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<title>Installing GCC: Configuration</title>
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<h1 class="settitle">Installing GCC: Configuration</h1>
<a name="index-Configuration-1"></a><a name="index-Installing-GCC_003a-Configuration-2"></a>
Like most GNU software, GCC must be configured before it can be built. 
This document describes the recommended configuration procedure
for both native and cross targets.

   <p>We use <var>srcdir</var> to refer to the toplevel source directory for
GCC; we use <var>objdir</var> to refer to the toplevel build/object directory.

   <p>If you obtained the sources via SVN, <var>srcdir</var> must refer to the top
<samp><span class="file">gcc</span></samp> directory, the one where the <samp><span class="file">MAINTAINERS</span></samp> file can be
found, and not its <samp><span class="file">gcc</span></samp> subdirectory, otherwise the build will fail.

   <p>If either <var>srcdir</var> or <var>objdir</var> is located on an automounted NFS
file system, the shell's built-in <samp><span class="command">pwd</span></samp> command will return
temporary pathnames.  Using these can lead to various sorts of build
problems.  To avoid this issue, set the <samp><span class="env">PWDCMD</span></samp> environment
variable to an automounter-aware <samp><span class="command">pwd</span></samp> command, e.g.,
<samp><span class="command">pawd</span></samp> or &lsquo;<samp><span class="samp">amq -w</span></samp>&rsquo;, during the configuration and build
phases.

   <p>First, we <strong>highly</strong> recommend that GCC be built into a
separate directory from the sources which does <strong>not</strong> reside
within the source tree.  This is how we generally build GCC; building
where <var>srcdir</var> == <var>objdir</var> should still work, but doesn't
get extensive testing; building where <var>objdir</var> is a subdirectory
of <var>srcdir</var> is unsupported.

   <p>If you have previously built GCC in the same directory for a
different target machine, do &lsquo;<samp><span class="samp">make distclean</span></samp>&rsquo; to delete all files
that might be invalid.  One of the files this deletes is <samp><span class="file">Makefile</span></samp>;
if &lsquo;<samp><span class="samp">make distclean</span></samp>&rsquo; complains that <samp><span class="file">Makefile</span></samp> does not exist
or issues a message like &ldquo;don't know how to make distclean&rdquo; it probably
means that the directory is already suitably clean.  However, with the
recommended method of building in a separate <var>objdir</var>, you should
simply use a different <var>objdir</var> for each target.

   <p>Second, when configuring a native system, either <samp><span class="command">cc</span></samp> or
<samp><span class="command">gcc</span></samp> must be in your path or you must set <samp><span class="env">CC</span></samp> in
your environment before running configure.  Otherwise the configuration
scripts may fail.

   <p>To configure GCC:

<pre class="smallexample">     % mkdir <var>objdir</var>
     % cd <var>objdir</var>
     % <var>srcdir</var>/configure [<var>options</var>] [<var>target</var>]
</pre>
   <h3 class="heading"><a name="TOC0"></a>Distributor options</h3>

<p>If you will be distributing binary versions of GCC, with modifications
to the source code, you should use the options described in this
section to make clear that your version contains modifications.

     <dl>
<dt><code>--with-pkgversion=</code><var>version</var><dd>Specify a string that identifies your package.  You may wish
to include a build number or build date.  This version string will be
included in the output of <samp><span class="command">gcc --version</span></samp>.  This suffix does
not replace the default version string, only the &lsquo;<samp><span class="samp">GCC</span></samp>&rsquo; part.

     <p>The default value is &lsquo;<samp><span class="samp">GCC</span></samp>&rsquo;.

     <br><dt><code>--with-bugurl=</code><var>url</var><dd>Specify the URL that users should visit if they wish to report a bug. 
You are of course welcome to forward bugs reported to you to the FSF,
if you determine that they are not bugs in your modifications.

     <p>The default value refers to the FSF's GCC bug tracker.

   </dl>

<h3 class="heading"><a name="TOC1"></a>Target specification</h3>

     <ul>
<li>GCC has code to correctly determine the correct value for <var>target</var>
for nearly all native systems.  Therefore, we highly recommend you do
not provide a configure target when configuring a native compiler.

     <li><var>target</var> must be specified as <samp><span class="option">--target=</span><var>target</var></samp>
when configuring a cross compiler; examples of valid targets would be
m68k-elf, sh-elf, etc.

     <li>Specifying just <var>target</var> instead of <samp><span class="option">--target=</span><var>target</var></samp>
implies that the host defaults to <var>target</var>. 
</ul>

<h3 class="heading"><a name="TOC2"></a>Options specification</h3>

<p>Use <var>options</var> to override several configure time options for
GCC.  A list of supported <var>options</var> follows; &lsquo;<samp><span class="samp">configure
--help</span></samp>&rsquo; may list other options, but those not listed below may not
work and should not normally be used.

   <p>Note that each <samp><span class="option">--enable</span></samp> option has a corresponding
<samp><span class="option">--disable</span></samp> option and that each <samp><span class="option">--with</span></samp> option has a
corresponding <samp><span class="option">--without</span></samp> option.

     <dl>
<dt><code>--prefix=</code><var>dirname</var><dd>Specify the toplevel installation
directory.  This is the recommended way to install the tools into a directory
other than the default.  The toplevel installation directory defaults to
<samp><span class="file">/usr/local</span></samp>.

     <p>We <strong>highly</strong> recommend against <var>dirname</var> being the same or a
subdirectory of <var>objdir</var> or vice versa.  If specifying a directory
beneath a user's home directory tree, some shells will not expand
<var>dirname</var> correctly if it contains the &lsquo;<samp><span class="samp">~</span></samp>&rsquo; metacharacter; use
<samp><span class="env">$HOME</span></samp> instead.

     <p>The following standard <samp><span class="command">autoconf</span></samp> options are supported.  Normally you
should not need to use these options.
          <dl>
<dt><code>--exec-prefix=</code><var>dirname</var><dd>Specify the toplevel installation directory for architecture-dependent
files.  The default is <samp><var>prefix</var></samp>.

          <br><dt><code>--bindir=</code><var>dirname</var><dd>Specify the installation directory for the executables called by users
(such as <samp><span class="command">gcc</span></samp> and <samp><span class="command">g++</span></samp>).  The default is
<samp><var>exec-prefix</var><span class="file">/bin</span></samp>.

          <br><dt><code>--libdir=</code><var>dirname</var><dd>Specify the installation directory for object code libraries and
internal data files of GCC.  The default is <samp><var>exec-prefix</var><span class="file">/lib</span></samp>.

          <br><dt><code>--libexecdir=</code><var>dirname</var><dd>Specify the installation directory for internal executables of GCC. 
The default is <samp><var>exec-prefix</var><span class="file">/libexec</span></samp>.

          <br><dt><code>--with-slibdir=</code><var>dirname</var><dd>Specify the installation directory for the shared libgcc library.  The
default is <samp><var>libdir</var></samp>.

          <br><dt><code>--datarootdir=</code><var>dirname</var><dd>Specify the root of the directory tree for read-only architecture-independent
data files referenced by GCC.  The default is <samp><var>prefix</var><span class="file">/share</span></samp>.

          <br><dt><code>--infodir=</code><var>dirname</var><dd>Specify the installation directory for documentation in info format. 
The default is <samp><var>datarootdir</var><span class="file">/info</span></samp>.

          <br><dt><code>--datadir=</code><var>dirname</var><dd>Specify the installation directory for some architecture-independent
data files referenced by GCC.  The default is <samp><var>datarootdir</var></samp>.

          <br><dt><code>--docdir=</code><var>dirname</var><dd>Specify the installation directory for documentation files (other
than Info) for GCC.  The default is <samp><var>datarootdir</var><span class="file">/doc</span></samp>.

          <br><dt><code>--htmldir=</code><var>dirname</var><dd>Specify the installation directory for HTML documentation files. 
The default is <samp><var>docdir</var></samp>.

          <br><dt><code>--pdfdir=</code><var>dirname</var><dd>Specify the installation directory for PDF documentation files. 
The default is <samp><var>docdir</var></samp>.

          <br><dt><code>--mandir=</code><var>dirname</var><dd>Specify the installation directory for manual pages.  The default is
<samp><var>datarootdir</var><span class="file">/man</span></samp>.  (Note that the manual pages are only extracts
from the full GCC manuals, which are provided in Texinfo format.  The manpages
are derived by an automatic conversion process from parts of the full
manual.)

          <br><dt><code>--with-gxx-include-dir=</code><var>dirname</var><dd>Specify
the installation directory for G++ header files.  The default depends
on other configuration options, and differs between cross and native
configurations.

          <br><dt><code>--with-specs=</code><var>specs</var><dd>Specify additional command line driver SPECS. 
This can be useful if you need to turn on a non-standard feature by
default without modifying the compiler's source code, for instance
<samp><span class="option">--with-specs=%{!fcommon:%{!fno-common:-fno-common}}</span></samp>. 
See &ldquo;Spec Files&rdquo; in the main manual

     </dl>

     <br><dt><code>--program-prefix=</code><var>prefix</var><dd>GCC supports some transformations of the names of its programs when
installing them.  This option prepends <var>prefix</var> to the names of
programs to install in <var>bindir</var> (see above).  For example, specifying
<samp><span class="option">--program-prefix=foo-</span></samp> would result in &lsquo;<samp><span class="samp">gcc</span></samp>&rsquo;
being installed as <samp><span class="file">/usr/local/bin/foo-gcc</span></samp>.

     <br><dt><code>--program-suffix=</code><var>suffix</var><dd>Appends <var>suffix</var> to the names of programs to install in <var>bindir</var>
(see above).  For example, specifying <samp><span class="option">--program-suffix=-3.1</span></samp>
would result in &lsquo;<samp><span class="samp">gcc</span></samp>&rsquo; being installed as
<samp><span class="file">/usr/local/bin/gcc-3.1</span></samp>.

     <br><dt><code>--program-transform-name=</code><var>pattern</var><dd>Applies the &lsquo;<samp><span class="samp">sed</span></samp>&rsquo; script <var>pattern</var> to be applied to the names
of programs to install in <var>bindir</var> (see above).  <var>pattern</var> has to
consist of one or more basic &lsquo;<samp><span class="samp">sed</span></samp>&rsquo; editing commands, separated by
semicolons.  For example, if you want the &lsquo;<samp><span class="samp">gcc</span></samp>&rsquo; program name to be
transformed to the installed program <samp><span class="file">/usr/local/bin/myowngcc</span></samp> and
the &lsquo;<samp><span class="samp">g++</span></samp>&rsquo; program name to be transformed to
<samp><span class="file">/usr/local/bin/gspecial++</span></samp> without changing other program names,
you could use the pattern
<samp><span class="option">--program-transform-name='s/^gcc$/myowngcc/; s/^g++$/gspecial++/'</span></samp>
to achieve this effect.

     <p>All three options can be combined and used together, resulting in more
complex conversion patterns.  As a basic rule, <var>prefix</var> (and
<var>suffix</var>) are prepended (appended) before further transformations
can happen with a special transformation script <var>pattern</var>.

     <p>As currently implemented, this option only takes effect for native
builds; cross compiler binaries' names are not transformed even when a
transformation is explicitly asked for by one of these options.

     <p>For native builds, some of the installed programs are also installed
with the target alias in front of their name, as in
&lsquo;<samp><span class="samp">i686-pc-linux-gnu-gcc</span></samp>&rsquo;.  All of the above transformations happen
before the target alias is prepended to the name&mdash;so, specifying
<samp><span class="option">--program-prefix=foo-</span></samp> and <samp><span class="option">program-suffix=-3.1</span></samp>, the
resulting binary would be installed as
<samp><span class="file">/usr/local/bin/i686-pc-linux-gnu-foo-gcc-3.1</span></samp>.

     <p>As a last shortcoming, none of the installed Ada programs are
transformed yet, which will be fixed in some time.

     <br><dt><code>--with-local-prefix=</code><var>dirname</var><dd>Specify the
installation directory for local include files.  The default is
<samp><span class="file">/usr/local</span></samp>.  Specify this option if you want the compiler to
search directory <samp><var>dirname</var><span class="file">/include</span></samp> for locally installed
header files <em>instead</em> of <samp><span class="file">/usr/local/include</span></samp>.

     <p>You should specify <samp><span class="option">--with-local-prefix</span></samp> <strong>only</strong> if your
site has a different convention (not <samp><span class="file">/usr/local</span></samp>) for where to put
site-specific files.

     <p>The default value for <samp><span class="option">--with-local-prefix</span></samp> is <samp><span class="file">/usr/local</span></samp>
regardless of the value of <samp><span class="option">--prefix</span></samp>.  Specifying
<samp><span class="option">--prefix</span></samp> has no effect on which directory GCC searches for
local header files.  This may seem counterintuitive, but actually it is
logical.

     <p>The purpose of <samp><span class="option">--prefix</span></samp> is to specify where to <em>install
GCC</em>.  The local header files in <samp><span class="file">/usr/local/include</span></samp>&mdash;if you put
any in that directory&mdash;are not part of GCC.  They are part of other
programs&mdash;perhaps many others.  (GCC installs its own header files in
another directory which is based on the <samp><span class="option">--prefix</span></samp> value.)

     <p>Both the local-prefix include directory and the GCC-prefix include
directory are part of GCC's &ldquo;system include&rdquo; directories.  Although these
two directories are not fixed, they need to be searched in the proper
order for the correct processing of the include_next directive.  The
local-prefix include directory is searched before the GCC-prefix
include directory.  Another characteristic of system include directories
is that pedantic warnings are turned off for headers in these directories.

     <p>Some autoconf macros add <samp><span class="option">-I </span><var>directory</var></samp> options to the
compiler command line, to ensure that directories containing installed
packages' headers are searched.  When <var>directory</var> is one of GCC's
system include directories, GCC will ignore the option so that system
directories continue to be processed in the correct order.  This
may result in a search order different from what was specified but the
directory will still be searched.

     <p>GCC automatically searches for ordinary libraries using
<samp><span class="env">GCC_EXEC_PREFIX</span></samp>.  Thus, when the same installation prefix is
used for both GCC and packages, GCC will automatically search for
both headers and libraries.  This provides a configuration that is
easy to use.  GCC behaves in a manner similar to that when it is
installed as a system compiler in <samp><span class="file">/usr</span></samp>.

     <p>Sites that need to install multiple versions of GCC may not want to
use the above simple configuration.  It is possible to use the
<samp><span class="option">--program-prefix</span></samp>, <samp><span class="option">--program-suffix</span></samp> and
<samp><span class="option">--program-transform-name</span></samp> options to install multiple versions
into a single directory, but it may be simpler to use different prefixes
and the <samp><span class="option">--with-local-prefix</span></samp> option to specify the location of the
site-specific files for each version.  It will then be necessary for
users to specify explicitly the location of local site libraries
(e.g., with <samp><span class="env">LIBRARY_PATH</span></samp>).

     <p>The same value can be used for both <samp><span class="option">--with-local-prefix</span></samp> and
<samp><span class="option">--prefix</span></samp> provided it is not <samp><span class="file">/usr</span></samp>.  This can be used
to avoid the default search of <samp><span class="file">/usr/local/include</span></samp>.

     <p><strong>Do not</strong> specify <samp><span class="file">/usr</span></samp> as the <samp><span class="option">--with-local-prefix</span></samp>! 
The directory you use for <samp><span class="option">--with-local-prefix</span></samp> <strong>must not</strong>
contain any of the system's standard header files.  If it did contain
them, certain programs would be miscompiled (including GNU Emacs, on
certain targets), because this would override and nullify the header
file corrections made by the <samp><span class="command">fixincludes</span></samp> script.

     <p>Indications are that people who use this option use it based on mistaken
ideas of what it is for.  People use it as if it specified where to
install part of GCC.  Perhaps they make this assumption because
installing GCC creates the directory.

     <br><dt><code>--with-native-system-header-dir=</code><var>dirname</var><dd>Specifies that <var>dirname</var> is the directory that contains native system
header files, rather than <samp><span class="file">/usr/include</span></samp>.  This option is most useful
if you are creating a compiler that should be isolated from the system
as much as possible.  It is most commonly used with the
<samp><span class="option">--with-sysroot</span></samp> option and will cause GCC to search
<var>dirname</var> inside the system root specified by that option.

     <br><dt><code>--enable-shared[=</code><var>package</var><code>[,...]]</code><dd>Build shared versions of libraries, if shared libraries are supported on
the target platform.  Unlike GCC 2.95.x and earlier, shared libraries
are enabled by default on all platforms that support shared libraries.

     <p>If a list of packages is given as an argument, build shared libraries
only for the listed packages.  For other packages, only static libraries
will be built.  Package names currently recognized in the GCC tree are
&lsquo;<samp><span class="samp">libgcc</span></samp>&rsquo; (also known as &lsquo;<samp><span class="samp">gcc</span></samp>&rsquo;), &lsquo;<samp><span class="samp">libstdc++</span></samp>&rsquo; (not
&lsquo;<samp><span class="samp">libstdc++-v3</span></samp>&rsquo;), &lsquo;<samp><span class="samp">libffi</span></samp>&rsquo;, &lsquo;<samp><span class="samp">zlib</span></samp>&rsquo;, &lsquo;<samp><span class="samp">boehm-gc</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">ada</span></samp>&rsquo;, &lsquo;<samp><span class="samp">libada</span></samp>&rsquo;, &lsquo;<samp><span class="samp">libjava</span></samp>&rsquo;, &lsquo;<samp><span class="samp">libgo</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">libobjc</span></samp>&rsquo;. 
Note &lsquo;<samp><span class="samp">libiberty</span></samp>&rsquo; does not support shared libraries at all.

     <p>Use <samp><span class="option">--disable-shared</span></samp> to build only static libraries.  Note that
<samp><span class="option">--disable-shared</span></samp> does not accept a list of package names as
argument, only <samp><span class="option">--enable-shared</span></samp> does.

     <p>Contrast with <samp><span class="option">--enable-host-shared</span></samp>, which affects <em>host</em>
code.

     <br><dt><code>--enable-host-shared</code><dd>Specify that the <em>host</em> code should be built into position-independent
machine code (with -fPIC), allowing it to be used within shared libraries,
but yielding a slightly slower compiler.

     <p>This option is required when building the libgccjit.so library.

     <p>Contrast with <samp><span class="option">--enable-shared</span></samp>, which affects <em>target</em>
libraries.

     <br><dt><code><a name="with_002dgnu_002das"></a>--with-gnu-as</code><dd>Specify that the compiler should assume that the
assembler it finds is the GNU assembler.  However, this does not modify
the rules to find an assembler and will result in confusion if the
assembler found is not actually the GNU assembler.  (Confusion may also
result if the compiler finds the GNU assembler but has not been
configured with <samp><span class="option">--with-gnu-as</span></samp>.)  If you have more than one
assembler installed on your system, you may want to use this option in
connection with <samp><span class="option">--with-as=</span><var>pathname</var></samp> or
<samp><span class="option">--with-build-time-tools=</span><var>pathname</var></samp>.

     <p>The following systems are the only ones where it makes a difference
whether you use the GNU assembler.  On any other system,
<samp><span class="option">--with-gnu-as</span></samp> has no effect.

          <ul>
<li>&lsquo;<samp><span class="samp">hppa1.0-</span><var>any</var><span class="samp">-</span><var>any</var></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">hppa1.1-</span><var>any</var><span class="samp">-</span><var>any</var></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">sparc-sun-solaris2.</span><var>any</var></samp>&rsquo;
<li>&lsquo;<samp><span class="samp">sparc64-</span><var>any</var><span class="samp">-solaris2.</span><var>any</var></samp>&rsquo;
</ul>

     <br><dt><code><a name="with_002das"></a>--with-as=</code><var>pathname</var><dd>Specify that the compiler should use the assembler pointed to by
<var>pathname</var>, rather than the one found by the standard rules to find
an assembler, which are:
          <ul>
<li>Unless GCC is being built with a cross compiler, check the
<samp><var>libexec</var><span class="file">/gcc/</span><var>target</var><span class="file">/</span><var>version</var></samp> directory. 
<var>libexec</var> defaults to <samp><var>exec-prefix</var><span class="file">/libexec</span></samp>;
<var>exec-prefix</var> defaults to <var>prefix</var>, which
defaults to <samp><span class="file">/usr/local</span></samp> unless overridden by the
<samp><span class="option">--prefix=</span><var>pathname</var></samp> switch described above.  <var>target</var>
is the target system triple, such as &lsquo;<samp><span class="samp">sparc-sun-solaris2.7</span></samp>&rsquo;, and
<var>version</var> denotes the GCC version, such as 3.0.

          <li>If the target system is the same that you are building on, check
operating system specific directories (e.g. <samp><span class="file">/usr/ccs/bin</span></samp> on
Sun Solaris 2).

          <li>Check in the <samp><span class="env">PATH</span></samp> for a tool whose name is prefixed by the
target system triple.

          <li>Check in the <samp><span class="env">PATH</span></samp> for a tool whose name is not prefixed by the
target system triple, if the host and target system triple are
the same (in other words, we use a host tool if it can be used for
the target as well). 
</ul>

     <p>You may want to use <samp><span class="option">--with-as</span></samp> if no assembler
is installed in the directories listed above, or if you have multiple
assemblers installed and want to choose one that is not found by the
above rules.

     <br><dt><code><a name="with_002dgnu_002dld"></a>--with-gnu-ld</code><dd>Same as <a href="#with-gnu-as"><samp><span class="option">--with-gnu-as</span></samp></a>
but for the linker.

     <br><dt><code>--with-ld=</code><var>pathname</var><dd>Same as <a href="#with-as"><samp><span class="option">--with-as</span></samp></a>
but for the linker.

     <br><dt><code>--with-stabs</code><dd>Specify that stabs debugging
information should be used instead of whatever format the host normally
uses.  Normally GCC uses the same debug format as the host system.

     <p>On MIPS based systems and on Alphas, you must specify whether you want
GCC to create the normal ECOFF debugging format, or to use BSD-style
stabs passed through the ECOFF symbol table.  The normal ECOFF debug
format cannot fully handle languages other than C.  BSD stabs format can
handle other languages, but it only works with the GNU debugger GDB.

     <p>Normally, GCC uses the ECOFF debugging format by default; if you
prefer BSD stabs, specify <samp><span class="option">--with-stabs</span></samp> when you configure GCC.

     <p>No matter which default you choose when you configure GCC, the user
can use the <samp><span class="option">-gcoff</span></samp> and <samp><span class="option">-gstabs+</span></samp> options to specify explicitly
the debug format for a particular compilation.

     <p><samp><span class="option">--with-stabs</span></samp> is meaningful on the ISC system on the 386, also, if
<samp><span class="option">--with-gas</span></samp> is used.  It selects use of stabs debugging
information embedded in COFF output.  This kind of debugging information
supports C++ well; ordinary COFF debugging information does not.

     <p><samp><span class="option">--with-stabs</span></samp> is also meaningful on 386 systems running SVR4.  It
selects use of stabs debugging information embedded in ELF output.  The
C++ compiler currently (2.6.0) does not support the DWARF debugging
information normally used on 386 SVR4 platforms; stabs provide a
workable alternative.  This requires gas and gdb, as the normal SVR4
tools can not generate or interpret stabs.

     <br><dt><code>--with-tls=</code><var>dialect</var><dd>Specify the default TLS dialect, for systems were there is a choice. 
For ARM targets, possible values for <var>dialect</var> are <code>gnu</code> or
<code>gnu2</code>, which select between the original GNU dialect and the GNU TLS
descriptor-based dialect.

     <br><dt><code>--enable-multiarch</code><dd>Specify whether to enable or disable multiarch support.  The default is
to check for glibc start files in a multiarch location, and enable it
if the files are found.  The auto detection is enabled for native builds,
and for cross builds configured with <samp><span class="option">--with-sysroot</span></samp>, and without
<samp><span class="option">--with-native-system-header-dir</span></samp>. 
More documentation about multiarch can be found at
<a href="http://wiki.debian.org/Multiarch">http://wiki.debian.org/Multiarch</a>.

     <br><dt><code>--enable-vtable-verify</code><dd>Specify whether to enable or disable the vtable verification feature. 
Enabling this feature causes libstdc++ to be built with its virtual calls
in verifiable mode.  This means that, when linked with libvtv, every
virtual call in libstdc++ will verify the vtable pointer through which the
call will be made before actually making the call.  If not linked with libvtv,
the verifier will call stub functions (in libstdc++ itself) and do nothing. 
If vtable verification is disabled, then libstdc++ is not built with its
virtual calls in verifiable mode at all.  However the libvtv library will
still be built (see <samp><span class="option">--disable-libvtv</span></samp> to turn off building libvtv). 
<samp><span class="option">--disable-vtable-verify</span></samp> is the default.

     <br><dt><code>--disable-multilib</code><dd>Specify that multiple target
libraries to support different target variants, calling
conventions, etc. should not be built.  The default is to build a
predefined set of them.

     <p>Some targets provide finer-grained control over which multilibs are built
(e.g., <samp><span class="option">--disable-softfloat</span></samp>):
          <dl>
<dt><code>arm-*-*</code><dd>fpu, 26bit, underscore, interwork, biendian, nofmult.

          <br><dt><code>m68*-*-*</code><dd>softfloat, m68881, m68000, m68020.

          <br><dt><code>mips*-*-*</code><dd>single-float, biendian, softfloat.

          <br><dt><code>powerpc*-*-*, rs6000*-*-*</code><dd>aix64, pthread, softfloat, powercpu, powerpccpu, powerpcos, biendian,
sysv, aix.

     </dl>

     <br><dt><code>--with-multilib-list=</code><var>list</var><dt><code>--without-multilib-list</code><dd>Specify what multilibs to build. 
Currently only implemented for sh*-*-* and x86-64-*-linux*.

          <dl>
<dt><code>sh*-*-*</code><dd><var>list</var> is a comma separated list of CPU names.  These must be of the
form <code>sh*</code> or <code>m*</code> (in which case they match the compiler option
for that processor).  The list should not contain any endian options -
these are handled by <samp><span class="option">--with-endian</span></samp>.

          <p>If <var>list</var> is empty, then there will be no multilibs for extra
processors.  The multilib for the secondary endian remains enabled.

          <p>As a special case, if an entry in the list starts with a <code>!</code>
(exclamation point), then it is added to the list of excluded multilibs. 
Entries of this sort should be compatible with &lsquo;<samp><span class="samp">MULTILIB_EXCLUDES</span></samp>&rsquo;
(once the leading <code>!</code> has been stripped).

          <p>If <samp><span class="option">--with-multilib-list</span></samp> is not given, then a default set of
multilibs is selected based on the value of <samp><span class="option">--target</span></samp>.  This is
usually the complete set of libraries, but some targets imply a more
specialized subset.

          <p>Example 1: to configure a compiler for SH4A only, but supporting both
endians, with little endian being the default:
          <pre class="smallexample">               --with-cpu=sh4a --with-endian=little,big --with-multilib-list=
</pre>
          <p>Example 2: to configure a compiler for both SH4A and SH4AL-DSP, but with
only little endian SH4AL:
          <pre class="smallexample">               --with-cpu=sh4a --with-endian=little,big \
               --with-multilib-list=sh4al,!mb/m4al
</pre>
          <br><dt><code>x86-64-*-linux*</code><dd><var>list</var> is a comma separated list of <code>m32</code>, <code>m64</code> and
<code>mx32</code> to enable 32-bit, 64-bit and x32 run-time libraries,
respectively.  If <var>list</var> is empty, then there will be no multilibs
and only the default run-time library will be enabled.

          <p>If <samp><span class="option">--with-multilib-list</span></samp> is not given, then only 32-bit and
64-bit run-time libraries will be enabled. 
</dl>

     <br><dt><code>--with-endian=</code><var>endians</var><dd>Specify what endians to use. 
Currently only implemented for sh*-*-*.

     <p><var>endians</var> may be one of the following:
          <dl>
<dt><code>big</code><dd>Use big endian exclusively. 
<br><dt><code>little</code><dd>Use little endian exclusively. 
<br><dt><code>big,little</code><dd>Use big endian by default.  Provide a multilib for little endian. 
<br><dt><code>little,big</code><dd>Use little endian by default.  Provide a multilib for big endian. 
</dl>

     <br><dt><code>--enable-threads</code><dd>Specify that the target
supports threads.  This affects the Objective-C compiler and runtime
library, and exception handling for other languages like C++ and Java. 
On some systems, this is the default.

     <p>In general, the best (and, in many cases, the only known) threading
model available will be configured for use.  Beware that on some
systems, GCC has not been taught what threading models are generally
available for the system.  In this case, <samp><span class="option">--enable-threads</span></samp> is an
alias for <samp><span class="option">--enable-threads=single</span></samp>.

     <br><dt><code>--disable-threads</code><dd>Specify that threading support should be disabled for the system. 
This is an alias for <samp><span class="option">--enable-threads=single</span></samp>.

     <br><dt><code>--enable-threads=</code><var>lib</var><dd>Specify that
<var>lib</var> is the thread support library.  This affects the Objective-C
compiler and runtime library, and exception handling for other languages
like C++ and Java.  The possibilities for <var>lib</var> are:

          <dl>
<dt><code>aix</code><dd>AIX thread support. 
<br><dt><code>dce</code><dd>DCE thread support. 
<br><dt><code>lynx</code><dd>LynxOS thread support. 
<br><dt><code>mipssde</code><dd>MIPS SDE thread support. 
<br><dt><code>no</code><dd>This is an alias for &lsquo;<samp><span class="samp">single</span></samp>&rsquo;. 
<br><dt><code>posix</code><dd>Generic POSIX/Unix98 thread support. 
<br><dt><code>rtems</code><dd>RTEMS thread support. 
<br><dt><code>single</code><dd>Disable thread support, should work for all platforms. 
<br><dt><code>tpf</code><dd>TPF thread support. 
<br><dt><code>vxworks</code><dd>VxWorks thread support. 
<br><dt><code>win32</code><dd>Microsoft Win32 API thread support. 
</dl>

     <br><dt><code>--enable-tls</code><dd>Specify that the target supports TLS (Thread Local Storage).  Usually
configure can correctly determine if TLS is supported.  In cases where
it guesses incorrectly, TLS can be explicitly enabled or disabled with
<samp><span class="option">--enable-tls</span></samp> or <samp><span class="option">--disable-tls</span></samp>.  This can happen if
the assembler supports TLS but the C library does not, or if the
assumptions made by the configure test are incorrect.

     <br><dt><code>--disable-tls</code><dd>Specify that the target does not support TLS. 
This is an alias for <samp><span class="option">--enable-tls=no</span></samp>.

     <br><dt><code>--with-cpu=</code><var>cpu</var><dt><code>--with-cpu-32=</code><var>cpu</var><dt><code>--with-cpu-64=</code><var>cpu</var><dd>Specify which cpu variant the compiler should generate code for by default. 
<var>cpu</var> will be used as the default value of the <samp><span class="option">-mcpu=</span></samp> switch. 
This option is only supported on some targets, including ARC, ARM, i386, M68k,
PowerPC, and SPARC.  It is mandatory for ARC.  The <samp><span class="option">--with-cpu-32</span></samp> and
<samp><span class="option">--with-cpu-64</span></samp> options specify separate default CPUs for
32-bit and 64-bit modes; these options are only supported for i386,
x86-64 and PowerPC.

     <br><dt><code>--with-schedule=</code><var>cpu</var><dt><code>--with-arch=</code><var>cpu</var><dt><code>--with-arch-32=</code><var>cpu</var><dt><code>--with-arch-64=</code><var>cpu</var><dt><code>--with-tune=</code><var>cpu</var><dt><code>--with-tune-32=</code><var>cpu</var><dt><code>--with-tune-64=</code><var>cpu</var><dt><code>--with-abi=</code><var>abi</var><dt><code>--with-fpu=</code><var>type</var><dt><code>--with-float=</code><var>type</var><dd>These configure options provide default values for the <samp><span class="option">-mschedule=</span></samp>,
<samp><span class="option">-march=</span></samp>, <samp><span class="option">-mtune=</span></samp>, <samp><span class="option">-mabi=</span></samp>, and <samp><span class="option">-mfpu=</span></samp>
options and for <samp><span class="option">-mhard-float</span></samp> or <samp><span class="option">-msoft-float</span></samp>.  As with
<samp><span class="option">--with-cpu</span></samp>, which switches will be accepted and acceptable values
of the arguments depend on the target.

     <br><dt><code>--with-mode=</code><var>mode</var><dd>Specify if the compiler should default to <samp><span class="option">-marm</span></samp> or <samp><span class="option">-mthumb</span></samp>. 
This option is only supported on ARM targets.

     <br><dt><code>--with-stack-offset=</code><var>num</var><dd>This option sets the default for the -mstack-offset=<var>num</var> option,
and will thus generally also control the setting of this option for
libraries.  This option is only supported on Epiphany targets.

     <br><dt><code>--with-fpmath=</code><var>isa</var><dd>This options sets <samp><span class="option">-mfpmath=sse</span></samp> by default and specifies the default
ISA for floating-point arithmetics.  You can select either &lsquo;<samp><span class="samp">sse</span></samp>&rsquo; which
enables <samp><span class="option">-msse2</span></samp> or &lsquo;<samp><span class="samp">avx</span></samp>&rsquo; which enables <samp><span class="option">-mavx</span></samp> by default. 
This option is only supported on i386 and x86-64 targets.

     <br><dt><code>--with-fp-32=</code><var>mode</var><dd>On MIPS targets, set the default value for the <samp><span class="option">-mfp</span></samp> option when using
the o32 ABI.  The possibilities for <var>mode</var> are:
          <dl>
<dt><code>32</code><dd>Use the o32 FP32 ABI extension, as with the <samp><span class="option">-mfp32</span></samp> command-line
option. 
<br><dt><code>xx</code><dd>Use the o32 FPXX ABI extension, as with the <samp><span class="option">-mfpxx</span></samp> command-line
option. 
<br><dt><code>64</code><dd>Use the o32 FP64 ABI extension, as with the <samp><span class="option">-mfp64</span></samp> command-line
option. 
</dl>
     In the absence of this configuration option the default is to use the o32
FP32 ABI extension.

     <br><dt><code>--with-odd-spreg-32</code><dd>On MIPS targets, set the <samp><span class="option">-modd-spreg</span></samp> option by default when using
the o32 ABI.

     <br><dt><code>--without-odd-spreg-32</code><dd>On MIPS targets, set the <samp><span class="option">-mno-odd-spreg</span></samp> option by default when using
the o32 ABI.  This is normally used in conjunction with
<samp><span class="option">--with-fp-32=64</span></samp> in order to target the o32 FP64A ABI extension.

     <br><dt><code>--with-nan=</code><var>encoding</var><dd>On MIPS targets, set the default encoding convention to use for the
special not-a-number (NaN) IEEE 754 floating-point data.  The
possibilities for <var>encoding</var> are:
          <dl>
<dt><code>legacy</code><dd>Use the legacy encoding, as with the <samp><span class="option">-mnan=legacy</span></samp> command-line
option. 
<br><dt><code>2008</code><dd>Use the 754-2008 encoding, as with the <samp><span class="option">-mnan=2008</span></samp> command-line
option. 
</dl>
     To use this configuration option you must have an assembler version
installed that supports the <samp><span class="option">-mnan=</span></samp> command-line option too. 
In the absence of this configuration option the default convention is
the legacy encoding, as when neither of the <samp><span class="option">-mnan=2008</span></samp> and
<samp><span class="option">-mnan=legacy</span></samp> command-line options has been used.

     <br><dt><code>--with-divide=</code><var>type</var><dd>Specify how the compiler should generate code for checking for
division by zero.  This option is only supported on the MIPS target. 
The possibilities for <var>type</var> are:
          <dl>
<dt><code>traps</code><dd>Division by zero checks use conditional traps (this is the default on
systems that support conditional traps). 
<br><dt><code>breaks</code><dd>Division by zero checks use the break instruction. 
</dl>

     <!-- If you make -with-llsc the default for additional targets, -->
     <!-- update the -with-llsc description in the MIPS section below. -->
     <br><dt><code>--with-llsc</code><dd>On MIPS targets, make <samp><span class="option">-mllsc</span></samp> the default when no
<samp><span class="option">-mno-llsc</span></samp> option is passed.  This is the default for
Linux-based targets, as the kernel will emulate them if the ISA does
not provide them.

     <br><dt><code>--without-llsc</code><dd>On MIPS targets, make <samp><span class="option">-mno-llsc</span></samp> the default when no
<samp><span class="option">-mllsc</span></samp> option is passed.

     <br><dt><code>--with-synci</code><dd>On MIPS targets, make <samp><span class="option">-msynci</span></samp> the default when no
<samp><span class="option">-mno-synci</span></samp> option is passed.

     <br><dt><code>--without-synci</code><dd>On MIPS targets, make <samp><span class="option">-mno-synci</span></samp> the default when no
<samp><span class="option">-msynci</span></samp> option is passed.  This is the default.

     <br><dt><code>--with-mips-plt</code><dd>On MIPS targets, make use of copy relocations and PLTs. 
These features are extensions to the traditional
SVR4-based MIPS ABIs and require support from GNU binutils
and the runtime C library.

     <br><dt><code>--enable-__cxa_atexit</code><dd>Define if you want to use __cxa_atexit, rather than atexit, to
register C++ destructors for local statics and global objects. 
This is essential for fully standards-compliant handling of
destructors, but requires __cxa_atexit in libc.  This option is currently
only available on systems with GNU libc.  When enabled, this will cause
<samp><span class="option">-fuse-cxa-atexit</span></samp> to be passed by default.

     <br><dt><code>--enable-gnu-indirect-function</code><dd>Define if you want to enable the <code>ifunc</code> attribute.  This option is
currently only available on systems with GNU libc on certain targets.

     <br><dt><code>--enable-target-optspace</code><dd>Specify that target
libraries should be optimized for code space instead of code speed. 
This is the default for the m32r platform.

     <br><dt><code>--with-cpp-install-dir=</code><var>dirname</var><dd>Specify that the user visible <samp><span class="command">cpp</span></samp> program should be installed
in <samp><var>prefix</var><span class="file">/</span><var>dirname</var><span class="file">/cpp</span></samp>, in addition to <var>bindir</var>.

     <br><dt><code>--enable-comdat</code><dd>Enable COMDAT group support.  This is primarily used to override the
automatically detected value.

     <br><dt><code>--enable-initfini-array</code><dd>Force the use of sections <code>.init_array</code> and <code>.fini_array</code>
(instead of <code>.init</code> and <code>.fini</code>) for constructors and
destructors.  Option <samp><span class="option">--disable-initfini-array</span></samp> has the
opposite effect.  If neither option is specified, the configure script
will try to guess whether the <code>.init_array</code> and
<code>.fini_array</code> sections are supported and, if they are, use them.

     <br><dt><code>--enable-link-mutex</code><dd>When building GCC, use a mutex to avoid linking the compilers for
multiple languages at the same time, to avoid thrashing on build
systems with limited free memory.  The default is not to use such a mutex.

     <br><dt><code>--enable-maintainer-mode</code><dd>The build rules that regenerate the Autoconf and Automake output files as
well as the GCC master message catalog <samp><span class="file">gcc.pot</span></samp> are normally
disabled.  This is because it can only be rebuilt if the complete source
tree is present.  If you have changed the sources and want to rebuild the
catalog, configuring with <samp><span class="option">--enable-maintainer-mode</span></samp> will enable
this.  Note that you need a recent version of the <code>gettext</code> tools
to do so.

     <br><dt><code>--disable-bootstrap</code><dd>For a native build, the default configuration is to perform
a 3-stage bootstrap of the compiler when &lsquo;<samp><span class="samp">make</span></samp>&rsquo; is invoked,
testing that GCC can compile itself correctly.  If you want to disable
this process, you can configure with <samp><span class="option">--disable-bootstrap</span></samp>.

     <br><dt><code>--enable-bootstrap</code><dd>In special cases, you may want to perform a 3-stage build
even if the target and host triplets are different. 
This is possible when the host can run code compiled for
the target (e.g. host is i686-linux, target is i486-linux). 
Starting from GCC 4.2, to do this you have to configure explicitly
with <samp><span class="option">--enable-bootstrap</span></samp>.

     <br><dt><code>--enable-generated-files-in-srcdir</code><dd>Neither the .c and .h files that are generated from Bison and flex nor the
info manuals and man pages that are built from the .texi files are present
in the SVN development tree.  When building GCC from that development tree,
or from one of our snapshots, those generated files are placed in your
build directory, which allows for the source to be in a readonly
directory.

     <p>If you configure with <samp><span class="option">--enable-generated-files-in-srcdir</span></samp> then those
generated files will go into the source directory.  This is mainly intended
for generating release or prerelease tarballs of the GCC sources, since it
is not a requirement that the users of source releases to have flex, Bison,
or makeinfo.

     <br><dt><code>--enable-version-specific-runtime-libs</code><dd>Specify
that runtime libraries should be installed in the compiler specific
subdirectory (<samp><var>libdir</var><span class="file">/gcc</span></samp>) rather than the usual places.  In
addition, &lsquo;<samp><span class="samp">libstdc++</span></samp>&rsquo;'s include files will be installed into
<samp><var>libdir</var></samp> unless you overruled it by using
<samp><span class="option">--with-gxx-include-dir=</span><var>dirname</var></samp>.  Using this option is
particularly useful if you intend to use several versions of GCC in
parallel.  This is currently supported by &lsquo;<samp><span class="samp">libgfortran</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">libjava</span></samp>&rsquo;, &lsquo;<samp><span class="samp">libstdc++</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">libobjc</span></samp>&rsquo;.

     <br><dt><code><a name="WithAixSoname"></a>--with-aix-soname=&lsquo;</code><samp><span class="samp">aix</span></samp><code>&rsquo;, &lsquo;</code><samp><span class="samp">svr4</span></samp><code>&rsquo; or &lsquo;</code><samp><span class="samp">both</span></samp><code>&rsquo;</code><dd>Traditional AIX shared library versioning (versioned <code>Shared Object</code>
files as members of unversioned <code>Archive Library</code> files named
&lsquo;<samp><span class="samp">lib.a</span></samp>&rsquo;) causes numerous headaches for package managers. However,
<code>Import Files</code> as members of <code>Archive Library</code> files allow for
<strong>filename-based versioning</strong> of shared libraries as seen on Linux/SVR4,
where this is called the "SONAME". But as they prevent static linking,
<code>Import Files</code> may be used with <code>Runtime Linking</code> only, where the
linker does search for &lsquo;<samp><span class="samp">libNAME.so</span></samp>&rsquo; before &lsquo;<samp><span class="samp">libNAME.a</span></samp>&rsquo; library
filenames with the &lsquo;<samp><span class="samp">-lNAME</span></samp>&rsquo; linker flag.

     <p><a name="AixLdCommand"></a>For detailed information please refer to the AIX
<a href="http://www-01.ibm.com/support/knowledgecenter/search/%22the%20ld%20command%2C%20also%20called%20the%20linkage%20editor%20or%20binder%22">ld Command</a> reference.

     <p>As long as shared library creation is enabled, upon:
          <dl>
<dt><code>--with-aix-soname=aix</code><br><dt><code>--with-aix-soname=both</code><dd> A (traditional AIX) <code>Shared Archive Library</code> file is created:
               <ul>
  <li>using the &lsquo;<samp><span class="samp">libNAME.a</span></samp>&rsquo; filename scheme
  <li>with the <code>Shared Object</code> file as archive member named
  &lsquo;<samp><span class="samp">libNAME.so.V</span></samp>&rsquo; (except for &lsquo;<samp><span class="samp">libgcc_s</span></samp>&rsquo;, where the <code>Shared
  Object</code> file is named &lsquo;<samp><span class="samp">shr.o</span></samp>&rsquo; for backwards compatibility), which
                    <ul>
   <li>is used for runtime loading from inside the &lsquo;<samp><span class="samp">libNAME.a</span></samp>&rsquo; file
   <li>is used for dynamic loading via
   <code>dlopen("libNAME.a(libNAME.so.V)", RTLD_MEMBER)</code>
   <li>is used for shared linking
   <li>is used for static linking, so no separate <code>Static Archive
   Library</code> file is needed
  </ul>
                </ul>
          <br><dt><code>--with-aix-soname=both</code><br><dt><code>--with-aix-soname=svr4</code><dd> A (second) <code>Shared Archive Library</code> file is created:
               <ul>
 <li>using the &lsquo;<samp><span class="samp">libNAME.so.V</span></samp>&rsquo; filename scheme
 <li>with the <code>Shared Object</code> file as archive member named
 &lsquo;<samp><span class="samp">shr.o</span></samp>&rsquo;, which
                    <ul>
   <li>is created with the <code>-G linker flag</code>
   <li>has the <code>F_LOADONLY</code> flag set
   <li>is used for runtime loading from inside the &lsquo;<samp><span class="samp">libNAME.so.V</span></samp>&rsquo; file
   <li>is used for dynamic loading via <code>dlopen("libNAME.so.V(shr.o)",
   RTLD_MEMBER)</code>
  </ul>
                <li>with the <code>Import File</code> as archive member named &lsquo;<samp><span class="samp">shr.imp</span></samp>&rsquo;,
 which
                    <ul>
   <li>refers to &lsquo;<samp><span class="samp">libNAME.so.V(shr.o)</span></samp>&rsquo; as the "SONAME", to be recorded
   in the <code>Loader Section</code> of subsequent binaries
   <li>indicates whether &lsquo;<samp><span class="samp">libNAME.so.V(shr.o)</span></samp>&rsquo; is 32 or 64 bit
   <li>lists all the public symbols exported by &lsquo;<samp><span class="samp">lib.so.V(shr.o)</span></samp>&rsquo;,
   eventually decorated with the <code>&lsquo;</code><samp><span class="samp">weak</span></samp><code>&rsquo; Keyword</code>
   <li>is necessary for shared linking against &lsquo;<samp><span class="samp">lib.so.V(shr.o)</span></samp>&rsquo;
   </ul>
                 </ul>
            A symbolic link using the &lsquo;<samp><span class="samp">libNAME.so</span></samp>&rsquo; filename scheme is created:
               <ul>
  <li>pointing to the &lsquo;<samp><span class="samp">libNAME.so.V</span></samp>&rsquo; <code>Shared Archive Library</code> file
  <li>to permit the <code>ld Command</code> to find &lsquo;<samp><span class="samp">lib.so.V(shr.imp)</span></samp>&rsquo; via
  the &lsquo;<samp><span class="samp">-lNAME</span></samp>&rsquo; argument (requires <code>Runtime Linking</code> to be enabled)
  <li>to permit dynamic loading of &lsquo;<samp><span class="samp">lib.so.V(shr.o)</span></samp>&rsquo; without the need
  to specify the version number via <code>dlopen("libNAME.so(shr.o)",
  RTLD_MEMBER)</code>
  </ul>
          </dl>

     <p>As long as static library creation is enabled, upon:
          <dl>
<dt><code>--with-aix-soname=svr4</code><dd> A <code>Static Archive Library</code> is created:
               <ul>
 <li>using the &lsquo;<samp><span class="samp">libNAME.a</span></samp>&rsquo; filename scheme
 <li>with all the <code>Static Object</code> files as archive members, which
                    <ul>
   <li>are used for static linking
  </ul>
                </ul>
          </dl>

     <p>While the aix-soname=&lsquo;<samp><span class="samp">svr4</span></samp>&rsquo; option does not create <code>Shared Object</code>
files as members of unversioned <code>Archive Library</code> files any more, package
managers still are responsible to
<a href="./specific.html#TransferAixShobj">transfer</a> <code>Shared Object</code> files
found as member of a previously installed unversioned <code>Archive Library</code>
file into the newly installed <code>Archive Library</code> file with the same
filename.

     <p><em>WARNING:</em> Creating <code>Shared Object</code> files with <code>Runtime Linking</code>
enabled may bloat the TOC, eventually leading to <code>TOC overflow</code> errors,
requiring the use of either the <samp><span class="option">-Wl,-bbigtoc</span></samp> linker flag (seen to
break with the <code>GDB</code> debugger) or some of the TOC-related compiler flags,
see &ldquo;RS/6000 and PowerPC Options&rdquo; in the main manual.

     <p><samp><span class="option">--with-aix-soname</span></samp> is currently supported by &lsquo;<samp><span class="samp">libgcc_s</span></samp>&rsquo; only, so
this option is still experimental and not for normal use yet.

     <p>Default is the traditional behaviour <samp><span class="option">--with-aix-soname=&lsquo;</span><samp><span class="samp">aix</span></samp><span class="option">&rsquo;</span></samp>.

     <br><dt><code>--enable-languages=</code><var>lang1</var><code>,</code><var>lang2</var><code>,...</code><dd>Specify that only a particular subset of compilers and
their runtime libraries should be built.  For a list of valid values for
<var>langN</var> you can issue the following command in the
<samp><span class="file">gcc</span></samp> directory of your GCC source tree:<br>
     <pre class="smallexample">          grep language= */config-lang.in
</pre>
     <p>Currently, you can use any of the following:
<code>all</code>, <code>ada</code>, <code>c</code>, <code>c++</code>, <code>fortran</code>,
<code>go</code>, <code>java</code>, <code>objc</code>, <code>obj-c++</code>. 
Building the Ada compiler has special requirements, see below. 
If you do not pass this flag, or specify the option <code>all</code>, then all
default languages available in the <samp><span class="file">gcc</span></samp> sub-tree will be configured. 
Ada, Go and Objective-C++ are not default languages; the rest are.

     <br><dt><code>--enable-stage1-languages=</code><var>lang1</var><code>,</code><var>lang2</var><code>,...</code><dd>Specify that a particular subset of compilers and their runtime
libraries should be built with the system C compiler during stage 1 of
the bootstrap process, rather than only in later stages with the
bootstrapped C compiler.  The list of valid values is the same as for
<samp><span class="option">--enable-languages</span></samp>, and the option <code>all</code> will select all
of the languages enabled by <samp><span class="option">--enable-languages</span></samp>.  This option is
primarily useful for GCC development; for instance, when a development
version of the compiler cannot bootstrap due to compiler bugs, or when
one is debugging front ends other than the C front end.  When this
option is used, one can then build the target libraries for the
specified languages with the stage-1 compiler by using <samp><span class="command">make
stage1-bubble all-target</span></samp>, or run the testsuite on the stage-1 compiler
for the specified languages using <samp><span class="command">make stage1-start check-gcc</span></samp>.

     <br><dt><code>--disable-libada</code><dd>Specify that the run-time libraries and tools used by GNAT should not
be built.  This can be useful for debugging, or for compatibility with
previous Ada build procedures, when it was required to explicitly
do a &lsquo;<samp><span class="samp">make -C gcc gnatlib_and_tools</span></samp>&rsquo;.

     <br><dt><code>--disable-libsanitizer</code><dd>Specify that the run-time libraries for the various sanitizers should
not be built.

     <br><dt><code>--disable-libssp</code><dd>Specify that the run-time libraries for stack smashing protection
should not be built.

     <br><dt><code>--disable-libquadmath</code><dd>Specify that the GCC quad-precision math library should not be built. 
On some systems, the library is required to be linkable when building
the Fortran front end, unless <samp><span class="option">--disable-libquadmath-support</span></samp>
is used.

     <br><dt><code>--disable-libquadmath-support</code><dd>Specify that the Fortran front end and <code>libgfortran</code> do not add
support for <code>libquadmath</code> on systems supporting it.

     <br><dt><code>--disable-libgomp</code><dd>Specify that the GNU Offloading and Multi Processing Runtime Library
should not be built.

     <br><dt><code>--disable-libvtv</code><dd>Specify that the run-time libraries used by vtable verification
should not be built.

     <br><dt><code>--with-dwarf2</code><dd>Specify that the compiler should
use DWARF 2 debugging information as the default.

     <br><dt><code>--enable-targets=all</code><dt><code>--enable-targets=</code><var>target_list</var><dd>Some GCC targets, e.g. powerpc64-linux, build bi-arch compilers. 
These are compilers that are able to generate either 64-bit or 32-bit
code.  Typically, the corresponding 32-bit target, e.g. 
powerpc-linux for powerpc64-linux, only generates 32-bit code.  This
option enables the 32-bit target to be a bi-arch compiler, which is
useful when you want a bi-arch compiler that defaults to 32-bit, and
you are building a bi-arch or multi-arch binutils in a combined tree. 
On mips-linux, this will build a tri-arch compiler (ABI o32/n32/64),
defaulted to o32. 
Currently, this option only affects sparc-linux, powerpc-linux, x86-linux,
mips-linux and s390-linux.

     <br><dt><code>--enable-secureplt</code><dd>This option enables <samp><span class="option">-msecure-plt</span></samp> by default for powerpc-linux. 
See &ldquo;RS/6000 and PowerPC Options&rdquo; in the main manual

     <br><dt><code>--enable-cld</code><dd>This option enables <samp><span class="option">-mcld</span></samp> by default for 32-bit x86 targets. 
See &ldquo;i386 and x86-64 Options&rdquo; in the main manual

     <br><dt><code>--enable-win32-registry</code><dt><code>--enable-win32-registry=</code><var>key</var><dt><code>--disable-win32-registry</code><dd>The <samp><span class="option">--enable-win32-registry</span></samp> option enables Microsoft Windows-hosted GCC
to look up installations paths in the registry using the following key:

     <pre class="smallexample">          <code>HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\</code><var>key</var>
</pre>
     <p><var>key</var> defaults to GCC version number, and can be overridden by the
<samp><span class="option">--enable-win32-registry=</span><var>key</var></samp> option.  Vendors and distributors
who use custom installers are encouraged to provide a different key,
perhaps one comprised of vendor name and GCC version number, to
avoid conflict with existing installations.  This feature is enabled
by default, and can be disabled by <samp><span class="option">--disable-win32-registry</span></samp>
option.  This option has no effect on the other hosts.

     <br><dt><code>--nfp</code><dd>Specify that the machine does not have a floating point unit.  This
option only applies to &lsquo;<samp><span class="samp">m68k-sun-sunos</span><var>n</var></samp>&rsquo;.  On any other
system, <samp><span class="option">--nfp</span></samp> has no effect.

     <br><dt><code>--enable-werror</code><dt><code>--disable-werror</code><dt><code>--enable-werror=yes</code><dt><code>--enable-werror=no</code><dd>When you specify this option, it controls whether certain files in the
compiler are built with <samp><span class="option">-Werror</span></samp> in bootstrap stage2 and later. 
If you don't specify it, <samp><span class="option">-Werror</span></samp> is turned on for the main
development trunk.  However it defaults to off for release branches and
final releases.  The specific files which get <samp><span class="option">-Werror</span></samp> are
controlled by the Makefiles.

     <br><dt><code>--enable-checking</code><dt><code>--enable-checking=</code><var>list</var><dd>When you specify this option, the compiler is built to perform internal
consistency checks of the requested complexity.  This does not change the
generated code, but adds error checking within the compiler.  This will
slow down the compiler and may only work properly if you are building
the compiler with GCC.  This is &lsquo;<samp><span class="samp">yes</span></samp>&rsquo; by default when building
from SVN or snapshots, but &lsquo;<samp><span class="samp">release</span></samp>&rsquo; for releases.  The default
for building the stage1 compiler is &lsquo;<samp><span class="samp">yes</span></samp>&rsquo;.  More control
over the checks may be had by specifying <var>list</var>.  The categories of
checks available are &lsquo;<samp><span class="samp">yes</span></samp>&rsquo; (most common checks
&lsquo;<samp><span class="samp">assert,misc,tree,gc,rtlflag,runtime</span></samp>&rsquo;), &lsquo;<samp><span class="samp">no</span></samp>&rsquo; (no checks at
all), &lsquo;<samp><span class="samp">all</span></samp>&rsquo; (all but &lsquo;<samp><span class="samp">valgrind</span></samp>&rsquo;), &lsquo;<samp><span class="samp">release</span></samp>&rsquo; (cheapest
checks &lsquo;<samp><span class="samp">assert,runtime</span></samp>&rsquo;) or &lsquo;<samp><span class="samp">none</span></samp>&rsquo; (same as &lsquo;<samp><span class="samp">no</span></samp>&rsquo;). 
Individual checks can be enabled with these flags &lsquo;<samp><span class="samp">assert</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">df</span></samp>&rsquo;, &lsquo;<samp><span class="samp">fold</span></samp>&rsquo;, &lsquo;<samp><span class="samp">gc</span></samp>&rsquo;, &lsquo;<samp><span class="samp">gcac</span></samp>&rsquo; &lsquo;<samp><span class="samp">misc</span></samp>&rsquo;, &lsquo;<samp><span class="samp">rtl</span></samp>&rsquo;,
&lsquo;<samp><span class="samp">rtlflag</span></samp>&rsquo;, &lsquo;<samp><span class="samp">runtime</span></samp>&rsquo;, &lsquo;<samp><span class="samp">tree</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">valgrind</span></samp>&rsquo;.

     <p>The &lsquo;<samp><span class="samp">valgrind</span></samp>&rsquo; check requires the external <samp><span class="command">valgrind</span></samp>
simulator, available from <a href="http://valgrind.org/">http://valgrind.org/</a>.  The
&lsquo;<samp><span class="samp">df</span></samp>&rsquo;, &lsquo;<samp><span class="samp">rtl</span></samp>&rsquo;, &lsquo;<samp><span class="samp">gcac</span></samp>&rsquo; and &lsquo;<samp><span class="samp">valgrind</span></samp>&rsquo; checks are very expensive. 
To disable all checking, &lsquo;<samp><span class="samp">--disable-checking</span></samp>&rsquo; or
&lsquo;<samp><span class="samp">--enable-checking=none</span></samp>&rsquo; must be explicitly requested.  Disabling
assertions will make the compiler and runtime slightly faster but
increase the risk of undetected internal errors causing wrong code to be
generated.

     <br><dt><code>--disable-stage1-checking</code><dt><code>--enable-stage1-checking</code><dt><code>--enable-stage1-checking=</code><var>list</var><dd>If no <samp><span class="option">--enable-checking</span></samp> option is specified the stage1
compiler will be built with &lsquo;<samp><span class="samp">yes</span></samp>&rsquo; checking enabled, otherwise
the stage1 checking flags are the same as specified by
<samp><span class="option">--enable-checking</span></samp>.  To build the stage1 compiler with
different checking options use <samp><span class="option">--enable-stage1-checking</span></samp>. 
The list of checking options is the same as for <samp><span class="option">--enable-checking</span></samp>. 
If your system is too slow or too small to bootstrap a released compiler
with checking for stage1 enabled, you can use &lsquo;<samp><span class="samp">--disable-stage1-checking</span></samp>&rsquo;
to disable checking for the stage1 compiler.

     <br><dt><code>--enable-coverage</code><dt><code>--enable-coverage=</code><var>level</var><dd>With this option, the compiler is built to collect self coverage
information, every time it is run.  This is for internal development
purposes, and only works when the compiler is being built with gcc.  The
<var>level</var> argument controls whether the compiler is built optimized or
not, values are &lsquo;<samp><span class="samp">opt</span></samp>&rsquo; and &lsquo;<samp><span class="samp">noopt</span></samp>&rsquo;.  For coverage analysis you
want to disable optimization, for performance analysis you want to
enable optimization.  When coverage is enabled, the default level is
without optimization.

     <br><dt><code>--enable-gather-detailed-mem-stats</code><dd>When this option is specified more detailed information on memory
allocation is gathered.  This information is printed when using
<samp><span class="option">-fmem-report</span></samp>.

     <br><dt><code>--enable-nls</code><dt><code>--disable-nls</code><dd>The <samp><span class="option">--enable-nls</span></samp> option enables Native Language Support (NLS),
which lets GCC output diagnostics in languages other than American
English.  Native Language Support is enabled by default if not doing a
canadian cross build.  The <samp><span class="option">--disable-nls</span></samp> option disables NLS.

     <br><dt><code>--with-included-gettext</code><dd>If NLS is enabled, the <samp><span class="option">--with-included-gettext</span></samp> option causes the build
procedure to prefer its copy of GNU <samp><span class="command">gettext</span></samp>.

     <br><dt><code>--with-catgets</code><dd>If NLS is enabled, and if the host lacks <code>gettext</code> but has the
inferior <code>catgets</code> interface, the GCC build procedure normally
ignores <code>catgets</code> and instead uses GCC's copy of the GNU
<code>gettext</code> library.  The <samp><span class="option">--with-catgets</span></samp> option causes the
build procedure to use the host's <code>catgets</code> in this situation.

     <br><dt><code>--with-libiconv-prefix=</code><var>dir</var><dd>Search for libiconv header files in <samp><var>dir</var><span class="file">/include</span></samp> and
libiconv library files in <samp><var>dir</var><span class="file">/lib</span></samp>.

     <br><dt><code>--enable-obsolete</code><dd>Enable configuration for an obsoleted system.  If you attempt to
configure GCC for a system (build, host, or target) which has been
obsoleted, and you do not specify this flag, configure will halt with an
error message.

     <p>All support for systems which have been obsoleted in one release of GCC
is removed entirely in the next major release, unless someone steps
forward to maintain the port.

     <br><dt><code>--enable-decimal-float</code><dt><code>--enable-decimal-float=yes</code><dt><code>--enable-decimal-float=no</code><dt><code>--enable-decimal-float=bid</code><dt><code>--enable-decimal-float=dpd</code><dt><code>--disable-decimal-float</code><dd>Enable (or disable) support for the C decimal floating point extension
that is in the IEEE 754-2008 standard.  This is enabled by default only
on PowerPC, i386, and x86_64 GNU/Linux systems.  Other systems may also
support it, but require the user to specifically enable it.  You can
optionally control which decimal floating point format is used (either
&lsquo;<samp><span class="samp">bid</span></samp>&rsquo; or &lsquo;<samp><span class="samp">dpd</span></samp>&rsquo;).  The &lsquo;<samp><span class="samp">bid</span></samp>&rsquo; (binary integer decimal)
format is default on i386 and x86_64 systems, and the &lsquo;<samp><span class="samp">dpd</span></samp>&rsquo;
(densely packed decimal) format is default on PowerPC systems.

     <br><dt><code>--enable-fixed-point</code><dt><code>--disable-fixed-point</code><dd>Enable (or disable) support for C fixed-point arithmetic. 
This option is enabled by default for some targets (such as MIPS) which
have hardware-support for fixed-point operations.  On other targets, you
may enable this option manually.

     <br><dt><code>--with-long-double-128</code><dd>Specify if <code>long double</code> type should be 128-bit by default on selected
GNU/Linux architectures.  If using <code>--without-long-double-128</code>,
<code>long double</code> will be by default 64-bit, the same as <code>double</code> type. 
When neither of these configure options are used, the default will be
128-bit <code>long double</code> when built against GNU C Library 2.4 and later,
64-bit <code>long double</code> otherwise.

     <br><dt><code>--with-gmp=</code><var>pathname</var><dt><code>--with-gmp-include=</code><var>pathname</var><dt><code>--with-gmp-lib=</code><var>pathname</var><dt><code>--with-mpfr=</code><var>pathname</var><dt><code>--with-mpfr-include=</code><var>pathname</var><dt><code>--with-mpfr-lib=</code><var>pathname</var><dt><code>--with-mpc=</code><var>pathname</var><dt><code>--with-mpc-include=</code><var>pathname</var><dt><code>--with-mpc-lib=</code><var>pathname</var><dd>If you want to build GCC but do not have the GMP library, the MPFR
library and/or the MPC library installed in a standard location and
do not have their sources present in the GCC source tree then you
can explicitly specify the directory where they are installed
(&lsquo;<samp><span class="samp">--with-gmp=</span><var>gmpinstalldir</var></samp>&rsquo;,
&lsquo;<samp><span class="samp">--with-mpfr=</span><var>mpfrinstalldir</var></samp>&rsquo;,
&lsquo;<samp><span class="samp">--with-mpc=</span><var>mpcinstalldir</var></samp>&rsquo;).  The
<samp><span class="option">--with-gmp=</span><var>gmpinstalldir</var></samp> option is shorthand for
<samp><span class="option">--with-gmp-lib=</span><var>gmpinstalldir</var><span class="option">/lib</span></samp> and
<samp><span class="option">--with-gmp-include=</span><var>gmpinstalldir</var><span class="option">/include</span></samp>.  Likewise the
<samp><span class="option">--with-mpfr=</span><var>mpfrinstalldir</var></samp> option is shorthand for
<samp><span class="option">--with-mpfr-lib=</span><var>mpfrinstalldir</var><span class="option">/lib</span></samp> and
<samp><span class="option">--with-mpfr-include=</span><var>mpfrinstalldir</var><span class="option">/include</span></samp>, also the
<samp><span class="option">--with-mpc=</span><var>mpcinstalldir</var></samp> option is shorthand for
<samp><span class="option">--with-mpc-lib=</span><var>mpcinstalldir</var><span class="option">/lib</span></samp> and
<samp><span class="option">--with-mpc-include=</span><var>mpcinstalldir</var><span class="option">/include</span></samp>.  If these
shorthand assumptions are not correct, you can use the explicit
include and lib options directly.  You might also need to ensure the
shared libraries can be found by the dynamic linker when building and
using GCC, for example by setting the runtime shared library path
variable (<samp><span class="env">LD_LIBRARY_PATH</span></samp> on GNU/Linux and Solaris systems).

     <p>These flags are applicable to the host platform only.  When building
a cross compiler, they will not be used to configure target libraries.

     <br><dt><code>--with-isl=</code><var>pathname</var><dt><code>--with-isl-include=</code><var>pathname</var><dt><code>--with-isl-lib=</code><var>pathname</var><dd>If you do not have the ISL library installed in a standard location and you
want to build GCC, you can explicitly specify the directory where it is
installed (&lsquo;<samp><span class="samp">--with-isl=</span><var>islinstalldir</var></samp>&rsquo;). The
<samp><span class="option">--with-isl=</span><var>islinstalldir</var></samp> option is shorthand for
<samp><span class="option">--with-isl-lib=</span><var>islinstalldir</var><span class="option">/lib</span></samp> and
<samp><span class="option">--with-isl-include=</span><var>islinstalldir</var><span class="option">/include</span></samp>. If this
shorthand assumption is not correct, you can use the explicit
include and lib options directly.

     <p>These flags are applicable to the host platform only.  When building
a cross compiler, they will not be used to configure target libraries.

     <br><dt><code>--with-host-libstdcxx=</code><var>linker-args</var><dd>If you are linking with a static copy of PPL, you can use this option
to specify how the linker should find the standard C++ library used
internally by PPL.  Typical values of <var>linker-args</var> might be
&lsquo;<samp><span class="samp">-lstdc++</span></samp>&rsquo; or &lsquo;<samp><span class="samp">-Wl,-Bstatic,-lstdc++,-Bdynamic -lm</span></samp>&rsquo;.  If you are
linking with a shared copy of PPL, you probably do not need this
option; shared library dependencies will cause the linker to search
for the standard C++ library automatically.

     <br><dt><code>--with-stage1-ldflags=</code><var>flags</var><dd>This option may be used to set linker flags to be used when linking
stage 1 of GCC.  These are also used when linking GCC if configured with
<samp><span class="option">--disable-bootstrap</span></samp>.  By default no special flags are used.

     <br><dt><code>--with-stage1-libs=</code><var>libs</var><dd>This option may be used to set libraries to be used when linking stage 1
of GCC.  These are also used when linking GCC if configured with
<samp><span class="option">--disable-bootstrap</span></samp>.  The default is the argument to
<samp><span class="option">--with-host-libstdcxx</span></samp>, if specified.

     <br><dt><code>--with-boot-ldflags=</code><var>flags</var><dd>This option may be used to set linker flags to be used when linking
stage 2 and later when bootstrapping GCC.  If neither &ndash;with-boot-libs
nor &ndash;with-host-libstdcxx is set to a value, then the default is
&lsquo;<samp><span class="samp">-static-libstdc++ -static-libgcc</span></samp>&rsquo;.

     <br><dt><code>--with-boot-libs=</code><var>libs</var><dd>This option may be used to set libraries to be used when linking stage 2
and later when bootstrapping GCC.  The default is the argument to
<samp><span class="option">--with-host-libstdcxx</span></samp>, if specified.

     <br><dt><code>--with-debug-prefix-map=</code><var>map</var><dd>Convert source directory names using <samp><span class="option">-fdebug-prefix-map</span></samp> when
building runtime libraries.  &lsquo;<samp><var>map</var></samp>&rsquo; is a space-separated
list of maps of the form &lsquo;<samp><var>old</var><span class="samp">=</span><var>new</var></samp>&rsquo;.

     <br><dt><code>--enable-linker-build-id</code><dd>Tells GCC to pass <samp><span class="option">--build-id</span></samp> option to the linker for all final
links (links performed without the <samp><span class="option">-r</span></samp> or <samp><span class="option">--relocatable</span></samp>
option), if the linker supports it.  If you specify
<samp><span class="option">--enable-linker-build-id</span></samp>, but your linker does not
support <samp><span class="option">--build-id</span></samp> option, a warning is issued and the
<samp><span class="option">--enable-linker-build-id</span></samp> option is ignored.  The default is off.

     <br><dt><code>--with-linker-hash-style=</code><var>choice</var><dd>Tells GCC to pass <samp><span class="option">--hash-style=</span><var>choice</var></samp> option to the
linker for all final links. <var>choice</var> can be one of
&lsquo;<samp><span class="samp">sysv</span></samp>&rsquo;, &lsquo;<samp><span class="samp">gnu</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">both</span></samp>&rsquo; where &lsquo;<samp><span class="samp">sysv</span></samp>&rsquo; is the default.

     <br><dt><code>--enable-gnu-unique-object</code><dt><code>--disable-gnu-unique-object</code><dd>Tells GCC to use the gnu_unique_object relocation for C++ template
static data members and inline function local statics.  Enabled by
default for a toolchain with an assembler that accepts it and
GLIBC 2.11 or above, otherwise disabled.

     <br><dt><code>--with-diagnostics-color=</code><var>choice</var><dd>Tells GCC to use <var>choice</var> as the default for <samp><span class="option">-fdiagnostics-color=</span></samp>
option (if not used explicitly on the command line).  <var>choice</var>
can be one of &lsquo;<samp><span class="samp">never</span></samp>&rsquo;, &lsquo;<samp><span class="samp">auto</span></samp>&rsquo;, &lsquo;<samp><span class="samp">always</span></samp>&rsquo;, and &lsquo;<samp><span class="samp">auto-if-env</span></samp>&rsquo;
where &lsquo;<samp><span class="samp">auto</span></samp>&rsquo; is the default.  &lsquo;<samp><span class="samp">auto-if-env</span></samp>&rsquo; means that
<samp><span class="option">-fdiagnostics-color=auto</span></samp> will be the default if <code>GCC_COLORS</code>
is present and non-empty in the environment, and
<samp><span class="option">-fdiagnostics-color=never</span></samp> otherwise.

     <br><dt><code>--enable-lto</code><dt><code>--disable-lto</code><dd>Enable support for link-time optimization (LTO).  This is enabled by
default, and may be disabled using <samp><span class="option">--disable-lto</span></samp>.

     <br><dt><code>--enable-linker-plugin-configure-flags=FLAGS</code><dt><code>--enable-linker-plugin-flags=FLAGS</code><dd>By default, linker plugins (such as the LTO plugin) are built for the
host system architecture.  For the case that the linker has a
different (but run-time compatible) architecture, these flags can be
specified to build plugins that are compatible to the linker.  For
example, if you are building GCC for a 64-bit x86_64
(&lsquo;<samp><span class="samp">x86_64-unknown-linux-gnu</span></samp>&rsquo;) host system, but have a 32-bit x86
GNU/Linux (&lsquo;<samp><span class="samp">i686-pc-linux-gnu</span></samp>&rsquo;) linker executable (which is
executable on the former system), you can configure GCC as follows for
getting compatible linker plugins:

     <pre class="smallexample">          % <var>srcdir</var>/configure \
              --host=x86_64-unknown-linux-gnu \
              --enable-linker-plugin-configure-flags=--host=i686-pc-linux-gnu \
              --enable-linker-plugin-flags='CC=gcc\ -m32\ -Wl,-rpath,[...]/i686-pc-linux-gnu/lib'
</pre>
     <br><dt><code>--with-plugin-ld=</code><var>pathname</var><dd>Enable an alternate linker to be used at link-time optimization (LTO)
link time when <samp><span class="option">-fuse-linker-plugin</span></samp> is enabled. 
This linker should have plugin support such as gold starting with
version 2.20 or GNU ld starting with version 2.21. 
See <samp><span class="option">-fuse-linker-plugin</span></samp> for details.

     <br><dt><code>--enable-canonical-system-headers</code><dt><code>--disable-canonical-system-headers</code><dd>Enable system header path canonicalization for <samp><span class="file">libcpp</span></samp>.  This can
produce shorter header file paths in diagnostics and dependency output
files, but these changed header paths may conflict with some compilation
environments.  Enabled by default, and may be disabled using
<samp><span class="option">--disable-canonical-system-headers</span></samp>.

     <br><dt><code>--with-glibc-version=</code><var>major</var><code>.</code><var>minor</var><dd>Tell GCC that when the GNU C Library (glibc) is used on the target it
will be version <var>major</var>.<var>minor</var> or later.  Normally this can
be detected from the C library's header files, but this option may be
needed when bootstrapping a cross toolchain without the header files
available for building the initial bootstrap compiler.

     <p>If GCC is configured with some multilibs that use glibc and some that
do not, this option applies only to the multilibs that use glibc. 
However, such configurations may not work well as not all the relevant
configuration in GCC is on a per-multilib basis.

     <br><dt><code>--enable-as-accelerator-for=</code><var>target</var><dd>Build as offload target compiler. Specify offload host triple by <var>target</var>.

     <br><dt><code>--enable-offload-targets=</code><var>target1</var><code>[=</code><var>path1</var><code>],...,</code><var>targetN</var><code>[=</code><var>pathN</var><code>]</code><dd>Enable offloading to targets <var>target1</var>, <small class="dots">...</small>, <var>targetN</var>. 
Offload compilers are expected to be already installed.  Default search
path for them is <samp><var>exec-prefix</var></samp>, but it can be changed by
specifying paths <var>path1</var>, <small class="dots">...</small>, <var>pathN</var>.

     <pre class="smallexample">          % <var>srcdir</var>/configure \
              --enable-offload-target=i686-unknown-linux-gnu=/path/to/i686/compiler,x86_64-pc-linux-gnu
</pre>
     </dl>

<h4 class="subheading"><a name="TOC3"></a>Cross-Compiler-Specific Options</h4>

<p>The following options only apply to building cross compilers.

     <dl>
<dt><code>--with-sysroot</code><dt><code>--with-sysroot=</code><var>dir</var><dd>Tells GCC to consider <var>dir</var> as the root of a tree that contains
(a subset of) the root filesystem of the target operating system. 
Target system headers, libraries and run-time object files will be
searched for in there.  More specifically, this acts as if
<samp><span class="option">--sysroot=</span><var>dir</var></samp> was added to the default options of the built
compiler.  The specified directory is not copied into the
install tree, unlike the options <samp><span class="option">--with-headers</span></samp> and
<samp><span class="option">--with-libs</span></samp> that this option obsoletes.  The default value,
in case <samp><span class="option">--with-sysroot</span></samp> is not given an argument, is
<samp><span class="option">${gcc_tooldir}/sys-root</span></samp>.  If the specified directory is a
subdirectory of <samp><span class="option">${exec_prefix}</span></samp>, then it will be found relative to
the GCC binaries if the installation tree is moved.

     <p>This option affects the system root for the compiler used to build
target libraries (which runs on the build system) and the compiler newly
installed with <code>make install</code>; it does not affect the compiler which is
used to build GCC itself.

     <p>If you specify the <samp><span class="option">--with-native-system-header-dir=</span><var>dirname</var></samp>
option then the compiler will search that directory within <var>dirname</var> for
native system headers rather than the default <samp><span class="file">/usr/include</span></samp>.

     <br><dt><code>--with-build-sysroot</code><dt><code>--with-build-sysroot=</code><var>dir</var><dd>Tells GCC to consider <var>dir</var> as the system root (see
<samp><span class="option">--with-sysroot</span></samp>) while building target libraries, instead of
the directory specified with <samp><span class="option">--with-sysroot</span></samp>.  This option is
only useful when you are already using <samp><span class="option">--with-sysroot</span></samp>.  You
can use <samp><span class="option">--with-build-sysroot</span></samp> when you are configuring with
<samp><span class="option">--prefix</span></samp> set to a directory that is different from the one in
which you are installing GCC and your target libraries.

     <p>This option affects the system root for the compiler used to build
target libraries (which runs on the build system); it does not affect
the compiler which is used to build GCC itself.

     <p>If you specify the <samp><span class="option">--with-native-system-header-dir=</span><var>dirname</var></samp>
option then the compiler will search that directory within <var>dirname</var> for
native system headers rather than the default <samp><span class="file">/usr/include</span></samp>.

     <br><dt><code>--with-headers</code><dt><code>--with-headers=</code><var>dir</var><dd>Deprecated in favor of <samp><span class="option">--with-sysroot</span></samp>. 
Specifies that target headers are available when building a cross compiler. 
The <var>dir</var> argument specifies a directory which has the target include
files.  These include files will be copied into the <samp><span class="file">gcc</span></samp> install
directory.  <em>This option with the </em><var>dir</var><em> argument is required</em> when
building a cross compiler, if <samp><var>prefix</var><span class="file">/</span><var>target</var><span class="file">/sys-include</span></samp>
doesn't pre-exist.  If <samp><var>prefix</var><span class="file">/</span><var>target</var><span class="file">/sys-include</span></samp> does
pre-exist, the <var>dir</var> argument may be omitted.  <samp><span class="command">fixincludes</span></samp>
will be run on these files to make them compatible with GCC.

     <br><dt><code>--without-headers</code><dd>Tells GCC not use any target headers from a libc when building a cross
compiler.  When crossing to GNU/Linux, you need the headers so GCC
can build the exception handling for libgcc.

     <br><dt><code>--with-libs</code><dt><code>--with-libs="</code><var>dir1</var> <var>dir2</var><code> ... </code><var>dirN</var><code>"</code><dd>Deprecated in favor of <samp><span class="option">--with-sysroot</span></samp>. 
Specifies a list of directories which contain the target runtime
libraries.  These libraries will be copied into the <samp><span class="file">gcc</span></samp> install
directory.  If the directory list is omitted, this option has no
effect.

     <br><dt><code>--with-newlib</code><dd>Specifies that &lsquo;<samp><span class="samp">newlib</span></samp>&rsquo; is
being used as the target C library.  This causes <code>__eprintf</code> to be
omitted from <samp><span class="file">libgcc.a</span></samp> on the assumption that it will be provided by
&lsquo;<samp><span class="samp">newlib</span></samp>&rsquo;.

     <br><dt><code>--with-avrlibc</code><dd>Specifies that &lsquo;<samp><span class="samp">AVR-Libc</span></samp>&rsquo; is
being used as the target C library.  This causes float support
functions like <code>__addsf3</code> to be omitted from <samp><span class="file">libgcc.a</span></samp> on
the assumption that it will be provided by <samp><span class="file">libm.a</span></samp>.  For more
technical details, cf. <a href="http://gcc.gnu.org/PR54461">PR54461</a>. 
This option is only supported for the AVR target.  It is not supported for
RTEMS configurations, which currently use newlib.  The option is
supported since version 4.7.2 and is the default in 4.8.0 and newer.

     <br><dt><code>--with-nds32-lib=</code><var>library</var><dd>Specifies that <var>library</var> setting is used for building <samp><span class="file">libgcc.a</span></samp>. 
Currently, the valid <var>library</var> is &lsquo;<samp><span class="samp">newlib</span></samp>&rsquo; or &lsquo;<samp><span class="samp">mculib</span></samp>&rsquo;. 
This option is only supported for the NDS32 target.

     <br><dt><code>--with-build-time-tools=</code><var>dir</var><dd>Specifies where to find the set of target tools (assembler, linker, etc.) 
that will be used while building GCC itself.  This option can be useful
if the directory layouts are different between the system you are building
GCC on, and the system where you will deploy it.

     <p>For example, on an &lsquo;<samp><span class="samp">ia64-hp-hpux</span></samp>&rsquo; system, you may have the GNU
assembler and linker in <samp><span class="file">/usr/bin</span></samp>, and the native tools in a
different path, and build a toolchain that expects to find the
native tools in <samp><span class="file">/usr/bin</span></samp>.

     <p>When you use this option, you should ensure that <var>dir</var> includes
<samp><span class="command">ar</span></samp>, <samp><span class="command">as</span></samp>, <samp><span class="command">ld</span></samp>, <samp><span class="command">nm</span></samp>,
<samp><span class="command">ranlib</span></samp> and <samp><span class="command">strip</span></samp> if necessary, and possibly
<samp><span class="command">objdump</span></samp>.  Otherwise, GCC may use an inconsistent set of
tools. 
</dl>

<h4 class="subheading"><a name="TOC4"></a>Java-Specific Options</h4>

<p>The following option applies to the build of the Java front end.

     <dl>
<dt><code>--disable-libgcj</code><dd>Specify that the run-time libraries
used by GCJ should not be built.  This is useful in case you intend
to use GCJ with some other run-time, or you're going to install it
separately, or it just happens not to build on your particular
machine.  In general, if the Java front end is enabled, the GCJ
libraries will be enabled too, unless they're known to not work on
the target platform.  If GCJ is enabled but &lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo; isn't built, you
may need to port it; in this case, before modifying the top-level
<samp><span class="file">configure.in</span></samp> so that &lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo; is enabled by default on this platform,
you may use <samp><span class="option">--enable-libgcj</span></samp> to override the default.

   </dl>

   <p>The following options apply to building &lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo;.

<h5 class="subsubheading"><a name="TOC5"></a>General Options</h5>

     <dl>
<dt><code>--enable-java-maintainer-mode</code><dd>By default the &lsquo;<samp><span class="samp">libjava</span></samp>&rsquo; build will not attempt to compile the
<samp><span class="file">.java</span></samp> source files to <samp><span class="file">.class</span></samp>.  Instead, it will use the
<samp><span class="file">.class</span></samp> files from the source tree.  If you use this option you
must have executables named <samp><span class="command">ecj1</span></samp> and <samp><span class="command">gjavah</span></samp> in your path
for use by the build.  You must use this option if you intend to
modify any <samp><span class="file">.java</span></samp> files in <samp><span class="file">libjava</span></samp>.

     <br><dt><code>--with-java-home=</code><var>dirname</var><dd>This &lsquo;<samp><span class="samp">libjava</span></samp>&rsquo; option overrides the default value of the
&lsquo;<samp><span class="samp">java.home</span></samp>&rsquo; system property.  It is also used to set
&lsquo;<samp><span class="samp">sun.boot.class.path</span></samp>&rsquo; to <samp><var>dirname</var><span class="file">/lib/rt.jar</span></samp>.  By
default &lsquo;<samp><span class="samp">java.home</span></samp>&rsquo; is set to <samp><var>prefix</var></samp> and
&lsquo;<samp><span class="samp">sun.boot.class.path</span></samp>&rsquo; to
<samp><var>datadir</var><span class="file">/java/libgcj-</span><var>version</var><span class="file">.jar</span></samp>.

     <br><dt><code>--with-ecj-jar=</code><var>filename</var><dd>This option can be used to specify the location of an external jar
file containing the Eclipse Java compiler.  A specially modified
version of this compiler is used by <samp><span class="command">gcj</span></samp> to parse
<samp><span class="file">.java</span></samp> source files.  If this option is given, the
&lsquo;<samp><span class="samp">libjava</span></samp>&rsquo; build will create and install an <samp><span class="file">ecj1</span></samp> executable
which uses this jar file at runtime.

     <p>If this option is not given, but an <samp><span class="file">ecj.jar</span></samp> file is found in
the topmost source tree at configure time, then the &lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo;
build will create and install <samp><span class="file">ecj1</span></samp>, and will also install the
discovered <samp><span class="file">ecj.jar</span></samp> into a suitable place in the install tree.

     <p>If <samp><span class="file">ecj1</span></samp> is not installed, then the user will have to supply one
on his path in order for <samp><span class="command">gcj</span></samp> to properly parse <samp><span class="file">.java</span></samp>
source files.  A suitable jar is available from
<a href="ftp://sourceware.org/pub/java/">ftp://sourceware.org/pub/java/</a>.

     <br><dt><code>--disable-getenv-properties</code><dd>Don't set system properties from <samp><span class="env">GCJ_PROPERTIES</span></samp>.

     <br><dt><code>--enable-hash-synchronization</code><dd>Use a global hash table for monitor locks.  Ordinarily,
&lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo;'s &lsquo;<samp><span class="samp">configure</span></samp>&rsquo; script automatically makes
the correct choice for this option for your platform.  Only use
this if you know you need the library to be configured differently.

     <br><dt><code>--enable-interpreter</code><dd>Enable the Java interpreter.  The interpreter is automatically
enabled by default on all platforms that support it.  This option
is really only useful if you want to disable the interpreter
(using <samp><span class="option">--disable-interpreter</span></samp>).

     <br><dt><code>--disable-java-net</code><dd>Disable java.net.  This disables the native part of java.net only,
using non-functional stubs for native method implementations.

     <br><dt><code>--disable-jvmpi</code><dd>Disable JVMPI support.

     <br><dt><code>--disable-libgcj-bc</code><dd>Disable BC ABI compilation of certain parts of libgcj.  By default,
some portions of libgcj are compiled with <samp><span class="option">-findirect-dispatch</span></samp>
and <samp><span class="option">-fno-indirect-classes</span></samp>, allowing them to be overridden at
run-time.

     <p>If <samp><span class="option">--disable-libgcj-bc</span></samp> is specified, libgcj is built without
these options.  This allows the compile-time linker to resolve
dependencies when statically linking to libgcj.  However it makes it
impossible to override the affected portions of libgcj at run-time.

     <br><dt><code>--enable-reduced-reflection</code><dd>Build most of libgcj with <samp><span class="option">-freduced-reflection</span></samp>.  This reduces
the size of libgcj at the expense of not being able to do accurate
reflection on the classes it contains.  This option is safe if you
know that code using libgcj will never use reflection on the standard
runtime classes in libgcj (including using serialization, RMI or CORBA).

     <br><dt><code>--with-ecos</code><dd>Enable runtime eCos target support.

     <br><dt><code>--without-libffi</code><dd>Don't use &lsquo;<samp><span class="samp">libffi</span></samp>&rsquo;.  This will disable the interpreter and JNI
support as well, as these require &lsquo;<samp><span class="samp">libffi</span></samp>&rsquo; to work.

     <br><dt><code>--enable-libgcj-debug</code><dd>Enable runtime debugging code.

     <br><dt><code>--enable-libgcj-multifile</code><dd>If specified, causes all <samp><span class="file">.java</span></samp> source files to be
compiled into <samp><span class="file">.class</span></samp> files in one invocation of
&lsquo;<samp><span class="samp">gcj</span></samp>&rsquo;.  This can speed up build time, but is more
resource-intensive.  If this option is unspecified or
disabled, &lsquo;<samp><span class="samp">gcj</span></samp>&rsquo; is invoked once for each <samp><span class="file">.java</span></samp>
file to compile into a <samp><span class="file">.class</span></samp> file.

     <br><dt><code>--with-libiconv-prefix=DIR</code><dd>Search for libiconv in <samp><span class="file">DIR/include</span></samp> and <samp><span class="file">DIR/lib</span></samp>.

     <br><dt><code>--enable-sjlj-exceptions</code><dd>Force use of the <code>setjmp</code>/<code>longjmp</code>-based scheme for exceptions. 
&lsquo;<samp><span class="samp">configure</span></samp>&rsquo; ordinarily picks the correct value based on the platform. 
Only use this option if you are sure you need a different setting.

     <br><dt><code>--with-system-zlib</code><dd>Use installed &lsquo;<samp><span class="samp">zlib</span></samp>&rsquo; rather than that included with GCC.

     <br><dt><code>--with-win32-nlsapi=ansi, unicows or unicode</code><dd>Indicates how MinGW &lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo; translates between UNICODE
characters and the Win32 API.

     <br><dt><code>--enable-java-home</code><dd>If enabled, this creates a JPackage compatible SDK environment during install. 
Note that if &ndash;enable-java-home is used, &ndash;with-arch-directory=ARCH must also
be specified.

     <br><dt><code>--with-arch-directory=ARCH</code><dd>Specifies the name to use for the <samp><span class="file">jre/lib/ARCH</span></samp> directory in the SDK
environment created when &ndash;enable-java-home is passed. Typical names for this
directory include i386, amd64, ia64, etc.

     <br><dt><code>--with-os-directory=DIR</code><dd>Specifies the OS directory for the SDK include directory. This is set to auto
detect, and is typically 'linux'.

     <br><dt><code>--with-origin-name=NAME</code><dd>Specifies the JPackage origin name. This defaults to the 'gcj' in
java-1.5.0-gcj.

     <br><dt><code>--with-arch-suffix=SUFFIX</code><dd>Specifies the suffix for the sdk directory. Defaults to the empty string. 
Examples include '.x86_64' in 'java-1.5.0-gcj-1.5.0.0.x86_64'.

     <br><dt><code>--with-jvm-root-dir=DIR</code><dd>Specifies where to install the SDK. Default is $(prefix)/lib/jvm.

     <br><dt><code>--with-jvm-jar-dir=DIR</code><dd>Specifies where to install jars. Default is $(prefix)/lib/jvm-exports.

     <br><dt><code>--with-python-dir=DIR</code><dd>Specifies where to install the Python modules used for aot-compile. DIR should
not include the prefix used in installation. For example, if the Python modules
are to be installed in /usr/lib/python2.5/site-packages, then
&ndash;with-python-dir=/lib/python2.5/site-packages should be passed. If this is
not specified, then the Python modules are installed in $(prefix)/share/python.

     <br><dt><code>--enable-aot-compile-rpm</code><dd>Adds aot-compile-rpm to the list of installed scripts.

     <br><dt><code>--enable-browser-plugin</code><dd>Build the gcjwebplugin web browser plugin.

     <br><dt><code>--enable-static-libjava</code><dd>Build static libraries in libjava. The default is to only build shared
libraries.

          <dl>
<dt><code>ansi</code><dd>Use the single-byte <code>char</code> and the Win32 A functions natively,
translating to and from UNICODE when using these functions.  If
unspecified, this is the default.

          <br><dt><code>unicows</code><dd>Use the <code>WCHAR</code> and Win32 W functions natively.  Adds
<code>-lunicows</code> to <samp><span class="file">libgcj.spec</span></samp> to link with &lsquo;<samp><span class="samp">libunicows</span></samp>&rsquo;. 
<samp><span class="file">unicows.dll</span></samp> needs to be deployed on Microsoft Windows 9X machines
running built executables.  <samp><span class="file">libunicows.a</span></samp>, an open-source
import library around Microsoft's <code>unicows.dll</code>, is obtained from
<a href="http://libunicows.sourceforge.net/">http://libunicows.sourceforge.net/</a>, which also gives details
on getting <samp><span class="file">unicows.dll</span></samp> from Microsoft.

          <br><dt><code>unicode</code><dd>Use the <code>WCHAR</code> and Win32 W functions natively.  Does <em>not</em>
add <code>-lunicows</code> to <samp><span class="file">libgcj.spec</span></samp>.  The built executables will
only run on Microsoft Windows NT and above. 
</dl>
     </dl>

<h5 class="subsubheading"><a name="TOC6"></a>AWT-Specific Options</h5>

     <dl>
<dt><code>--with-x</code><dd>Use the X Window System.

     <br><dt><code>--enable-java-awt=PEER(S)</code><dd>Specifies the AWT peer library or libraries to build alongside
&lsquo;<samp><span class="samp">libgcj</span></samp>&rsquo;.  If this option is unspecified or disabled, AWT
will be non-functional.  Current valid values are <samp><span class="option">gtk</span></samp> and
<samp><span class="option">xlib</span></samp>.  Multiple libraries should be separated by a
comma (i.e. <samp><span class="option">--enable-java-awt=gtk,xlib</span></samp>).

     <br><dt><code>--enable-gtk-cairo</code><dd>Build the cairo Graphics2D implementation on GTK.

     <br><dt><code>--enable-java-gc=TYPE</code><dd>Choose garbage collector.  Defaults to <samp><span class="option">boehm</span></samp> if unspecified.

     <br><dt><code>--disable-gtktest</code><dd>Do not try to compile and run a test GTK+ program.

     <br><dt><code>--disable-glibtest</code><dd>Do not try to compile and run a test GLIB program.

     <br><dt><code>--with-libart-prefix=PFX</code><dd>Prefix where libart is installed (optional).

     <br><dt><code>--with-libart-exec-prefix=PFX</code><dd>Exec prefix where libart is installed (optional).

     <br><dt><code>--disable-libarttest</code><dd>Do not try to compile and run a test libart program.

</dl>

<h5 class="subsubheading"><a name="TOC7"></a>Overriding <samp><span class="command">configure</span></samp> test results</h5>

<p>Sometimes, it might be necessary to override the result of some
<samp><span class="command">configure</span></samp> test, for example in order to ease porting to a new
system or work around a bug in a test.  The toplevel <samp><span class="command">configure</span></samp>
script provides three variables for this:

     <dl>
<dt><code>build_configargs</code><dd><a name="index-g_t_0040code_007bbuild_005fconfigargs_007d-3"></a>The contents of this variable is passed to all build <samp><span class="command">configure</span></samp>
scripts.

     <br><dt><code>host_configargs</code><dd><a name="index-g_t_0040code_007bhost_005fconfigargs_007d-4"></a>The contents of this variable is passed to all host <samp><span class="command">configure</span></samp>
scripts.

     <br><dt><code>target_configargs</code><dd><a name="index-g_t_0040code_007btarget_005fconfigargs_007d-5"></a>The contents of this variable is passed to all target <samp><span class="command">configure</span></samp>
scripts.

   </dl>

   <p>In order to avoid shell and <samp><span class="command">make</span></samp> quoting issues for complex
overrides, you can pass a setting for <samp><span class="env">CONFIG_SITE</span></samp> and set
variables in the site file.

   <p><hr />
<p><a href="./index.html">Return to the GCC Installation page</a>

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