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| <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 V1.74.0" /><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_namespaces.html" title="Namespaces" /><link rel="next" href="using_concurrency.html" title="Concurrency" /></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_namespaces.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="using_concurrency.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.macros"></a>Macros</h2></div></div></div><p>All pre-processor switches and configurations are all gathered |
| in the file <code class="code">c++config.h</code>, which is generated during |
| the libstdc++ configuration and build process, and included by |
| files part of the public libstdc++ API. 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>. However, a select handful of these macro |
| control libstdc++ extensions and extra features, or provide |
| versioning information for the API, and are able to be used. |
| </p><p>All library macros begin with <code class="code">_GLIBCXX_</code> (except for |
| versions 3.1.x to 3.3.x, which use <code class="code">_GLIBCPP_</code>). |
| </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="ulink" href="abi.html" target="_top"> |
| 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">Configurable</span>” (or “<span class="quote">Not configurable</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_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="ulink" href="../19_diagnostics/howto.html#3" target="_top">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="ulink" href="../ext/debug.html#safe" target="_top">libstdc++ 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="ulink" href="../ext/debug.html#safe" target="_top">libstdc++ 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="ulink" href="../ext/parallel_mode.html" target="_top">libstdc++ parallel |
| mode</a>. |
| </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_namespaces.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_concurrency.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Namespaces </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Concurrency</td></tr></table></div></body></html> |
