1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!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 Vsnapshot" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.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 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="using_macros.html">Next</a></td></tr></table><hr /></div><div class="section"><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="section"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.headers.all"></a>Header Files</h3></div></div></div><p> 3 The C++ standard specifies the entire set of header files that 4 must be available to all hosted implementations. Actually, the 5 word "files" is a misnomer, since the contents of the 6 headers don't necessarily have to be in any kind of external 7 file. The only rule is that when one <code class="code">#include</code>s a 8 header, the contents of that header become available, no matter 9 how. 10 </p><p> 11 That said, in practice files are used. 12 </p><p> 13 There are two main types of include files: header files related 14 to a specific version of the ISO C++ standard (called Standard 15 Headers), and all others (TS, TR1, C++ ABI, and Extensions). 16 </p><p> 17 Multiple dialects of standard headers are supported, corresponding to 18 the 1998 standard as updated for 2003, the 2011 standard, the 2014 19 standard, and so on. 20 </p><p> 21 <a class="xref" href="using_headers.html#table.cxx98_headers" title="Table 3.2. C++ 1998 Library Headers">Table 3.2, “C++ 1998 Library Headers”</a> and 22 <a class="xref" href="using_headers.html#table.cxx98_cheaders" title="Table 3.3. C++ 1998 Library Headers for C Library Facilities">Table 3.3, “C++ 1998 Library Headers for C Library Facilities”</a> and 23 <a class="xref" href="using_headers.html#table.cxx98_deprheaders" title="Table 3.4. C++ 1998 Deprecated Library Header">Table 3.4, “C++ 1998 Deprecated Library Header”</a> 24 show the C++98/03 include files. 25 These are available in the C++98 compilation mode, 26 i.e. <code class="code">-std=c++98</code> or <code class="code">-std=gnu++98</code>. 27 Unless specified otherwise below, they are also available in later modes 28 (C++11, C++14 etc). 29 </p><div class="table"><a id="table.cxx98_headers"></a><p class="title"><strong>Table 3.2. C++ 1998 Library Headers</strong></p><div class="table-contents"><table class="table" summary="C++ 1998 Library Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">algorithm</code></td><td align="left"><code class="filename">bitset</code></td><td align="left"><code class="filename">complex</code></td><td align="left"><code class="filename">deque</code></td><td align="left"><code class="filename">exception</code></td></tr><tr><td align="left"><code class="filename">fstream</code></td><td align="left"><code class="filename">functional</code></td><td align="left"><code class="filename">iomanip</code></td><td align="left"><code class="filename">ios</code></td><td align="left"><code class="filename">iosfwd</code></td></tr><tr><td align="left"><code class="filename">iostream</code></td><td align="left"><code class="filename">istream</code></td><td align="left"><code class="filename">iterator</code></td><td align="left"><code class="filename">limits</code></td><td align="left"><code class="filename">list</code></td></tr><tr><td align="left"><code class="filename">locale</code></td><td align="left"><code class="filename">map</code></td><td align="left"><code class="filename">memory</code></td><td align="left"><code class="filename">new</code></td><td align="left"><code class="filename">numeric</code></td></tr><tr><td align="left"><code class="filename">ostream</code></td><td align="left"><code class="filename">queue</code></td><td align="left"><code class="filename">set</code></td><td align="left"><code class="filename">sstream</code></td><td align="left"><code class="filename">stack</code></td></tr><tr><td align="left"><code class="filename">stdexcept</code></td><td align="left"><code class="filename">streambuf</code></td><td align="left"><code class="filename">string</code></td><td align="left"><code class="filename">utility</code></td><td align="left"><code class="filename">typeinfo</code></td></tr><tr><td align="left"><code class="filename">valarray</code></td><td align="left"><code class="filename">vector</code></td><td colspan="3" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.cxx98_cheaders"></a><p class="title"><strong>Table 3.3. C++ 1998 Library Headers for C Library Facilities</strong></p><div class="table-contents"><table class="table" summary="C++ 1998 Library Headers for C Library Facilities" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">cassert</code></td><td align="left"><code class="filename">cerrno</code></td><td align="left"><code class="filename">cctype</code></td><td align="left"><code class="filename">cfloat</code></td><td align="left"><code class="filename">ciso646</code></td></tr><tr><td align="left"><code class="filename">climits</code></td><td align="left"><code class="filename">clocale</code></td><td align="left"><code class="filename">cmath</code></td><td align="left"><code class="filename">csetjmp</code></td><td align="left"><code class="filename">csignal</code></td></tr><tr><td align="left"><code class="filename">cstdarg</code></td><td align="left"><code class="filename">cstddef</code></td><td align="left"><code class="filename">cstdio</code></td><td align="left"><code class="filename">cstdlib</code></td><td align="left"><code class="filename">cstring</code></td></tr><tr><td align="left"><code class="filename">ctime</code></td><td align="left"><code class="filename">cwchar</code></td><td align="left"><code class="filename">cwctype</code></td><td colspan="2" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p> 30 The following header is deprecated 31 and might be removed from a future C++ standard. 32</p><div class="table"><a id="table.cxx98_deprheaders"></a><p class="title"><strong>Table 3.4. C++ 1998 Deprecated Library Header</strong></p><div class="table-contents"><table class="table" summary="C++ 1998 Deprecated Library Header" border="1"><colgroup><col align="left" class="c1" /></colgroup><tbody><tr><td align="left"><code class="filename">strstream</code></td></tr></tbody></table></div></div><br class="table-break" /><p> 33<a class="xref" href="using_headers.html#table.cxx11_headers" title="Table 3.5. C++ 2011 Library Headers">Table 3.5, “C++ 2011 Library Headers”</a> and 34<a class="xref" href="using_headers.html#table.cxx11_cheaders" title="Table 3.6. C++ 2011 Library Headers for C Library Facilities">Table 3.6, “C++ 2011 Library Headers for C Library Facilities”</a> show the C++11 include files. 35These are available in C++11 compilation 36mode, i.e. <code class="literal">-std=c++11</code> or <code class="literal">-std=gnu++11</code>. 37Including these headers in C++98/03 mode may result in compilation errors. 38Unless specified otherwise below, they are also available in later modes 39(C++14 etc). 40</p><p></p><div class="table"><a id="table.cxx11_headers"></a><p class="title"><strong>Table 3.5. C++ 2011 Library Headers</strong></p><div class="table-contents"><table class="table" summary="C++ 2011 Library Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">array</code></td><td align="left"><code class="filename">atomic</code></td><td align="left"><code class="filename">chrono</code></td><td align="left"><code class="filename">codecvt</code></td><td align="left"><code class="filename">condition_variable</code></td></tr><tr><td align="left"><code class="filename">forward_list</code></td><td align="left"><code class="filename">future</code></td><td align="left"><code class="filename">initalizer_list</code></td><td align="left"><code class="filename">mutex</code></td><td align="left"><code class="filename">random</code></td></tr><tr><td align="left"><code class="filename">ratio</code></td><td align="left"><code class="filename">regex</code></td><td align="left"><code class="filename">scoped_allocator</code></td><td align="left"><code class="filename">system_error</code></td><td align="left"><code class="filename">thread</code></td></tr><tr><td align="left"><code class="filename">tuple</code></td><td align="left"><code class="filename">typeindex</code></td><td align="left"><code class="filename">type_traits</code></td><td align="left"><code class="filename">unordered_map</code></td><td align="left"><code class="filename">unordered_set</code></td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.cxx11_cheaders"></a><p class="title"><strong>Table 3.6. C++ 2011 Library Headers for C Library Facilities</strong></p><div class="table-contents"><table class="table" summary="C++ 2011 Library Headers for C Library Facilities" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">ccomplex</code></td><td align="left"><code class="filename">cfenv</code></td><td align="left"><code class="filename">cinttypes</code></td><td align="left"><code class="filename">cstdalign</code></td><td align="left"><code class="filename">cstdbool</code></td></tr><tr><td align="left"><code class="filename">cstdint</code></td><td align="left"><code class="filename">ctgmath</code></td><td align="left"><code class="filename">cuchar</code></td><td colspan="2" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p> 41<a class="xref" href="using_headers.html#table.cxx14_headers" title="Table 3.7. C++ 2014 Library Header">Table 3.7, “C++ 2014 Library Header”</a> shows the C++14 include file. 42This is available in C++14 compilation 43mode, i.e. <code class="literal">-std=c++14</code> or <code class="literal">-std=gnu++14</code>. 44Including this header in C++98/03 mode or C++11 will not result in 45compilation errors, but will not define anything. 46Unless specified otherwise below, it is also available in later modes 47(C++17 etc). 48</p><p></p><div class="table"><a id="table.cxx14_headers"></a><p class="title"><strong>Table 3.7. C++ 2014 Library Header</strong></p><div class="table-contents"><table class="table" summary="C++ 2014 Library Header" border="1"><colgroup><col align="left" class="c1" /></colgroup><tbody><tr><td align="left"><code class="filename">shared_mutex</code></td></tr></tbody></table></div></div><br class="table-break" /><p> 49<a class="xref" href="using_headers.html#table.filesystemts_headers" title="Table 3.8. File System TS Header">Table 3.8, “File System TS Header”</a>, 50shows the additional include file define by the 51File System Technical Specification, ISO/IEC TS 18822. 52This is available in C++11 and later compilation modes. 53Including this header in earlier modes will not result in 54compilation errors, but will not define anything. 55</p><p></p><div class="table"><a id="table.filesystemts_headers"></a><p class="title"><strong>Table 3.8. File System TS Header</strong></p><div class="table-contents"><table class="table" summary="File System TS Header" border="1"><colgroup><col align="left" class="c1" /></colgroup><tbody><tr><td align="left"><code class="filename">experimental/filesystem</code></td></tr></tbody></table></div></div><br class="table-break" /><p> 56<a class="xref" href="using_headers.html#table.libfundts_headers" title="Table 3.9. Library Fundamentals TS Headers">Table 3.9, “Library Fundamentals TS Headers”</a>, 57shows the additional include files define by the C++ Extensions for 58Library Fundamentals Technical Specification, ISO/IEC TS 19568. 59These are available in C++14 and later compilation modes. 60Including these headers in earlier modes will not result in 61compilation errors, but will not define anything. 62</p><p></p><div class="table"><a id="table.libfundts_headers"></a><p class="title"><strong>Table 3.9. Library Fundamentals TS Headers</strong></p><div class="table-contents"><table class="table" summary="Library Fundamentals TS Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">experimental/algorithm</code></td><td align="left"><code class="filename">experimental/any</code></td><td align="left"><code class="filename">experimental/array</code></td><td align="left"><code class="filename">experimental/chrono</code></td><td align="left"><code class="filename">experimental/deque</code></td></tr><tr><td align="left"><code class="filename">experimental/forward_list</code></td><td align="left"><code class="filename">experimental/functional</code></td><td align="left"><code class="filename">experimental/iterator</code></td><td align="left"><code class="filename">experimental/list</code></td><td align="left"><code class="filename">experimental/map</code></td></tr><tr><td align="left"><code class="filename">experimental/memory</code></td><td align="left"><code class="filename">experimental/memory_resource</code></td><td align="left"><code class="filename">experimental/numeric</code></td><td align="left"><code class="filename">experimental/optional</code></td><td align="left"><code class="filename">experimental/propagate_const</code></td></tr><tr><td align="left"><code class="filename">experimental/random</code></td><td align="left"><code class="filename">experimental/ratio</code></td><td align="left"><code class="filename">experimental/regex</code></td><td align="left"><code class="filename">experimental/set</code></td><td align="left"><code class="filename">experimental/string</code></td></tr><tr><td align="left"><code class="filename">experimental/string_view</code></td><td align="left"><code class="filename">experimental/system_error</code></td><td align="left"><code class="filename">experimental/tuple</code></td><td align="left"><code class="filename">experimental/type_traits</code></td><td align="left"><code class="filename">experimental/unordered_map</code></td></tr><tr><td align="left"><code class="filename">experimental/unordered_set</code></td><td align="left"><code class="filename">experimental/utility</code></td><td align="left"><code class="filename">experimental/vector</code></td><td colspan="2" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p> 63 In addition, TR1 includes as: 64</p><div class="table"><a id="table.tr1_headers"></a><p class="title"><strong>Table 3.10. C++ TR 1 Library Headers</strong></p><div class="table-contents"><table class="table" summary="C++ TR 1 Library Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">tr1/array</code></td><td align="left"><code class="filename">tr1/complex</code></td><td align="left"><code class="filename">tr1/memory</code></td><td align="left"><code class="filename">tr1/functional</code></td><td align="left"><code class="filename">tr1/random</code></td></tr><tr><td align="left"><code class="filename">tr1/regex</code></td><td align="left"><code class="filename">tr1/tuple</code></td><td align="left"><code class="filename">tr1/type_traits</code></td><td align="left"><code class="filename">tr1/unordered_map</code></td><td align="left"><code class="filename">tr1/unordered_set</code></td></tr><tr><td align="left"><code class="filename">tr1/utility</code></td><td colspan="4" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.tr1_cheaders"></a><p class="title"><strong>Table 3.11. C++ TR 1 Library Headers for C Library Facilities</strong></p><div class="table-contents"><table class="table" summary="C++ TR 1 Library Headers for C Library Facilities" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">tr1/ccomplex</code></td><td align="left"><code class="filename">tr1/cfenv</code></td><td align="left"><code class="filename">tr1/cfloat</code></td><td align="left"><code class="filename">tr1/cmath</code></td><td align="left"><code class="filename">tr1/cinttypes</code></td></tr><tr><td align="left"><code class="filename">tr1/climits</code></td><td align="left"><code class="filename">tr1/cstdarg</code></td><td align="left"><code class="filename">tr1/cstdbool</code></td><td align="left"><code class="filename">tr1/cstdint</code></td><td align="left"><code class="filename">tr1/cstdio</code></td></tr><tr><td align="left"><code class="filename">tr1/cstdlib</code></td><td align="left"><code class="filename">tr1/ctgmath</code></td><td align="left"><code class="filename">tr1/ctime</code></td><td align="left"><code class="filename">tr1/cwchar</code></td><td 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++ 65compiler supports scalar decimal floating-point types defined via 66<code class="code">__attribute__((mode(SD|DD|LD)))</code>. 67</p><div class="table"><a id="table.decfp_headers"></a><p class="title"><strong>Table 3.12. C++ TR 24733 Decimal Floating-Point Header</strong></p><div class="table-contents"><table class="table" summary="C++ TR 24733 Decimal Floating-Point Header" border="1"><colgroup><col align="left" class="c1" /></colgroup><tbody><tr><td align="left"><code class="filename">decimal/decimal</code></td></tr></tbody></table></div></div><br class="table-break" /><p> 68 Also included are files for the C++ ABI interface: 69</p><div class="table"><a id="table.abi_headers"></a><p class="title"><strong>Table 3.13. C++ ABI Headers</strong></p><div class="table-contents"><table class="table" summary="C++ ABI Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></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> 70 And a large variety of extensions. 71</p><div class="table"><a id="table.ext_headers"></a><p class="title"><strong>Table 3.14. Extension Headers</strong></p><div class="table-contents"><table class="table" summary="Extension Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">ext/algorithm</code></td><td align="left"><code class="filename">ext/atomicity.h</code></td><td align="left"><code class="filename">ext/array_allocator.h</code></td><td align="left"><code class="filename">ext/bitmap_allocator.h</code></td><td align="left"><code class="filename">ext/cast.h</code></td></tr><tr><td align="left"><code class="filename">ext/codecvt_specializations.h</code></td><td align="left"><code class="filename">ext/concurrence.h</code></td><td align="left"><code class="filename">ext/debug_allocator.h</code></td><td align="left"><code class="filename">ext/enc_filebuf.h</code></td><td align="left"><code class="filename">ext/extptr_allocator.h</code></td></tr><tr><td align="left"><code class="filename">ext/functional</code></td><td align="left"><code class="filename">ext/iterator</code></td><td align="left"><code class="filename">ext/malloc_allocator.h</code></td><td align="left"><code class="filename">ext/memory</code></td><td align="left"><code class="filename">ext/mt_allocator.h</code></td></tr><tr><td align="left"><code class="filename">ext/new_allocator.h</code></td><td align="left"><code class="filename">ext/numeric</code></td><td align="left"><code class="filename">ext/numeric_traits.h</code></td><td align="left"><code class="filename">ext/pb_ds/assoc_container.h</code></td><td align="left"><code class="filename">ext/pb_ds/priority_queue.h</code></td></tr><tr><td align="left"><code class="filename">ext/pod_char_traits.h</code></td><td align="left"><code class="filename">ext/pool_allocator.h</code></td><td align="left"><code class="filename">ext/rb_tree</code></td><td align="left"><code class="filename">ext/rope</code></td><td align="left"><code class="filename">ext/slist</code></td></tr><tr><td align="left"><code class="filename">ext/stdio_filebuf.h</code></td><td align="left"><code class="filename">ext/stdio_sync_filebuf.h</code></td><td align="left"><code class="filename">ext/throw_allocator.h</code></td><td align="left"><code class="filename">ext/typelist.h</code></td><td align="left"><code class="filename">ext/type_traits.h</code></td></tr><tr><td align="left"><code class="filename">ext/vstring.h</code></td><td colspan="4" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.debug_headers"></a><p class="title"><strong>Table 3.15. Extension Debug Headers</strong></p><div class="table-contents"><table class="table" summary="Extension Debug Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /><col align="left" class="c5" /></colgroup><tbody><tr><td align="left"><code class="filename">debug/array</code></td><td align="left"><code class="filename">debug/bitset</code></td><td align="left"><code class="filename">debug/deque</code></td><td align="left"><code class="filename">debug/forward_list</code></td><td align="left"><code class="filename">debug/list</code></td></tr><tr><td align="left"><code class="filename">debug/map</code></td><td align="left"><code class="filename">debug/set</code></td><td align="left"><code class="filename">debug/string</code></td><td align="left"><code class="filename">debug/unordered_map</code></td><td align="left"><code class="filename">debug/unordered_set</code></td></tr><tr><td align="left"><code class="filename">debug/vector</code></td><td colspan="4" align="left"> </td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.profile_headers"></a><p class="title"><strong>Table 3.16. Extension Profile Headers</strong></p><div class="table-contents"><table class="table" summary="Extension Profile Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /><col align="left" class="c3" /><col align="left" class="c4" /></colgroup><tbody><tr><td align="left"><code class="filename">profile/bitset</code></td><td align="left"><code class="filename">profile/deque</code></td><td align="left"><code class="filename">profile/list</code></td><td align="left"><code class="filename">profile/map</code></td></tr><tr><td align="left"><code class="filename">profile/set</code></td><td align="left"><code class="filename">profile/unordered_map</code></td><td align="left"><code class="filename">profile/unordered_set</code></td><td align="left"><code class="filename">profile/vector</code></td></tr></tbody></table></div></div><br class="table-break" /><p></p><div class="table"><a id="table.parallel_headers"></a><p class="title"><strong>Table 3.17. Extension Parallel Headers</strong></p><div class="table-contents"><table class="table" summary="Extension Parallel Headers" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></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="section"><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. 72</p><p>First, mixing different dialects of the standard headers is not 73possible. It's an all-or-nothing affair. Thus, code like 74</p><pre class="programlisting"> 75#include <array> 76#include <functional> 77</pre><p>Implies C++11 mode. To use the entities in <array>, the C++11 78compilation mode must be used, which implies the C++11 functionality 79(and deprecations) in <functional> will be present. 80</p><p>Second, the other headers can be included with either dialect of 81the standard headers, although features and types specific to C++11 82are still only enabled when in C++11 compilation mode. So, to use 83rvalue references with <code class="code">__gnu_cxx::vstring</code>, or to use the 84debug-mode versions of <code class="code">std::unordered_map</code>, one must use 85the <code class="code">std=gnu++11</code> compiler flag. (Or <code class="code">std=c++11</code>, of course.) 86</p><p>A special case of the second rule is the mixing of TR1 and C++11 87facilities. It is possible (although not especially prudent) to 88include both the TR1 version and the C++11 version of header in the 89same translation unit: 90</p><pre class="programlisting"> 91#include <tr1/type_traits> 92#include <type_traits> 93</pre><p> Several parts of C++11 diverge quite substantially from TR1 predecessors. 94</p></div><div class="section"><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> 95 The standard specifies that if one includes the C-style header 96 (<math.h> in this case), the symbols will be available 97 in the global namespace and perhaps in 98 namespace <code class="code">std::</code> (but this is no longer a firm 99 requirement.) On the other hand, including the C++-style 100 header (<cmath>) guarantees that the entities will be 101 found in namespace std and perhaps in the global namespace. 102 </p><p> 103Usage of C++-style headers is recommended, as then 104C-linkage names can be disambiguated by explicit qualification, such 105as by <code class="code">std::abort</code>. In addition, the C++-style headers can 106use function overloading to provide a simpler interface to certain 107families of C-functions. For instance in <cmath>, the 108function <code class="code">std::sin</code> has overloads for all the builtin 109floating-point types. This means that <code class="code">std::sin</code> can be 110used uniformly, instead of a combination 111of <code class="code">std::sinf</code>, <code class="code">std::sin</code>, 112and <code class="code">std::sinl</code>. 113</p></div><div class="section"><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 be 114used to precompile the standard headers and extensions into binary 115files that may then be used to speed up compilations that use these headers. 116</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>stdc++.h</p><p>Includes all standard headers. Actual content varies depending on 117<a class="link" href="using.html#manual.intro.using.flags" title="Command Options">language dialect</a>. 118</p></li><li class="listitem"><p>stdtr1c++.h</p><p>Includes all of <stdc++.h>, and adds all the TR1 headers. 119</p></li><li class="listitem"><p>extc++.h</p><p>Includes all of <stdc++.h>, and adds all the Extension headers 120(and in C++98 mode also adds all the TR1 headers by including all of 121<stdtr1c++.h>). 122</p></li></ul></div><p>To construct a .gch file from one of these base header files, 123first find the include directory for the compiler. One way to do 124this is:</p><pre class="programlisting"> 125g++ -v hello.cc 126 127#include <...> search starts here: 128 /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0 129... 130End of search list. 131</pre><p>Then, create a precompiled header file with the same flags that 132will be used to compile other projects.</p><pre class="programlisting"> 133g++ -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 134</pre><p>The resulting file will be quite large: the current size is around 135thirty megabytes. </p><p>How to use the resulting file.</p><pre class="programlisting"> 136g++ -I. -include stdc++.h -H -g -O2 hello.cc 137</pre><p>Verification that the PCH file is being used is easy:</p><pre class="programlisting"> 138g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe 139! ./stdc++.h.gch 140. /mnt/share/bld/H-x86-gcc.20071201/include/c++/4.3.0/iostream 141. /mnt/share/bld/H-x86-gcc.20071201include/c++/4.3.0/string 142</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.</p><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" target="_top">documentation</a>. 143</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="using_macros.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 3. 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