<?xml version="1.0" encoding="UTF-8" standalone="no"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Headers</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="start" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="using.html" title="Chapter 3. Using" /><link rel="prev" href="using.html" title="Chapter 3. Using" /><link rel="next" href="bk01pt01ch03s03.html" title="Namespaces" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Headers</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="bk01pt01ch03s03.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.headers"></a>Headers</h2></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.all"></a>Header Files</h3></div></div></div><p>The C++ standard specifies the entire set of header files thatmust be available to all hosted implementations. Actually, theword "files" is a misnomer, since the contents of theheaders don't necessarily have to be in any kind of externalfile. The only rule is that when one <code class="code">#include</code>'s aheader, the contents of that header become available, no matterhow.</p><p>That said, in practice files are used.</p><p>There are two main types of include files: header files relatedto a specific version of the ISO C++ standard (called StandardHeaders), and all others (TR1, C++ ABI, and Extensions).</p><p>Two dialects of standard headers are supported, corresponding tothe 1998 standard as updated for 2003, and the draft of theupcoming 200x standard.</p><p>C++98/03 include files. These are available in the default compilation mode, i.e. <code class="code">-std=c++98</code> or <code class="code">-std=gnu++98</code>.</p><div class="table"><a id="id424211"></a><p class="title"><b>Table 3.1. C++ 1998 Library Headers</b></p><div class="table-contents"><table summary="C++ 1998 Library Headers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col /></colgroup><tbody><tr><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="filename">iomanip</code></td><td align="left"><code class="filename">list</code></td><td align="left"><code class="filename">ostream</code></td><td align="left"><code class="filename">streambuf</code></td></tr><tr><td align="left"><code class="filename">bitset</code></td><td align="left"><code class="filename">ios</code></td><td align="left"><code class="filename">locale</code></td><td align="left"><code class="filename">queue</code></td><td align="left"><code class="filename">string</code></td></tr><tr><td align="left"><code class="filename">complex</code></td><td align="left"><code class="filename">iosfwd</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="filename">typeinfo</code></td></tr><tr><td align="left"><code class="filename">deque</code></td><td align="left"><code class="filename">iostream</code></td><td align="left"><code class="filename">memory</code></td><td align="left"><code class="filename">sstream</code></td><td align="left"><code class="filename">utility</code></td></tr><tr><td align="left"><code class="filename">exception</code></td><td align="left"><code class="filename">istream</code></td><td align="left"><code class="filename">new</code></td><td align="left"><code class="filename">stack</code></td><td align="left"><code class="filename">valarray</code></td></tr><tr><td align="left"><code class="filename">fstream</code></td><td align="left"><code class="filename">iterator</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="filename">stdexcept</code></td><td align="left"><code class="filename">vector</code></td></tr><tr><td align="left"><code class="filename">functional</code></td><td align="left"><code class="filename">limits</code></td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="id410652"></a><p class="title"><b>Table 3.2. C++ 1998 Library Headers for C Library Facilities</b></p><div class="table-contents"><table summary="C++ 1998 Library Headers for C Library Facilities" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col /></colgroup><tbody><tr><td align="left"><code class="filename">cassert</code></td><td align="left"><code class="filename">ciso646</code></td><td align="left"><code class="filename">csetjmp</code></td><td align="left"><code class="filename">cstdio</code></td><td align="left"><code class="filename">ctime</code></td></tr><tr><td align="left"><code class="filename">cctype</code></td><td align="left"><code class="filename">climits</code></td><td align="left"><code class="filename">csignal</code></td><td align="left"><code class="filename">cstdlib</code></td><td align="left"><code class="filename">cwchar</code></td></tr><tr><td align="left"><code class="filename">cerrno</code></td><td align="left"><code class="filename">clocale</code></td><td align="left"><code class="filename">cstdarg</code></td><td align="left"><code class="filename">cstring</code></td><td align="left"><code class="filename">cwctype</code></td></tr><tr><td align="left"><code class="filename">cfloat</code></td><td align="left"><code class="filename">cmath</code></td><td align="left"><code class="filename">cstddef</code></td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><p>C++0x include files. These are only available in C++0x compilation mode, i.e. <code class="code">-std=c++0x</code> or <code class="code">-std=gnu++0x</code>.</p><p></p><div class="table"><a id="id411001"></a><p class="title"><b>Table 3.3. C++ 200x Library Headers</b></p><div class="table-contents"><table summary="C++ 200x Library Headers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col /></colgroup><tbody><tr><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="filename">iomanip</code></td><td align="left"><code class="filename">locale</code></td><td align="left"><code class="filename">regex</code></td><td align="left"><code class="filename">tuple</code></td></tr><tr><td align="left"><code class="filename">array</code></td><td align="left"><code class="filename">ios</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="filename">typeinfo</code></td></tr><tr><td align="left"><code class="filename">bitset</code></td><td align="left"><code class="filename">iosfwd</code></td><td align="left"><code class="filename">memory</code></td><td align="left"><code class="filename">sstream</code></td><td align="left"><code class="filename">type_traits</code></td></tr><tr><td align="left"><code class="filename">complex</code></td><td align="left"><code class="filename">iostream</code></td><td align="left"><code class="filename">new</code></td><td align="left"><code class="filename">stack</code></td><td align="left"><code class="filename">unordered_map</code></td></tr><tr><td align="left"><code class="filename">deque</code></td><td align="left"><code class="filename">istream</code></td><td align="left"><code class="filename">numeric</code></td><td align="left"><code class="filename">stdexcept</code></td><td align="left"><code class="filename">unordered_set</code></td></tr><tr><td align="left"><code class="filename">exception</code></td><td align="left"><code class="filename">iterator</code></td><td align="left"><code class="filename">ostream</code></td><td align="left"><code class="filename">streambuf</code></td><td align="left"><code class="filename">utility</code></td></tr><tr><td align="left"><code class="filename">fstream</code></td><td align="left"><code class="filename">limits</code></td><td align="left"><code class="filename">queue</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="filename">valarray</code></td></tr><tr><td align="left"><code class="filename">functional</code></td><td align="left"><code class="filename">list</code></td><td align="left"><code class="filename">random</code></td><td align="left"><code class="filename">system_error</code></td><td align="left"><code class="filename">vector</code></td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="id456739"></a><p class="title"><b>Table 3.4. C++ 200x Library Headers for C Library Facilities</b></p><div class="table-contents"><table summary="C++ 200x Library Headers for C Library Facilities" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">cassert</code></td><td align="left"><code class="filename">cfloat</code></td><td align="left"><code class="filename">cmath</code></td><td align="left"><code class="filename">cstddef</code></td><td align="left"><code class="filename">ctgmath</code></td></tr><tr><td align="left"><code class="filename">ccomplex</code></td><td align="left"><code class="filename">cinttypes</code></td><td align="left"><code class="filename">csetjmp</code></td><td align="left"><code class="filename">cstdint</code></td><td align="left"><code class="filename">ctime</code></td></tr><tr><td align="left"><code class="filename">cctype</code></td><td align="left"><code class="filename">ciso646</code></td><td align="left"><code class="filename">csignal</code></td><td align="left"><code class="filename">cstdio</code></td><td align="left"><code class="filename">cuchar</code></td></tr><tr><td align="left"><code class="filename">cerrno</code></td><td align="left"><code class="filename">climits</code></td><td align="left"><code class="filename">cstdarg</code></td><td align="left"><code class="filename">cstdlib</code></td><td align="left"><code class="filename">cwchar</code></td></tr><tr><td align="left"><code class="filename">cfenv</code></td><td align="left"><code class="filename">clocale</code></td><td align="left"><code class="filename">cstdbool</code></td><td align="left"><code class="filename">cstring</code></td><td align="left"><code class="filename">cwctype</code></td></tr></tbody></table></div></div><br class="table-break" /><p>In addition, TR1 includes as:</p><div class="table"><a id="id420313"></a><p class="title"><b>Table 3.5. C++ TR1 Library Headers</b></p><div class="table-contents"><table summary="C++ TR1 Library Headers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">tr1/array</code></td><td align="left"><code class="filename">tr1/memory</code></td><td align="left"><code class="filename">tr1/regex</code></td><td align="left"><code class="filename">tr1/type_traits</code></td><td align="left"><code class="filename">tr1/unordered_set</code></td></tr><tr><td align="left"><code class="filename">tr1/complex</code></td><td align="left"><code class="filename">tr1/random</code></td><td align="left"><code class="filename">tr1/tuple</code></td><td align="left"><code class="filename">tr1/unordered_map</code></td><td align="left"><code class="filename">tr1/utility</code></td></tr><tr><td align="left"><code class="filename">tr1/functional</code></td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="id362939"></a><p class="title"><b>Table 3.6. C++ TR1 Library Headers for C Library Facilities</b></p><div class="table-contents"><table summary="C++ TR1 Library Headers for C Library Facilities" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">tr1/cmath</code></td><td align="left"><code class="filename">tr1/cfloat</code></td><td align="left"><code class="filename">tr1/cstdarg</code></td><td align="left"><code class="filename">tr1/cstdio</code></td><td align="left"><code class="filename">tr1/ctime</code></td></tr><tr><td align="left"><code class="filename">tr1/ccomplex</code></td><td align="left"><code class="filename">tr1/cinttypes</code></td><td align="left"><code class="filename">tr1/cstdbool</code></td><td align="left"><code class="filename">tr1/cstdlib</code></td><td align="left"><code class="filename">tr1/cwchar</code></td></tr><tr><td align="left"><code class="filename">tr1/cfenv</code></td><td align="left"><code class="filename">tr1/climits</code></td><td align="left"><code class="filename">tr1/cstdint</code></td><td align="left"><code class="filename">tr1/ctgmath</code></td><td align="left"><code class="filename">tr1/cwctype</code></td></tr></tbody></table></div></div><br class="table-break" /><p>Also included are files for the C++ ABI interface:</p><div class="table"><a id="id429435"></a><p class="title"><b>Table 3.7. C++ ABI Headers</b></p><div class="table-contents"><table summary="C++ ABI Headers" border="1"><colgroup><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">cxxabi.h</code></td><td align="left"><code class="filename">cxxabi_forced.h</code></td></tr></tbody></table></div></div><br class="table-break" /><p>And a large variety of extensions.</p><div class="table"><a id="id490019"></a><p class="title"><b>Table 3.8. Extension Headers</b></p><div class="table-contents"><table summary="Extension Headers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">ext/algorithm</code></td><td align="left"><code class="filename">ext/debug_allocator.h</code></td><td align="left"><code class="filename">ext/mt_allocator.h</code></td><td align="left"><code class="filename">ext/pod_char_traits.h</code></td><td align="left"><code class="filename">ext/stdio_sync_filebuf.h</code></td></tr><tr><td align="left"><code class="filename">ext/array_allocator.h</code></td><td align="left"><code class="filename">ext/enc_filebuf.h</code></td><td align="left"><code class="filename">ext/new_allocator.h</code></td><td align="left"><code class="filename">ext/pool_allocator.h</code></td><td align="left"><code class="filename">ext/throw_allocator.h</code></td></tr><tr><td align="left"><code class="filename">ext/atomicity.h</code></td><td align="left"><code class="filename">ext/functional</code></td><td align="left"><code class="filename">ext/numeric</code></td><td align="left"><code class="filename">ext/rb_tree</code></td><td align="left"><code class="filename">ext/typelist.h</code></td></tr><tr><td align="left"><code class="filename">ext/bitmap_allocator.h</code></td><td align="left"><code class="filename">ext/iterator</code></td><td align="left"><code class="filename">ext/numeric_traits.h</code></td><td align="left"><code class="filename">ext/rope</code></td><td align="left"><code class="filename">ext/type_traits.h</code></td></tr><tr><td align="left"><code class="filename">ext/codecvt_specializations.h</code></td><td align="left"><code class="filename">ext/malloc_allocator.h</code></td><td align="left"><code class="filename">ext/pb_ds/assoc_container.h</code></td><td align="left"><code class="filename">ext/slist</code></td><td align="left"><code class="filename">ext/vstring.h</code></td></tr><tr><td align="left"><code class="filename">ext/concurrence.h</code></td><td align="left"><code class="filename">ext/memory</code></td><td align="left"><code class="filename">ext/pb_ds/priority_queue.h</code></td><td align="left"><code class="filename">ext/stdio_filebuf.h</code></td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="id421980"></a><p class="title"><b>Table 3.9. Extension Debug Headers</b></p><div class="table-contents"><table summary="Extension Debug Headers" border="1"><colgroup><col align="left" /><col align="left" /><col align="left" /><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">debug/bitset</code></td><td align="left"><code class="filename">debug/list</code></td><td align="left"><code class="filename">debug/set</code></td><td align="left"><code class="filename">debug/unordered_map</code></td><td align="left"><code class="filename">debug/vector</code></td></tr><tr><td align="left"><code class="filename">debug/deque</code></td><td align="left"><code class="filename">debug/map</code></td><td align="left"><code class="filename">debug/string</code></td><td align="left"><code class="filename">debug/unordered_set</code></td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="id362228"></a><p class="title"><b>Table 3.10. Extension Parallel Headers</b></p><div class="table-contents"><table summary="Extension Parallel Headers" border="1"><colgroup><col align="left" /><col align="left" /></colgroup><tbody><tr><td align="left"><code class="filename">parallel/algorithm</code></td><td align="left"><code class="filename">parallel/numeric</code></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.mixing"></a>Mixing Headers</h3></div></div></div><p> A few simple rules.</p><p>First, mixing different dialects of the standard headers is notpossible. It's an all-or-nothing affair. Thus, code like</p><pre class="programlisting">#include <array>#include <functional></pre><p>Implies C++0x mode. To use the entities in <array>, the C++0xcompilation mode must be used, which implies the C++0x functionality(and deprecations) in <functional> will be present.</p><p>Second, the other headers can be included with either dialect ofthe standard headers, although features and types specific to C++0xare still only enabled when in C++0x compilation mode. So, to uservalue references with <code class="code">__gnu_cxx::vstring</code>, or to use thedebug-mode versions of <code class="code">std::unordered_map</code>, one must usethe <code class="code">std=gnu++0x</code> compiler flag. (Or <code class="code">std=c++0x</code>, of course.)</p><p>A special case of the second rule is the mixing of TR1 and C++0xfacilities. It is possible (although not especially prudent) toinclude both the TR1 version and the C++0x version of header in thesame translation unit:</p><pre class="programlisting">#include <tr1/type_traits>#include <type_traits></pre><p> Several parts of C++0x diverge quite substantially from TR1 predecessors.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.cheaders"></a>The C Headers and <code class="code">namespace std</code></h3></div></div></div><p>The standard specifies that if one includes the C-style header(<math.h> in this case), the symbols will be availablein the global namespace and perhaps innamespace <code class="code">std::</code> (but this is no longer a firmrequirement.) One the other hand, including the C++-styleheader (<cmath>) guarantees that the entities will befound in namespace std and perhaps in the global namespace.</p><p>Usage of C++-style headers is recommended, as thenC-linkage names can be disambiguated by explicit qualification, suchas by <code class="code">std::abort</code>. In addition, the C++-style headers canuse function overloading to provide a simpler interface to certainfamilies of C-functions. For instance in <cmath>, thefunction <code class="code">std::sin</code> has overloads for all the builtinfloating-point types. This means that <code class="code">std::sin</code> can beused uniformly, instead of a combinationof <code class="code">std::sinf</code>, <code class="code">std::sin</code>,and <code class="code">std::sinl</code>.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.pre"></a>Precompiled Headers</h3></div></div></div><p>There are three base header files that are provided. They can beused to precompile the standard headers and extensions into binaryfiles that may the be used to speed compiles that use these headers.</p><div class="itemizedlist"><ul type="disc"><li><p>stdc++.h</p><p>Includes all standard headers. Actual content varies depending onlanguage dialect.</p></li><li><p>stdtr1c++.h</p><p>Includes all of <stdc++.h>, and adds all the TR1 headers.</p></li><li><p>extc++.h</p><p>Includes all of <stdtr1c++.h>, and adds all the Extension headers.</p></li></ul></div><p>How to construct a .gch file from one of these base header files.</p><p>First, find the include directory for the compiler. One way to dothis is:</p><pre class="programlisting">g++ -v hello.cc#include <...> search starts here:/mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0...End of search list.</pre><p>Then, create a precompiled header file with the same flags thatwill be used to compile other projects.</p><pre class="programlisting">g++ -Winvalid-pch -x c++-header -g -O2 -o ./stdc++.h.gch /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h</pre><p>The resulting file will be quite large: the current size is aroundthirty megabytes. </p><p>How to use the resulting file.</p><pre class="programlisting">g++ -I. -include stdc++.h -H -g -O2 hello.cc</pre><p>Verification that the PCH file is being used is easy:</p><pre class="programlisting">g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe! ./stdc++.h.gch. /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0/iostream. /mnt/share/bld/H-x86-gcc.20071201include/c++/4.3.0/string</pre><p>The exclamation point to the left of the <code class="code">stdc++.h.gch</code> listing means that the generated PCH file was used, and thus the </p><p></p><p> Detailed information about creating precompiled header files can be found in the GCC <a class="ulink" href="http://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html" target="_top">documentation</a>.</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="bk01pt01ch03s03.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 3. 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