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   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 &lt;ios&gt;. 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>