aarch64-linux-gnu-4.9/share/doc/gccinstall/configure.html - toolchains/linux-x86/gcc - Git at Google

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 <h1 class="settitle" align="center">Installing GCC</h1>


 <a name="index-Configuration"></a>
 <a name="index-Installing-GCC_003a-Configuration"></a>

 <p>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>
 <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>
 <p>If you obtained the sources via SVN, <var>srcdir</var> must refer to the top
 <samp>gcc</samp> directory, the one where the <samp>MAINTAINERS</samp> file can be
 found, and not its <samp>gcc</samp> subdirectory, otherwise the build will fail.
 </p>
 <p>If either <var>srcdir</var> or <var>objdir</var> is located on an automounted NFS
 file system, the shell&rsquo;s built-in <code>pwd</code> command will return
 temporary pathnames.  Using these can lead to various sorts of build
 problems.  To avoid this issue, set the <code>PWDCMD</code> environment
 variable to an automounter-aware <code>pwd</code> command, e.g.,
 <code>pawd</code> or &lsquo;<samp>amq -w</samp>&rsquo;, during the configuration and build
 phases.
 </p>
 <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&rsquo;t
 get extensive testing; building where <var>objdir</var> is a subdirectory
 of <var>srcdir</var> is unsupported.
 </p>
 <p>If you have previously built GCC in the same directory for a
 different target machine, do &lsquo;<samp>make distclean</samp>&rsquo; to delete all files
 that might be invalid.  One of the files this deletes is <samp>Makefile</samp>;
 if &lsquo;<samp>make distclean</samp>&rsquo; complains that <samp>Makefile</samp> does not exist
 or issues a message like &ldquo;don&rsquo;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>
 <p>Second, when configuring a native system, either <code>cc</code> or
 <code>gcc</code> must be in your path or you must set <code>CC</code> in
 your environment before running configure.  Otherwise the configuration
 scripts may fail.
 </p>

 <p>To configure GCC:
 </p>
 <div class="smallexample">
 <pre class="smallexample">% mkdir <var>objdir</var>
 % cd <var>objdir</var>
 % <var>srcdir</var>/configure [<var>options</var>] [<var>target</var>]
 </pre></div>

 <a name="Distributor-options"></a>
 <h3 class="heading">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.
 </p>
 <dl compact="compact">
 <dt><code>--with-pkgversion=<var>version</var></code></dt>
 <dd><p>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 <code>gcc --version</code>.  This suffix does
 not replace the default version string, only the &lsquo;<samp>GCC</samp>&rsquo; part.
 </p>
 <p>The default value is &lsquo;<samp>GCC</samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--with-bugurl=<var>url</var></code></dt>
 <dd><p>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>
 <p>The default value refers to the FSF&rsquo;s GCC bug tracker.
 </p>
 </dd>
 </dl>

 <a name="Target-specification"></a>
 <h3 class="heading">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><li> <var>target</var> must be specified as <samp>--target=<var>target</var></samp>
 when configuring a cross compiler; examples of valid targets would be
 m68k-elf, sh-elf, etc.

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


 <a name="Options-specification"></a>
 <h3 class="heading">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>configure
 --help</samp>&rsquo; may list other options, but those not listed below may not
 work and should not normally be used.
 </p>
 <p>Note that each <samp>--enable</samp> option has a corresponding
 <samp>--disable</samp> option and that each <samp>--with</samp> option has a
 corresponding <samp>--without</samp> option.
 </p>
 <dl compact="compact">
 <dt><code>--prefix=<var>dirname</var></code></dt>
 <dd><p>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>/usr/local</samp>.
 </p>
 <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&rsquo;s home directory tree, some shells will not expand
 <var>dirname</var> correctly if it contains the &lsquo;<samp>~</samp>&rsquo; metacharacter; use
 <code>$HOME</code> instead.
 </p>
 <p>The following standard <code>autoconf</code> options are supported.  Normally you
 should not need to use these options.
 </p><dl compact="compact">
 <dt><code>--exec-prefix=<var>dirname</var></code></dt>
 <dd><p>Specify the toplevel installation directory for architecture-dependent
 files.  The default is <samp><var>prefix</var></samp>.
 </p>
 </dd>
 <dt><code>--bindir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for the executables called by users
 (such as <code>gcc</code> and <code>g++</code>).  The default is
 <samp><var>exec-prefix</var>/bin</samp>.
 </p>
 </dd>
 <dt><code>--libdir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for object code libraries and
 internal data files of GCC.  The default is <samp><var>exec-prefix</var>/lib</samp>.
 </p>
 </dd>
 <dt><code>--libexecdir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for internal executables of GCC.
 The default is <samp><var>exec-prefix</var>/libexec</samp>.
 </p>
 </dd>
 <dt><code>--with-slibdir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for the shared libgcc library.  The
 default is <samp><var>libdir</var></samp>.
 </p>
 </dd>
 <dt><code>--datarootdir=<var>dirname</var></code></dt>
 <dd><p>Specify the root of the directory tree for read-only architecture-independent
 data files referenced by GCC.  The default is <samp><var>prefix</var>/share</samp>.
 </p>
 </dd>
 <dt><code>--infodir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for documentation in info format.
 The default is <samp><var>datarootdir</var>/info</samp>.
 </p>
 </dd>
 <dt><code>--datadir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for some architecture-independent
 data files referenced by GCC.  The default is <samp><var>datarootdir</var></samp>.
 </p>
 </dd>
 <dt><code>--docdir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for documentation files (other
 than Info) for GCC.  The default is <samp><var>datarootdir</var>/doc</samp>.
 </p>
 </dd>
 <dt><code>--htmldir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for HTML documentation files.
 The default is <samp><var>docdir</var></samp>.
 </p>
 </dd>
 <dt><code>--pdfdir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for PDF documentation files.
 The default is <samp><var>docdir</var></samp>.
 </p>
 </dd>
 <dt><code>--mandir=<var>dirname</var></code></dt>
 <dd><p>Specify the installation directory for manual pages.  The default is
 <samp><var>datarootdir</var>/man</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.)
 </p>
 </dd>
 <dt><code>--with-gxx-include-dir=<var>dirname</var></code></dt>
 <dd><p>Specify
 the installation directory for G++ header files.  The default depends
 on other configuration options, and differs between cross and native
 configurations.
 </p>
 </dd>
 <dt><code>--with-specs=<var>specs</var></code></dt>
 <dd><p>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&rsquo;s source code, for instance
 <samp>--with-specs=%{!fcommon:%{!fno-common:-fno-common}}</samp>.
 See &ldquo;Spec Files&rdquo; in the main manual
 </p>
 </dd>
 </dl>

 </dd>
 <dt><code>--program-prefix=<var>prefix</var></code></dt>
 <dd><p>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>--program-prefix=foo-</samp> would result in &lsquo;<samp>gcc</samp>&rsquo;
 being installed as <samp>/usr/local/bin/foo-gcc</samp>.
 </p>
 </dd>
 <dt><code>--program-suffix=<var>suffix</var></code></dt>
 <dd><p>Appends <var>suffix</var> to the names of programs to install in <var>bindir</var>
 (see above).  For example, specifying <samp>--program-suffix=-3.1</samp>
 would result in &lsquo;<samp>gcc</samp>&rsquo; being installed as
 <samp>/usr/local/bin/gcc-3.1</samp>.
 </p>
 </dd>
 <dt><code>--program-transform-name=<var>pattern</var></code></dt>
 <dd><p>Applies the &lsquo;<samp>sed</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>sed</samp>&rsquo; editing commands, separated by
 semicolons.  For example, if you want the &lsquo;<samp>gcc</samp>&rsquo; program name to be
 transformed to the installed program <samp>/usr/local/bin/myowngcc</samp> and
 the &lsquo;<samp>g++</samp>&rsquo; program name to be transformed to
 <samp>/usr/local/bin/gspecial++</samp> without changing other program names,
 you could use the pattern
 <samp>--program-transform-name='s/^gcc$/myowngcc/; s/^g++$/gspecial++/'</samp>
 to achieve this effect.
 </p>
 <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>
 <p>As currently implemented, this option only takes effect for native
 builds; cross compiler binaries&rsquo; names are not transformed even when a
 transformation is explicitly asked for by one of these options.
 </p>
 <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>i686-pc-linux-gnu-gcc</samp>&rsquo;.  All of the above transformations happen
 before the target alias is prepended to the name&mdash;so, specifying
 <samp>--program-prefix=foo-</samp> and <samp>program-suffix=-3.1</samp>, the
 resulting binary would be installed as
 <samp>/usr/local/bin/i686-pc-linux-gnu-foo-gcc-3.1</samp>.
 </p>
 <p>As a last shortcoming, none of the installed Ada programs are
 transformed yet, which will be fixed in some time.
 </p>
 </dd>
 <dt><code>--with-local-prefix=<var>dirname</var></code></dt>
 <dd><p>Specify the
 installation directory for local include files.  The default is
 <samp>/usr/local</samp>.  Specify this option if you want the compiler to
 search directory <samp><var>dirname</var>/include</samp> for locally installed
 header files <em>instead</em> of <samp>/usr/local/include</samp>.
 </p>
 <p>You should specify <samp>--with-local-prefix</samp> <strong>only</strong> if your
 site has a different convention (not <samp>/usr/local</samp>) for where to put
 site-specific files.
 </p>
 <p>The default value for <samp>--with-local-prefix</samp> is <samp>/usr/local</samp>
 regardless of the value of <samp>--prefix</samp>.  Specifying
 <samp>--prefix</samp> has no effect on which directory GCC searches for
 local header files.  This may seem counterintuitive, but actually it is
 logical.
 </p>
 <p>The purpose of <samp>--prefix</samp> is to specify where to <em>install
 GCC</em>.  The local header files in <samp>/usr/local/include</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>--prefix</samp> value.)
 </p>
 <p>Both the local-prefix include directory and the GCC-prefix include
 directory are part of GCC&rsquo;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>
 <p>Some autoconf macros add <samp>-I <var>directory</var></samp> options to the
 compiler command line, to ensure that directories containing installed
 packages&rsquo; headers are searched.  When <var>directory</var> is one of GCC&rsquo;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>
 <p>GCC automatically searches for ordinary libraries using
 <code>GCC_EXEC_PREFIX</code>.  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>/usr</samp>.
 </p>
 <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>--program-prefix</samp>, <samp>--program-suffix</samp> and
 <samp>--program-transform-name</samp> options to install multiple versions
 into a single directory, but it may be simpler to use different prefixes
 and the <samp>--with-local-prefix</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 <code>LIBRARY_PATH</code>).
 </p>
 <p>The same value can be used for both <samp>--with-local-prefix</samp> and
 <samp>--prefix</samp> provided it is not <samp>/usr</samp>.  This can be used
 to avoid the default search of <samp>/usr/local/include</samp>.
 </p>
 <p><strong>Do not</strong> specify <samp>/usr</samp> as the <samp>--with-local-prefix</samp>!
 The directory you use for <samp>--with-local-prefix</samp> <strong>must not</strong>
 contain any of the system&rsquo;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 <code>fixincludes</code> script.
 </p>
 <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.
 </p>
 </dd>
 <dt><code>--with-native-system-header-dir=<var>dirname</var></code></dt>
 <dd><p>Specifies that <var>dirname</var> is the directory that contains native system
 header files, rather than <samp>/usr/include</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>--with-sysroot</samp> option and will cause GCC to search
 <var>dirname</var> inside the system root specified by that option.
 </p>
 </dd>
 <dt><code>--enable-shared[=<var>package</var>[,&hellip;]]</code></dt>
 <dd><p>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>
 <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>libgcc</samp>&rsquo; (also known as &lsquo;<samp>gcc</samp>&rsquo;), &lsquo;<samp>libstdc++</samp>&rsquo; (not
 &lsquo;<samp>libstdc++-v3</samp>&rsquo;), &lsquo;<samp>libffi</samp>&rsquo;, &lsquo;<samp>zlib</samp>&rsquo;, &lsquo;<samp>boehm-gc</samp>&rsquo;,
 &lsquo;<samp>ada</samp>&rsquo;, &lsquo;<samp>libada</samp>&rsquo;, &lsquo;<samp>libjava</samp>&rsquo;, &lsquo;<samp>libgo</samp>&rsquo;, and &lsquo;<samp>libobjc</samp>&rsquo;.
 Note &lsquo;<samp>libiberty</samp>&rsquo; does not support shared libraries at all.
 </p>
 <p>Use <samp>--disable-shared</samp> to build only static libraries.  Note that
 <samp>--disable-shared</samp> does not accept a list of package names as
 argument, only <samp>--enable-shared</samp> does.
 </p>
 <p>Contrast with <samp>--enable-host-shared</samp>, which affects <em>host</em>
 code.
 </p>
 </dd>
 <dt><code>--enable-host-shared</code></dt>
 <dd><p>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>
 <p>Currently this option is only of use to people developing GCC itself.
 </p>
 <p>Contrast with <samp>--enable-shared</samp>, which affects <em>target</em>
 libraries.
 </p>
 </dd>
 <dt><code><a name="with_002dgnu_002das"></a>--with-gnu-as</code></dt>
 <dd><p>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>--with-gnu-as</samp>.)  If you have more than one
 assembler installed on your system, you may want to use this option in
 connection with <samp>--with-as=<var>pathname</var></samp> or
 <samp>--with-build-time-tools=<var>pathname</var></samp>.
 </p>
 <p>The following systems are the only ones where it makes a difference
 whether you use the GNU assembler.  On any other system,
 <samp>--with-gnu-as</samp> has no effect.
 </p>
 <ul>
 <li> &lsquo;<samp>hppa1.0-<var>any</var>-<var>any</var></samp>&rsquo;
 </li><li> &lsquo;<samp>hppa1.1-<var>any</var>-<var>any</var></samp>&rsquo;
 </li><li> &lsquo;<samp>sparc-sun-solaris2.<var>any</var></samp>&rsquo;
 </li><li> &lsquo;<samp>sparc64-<var>any</var>-solaris2.<var>any</var></samp>&rsquo;
 </li></ul>

 </dd>
 <dt><code><a name="with_002das"></a>--with-as=<var>pathname</var></code></dt>
 <dd><p>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:
 </p><ul>
 <li> Unless GCC is being built with a cross compiler, check the
 <samp><var>libexec</var>/gcc/<var>target</var>/<var>version</var></samp> directory.
 <var>libexec</var> defaults to <samp><var>exec-prefix</var>/libexec</samp>;
 <var>exec-prefix</var> defaults to <var>prefix</var>, which
 defaults to <samp>/usr/local</samp> unless overridden by the
 <samp>--prefix=<var>pathname</var></samp> switch described above.  <var>target</var>
 is the target system triple, such as &lsquo;<samp>sparc-sun-solaris2.7</samp>&rsquo;, and
 <var>version</var> denotes the GCC version, such as 3.0.

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

 </li><li> Check in the <code>PATH</code> for a tool whose name is prefixed by the
 target system triple.

 </li><li> Check in the <code>PATH</code> 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).
 </li></ul>

 <p>You may want to use <samp>--with-as</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.
 </p>
 </dd>
 <dt><code><a name="with_002dgnu_002dld"></a>--with-gnu-ld</code></dt>
 <dd><p>Same as <a href="#with-gnu-as"><samp>--with-gnu-as</samp></a>
 but for the linker.
 </p>
 </dd>
 <dt><code>--with-ld=<var>pathname</var></code></dt>
 <dd><p>Same as <a href="#with-as"><samp>--with-as</samp></a>
 but for the linker.
 </p>
 </dd>
 <dt><code>--with-stabs</code></dt>
 <dd><p>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>
 <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>
 <p>Normally, GCC uses the ECOFF debugging format by default; if you
 prefer BSD stabs, specify <samp>--with-stabs</samp> when you configure GCC.
 </p>
 <p>No matter which default you choose when you configure GCC, the user
 can use the <samp>-gcoff</samp> and <samp>-gstabs+</samp> options to specify explicitly
 the debug format for a particular compilation.
 </p>
 <p><samp>--with-stabs</samp> is meaningful on the ISC system on the 386, also, if
 <samp>--with-gas</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>
 <p><samp>--with-stabs</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.
 </p>
 </dd>
 <dt><code>--with-tls=<var>dialect</var></code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-multiarch</code></dt>
 <dd><p>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>--with-sysroot</samp>, and without
 <samp>--with-native-system-header-dir</samp>.
 More documentation about multiarch can be found at
 <a href="http://wiki.debian.org/Multiarch">http://wiki.debian.org/Multiarch</a>.
 </p>
 </dd>
 <dt><code>--enable-vtable-verify</code></dt>
 <dd><p>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>--disable-libvtv</samp> to turn off building libvtv).
 <samp>--disable-vtable-verify</samp> is the default.
 </p>
 </dd>
 <dt><code>--disable-multilib</code></dt>
 <dd><p>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>
 <p>Some targets provide finer-grained control over which multilibs are built
 (e.g., <samp>--disable-softfloat</samp>):
 </p><dl compact="compact">
 <dt><code>arm-*-*</code></dt>
 <dd><p>fpu, 26bit, underscore, interwork, biendian, nofmult.
 </p>
 </dd>
 <dt><code>m68*-*-*</code></dt>
 <dd><p>softfloat, m68881, m68000, m68020.
 </p>
 </dd>
 <dt><code>mips*-*-*</code></dt>
 <dd><p>single-float, biendian, softfloat.
 </p>
 </dd>
 <dt><code>powerpc*-*-*, rs6000*-*-*</code></dt>
 <dd><p>aix64, pthread, softfloat, powercpu, powerpccpu, powerpcos, biendian,
 sysv, aix.
 </p>
 </dd>
 </dl>

 </dd>
 <dt><code>--with-multilib-list=<var>list</var></code></dt>
 <dt><code>--without-multilib-list</code></dt>
 <dd><p>Specify what multilibs to build.
 Currently only implemented for sh*-*-* and x86-64-*-linux*.
 </p>
 <dl compact="compact">
 <dt><code>sh*-*-*</code></dt>
 <dd><p><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>--with-endian</samp>.
 </p>
 <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>
 <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>MULTILIB_EXCLUDES</samp>&rsquo;
 (once the leading <code>!</code> has been stripped).
 </p>
 <p>If <samp>--with-multilib-list</samp> is not given, then a default set of
 multilibs is selected based on the value of <samp>--target</samp>.  This is
 usually the complete set of libraries, but some targets imply a more
 specialized subset.
 </p>
 <p>Example 1: to configure a compiler for SH4A only, but supporting both
 endians, with little endian being the default:
 </p><div class="smallexample">
 <pre class="smallexample">--with-cpu=sh4a --with-endian=little,big --with-multilib-list=
 </pre></div>

 <p>Example 2: to configure a compiler for both SH4A and SH4AL-DSP, but with
 only little endian SH4AL:
 </p><div class="smallexample">
 <pre class="smallexample">--with-cpu=sh4a --with-endian=little,big \
 --with-multilib-list=sh4al,!mb/m4al
 </pre></div>

 </dd>
 <dt><code>x86-64-*-linux*</code></dt>
 <dd><p><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>
 <p>If <samp>--with-multilib-list</samp> is not given, then only 32-bit and
 64-bit run-time libraries will be enabled.
 </p></dd>
 </dl>

 </dd>
 <dt><code>--with-endian=<var>endians</var></code></dt>
 <dd><p>Specify what endians to use.
 Currently only implemented for sh*-*-*.
 </p>
 <p><var>endians</var> may be one of the following:
 </p><dl compact="compact">
 <dt><code>big</code></dt>
 <dd><p>Use big endian exclusively.
 </p></dd>
 <dt><code>little</code></dt>
 <dd><p>Use little endian exclusively.
 </p></dd>
 <dt><code>big,little</code></dt>
 <dd><p>Use big endian by default.  Provide a multilib for little endian.
 </p></dd>
 <dt><code>little,big</code></dt>
 <dd><p>Use little endian by default.  Provide a multilib for big endian.
 </p></dd>
 </dl>

 </dd>
 <dt><code>--enable-threads</code></dt>
 <dd><p>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>
 <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>--enable-threads</samp> is an
 alias for <samp>--enable-threads=single</samp>.
 </p>
 </dd>
 <dt><code>--disable-threads</code></dt>
 <dd><p>Specify that threading support should be disabled for the system.
 This is an alias for <samp>--enable-threads=single</samp>.
 </p>
 </dd>
 <dt><code>--enable-threads=<var>lib</var></code></dt>
 <dd><p>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:
 </p>
 <dl compact="compact">
 <dt><code>aix</code></dt>
 <dd><p>AIX thread support.
 </p></dd>
 <dt><code>dce</code></dt>
 <dd><p>DCE thread support.
 </p></dd>
 <dt><code>lynx</code></dt>
 <dd><p>LynxOS thread support.
 </p></dd>
 <dt><code>mipssde</code></dt>
 <dd><p>MIPS SDE thread support.
 </p></dd>
 <dt><code>no</code></dt>
 <dd><p>This is an alias for &lsquo;<samp>single</samp>&rsquo;.
 </p></dd>
 <dt><code>posix</code></dt>
 <dd><p>Generic POSIX/Unix98 thread support.
 </p></dd>
 <dt><code>rtems</code></dt>
 <dd><p>RTEMS thread support.
 </p></dd>
 <dt><code>single</code></dt>
 <dd><p>Disable thread support, should work for all platforms.
 </p></dd>
 <dt><code>tpf</code></dt>
 <dd><p>TPF thread support.
 </p></dd>
 <dt><code>vxworks</code></dt>
 <dd><p>VxWorks thread support.
 </p></dd>
 <dt><code>win32</code></dt>
 <dd><p>Microsoft Win32 API thread support.
 </p></dd>
 </dl>

 </dd>
 <dt><code>--enable-tls</code></dt>
 <dd><p>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>--enable-tls</samp> or <samp>--disable-tls</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.
 </p>
 </dd>
 <dt><code>--disable-tls</code></dt>
 <dd><p>Specify that the target does not support TLS.
 This is an alias for <samp>--enable-tls=no</samp>.
 </p>
 </dd>
 <dt><code>--with-cpu=<var>cpu</var></code></dt>
 <dt><code>--with-cpu-32=<var>cpu</var></code></dt>
 <dt><code>--with-cpu-64=<var>cpu</var></code></dt>
 <dd><p>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>-mcpu=</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>--with-cpu-32</samp> and
 <samp>--with-cpu-64</samp> options specify separate default CPUs for
 32-bit and 64-bit modes; these options are only supported for i386,
 x86-64 and PowerPC.
 </p>
 </dd>
 <dt><code>--with-schedule=<var>cpu</var></code></dt>
 <dt><code>--with-arch=<var>cpu</var></code></dt>
 <dt><code>--with-arch-32=<var>cpu</var></code></dt>
 <dt><code>--with-arch-64=<var>cpu</var></code></dt>
 <dt><code>--with-tune=<var>cpu</var></code></dt>
 <dt><code>--with-tune-32=<var>cpu</var></code></dt>
 <dt><code>--with-tune-64=<var>cpu</var></code></dt>
 <dt><code>--with-abi=<var>abi</var></code></dt>
 <dt><code>--with-fpu=<var>type</var></code></dt>
 <dt><code>--with-float=<var>type</var></code></dt>
 <dd><p>These configure options provide default values for the <samp>-mschedule=</samp>,
 <samp>-march=</samp>, <samp>-mtune=</samp>, <samp>-mabi=</samp>, and <samp>-mfpu=</samp>
 options and for <samp>-mhard-float</samp> or <samp>-msoft-float</samp>.  As with
 <samp>--with-cpu</samp>, which switches will be accepted and acceptable values
 of the arguments depend on the target.
 </p>
 </dd>
 <dt><code>--with-mode=<var>mode</var></code></dt>
 <dd><p>Specify if the compiler should default to <samp>-marm</samp> or <samp>-mthumb</samp>.
 This option is only supported on ARM targets.
 </p>
 </dd>
 <dt><code>--with-stack-offset=<var>num</var></code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--with-fpmath=<var>isa</var></code></dt>
 <dd><p>This options sets <samp>-mfpmath=sse</samp> by default and specifies the default
 ISA for floating-point arithmetics.  You can select either &lsquo;<samp>sse</samp>&rsquo; which
 enables <samp>-msse2</samp> or &lsquo;<samp>avx</samp>&rsquo; which enables <samp>-mavx</samp> by default.
 This option is only supported on i386 and x86-64 targets.
 </p>
 </dd>
 <dt><code>--with-nan=<var>encoding</var></code></dt>
 <dd><p>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:
 </p><dl compact="compact">
 <dt><code>legacy</code></dt>
 <dd><p>Use the legacy encoding, as with the <samp>-mnan=legacy</samp> command-line
 option.
 </p></dd>
 <dt><code>2008</code></dt>
 <dd><p>Use the 754-2008 encoding, as with the <samp>-mnan=2008</samp> command-line
 option.
 </p></dd>
 </dl>
 <p>To use this configuration option you must have an assembler version
 installed that supports the <samp>-mnan=</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>-mnan=2008</samp> and
 <samp>-mnan=legacy</samp> command-line options has been used.
 </p>
 </dd>
 <dt><code>--with-divide=<var>type</var></code></dt>
 <dd><p>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:
 </p><dl compact="compact">
 <dt><code>traps</code></dt>
 <dd><p>Division by zero checks use conditional traps (this is the default on
 systems that support conditional traps).
 </p></dd>
 <dt><code>breaks</code></dt>
 <dd><p>Division by zero checks use the break instruction.
 </p></dd>
 </dl>


 </dd>
 <dt><code>--with-llsc</code></dt>
 <dd><p>On MIPS targets, make <samp>-mllsc</samp> the default when no
 <samp>-mno-llsc</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.
 </p>
 </dd>
 <dt><code>--without-llsc</code></dt>
 <dd><p>On MIPS targets, make <samp>-mno-llsc</samp> the default when no
 <samp>-mllsc</samp> option is passed.
 </p>
 </dd>
 <dt><code>--with-synci</code></dt>
 <dd><p>On MIPS targets, make <samp>-msynci</samp> the default when no
 <samp>-mno-synci</samp> option is passed.
 </p>
 </dd>
 <dt><code>--without-synci</code></dt>
 <dd><p>On MIPS targets, make <samp>-mno-synci</samp> the default when no
 <samp>-msynci</samp> option is passed.  This is the default.
 </p>
 </dd>
 <dt><code>--with-mips-plt</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-__cxa_atexit</code></dt>
 <dd><p>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>-fuse-cxa-atexit</samp> to be passed by default.
 </p>
 </dd>
 <dt><code>--enable-gnu-indirect-function</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-target-optspace</code></dt>
 <dd><p>Specify that target
 libraries should be optimized for code space instead of code speed.
 This is the default for the m32r platform.
 </p>
 </dd>
 <dt><code>--with-cpp-install-dir=<var>dirname</var></code></dt>
 <dd><p>Specify that the user visible <code>cpp</code> program should be installed
 in <samp><var>prefix</var>/<var>dirname</var>/cpp</samp>, in addition to <var>bindir</var>.
 </p>
 </dd>
 <dt><code>--enable-comdat</code></dt>
 <dd><p>Enable COMDAT group support.  This is primarily used to override the
 automatically detected value.
 </p>
 </dd>
 <dt><code>--enable-initfini-array</code></dt>
 <dd><p>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>--disable-initfini-array</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.
 </p>
 </dd>
 <dt><code>--enable-link-mutex</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-maintainer-mode</code></dt>
 <dd><p>The build rules that regenerate the Autoconf and Automake output files as
 well as the GCC master message catalog <samp>gcc.pot</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>--enable-maintainer-mode</samp> will enable
 this.  Note that you need a recent version of the <code>gettext</code> tools
 to do so.
 </p>
 </dd>
 <dt><code>--disable-bootstrap</code></dt>
 <dd><p>For a native build, the default configuration is to perform
 a 3-stage bootstrap of the compiler when &lsquo;<samp>make</samp>&rsquo; is invoked,
 testing that GCC can compile itself correctly.  If you want to disable
 this process, you can configure with <samp>--disable-bootstrap</samp>.
 </p>
 </dd>
 <dt><code>--enable-bootstrap</code></dt>
 <dd><p>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>--enable-bootstrap</samp>.
 </p>
 </dd>
 <dt><code>--enable-generated-files-in-srcdir</code></dt>
 <dd><p>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>
 <p>If you configure with <samp>--enable-generated-files-in-srcdir</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.
 </p>
 </dd>
 <dt><code>--enable-version-specific-runtime-libs</code></dt>
 <dd><p>Specify
 that runtime libraries should be installed in the compiler specific
 subdirectory (<samp><var>libdir</var>/gcc</samp>) rather than the usual places.  In
 addition, &lsquo;<samp>libstdc++</samp>&rsquo;&rsquo;s include files will be installed into
 <samp><var>libdir</var></samp> unless you overruled it by using
 <samp>--with-gxx-include-dir=<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>libgfortran</samp>&rsquo;,
 &lsquo;<samp>libjava</samp>&rsquo;, &lsquo;<samp>libstdc++</samp>&rsquo;, and &lsquo;<samp>libobjc</samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--enable-languages=<var>lang1</var>,<var>lang2</var>,&hellip;</code></dt>
 <dd><p>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>gcc</samp> directory of your GCC source tree:<br>
 </p><div class="smallexample">
 <pre class="smallexample">grep language= */config-lang.in
 </pre></div>
 <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>gcc</samp> sub-tree will be configured.
 Ada, Go and Objective-C++ are not default languages; the rest are.
 </p>
 </dd>
 <dt><code>--enable-stage1-languages=<var>lang1</var>,<var>lang2</var>,&hellip;</code></dt>
 <dd><p>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>--enable-languages</samp>, and the option <code>all</code> will select all
 of the languages enabled by <samp>--enable-languages</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 <code>make
 stage1-bubble all-target</code>, or run the testsuite on the stage-1 compiler
 for the specified languages using <code>make stage1-start check-gcc</code>.
 </p>
 </dd>
 <dt><code>--disable-libada</code></dt>
 <dd><p>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>make -C gcc gnatlib_and_tools</samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--disable-libsanitizer</code></dt>
 <dd><p>Specify that the run-time libraries for the various sanitizers should
 not be built.
 </p>
 </dd>
 <dt><code>--disable-libssp</code></dt>
 <dd><p>Specify that the run-time libraries for stack smashing protection
 should not be built.
 </p>
 </dd>
 <dt><code>--disable-libquadmath</code></dt>
 <dd><p>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>--disable-libquadmath-support</samp>
 is used.
 </p>
 </dd>
 <dt><code>--disable-libquadmath-support</code></dt>
 <dd><p>Specify that the Fortran front end and <code>libgfortran</code> do not add
 support for <code>libquadmath</code> on systems supporting it.
 </p>
 </dd>
 <dt><code>--disable-libgomp</code></dt>
 <dd><p>Specify that the run-time libraries used by GOMP should not be built.
 </p>
 </dd>
 <dt><code>--disable-libvtv</code></dt>
 <dd><p>Specify that the run-time libraries used by vtable verification
 should not be built.
 </p>
 </dd>
 <dt><code>--with-dwarf2</code></dt>
 <dd><p>Specify that the compiler should
 use DWARF 2 debugging information as the default.
 </p>
 </dd>
 <dt><code>--enable-targets=all</code></dt>
 <dt><code>--enable-targets=<var>target_list</var></code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-secureplt</code></dt>
 <dd><p>This option enables <samp>-msecure-plt</samp> by default for powerpc-linux.
 See &ldquo;RS/6000 and PowerPC Options&rdquo; in the main manual
 </p>
 </dd>
 <dt><code>--enable-cld</code></dt>
 <dd><p>This option enables <samp>-mcld</samp> by default for 32-bit x86 targets.
 See &ldquo;i386 and x86-64 Options&rdquo; in the main manual
 </p>
 </dd>
 <dt><code>--enable-win32-registry</code></dt>
 <dt><code>--enable-win32-registry=<var>key</var></code></dt>
 <dt><code>--disable-win32-registry</code></dt>
 <dd><p>The <samp>--enable-win32-registry</samp> option enables Microsoft Windows-hosted GCC
 to look up installations paths in the registry using the following key:
 </p>
 <div class="smallexample">
 <pre class="smallexample"><code>HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\<var>key</var></code>
 </pre></div>

 <p><var>key</var> defaults to GCC version number, and can be overridden by the
 <samp>--enable-win32-registry=<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>--disable-win32-registry</samp>
 option.  This option has no effect on the other hosts.
 </p>
 </dd>
 <dt><code>--nfp</code></dt>
 <dd><p>Specify that the machine does not have a floating point unit.  This
 option only applies to &lsquo;<samp>m68k-sun-sunos<var>n</var></samp>&rsquo;.  On any other
 system, <samp>--nfp</samp> has no effect.
 </p>
 </dd>
 <dt><code>--enable-werror</code></dt>
 <dt><code>--disable-werror</code></dt>
 <dt><code>--enable-werror=yes</code></dt>
 <dt><code>--enable-werror=no</code></dt>
 <dd><p>When you specify this option, it controls whether certain files in the
 compiler are built with <samp>-Werror</samp> in bootstrap stage2 and later.
 If you don&rsquo;t specify it, <samp>-Werror</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>-Werror</samp> are
 controlled by the Makefiles.
 </p>
 </dd>
 <dt><code>--enable-checking</code></dt>
 <dt><code>--enable-checking=<var>list</var></code></dt>
 <dd><p>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>yes</samp>&rsquo; by default when building
 from SVN or snapshots, but &lsquo;<samp>release</samp>&rsquo; for releases.  The default
 for building the stage1 compiler is &lsquo;<samp>yes</samp>&rsquo;.  More control
 over the checks may be had by specifying <var>list</var>.  The categories of
 checks available are &lsquo;<samp>yes</samp>&rsquo; (most common checks
 &lsquo;<samp>assert,misc,tree,gc,rtlflag,runtime</samp>&rsquo;), &lsquo;<samp>no</samp>&rsquo; (no checks at
 all), &lsquo;<samp>all</samp>&rsquo; (all but &lsquo;<samp>valgrind</samp>&rsquo;), &lsquo;<samp>release</samp>&rsquo; (cheapest
 checks &lsquo;<samp>assert,runtime</samp>&rsquo;) or &lsquo;<samp>none</samp>&rsquo; (same as &lsquo;<samp>no</samp>&rsquo;).
 Individual checks can be enabled with these flags &lsquo;<samp>assert</samp>&rsquo;,
 &lsquo;<samp>df</samp>&rsquo;, &lsquo;<samp>fold</samp>&rsquo;, &lsquo;<samp>gc</samp>&rsquo;, &lsquo;<samp>gcac</samp>&rsquo; &lsquo;<samp>misc</samp>&rsquo;, &lsquo;<samp>rtl</samp>&rsquo;,
 &lsquo;<samp>rtlflag</samp>&rsquo;, &lsquo;<samp>runtime</samp>&rsquo;, &lsquo;<samp>tree</samp>&rsquo;, and &lsquo;<samp>valgrind</samp>&rsquo;.
 </p>
 <p>The &lsquo;<samp>valgrind</samp>&rsquo; check requires the external <code>valgrind</code>
 simulator, available from <a href="http://valgrind.org/">http://valgrind.org/</a>.  The
 &lsquo;<samp>df</samp>&rsquo;, &lsquo;<samp>rtl</samp>&rsquo;, &lsquo;<samp>gcac</samp>&rsquo; and &lsquo;<samp>valgrind</samp>&rsquo; checks are very expensive.
 To disable all checking, &lsquo;<samp>--disable-checking</samp>&rsquo; or
 &lsquo;<samp>--enable-checking=none</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.
 </p>
 </dd>
 <dt><code>--disable-stage1-checking</code></dt>
 <dt><code>--enable-stage1-checking</code></dt>
 <dt><code>--enable-stage1-checking=<var>list</var></code></dt>
 <dd><p>If no <samp>--enable-checking</samp> option is specified the stage1
 compiler will be built with &lsquo;<samp>yes</samp>&rsquo; checking enabled, otherwise
 the stage1 checking flags are the same as specified by
 <samp>--enable-checking</samp>.  To build the stage1 compiler with
 different checking options use <samp>--enable-stage1-checking</samp>.
 The list of checking options is the same as for <samp>--enable-checking</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>--disable-stage1-checking</samp>&rsquo;
 to disable checking for the stage1 compiler.
 </p>
 </dd>
 <dt><code>--enable-coverage</code></dt>
 <dt><code>--enable-coverage=<var>level</var></code></dt>
 <dd><p>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>opt</samp>&rsquo; and &lsquo;<samp>noopt</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.
 </p>
 </dd>
 <dt><code>--enable-gather-detailed-mem-stats</code></dt>
 <dd><p>When this option is specified more detailed information on memory
 allocation is gathered.  This information is printed when using
 <samp>-fmem-report</samp>.
 </p>
 </dd>
 <dt><code>--enable-nls</code></dt>
 <dt><code>--disable-nls</code></dt>
 <dd><p>The <samp>--enable-nls</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>--disable-nls</samp> option disables NLS.
 </p>
 </dd>
 <dt><code>--with-included-gettext</code></dt>
 <dd><p>If NLS is enabled, the <samp>--with-included-gettext</samp> option causes the build
 procedure to prefer its copy of GNU <code>gettext</code>.
 </p>
 </dd>
 <dt><code>--with-catgets</code></dt>
 <dd><p>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&rsquo;s copy of the GNU
 <code>gettext</code> library.  The <samp>--with-catgets</samp> option causes the
 build procedure to use the host&rsquo;s <code>catgets</code> in this situation.
 </p>
 </dd>
 <dt><code>--with-libiconv-prefix=<var>dir</var></code></dt>
 <dd><p>Search for libiconv header files in <samp><var>dir</var>/include</samp> and
 libiconv library files in <samp><var>dir</var>/lib</samp>.
 </p>
 </dd>
 <dt><code>--enable-obsolete</code></dt>
 <dd><p>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>
 <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.
 </p>
 </dd>
 <dt><code>--enable-decimal-float</code></dt>
 <dt><code>--enable-decimal-float=yes</code></dt>
 <dt><code>--enable-decimal-float=no</code></dt>
 <dt><code>--enable-decimal-float=bid</code></dt>
 <dt><code>--enable-decimal-float=dpd</code></dt>
 <dt><code>--disable-decimal-float</code></dt>
 <dd><p>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>bid</samp>&rsquo; or &lsquo;<samp>dpd</samp>&rsquo;).  The &lsquo;<samp>bid</samp>&rsquo; (binary integer decimal)
 format is default on i386 and x86_64 systems, and the &lsquo;<samp>dpd</samp>&rsquo;
 (densely packed decimal) format is default on PowerPC systems.
 </p>
 </dd>
 <dt><code>--enable-fixed-point</code></dt>
 <dt><code>--disable-fixed-point</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--with-long-double-128</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--with-gmp=<var>pathname</var></code></dt>
 <dt><code>--with-gmp-include=<var>pathname</var></code></dt>
 <dt><code>--with-gmp-lib=<var>pathname</var></code></dt>
 <dt><code>--with-mpfr=<var>pathname</var></code></dt>
 <dt><code>--with-mpfr-include=<var>pathname</var></code></dt>
 <dt><code>--with-mpfr-lib=<var>pathname</var></code></dt>
 <dt><code>--with-mpc=<var>pathname</var></code></dt>
 <dt><code>--with-mpc-include=<var>pathname</var></code></dt>
 <dt><code>--with-mpc-lib=<var>pathname</var></code></dt>
 <dd><p>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>--with-gmp=<var>gmpinstalldir</var></samp>&rsquo;,
 &lsquo;<samp>--with-mpfr=<var>mpfrinstalldir</var></samp>&rsquo;,
 &lsquo;<samp>--with-mpc=<var>mpcinstalldir</var></samp>&rsquo;).  The
 <samp>--with-gmp=<var>gmpinstalldir</var></samp> option is shorthand for
 <samp>--with-gmp-lib=<var>gmpinstalldir</var>/lib</samp> and
 <samp>--with-gmp-include=<var>gmpinstalldir</var>/include</samp>.  Likewise the
 <samp>--with-mpfr=<var>mpfrinstalldir</var></samp> option is shorthand for
 <samp>--with-mpfr-lib=<var>mpfrinstalldir</var>/lib</samp> and
 <samp>--with-mpfr-include=<var>mpfrinstalldir</var>/include</samp>, also the
 <samp>--with-mpc=<var>mpcinstalldir</var></samp> option is shorthand for
 <samp>--with-mpc-lib=<var>mpcinstalldir</var>/lib</samp> and
 <samp>--with-mpc-include=<var>mpcinstalldir</var>/include</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 (<code>LD_LIBRARY_PATH</code> on GNU/Linux and Solaris systems).
 </p>
 <p>These flags are applicable to the host platform only.  When building
 a cross compiler, they will not be used to configure target libraries.
 </p>
 </dd>
 <dt><code>--with-isl=<var>pathname</var></code></dt>
 <dt><code>--with-isl-include=<var>pathname</var></code></dt>
 <dt><code>--with-isl-lib=<var>pathname</var></code></dt>
 <dt><code>--with-cloog=<var>pathname</var></code></dt>
 <dt><code>--with-cloog-include=<var>pathname</var></code></dt>
 <dt><code>--with-cloog-lib=<var>pathname</var></code></dt>
 <dd><p>If you do not have ISL and the CLooG
 libraries installed in a standard location and you want to build GCC,
 you can explicitly specify the directory where they are installed
 (&lsquo;<samp>--with-isl=<var>islinstalldir</var></samp>&rsquo;,
 &lsquo;<samp>--with-cloog=<var>clooginstalldir</var></samp>&rsquo;). The
 <samp>--with-isl=<var>islinstalldir</var></samp> option is shorthand for
 <samp>--with-isl-lib=<var>islinstalldir</var>/lib</samp> and
 <samp>--with-isl-include=<var>islinstalldir</var>/include</samp>.  Likewise the
 <samp>--with-cloog=<var>clooginstalldir</var></samp> option is shorthand for
 <samp>--with-cloog-lib=<var>clooginstalldir</var>/lib</samp> and
 <samp>--with-cloog-include=<var>clooginstalldir</var>/include</samp>.  If these
 shorthand assumptions are not correct, you can use the explicit
 include and lib options directly.
 </p>
 <p>These flags are applicable to the host platform only.  When building
 a cross compiler, they will not be used to configure target libraries.
 </p>
 </dd>
 <dt><code>--with-host-libstdcxx=<var>linker-args</var></code></dt>
 <dd><p>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>-lstdc++</samp>&rsquo; or &lsquo;<samp>-Wl,-Bstatic,-lstdc++,-Bdynamic -lm</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.
 </p>
 </dd>
 <dt><code>--with-stage1-ldflags=<var>flags</var></code></dt>
 <dd><p>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>--disable-bootstrap</samp>.  By default no special flags are used.
 </p>
 </dd>
 <dt><code>--with-stage1-libs=<var>libs</var></code></dt>
 <dd><p>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>--disable-bootstrap</samp>.  The default is the argument to
 <samp>--with-host-libstdcxx</samp>, if specified.
 </p>
 </dd>
 <dt><code>--with-boot-ldflags=<var>flags</var></code></dt>
 <dd><p>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>-static-libstdc++ -static-libgcc</samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--with-boot-libs=<var>libs</var></code></dt>
 <dd><p>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>--with-host-libstdcxx</samp>, if specified.
 </p>
 </dd>
 <dt><code>--with-debug-prefix-map=<var>map</var></code></dt>
 <dd><p>Convert source directory names using <samp>-fdebug-prefix-map</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>=<var>new</var></samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--enable-linker-build-id</code></dt>
 <dd><p>Tells GCC to pass <samp>--build-id</samp> option to the linker for all final
 links (links performed without the <samp>-r</samp> or <samp>--relocatable</samp>
 option), if the linker supports it.  If you specify
 <samp>--enable-linker-build-id</samp>, but your linker does not
 support <samp>--build-id</samp> option, a warning is issued and the
 <samp>--enable-linker-build-id</samp> option is ignored.  The default is off.
 </p>
 </dd>
 <dt><code>--with-linker-hash-style=<var>choice</var></code></dt>
 <dd><p>Tells GCC to pass <samp>--hash-style=<var>choice</var></samp> option to the
 linker for all final links. <var>choice</var> can be one of
 &lsquo;<samp>sysv</samp>&rsquo;, &lsquo;<samp>gnu</samp>&rsquo;, and &lsquo;<samp>both</samp>&rsquo; where &lsquo;<samp>sysv</samp>&rsquo; is the default.
 </p>
 </dd>
 <dt><code>--enable-gnu-unique-object</code></dt>
 <dt><code>--disable-gnu-unique-object</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-lto</code></dt>
 <dt><code>--disable-lto</code></dt>
 <dd><p>Enable support for link-time optimization (LTO).  This is enabled by
 default, and may be disabled using <samp>--disable-lto</samp>.
 </p>
 </dd>
 <dt><code>--with-plugin-ld=<var>pathname</var></code></dt>
 <dd><p>Enable an alternate linker to be used at link-time optimization (LTO)
 link time when <samp>-fuse-linker-plugin</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>-fuse-linker-plugin</samp> for details.
 </p>
 </dd>
 <dt><code>--enable-canonical-system-headers</code></dt>
 <dt><code>--disable-canonical-system-headers</code></dt>
 <dd><p>Enable system header path canonicalization for <samp>libcpp</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>--disable-canonical-system-headers</samp>.
 </p>
 </dd>
 <dt><code>--with-glibc-version=<var>major</var>.<var>minor</var></code></dt>
 <dd><p>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&rsquo;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>
 <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.
 </p></dd>
 </dl>

 <a name="Cross_002dCompiler_002dSpecific-Options"></a>
 <h4 class="subheading">Cross-Compiler-Specific Options</h4>
 <p>The following options only apply to building cross compilers.
 </p>
 <dl compact="compact">
 <dt><code>--with-sysroot</code></dt>
 <dt><code>--with-sysroot=<var>dir</var></code></dt>
 <dd><p>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>--sysroot=<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>--with-headers</samp> and
 <samp>--with-libs</samp> that this option obsoletes.  The default value,
 in case <samp>--with-sysroot</samp> is not given an argument, is
 <samp>${gcc_tooldir}/sys-root</samp>.  If the specified directory is a
 subdirectory of <samp>${exec_prefix}</samp>, then it will be found relative to
 the GCC binaries if the installation tree is moved.
 </p>
 <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>
 <p>If you specify the <samp>--with-native-system-header-dir=<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>/usr/include</samp>.
 </p>
 </dd>
 <dt><code>--with-build-sysroot</code></dt>
 <dt><code>--with-build-sysroot=<var>dir</var></code></dt>
 <dd><p>Tells GCC to consider <var>dir</var> as the system root (see
 <samp>--with-sysroot</samp>) while building target libraries, instead of
 the directory specified with <samp>--with-sysroot</samp>.  This option is
 only useful when you are already using <samp>--with-sysroot</samp>.  You
 can use <samp>--with-build-sysroot</samp> when you are configuring with
 <samp>--prefix</samp> set to a directory that is different from the one in
 which you are installing GCC and your target libraries.
 </p>
 <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>
 <p>If you specify the <samp>--with-native-system-header-dir=<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>/usr/include</samp>.
 </p>
 </dd>
 <dt><code>--with-headers</code></dt>
 <dt><code>--with-headers=<var>dir</var></code></dt>
 <dd><p>Deprecated in favor of <samp>--with-sysroot</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>gcc</samp> install
 directory.  <em>This option with the <var>dir</var> argument is required</em> when
 building a cross compiler, if <samp><var>prefix</var>/<var>target</var>/sys-include</samp>
 doesn&rsquo;t pre-exist.  If <samp><var>prefix</var>/<var>target</var>/sys-include</samp> does
 pre-exist, the <var>dir</var> argument may be omitted.  <code>fixincludes</code>
 will be run on these files to make them compatible with GCC.
 </p>
 </dd>
 <dt><code>--without-headers</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--with-libs</code></dt>
 <dt><code>--with-libs=&quot;<var>dir1</var> <var>dir2</var> &hellip; <var>dirN</var>&quot;</code></dt>
 <dd><p>Deprecated in favor of <samp>--with-sysroot</samp>.
 Specifies a list of directories which contain the target runtime
 libraries.  These libraries will be copied into the <samp>gcc</samp> install
 directory.  If the directory list is omitted, this option has no
 effect.
 </p>
 </dd>
 <dt><code>--with-newlib</code></dt>
 <dd><p>Specifies that &lsquo;<samp>newlib</samp>&rsquo; is
 being used as the target C library.  This causes <code>__eprintf</code> to be
 omitted from <samp>libgcc.a</samp> on the assumption that it will be provided by
 &lsquo;<samp>newlib</samp>&rsquo;.
 </p>
 </dd>
 <dt><code>--with-avrlibc</code></dt>
 <dd><p>Specifies that &lsquo;<samp>AVR-Libc</samp>&rsquo; is
 being used as the target C library.  This causes float support
 functions like <code>__addsf3</code> to be omitted from <samp>libgcc.a</samp> on
 the assumption that it will be provided by <samp>libm.a</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.
 </p>
 </dd>
 <dt><code>--with-nds32-lib=<var>library</var></code></dt>
 <dd><p>Specifies that <var>library</var> setting is used for building <samp>libgcc.a</samp>.
 Currently, the valid <var>library</var> is &lsquo;<samp>newlib</samp>&rsquo; or &lsquo;<samp>mculib</samp>&rsquo;.
 This option is only supported for the NDS32 target.
 </p>
 </dd>
 <dt><code>--with-build-time-tools=<var>dir</var></code></dt>
 <dd><p>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>
 <p>For example, on an &lsquo;<samp>ia64-hp-hpux</samp>&rsquo; system, you may have the GNU
 assembler and linker in <samp>/usr/bin</samp>, and the native tools in a
 different path, and build a toolchain that expects to find the
 native tools in <samp>/usr/bin</samp>.
 </p>
 <p>When you use this option, you should ensure that <var>dir</var> includes
 <code>ar</code>, <code>as</code>, <code>ld</code>, <code>nm</code>,
 <code>ranlib</code> and <code>strip</code> if necessary, and possibly
 <code>objdump</code>.  Otherwise, GCC may use an inconsistent set of
 tools.
 </p></dd>
 </dl>

 <a name="Java_002dSpecific-Options"></a>
 <h4 class="subheading">Java-Specific Options</h4>

 <p>The following option applies to the build of the Java front end.
 </p>
 <dl compact="compact">
 <dt><code>--disable-libgcj</code></dt>
 <dd><p>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&rsquo;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&rsquo;re known to not work on
 the target platform.  If GCJ is enabled but &lsquo;<samp>libgcj</samp>&rsquo; isn&rsquo;t built, you
 may need to port it; in this case, before modifying the top-level
 <samp>configure.in</samp> so that &lsquo;<samp>libgcj</samp>&rsquo; is enabled by default on this platform,
 you may use <samp>--enable-libgcj</samp> to override the default.
 </p>
 </dd>
 </dl>

 <p>The following options apply to building &lsquo;<samp>libgcj</samp>&rsquo;.
 </p>
 <a name="General-Options"></a>
 <h4 class="subsubheading">General Options</h4>

 <dl compact="compact">
 <dt><code>--enable-java-maintainer-mode</code></dt>
 <dd><p>By default the &lsquo;<samp>libjava</samp>&rsquo; build will not attempt to compile the
 <samp>.java</samp> source files to <samp>.class</samp>.  Instead, it will use the
 <samp>.class</samp> files from the source tree.  If you use this option you
 must have executables named <code>ecj1</code> and <code>gjavah</code> in your path
 for use by the build.  You must use this option if you intend to
 modify any <samp>.java</samp> files in <samp>libjava</samp>.
 </p>
 </dd>
 <dt><code>--with-java-home=<var>dirname</var></code></dt>
 <dd><p>This &lsquo;<samp>libjava</samp>&rsquo; option overrides the default value of the
 &lsquo;<samp>java.home</samp>&rsquo; system property.  It is also used to set
 &lsquo;<samp>sun.boot.class.path</samp>&rsquo; to <samp><var>dirname</var>/lib/rt.jar</samp>.  By
 default &lsquo;<samp>java.home</samp>&rsquo; is set to <samp><var>prefix</var></samp> and
 &lsquo;<samp>sun.boot.class.path</samp>&rsquo; to
 <samp><var>datadir</var>/java/libgcj-<var>version</var>.jar</samp>.
 </p>
 </dd>
 <dt><code>--with-ecj-jar=<var>filename</var></code></dt>
 <dd><p>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 <code>gcj</code> to parse
 <samp>.java</samp> source files.  If this option is given, the
 &lsquo;<samp>libjava</samp>&rsquo; build will create and install an <samp>ecj1</samp> executable
 which uses this jar file at runtime.
 </p>
 <p>If this option is not given, but an <samp>ecj.jar</samp> file is found in
 the topmost source tree at configure time, then the &lsquo;<samp>libgcj</samp>&rsquo;
 build will create and install <samp>ecj1</samp>, and will also install the
 discovered <samp>ecj.jar</samp> into a suitable place in the install tree.
 </p>
 <p>If <samp>ecj1</samp> is not installed, then the user will have to supply one
 on his path in order for <code>gcj</code> to properly parse <samp>.java</samp>
 source files.  A suitable jar is available from
 <a href="ftp://sourceware.org/pub/java/">ftp://sourceware.org/pub/java/</a>.
 </p>
 </dd>
 <dt><code>--disable-getenv-properties</code></dt>
 <dd><p>Don&rsquo;t set system properties from <code>GCJ_PROPERTIES</code>.
 </p>
 </dd>
 <dt><code>--enable-hash-synchronization</code></dt>
 <dd><p>Use a global hash table for monitor locks.  Ordinarily,
 &lsquo;<samp>libgcj</samp>&rsquo;&rsquo;s &lsquo;<samp>configure</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.
 </p>
 </dd>
 <dt><code>--enable-interpreter</code></dt>
 <dd><p>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>--disable-interpreter</samp>).
 </p>
 </dd>
 <dt><code>--disable-java-net</code></dt>
 <dd><p>Disable java.net.  This disables the native part of java.net only,
 using non-functional stubs for native method implementations.
 </p>
 </dd>
 <dt><code>--disable-jvmpi</code></dt>
 <dd><p>Disable JVMPI support.
 </p>
 </dd>
 <dt><code>--disable-libgcj-bc</code></dt>
 <dd><p>Disable BC ABI compilation of certain parts of libgcj.  By default,
 some portions of libgcj are compiled with <samp>-findirect-dispatch</samp>
 and <samp>-fno-indirect-classes</samp>, allowing them to be overridden at
 run-time.
 </p>
 <p>If <samp>--disable-libgcj-bc</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.
 </p>
 </dd>
 <dt><code>--enable-reduced-reflection</code></dt>
 <dd><p>Build most of libgcj with <samp>-freduced-reflection</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).
 </p>
 </dd>
 <dt><code>--with-ecos</code></dt>
 <dd><p>Enable runtime eCos target support.
 </p>
 </dd>
 <dt><code>--without-libffi</code></dt>
 <dd><p>Don&rsquo;t use &lsquo;<samp>libffi</samp>&rsquo;.  This will disable the interpreter and JNI
 support as well, as these require &lsquo;<samp>libffi</samp>&rsquo; to work.
 </p>
 </dd>
 <dt><code>--enable-libgcj-debug</code></dt>
 <dd><p>Enable runtime debugging code.
 </p>
 </dd>
 <dt><code>--enable-libgcj-multifile</code></dt>
 <dd><p>If specified, causes all <samp>.java</samp> source files to be
 compiled into <samp>.class</samp> files in one invocation of
 &lsquo;<samp>gcj</samp>&rsquo;.  This can speed up build time, but is more
 resource-intensive.  If this option is unspecified or
 disabled, &lsquo;<samp>gcj</samp>&rsquo; is invoked once for each <samp>.java</samp>
 file to compile into a <samp>.class</samp> file.
 </p>
 </dd>
 <dt><code>--with-libiconv-prefix=DIR</code></dt>
 <dd><p>Search for libiconv in <samp>DIR/include</samp> and <samp>DIR/lib</samp>.
 </p>
 </dd>
 <dt><code>--enable-sjlj-exceptions</code></dt>
 <dd><p>Force use of the <code>setjmp</code>/<code>longjmp</code>-based scheme for exceptions.
 &lsquo;<samp>configure</samp>&rsquo; ordinarily picks the correct value based on the platform.
 Only use this option if you are sure you need a different setting.
 </p>
 </dd>
 <dt><code>--with-system-zlib</code></dt>
 <dd><p>Use installed &lsquo;<samp>zlib</samp>&rsquo; rather than that included with GCC.
 </p>
 </dd>
 <dt><code>--with-win32-nlsapi=ansi, unicows or unicode</code></dt>
 <dd><p>Indicates how MinGW &lsquo;<samp>libgcj</samp>&rsquo; translates between UNICODE
 characters and the Win32 API.
 </p>
 </dd>
 <dt><code>--enable-java-home</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--with-arch-directory=ARCH</code></dt>
 <dd><p>Specifies the name to use for the <samp>jre/lib/ARCH</samp> directory in the SDK
 environment created when &ndash;enable-java-home is passed. Typical names for this
 directory include i386, amd64, ia64, etc.
 </p>
 </dd>
 <dt><code>--with-os-directory=DIR</code></dt>
 <dd><p>Specifies the OS directory for the SDK include directory. This is set to auto
 detect, and is typically &rsquo;linux&rsquo;.
 </p>
 </dd>
 <dt><code>--with-origin-name=NAME</code></dt>
 <dd><p>Specifies the JPackage origin name. This defaults to the &rsquo;gcj&rsquo; in
 java-1.5.0-gcj.
 </p>
 </dd>
 <dt><code>--with-arch-suffix=SUFFIX</code></dt>
 <dd><p>Specifies the suffix for the sdk directory. Defaults to the empty string.
 Examples include &rsquo;.x86_64&rsquo; in &rsquo;java-1.5.0-gcj-1.5.0.0.x86_64&rsquo;.
 </p>
 </dd>
 <dt><code>--with-jvm-root-dir=DIR</code></dt>
 <dd><p>Specifies where to install the SDK. Default is $(prefix)/lib/jvm.
 </p>
 </dd>
 <dt><code>--with-jvm-jar-dir=DIR</code></dt>
 <dd><p>Specifies where to install jars. Default is $(prefix)/lib/jvm-exports.
 </p>
 </dd>
 <dt><code>--with-python-dir=DIR</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>--enable-aot-compile-rpm</code></dt>
 <dd><p>Adds aot-compile-rpm to the list of installed scripts.
 </p>
 </dd>
 <dt><code>--enable-browser-plugin</code></dt>
 <dd><p>Build the gcjwebplugin web browser plugin.
 </p>
 </dd>
 <dt><code>--enable-static-libjava</code></dt>
 <dd><p>Build static libraries in libjava. The default is to only build shared
 libraries.
 </p>
 <dl compact="compact">
 <dt><code>ansi</code></dt>
 <dd><p>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.
 </p>
 </dd>
 <dt><code>unicows</code></dt>
 <dd><p>Use the <code>WCHAR</code> and Win32 W functions natively.  Adds
 <code>-lunicows</code> to <samp>libgcj.spec</samp> to link with &lsquo;<samp>libunicows</samp>&rsquo;.
 <samp>unicows.dll</samp> needs to be deployed on Microsoft Windows 9X machines
 running built executables.  <samp>libunicows.a</samp>, an open-source
 import library around Microsoft&rsquo;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>unicows.dll</samp> from Microsoft.
 </p>
 </dd>
 <dt><code>unicode</code></dt>
 <dd><p>Use the <code>WCHAR</code> and Win32 W functions natively.  Does <em>not</em>
 add <code>-lunicows</code> to <samp>libgcj.spec</samp>.  The built executables will
 only run on Microsoft Windows NT and above.
 </p></dd>
 </dl>
 </dd>
 </dl>

 <a name="AWT_002dSpecific-Options"></a>
 <h4 class="subsubheading">AWT-Specific Options</h4>

 <dl compact="compact">
 <dt><code>--with-x</code></dt>
 <dd><p>Use the X Window System.
 </p>
 </dd>
 <dt><code>--enable-java-awt=PEER(S)</code></dt>
 <dd><p>Specifies the AWT peer library or libraries to build alongside
 &lsquo;<samp>libgcj</samp>&rsquo;.  If this option is unspecified or disabled, AWT
 will be non-functional.  Current valid values are <samp>gtk</samp> and
 <samp>xlib</samp>.  Multiple libraries should be separated by a
 comma (i.e. <samp>--enable-java-awt=gtk,xlib</samp>).
 </p>
 </dd>
 <dt><code>--enable-gtk-cairo</code></dt>
 <dd><p>Build the cairo Graphics2D implementation on GTK.
 </p>
 </dd>
 <dt><code>--enable-java-gc=TYPE</code></dt>
 <dd><p>Choose garbage collector.  Defaults to <samp>boehm</samp> if unspecified.
 </p>
 </dd>
 <dt><code>--disable-gtktest</code></dt>
 <dd><p>Do not try to compile and run a test GTK+ program.
 </p>
 </dd>
 <dt><code>--disable-glibtest</code></dt>
 <dd><p>Do not try to compile and run a test GLIB program.
 </p>
 </dd>
 <dt><code>--with-libart-prefix=PFX</code></dt>
 <dd><p>Prefix where libart is installed (optional).
 </p>
 </dd>
 <dt><code>--with-libart-exec-prefix=PFX</code></dt>
 <dd><p>Exec prefix where libart is installed (optional).
 </p>
 </dd>
 <dt><code>--disable-libarttest</code></dt>
 <dd><p>Do not try to compile and run a test libart program.
 </p>
 </dd>
 </dl>

 <a name="Overriding-configure-test-results"></a>
 <h4 class="subsubheading">Overriding <code>configure</code> test results</h4>

 <p>Sometimes, it might be necessary to override the result of some
 <code>configure</code> test, for example in order to ease porting to a new
 system or work around a bug in a test.  The toplevel <code>configure</code>
 script provides three variables for this:
 </p>
 <dl compact="compact">
 <dt><code>build_configargs</code></dt>
 <dd><a name="index-build_005fconfigargs"></a>
 <p>The contents of this variable is passed to all build <code>configure</code>
 scripts.
 </p>
 </dd>
 <dt><code>host_configargs</code></dt>
 <dd><a name="index-host_005fconfigargs"></a>
 <p>The contents of this variable is passed to all host <code>configure</code>
 scripts.
 </p>
 </dd>
 <dt><code>target_configargs</code></dt>
 <dd><a name="index-target_005fconfigargs"></a>
 <p>The contents of this variable is passed to all target <code>configure</code>
 scripts.
 </p>
 </dd>
 </dl>

 <p>In order to avoid shell and <code>make</code> quoting issues for complex
 overrides, you can pass a setting for <code>CONFIG_SITE</code> and set
 variables in the site file.
 </p>
 <hr />
 <p><p><a href="./index.html">Return to the GCC Installation page</a>
 </p>


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