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| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><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 Vsnapshot" /><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_dual_abi.html" title="Dual ABI" /></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_headers.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="using_dual_abi.html">Next</a></td></tr></table><hr /></div><div class="section"><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 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 |
| <code class="filename"><ios></code>. 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 are the macros which users may check for library version |
| information. </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="code">_GLIBCXX_RELEASE</code></span></dt><dd><p>The major release number for libstdc++. This macro is defined |
| to the GCC major version that the libstdc++ headers belong to, |
| as an integer constant. |
| When compiling with GCC it has the same value as GCC's pre-defined |
| macro <span class="symbol">__GNUC__</span>. |
| This macro can be used when libstdc++ is used with a non-GNU |
| compiler where <span class="symbol">__GNUC__</span> is not defined, or has a |
| different value that doesn't correspond to the libstdc++ version. |
| This macro first appeared in the GCC 7.1 release and is not defined |
| for GCC 6.x or older releases. |
| </p></dd><dt><span class="term"><code class="code">__GLIBCXX__</code></span></dt><dd><p>The revision date of the libstdc++ source code, |
| in compressed ISO date format, as an unsigned |
| long. For notes about using this macro and details on the value of |
| this macro for a particular release, please consult the |
| <a class="link" href="abi.html#abi.versioning.__GLIBCXX__">ABI History</a> |
| appendix. |
| </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 in |
| <a class="link" href="configure.html" title="Configure">Configure</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 class="variablelist"><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 |
| different <code class="code">-std</code> options. 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_USE_CXX11_ABI</code></span></dt><dd><p> |
| Defined to the value <code class="literal">1</code> by default. |
| Configurable via <code class="code">--disable-libstdcxx-dual-abi</code> |
| and/or <code class="code">--with-default-libstdcxx-abi</code>. |
| ABI-changing. |
| When defined to a non-zero value the library headers will use the |
| new C++11-conforming ABI introduced in GCC 5, rather than the older |
| ABI introduced in GCC 3.4. This changes the definition of several |
| class templates, including <code class="classname">std:string</code>, |
| <code class="classname">std::list</code> and some locale facets. |
| For more details see <a class="xref" href="using_dual_abi.html" title="Dual ABI">Dual ABI</a>. |
| </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 |
| macro has no effect for freestanding implementations. |
| This is described in more detail in |
| <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">Compile Time Checks</a>. |
| </p></dd><dt><span class="term"><code class="code">_GLIBCXX_ASSERTIONS</code></span></dt><dd><p> |
| Undefined by default. When defined, enables extra error checking in |
| the form of precondition assertions, such as bounds checking in |
| strings and null pointer checks when dereferencing smart pointers. |
| </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>. |
| When defined, <code class="code">_GLIBCXX_ASSERTIONS</code> is defined |
| automatically, so all the assertions enabled by that macro are also |
| enabled in debug mode. |
| </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_PARALLEL_ASSERTIONS</code></span></dt><dd><p>Undefined by default, but when any parallel mode header is included |
| this macro will be defined to a non-zero value if |
| <code class="code">_GLIBCXX_ASSERTIONS</code> has a non-zero value, otherwise to zero. |
| When defined to a non-zero value, it enables extra error checking and |
| assertions in the parallel mode. |
| </p></dd><dt><span class="term"><code class="code">__STDCPP_WANT_MATH_SPEC_FUNCS__</code></span></dt><dd><p>Undefined by default. When defined to a non-zero integer constant, |
| enables support for ISO/IEC 29124 Special Math Functions. |
| </p></dd><dt><span class="term"><code class="code">_GLIBCXX_SANITIZE_VECTOR</code></span></dt><dd><p> |
| Undefined by default. When defined, <code class="classname">std::vector</code> |
| operations will be annotated so that AddressSanitizer can detect |
| invalid accesses to the unused capacity of a |
| <code class="classname">std::vector</code>. These annotations are only |
| enabled for |
| <code class="classname">std::vector<T, std::allocator<T>></code> |
| and only when <code class="classname">std::allocator</code> is derived from |
| <a class="link" href="memory.html#allocator.ext" title="Extension Allocators"><code class="classname">new_allocator</code> |
| or <code class="classname">malloc_allocator</code></a>. The annotations |
| must be present on all vector operations or none, so this macro must |
| be defined to the same value for all translation units that create, |
| destroy or modify vectors. |
| </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_dual_abi.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"> Dual ABI</td></tr></table></div></body></html> |