libstdc++-v3/doc/html/manual/using_headers.html


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Headers</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="using.html" title="Chapter 3. Using"/><link rel="prev" href="using.html" title="Chapter 3. Using"/><link rel="next" href="using_macros.html" title="Macros"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Headers</th></tr><tr><td align="left"><a accesskey="p" href="using.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td align="right"> <a accesskey="n" href="using_macros.html">Next</a></td></tr></table><hr/></div><div class="section" title="Headers"><div class="titlepage"><div><div><h2 class="title"><a id="manual.intro.using.headers"/>Headers</h2></div></div></div><div class="section" title="Header Files"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.all"/>Header Files</h3></div></div></div><p>
     The C++ standard specifies the entire set of header files that
     must be available to all hosted implementations.  Actually, the
     word "files" is a misnomer, since the contents of the
     headers don't necessarily have to be in any kind of external
     file.  The only rule is that when one <code class="code">#include</code>'s a
     header, the contents of that header become available, no matter
     how.
   </p><p>
   That said, in practice files are used.
   </p><p>
     There are two main types of include files: header files related
     to a specific version of the ISO C++ standard (called Standard
     Headers), and all others (TR1, C++ ABI, and Extensions).
   </p><p>
     Two dialects of standard headers are supported, corresponding to
     the 1998 standard as updated for 2003, and the draft of the
     upcoming 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="id466139"/><p class="title"><strong>Table 3.2. C++ 1998 Library Headers</strong></p><div class="table-contents"><table summary="C++ 1998 Library Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">algorithm</code></td><td style="text-align: left"><code class="filename">bitset</code></td><td style="text-align: left"><code class="filename">complex</code></td><td style="text-align: left"><code class="filename">deque</code></td><td style="text-align: left"><code class="filename">exception</code></td></tr><tr><td style="text-align: left"><code class="filename">fstream</code></td><td style="text-align: left"><code class="filename">functional</code></td><td style="text-align: left"><code class="filename">iomanip</code></td><td style="text-align: left"><code class="filename">ios</code></td><td style="text-align: left"><code class="filename">iosfwd</code></td></tr><tr><td style="text-align: left"><code class="filename">iostream</code></td><td style="text-align: left"><code class="filename">istream</code></td><td style="text-align: left"><code class="filename">iterator</code></td><td style="text-align: left"><code class="filename">limits</code></td><td style="text-align: left"><code class="filename">list</code></td></tr><tr><td style="text-align: left"><code class="filename">locale</code></td><td style="text-align: left"><code class="filename">map</code></td><td style="text-align: left"><code class="filename">memory</code></td><td style="text-align: left"><code class="filename">new</code></td><td style="text-align: left"><code class="filename">numeric</code></td></tr><tr><td style="text-align: left"><code class="filename">ostream</code></td><td style="text-align: left"><code class="filename">queue</code></td><td style="text-align: left"><code class="filename">set</code></td><td style="text-align: left"><code class="filename">sstream</code></td><td style="text-align: left"><code class="filename">stack</code></td></tr><tr><td style="text-align: left"><code class="filename">stdexcept</code></td><td style="text-align: left"><code class="filename">streambuf</code></td><td style="text-align: left"><code class="filename">string</code></td><td style="text-align: left"><code class="filename">utility</code></td><td style="text-align: left"><code class="filename">typeinfo</code></td></tr><tr><td style="text-align: left"><code class="filename">valarray</code></td><td style="text-align: left"><code class="filename">vector</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/><div class="table"><a id="id466443"/><p class="title"><strong>Table 3.3. C++ 1998 Library Headers for C Library Facilities</strong></p><div class="table-contents"><table summary="C++ 1998 Library Headers for C Library Facilities" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">cassert</code></td><td style="text-align: left"><code class="filename">cerrno</code></td><td style="text-align: left"><code class="filename">cctype</code></td><td style="text-align: left"><code class="filename">cfloat</code></td><td style="text-align: left"><code class="filename">ciso646</code></td></tr><tr><td style="text-align: left"><code class="filename">climits</code></td><td style="text-align: left"><code class="filename">clocale</code></td><td style="text-align: left"><code class="filename">cmath</code></td><td style="text-align: left"><code class="filename">csetjmp</code></td><td style="text-align: left"><code class="filename">csignal</code></td></tr><tr><td style="text-align: left"><code class="filename">cstdarg</code></td><td style="text-align: left"><code class="filename">cstddef</code></td><td style="text-align: left"><code class="filename">cstdio</code></td><td style="text-align: left"><code class="filename">cstdlib</code></td><td style="text-align: left"><code class="filename">cstring</code></td></tr><tr><td style="text-align: left"><code class="filename">ctime</code></td><td style="text-align: left"><code class="filename">cwchar</code></td><td style="text-align: left"><code class="filename">cwctype</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="literal">-std=c++0x</code> or <code class="literal">-std=gnu++0x</code>.
</p><p/><div class="table"><a id="id466649"/><p class="title"><strong>Table 3.4. C++ 200x Library Headers</strong></p><div class="table-contents"><table summary="C++ 200x Library Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">algorithm</code></td><td style="text-align: left"><code class="filename">array</code></td><td style="text-align: left"><code class="filename">bitset</code></td><td style="text-align: left"><code class="filename">chrono</code></td><td style="text-align: left"><code class="filename">complex</code></td></tr><tr><td style="text-align: left"><code class="filename">condition_variable</code></td><td style="text-align: left"><code class="filename">deque</code></td><td style="text-align: left"><code class="filename">exception</code></td><td style="text-align: left"><code class="filename">forward_list</code></td><td style="text-align: left"><code class="filename">fstream</code></td></tr><tr><td style="text-align: left"><code class="filename">functional</code></td><td style="text-align: left"><code class="filename">future</code></td><td style="text-align: left"><code class="filename">initalizer_list</code></td><td style="text-align: left"><code class="filename">iomanip</code></td><td style="text-align: left"><code class="filename">ios</code></td></tr><tr><td style="text-align: left"><code class="filename">iosfwd</code></td><td style="text-align: left"><code class="filename">iostream</code></td><td style="text-align: left"><code class="filename">istream</code></td><td style="text-align: left"><code class="filename">iterator</code></td><td style="text-align: left"><code class="filename">limits</code></td></tr><tr><td style="text-align: left"><code class="filename">list</code></td><td style="text-align: left"><code class="filename">locale</code></td><td style="text-align: left"><code class="filename">map</code></td><td style="text-align: left"><code class="filename">memory</code></td><td style="text-align: left"><code class="filename">mutex</code></td></tr><tr><td style="text-align: left"><code class="filename">new</code></td><td style="text-align: left"><code class="filename">numeric</code></td><td style="text-align: left"><code class="filename">ostream</code></td><td style="text-align: left"><code class="filename">queue</code></td><td style="text-align: left"><code class="filename">random</code></td></tr><tr><td style="text-align: left"><code class="filename">ratio</code></td><td style="text-align: left"><code class="filename">regex</code></td><td style="text-align: left"><code class="filename">set</code></td><td style="text-align: left"><code class="filename">sstream</code></td><td style="text-align: left"><code class="filename">stack</code></td></tr><tr><td style="text-align: left"><code class="filename">stdexcept</code></td><td style="text-align: left"><code class="filename">streambuf</code></td><td style="text-align: left"><code class="filename">string</code></td><td style="text-align: left"><code class="filename">system_error</code></td><td style="text-align: left"><code class="filename">thread</code></td></tr><tr><td style="text-align: left"><code class="filename">tuple</code></td><td style="text-align: left"><code class="filename">type_traits</code></td><td style="text-align: left"><code class="filename">typeinfo</code></td><td style="text-align: left"><code class="filename">unordered_map</code></td><td style="text-align: left"><code class="filename">unordered_set</code></td></tr><tr><td style="text-align: left"><code class="filename">utility</code></td><td style="text-align: left"><code class="filename">valarray</code></td><td style="text-align: left"><code class="filename">vector</code></td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break"/><p/><div class="table"><a id="id467078"/><p class="title"><strong>Table 3.5. C++ 200x Library Headers for C Library Facilities</strong></p><div class="table-contents"><table summary="C++ 200x Library Headers for C Library Facilities" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">cassert</code></td><td style="text-align: left"><code class="filename">ccomplex</code></td><td style="text-align: left"><code class="filename">cctype</code></td><td style="text-align: left"><code class="filename">cerrno</code></td><td style="text-align: left"><code class="filename">cfenv</code></td></tr><tr><td style="text-align: left"><code class="filename">cfloat</code></td><td style="text-align: left"><code class="filename">cinttypes</code></td><td style="text-align: left"><code class="filename">ciso646</code></td><td style="text-align: left"><code class="filename">climits</code></td><td style="text-align: left"><code class="filename">clocale</code></td></tr><tr><td style="text-align: left"><code class="filename">cmath</code></td><td style="text-align: left"><code class="filename">csetjmp</code></td><td style="text-align: left"><code class="filename">csignal</code></td><td style="text-align: left"><code class="filename">cstdarg</code></td><td style="text-align: left"><code class="filename">cstdbool</code></td></tr><tr><td style="text-align: left"><code class="filename">cstddef</code></td><td style="text-align: left"><code class="filename">cstdint</code></td><td style="text-align: left"><code class="filename">cstdlib</code></td><td style="text-align: left"><code class="filename">cstdio</code></td><td style="text-align: left"><code class="filename">cstring</code></td></tr><tr><td style="text-align: left"><code class="filename">ctgmath</code></td><td style="text-align: left"><code class="filename">ctime</code></td><td style="text-align: left"><code class="filename">cuchar</code></td><td style="text-align: left"><code class="filename">cwchar</code></td><td style="text-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="id467327"/><p class="title"><strong>Table 3.6. C++ TR 1 Library Headers</strong></p><div class="table-contents"><table summary="C++ TR 1 Library Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">tr1/array</code></td><td style="text-align: left"><code class="filename">tr1/complex</code></td><td style="text-align: left"><code class="filename">tr1/memory</code></td><td style="text-align: left"><code class="filename">tr1/functional</code></td><td style="text-align: left"><code class="filename">tr1/random</code></td></tr><tr><td style="text-align: left"><code class="filename">tr1/regex</code></td><td style="text-align: left"><code class="filename">tr1/tuple</code></td><td style="text-align: left"><code class="filename">tr1/type_traits</code></td><td style="text-align: left"><code class="filename">tr1/unordered_map</code></td><td style="text-align: left"><code class="filename">tr1/unordered_set</code></td></tr><tr><td style="text-align: left"><code class="filename">tr1/utility</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/><div class="table"><a id="id467468"/><p class="title"><strong>Table 3.7. C++ TR 1 Library Headers for C Library Facilities</strong></p><div class="table-contents"><table summary="C++ TR 1 Library Headers for C Library Facilities" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">tr1/ccomplex</code></td><td style="text-align: left"><code class="filename">tr1/cfenv</code></td><td style="text-align: left"><code class="filename">tr1/cfloat</code></td><td style="text-align: left"><code class="filename">tr1/cmath</code></td><td style="text-align: left"><code class="filename">tr1/cinttypes</code></td></tr><tr><td style="text-align: left"><code class="filename">tr1/climits</code></td><td style="text-align: left"><code class="filename">tr1/cstdarg</code></td><td style="text-align: left"><code class="filename">tr1/cstdbool</code></td><td style="text-align: left"><code class="filename">tr1/cstdint</code></td><td style="text-align: left"><code class="filename">tr1/cstdio</code></td></tr><tr><td style="text-align: left"><code class="filename">tr1/cstdlib</code></td><td style="text-align: left"><code class="filename">tr1/ctgmath</code></td><td style="text-align: left"><code class="filename">tr1/ctime</code></td><td style="text-align: left"><code class="filename">tr1/cwchar</code></td><td style="text-align: left"><code class="filename">tr1/cwctype</code></td></tr></tbody></table></div></div><br class="table-break"/><p>Decimal floating-point arithmetic is available if the C++
compiler supports scalar decimal floating-point types defined via
<code class="code">__attribute__((mode(SD|DD|LD)))</code>.
</p><div class="table"><a id="id467644"/><p class="title"><strong>Table 3.8. C++ TR 24733 Decimal Floating-Point Header</strong></p><div class="table-contents"><table summary="C++ TR 24733 Decimal Floating-Point Header" border="1"><colgroup><col style="text-align: left" class="c1"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">decimal/decimal</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="id467690"/><p class="title"><strong>Table 3.9. C++ ABI Headers</strong></p><div class="table-contents"><table summary="C++ ABI Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">cxxabi.h</code></td><td style="text-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="id467743"/><p class="title"><strong>Table 3.10. Extension Headers</strong></p><div class="table-contents"><table summary="Extension Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">ext/algorithm</code></td><td style="text-align: left"><code class="filename">ext/atomicity.h</code></td><td style="text-align: left"><code class="filename">ext/array_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/bitmap_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/cast.h</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/codecvt_specializations.h</code></td><td style="text-align: left"><code class="filename">ext/concurrence.h</code></td><td style="text-align: left"><code class="filename">ext/debug_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/enc_filebuf.h</code></td><td style="text-align: left"><code class="filename">ext/extptr_allocator.h</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/functional</code></td><td style="text-align: left"><code class="filename">ext/iterator</code></td><td style="text-align: left"><code class="filename">ext/malloc_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/memory</code></td><td style="text-align: left"><code class="filename">ext/mt_allocator.h</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/new_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/numeric</code></td><td style="text-align: left"><code class="filename">ext/numeric_traits.h</code></td><td style="text-align: left"><code class="filename">ext/pb_ds/assoc_container.h</code></td><td style="text-align: left"><code class="filename">ext/pb_ds/priority_queue.h</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/pod_char_traits.h</code></td><td style="text-align: left"><code class="filename">ext/pool_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/rb_tree</code></td><td style="text-align: left"><code class="filename">ext/rope</code></td><td style="text-align: left"><code class="filename">ext/slist</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/stdio_filebuf.h</code></td><td style="text-align: left"><code class="filename">ext/stdio_sync_filebuf.h</code></td><td style="text-align: left"><code class="filename">ext/throw_allocator.h</code></td><td style="text-align: left"><code class="filename">ext/typelist.h</code></td><td style="text-align: left"><code class="filename">ext/type_traits.h</code></td></tr><tr><td style="text-align: left"><code class="filename">ext/vstring.h</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/><div class="table"><a id="id468041"/><p class="title"><strong>Table 3.11. Extension Debug Headers</strong></p><div class="table-contents"><table summary="Extension Debug Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/><col style="text-align: left" class="c5"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">debug/bitset</code></td><td style="text-align: left"><code class="filename">debug/deque</code></td><td style="text-align: left"><code class="filename">debug/list</code></td><td style="text-align: left"><code class="filename">debug/map</code></td><td style="text-align: left"><code class="filename">debug/set</code></td></tr><tr><td style="text-align: left"><code class="filename">debug/string</code></td><td style="text-align: left"><code class="filename">debug/unordered_map</code></td><td style="text-align: left"><code class="filename">debug/unordered_set</code></td><td style="text-align: left"><code class="filename">debug/vector</code></td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break"/><p/><div class="table"><a id="id468164"/><p class="title"><strong>Table 3.12. Extension Profile Headers</strong></p><div class="table-contents"><table summary="Extension Profile Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/><col style="text-align: left" class="c3"/><col style="text-align: left" class="c4"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">profile/bitset</code></td><td style="text-align: left"><code class="filename">profile/deque</code></td><td style="text-align: left"><code class="filename">profile/list</code></td><td style="text-align: left"><code class="filename">profile/map</code></td></tr><tr><td style="text-align: left"><code class="filename">profile/set</code></td><td style="text-align: left"><code class="filename">profile/unordered_map</code></td><td style="text-align: left"><code class="filename">profile/unordered_set</code></td><td style="text-align: left"><code class="filename">profile/vector</code></td></tr></tbody></table></div></div><br class="table-break"/><p/><div class="table"><a id="id468275"/><p class="title"><strong>Table 3.13. Extension Parallel Headers</strong></p><div class="table-contents"><table summary="Extension Parallel Headers" border="1"><colgroup><col style="text-align: left" class="c1"/><col style="text-align: left" class="c2"/></colgroup><tbody><tr><td style="text-align: left"><code class="filename">parallel/algorithm</code></td><td style="text-align: left"><code class="filename">parallel/numeric</code></td></tr></tbody></table></div></div><br class="table-break"/></div><div class="section" title="Mixing Headers"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.mixing"/>Mixing Headers</h3></div></div></div><p> A few simple rules.
</p><p>First, mixing different dialects of the standard headers is not
possible. It's an all-or-nothing affair. Thus, code like
</p><pre class="programlisting">
#include &lt;array&gt;
#include &lt;functional&gt;
</pre><p>Implies C++0x mode. To use the entities in &lt;array&gt;, the C++0x
compilation mode must be used, which implies the C++0x functionality
(and deprecations) in &lt;functional&gt; will be present.
</p><p>Second, the other headers can be included with either dialect of
the standard headers, although features and types specific to C++0x
are still only enabled when in C++0x compilation mode. So, to use
rvalue references with <code class="code">__gnu_cxx::vstring</code>, or to use the
debug-mode versions of <code class="code">std::unordered_map</code>, one must use
the <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++0x
facilities. It is possible (although not especially prudent) to
include both the TR1 version and the C++0x version of header in the
same translation unit:
</p><pre class="programlisting">
#include &lt;tr1/type_traits&gt;
#include &lt;type_traits&gt;
</pre><p> Several parts of C++0x diverge quite substantially from TR1 predecessors.
</p></div><div class="section" title="The C Headers and namespace std"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.cheaders"/>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
	(&lt;math.h&gt; in this case), the symbols will be available
	in the global namespace and perhaps in
	namespace <code class="code">std::</code> (but this is no longer a firm
	requirement.) On the other hand, including the C++-style
	header (&lt;cmath&gt;) guarantees that the entities will be
	found in namespace std and perhaps in the global namespace.
      </p><p>
Usage of C++-style headers is recommended, as then
C-linkage names can be disambiguated by explicit qualification, such
as by <code class="code">std::abort</code>. In addition, the C++-style headers can
use function overloading to provide a simpler interface to certain
families of C-functions. For instance in &lt;cmath&gt;, the
function <code class="code">std::sin</code> has overloads for all the builtin
floating-point types. This means that <code class="code">std::sin</code> can be
used uniformly, instead of a combination
of <code class="code">std::sinf</code>, <code class="code">std::sin</code>,
and <code class="code">std::sinl</code>.
</p></div><div class="section" title="Precompiled Headers"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.pre"/>Precompiled Headers</h3></div></div></div><p>There are three base header files that are provided. They can be
used to precompile the standard headers and extensions into binary
files that may the be used to speed compiles that use these headers.
</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>stdc++.h</p><p>Includes all standard headers. Actual content varies depending on
language dialect.
</p></li><li class="listitem"><p>stdtr1c++.h</p><p>Includes all of &lt;stdc++.h&gt;, and adds all the TR1 headers.
</p></li><li class="listitem"><p>extc++.h</p><p>Includes all of &lt;stdtr1c++.h&gt;, 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 do
this is:</p><pre class="programlisting">
g++ -v hello.cc

#include &lt;...&gt; 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 that
will 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 around
thirty 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> Detailed information about creating precompiled header files can be found in the GCC <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html">documentation</a>.
</p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="using.html">Prev</a> </td><td align="center"><a accesskey="u" href="using.html">Up</a></td><td align="right"> <a accesskey="n" href="using_macros.html">Next</a></td></tr><tr><td align="left" valign="top">Chapter 3. Using </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Macros</td></tr></table></div></body></html>