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- <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" />
- <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" />
- <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3." />
- <meta name="GENERATOR" content="vi and eight fingers" />
- <title>libstdc++-v3 configure options</title>
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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
- <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>.
-</p>
-
-<!-- ####################################################### -->
-<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://www.gnu.org/manual/autoconf/html_node/Package-Options.html#Package%20Options">they
- all have opposite forms as well</a>
- (enable/disable and with/without). The defaults are for current
- development sources.
-</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>
- <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-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-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>--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-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. 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>.
- </p>
- </dd>
-
- <dt><code>--enable-clocale </code></dt>
- <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
- (described next). This option can change the library ABI.
- </p>
- </dd>
-
- <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
- 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.
- </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-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.
- </p>
- </dd>
-
- <dt><code>--enable-threads </code></dt>
- <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
- (described next). This option can change the library ABI.
- </p>
- </dd>
-
- <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-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>
- 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>
- </p>
- </dd>
-
- <dt><code>--enable-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-debug-flags='-g3 -O1 -gdwarf-2'</pre>
- </dd>
-
- <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++. 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.
- </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>
- -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><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-c-mbchar </code>[default]</dt>
- <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. This option can change
- the library ABI.
- </p>
- </dd>
-
- <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-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>
-</dl>
-<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>
-
-
-<!-- ####################################################### -->
-
-<hr />
-<p class="fineprint"><em>
-See <a href="17_intro/license.html">license.html</a> for copying conditions.
-Comments and suggestions are welcome, and may be sent to
-<a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
-</em></p>
-
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