libstdc++-v3/docs/html/configopts.html

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   8    <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" />
   9    <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++" />
  10    <meta name="DESCRIPTION" content="Configuration options for libstdc++-v3." />
  11    <meta name="GENERATOR" content="vi and eight fingers" />
  12    <title>libstdc++-v3 configure options</title>
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  17
  18 <h1 class="centered"><a name="top">Interesting <code>configure</code>
  19 options</a></h1>
  20
  21 <p class="fineprint"><em>
  22    The latest version of this document is always available at
  23    <a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
  24    http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>.
  25 </em></p>
  26
  27 <p><em>
  28    To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
  29 </em></p>
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  32 <hr />
  33 <p>Here are some of the non-obvious options to libstdc++'s configure.
  34    Keep in mind that
  35    <!-- This SECnn should be the "Choosing Package Options" section. -->
  36    <a href="http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_node/autoconf_131.html#SEC131">they
  37    all have opposite forms as well</a>
  38    (enable/disable and with/without).  The defaults are for <strong>current
  39    development sources</strong>, which may be different than those for
  40    released versions.
  41 </p>
  42 <p>The canonical way to find out the configure options that are
  43    available for a given set of libstdc++ sources is to go to the
  44    source directory and then type:<code>  ./configure --help</code>
  45 </p>
  46
  47 <dl>
  48  <dt><code>--enable-multilib  </code>[default]</dt>
  49  <dd><p>This is part of the generic multilib support for building cross
  50         compilers.  As such, targets like &quot;powerpc-elf&quot; will have
  51         libstdc++ built many different ways:  &quot;-msoft-float&quot;
  52         and not, etc.  A different libstdc++ will be built for each of
  53         the different multilib versions.  This option is on by default.
  54      </p>
  55  </dd>
  56
  57  <dt><code>--enable-sjlj-exceptions  </code></dt>
  58  <dd><p>Forces old, set-jump/long-jump exception handling model.  If
  59         at all possible, the new, frame unwinding exception handling routines
  60         should be used instead, as they significantly reduce both
  61         runtime memory usage and executable size. This option can
  62         change the library ABI.
  63      </p>
  64  </dd>
  65
  66  <dt><code>--enable-version-specific-runtime-libs  </code></dt>
  67  <dd><p>Specify that run-time libraries should be installed in the
  68         compiler-specific subdirectory (i.e.,
  69         <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
  70         instead of <code>${libdir}</code>.  This option is useful if you
  71         intend to use several versions of gcc in parallel.  In addition,
  72         libstdc++'s include files will be installed in
  73         <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
  74         unless you also specify
  75        <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
  76      </p>
  77  </dd>
  78
  79  <dt><code>--with-gxx-include-dir=&lt;include-files dir&gt;</code></dt>
  80  <dd><p>Adds support for named libstdc++ include directory.  For instance,
  81         the following puts all the libstdc++ headers into a directory
  82         called &quot;2.97-20001008&quot; instead of the usual
  83         &quot;c++/(version)&quot;.
  84      </p>
  85         <pre>
  86    --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd>
  87
  88  <dt><code>--enable-cstdio  </code></dt>
  89  <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
  90         (described next). This option can change the library ABI.
  91      </p>
  92  </dd>
  93
  94  <dt><code>--enable-cstdio=OPTION  </code></dt>
  95  <dd><p>Select a target-specific I/O package. At the moment, the only
  96         choice is to use 'stdio', a generic &quot;C&quot; abstraction.
  97         The default is 'stdio'.  A longer explanation is <a
  98         href="explanations.html#cstdio">here</a>.
  99      </p>
 100  </dd>
 101
 102  <dt><code>--enable-clocale  </code></dt>
 103  <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
 104         (described next). This option can change the library ABI.
 105      </p>
 106  </dd>
 107
 108  <dt><code>--enable-clocale=OPTION  </code></dt>
 109  <dd><p>Select a target-specific underlying locale package.  The
 110         choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
 111         (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
 112         'gnu' to specify a model based on functionality from the GNU C
 113         library (langinfo/iconv/gettext) (from <a
 114         href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
 115         library), or 'generic' to use a generic &quot;C&quot;
 116         abstraction which consists of &quot;C&quot; locale info.
 117      </p>
 118
 119      <p>As part of the configuration process, the "C" library is
 120       probed both for sufficient vintage, and installed locale
 121       data. If either of these elements are not present, the C++
 122       locale model default to 'generic.' On glibc-based systems of
 123       version 2.2.5 and above with installed locale files, 'gnu' is
 124       automatically selected.
 125      </p>
 126  </dd>
 127
 128  <dt><code>--enable-libstdcxx-allocator  </code></dt>
 129  <dd><p>This is an abbreviated form of
 130         <code>'--enable-libstdcxx-allocator=auto'</code> (described
 131         next). This option can change the library ABI.
 132      </p>
 133  </dd>
 134
 135  <dt><code>--enable-libstdcxx-allocator=OPTION  </code></dt>
 136  <dd><p>Select a target-specific underlying std::allocator.  The
 137         choices are 'new' to specify a wrapper for new, 'malloc' to
 138         specify a wrapper for malloc, 'mt' for a fixed power of two allocator
 139         (<a href="ext/mt_allocator.html">documented</a> under extensions),
 140         'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator.
 141         This option can change the library ABI.
 142      </p>
 143  </dd>
 144
 145  <dt><code>--enable-cheaders=OPTION  </code></dt>
 146  <dd><p>This allows the user to define what kind of C headers are
 147         used.  Options are c and c_std.  These correspond to the source
 148         directory's include/c and include/c_std.  The default is c_std.
 149      </p>
 150  </dd>
 151
 152  <dt><code>--enable-threads  </code></dt>
 153  <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
 154         (described next). This option can change the library ABI.
 155      </p>
 156  </dd>
 157
 158  <dt><code>--enable-threads=OPTION  </code></dt>
 159  <dd><p>Select a threading library.  A full description is given in the
 160         general <a href="http://gcc.gnu.org/install/configure.html">compiler
 161         configuration instructions</a>.
 162      </p>
 163  </dd>
 164
 165  <dt><code>--enable-libstdcxx-debug  </code></dt>
 166  <dd><p>Build separate debug libraries in addition to what is normally built.
 167         By default, the debug libraries are compiled with
 168         <code> CXXFLAGS='-g3 -O0'</code>
 169         , are installed in <code>${libdir}/debug</code>, and have the
 170         same names and versioning information as the non-debug
 171         libraries. This option is off by default.
 172      </p>
 173      <p>Note this make command, executed in
 174         the build directory, will do much the same thing, without the
 175         configuration difference and without building everything twice:
 176         <code>make CXXFLAGS='-g3 -O0' all</code>
 177      </p>
 178  </dd>
 179
 180  <dt><code>--enable-libstdcxx-debug-flags=FLAGS</code></dt>
 181
 182  <dd><p>This option is only valid when <code> --enable-debug </code>
 183         is also specified, and applies to the debug builds only. With
 184         this option, you can pass a specific string of flags to the
 185         compiler to use when building the debug versions of libstdc++.
 186         FLAGS is a quoted string of options, like
 187      </p>
 188         <pre>
 189   --enable-libstdcxx-debug-flags='-g3 -O1 -gdwarf-2'</pre>
 190  </dd>
 191
 192  <dt><code>--enable-cxx-flags=FLAGS</code></dt>
 193  <dd><p>With this option, you can pass a string of -f (functionality)
 194         flags to the compiler to use when building libstdc++. This
 195         option can change the library ABI. FLAGS is a quoted string of
 196         options, like
 197      </p>
 198         <pre>
 199   --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre>
 200      <p>
 201         Note that the flags don't necessarily have to all be -f flags,
 202         as shown, but usually those are the ones that will make sense
 203         for experimentation and configure-time overriding.
 204      </p>
 205      <p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
 206         the 'make' environment is that, if files are automatically
 207         rebuilt, the same flags will be used when compiling those files
 208         as well, so that everything matches.
 209      </p>
 210      <p>Fun flags to try might include combinations of
 211      </p>
 212         <pre>
 213   -fstrict-aliasing
 214   -fno-exceptions
 215   -ffunction-sections
 216   -fvtable-gc</pre>
 217      <p>and opposite forms (-fno-) of the same.  Tell us (the libstdc++
 218         mailing list) if you discover more!
 219      </p>
 220  </dd>
 221
 222  <dt><code>--enable-c99  </code></dt>
 223  <dd><p>The &quot;long long&quot; type was introduced in C99, along
 224         with many other functions for wide characters, and math
 225         classification macros, etc.  If enabled, all C99 functions not
 226         specified by the C++ standard will be put into <code>namespace
 227         __gnu_cxx</code>, and then all these names will
 228         be injected into namespace std, so that C99 functions can be
 229         used &quot;as if&quot; they were in the C++ standard (as they
 230         will eventually be in some future revision of the standard,
 231         without a doubt).  By default, C99 support is on, assuming the
 232         configure probes find all the necessary functions and bits
 233         necessary. This option can change the library ABI.
 234     </p>
 235  </dd>
 236
 237  <dt><code>--enable-wchar_t  </code>[default]</dt>
 238  <dd><p>Template specializations for the &quot;wchar_t&quot; type are
 239         required for wide character conversion support.  Disabling
 240         wide character specializations may be expedient for initial
 241         porting efforts, but builds only a subset of what is required by
 242         ISO, and is not recommended.  By default, this option is on.
 243         This option can change the library ABI.
 244      </p>
 245  </dd>
 246
 247  <dt><code>--enable-long-long  </code></dt>
 248  <dd><p>The &quot;long long&quot; type was introduced in C99.  It is
 249         provided as a GNU extension to C++98 in g++.  This flag builds
 250         support for &quot;long long&quot; into the library (specialized
 251         templates and the like for iostreams).  This option is on by default:
 252         if enabled, users will have to either use the new-style &quot;C&quot;
 253         headers by default (i.e., &lt;cmath&gt; not &lt;math.h&gt;)
 254         or add appropriate compile-time flags to all compile lines to
 255         allow &quot;C&quot; visibility of this feature (on GNU/Linux,
 256         the flag is -D_ISOC99_SOURCE, which is added automatically via
 257         CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
 258         This option can change the library ABI.
 259      </p>
 260  </dd>
 261
 262  <dt><code>--enable-fully-dynamic-string  </code></dt>
 263  <dd><p>This option enables a special version of basic_string avoiding
 264         the optimization that allocates empty objects in static memory.
 265         Mostly useful together with shared memory allocators, see PR
 266         libstdc++/16612 for details.
 267      </p>
 268  </dd>
 269
 270  <dt><code>--enable-concept-checks  </code></dt>
 271  <dd><p>This turns on additional compile-time checks for instantiated
 272         library templates, in the form of specialized templates,
 273         <a href="19_diagnostics/howto.html#3">described here</a>.  They
 274         can help users discover when they break the rules of the STL, before
 275         their programs run.
 276      </p>
 277  </dd>
 278
 279  <dt><code>--enable-symvers[=style]  </code></dt>
 280
 281  <dd><p>In 3.1 and later, tries to turn on symbol versioning in the
 282         shared library (if a shared library has been
 283         requested). Values for 'style' that are currently supported
 284         are 'gnu', 'gnu-versioned-namespace', 'darwin', and
 285         'darwin-export'. Both gnu- options require that a recent
 286         version of the GNU linker be in use. Both darwin options are
 287         equivalent. With no style given, the configure script will try
 288         to guess correct defaults for the host system, probe to see if
 289         additional requirements are necessary and present for
 290         activation, and if so, will turn symbol versioning on. This
 291         option can change the library ABI.
 292      </p>
 293
 294  </dd>
 295
 296  <dt><code>--enable-libstdcxx-pch  </code></dt>
 297  <dd><p>In 3.4 and later, tries to turn on the generation of
 298         stdc++.h.gch, a pre-compiled file including all the standard
 299         C++ includes. If enabled (as by default), and the compiler
 300         seems capable of passing the simple sanity checks thrown at
 301         it, try to build stdc++.h.gch as part of the make process.
 302         In addition, this generated file is used later on (by appending <code>
 303         --include bits/stdc++.h </code> to CXXFLAGS) when running the
 304         testsuite.
 305      </p>
 306  </dd>
 307
 308  <dt><code>--disable-hosted-libstdcxx  </code></dt>
 309  <dd><p>By default, a complete <em>hosted</em> C++ library is built.  The
 310         C++ Standard also describes a <em>freestanding</em> environment,
 311         in which only a minimal set of headers are provided.  This option
 312         builds such an environment.
 313      </p>
 314  </dd>
 315 </dl>
 316 <p>Return <a href="#top">to the top of the page</a> or
 317    <a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>.
 318 </p>
 319
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 326 Comments and suggestions are welcome, and may be sent to
 327 <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
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