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_namespaces.html" title="Namespaces" /></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_namespaces.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 <ios>. Most of these macros 11 should not be used by consumers of libstdc++, and are reserved 12 for internal implementation use. <span class="emphasis"><em>These macros cannot 13 be redefined</em></span>. 14 </p><p> 15 A select handful of macros control libstdc++ extensions and extra 16 features, or provide versioning information for the API. Only 17 those macros listed below are offered for consideration by the 18 general public. 19 </p><p>Below is the macro which users may check for library version 20 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 21 libstdc++ in compressed ISO date format, form of an unsigned 22 long. For details on the value of this particular macro for a 23 particular release, please consult this <a class="link" href="abi.html" title="ABI Policy and Guidelines"> 24 document</a>. 25 </p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or 26 with -D/-U compiler flags. The default state of the symbol is 27 listed.</p><p><span class="quote">“<span class="quote">Configurable</span>”</span> (or <span class="quote">“<span class="quote">Not configurable</span>”</span>) means 28 that the symbol is initially chosen (or not) based on 29 --enable/--disable options at library build and configure time 30 (documented <a class="link" href="configure.html" title="Configure">here</a>), with the 31 various --enable/--disable choices being translated to 32 #define/#undef). 33 </p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may 34 mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, these 35 choices control code which has already been compiled (i.e., in a 36 binary such as libstdc++.a/.so). If you explicitly #define or 37 #undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code 38 paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not. 39 Experimenting with different values with the expectation of 40 consistent linkage requires changing the config headers before 41 building/installing the library. 42 </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p> 43 Defined by default. Not configurable. ABI-changing. Turning this off 44 removes older ARM-style iostreams code, and other anachronisms 45 from the API. This macro is dependent on the version of the 46 standard being tracked, and as a result may give different results for 47 <code class="code">-std=c++98</code> and <code class="code">-std=c++11</code>. This may 48 be useful in updating old C++ code which no longer meet the 49 requirements of the language, or for checking current code 50 against new language standards. 51 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p> 52 Undefined by default. Configurable via 53 <code class="code">--enable-concept-checks</code>. When defined, performs 54 compile-time checking on certain template instantiations to 55 detect violations of the requirements of the standard. This 56 is described in more detail <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">here</a>. 57 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p> 58 Undefined by default. When defined, compiles user code using 59 the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>. 60 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p> 61 Undefined by default. When defined while compiling with 62 the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>, makes 63 the debug mode extremely picky by making the use of libstdc++ 64 extensions and libstdc++-specific behavior into errors. 65 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 66 using the <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel 67 mode</a>. 68 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 69 using the <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">profile 70 mode</a>. 71 </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_namespaces.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"> Namespaces</td></tr></table></div></body></html>