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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Macros</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.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 align="left"><a accesskey="p" href="using_headers.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td 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"><a id="manual.intro.using.macros"/>Macros</h2></div></div></div><p>
All library macros begin with <code class="code">_GLIBCXX_</code>.
</p><p>
Furthermore, all pre-processor macros, switches, and
configuration options are gathered in the
file <code class="filename">c++config.h</code>, which
is generated during the libstdc++ configuration and build
process. This file is then included when needed by files part of
the public libstdc++ API, like <ios>. Most of these macros
should not be used by consumers of libstdc++, and are reserved
for internal implementation use. <span class="emphasis"><em>These macros cannot
be redefined</em></span>.
</p><p>
A select handful of macros control libstdc++ extensions and extra
features, or provide versioning information for the API. Only
those macros listed below are offered for consideration by the
general public.
</p><p>Below is the macro which users may check for library version
information. </p><div class="variablelist"><dl><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The current version of
libstdc++ in compressed ISO date format, form of an unsigned
long. For details on the value of this particular macro for a
particular release, please consult this <a class="link" href="abi.html" title="ABI Policy and Guidelines">
document</a>.
</p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or
with -D/-U compiler flags. The default state of the symbol is
listed.</p><p><span class="quote">“<span class="quote">Configurable</span>”</span> (or <span class="quote">“<span class="quote">Not configurable</span>”</span>) means
that the symbol is initially chosen (or not) based on
--enable/--disable options at library build and configure time
(documented <a class="link" href="configure.html" title="Configure">here</a>), with the
various --enable/--disable choices being translated to
#define/#undef).
</p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may
mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, these
choices control code which has already been compiled (i.e., in a
binary such as libstdc++.a/.so). If you explicitly #define or
#undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code
paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not.
Experimenting with different values with the expectation of
consistent linkage requires changing the config headers before
building/installing the library.
</p><div class="variablelist"><dl><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p>
Defined by default. Not configurable. ABI-changing. Turning this off
removes older ARM-style iostreams code, and other anachronisms
from the API. This macro is dependent on the version of the
standard being tracked, and as a result may give different results for
<code class="code">-std=c++98</code> and <code class="code">-std=c++0x</code>. This may
be useful in updating old C++ code which no longer meet the
requirements of the language, or for checking current code
against new language standards.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_FORCE_NEW</code></span></dt><dd><p>
Undefined by default. When defined, memory allocation and
allocators controlled by libstdc++ call operator new/delete
without caching and pooling. Configurable via
<code class="code">--enable-libstdcxx-allocator</code>. ABI-changing.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p>
Undefined by default. Configurable via
<code class="code">--enable-concept-checks</code>. When defined, performs
compile-time checking on certain template instantiations to
detect violations of the requirements of the standard. This
is described in more detail <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">here</a>.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p>
Undefined by default. When defined, compiles user code using
the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p>
Undefined by default. When defined while compiling with
the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>, makes
the debug mode extremely picky by making the use of libstdc++
extensions and libstdc++-specific behavior into errors.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
using the <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel
mode</a>.
</p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
using the <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">profile
mode</a>.
</p></dd></dl></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="using_headers.html">Prev</a> </td><td align="center"><a accesskey="u" href="using.html">Up</a></td><td align="right"> <a accesskey="n" href="using_namespaces.html">Next</a></td></tr><tr><td align="left" valign="top">Headers </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Namespaces</td></tr></table></div></body></html>