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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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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 "/><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 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>
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All library macros begin with <code class="code">_GLIBCXX_</code>.
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</p><p>
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Furthermore, all pre-processor macros, switches, and
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configuration options are gathered in the
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file <code class="filename">c++config.h</code>, which
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is generated during the libstdc++ configuration and build
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process. This file is then included when needed by files part of
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the public libstdc++ API, like <ios>. Most of these macros
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should not be used by consumers of libstdc++, and are reserved
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for internal implementation use. <span class="emphasis"><em>These macros cannot
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be redefined</em></span>.
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</p><p>
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A select handful of macros control libstdc++ extensions and extra
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features, or provide versioning information for the API. Only
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those macros listed below are offered for consideration by the
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general public.
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</p><p>Below is the macro which users may check for library version
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information. </p><div class="variablelist"><dl><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The current version of
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libstdc++ in compressed ISO date format, form of an unsigned
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long. For details on the value of this particular macro for a
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particular release, please consult this <a class="link" href="abi.html" title="ABI Policy and Guidelines">
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document</a>.
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</p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or
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with -D/-U compiler flags. The default state of the symbol is
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listed.</p><p><span class="quote">“<span class="quote">Configurable</span>”</span> (or <span class="quote">“<span class="quote">Not configurable</span>”</span>) means
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that the symbol is initially chosen (or not) based on
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--enable/--disable options at library build and configure time
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(documented <a class="link" href="configure.html" title="Configure">here</a>), with the
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various --enable/--disable choices being translated to
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#define/#undef).
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</p><p> <acronym class="acronym">ABI</acronym> means that changing from the default value may
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mean changing the <acronym class="acronym">ABI</acronym> of compiled code. In other words, these
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choices control code which has already been compiled (i.e., in a
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binary such as libstdc++.a/.so). If you explicitly #define or
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#undef these macros, the <span class="emphasis"><em>headers</em></span> may see different code
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paths, but the <span class="emphasis"><em>libraries</em></span> which you link against will not.
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Experimenting with different values with the expectation of
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consistent linkage requires changing the config headers before
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building/installing the library.
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</p><div class="variablelist"><dl><dt><span class="term"><code class="code">_GLIBCXX_USE_DEPRECATED</code></span></dt><dd><p>
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Defined by default. Not configurable. ABI-changing. Turning this off
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removes older ARM-style iostreams code, and other anachronisms
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from the API. This macro is dependent on the version of the
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standard being tracked, and as a result may give different results for
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<code class="code">-std=c++98</code> and <code class="code">-std=c++11</code>. This may
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be useful in updating old C++ code which no longer meet the
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requirements of the language, or for checking current code
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against new language standards.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_FORCE_NEW</code></span></dt><dd><p>
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Undefined by default. When defined, memory allocation and
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allocators controlled by libstdc++ call operator new/delete
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without caching and pooling. Configurable via
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<code class="code">--enable-libstdcxx-allocator</code>. ABI-changing.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_CONCEPT_CHECKS</code></span></dt><dd><p>
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Undefined by default. Configurable via
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<code class="code">--enable-concept-checks</code>. When defined, performs
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compile-time checking on certain template instantiations to
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detect violations of the requirements of the standard. This
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is described in more detail <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">here</a>.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG</code></span></dt><dd><p>
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Undefined by default. When defined, compiles user code using
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the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_DEBUG_PEDANTIC</code></span></dt><dd><p>
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Undefined by default. When defined while compiling with
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the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>, makes
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the debug mode extremely picky by making the use of libstdc++
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extensions and libstdc++-specific behavior into errors.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_PARALLEL</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
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using the <a class="link" href="parallel_mode.html" title="Chapter 18. Parallel Mode">parallel
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mode</a>.
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</p></dd><dt><span class="term"><code class="code">_GLIBCXX_PROFILE</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
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using the <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">profile
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mode</a>.
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</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="../index.html">Home</a></td><td align="right" valign="top"> Namespaces</td></tr></table></div></body></html>
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