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  17     "><link rel="home" href="../index.html" title="The GNU C++ Library"><link rel="up" href="setup.html" title="Chapter 2. Setup"><link rel="prev" href="setup.html" title="Chapter 2. Setup"><link rel="next" href="make.html" title="Make"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Configure</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="setup.html">Prev</a> </td><th width="60%" align="center">Chapter 2. Setup</th><td width="20%" align="right"> <a accesskey="n" href="make.html">Next</a></td></tr></table><hr></div><div class="section" title="Configure"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="manual.intro.setup.configure"></a>Configure</h2></div></div></div><p>
  18   When configuring libstdc++, you'll have to configure the entire
  19   <span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the
  20   toplevel gcc configuration option
  21   <code class="literal">--enable-languages=c++</code>, which saves time by only
  22   building the C++ toolchain.
  23 </p><p>
  24   Here are all of the configure options specific to libstdc++.  Keep
  25   in mind that
  26
  27    <a class="link" href="http://sourceware.org/autobook/autobook/autobook_14.html" target="_top">they
  28    all have opposite forms as well</a> (enable/disable and
  29    with/without).  The defaults are for the <span class="emphasis"><em>current
  30    development sources</em></span>, which may be different than those
  31    for released versions.
  32 </p><p>The canonical way to find out the configure options that are
  33    available for a given set of libstdc++ sources is to go to the
  34    source directory and then type:<span class="command"><strong>./configure --help</strong></span>.
  35 </p><div class="variablelist"><dl><dt><span class="term"><code class="code">--enable-multilib</code>[default]</span></dt><dd><p>This is part of the generic multilib support for building cross
  36         compilers.  As such, targets like "powerpc-elf" will have
  37         libstdc++ built many different ways:  "-msoft-float"
  38         and not, etc.  A different libstdc++ will be built for each of
  39         the different multilib versions.  This option is on by default.
  40      </p></dd><dt><span class="term"><code class="code">--enable-sjlj-exceptions</code></span></dt><dd><p>Forces old, set-jump/long-jump exception handling model.  If
  41         at all possible, the new, frame unwinding exception handling routines
  42         should be used instead, as they significantly reduce both
  43         runtime memory usage and executable size. This option can
  44         change the library ABI.
  45      </p></dd><dt><span class="term"><code class="code">--enable-version-specific-runtime-libs</code></span></dt><dd><p>Specify that run-time libraries should be installed in the
  46         compiler-specific subdirectory (i.e.,
  47         <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
  48         instead of <code class="code">${libdir}</code>.  This option is useful if you
  49         intend to use several versions of gcc in parallel.  In addition,
  50         libstdc++'s include files will be installed in
  51         <code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
  52         unless you also specify
  53        <code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration.
  54      </p></dd><dt><span class="term"><code class="code">--with-gxx-include-dir=&lt;include-files dir&gt;</code></span></dt><dd><p>Adds support for named libstdc++ include directory.  For instance,
  55         the following puts all the libstdc++ headers into a directory
  56         called "4.4-20090404" instead of the usual
  57         "c++/(version)".
  58      </p><pre class="programlisting">
  59    --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/4.4-20090404</pre></dd><dt><span class="term"><code class="code">--enable-cstdio</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-cstdio=stdio'</code>
  60         (described next).
  61      </p></dd><dt><span class="term"><code class="code">--enable-cstdio=OPTION</code></span></dt><dd><p>Select a target-specific I/O package. At the moment, the only
  62         choice is to use 'stdio', a generic "C" abstraction.
  63         The default is 'stdio'. This option can change the library ABI.
  64      </p></dd><dt><span class="term"><code class="code">--enable-clocale</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-clocale=generic'</code>
  65         (described next).
  66      </p></dd><dt><span class="term"><code class="code">--enable-clocale=OPTION</code></span></dt><dd><p>Select a target-specific underlying locale package.  The
  67         choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
  68         (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
  69         'gnu' to specify a model based on functionality from the GNU C
  70         library (langinfo/iconv/gettext) (from <a class="link" href="http://sources.redhat.com/glibc/" target="_top">glibc</a>, the GNU C
  71         library), or 'generic' to use a generic "C"
  72         abstraction which consists of "C" locale info.
  73      </p><p>If not explicitly specified, the configure proccess tries
  74       to guess the most suitable package from the choices above. The
  75       default is 'generic'. On glibc-based systems of sufficient
  76       vintage (2.3 and newer), 'gnu' is automatically selected. This option
  77       can change the library ABI.
  78      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of
  79         <code class="code">'--enable-libstdcxx-allocator=auto'</code> (described
  80         next).
  81      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator=OPTION  </code></span></dt><dd><p>Select a target-specific underlying std::allocator.  The
  82         choices are 'new' to specify a wrapper for new, 'malloc' to
  83         specify a wrapper for malloc, 'mt' for a fixed power of two allocator,
  84         'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
  85         See this page for more information on allocator
  86         <a class="link" href="memory.html#allocator.ext" title="Extension Allocators">extensions</a>. This option
  87         can change the library ABI.
  88      </p></dd><dt><span class="term"><code class="code">--enable-cheaders=OPTION</code></span></dt><dd><p>This allows the user to define the approach taken for C header
  89         compatibility with C++. Options are c, c_std, and c_global.
  90         These correspond to the source directory's include/c,
  91         include/c_std, and include/c_global, and may also include
  92         include/c_compatibility.  The default is 'c_global'.
  93      </p></dd><dt><span class="term"><code class="code">--enable-threads</code></span></dt><dd><p>This is an abbreviated form of <code class="code">'--enable-threads=yes'</code>
  94         (described next).
  95      </p></dd><dt><span class="term"><code class="code">--enable-threads=OPTION</code></span></dt><dd><p>Select a threading library.  A full description is
  96         given in the
  97         general <a class="link" href="http://gcc.gnu.org/install/configure.html" target="_top">compiler
  98         configuration instructions</a>. This option can change the
  99         library ABI.
 100      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-threads</code></span></dt><dd><p>Enable C++11 threads support.  If not explicitly specified,
 101         the  configure process enables it if possible.  It defaults to 'off'
 102         on Solaris 9, where it would break symbol versioning.   This
 103         option can change the library ABI.
 104      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of
 105         <code class="code">'--enable-libstdcxx-time=yes'</code>(described next).
 106      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time=OPTION</code></span></dt><dd><p>Enables link-type checks for the availability of the
 107         clock_gettime clocks, used in the implementation of [time.clock],
 108         and of the nanosleep and sched_yield functions, used in the
 109         implementation of [thread.thread.this] of the 2011 ISO C++ standard.
 110         The choice OPTION=yes checks for the availability of the facilities
 111         in libc and libposix4.  In case of need the latter is also linked
 112         to libstdc++ as part of the build process.  OPTION=rt also searches
 113         (and, in case, links) librt.   Note that the latter is not always
 114         desirable because, in glibc, for example, in turn it triggers the
 115         linking of libpthread too, which activates locking, a large overhead
 116         for single-thread programs.  OPTION=no skips the tests completely.
 117         The default is OPTION=no.
 118     </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-debug</code></span></dt><dd><p>Build separate debug libraries in addition to what is normally built.
 119         By default, the debug libraries are compiled with
 120         <code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code>
 121         , are installed in <code class="code">${libdir}/debug</code>, and have the
 122         same names and versioning information as the non-debug
 123         libraries. This option is off by default.
 124      </p><p>Note this make command, executed in
 125         the build directory, will do much the same thing, without the
 126         configuration difference and without building everything twice:
 127         <code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code>
 128      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-debug-flags=FLAGS</code></span></dt><dd><p>This option is only valid when <code class="code"> --enable-debug </code>
 129         is also specified, and applies to the debug builds only. With
 130         this option, you can pass a specific string of flags to the
 131         compiler to use when building the debug versions of libstdc++.
 132         FLAGS is a quoted string of options, like
 133      </p><pre class="programlisting">
 134   --enable-libstdcxx-debug-flags='-g3 -O1 -fno-inline'</pre></dd><dt><span class="term"><code class="code">--enable-cxx-flags=FLAGS</code></span></dt><dd><p>With this option, you can pass a string of -f (functionality)
 135         flags to the compiler to use when building libstdc++. This
 136         option can change the library ABI. FLAGS is a quoted string of
 137         options, like
 138      </p><pre class="programlisting">
 139   --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p>
 140         Note that the flags don't necessarily have to all be -f flags,
 141         as shown, but usually those are the ones that will make sense
 142         for experimentation and configure-time overriding.
 143      </p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
 144         the 'make' environment is that, if files are automatically
 145         rebuilt, the same flags will be used when compiling those files
 146         as well, so that everything matches.
 147      </p><p>Fun flags to try might include combinations of
 148      </p><pre class="programlisting">
 149   -fstrict-aliasing
 150   -fno-exceptions
 151   -ffunction-sections
 152   -fvtable-gc</pre><p>and opposite forms (-fno-) of the same.  Tell us (the libstdc++
 153         mailing list) if you discover more!
 154      </p></dd><dt><span class="term"><code class="code">--enable-c99</code></span></dt><dd><p>The "long long" type was introduced in C99, along
 155         with many other functions for wide characters, and math
 156         classification macros, etc.  If enabled, all C99 functions not
 157         specified by the C++ standard will be put into <code class="code">namespace
 158         __gnu_cxx</code>, and then all these names will
 159         be injected into namespace std, so that C99 functions can be
 160         used "as if" they were in the C++ standard (as they
 161         will eventually be in some future revision of the standard,
 162         without a doubt).  By default, C99 support is on, assuming the
 163         configure probes find all the necessary functions and bits
 164         necessary. This option can change the library ABI.
 165     </p></dd><dt><span class="term"><code class="code">--enable-wchar_t</code>[default]</span></dt><dd><p>Template specializations for the "wchar_t" type are
 166         required for wide character conversion support.  Disabling
 167         wide character specializations may be expedient for initial
 168         porting efforts, but builds only a subset of what is required by
 169         ISO, and is not recommended.  By default, this option is on.
 170         This option can change the library ABI.
 171      </p></dd><dt><span class="term"><code class="code">--enable-long-long  </code></span></dt><dd><p>The "long long" type was introduced in C99.  It is
 172         provided as a GNU extension to C++98 in g++.  This flag builds
 173         support for "long long" into the library (specialized
 174         templates and the like for iostreams).  This option is on by default:
 175         if enabled, users will have to either use the new-style "C"
 176         headers by default (i.e., &lt;cmath&gt; not &lt;math.h&gt;)
 177         or add appropriate compile-time flags to all compile lines to
 178         allow "C" visibility of this feature (on GNU/Linux,
 179         the flag is -D_ISOC99_SOURCE, which is added automatically via
 180         CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
 181         This option can change the library ABI.
 182      </p></dd><dt><span class="term"><code class="code">--enable-fully-dynamic-string</code></span></dt><dd><p>This option enables a special version of basic_string avoiding
 183         the optimization that allocates empty objects in static memory.
 184         Mostly useful together with shared memory allocators, see PR
 185         libstdc++/16612 for details.
 186      </p></dd><dt><span class="term"><code class="code">--enable-concept-checks</code></span></dt><dd><p>This turns on additional compile-time checks for instantiated
 187         library templates, in the form of specialized templates,
 188         <a class="link" href="bk01pt02ch05s02.html" title="Concept Checking">described here</a>.  They
 189         can help users discover when they break the rules of the STL, before
 190         their programs run.
 191      </p></dd><dt><span class="term"><code class="code">--enable-symvers[=style]</code></span></dt><dd><p>In 3.1 and later, tries to turn on symbol versioning in the
 192         shared library (if a shared library has been
 193         requested). Values for 'style' that are currently supported
 194         are 'gnu', 'gnu-versioned-namespace', 'darwin',
 195         'darwin-export', and 'sun'. Both gnu- options require that a recent
 196         version of the GNU linker be in use. Both darwin options are
 197         equivalent. With no style given, the configure script will try
 198         to guess correct defaults for the host system, probe to see if
 199         additional requirements are necessary and present for
 200         activation, and if so, will turn symbol versioning on. This
 201         option can change the library ABI.
 202      </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-visibility</code></span></dt><dd><p> In 4.2 and later, enables or disables visibility
 203         attributes. If enabled (as by default), and the compiler seems
 204         capable of passing the simple sanity checks thrown at it, adjusts
 205         items in namespace std, namespace std::tr1, namespace std::tr2,
 206         and namespace __gnu_cxx to have <code class="code">visibility ("default")</code>
 207         so that -fvisibility options can be used without affecting the
 208         normal external-visibility of namespace std entities.
 209         Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>.
 210     </p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-pch</code></span></dt><dd><p>In 3.4 and later, tries to turn on the generation of
 211         stdc++.h.gch, a pre-compiled file including all the standard
 212         C++ includes. If enabled (as by default), and the compiler
 213         seems capable of passing the simple sanity checks thrown at
 214         it, try to build stdc++.h.gch as part of the make process.
 215         In addition, this generated file is used later on (by appending <code class="code">
 216         --include bits/stdc++.h </code> to CXXFLAGS) when running the
 217         testsuite.
 218      </p></dd><dt><span class="term"><code class="code">--enable-extern-template</code>[default]</span></dt><dd><p>Use extern template to pre-instantiate all required
 219         specializations for certain types defined in the standard libraries.
 220         These types include <code class="classname">string</code> and dependents like
 221         <code class="classname">char_traits</code>, the templateized io classes,
 222         <code class="classname">allocator</code>, and others.
 223         Disabling means that implicit
 224         template generation will be used when compiling these types.  By
 225         default, this option is on. This option can change the library ABI.
 226      </p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p>
 227      By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is
 228      built.  The C++ Standard also describes a
 229      <span class="emphasis"><em>freestanding</em></span> environment, in which only a
 230      minimal set of headers are provided.  This option builds such an
 231      environment.
 232      </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="setup.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="setup.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="make.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 2. Setup </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Make</td></tr></table></div></body></html>