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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>Configure</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.77.1" /><meta name="keywords" content="ISO C++, configure, options" /><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="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><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"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.setup.configure"></a>Configure</h2></div></div></div><p>
When configuring libstdc++, you'll have to configure the entire
<span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the
toplevel gcc configuration option
<code class="literal">--enable-languages=c++</code>, which saves time by only
building the C++ toolchain.
</p><p>
Here are all of the configure options specific to libstdc++. Keep
in mind that
<a class="link" href="http://sourceware.org/autobook/autobook/autobook_14.html" target="_top">they
all have opposite forms as well</a> (enable/disable and
with/without). The defaults are for the <span class="emphasis"><em>current
development sources</em></span>, which may be different than those
for released versions.
</p><p>The canonical way to find out the configure options that are
available for a given set of libstdc++ sources is to go to the
source directory and then type: <span class="command"><strong>./configure --help</strong></span>.
</p><div class="variablelist"><dl class="variablelist"><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
compilers. As such, targets like "powerpc-elf" will have
libstdc++ built many different ways: "-msoft-float"
and not, etc. A different libstdc++ will be built for each of
the different multilib versions. This option is on by default.
</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
at all possible, the new, frame unwinding exception handling routines
should be used instead, as they significantly reduce both
runtime memory usage and executable size. This option can
change the library ABI.
</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
compiler-specific subdirectory (i.e.,
<code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
instead of <code class="code">${libdir}</code>. This option is useful if you
intend to use several versions of gcc in parallel. In addition,
libstdc++'s include files will be installed in
<code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
unless you also specify
<code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration.
</p></dd><dt><span class="term"><code class="code">--with-gxx-include-dir=<include-files dir></code></span></dt><dd><p>Adds support for named libstdc++ include directory. For instance,
the following puts all the libstdc++ headers into a directory
called "4.4-20090404" instead of the usual
"c++/(version)".
</p><pre class="programlisting">
--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>
(described next).
</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
choice is to use 'stdio', a generic "C" abstraction.
The default is 'stdio'. This option can change the library ABI.
</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>
(described next).
</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
choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
(IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
'gnu' to specify a model based on functionality from the GNU C
library (langinfo/iconv/gettext) (from <a class="link" href="https://www.gnu.org/software/libc/" target="_top">glibc</a>, the GNU C
library), 'generic' to use a generic "C" abstraction which consists
of "C" locale info, 'newlib' to specify the Newlib C library model
which only differs from the 'generic' model in the handling of
ctype, or 'darwin' which omits the <span class="type">wchar_t</span> specializations
needed by the 'generic' model.
</p><p>If not explicitly specified, the configure process tries
to guess the most suitable package from the choices above. The
default is 'generic'. On glibc-based systems of sufficient
vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based
systems (<code class="code">'--with_newlib=yes'</code>) and OpenBSD, 'newlib' is
automatically selected. On Mac OS X 'darwin' is automatically selected.
This option can change the library ABI.
</p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of
<code class="code">'--enable-libstdcxx-allocator=auto'</code> (described
next).
</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
choices are 'new' to specify a wrapper for new, 'malloc' to
specify a wrapper for malloc, 'mt' for a fixed power of two allocator,
'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
See this page for more information on allocator
<a class="link" href="memory.html#allocator.ext" title="Extension Allocators">extensions</a>. This option
can change the library ABI.
</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
compatibility with C++. Options are c, c_std, and c_global.
These correspond to the source directory's include/c,
include/c_std, and include/c_global, and may also include
include/c_compatibility. The default is 'c_global'.
</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>
(described next).
</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
given in the
general <a class="link" href="http://gcc.gnu.org/install/configure.html" target="_top">compiler
configuration instructions</a>. This option can change the
library ABI.
</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,
the configure process enables it if possible. It defaults to 'off'
on Solaris 9, where it would break symbol versioning. This
option can change the library ABI.
</p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of
<code class="code">'--enable-libstdcxx-time=yes'</code>(described next).
</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
clock_gettime clocks, used in the implementation of [time.clock],
and of the nanosleep and sched_yield functions, used in the
implementation of [thread.thread.this] of the 2011 ISO C++ standard.
The choice OPTION=yes checks for the availability of the facilities
in libc and libposix4. In case it's needed the latter is also linked
to libstdc++ as part of the build process. OPTION=rt also searches
(and, if needed, links) librt. Note that the latter is not always
desirable because, in glibc, for example, in turn it triggers the
linking of libpthread too, which activates locking, a large overhead
for single-thread programs. OPTION=no skips the tests completely.
The default is OPTION=no.
</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.
By default, the debug libraries are compiled with
<code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code>
, are installed in <code class="code">${libdir}/debug</code>, and have the
same names and versioning information as the non-debug
libraries. This option is off by default.
</p><p>Note this make command, executed in
the build directory, will do much the same thing, without the
configuration difference and without building everything twice:
<code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code>
</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>
is also specified, and applies to the debug builds only. With
this option, you can pass a specific string of flags to the
compiler to use when building the debug versions of libstdc++.
FLAGS is a quoted string of options, like
</p><pre class="programlisting">
--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)
flags to the compiler to use when building libstdc++. This
option can change the library ABI. FLAGS is a quoted string of
options, like
</p><pre class="programlisting">
--enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p>
Note that the flags don't necessarily have to all be -f flags,
as shown, but usually those are the ones that will make sense
for experimentation and configure-time overriding.
</p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
the 'make' environment is that, if files are automatically
rebuilt, the same flags will be used when compiling those files
as well, so that everything matches.
</p><p>Fun flags to try might include combinations of
</p><pre class="programlisting">
-fstrict-aliasing
-fno-exceptions
-ffunction-sections
-fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
mailing list) if you discover more!
</p></dd><dt><span class="term"><code class="code">--enable-c99</code></span></dt><dd><p>The <span class="type">long long</span> type was introduced in C99, along
with many other functions for wide characters, and math
classification macros, etc. If enabled, all C99 functions not
specified by the C++ standard will be put into <code class="code">namespace
__gnu_cxx</code>, and then all these names will
be injected into namespace std, so that C99 functions can be
used "as if" they were in the C++ standard (as they
will eventually be in some future revision of the standard,
without a doubt). By default, C99 support is on, assuming the
configure probes find all the necessary functions and bits
necessary. This option can change the library ABI.
</p></dd><dt><span class="term"><code class="code">--enable-wchar_t</code>[default]</span></dt><dd><p>Template specializations for the <span class="type">wchar_t</span> type are
required for wide character conversion support. Disabling
wide character specializations may be expedient for initial
porting efforts, but builds only a subset of what is required by
ISO, and is not recommended. By default, this option is on.
This option can change the library ABI.
</p></dd><dt><span class="term"><code class="code">--enable-long-long </code></span></dt><dd><p>The <span class="type">long long</span> type was introduced in C99. It is
provided as a GNU extension to C++98 in g++. This flag builds
support for "long long" into the library (specialized
templates and the like for iostreams). This option is on by default:
if enabled, users will have to either use the new-style "C"
headers by default (i.e., <cmath> not <math.h>)
or add appropriate compile-time flags to all compile lines to
allow "C" visibility of this feature (on GNU/Linux,
the flag is -D_ISOC99_SOURCE, which is added automatically via
CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
This option can change the library ABI.
</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
the optimization that allocates empty objects in static memory.
Mostly useful together with shared memory allocators, see PR
libstdc++/16612 for details.
</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
library templates, in the form of specialized templates,
<a class="link" href="concept_checking.html" title="Concept Checking">described here</a>. They
can help users discover when they break the rules of the STL, before
their programs run.
</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
shared library (if a shared library has been
requested). Values for 'style' that are currently supported
are 'gnu', 'gnu-versioned-namespace', 'darwin',
'darwin-export', and 'sun'. Both gnu- options require that a recent
version of the GNU linker be in use. Both darwin options are
equivalent. With no style given, the configure script will try
to guess correct defaults for the host system, probe to see if
additional requirements are necessary and present for
activation, and if so, will turn symbol versioning on. This
option can change the library ABI.
</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
attributes. If enabled (as by default), and the compiler seems
capable of passing the simple sanity checks thrown at it, adjusts
items in namespace std, namespace std::tr1, namespace std::tr2,
and namespace __gnu_cxx to have <code class="code">visibility ("default")</code>
so that -fvisibility options can be used without affecting the
normal external-visibility of namespace std entities.
Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>.
</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
stdc++.h.gch, a pre-compiled file including all the standard
C++ includes. If enabled (as by default), and the compiler
seems capable of passing the simple sanity checks thrown at
it, try to build stdc++.h.gch as part of the make process.
In addition, this generated file is used later on (by appending <code class="code">
--include bits/stdc++.h </code> to CXXFLAGS) when running the
testsuite.
</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
specializations for certain types defined in the standard libraries.
These types include <code class="classname">string</code> and dependents like
<code class="classname">char_traits</code>, the templatized IO classes,
<code class="classname">allocator</code>, and others.
Disabling means that implicit
template generation will be used when compiling these types. By
default, this option is on. This option can change the library ABI.
</p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p>
By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is
built. The C++ Standard also describes a
<span class="emphasis"><em>freestanding</em></span> environment, in which only a
minimal set of headers are provided. This option builds such an
environment.
</p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-verbose</code></span></dt><dd><p>
By default, the library is configured to write descriptive messages
to standard error for certain events such as calling a pure virtual
function or the invocation of the standard terminate handler. Those
messages cause the library to depend on the demangler and standard I/O
facilites, which might be undesirable in a low-memory environment or
when standard error is not available. This option disables those
messages. This option does not change the library ABI.
</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>
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