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- <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)">
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- <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3.">
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<h1 class="centered"><a name="top">Interesting <code>configure</code>
options</a></h1>
-<p>The latest version of this document is always available at
+<p class="fineprint"><em>
+ The latest version of this document is always available at
<a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>.
-</p>
-
-<p>To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
+</em></p>
+<p><em>
+ To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
+</em></p>
<!-- ####################################################### -->
-<hr>
+<hr />
<p>Here are some of the non-obvious options to libstdc++'s configure.
Keep in mind that
<!-- This SECnn should be the "Choosing Package Options" section. -->
- <a href="http://sources.redhat.com/autoconf/autoconf.html#SEC74">they
+ <a href="http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_node/autoconf_131.html#SEC131">they
all have opposite forms as well</a>
- (enable/disable and with/without). The defaults are for current
- development sources.
+ (enable/disable and with/without). The defaults are for <strong>current
+ development sources</strong>, 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:<code> ./configure --help</code>
+</p>
<dl>
- <dt><code>--enable-multilib </code>[default]
+ <dt><code>--enable-multilib </code>[default]</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><code>--enable-debug </code>
- <dd><p>The configure script will automatically detect the highest
- level of optimization that the compiler in use can use
- (certain versions of g++ will ICE if given the <code>-O2</code>
- option, but this is fixed in later versions of the compiler).
- This --enable flag will disable all optimizations and instruct
- the compiler to emit as much extra debugging information as it
- can, for use inside GDB. Note this make command, executed in
- the build directory, will do much the same thing, without the
- configuration difference:<code>make CXXFLAGS='-g -O0' all</code>
+ <dt><code>--enable-sjlj-exceptions </code></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><code>--enable-cstdio </code>
- <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
- (described next).
+ <dt><code>--enable-version-specific-runtime-libs </code></dt>
+ <dd><p>Specify that run-time libraries should be installed in the
+ compiler-specific subdirectory (i.e.,
+ <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
+ instead of <code>${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>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
+ unless you also specify
+ <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
</p>
+ </dd>
- <dt><code>--enable-cstdio=LIB </code>
- <dd><p>Select a target-specific I/O package. As of libstdc++-v3
- snapshot 3.0.96, the choices are 'libio' to specify the GNU
- I/O package (from
- <a href="http://sources.redhat.com/glibc/">glibc</a>, the
- GNU C library), or 'stdio' to use a generic "C"
- abstraction. The default is 'stdio'. A longer explanation
- is <a href="explanations.html#cstdio">here</a>.
+ <dt><code>--with-gxx-include-dir=<include-files dir></code></dt>
+ <dd><p>Adds support for named libstdc++ include directory. For instance,
+ the following puts all the libstdc++ headers into a directory
+ called "2.97-20001008" instead of the usual
+ "c++/(version)".
</p>
+ <pre>
+ --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd>
- <dt><code>--enable-sjlj-exceptions </code>
- <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.
+ <dt><code>--enable-cstdio </code></dt>
+ <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
+ (described next). This option can change the library ABI.
+ </p>
+ </dd>
+
+ <dt><code>--enable-cstdio=OPTION </code></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'. A longer explanation is <a
+ href="explanations.html#cstdio">here</a>.
</p>
+ </dd>
- <dt><code>--enable-clocale </code>
+ <dt><code>--enable-clocale </code></dt>
<dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
- (described next).
+ (described next). This option can change the library ABI.
</p>
+ </dd>
- <dt><code>--enable-clocale=MODEL </code>
+ <dt><code>--enable-clocale=OPTION </code></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
+ library (langinfo/iconv/gettext) (from <a
href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
library), or 'generic' to use a generic "C"
- abstraction which consists of "C" locale info. The
- default is 'generic'.
+ abstraction which consists of "C" locale info.
</p>
- <dt><code>--enable-c99 </code>
- <dd><p>The "long long" 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>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.
- </p>
+ <p>As part of the configuration process, the "C" library is
+ probed both for sufficient vintage, and installed locale
+ data. If either of these elements are not present, the C++
+ locale model default to 'generic.' On glibc-based systems of
+ version 2.2.5 and above with installed locale files, 'gnu' is
+ automatically selected.
+ </p>
+ </dd>
- <dt><code>--enable-long-long </code>
- <dd><p>The "long long" 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).
+ <dt><code>--enable-libstdcxx-allocator </code></dt>
+ <dd><p>This is an abbreviated form of
+ <code>'--enable-libstdcxx-allocator=auto'</code> (described
+ next). This option can change the library ABI.
</p>
+ </dd>
- <dt><code>--enable-cheaders=OPTION </code>
+ <dt><code>--enable-libstdcxx-allocator=OPTION </code></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
+ (<a href="ext/mt_allocator.html">documented</a> under extensions) or
+ 'bitmap' for a bitmap allocator. This option can change the
+ library ABI.
+ </p>
+ </dd>
+
+ <dt><code>--enable-cheaders=OPTION </code></dt>
<dd><p>This allows the user to define what kind of C headers are
- used. Options are: c, c_std, and c_shadow. These correspond
- to the source directory's include/c, include/c_std, and
- include/c_shadow directories. The default is c_std.
+ used. Options are c and c_std. These correspond to the source
+ directory's include/c and include/c_std. The default is c_std.
</p>
+ </dd>
- <dt><code>--enable-threads </code>
+ <dt><code>--enable-threads </code></dt>
<dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
- (described next).
+ (described next). This option can change the library ABI.
</p>
+ </dd>
- <dt><code>--enable-threads=LIB </code>
+ <dt><code>--enable-threads=OPTION </code></dt>
<dd><p>Select a threading library. A full description is given in the
general <a href="http://gcc.gnu.org/install/configure.html">compiler
configuration instructions</a>.
</p>
+ </dd>
- <dt><code>--enable-version-specific-runtime-libs </code>
- <dd><p>Specify that run-time libraries should be installed in the
- compiler-specific subdirectory (i.e.,
- <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
- instead of <code>${libdir}</code>. This option is useful if you
- intend to use several versions of gcc in parallel. In addition,
- libstdc++'s include files will be installed in
- <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
- unless you also specify
- <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
+ <dt><code>--enable-libstdcxx-debug </code></dt>
+ <dd><p>Build separate debug libraries in addition to what is normally built.
+ By default, the debug libraries are compiled with
+ <code> CXXFLAGS='-g3 -O0'</code>
+ , are installed in <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>make CXXFLAGS='-g3 -O0' all</code>
+ </p>
+ </dd>
- <dt><code>--with-gxx-include-dir=<include-files dir></code>
- <dd><p>Adds support for named libstdc++ include directory. For instance,
- the following puts all the libstdc++ headers into a directory
- called "2.97-20001008" instead of the usual
- "g++-v3".
- <pre>
- --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre>
+ <dt><code>--enable-libstdcxx-debug-flags=FLAGS</code></dt>
+
+ <dd><p>This option is only valid when <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>
+ --enable-libstdcxx-debug-flags='-g3 -O1 -gdwarf-2'</pre>
+ </dd>
- <dt><code>--enable-cxx-flags=FLAGS</code>
+ <dt><code>--enable-cxx-flags=FLAGS</code></dt>
<dd><p>With this option, you can pass a string of -f (functionality)
- flags to the compiler to use when building libstdc++. FLAGS
- is a quoted string of options, like
+ 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>
--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.
as well, so that everything matches.
</p>
<p>Fun flags to try might include combinations of
+ </p>
<pre>
-fstrict-aliasing
-fno-exceptions
-ffunction-sections
-fvtable-gc</pre>
- and opposite forms (-fno-) of the same. Tell us (the libstdc++
+ <p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
mailing list) if you discover more!
</p>
+ </dd>
- <dt><code>--enable-c-mbchar </code>[default]
- <dd><p>Certain template specializations are required for wide
- character conversion support. This is tricky and currently
- changing rapidly, and can cause problems on new platforms.
- Disabling wide character specializations is useful for initial
- porting steps, but builds only a subset of what is required by
- ISO. By default, this option is on.
+ <dt><code>--enable-c99 </code></dt>
+ <dd><p>The "long long" 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>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><code>--enable-wchar_t </code>[default]</dt>
+ <dd><p>Template specializations for the "wchar_t" 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><code>--enable-concept-checks </code>
+ <dt><code>--enable-long-long </code></dt>
+ <dd><p>The "long long" 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><code>--enable-fully-dynamic-string </code></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><code>--enable-concept-checks </code></dt>
<dd><p>This turns on additional compile-time checks for instantiated
library templates, in the form of specialized templates,
<a href="19_diagnostics/howto.html#3">described here</a>. They
can help users discover when they break the rules of the STL, before
their programs run.
</p>
+ </dd>
+
+ <dt><code>--enable-symvers[=style] </code></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). The
+ only 'style' currently supported is 'gnu' which requires that
+ a recent version of the GNU linker be in use. With no style
+ given, the configure script will try to guess if the 'gnu'
+ style can be used, and if so, will turn it on. Hopefully
+ people will volunteer to do other 'style' options.
+ </p>
+ </dd>
- <dt><code>--enable-symvers[=style] </code>
- <dd><p>In 3.1, tries to turn on symbol versioning in the shared library (if a
- shared library has been requested). The only 'style' currently
- supported is 'gnu' which requires that a recent version of the GNU
- linker be in use. With no style given, the configure script will
- try to guess if the 'gnu' style can be used, and if so, will turn it
- on. Hopefully people will volunteer to do other 'style' options.
+ <dt><code>--enable-libstdcxx-pch </code></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>
+ --include bits/stdc++.h </code> to CXXFLAGS) when running the
+ testsuite.
</p>
+ </dd>
+
+ <dt><code>--disable-hosted-libstdcxx </code></dt>
+ <dd><p>By default, a complete <em>hosted</em> C++ library is built. The
+ C++ Standard also describes a <em>freestanding</em> environment,
+ in which only a minimal set of headers are provided. This option
+ builds such an environment.
+ </p>
+ </dd>
</dl>
-</p>
<p>Return <a href="#top">to the top of the page</a> or
<a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>.
</p>
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+<hr />
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