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3 All library macros begin with
<code class=
"code">_GLIBCXX_
</code>.
5 Furthermore, all pre-processor macros, switches, and
6 configuration options are gathered in the
7 file
<code class=
"filename">c++config.h
</code>, which
8 is generated during the libstdc++ configuration and build
9 process. This file is then included when needed by files part of
10 the public libstdc++ API, like
<ios
>. Most of these macros
11 should not be used by consumers of libstdc++, and are reserved
12 for internal implementation use.
<span class=
"emphasis"><em>These macros cannot
13 be redefined
</em></span>.
15 A select handful of macros control libstdc++ extensions and extra
16 features, or provide versioning information for the API. Only
17 those macros listed below are offered for consideration by the
19 </p><p>Below is the macro which users may check for library version
20 information.
</p><div class=
"variablelist"><dl class=
"variablelist"><dt><span class=
"term"><code class=
"code">__GLIBCXX__
</code></span></dt><dd><p>The current version of
21 libstdc++ in compressed ISO date format, form of an unsigned
22 long. For details on the value of this particular macro for a
23 particular release, please consult this
<a class=
"link" href=
"abi.html" title=
"ABI Policy and Guidelines">
25 </p></dd></dl></div><p>Below are the macros which users may change with #define/#undef or
26 with -D/-U compiler flags. The default state of the symbol is
27 listed.
</p><p><span class=
"quote">“
<span class=
"quote">Configurable
</span>”
</span> (or
<span class=
"quote">“
<span class=
"quote">Not configurable
</span>”
</span>) means
28 that the symbol is initially chosen (or not) based on
29 --enable/--disable options at library build and configure time
30 (documented
<a class=
"link" href=
"configure.html" title=
"Configure">here
</a>), with the
31 various --enable/--disable choices being translated to
33 </p><p> <acronym class=
"acronym">ABI
</acronym> means that changing from the default value may
34 mean changing the
<acronym class=
"acronym">ABI
</acronym> of compiled code. In other words, these
35 choices control code which has already been compiled (i.e., in a
36 binary such as libstdc++.a/.so). If you explicitly #define or
37 #undef these macros, the
<span class=
"emphasis"><em>headers
</em></span> may see different code
38 paths, but the
<span class=
"emphasis"><em>libraries
</em></span> which you link against will not.
39 Experimenting with different values with the expectation of
40 consistent linkage requires changing the config headers before
41 building/installing the library.
42 </p><div class=
"variablelist"><dl class=
"variablelist"><dt><span class=
"term"><code class=
"code">_GLIBCXX_USE_DEPRECATED
</code></span></dt><dd><p>
43 Defined by default. Not configurable. ABI-changing. Turning this off
44 removes older ARM-style iostreams code, and other anachronisms
45 from the API. This macro is dependent on the version of the
46 standard being tracked, and as a result may give different results for
47 <code class=
"code">-std=c++
98</code> and
<code class=
"code">-std=c++
11</code>. This may
48 be useful in updating old C++ code which no longer meet the
49 requirements of the language, or for checking current code
50 against new language standards.
51 </p></dd><dt><span class=
"term"><code class=
"code">_GLIBCXX_CONCEPT_CHECKS
</code></span></dt><dd><p>
52 Undefined by default. Configurable via
53 <code class=
"code">--enable-concept-checks
</code>. When defined, performs
54 compile-time checking on certain template instantiations to
55 detect violations of the requirements of the standard. This
56 is described in more detail
<a class=
"link" href=
"ext_compile_checks.html" title=
"Chapter 16. Compile Time Checks">here
</a>.
57 </p></dd><dt><span class=
"term"><code class=
"code">_GLIBCXX_DEBUG
</code></span></dt><dd><p>
58 Undefined by default. When defined, compiles user code using
59 the
<a class=
"link" href=
"debug_mode.html" title=
"Chapter 17. Debug Mode">debug mode
</a>.
60 </p></dd><dt><span class=
"term"><code class=
"code">_GLIBCXX_DEBUG_PEDANTIC
</code></span></dt><dd><p>
61 Undefined by default. When defined while compiling with
62 the
<a class=
"link" href=
"debug_mode.html" title=
"Chapter 17. Debug Mode">debug mode
</a>, makes
63 the debug mode extremely picky by making the use of libstdc++
64 extensions and libstdc++-specific behavior into errors.
65 </p></dd><dt><span class=
"term"><code class=
"code">_GLIBCXX_PARALLEL
</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
66 using the
<a class=
"link" href=
"parallel_mode.html" title=
"Chapter 18. Parallel Mode">parallel
68 </p></dd><dt><span class=
"term"><code class=
"code">_GLIBCXX_PROFILE
</code></span></dt><dd><p>Undefined by default. When defined, compiles user code
69 using the
<a class=
"link" href=
"profile_mode.html" title=
"Chapter 19. Profile Mode">profile
71 </p></dd></dl></div></div><div class=
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