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>Macros</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_headers.html" title="Headers" /><link rel="next" href="using_dual_abi.html" title="Dual ABI" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Macros</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using_headers.html">Prev</a>��</td><th width="60%" align="center">Chapter��3.��Using</th><td width="20%" align="right">��<a accesskey="n" href="using_dual_abi.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.macros"></a>Macros</h2></div></div></div><p> 3 All library macros begin with <code class="code">_GLIBCXX_</code>. 4 </p><p> 5 Furthermore, all pre-processor macros, switches, and 6 configuration options are gathered in the 7 file <code class="filename">c++config.h</code>, which 8 is generated during the libstdc++ configuration and build 9 process. This file is then included when needed by files part of 10 the public libstdc++ API, like 11 <code class="filename"><ios></code>. Most of these 12 macros should not be used by consumers of libstdc++, and are reserved 13 for internal implementation use. <span class="emphasis"><em>These macros cannot 14 be redefined</em></span>. 15 </p><p> 16 A select handful of macros control libstdc++ extensions and extra 17 features, or provide versioning information for the API. Only 18 those macros listed below are offered for consideration by the 19 general public. 20 </p><p>Below are the macros which users may check for library version 21 information. </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">_GLIBCXX_RELEASE</code></span></dt><dd><p>The major release number for libstdc++. This macro is defined 22 to the GCC major version that the libstdc++ headers belong to, 23 as an integer constant. 24 When compiling with GCC it has the same value as GCC's pre-defined 25 macro <span class="symbol">__GNUC__</span>. 26 This macro can be used when libstdc++ is used with a non-GNU 27 compiler where <span class="symbol">__GNUC__</span> is not defined, or has a 28 different value that doesn't correspond to the libstdc++ version. 29 This macro first appeared in the GCC 7.1 release and is not defined 30 for GCC 6.x or older releases. 31 </p></dd><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The revision date of the libstdc++ source code, 32 in compressed ISO date format, as an unsigned 33 long. For notes about using this macro and details on the value of 34 this macro for a particular release, please consult the 35 <a class="link" href="abi.html#abi.versioning.__GLIBCXX__">ABI History</a> 36 appendix. 37 </p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or 38 with -D/-U compiler flags. The default state of the symbol is 39 listed.</p><p><span class="quote">���<span class="quote">Configurable</span>���</span> (or <span class="quote">���<span class="quote">Not configurable</span>���</span>) means 40 that the symbol is initially chosen (or not) based on 41 --enable/--disable options at library build and configure time 42 (documented in 43 <a class="link" href="configure.html" title="Configure">Configure</a>), 44 with the various --enable/--disable choices being translated to 45 #define/#undef). 46 </p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may 47 mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, 48 these choices control code which has already been compiled (i.e., in a 49 binary such as libstdc++.a/.so). If you explicitly #define or 50 #undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code 51 paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not. 52 Experimenting with different values with the expectation of 53 consistent linkage requires changing the config headers before 54 building/installing the library. 55 </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p> 56 Defined by default. Not configurable. ABI-changing. Turning this off 57 removes older ARM-style iostreams code, and other anachronisms 58 from the API. This macro is dependent on the version of the 59 standard being tracked, and as a result may give different results for 60 <code class="code">-std=c++98</code> and <code class="code">-std=c++11</code>. This may 61 be useful in updating old C++ code which no longer meet the 62 requirements of the language, or for checking current code 63 against new language standards. 64 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_USE_CXX11_ABI</code></span></dt><dd><p> 65 Defined to the value <code class="literal">1</code> by default. 66 Configurable via <code class="code">--disable-libstdcxx-dual-abi</code> 67 and/or <code class="code">--with-default-libstdcxx-abi</code>. 68 ABI-changing. 69 When defined to a non-zero value the library headers will use the 70 new C++11-conforming ABI introduced in GCC 5, rather than the older 71 ABI introduced in GCC 3.4. This changes the definition of several 72 class templates, including <code class="classname">std:string</code>, 73 <code class="classname">std::list</code> and some locale facets. 74 For more details see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>. 75 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p> 76 Undefined by default. Configurable via 77 <code class="code">--enable-concept-checks</code>. When defined, performs 78 compile-time checking on certain template instantiations to 79 detect violations of the requirements of the standard. This 80 macro has no effect for freestanding implementations. 81 This is described in more detail in 82 <a class="link" href="ext_compile_checks.html" title="Chapter��16.��Compile Time Checks">Compile Time Checks</a>. 83 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_ASSERTIONS</code></span></dt><dd><p> 84 Undefined by default. When defined, enables extra error checking in 85 the form of precondition assertions, such as bounds checking in 86 strings and null pointer checks when dereferencing smart pointers. 87 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p> 88 Undefined by default. When defined, compiles user code using 89 the <a class="link" href="debug_mode.html" title="Chapter��17.��Debug Mode">debug mode</a>. 90 When defined, <code class="code">_GLIBCXX_ASSERTIONS</code> is defined 91 automatically, so all the assertions enabled by that macro are also 92 enabled in debug mode. 93 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p> 94 Undefined by default. When defined while compiling with 95 the <a class="link" href="debug_mode.html" title="Chapter��17.��Debug Mode">debug mode</a>, makes 96 the debug mode extremely picky by making the use of libstdc++ 97 extensions and libstdc++-specific behavior into errors. 98 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 99 using the <a class="link" href="parallel_mode.html" title="Chapter��18.��Parallel Mode">parallel 100 mode</a>. 101 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL_ASSERTIONS</code></span></dt><dd><p>Undefined by default, but when any parallel mode header is included 102 this macro will be defined to a non-zero value if 103 <code class="code">_GLIBCXX_ASSERTIONS</code> has a non-zero value, otherwise to zero. 104 When defined to a non-zero value, it enables extra error checking and 105 assertions in the parallel mode. 106 </p></dd><dt><span class="term"><code class="code">__STDCPP_WANT_MATH_SPEC_FUNCS__</code></span></dt><dd><p>Undefined by default. When defined to a non-zero integer constant, 107 enables support for ISO/IEC 29124 Special Math Functions. 108 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_SANITIZE_VECTOR</code></span></dt><dd><p> 109 Undefined by default. When defined, <code class="classname">std::vector</code> 110 operations will be annotated so that AddressSanitizer can detect 111 invalid accesses to the unused capacity of a 112 <code class="classname">std::vector</code>. These annotations are only 113 enabled for 114 <code class="classname">std::vector<T, std::allocator<T>></code> 115 and only when <code class="classname">std::allocator</code> is derived from 116 <a class="link" href="memory.html#allocator.ext" title="Extension Allocators"><code class="classname">new_allocator</code> 117 or <code class="classname">malloc_allocator</code></a>. The annotations 118 must be present on all vector operations or none, so this macro must 119 be defined to the same value for all translation units that create, 120 destroy or modify vectors. 121 </p></dd></dl></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using_headers.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_dual_abi.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Headers��</td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top">��Dual ABI</td></tr></table></div></body></html>