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| 6 | <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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| 7 | <head>
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| 8 | <meta name="AUTHOR" content="[email protected] (Phil Edwards)" />
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| 9 | <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" />
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| 10 | <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3." />
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| 11 | <meta name="GENERATOR" content="vi and eight fingers" />
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| 12 | <title>libstdc++-v3 configure options</title>
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| 13 | <link rel="StyleSheet" href="lib3styles.css" />
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| 14 | </head>
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| 15 | <body>
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| 16 |
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| 17 | <h1 class="centered"><a name="top">Interesting <code>configure</code>
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| 18 | options</a></h1>
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| 19 |
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| 20 | <p class="fineprint"><em>
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| 21 | The latest version of this document is always available at
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| 22 | <a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
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| 23 | http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>.
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| 24 | </em></p>
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| 25 |
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| 26 | <p><em>
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| 27 | To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
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| 28 | </em></p>
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| 29 |
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| 30 | <!-- ####################################################### -->
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| 31 | <hr />
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| 32 | <p>Here are some of the non-obvious options to libstdc++'s configure.
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| 33 | Keep in mind that
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| 34 | <!-- This SECnn should be the "Choosing Package Options" section. -->
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| 35 | <a href="http://www.gnu.org/manual/autoconf/html_node/Package-Options.html#Package%20Options">they
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| 36 | all have opposite forms as well</a>
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| 37 | (enable/disable and with/without). The defaults are for current
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| 38 | development sources.
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| 39 | </p>
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| 40 | <p>The canonical way to find out the configure options that are
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| 41 | available for a given set of libstdc++ sources is to go to the
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| 42 | source directory and then type:<code> ./configure --help</code>
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| 43 | </p>
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| 44 |
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| 45 | <dl>
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| 46 | <dt><code>--enable-multilib </code>[default]</dt>
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| 47 | <dd><p>This is part of the generic multilib support for building cross
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| 48 | compilers. As such, targets like "powerpc-elf" will have
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| 49 | libstdc++ built many different ways: "-msoft-float"
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| 50 | and not, etc. A different libstdc++ will be built for each of
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| 51 | the different multilib versions. This option is on by default.
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| 52 | </p>
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| 53 | </dd>
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| 54 |
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| 55 | <dt><code>--enable-sjlj-exceptions </code></dt>
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| 56 | <dd><p>Forces old, set-jump/long-jump exception handling model. If
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| 57 | at all possible, the new, frame unwinding exception handling routines
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| 58 | should be used instead, as they significantly reduce both
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| 59 | runtime memory usage and executable size. This option can
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| 60 | change the library ABI.
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| 61 | </p>
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| 62 | </dd>
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| 63 |
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| 64 | <dt><code>--enable-version-specific-runtime-libs </code></dt>
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| 65 | <dd><p>Specify that run-time libraries should be installed in the
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| 66 | compiler-specific subdirectory (i.e.,
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| 67 | <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
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| 68 | instead of <code>${libdir}</code>. This option is useful if you
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| 69 | intend to use several versions of gcc in parallel. In addition,
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| 70 | libstdc++'s include files will be installed in
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| 71 | <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
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| 72 | unless you also specify
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| 73 | <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
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| 74 | </p>
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| 75 | </dd>
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| 76 |
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| 77 | <dt><code>--with-gxx-include-dir=<include-files dir></code></dt>
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| 78 | <dd><p>Adds support for named libstdc++ include directory. For instance,
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| 79 | the following puts all the libstdc++ headers into a directory
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| 80 | called "2.97-20001008" instead of the usual
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| 81 | "c++/(version)".
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| 82 | </p>
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| 83 | <pre>
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| 84 | --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd>
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| 85 |
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| 86 | <dt><code>--enable-cstdio </code></dt>
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| 87 | <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
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| 88 | (described next). This option can change the library ABI.
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| 89 | </p>
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| 90 | </dd>
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| 91 |
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| 92 | <dt><code>--enable-cstdio=OPTION </code></dt>
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| 93 | <dd><p>Select a target-specific I/O package. At the moment, the only
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| 94 | choice is to use 'stdio', a generic "C" abstraction.
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| 95 | The default is 'stdio'. A longer explanation is <a
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| 96 | href="explanations.html#cstdio">here</a>.
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| 97 | </p>
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| 98 | </dd>
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| 99 |
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| 100 | <dt><code>--enable-clocale </code></dt>
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| 101 | <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
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| 102 | (described next). This option can change the library ABI.
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| 103 | </p>
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| 104 | </dd>
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| 105 |
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| 106 | <dt><code>--enable-clocale=OPTION </code></dt>
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| 107 | <dd><p>Select a target-specific underlying locale package. The
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| 108 | choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
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| 109 | (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
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| 110 | 'gnu' to specify a model based on functionality from the GNU C
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| 111 | library (langinfo/iconv/gettext) (from <a
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| 112 | href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
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| 113 | library), or 'generic' to use a generic "C"
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| 114 | abstraction which consists of "C" locale info.
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| 115 | </p>
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| 116 |
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| 117 | <p>As part of the configuration process, the "C" library is
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| 118 | probed both for sufficient vintage, and installed locale
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| 119 | data. If either of these elements are not present, the C++
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| 120 | locale model default to 'generic.' On glibc-based systems of
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| 121 | version 2.2.5 and above with installed locale files, 'gnu' is
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| 122 | automatically selected.
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| 123 | </p>
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| 124 | </dd>
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| 125 |
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| 126 | <dt><code>--enable-cheaders=OPTION </code></dt>
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| 127 | <dd><p>This allows the user to define what kind of C headers are
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| 128 | used. Options are: c, c_std, and c_shadow. These correspond
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| 129 | to the source directory's include/c, include/c_std, and
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| 130 | include/c_shadow directories. The default is c_std.
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| 131 | </p>
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| 132 | </dd>
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| 133 |
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| 134 | <dt><code>--enable-threads </code></dt>
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| 135 | <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
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| 136 | (described next). This option can change the library ABI.
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| 137 | </p>
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| 138 | </dd>
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| 139 |
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| 140 | <dt><code>--enable-threads=OPTION </code></dt>
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| 141 | <dd><p>Select a threading library. A full description is given in the
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| 142 | general <a href="http://gcc.gnu.org/install/configure.html">compiler
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| 143 | configuration instructions</a>.
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| 144 | </p>
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| 145 | </dd>
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| 146 |
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| 147 | <dt><code>--enable-debug </code></dt>
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| 148 | <dd><p>Build separate debug libraries in addition to what is normally built.
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| 149 | By default, the debug libraries are compiled with
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| 150 | <code> CXXFLAGS='-g3 -O0'</code>
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| 151 | , are installed in <code>${libdir}/debug</code>, and have the
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| 152 | same names and versioning information as the non-debug
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| 153 | libraries. This option is off by default.
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| 154 | </p>
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| 155 | <p>Note this make command, executed in
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| 156 | the build directory, will do much the same thing, without the
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| 157 | configuration difference and without building everything twice:
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| 158 | <code>make CXXFLAGS='-g3 -O0' all</code>
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| 159 | </p>
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| 160 | </dd>
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| 161 |
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| 162 | <dt><code>--enable-debug-flags=FLAGS</code></dt>
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| 163 |
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| 164 | <dd><p>This option is only valid when <code> --enable-debug </code>
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| 165 | is also specified, and applies to the debug builds only. With
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| 166 | this option, you can pass a specific string of flags to the
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| 167 | compiler to use when building the debug versions of libstdc++.
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| 168 | FLAGS is a quoted string of options, like
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| 169 | </p>
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| 170 | <pre>
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| 171 | --enable-debug-flags='-g3 -O1 -gdwarf-2'</pre>
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| 172 | </dd>
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| 173 |
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| 174 | <dt><code>--enable-cxx-flags=FLAGS</code></dt>
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| 175 | <dd><p>With this option, you can pass a string of -f (functionality)
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| 176 | flags to the compiler to use when building libstdc++. This
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| 177 | option can change the library ABI. FLAGS is a quoted string of
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| 178 | options, like
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| 179 | </p>
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| 180 | <pre>
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| 181 | --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre>
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| 182 | <p>
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| 183 | Note that the flags don't necessarily have to all be -f flags,
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| 184 | as shown, but usually those are the ones that will make sense
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| 185 | for experimentation and configure-time overriding.
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| 186 | </p>
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| 187 | <p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
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| 188 | the 'make' environment is that, if files are automatically
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| 189 | rebuilt, the same flags will be used when compiling those files
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| 190 | as well, so that everything matches.
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| 191 | </p>
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| 192 | <p>Fun flags to try might include combinations of
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| 193 | </p>
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| 194 | <pre>
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| 195 | -fstrict-aliasing
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| 196 | -fno-exceptions
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| 197 | -ffunction-sections
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| 198 | -fvtable-gc</pre>
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| 199 | <p>and opposite forms (-fno-) of the same. Tell us (the libstdc++
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| 200 | mailing list) if you discover more!
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| 201 | </p>
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| 202 | </dd>
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| 203 |
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| 204 | <dt><code>--enable-c99 </code></dt>
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| 205 | <dd><p>The "long long" type was introduced in C99, along
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| 206 | with many other functions for wide characters, and math
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| 207 | classification macros, etc. If enabled, all C99 functions not
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| 208 | specified by the C++ standard will be put into <code>namespace
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| 209 | __gnu_cxx</code>, and then all these names will
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| 210 | be injected into namespace std, so that C99 functions can be
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| 211 | used "as if" they were in the C++ standard (as they
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| 212 | will eventually be in some future revision of the standard,
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| 213 | without a doubt). By default, C99 support is on, assuming the
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| 214 | configure probes find all the necessary functions and bits
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| 215 | necessary. This option can change the library ABI.
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| 216 | </p>
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| 217 | </dd>
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| 218 |
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| 219 | <dt><code>--enable-c-mbchar </code>[default]</dt>
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| 220 | <dd><p>Certain template specializations are required for wide
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| 221 | character conversion support. This is tricky and currently
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| 222 | changing rapidly, and can cause problems on new platforms.
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| 223 | Disabling wide character specializations is useful for initial
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| 224 | porting steps, but builds only a subset of what is required by
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| 225 | ISO. By default, this option is on. This option can change
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| 226 | the library ABI.
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| 227 | </p>
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| 228 | </dd>
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| 229 |
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| 230 | <dt><code>--enable-long-long </code></dt>
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| 231 | <dd><p>The "long long" type was introduced in C99. It is
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| 232 | provided as a GNU extension to C++98 in g++. This flag builds
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| 233 | support for "long long" into the library (specialized
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| 234 | templates and the like for iostreams). This option is on by default:
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| 235 | if enabled, users will have to either use the new-style "C"
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| 236 | headers by default (i.e., <cmath> not <math.h>)
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| 237 | or add appropriate compile-time flags to all compile lines to
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| 238 | allow "C" visibility of this feature (on GNU/Linux,
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| 239 | the flag is -D_ISOC99_SOURCE, which is added automatically via
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| 240 | CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
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| 241 | This option can change the library ABI.
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| 242 | </p>
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| 243 | </dd>
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| 244 |
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| 245 | <dt><code>--enable-concept-checks </code></dt>
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| 246 | <dd><p>This turns on additional compile-time checks for instantiated
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| 247 | library templates, in the form of specialized templates,
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| 248 | <a href="19_diagnostics/howto.html#3">described here</a>. They
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| 249 | can help users discover when they break the rules of the STL, before
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| 250 | their programs run.
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| 251 | </p>
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| 252 | </dd>
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| 253 |
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| 254 | <dt><code>--enable-symvers[=style] </code></dt>
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| 255 | <dd><p>In 3.1 and later, tries to turn on symbol versioning in the
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| 256 | shared library (if a shared library has been requested). The
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| 257 | only 'style' currently supported is 'gnu' which requires that
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| 258 | a recent version of the GNU linker be in use. With no style
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| 259 | given, the configure script will try to guess if the 'gnu'
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| 260 | style can be used, and if so, will turn it on. Hopefully
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| 261 | people will volunteer to do other 'style' options.
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| 262 | </p>
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| 263 | </dd>
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| 264 | </dl>
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| 265 | <p>Return <a href="#top">to the top of the page</a> or
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| 266 | <a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>.
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| 267 | </p>
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| 268 |
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| 269 |
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| 270 | <!-- ####################################################### -->
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| 271 |
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| 272 | <hr />
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| 273 | <p class="fineprint"><em>
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| 274 | See <a href="17_intro/license.html">license.html</a> for copying conditions.
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| 275 | Comments and suggestions are welcome, and may be sent to
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| 276 | <a href="mailto:[email protected]">the libstdc++ mailing list</a>.
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| 277 | </em></p>
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| 278 |
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| 279 |
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| 280 | </body>
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| 281 | </html>
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