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-NS Stylesheets V1.78.1" /><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 is the macro which users may check for library version 21 information. </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The current version of 22 libstdc++ in compressed ISO date format, as an unsigned 23 long. For details on the value of this particular macro for a 24 particular release, please consult the <a class="link" href="abi.html" title="ABI Policy and Guidelines"> 25 ABI Policy and Guidelines</a> appendix. 26 </p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or 27 with -D/-U compiler flags. The default state of the symbol is 28 listed.</p><p><span class="quote">“<span class="quote">Configurable</span>”</span> (or <span class="quote">“<span class="quote">Not configurable</span>”</span>) means 29 that the symbol is initially chosen (or not) based on 30 --enable/--disable options at library build and configure time 31 (documented in 32 <a class="link" href="configure.html" title="Configure">Configure</a>), 33 with the various --enable/--disable choices being translated to 34 #define/#undef). 35 </p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may 36 mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, 37 these choices control code which has already been compiled (i.e., in a 38 binary such as libstdc++.a/.so). If you explicitly #define or 39 #undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code 40 paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not. 41 Experimenting with different values with the expectation of 42 consistent linkage requires changing the config headers before 43 building/installing the library. 44 </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p> 45 Defined by default. Not configurable. ABI-changing. Turning this off 46 removes older ARM-style iostreams code, and other anachronisms 47 from the API. This macro is dependent on the version of the 48 standard being tracked, and as a result may give different results for 49 <code class="code">-std=c++98</code> and <code class="code">-std=c++11</code>. This may 50 be useful in updating old C++ code which no longer meet the 51 requirements of the language, or for checking current code 52 against new language standards. 53 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_USE_CXX11_ABI</code></span></dt><dd><p> 54 Defined to the value <code class="literal">1</code> by default. 55 Configurable via <code class="code">--disable-libstdcxx-dual-abi</code> 56 and/or <code class="code">--with-default-libstdcxx-abi</code>. 57 ABI-changing. 58 When defined to a non-zero value the library headers will use the 59 new C++11-conforming ABI introduced in GCC 5, rather than the older 60 ABI introduced in GCC 3.4. This changes the definition of several 61 class templates, including <code class="classname">std:string</code>, 62 <code class="classname">std::list</code> and some locale facets. 63 For more details see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>. 64 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p> 65 Undefined by default. Configurable via 66 <code class="code">--enable-concept-checks</code>. When defined, performs 67 compile-time checking on certain template instantiations to 68 detect violations of the requirements of the standard. This 69 is described in more detail in 70 <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">Compile Time Checks</a>. 71 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p> 72 Undefined by default. When defined, compiles user code using 73 the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>. 74 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p> 75 Undefined by default. When defined while compiling with 76 the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>, makes 77 the debug mode extremely picky by making the use of libstdc++ 78 extensions and libstdc++-specific behavior into errors. 79 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 80 using the <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel 81 mode</a>. 82 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 83 using the <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">profile 84 mode</a>. 85 </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>