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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 V1.78.1" /><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>
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When configuring libstdc++, you'll have to configure the entire
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<span class="emphasis"><em>gccsrcdir</em></span> directory. Consider using the
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toplevel gcc configuration option
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<code class="literal">--enable-languages=c++</code>, which saves time by only
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building the C++ toolchain.
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</p><p>
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Here are all of the configure options specific to libstdc++. Keep
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in mind that
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<a class="link" href="http://sourceware.org/autobook/autobook/autobook_14.html" target="_top">they
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all have opposite forms as well</a> (enable/disable and
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with/without). The defaults are for the <span class="emphasis"><em>current
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development sources</em></span>, which may be different than those
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for released versions.
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</p><p>The canonical way to find out the configure options that are
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available for a given set of libstdc++ sources is to go to the
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source directory and then type: <span class="command"><strong>./configure --help</strong></span>.
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</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
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compilers. As such, targets like "powerpc-elf" will have
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libstdc++ built many different ways: "-msoft-float"
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and not, etc. A different libstdc++ will be built for each of
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the different multilib versions. This option is on by default.
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</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
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at all possible, the new, frame unwinding exception handling routines
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should be used instead, as they significantly reduce both
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runtime memory usage and executable size. This option can
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change the library ABI.
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</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
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compiler-specific subdirectory (i.e.,
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<code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
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instead of <code class="code">${libdir}</code>. This option is useful if you
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intend to use several versions of gcc in parallel. In addition,
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libstdc++'s include files will be installed in
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<code class="code">${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
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unless you also specify
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<code class="literal">--with-gxx-include-dir=</code><code class="filename">dirname</code> during configuration.
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</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,
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the following puts all the libstdc++ headers into a directory
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called "4.4-20090404" instead of the usual
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"c++/(version)".
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</p><pre class="programlisting">
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--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>
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(described next).
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</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
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choice is to use 'stdio', a generic "C" abstraction.
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The default is 'stdio'. This option can change the library ABI.
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</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>
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(described next).
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</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
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choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
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(IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
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'gnu' to specify a model based on functionality from the GNU C
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library (langinfo/iconv/gettext) (from <a class="link" href="https://www.gnu.org/software/libc/" target="_top">glibc</a>, the GNU C
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library), 'generic' to use a generic "C" abstraction which consists
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of "C" locale info, 'newlib' to specify the Newlib C library model
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which only differs from the 'generic' model in the handling of
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ctype, or 'darwin' which omits the <span class="type">wchar_t</span> specializations
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needed by the 'generic' model.
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</p><p>If not explicitly specified, the configure process tries
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to guess the most suitable package from the choices above. The
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default is 'generic'. On glibc-based systems of sufficient
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vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based
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systems (<code class="code">'--with_newlib=yes'</code>) and OpenBSD, 'newlib' is
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automatically selected. On Mac OS X 'darwin' is automatically selected.
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This option can change the library ABI.
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</p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-allocator</code></span></dt><dd><p>This is an abbreviated form of
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<code class="code">'--enable-libstdcxx-allocator=auto'</code> (described
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next).
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</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
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choices are 'new' to specify a wrapper for new, 'malloc' to
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specify a wrapper for malloc, 'mt' for a fixed power of two allocator,
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'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
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See this page for more information on allocator
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<a class="link" href="memory.html#allocator.ext" title="Extension Allocators">extensions</a>. This option
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can change the library ABI.
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</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
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compatibility with C++. Options are c, c_std, and c_global.
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These correspond to the source directory's include/c,
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include/c_std, and include/c_global, and may also include
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include/c_compatibility. The default is 'c_global'.
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</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>
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(described next).
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</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
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given in the
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general <a class="link" href="http://gcc.gnu.org/install/configure.html" target="_top">compiler
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configuration instructions</a>. This option can change the
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library ABI.
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</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,
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the configure process enables it if possible. It defaults to 'off'
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on Solaris 9, where it would break symbol versioning. This
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option can change the library ABI.
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</p></dd><dt><span class="term"><code class="code">--enable-libstdcxx-time</code></span></dt><dd><p>This is an abbreviated form of
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<code class="code">'--enable-libstdcxx-time=yes'</code>(described next).
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</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
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clock_gettime clocks, used in the implementation of [time.clock],
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and of the nanosleep and sched_yield functions, used in the
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implementation of [thread.thread.this] of the 2011 ISO C++ standard.
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The choice OPTION=yes checks for the availability of the facilities
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in libc and libposix4. In case it's needed the latter is also linked
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to libstdc++ as part of the build process. OPTION=rt also searches
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(and, if needed, links) librt. Note that the latter is not always
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desirable because, in glibc, for example, in turn it triggers the
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linking of libpthread too, which activates locking, a large overhead
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for single-thread programs. OPTION=no skips the tests completely.
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The default is OPTION=no.
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</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.
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By default, the debug libraries are compiled with
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<code class="code"> CXXFLAGS='-g3 -O0 -fno-inline'</code>
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, are installed in <code class="code">${libdir}/debug</code>, and have the
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same names and versioning information as the non-debug
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libraries. This option is off by default.
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</p><p>Note this make command, executed in
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the build directory, will do much the same thing, without the
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configuration difference and without building everything twice:
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<code class="code">make CXXFLAGS='-g3 -O0 -fno-inline' all</code>
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</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>
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is also specified, and applies to the debug builds only. With
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this option, you can pass a specific string of flags to the
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compiler to use when building the debug versions of libstdc++.
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FLAGS is a quoted string of options, like
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</p><pre class="programlisting">
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--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)
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flags to the compiler to use when building libstdc++. This
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option can change the library ABI. FLAGS is a quoted string of
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options, like
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</p><pre class="programlisting">
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--enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre><p>
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Note that the flags don't necessarily have to all be -f flags,
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as shown, but usually those are the ones that will make sense
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for experimentation and configure-time overriding.
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</p><p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
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the 'make' environment is that, if files are automatically
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rebuilt, the same flags will be used when compiling those files
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as well, so that everything matches.
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</p><p>Fun flags to try might include combinations of
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</p><pre class="programlisting">
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-fstrict-aliasing
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-fno-exceptions
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-ffunction-sections
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-fvtable-gc</pre><p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
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mailing list) if you discover more!
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</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
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with many other functions for wide characters, and math
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classification macros, etc. If enabled, all C99 functions not
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specified by the C++ standard will be put into <code class="code">namespace
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__gnu_cxx</code>, and then all these names will
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be injected into namespace std, so that C99 functions can be
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used "as if" they were in the C++ standard (as they
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will eventually be in some future revision of the standard,
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without a doubt). By default, C99 support is on, assuming the
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configure probes find all the necessary functions and bits
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necessary. This option can change the library ABI.
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</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
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required for wide character conversion support. Disabling
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wide character specializations may be expedient for initial
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porting efforts, but builds only a subset of what is required by
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ISO, and is not recommended. By default, this option is on.
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This option can change the library ABI.
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</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
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provided as a GNU extension to C++98 in g++. This flag builds
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support for "long long" into the library (specialized
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templates and the like for iostreams). This option is on by default:
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if enabled, users will have to either use the new-style "C"
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headers by default (i.e., <cmath> not <math.h>)
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or add appropriate compile-time flags to all compile lines to
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allow "C" visibility of this feature (on GNU/Linux,
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the flag is -D_ISOC99_SOURCE, which is added automatically via
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CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
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This option can change the library ABI.
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</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
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the optimization that allocates empty objects in static memory.
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Mostly useful together with shared memory allocators, see PR
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libstdc++/16612 for details.
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</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
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library templates, in the form of specialized templates,
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<a class="link" href="concept_checking.html" title="Concept Checking">described here</a>. They
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can help users discover when they break the rules of the STL, before
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their programs run.
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</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
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shared library (if a shared library has been
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requested). Values for 'style' that are currently supported
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are 'gnu', 'gnu-versioned-namespace', 'darwin',
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'darwin-export', and 'sun'. Both gnu- options require that a recent
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version of the GNU linker be in use. Both darwin options are
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equivalent. With no style given, the configure script will try
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to guess correct defaults for the host system, probe to see if
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additional requirements are necessary and present for
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activation, and if so, will turn symbol versioning on. This
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option can change the library ABI.
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</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
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attributes. If enabled (as by default), and the compiler seems
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capable of passing the simple sanity checks thrown at it, adjusts
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items in namespace std, namespace std::tr1, namespace std::tr2,
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and namespace __gnu_cxx to have <code class="code">visibility ("default")</code>
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so that -fvisibility options can be used without affecting the
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normal external-visibility of namespace std entities.
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Prior to 4.7 this option was spelled <code class="code">--enable-visibility</code>.
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</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
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stdc++.h.gch, a pre-compiled file including all the standard
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C++ includes. If enabled (as by default), and the compiler
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seems capable of passing the simple sanity checks thrown at
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it, try to build stdc++.h.gch as part of the make process.
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In addition, this generated file is used later on (by appending <code class="code">
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--include bits/stdc++.h </code> to CXXFLAGS) when running the
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testsuite.
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</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
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specializations for certain types defined in the standard libraries.
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These types include <code class="classname">string</code> and dependents like
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<code class="classname">char_traits</code>, the templatized IO classes,
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<code class="classname">allocator</code>, and others.
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Disabling means that implicit
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template generation will be used when compiling these types. By
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default, this option is on. This option can change the library ABI.
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</p></dd><dt><span class="term"><code class="code">--disable-hosted-libstdcxx</code></span></dt><dd><p>
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By default, a complete <span class="emphasis"><em>hosted</em></span> C++ library is
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built. The C++ Standard also describes a
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<span class="emphasis"><em>freestanding</em></span> environment, in which only a
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minimal set of headers are provided. This option builds such an
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environment.
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</p></dd><dt><span class="term"><code class="code">--disable-libstdcxx-verbose</code></span></dt><dd><p>
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By default, the library is configured to write descriptive messages
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to standard error for certain events such as calling a pure virtual
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function or the invocation of the standard terminate handler. Those
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messages cause the library to depend on the demangler and standard I/O
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facilities, which might be undesirable in a low-memory environment or
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when standard error is not available. This option disables those
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messages. This option does not change the library ABI.
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</p></dd><dt><span class="term"><code class="code">--enable-vtable-verify</code>[default]</span></dt><dd><p>Use <code class="code">-fvtable-verify=std</code> to compile the C++
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runtime with instrumentation for vtable verification. All virtual
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||
functions in the standard library will be verified at runtime.
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||
Types impacted include <code class="classname">locale</code> and
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||
<code class="classname">iostream</code>, and others. Disabling means that
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the C++ runtime is compiled without support for vtable
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||
verification. By default, this option is off.
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||
</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> |