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"> 3<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 V1.75.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><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="sect1" title="Macros"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.macros"></a>Macros</h2></div></div></div><p> 4 All library macros begin with <code class="code">_GLIBCXX_</code>. 5 </p><p> 6 Furthermore, all pre-processor macros, switches, and 7 configuration options are gathered in the 8 file <code class="filename">c++config.h</code>, which 9 is generated during the libstdc++ configuration and build 10 process. This file is then included when needed by files part of 11 the public libstdc++ API, like <ios>. Most of these macros 12 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><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The current version of 22 libstdc++ in compressed ISO date format, form of an unsigned 23 long. For details on the value of this particular macro for a 24 particular release, please consult this <a class="link" href="abi.html" title="ABI Policy and Guidelines"> 25 document</a>. 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 <a class="link" href="configure.html" title="Configure">here</a>), with the 32 various --enable/--disable choices being translated to 33 #define/#undef). 34 </p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may 35 mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, these 36 choices control code which has already been compiled (i.e., in a 37 binary such as libstdc++.a/.so). If you explicitly #define or 38 #undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code 39 paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not. 40 Experimenting with different values with the expectation of 41 consistent linkage requires changing the config headers before 42 building/installing the library. 43 </p><div class="variablelist"><dl><dt><span class="term"><code class="code">_GLIBCXX_DEPRECATED</code></span></dt><dd><p> 44 Defined by default. Not configurable. ABI-changing. Turning this off 45 removes older ARM-style iostreams code, and other anachronisms 46 from the API. This macro is dependent on the version of the 47 standard being tracked, and as a result may give different results for 48 <code class="code">-std=c++98</code> and <code class="code">-std=c++0x</code>. This may 49 be useful in updating old C++ code which no longer meet the 50 requirements of the language, or for checking current code 51 against new language standards. 52 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_FORCE_NEW</code></span></dt><dd><p> 53 Undefined by default. When defined, memory allocation and 54 allocators controlled by libstdc++ call operator new/delete 55 without caching and pooling. Configurable via 56 <code class="code">--enable-libstdcxx-allocator</code>. ABI-changing. 57 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p> 58 Undefined by default. Configurable via 59 <code class="code">--enable-concept-checks</code>. When defined, performs 60 compile-time checking on certain template instantiations to 61 detect violations of the requirements of the standard. This 62 is described in more detail <a class="link" href="ext_compile_checks.html" title="Chapter 29. Compile Time Checks">here</a>. 63 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p> 64 Undefined by default. When defined, compiles user code using 65 the <a class="link" href="debug_mode.html" title="Chapter 30. Debug Mode">debug mode</a>. 66 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p> 67 Undefined by default. When defined while compiling with 68 the <a class="link" href="debug_mode.html" title="Chapter 30. Debug Mode">debug mode</a>, makes 69 the debug mode extremely picky by making the use of libstdc++ 70 extensions and libstdc++-specific behavior into errors. 71 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 72 using the <a class="link" href="parallel_mode.html" title="Chapter 31. Parallel Mode">parallel 73 mode</a>. 74 </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code 75 using the <a class="link" href="profile_mode.html" title="Chapter 32. Profile Mode">profile 76 mode</a>. 77 </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="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Namespaces</td></tr></table></div></body></html> 78