this topic</a>. Subscribing to the mailing list (see above, or
169 
    the homepage) is a very good idea if you have something to
170 
    contribute, or if you have spare time and want to
171 
    help. Contributions don't have to be in the form of source code;
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    anybody who is willing to help write documentation, for example,
173 
    or has found a bug in code that we all thought was working and is
174 
    willing to provide details, is more than welcome!
175 
    </p></td></tr><tr class="question" title="1.6."><td align="left" valign="top"><a id="faq.whereis_old"></a><a id="q-whereis_old"></a><p><b>1.6.</b></p></td><td align="left" valign="top"><p>
176 
      What happened to the older libg++? I need that!
177 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-whereis_old"></a></td><td align="left" valign="top"><p>
178 
    The most recent libg++ README states that libg++ is no longer
179 
    being actively maintained.  It should not be used for new
180 
    projects, and is only being kicked along to support older code.
181 
    </p><p>
182 
    More information in the <a class="link" href="manual/backwards.html" title="Backwards Compatibility">backwards compatibility documentation</a>
183 
    </p></td></tr><tr class="question" title="1.7."><td align="left" valign="top"><a id="faq.more_questions"></a><a id="q-more_questions"></a><p><b>1.7.</b></p></td><td align="left" valign="top"><p>
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      What if I have more questions?
185 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-more_questions"></a></td><td align="left" valign="top"><p>
186 
    If you have read the README file, and your question remains
187 
    unanswered, then just ask the mailing list. At present, you do not
188 
    need to be subscribed to the list to send a message to it.  More
189 
    information is available on the homepage (including how to browse
190 
    the list archives); to send a message to the list,
191 
    use <code class="email">&lt;<a class="email" href="mailto:libstdc++@gcc.gnu.org">libstdc++@gcc.gnu.org</a>&gt;</code>.
192 
    </p><p>
193 
    If you have a question that you think should be included
194 
    here, or if you have a question <span class="emphasis"><em>about</em></span> a question/answer
195 
    here, please send email to the libstdc++ mailing list, as above.
196 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.license"></a>2. License</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>2.1. <a href="faq.html#faq.license.what">
197 
      What are the license terms for libstdc++?
198 
    </a></dt><dt>2.2. <a href="faq.html#faq.license.any_program">
199 
      So any program which uses libstdc++ falls under the GPL?
200 
    </a></dt><dt>2.3. <a href="faq.html#faq.license.lgpl">
201 
      How is that different from the GNU {Lesser,Library} GPL?
202 
    </a></dt><dt>2.4. <a href="faq.html#faq.license.what_restrictions">
203 
      I see. So, what restrictions are there on programs that use the library?
204 
    </a></dt></dl></td></tr><tr class="question" title="2.1."><td align="left" valign="top"><a id="faq.license.what"></a><a id="q-license.what"></a><p><b>2.1.</b></p></td><td align="left" valign="top"><p>
205 
      What are the license terms for libstdc++?
206 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-license.what"></a></td><td align="left" valign="top"><p>
207 
    See <a class="link" href="manual/license.html" title="License">our license description</a>
208 
    for these and related questions.
209 
    </p></td></tr><tr class="question" title="2.2."><td align="left" valign="top"><a id="faq.license.any_program"></a><a id="q-license.any_program"></a><p><b>2.2.</b></p></td><td align="left" valign="top"><p>
210 
      So any program which uses libstdc++ falls under the GPL?
211 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-license.any_program"></a></td><td align="left" valign="top"><p>
212 
     No. The special exception permits use of the library in
213 
     proprietary applications.
214 
    </p></td></tr><tr class="question" title="2.3."><td align="left" valign="top"><a id="faq.license.lgpl"></a><a id="q-license.lgpl"></a><p><b>2.3.</b></p></td><td align="left" valign="top"><p>
215 
      How is that different from the GNU {Lesser,Library} GPL?
216 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-license.lgpl"></a></td><td align="left" valign="top"><p>
217 
      The LGPL requires that users be able to replace the LGPL code with a
218 
     modified version; this is trivial if the library in question is a C
219 
     shared library.  But there's no way to make that work with C++, where
220 
     much of the library consists of inline functions and templates, which
221 
     are expanded inside the code that uses the library.  So to allow people
222 
     to replace the library code, someone using the library would have to
223 
     distribute their own source, rendering the LGPL equivalent to the GPL.
224 
    </p></td></tr><tr class="question" title="2.4."><td align="left" valign="top"><a id="faq.license.what_restrictions"></a><a id="q-license.what_restrictions"></a><p><b>2.4.</b></p></td><td align="left" valign="top"><p>
225 
      I see. So, what restrictions are there on programs that use the library?
226 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-license.what_restrictions"></a></td><td align="left" valign="top"><p>
227 
      None.  We encourage such programs to be released as open source,
228 
     but we won't punish you or sue you if you choose otherwise.
229 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.installation"></a>3. Installation</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>3.1. <a href="faq.html#faq.how_to_install">How do I install libstdc++?
230 
    </a></dt><dt>3.2. <a href="faq.html#faq.how_to_get_sources">How does one get current libstdc++ sources?
231 
    </a></dt><dt>3.3. <a href="faq.html#faq.how_to_test">How do I know if it works?
232 
    </a></dt><dt>3.4. <a href="faq.html#faq.how_to_set_paths">How do I insure that the dynamically linked library will be found?
233 
    </a></dt><dt>3.5. <a href="faq.html#faq.what_is_libsupcxx">
234 
      What's libsupc++?
235 
    </a></dt><dt>3.6. <a href="faq.html#faq.size">
236 
      This library is HUGE!
237 
    </a></dt></dl></td></tr><tr class="question" title="3.1."><td align="left" valign="top"><a id="faq.how_to_install"></a><a id="q-how_to_install"></a><p><b>3.1.</b></p></td><td align="left" valign="top"><p>How do I install libstdc++?
238 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-how_to_install"></a></td><td align="left" valign="top"><p>
239 
    Often libstdc++ comes pre-installed as an integral part of many
240 
    existing Linux and Unix systems, as well as many embedded
241 
    development tools. It may be necessary to install extra
242 
    development packages to get the headers, or the documentation, or
243 
    the source: please consult your vendor for details.
244 
    </p><p>
245 
    To build and install from the GNU GCC sources, please consult the
246 
    <a class="link" href="manual/setup.html" title="Chapter 2. Setup">setup
247 
    documentation</a> for detailed
248 
    instructions. You may wish to browse those files ahead
249 
    of time to get a feel for what's required.
250 
    </p></td></tr><tr class="question" title="3.2."><td align="left" valign="top"><a id="faq.how_to_get_sources"></a><a id="q-how_to_get_sources"></a><p><b>3.2.</b></p></td><td align="left" valign="top"><p>How does one get current libstdc++ sources?
251 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-how_to_get_sources"></a></td><td align="left" valign="top"><p>
252 
    Libstdc++ sources for all official releases can be obtained as
253 
    part of the GCC sources, available from various sites and
254 
    mirrors. A full <a class="ulink" href="http://gcc.gnu.org/mirrors.html" target="_top">list of
255 
    download sites</a> is provided on the main GCC site.
256 
    </p><p>
257 
    Current libstdc++ sources can always be checked out of the main
258 
    GCC source repository using the appropriate version control
259 
    tool. At this time, that tool
260 
    is <span class="application">Subversion</span>.
261 
    </p><p>
262 
    <span class="application">Subversion</span>, or <acronym class="acronym">SVN</acronym>, is
263 
    one of several revision control packages.  It was selected for GNU
264 
    projects because it's free (speech), free (beer), and very high
265 
    quality.  The <a class="ulink" href="http://subversion.tigris.org" target="_top"> Subversion
266 
    home page</a> has a better description.
267 
    </p><p>
268 
    The <span class="quote">“<span class="quote">anonymous client checkout</span>”</span> feature of SVN is
269 
    similar to anonymous FTP in that it allows anyone to retrieve
270 
    the latest libstdc++ sources.
271 
    </p><p>
272 
    For more information
273 
    see <a class="ulink" href="http://gcc.gnu.org/svn.html" target="_top"><acronym class="acronym">SVN</acronym>
274 
    details</a>.
275 
    </p></td></tr><tr class="question" title="3.3."><td align="left" valign="top"><a id="faq.how_to_test"></a><a id="q-how_to_test"></a><p><b>3.3.</b></p></td><td align="left" valign="top"><p>How do I know if it works?
276 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-how_to_test"></a></td><td align="left" valign="top"><p>
277 
    Libstdc++ comes with its own validation testsuite, which includes
278 
    conformance testing, regression testing, ABI testing, and
279 
    performance testing. Please consult the
280 
    <a class="ulink" href="http://gcc.gnu.org/install/test.html" target="_top">testing
281 
    documentation</a> for more details.
282 
    </p><p>
283 
    If you find bugs in the testsuite programs themselves, or if you
284 
    think of a new test program that should be added to the suite,
285 
    <span class="emphasis"><em>please</em></span> write up your idea and send it to the list!
286 
    </p></td></tr><tr class="question" title="3.4."><td align="left" valign="top"><a id="faq.how_to_set_paths"></a><a id="q-how_to_set_paths"></a><p><b>3.4.</b></p></td><td align="left" valign="top"><p>How do I insure that the dynamically linked library will be found?
287 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-how_to_set_paths"></a></td><td align="left" valign="top"><p>
288 
    Depending on your platform and library version, the error message might
289 
    be similar to one of the following:
290 
    </p><pre class="screen">
291 
    ./a.out: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory
292 
 
293 
    /usr/libexec/ld-elf.so.1: Shared object "libstdc++.so.6" not found
294 
    </pre><p>
295 
    This doesn't mean that the shared library isn't installed, only
296 
    that the dynamic linker can't find it. When a dynamically-linked
297 
    executable is run the linker finds and loads the required shared
298 
    libraries by searching a pre-configured list of directories. If
299 
    the directory where you've installed libstdc++ is not in this list
300 
    then the libraries won't be found. The simplest way to fix this is
301 
    to use the <code class="literal">LD_LIBRARY_PATH</code> environment variable,
302 
    which is a colon-separated list of directories in which the linker
303 
    will search for shared libraries:
304 
    </p><pre class="screen">
305 
    LD_LIBRARY_PATH=${prefix}/lib:$LD_LIBRARY_PATH
306 
    export LD_LIBRARY_PATH
307 
    </pre><p>
308 
    The exact environment variable to use will depend on your
309 
    platform, e.g. DYLD_LIBRARY_PATH for Darwin,
310 
    LD_LIBRARY_PATH_32/LD_LIBRARY_PATH_64 for Solaris 32-/64-bit,
311 
    LD_LIBRARYN32_PATH/LD_LIBRARY64_PATH for Irix N32/64-bit ABIs and
312 
    SHLIB_PATH for HP-UX.
313 
    </p><p>
314 
    See the man pages for <span class="command"><strong>ld</strong></span>, <span class="command"><strong>ldd</strong></span>
315 
    and <span class="command"><strong>ldconfig</strong></span> for more information. The dynamic
316 
    linker has different names on different platforms but the man page
317 
    is usually called something such as <code class="filename">ld.so/rtld/dld.so</code>.
318 
    </p></td></tr><tr class="question" title="3.5."><td align="left" valign="top"><a id="faq.what_is_libsupcxx"></a><a id="q-what_is_libsupcxx"></a><p><b>3.5.</b></p></td><td align="left" valign="top"><p>
319 
      What's libsupc++?
320 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-what_is_libsupcxx"></a></td><td align="left" valign="top"><p>
321 
      If the only functions from <code class="filename">libstdc++.a</code>
322 
      which you need are language support functions (those listed in
323 
      <a class="link" href="manual/support.html" title="Part II.  Support">clause 18</a> of the
324 
      standard, e.g., <code class="function">new</code> and
325 
      <code class="function">delete</code>), then try linking against
326 
      <code class="filename">libsupc++.a</code>, which is a subset of
327 
      <code class="filename">libstdc++.a</code>.  (Using <span class="command"><strong>gcc</strong></span>
328 
      instead of <span class="command"><strong>g++</strong></span> and explicitly linking in
329 
      <code class="filename">libsupc++.a</code> via <code class="literal">-lsupc++</code>
330 
      for the final link step will do it).  This library contains only
331 
      those support routines, one per object file.  But if you are
332 
      using anything from the rest of the library, such as IOStreams
333 
      or vectors, then you'll still need pieces from
334 
      <code class="filename">libstdc++.a</code>.
335 
    </p></td></tr><tr class="question" title="3.6."><td align="left" valign="top"><a id="faq.size"></a><a id="q-size"></a><p><b>3.6.</b></p></td><td align="left" valign="top"><p>
336 
      This library is HUGE!
337 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-size"></a></td><td align="left" valign="top"><p>
338 
    Usually the size of libraries on disk isn't noticeable.  When a
339 
    link editor (or simply <span class="quote">“<span class="quote">linker</span>”</span>) pulls things from a
340 
    static archive library, only the necessary object files are copied
341 
    into your executable, not the entire library.  Unfortunately, even
342 
    if you only need a single function or variable from an object file,
343 
    the entire object file is extracted.  (There's nothing unique to C++
344 
    or libstdc++ about this; it's just common behavior, given here
345 
    for background reasons.)
346 
    </p><p>
347 
    Some of the object files which make up libstdc++.a are rather large.
348 
    If you create a statically-linked executable with
349 
    <code class="literal">-static</code>, those large object files are suddenly part
350 
    of your executable.  Historically the best way around this was to
351 
    only place a very few functions (often only a single one) in each
352 
    source/object file; then extracting a single function is the same
353 
    as extracting a single .o file.  For libstdc++ this is only
354 
    possible to a certain extent; the object files in question contain
355 
    template classes and template functions, pre-instantiated, and
356 
    splitting those up causes severe maintenance headaches.
357 
    </p><p>
358 
    On supported platforms, libstdc++ takes advantage of garbage
359 
    collection in the GNU linker to get a result similar to separating
360 
    each symbol into a separate source and object files. On these platforms,
361 
    GNU ld can place each function and variable into its own
362 
    section in a .o file.  The GNU linker can then perform garbage
363 
    collection on unused sections; this reduces the situation to only
364 
    copying needed functions into the executable, as before, but all
365 
    happens automatically.
366 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.platform-specific"></a>4. Platform-Specific Issues</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>4.1. <a href="faq.html#faq.other_compilers">
367 
      Can libstdc++ be used with non-GNU compilers?
368 
    </a></dt><dt>4.2. <a href="faq.html#faq.solaris_long_long">
369 
      No 'long long' type on Solaris?
370 
    </a></dt><dt>4.3. <a href="faq.html#faq.predefined">
371 
      _XOPEN_SOURCE and _GNU_SOURCE are always defined?
372 
    </a></dt><dt>4.4. <a href="faq.html#faq.darwin_ctype">
373 
      Mac OS X ctype.h is broken! How can I fix it?
374 
    </a></dt><dt>4.5. <a href="faq.html#faq.threads_i386">
375 
      Threading is broken on i386?
376 
    </a></dt><dt>4.6. <a href="faq.html#faq.atomic_mips">
377 
      MIPS atomic operations
378 
    </a></dt><dt>4.7. <a href="faq.html#faq.linux_glibc">
379 
      Recent GNU/Linux glibc required?
380 
    </a></dt><dt>4.8. <a href="faq.html#faq.freebsd_wchar">
381 
      Can't use wchar_t/wstring on FreeBSD
382 
    </a></dt></dl></td></tr><tr class="question" title="4.1."><td align="left" valign="top"><a id="faq.other_compilers"></a><a id="q-other_compilers"></a><p><b>4.1.</b></p></td><td align="left" valign="top"><p>
383 
      Can libstdc++ be used with non-GNU compilers?
384 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-other_compilers"></a></td><td align="left" valign="top"><p>
385 
    Perhaps.
386 
    </p><p>
387 
    Since the goal of ISO Standardization is for all C++
388 
    implementations to be able to share code, libstdc++ should be
389 
    usable under any ISO-compliant compiler, at least in theory.
390 
    </p><p>
391 
    However, the reality is that libstdc++ is targeted and optimized
392 
    for GCC/g++. This means that often libstdc++ uses specific,
393 
    non-standard features of g++ that are not present in older
394 
    versions of proprietary compilers. It may take as much as a year or two
395 
    after an official release of GCC that contains these features for
396 
    proprietary tools support these constructs.
397 
    </p><p>
398 
    In the near past, specific released versions of libstdc++ have
399 
    been known to work with versions of the EDG C++ compiler, and
400 
    vendor-specific proprietary C++ compilers such as the Intel ICC
401 
    C++ compiler.
402 
    </p></td></tr><tr class="question" title="4.2."><td align="left" valign="top"><a id="faq.solaris_long_long"></a><a id="q-solaris_long_long"></a><p><b>4.2.</b></p></td><td align="left" valign="top"><p>
403 
      No 'long long' type on Solaris?
404 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-solaris_long_long"></a></td><td align="left" valign="top"><p>
405 
    By default we try to support the C99 <span class="type">long long</span> type.
406 
    This requires that certain functions from your C library be present.
407 
    </p><p>
408 
    Up through release 3.0.2 the platform-specific tests performed by
409 
    libstdc++ were too general, resulting in a conservative approach
410 
    to enabling the <span class="type">long long</span> code paths. The most
411 
    commonly reported platform affected was Solaris.
412 
    </p><p>
413 
    This has been fixed for libstdc++ releases greater than 3.0.3.
414 
    </p></td></tr><tr class="question" title="4.3."><td align="left" valign="top"><a id="faq.predefined"></a><a id="q-predefined"></a><p><b>4.3.</b></p></td><td align="left" valign="top"><p>
415 
      <code class="constant">_XOPEN_SOURCE</code> and <code class="constant">_GNU_SOURCE</code> are always defined?
416 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-predefined"></a></td><td align="left" valign="top"><p>On Solaris, g++ (but not gcc) always defines the preprocessor
417 
         macro <code class="constant">_XOPEN_SOURCE</code>.  On GNU/Linux, the same happens
418 
         with <code class="constant">_GNU_SOURCE</code>.  (This is not an exhaustive list;
419 
         other macros and other platforms are also affected.)
420 
      </p><p>These macros are typically used in C library headers, guarding new
421 
         versions of functions from their older versions.  The C++ standard
422 
         library includes the C standard library, but it requires the C90
423 
         version, which for backwards-compatibility reasons is often not the
424 
         default for many vendors.
425 
      </p><p>More to the point, the C++ standard requires behavior which is only
426 
         available on certain platforms after certain symbols are defined.
427 
         Usually the issue involves I/O-related typedefs.  In order to
428 
         ensure correctness, the compiler simply predefines those symbols.
429 
      </p><p>Note that it's not enough to #define them only when the library is
430 
         being built (during installation).  Since we don't have an 'export'
431 
         keyword, much of the library exists as headers, which means that
432 
         the symbols must also be defined as your programs are parsed and
433 
         compiled.
434 
      </p><p>To see which symbols are defined, look for CPLUSPLUS_CPP_SPEC in
435 
         the gcc config headers for your target (and try changing them to
436 
         see what happens when building complicated code).  You can also run
437 
         <span class="command"><strong>g++ -E -dM - &lt; /dev/null"</strong></span> to display
438 
         a list of predefined macros for any particular installation.
439 
      </p><p>This has been discussed on the mailing lists
440 
         <a class="ulink" href="http://gcc.gnu.org/cgi-bin/htsearch?method=and&amp;format=builtin-long&amp;sort=score&amp;words=_XOPEN_SOURCE+Solaris" target="_top">quite a bit</a>.
441 
      </p><p>This method is something of a wart.  We'd like to find a cleaner
442 
         solution, but nobody yet has contributed the time.
443 
      </p></td></tr><tr class="question" title="4.4."><td align="left" valign="top"><a id="faq.darwin_ctype"></a><a id="q-darwin_ctype"></a><p><b>4.4.</b></p></td><td align="left" valign="top"><p>
444 
      Mac OS X <code class="filename">ctype.h</code> is broken! How can I fix it?
445 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-darwin_ctype"></a></td><td align="left" valign="top"><p>This is a long-standing bug in the OS X support.  Fortunately,
446 
         the patch is quite simple, and well-known.
447 
         <a class="ulink" href="http://gcc.gnu.org/ml/gcc/2002-03/msg00817.html" target="_top"> Here's a
448 
         link to the solution</a>.
449 
      </p></td></tr><tr class="question" title="4.5."><td align="left" valign="top"><a id="faq.threads_i386"></a><a id="q-threads_i386"></a><p><b>4.5.</b></p></td><td align="left" valign="top"><p>
450 
      Threading is broken on i386?
451 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-threads_i386"></a></td><td align="left" valign="top"><p>
452 
    </p><p>Support for atomic integer operations is/was broken on i386
453 
         platforms.  The assembly code accidentally used opcodes that are
454 
         only available on the i486 and later.  So if you configured GCC
455 
         to target, for example, i386-linux, but actually used the programs
456 
         on an i686, then you would encounter no problems.  Only when
457 
         actually running the code on a i386 will the problem appear.
458 
      </p><p>This is fixed in 3.2.2.
459 
      </p></td></tr><tr class="question" title="4.6."><td align="left" valign="top"><a id="faq.atomic_mips"></a><a id="q-atomic_mips"></a><p><b>4.6.</b></p></td><td align="left" valign="top"><p>
460 
      MIPS atomic operations
461 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-atomic_mips"></a></td><td align="left" valign="top"><p>
462 
    The atomic locking routines for MIPS targets requires MIPS II
463 
    and later.  A patch went in just after the 3.3 release to
464 
    make mips* use the generic implementation instead.  You can also
465 
    configure for mipsel-elf as a workaround.
466 
    </p><p>
467 
    The mips*-*-linux* port continues to use the MIPS II routines, and more
468 
    work in this area is expected.
469 
    </p></td></tr><tr class="question" title="4.7."><td align="left" valign="top"><a id="faq.linux_glibc"></a><a id="q-linux_glibc"></a><p><b>4.7.</b></p></td><td align="left" valign="top"><p>
470 
      Recent GNU/Linux glibc required?
471 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-linux_glibc"></a></td><td align="left" valign="top"><p>When running on GNU/Linux, libstdc++ 3.2.1 (shared library version
472 
         5.0.1) and later uses localization and formatting code from the system
473 
         C library (glibc) version 2.2.5.  That version of glibc is over a
474 
         year old and contains necessary bugfixes.  Many GNU/Linux distros make
475 
         glibc version 2.3.x available now.
476 
      </p><p>The guideline is simple:  the more recent the C++ library, the
477 
         more recent the C library.  (This is also documented in the main
478 
         GCC installation instructions.)
479 
      </p></td></tr><tr class="question" title="4.8."><td align="left" valign="top"><a id="faq.freebsd_wchar"></a><a id="q-freebsd_wchar"></a><p><b>4.8.</b></p></td><td align="left" valign="top"><p>
480 
      Can't use wchar_t/wstring on FreeBSD
481 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-freebsd_wchar"></a></td><td align="left" valign="top"><p>
482 
    Older versions of FreeBSD's C library do not have sufficient
483 
    support for wide character functions, and as a result the
484 
    libstdc++ configury decides that wchar_t support should be
485 
    disabled. In addition, the libstdc++ platform checks that
486 
    enabled <span class="type">wchar_t</span> were quite strict, and not granular
487 
    enough to detect when the minimal support to
488 
    enable <span class="type">wchar_t</span> and C++ library structures
489 
    like <code class="classname">wstring</code> were present. This impacted Solaris,
490 
    Darwin, and BSD variants, and is fixed in libstdc++ versions post 4.1.0.
491 
    </p><p>
492 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.known_bugs"></a>5. Known Bugs</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>5.1. <a href="faq.html#faq.what_works">
493 
      What works already?
494 
    </a></dt><dt>5.2. <a href="faq.html#faq.standard_bugs">
495 
      Bugs in the ISO C++ language or library specification
496 
    </a></dt><dt>5.3. <a href="faq.html#faq.compiler_bugs">
497 
      Bugs in the compiler (gcc/g++) and not libstdc++
498 
    </a></dt></dl></td></tr><tr class="question" title="5.1."><td align="left" valign="top"><a id="faq.what_works"></a><a id="q-what_works"></a><p><b>5.1.</b></p></td><td align="left" valign="top"><p>
499 
      What works already?
500 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-what_works"></a></td><td align="left" valign="top"><p>
501 
    Short answer: Pretty much everything <span class="emphasis"><em>works</em></span>
502 
    except for some corner cases.  Support for localization
503 
    in <code class="classname">locale</code> may be incomplete on non-GNU
504 
    platforms. Also dependant on the underlying platform is support
505 
    for <span class="type">wchar_t</span> and <span class="type">long
506 
    long</span> specializations, and details of thread support.
507 
    </p><p>
508 
    Long answer: See the implementation status pages for
509 
    <a class="link" href="manual/status.html#status.iso.1998" title="C++ 1998/2003">C++98</a>,
510 
    <a class="link" href="manual/status.html#status.iso.tr1" title="C++ TR1">TR1</a>, and
511 
    <a class="link" href="manual/status.html#status.iso.200x" title="C++ 200x">C++0x</a>.
512 
    </p></td></tr><tr class="question" title="5.2."><td align="left" valign="top"><a id="faq.standard_bugs"></a><a id="q-standard_bugs"></a><p><b>5.2.</b></p></td><td align="left" valign="top"><p>
513 
      Bugs in the ISO C++ language or library specification
514 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-standard_bugs"></a></td><td align="left" valign="top"><p>
515 
    Unfortunately, there are some.
516 
    </p><p>
517 
    For those people who are not part of the ISO Library Group
518 
    (i.e., nearly all of us needing to read this page in the first
519 
    place), a public list of the library defects is occasionally
520 
    published <a class="ulink" href="http://anubis.dkuug.dk/jtc1/sc22/wg21/" target="_top">here</a>.
521 
    Some of these issues have resulted in code changes in libstdc++.
522 
    </p><p>
523 
    If you think you've discovered a new bug that is not listed,
524 
    please post a message describing your problem
525 
    to <code class="email">&lt;<a class="email" href="mailto:libstdc++@gcc.gnu.org">libstdc++@gcc.gnu.org</a>&gt;</code> or the Usenet group
526 
    comp.lang.c++.moderated.
527 
    </p></td></tr><tr class="question" title="5.3."><td align="left" valign="top"><a id="faq.compiler_bugs"></a><a id="q-compiler_bugs"></a><p><b>5.3.</b></p></td><td align="left" valign="top"><p>
528 
      Bugs in the compiler (gcc/g++) and not libstdc++
529 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-compiler_bugs"></a></td><td align="left" valign="top"><p>
530 
    On occasion, the compiler is wrong. Please be advised that this
531 
    happens much less often than one would think, and avoid jumping to
532 
    conclusions.
533 
    </p><p>
534 
    First, examine the ISO C++ standard. Second, try another compiler
535 
    or an older version of the GNU compilers. Third, you can find more
536 
    information on the libstdc++ and the GCC mailing lists: search
537 
    these lists with terms describing your issue.
538 
    </p><p>
539 
    Before reporting a bug, please examine the
540 
    <a class="ulink" href="http://gcc.gnu.org/bugs.html" target="_top">bugs database</a> with the
541 
    category set to <span class="quote">“<span class="quote">g++</span>”</span>.
542 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.known_non-bugs"></a>6. Known Non-Bugs</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>6.1. <a href="faq.html#faq.stream_reopening_fails">
543 
      Reopening a stream fails
544 
    </a></dt><dt>6.2. <a href="faq.html#faq.wefcxx_verbose">
545 
      -Weffc++ complains too much
546 
    </a></dt><dt>6.3. <a href="faq.html#faq.ambiguous_overloads">
547 
      Ambiguous overloads after including an old-style header
548 
    </a></dt><dt>6.4. <a href="faq.html#faq.v2_headers">
549 
      The g++-3 headers are not ours
550 
    </a></dt><dt>6.5. <a href="faq.html#faq.boost_concept_checks">
551 
      Errors about *Concept and
552 
      constraints in the STL
553 
    </a></dt><dt>6.6. <a href="faq.html#faq.dlopen_crash">
554 
      Program crashes when using library code in a
555 
      dynamically-loaded library
556 
    </a></dt><dt>6.7. <a href="faq.html#faq.memory_leaks">
557 
      “Memory leaks” in containers
558 
    </a></dt><dt>6.8. <a href="faq.html#faq.list_size_on">
559 
      list::size() is O(n)!
560 
    </a></dt><dt>6.9. <a href="faq.html#faq.easy_to_fix">
561 
      Aw, that's easy to fix!
562 
    </a></dt></dl></td></tr><tr class="question" title="6.1."><td align="left" valign="top"><a id="faq.stream_reopening_fails"></a><a id="q-stream_reopening_fails"></a><p><b>6.1.</b></p></td><td align="left" valign="top"><p>
563 
      Reopening a stream fails
564 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-stream_reopening_fails"></a></td><td align="left" valign="top"><p>
565 
    One of the most-reported non-bug reports. Executing a sequence like:
566 
    </p><div class="literallayout"><p><br />
567 
    #include &lt;fstream&gt;<br />
568 
    ...<br />
569 
    std::fstream  fs(<span class="quote">“<span class="quote">a_file</span>”</span>);<br />
570 
    // .<br />
571 
    // . do things with fs...<br />
572 
    // .<br />
573 
    fs.close();<br />
574 
    fs.open(<span class="quote">“<span class="quote">a_new_file</span>”</span>);<br />
575 
    </p></div><p>
576 
    All operations on the re-opened <code class="varname">fs</code> will fail, or at
577 
    least act very strangely.  Yes, they often will, especially if
578 
    <code class="varname">fs</code> reached the EOF state on the previous file.  The
579 
    reason is that the state flags are <span class="emphasis"><em>not</em></span> cleared
580 
    on a successful call to open().  The standard unfortunately did
581 
    not specify behavior in this case, and to everybody's great sorrow,
582 
    the <a class="link" href="manual/bugs.html" title="Bugs">proposed LWG resolution in
583 
      DR #22</a> is to leave the flags unchanged.  You must insert a call
584 
    to <code class="function">fs.clear()</code> between the calls to close() and open(),
585 
    and then everything will work like we all expect it to work.
586 
    <span class="emphasis"><em>Update:</em></span> for GCC 4.0 we implemented the resolution
587 
    of <a class="link" href="manual/bugs.html" title="Bugs">DR #409</a> and open()
588 
    now calls <code class="function">clear()</code> on success!
589 
    </p></td></tr><tr class="question" title="6.2."><td align="left" valign="top"><a id="faq.wefcxx_verbose"></a><a id="q-wefcxx_verbose"></a><p><b>6.2.</b></p></td><td align="left" valign="top"><p>
590 
      -Weffc++ complains too much
591 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-wefcxx_verbose"></a></td><td align="left" valign="top"><p>
592 
    Many warnings are emitted when <code class="literal">-Weffc++</code> is used.  Making
593 
    libstdc++ <code class="literal">-Weffc++</code>-clean is not a goal of the project,
594 
    for a few reasons.  Mainly, that option tries to enforce
595 
    object-oriented programming, while the Standard Library isn't
596 
    necessarily trying to be OO.
597 
    </p><p>
598 
    We do, however, try to have libstdc++ sources as clean as possible. If
599 
    you see some simple changes that pacify <code class="literal">-Weffc++</code>
600 
    without other drawbacks, send us a patch.
601 
    </p></td></tr><tr class="question" title="6.3."><td align="left" valign="top"><a id="faq.ambiguous_overloads"></a><a id="q-ambiguous_overloads"></a><p><b>6.3.</b></p></td><td align="left" valign="top"><p>
602 
      Ambiguous overloads after including an old-style header
603 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-ambiguous_overloads"></a></td><td align="left" valign="top"><p>
604 
    Another problem is the <code class="literal">rel_ops</code> namespace and the template
605 
    comparison operator functions contained therein.  If they become
606 
    visible in the same namespace as other comparison functions
607 
    (e.g., <span class="quote">“<span class="quote">using</span>”</span> them and the &lt;iterator&gt; header),
608 
    then you will suddenly be faced with huge numbers of ambiguity
609 
    errors.  This was discussed on the -v3 list; Nathan Myers
610 
    <a class="ulink" href="http://gcc.gnu.org/ml/libstdc++/2001-01/msg00247.html" target="_top">sums
611 
      things up here</a>.  The collisions with vector/string iterator
612 
    types have been fixed for 3.1.
613 
    </p></td></tr><tr class="question" title="6.4."><td align="left" valign="top"><a id="faq.v2_headers"></a><a id="q-v2_headers"></a><p><b>6.4.</b></p></td><td align="left" valign="top"><p>
614 
      The g++-3 headers are <span class="emphasis"><em>not ours</em></span>
615 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-v2_headers"></a></td><td align="left" valign="top"><p>
616 
        If you have found an extremely broken header file which is
617 
        causing problems for you, look carefully before submitting a
618 
        "high" priority bug report (which you probably
619 
        shouldn't do anyhow; see the last paragraph of the page
620 
        describing <a class="ulink" href="http://gcc.gnu.org/bugs.html" target="_top">the GCC
621 
        bug database</a>).
622 
      </p><p>
623 
        If the headers are in <code class="filename">${prefix}/include/g++-3</code>, or
624 
        if the installed library's name looks like
625 
        <code class="filename">libstdc++-2.10.a</code> or
626 
        <code class="filename">libstdc++-libc6-2.10.so</code>, then you are using the
627 
        old libstdc++-v2 library, which is nonstandard and
628 
        unmaintained.  Do not report problems with -v2 to the -v3
629 
        mailing list.
630 
      </p><p>
631 
        For GCC versions 3.0 and 3.1 the libstdc++ header files are
632 
        installed in <code class="filename">${prefix}/include/g++-v3</code> (see the
633 
        'v'?).  Starting with version 3.2 the headers are installed in
634 
        <code class="filename">${prefix}/include/c++/${version}</code> as this prevents
635 
        headers from previous versions being found by mistake.
636 
      </p></td></tr><tr class="question" title="6.5."><td align="left" valign="top"><a id="faq.boost_concept_checks"></a><a id="q-boost_concept_checks"></a><p><b>6.5.</b></p></td><td align="left" valign="top"><p>
637 
      Errors about <span class="emphasis"><em>*Concept</em></span> and
638 
      <span class="emphasis"><em>constraints</em></span> in the STL
639 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-boost_concept_checks"></a></td><td align="left" valign="top"><p>
640 
    If you see compilation errors containing messages about
641 
    <span class="errortext">foo Concept </span>and something to do with a
642 
    <span class="errortext">constraints</span> member function, then most
643 
    likely you have violated one of the requirements for types used
644 
    during instantiation of template containers and functions.  For
645 
    example, EqualityComparableConcept appears if your types must be
646 
    comparable with == and you have not provided this capability (a
647 
    typo, or wrong visibility, or you just plain forgot, etc).
648 
    </p><p>
649 
    More information, including how to optionally enable/disable the
650 
    checks, is available
651 
    <a class="link" href="manual/bk01pt03ch08.html" title="Chapter 8. Concept Checking">here</a>.
652 
    </p></td></tr><tr class="question" title="6.6."><td align="left" valign="top"><a id="faq.dlopen_crash"></a><a id="q-dlopen_crash"></a><p><b>6.6.</b></p></td><td align="left" valign="top"><p>
653 
      Program crashes when using library code in a
654 
      dynamically-loaded library
655 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-dlopen_crash"></a></td><td align="left" valign="top"><p>
656 
    If you are using the C++ library across dynamically-loaded
657 
    objects, make certain that you are passing the correct options
658 
    when compiling and linking:
659 
    </p><div class="literallayout"><p><br />
660 
    // compile your library components<br />
661 
    g++ -fPIC -c a.cc<br />
662 
    g++ -fPIC -c b.cc<br />
663 
    ...<br />
664 
    g++ -fPIC -c z.cc<br />
665 
<br />
666 
    // create your library<br />
667 
    g++ -fPIC -shared -rdynamic -o libfoo.so a.o b.o ... z.o<br />
668 
<br />
669 
    // link the executable<br />
670 
    g++ -fPIC -rdynamic -o foo ... -L. -lfoo -ldl<br />
671 
    </p></div></td></tr><tr class="question" title="6.7."><td align="left" valign="top"><a id="faq.memory_leaks"></a><a id="q-memory_leaks"></a><p><b>6.7.</b></p></td><td align="left" valign="top"><p>
672 
      <span class="quote">“<span class="quote">Memory leaks</span>”</span> in containers
673 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-memory_leaks"></a></td><td align="left" valign="top"><p>
674 
    A few people have reported that the standard containers appear
675 
    to leak memory when tested with memory checkers such as
676 
    <a class="ulink" href="http://valgrind.org/" target="_top">valgrind</a>.
677 
    The library's default allocators keep free memory in a pool
678 
    for later reuse, rather than returning it to the OS.  Although
679 
    this memory is always reachable by the library and is never
680 
    lost, memory debugging tools can report it as a leak.  If you
681 
    want to test the library for memory leaks please read
682 
    <a class="link" href="manual/debug.html#debug.memory" title="Memory Leak Hunting">Tips for memory leak hunting</a>
683 
    first.
684 
    </p></td></tr><tr class="question" title="6.8."><td align="left" valign="top"><a id="faq.list_size_on"></a><a id="q-list_size_on"></a><p><b>6.8.</b></p></td><td align="left" valign="top"><p>
685 
      list::size() is O(n)!
686 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-list_size_on"></a></td><td align="left" valign="top"><p>
687 
    See
688 
    the <a class="link" href="manual/containers.html" title="Part VII.  Containers">Containers</a>
689 
    chapter.
690 
    </p></td></tr><tr class="question" title="6.9."><td align="left" valign="top"><a id="faq.easy_to_fix"></a><a id="q-easy_to_fix"></a><p><b>6.9.</b></p></td><td align="left" valign="top"><p>
691 
      Aw, that's easy to fix!
692 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-easy_to_fix"></a></td><td align="left" valign="top"><p>
693 
    If you have found a bug in the library and you think you have
694 
    a working fix, then send it in!  The main GCC site has a page
695 
    on <a class="ulink" href="http://gcc.gnu.org/contribute.html" target="_top">submitting
696 
    patches</a> that covers the procedure, but for libstdc++ you
697 
    should also send the patch to our mailing list in addition to
698 
    the GCC patches mailing list.  The libstdc++
699 
    <a class="link" href="manual/appendix_contributing.html" title="Appendix A.  Contributing">contributors' page</a>
700 
    also talks about how to submit patches.
701 
    </p><p>
702 
    In addition to the description, the patch, and the ChangeLog
703 
    entry, it is a Good Thing if you can additionally create a small
704 
    test program to test for the presence of the bug that your
705 
    patch fixes.  Bugs have a way of being reintroduced; if an old
706 
    bug creeps back in, it will be caught immediately by the
707 
    <a class="ulink" href="#2_4" target="_top">testsuite</a> -- but only if such a test exists.
708 
    </p></td></tr><tr class="qandadiv"><td align="left" valign="top" colspan="2"><h3 class="title"><a id="faq.misc"></a>7. Miscellaneous</h3></td></tr><tr class="toc"><td align="left" valign="top" colspan="2"><dl><dt>7.1. <a href="faq.html#faq.iterator_as_pod">
709 
      string::iterator is not char*; vector&lt;T&gt;::iterator is not T*
710 
    </a></dt><dt>7.2. <a href="faq.html#faq.what_is_next">
711 
      What's next after libstdc++?
712 
    </a></dt><dt>7.3. <a href="faq.html#faq.sgi_stl">
713 
      What about the STL from SGI?
714 
    </a></dt><dt>7.4. <a href="faq.html#faq.extensions_and_backwards_compat">
715 
      Extensions and Backward Compatibility
716 
    </a></dt><dt>7.5. <a href="faq.html#faq.tr1_support">
717 
      Does libstdc++ support TR1?
718 
    </a></dt><dt>7.6. <a href="faq.html#faq.get_iso_cxx">How do I get a copy of the ISO C++ Standard?
719 
    </a></dt><dt>7.7. <a href="faq.html#faq.what_is_abi">
720 
      What's an ABI and why is it so messy?
721 
    </a></dt><dt>7.8. <a href="faq.html#faq.size_equals_capacity">
722 
      How do I make std::vector&lt;T&gt;::capacity() == std::vector&lt;T&gt;::size?
723 
    </a></dt></dl></td></tr><tr class="question" title="7.1."><td align="left" valign="top"><a id="faq.iterator_as_pod"></a><a id="faq.iterator_as_pod_q"></a><p><b>7.1.</b></p></td><td align="left" valign="top"><p>
724 
      string::iterator is not char*; vector&lt;T&gt;::iterator is not T*
725 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="faq.iterator_as_pod_a"></a></td><td align="left" valign="top"><p>
726 
    If you have code that depends on container&lt;T&gt; iterators
727 
    being implemented as pointer-to-T, your code is broken. It's
728 
    considered a feature, not a bug, that libstdc++ points this out.
729 
    </p><p>
730 
    While there are arguments for iterators to be implemented in
731 
    that manner, A) they aren't very good ones in the long term,
732 
    and B) they were never guaranteed by the Standard anyway.  The
733 
    type-safety achieved by making iterators a real class rather
734 
    than a typedef for <span class="type">T*</span> outweighs nearly all opposing
735 
    arguments.
736 
    </p><p>
737 
    Code which does assume that a vector iterator <code class="varname">i</code>
738 
    is a pointer can often be fixed by changing <code class="varname">i</code> in
739 
    certain expressions to <code class="varname">&amp;*i</code>.  Future revisions
740 
    of the Standard are expected to bless this usage for
741 
    vector&lt;&gt; (but not for basic_string&lt;&gt;).
742 
    </p></td></tr><tr class="question" title="7.2."><td align="left" valign="top"><a id="faq.what_is_next"></a><a id="q-what_is_next"></a><p><b>7.2.</b></p></td><td align="left" valign="top"><p>
743 
      What's next after libstdc++?
744 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-what_is_next"></a></td><td align="left" valign="top"><p>
745 
        Hopefully, not much.  The goal of libstdc++ is to produce a
746 
        fully-compliant, fully-portable Standard Library.  After that,
747 
        we're mostly done: there won't <span class="emphasis"><em>be</em></span> any
748 
        more compliance work to do.
749 
      </p><p>
750 
        There is an effort underway to add significant extensions to
751 
        the standard library specification.  The latest version of
752 
        this effort is described in
753 
         <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf" target="_top">
754 
         The C++ Library Technical Report 1</a>.
755 
      </p></td></tr><tr class="question" title="7.3."><td align="left" valign="top"><a id="faq.sgi_stl"></a><a id="q-sgi_stl"></a><p><b>7.3.</b></p></td><td align="left" valign="top"><p>
756 
      What about the STL from SGI?
757 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-sgi_stl"></a></td><td align="left" valign="top"><p>
758 
      The <a class="ulink" href="http://www.sgi.com/tech/stl/" target="_top">STL from SGI</a>,
759 
    version 3.3, was the final merge of the STL codebase.  The
760 
    code in libstdc++ contains many fixes and changes, and
761 
    the SGI code is no longer under active
762 
    development.  We expect that no future merges will take place.
763 
    </p><p>
764 
    In particular, <code class="classname">string</code> is not from SGI and makes no
765 
    use of their "rope" class (which is included as an
766 
    optional extension), nor is <code class="classname">valarray</code> and some others.
767 
    Classes like <code class="classname">vector&lt;&gt;</code> are, but have been
768 
    extensively modified.
769 
    </p><p>
770 
    More information on the evolution of libstdc++ can be found at the
771 
    <a class="link" href="manual/api.html" title="API Evolution and Deprecation History">API
772 
    evolution</a>
773 
    and <a class="link" href="manual/backwards.html" title="Backwards Compatibility">backwards
774 
    compatibility</a> documentation.
775 
    </p><p>
776 
    The FAQ for SGI's STL (one jump off of their main page) is
777 
    still recommended reading.
778 
    </p></td></tr><tr class="question" title="7.4."><td align="left" valign="top"><a id="faq.extensions_and_backwards_compat"></a><a id="q-extensions_and_backwards_compat"></a><p><b>7.4.</b></p></td><td align="left" valign="top"><p>
779 
      Extensions and Backward Compatibility
780 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-extensions_and_backwards_compat"></a></td><td align="left" valign="top"><p>
781 
      See the <a class="link" href="manual/backwards.html" title="Backwards Compatibility">link</a> on backwards compatibility and <a class="link" href="manual/api.html" title="API Evolution and Deprecation History">link</a> on evolution.
782 
    </p></td></tr><tr class="question" title="7.5."><td align="left" valign="top"><a id="faq.tr1_support"></a><a id="q-tr1_support"></a><p><b>7.5.</b></p></td><td align="left" valign="top"><p>
783 
      Does libstdc++ support TR1?
784 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-tr1_support"></a></td><td align="left" valign="top"><p>
785 
    Yes.
786 
    </p><p>
787 
    The C++ Standard Library Technical Report adds many new features to
788 
    the library.  The latest version of this effort is described in
789 
    <a class="ulink" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf" target="_top">
790 
         Technical Report 1</a>.
791 
    </p><p>
792 
    The implementation status of TR1 in libstdc++ can be tracked <a class="link" href="manual/status.html#status.iso.tr1" title="C++ TR1">on the TR1 status
793 
    page</a>.
794 
    </p></td></tr><tr class="question" title="7.6."><td align="left" valign="top"><a id="faq.get_iso_cxx"></a><a id="q-get_iso_cxx"></a><p><b>7.6.</b></p></td><td align="left" valign="top"><p>How do I get a copy of the ISO C++ Standard?
795 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-get_iso_cxx"></a></td><td align="left" valign="top"><p>
796 
    Copies of the full ISO 14882 standard are available on line via
797 
    the ISO mirror site for committee members.  Non-members, or those
798 
    who have not paid for the privilege of sitting on the committee
799 
    and sustained their two-meeting commitment for voting rights, may
800 
    get a copy of the standard from their respective national
801 
    standards organization.  In the USA, this national standards
802 
    organization is ANSI and their website is
803 
    right <a class="ulink" href="http://www.ansi.org" target="_top">here</a>.  (And if
804 
    you've already registered with them, clicking this link will take
805 
    you to directly to the place where you can
806 
    <a class="ulink" href="http://webstore.ansi.org/RecordDetail.aspx?sku=ISO%2FIEC+14882:2003" target="_top">buy the standard on-line</a>.
807 
    </p><p>
808 
    Who is your country's member body?  Visit the
809 
    <a class="ulink" href="http://www.iso.ch/" target="_top">ISO homepage</a> and find out!
810 
    </p><p>
811 
    The 2003 version of the standard (the 1998 version plus TC1) is
812 
    available in print, ISBN 0-470-84674-7.
813 
    </p></td></tr><tr class="question" title="7.7."><td align="left" valign="top"><a id="faq.what_is_abi"></a><a id="q-what_is_abi"></a><p><b>7.7.</b></p></td><td align="left" valign="top"><p>
814 
      What's an ABI and why is it so messy?
815 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-what_is_abi"></a></td><td align="left" valign="top"><p>
816 
    <acronym class="acronym">ABI</acronym> stands for <span class="quote">“<span class="quote">Application Binary
817 
     Interface</span>”</span>.  Conventionally, it refers to a great
818 
    mass of details about how arguments are arranged on the call
819 
    stack and/or in registers, and how various types are arranged
820 
    and padded in structs.  A single CPU design may suffer
821 
    multiple ABIs designed by different development tool vendors
822 
    who made different choices, or even by the same vendor for
823 
    different target applications or compiler versions.  In ideal
824 
    circumstances the CPU designer presents one ABI and all the
825 
    OSes and compilers use it.  In practice every ABI omits
826 
    details that compiler implementers (consciously or
827 
    accidentally) must choose for themselves.
828 
    </p><p>
829 
    That ABI definition suffices for compilers to generate code so a
830 
    program can interact safely with an OS and its lowest-level libraries.
831 
    Users usually want an ABI to encompass more detail, allowing libraries
832 
    built with different compilers (or different releases of the same
833 
    compiler!) to be linked together.  For C++, this includes many more
834 
    details than for C, and CPU designers (for good reasons elaborated
835 
    below) have not stepped up to publish C++ ABIs.  The details include
836 
    virtual function implementation, struct inheritance layout, name
837 
    mangling, and exception handling.  Such an ABI has been defined for
838 
    GNU C++, and is immediately useful for embedded work relying only on
839 
    a <span class="quote">“<span class="quote">free-standing implementation</span>”</span> that doesn't include (much
840 
    of) the standard library.  It is a good basis for the work to come.
841 
    </p><p>
842 
    A useful C++ ABI must also incorporate many details of the standard
843 
    library implementation.  For a C ABI, the layouts of a few structs
844 
    (such as FILE, stat, jmpbuf, and the like) and a few macros suffice.
845 
    For C++, the details include the complete set of names of functions
846 
    and types used, the offsets of class members and virtual functions,
847 
    and the actual definitions of all inlines.  C++ exposes many more
848 
    library details to the caller than C does.  It makes defining
849 
    a complete ABI a much bigger undertaking, and requires not just
850 
    documenting library implementation details, but carefully designing
851 
    those details so that future bug fixes and optimizations don't
852 
    force breaking the ABI.
853 
    </p><p>
854 
    There are ways to help isolate library implementation details from the
855 
    ABI, but they trade off against speed.  Library details used in
856 
    inner loops (e.g., getchar) must be exposed and frozen for all
857 
    time, but many others may reasonably be kept hidden from user code,
858 
    so they may later be changed.  Deciding which, and implementing
859 
    the decisions, must happen before you can reasonably document a
860 
    candidate C++ ABI that encompasses the standard library.
861 
    </p></td></tr><tr class="question" title="7.8."><td align="left" valign="top"><a id="faq.size_equals_capacity"></a><a id="q-size_equals_capacity"></a><p><b>7.8.</b></p></td><td align="left" valign="top"><p>
862 
      How do I make std::vector&lt;T&gt;::capacity() == std::vector&lt;T&gt;::size?
863 
    </p></td></tr><tr class="answer"><td align="left" valign="top"><a id="a-size_equals_capacity"></a></td><td align="left" valign="top"><p>
864 
    The standard idiom for deallocating a <code class="classname">vector&lt;T&gt;</code>'s
865 
    unused memory is to create a temporary copy of the vector and swap their
866 
    contents, e.g. for <code class="classname">vector&lt;T&gt; v</code>
867 
    </p><div class="literallayout"><p><br />
868 
     std::vector&lt;T&gt;(v).swap(v);<br />
869 
    </p></div><p>
870 
    The copy will take O(n) time and the swap is constant time.
871 
    </p><p>
872 
    See <a class="link" href="manual/bk01pt05ch13s05.html" title="Shrink to Fit">Shrink-to-fit
873 
    strings</a> for a similar solution for strings.
874 
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