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  11     "><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 bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><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" title="Macros"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="manual.intro.using.macros"></a>Macros</h2></div></div></div><p>
  12      All library macros begin with <code class="code">_GLIBCXX_</code>.
  13    </p><p>
  14      Furthermore, all pre-processor macros, switches, and
  15       configuration options are gathered in the
  16       file <code class="filename">c++config.h</code>, which
  17       is generated during the libstdc++ configuration and build
  18       process. This file is then included when needed by files part of
  19       the public libstdc++ API, like &lt;ios&gt;. Most of these macros
  20       should not be used by consumers of libstdc++, and are reserved
  21       for internal implementation use. <span class="emphasis"><em>These macros cannot
  22       be redefined</em></span>.
  23    </p><p>
  24      A select handful of macros control libstdc++ extensions and extra
  25       features, or provide versioning information for the API.  Only
  26       those macros listed below are offered for consideration by the
  27       general public.
  28    </p><p>Below is the macro which users may check for library version
  29       information. </p><div class="variablelist"><dl><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The current version of
  30     libstdc++ in compressed ISO date format, form of an unsigned
  31     long. For details on the value of this particular macro for a
  32     particular release, please consult this <a class="link" href="abi.html" title="ABI Policy and Guidelines">
  33     document</a>.
  34     </p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or
  35       with -D/-U compiler flags.  The default state of the symbol is
  36       listed.</p><p><span class="quote">“<span class="quote">Configurable</span>”</span> (or <span class="quote">“<span class="quote">Not configurable</span>”</span>) means
  37       that the symbol is initially chosen (or not) based on
  38       --enable/--disable options at library build and configure time
  39       (documented <a class="link" href="configure.html" title="Configure">here</a>), with the
  40       various --enable/--disable choices being translated to
  41       #define/#undef).
  42    </p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may
  43   mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, these
  44   choices control code which has already been compiled (i.e., in a
  45   binary such as libstdc++.a/.so).  If you explicitly #define or
  46   #undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code
  47   paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not.
  48   Experimenting with different values with the expectation of
  49   consistent linkage requires changing the config headers before
  50   building/installing the library.
  51    </p><div class="variablelist"><dl><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p>
  52         Defined by default. Not configurable. ABI-changing. Turning this off
  53         removes older ARM-style iostreams code, and other anachronisms
  54         from the API.  This macro is dependent on the version of the
  55         standard being tracked, and as a result may give different results for
  56         <code class="code">-std=c++98</code> and <code class="code">-std=c++11</code>. This may
  57         be useful in updating old C++ code which no longer meet the
  58         requirements of the language, or for checking current code
  59         against new language standards.
  60     </p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p>
  61         Undefined by default.  Configurable via
  62         <code class="code">--enable-concept-checks</code>.  When defined, performs
  63         compile-time checking on certain template instantiations to
  64         detect violations of the requirements of the standard.  This
  65         is described in more detail <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">here</a>.
  66       </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p>
  67         Undefined by default. When defined, compiles user code using
  68     the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>.
  69       </p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p>
  70         Undefined by default. When defined while compiling with
  71     the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>, makes
  72     the debug mode extremely picky by making the use of libstdc++
  73     extensions and libstdc++-specific behavior into errors.
  74       </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
  75     using the <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel
  76     mode</a>.
  77       </p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
  78     using the <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">profile
  79     mode</a>.
  80       </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>