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

   1 <?xml version="1.0" encoding="ISO-8859-1"?>
   2 <!DOCTYPE html
   3           PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   4           "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
   5
   6 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
   7 <head>
   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>
  13 <link rel="StyleSheet" href="lib3styles.css" />
  14 </head>
  15 <body>
  16
  17 <h1 class="centered"><a name="top">Interesting <code>configure</code>
  18 options</a></h1>
  19
  20 <p class="fineprint"><em>
  21    The latest version of this document is always available at
  22    <a href="http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html">
  23    http://gcc.gnu.org/onlinedocs/libstdc++/configopts.html</a>.
  24 </em></p>
  25
  26 <p><em>
  27    To the <a href="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</a>.
  28 </em></p>
  29
  30 <!-- ####################################################### -->
  31 <hr />
  32 <p>Here are some of the non-obvious options to libstdc++'s configure.
  33    Keep in mind that
  34    <!-- This SECnn should be the "Choosing Package Options" section. -->
  35    <a href="http://www.gnu.org/manual/autoconf/html_node/Package-Options.html#Package%20Options">they
  36    all have opposite forms as well</a>
  37    (enable/disable and with/without).  The defaults are for current
  38    development sources.
  39 </p>
  40 <p>The canonical way to find out the configure options that are
  41    available for a given set of libstdc++ sources is to go to the
  42    source directory and then type:<code>  ./configure --help</code>
  43 </p>
  44
  45 <dl>
  46  <dt><code>--enable-multilib  </code>[default]</dt>
  47  <dd><p>This is part of the generic multilib support for building cross
  48         compilers.  As such, targets like &quot;powerpc-elf&quot; will have
  49         libstdc++ built many different ways:  &quot;-msoft-float&quot;
  50         and not, etc.  A different libstdc++ will be built for each of
  51         the different multilib versions.  This option is on by default.
  52      </p>
  53  </dd>
  54
  55  <dt><code>--enable-sjlj-exceptions  </code></dt>
  56  <dd><p>Forces old, set-jump/long-jump exception handling model.  If
  57         at all possible, the new, frame unwinding exception handling routines
  58         should be used instead, as they significantly reduce both
  59         runtime memory usage and executable size. This option can
  60         change the library ABI.
  61      </p>
  62  </dd>
  63
  64  <dt><code>--enable-version-specific-runtime-libs  </code></dt>
  65  <dd><p>Specify that run-time libraries should be installed in the
  66         compiler-specific subdirectory (i.e.,
  67         <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}</code>)
  68         instead of <code>${libdir}</code>.  This option is useful if you
  69         intend to use several versions of gcc in parallel.  In addition,
  70         libstdc++'s include files will be installed in
  71         <code>${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++</code>,
  72         unless you also specify
  73        <code>--with-gxx-include-dir=<em>dirname</em></code> during configuration.
  74      </p>
  75  </dd>
  76
  77  <dt><code>--with-gxx-include-dir=&lt;include-files dir&gt;</code></dt>
  78  <dd><p>Adds support for named libstdc++ include directory.  For instance,
  79         the following puts all the libstdc++ headers into a directory
  80         called &quot;2.97-20001008&quot; instead of the usual
  81         &quot;c++/(version)&quot;.
  82      </p>
  83         <pre>
  84    --with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/2.97-20001008</pre> </dd>
  85
  86  <dt><code>--enable-cstdio  </code></dt>
  87  <dd><p>This is an abbreviated form of <code>'--enable-cstdio=stdio'</code>
  88         (described next). This option can change the library ABI.
  89      </p>
  90  </dd>
  91
  92  <dt><code>--enable-cstdio=OPTION  </code></dt>
  93  <dd><p>Select a target-specific I/O package.  As of libstdc++-v3
  94         snapshot 3.0.96, the choices are 'libio' to specify the GNU
  95         I/O package (from
  96         <a href="http://sources.redhat.com/glibc/">glibc</a>, the
  97         GNU C library), or 'stdio' to use a generic &quot;C&quot;
  98         abstraction.  The default is 'stdio'.  A longer explanation
  99         is <a href="explanations.html#cstdio">here</a>.
 100      </p>
 101  </dd>
 102
 103  <dt><code>--enable-clocale  </code></dt>
 104  <dd><p>This is an abbreviated form of <code>'--enable-clocale=generic'</code>
 105         (described next). This option can change the library ABI.
 106      </p>
 107  </dd>
 108
 109  <dt><code>--enable-clocale=OPTION  </code></dt>
 110  <dd><p>Select a target-specific underlying locale package.  The
 111         choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix
 112         (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets,
 113         'gnu' to specify a model based on functionality from the GNU C
 114         library (langinfo/iconv/gettext) (from <a
 115         href="http://sources.redhat.com/glibc/">glibc</a>, the GNU C
 116         library), or 'generic' to use a generic &quot;C&quot;
 117         abstraction which consists of &quot;C&quot; locale info.
 118      </p>
 119
 120      <p>As part of the configuration process, the "C" library is
 121       probed both for sufficient vintage, and installed locale
 122       data. If either of these elements are not present, the C++
 123       locale model default to 'generic.' On glibc-based systems of
 124       version 2.2.5 and above with installed locale files, 'gnu' is
 125       automatically selected.
 126      </p>
 127  </dd>
 128
 129  <dt><code>--enable-cheaders=OPTION  </code></dt>
 130  <dd><p>This allows the user to define what kind of C headers are
 131         used.  Options are: c, c_std, and c_shadow. These correspond
 132         to the source directory's include/c, include/c_std, and
 133         include/c_shadow directories.  The default is c_std.
 134      </p>
 135  </dd>
 136
 137  <dt><code>--enable-threads  </code></dt>
 138  <dd><p>This is an abbreviated form of <code>'--enable-threads=yes'</code>
 139         (described next). This option can change the library ABI.
 140      </p>
 141  </dd>
 142
 143  <dt><code>--enable-threads=OPTION  </code></dt>
 144  <dd><p>Select a threading library.  A full description is given in the
 145         general <a href="http://gcc.gnu.org/install/configure.html">compiler
 146         configuration instructions</a>.
 147      </p>
 148  </dd>
 149
 150  <dt><code>--enable-debug  </code></dt>
 151  <dd><p>Build separate debug libraries in addition to what is normally built.
 152         By default, the debug libraries are compiled with
 153         <code> CXXFLAGS='-g3 -O0'</code>
 154         , are installed in <code>${libdir}/debug</code>, and have the
 155         same names and versioning information as the non-debug
 156         libraries. This option is off by default.
 157      </p>
 158      <p>Note this make command, executed in
 159         the build directory, will do much the same thing, without the
 160         configuration difference and without building everything twice:
 161         <code>make CXXFLAGS='-g3 -O0' all</code>
 162      </p>
 163  </dd>
 164
 165  <dt><code>--enable-debug-flags=FLAGS</code></dt>
 166
 167  <dd><p>This option is only valid when <code> --enable-debug </code>
 168         is also specified, and applies to the debug builds only. With
 169         this option, you can pass a specific string of flags to the
 170         compiler to use when building the debug versions of libstdc++.
 171         FLAGS is a quoted string of options, like
 172      </p>
 173         <pre>
 174   --enable-debug-flags='-g3 -O1 -gdwarf-2'</pre>
 175  </dd>
 176
 177  <dt><code>--enable-cxx-flags=FLAGS</code></dt>
 178  <dd><p>With this option, you can pass a string of -f (functionality)
 179         flags to the compiler to use when building libstdc++. This
 180         option can change the library ABI. FLAGS is a quoted string of
 181         options, like
 182      </p>
 183         <pre>
 184   --enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'</pre>
 185      <p>
 186         Note that the flags don't necessarily have to all be -f flags,
 187         as shown, but usually those are the ones that will make sense
 188         for experimentation and configure-time overriding.
 189      </p>
 190      <p>The advantage of --enable-cxx-flags over setting CXXFLAGS in
 191         the 'make' environment is that, if files are automatically
 192         rebuilt, the same flags will be used when compiling those files
 193         as well, so that everything matches.
 194      </p>
 195      <p>Fun flags to try might include combinations of
 196      </p>
 197         <pre>
 198   -fstrict-aliasing
 199   -fno-exceptions
 200   -ffunction-sections
 201   -fvtable-gc</pre>
 202      <p>and opposite forms (-fno-) of the same.  Tell us (the libstdc++
 203         mailing list) if you discover more!
 204      </p>
 205  </dd>
 206
 207  <dt><code>--enable-c99  </code></dt>
 208  <dd><p>The &quot;long long&quot; type was introduced in C99, along
 209         with many other functions for wide characters, and math
 210         classification macros, etc.  If enabled, all C99 functions not
 211         specified by the C++ standard will be put into <code>namespace
 212         __gnu_cxx</code>, and then all these names will
 213         be injected into namespace std, so that C99 functions can be
 214         used &quot;as if&quot; they were in the C++ standard (as they
 215         will eventually be in some future revision of the standard,
 216         without a doubt).  By default, C99 support is on, assuming the
 217         configure probes find all the necessary functions and bits
 218         necessary. This option can change the library ABI.
 219     </p>
 220  </dd>
 221
 222  <dt><code>--enable-c-mbchar  </code>[default]</dt>
 223  <dd><p>Certain template specializations are required for wide
 224         character conversion support.  This is tricky and currently
 225         changing rapidly, and can cause problems on new platforms.
 226         Disabling wide character specializations is useful for initial
 227         porting steps, but builds only a subset of what is required by
 228         ISO.  By default, this option is on.  This option can change
 229         the library ABI.
 230      </p>
 231  </dd>
 232
 233  <dt><code>--enable-long-long  </code></dt>
 234  <dd><p>The &quot;long long&quot; type was introduced in C99.  It is
 235         provided as a GNU extension to C++98 in g++.  This flag builds
 236         support for &quot;long long&quot; into the library (specialized
 237         templates and the like for iostreams).  This option is on by default:
 238         if enabled, users will have to either use the new-style &quot;C&quot;
 239         headers by default (i.e., &lt;cmath&gt; not &lt;math.h&gt;)
 240         or add appropriate compile-time flags to all compile lines to
 241         allow &quot;C&quot; visibility of this feature (on GNU/Linux,
 242         the flag is -D_ISOC99_SOURCE, which is added automatically via
 243         CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE).
 244         This option can change the library ABI.
 245      </p>
 246  </dd>
 247
 248  <dt><code>--enable-concept-checks  </code></dt>
 249  <dd><p>This turns on additional compile-time checks for instantiated
 250         library templates, in the form of specialized templates,
 251         <a href="19_diagnostics/howto.html#3">described here</a>.  They
 252         can help users discover when they break the rules of the STL, before
 253         their programs run.
 254      </p>
 255  </dd>
 256
 257  <dt><code>--enable-symvers[=style]  </code></dt>
 258  <dd><p>In 3.1 and later, tries to turn on symbol versioning in the
 259         shared library (if a shared library has been requested).  The
 260         only 'style' currently supported is 'gnu' which requires that
 261         a recent version of the GNU linker be in use.  With no style
 262         given, the configure script will try to guess if the 'gnu'
 263         style can be used, and if so, will turn it on.  Hopefully
 264         people will volunteer to do other 'style' options.
 265      </p>
 266  </dd>
 267 </dl>
 268 <p>Return <a href="#top">to the top of the page</a> or
 269    <a href="http://gcc.gnu.org/libstdc++/">to the libstdc++ homepage</a>.
 270 </p>
 271
 272
 273 <!-- ####################################################### -->
 274
 275 <hr />
 276 <p class="fineprint"><em>
 277 See <a href="17_intro/license.html">license.html</a> for copying conditions.
 278 Comments and suggestions are welcome, and may be sent to
 279 <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.
 280 </em></p>
 281
 282
 283 </body>
 284 </html>