# Installing GCC: Configuration

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.

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

If you obtained the sources by cloning the repository, srcdir must refer to the top `gcc` directory, the one where the `MAINTAINERS` file can be found, and not its `gcc` subdirectory, otherwise the build will fail.

If either srcdir or objdir is located on an automounted NFS file system, the shell’s built-in `pwd` command will return temporary pathnames. Using these can lead to various sorts of build problems. To avoid this issue, set the `PWDCMD` environment variable to an automounter-aware `pwd` command, e.g., `pawd` or ‘`amq -w`’, during the configuration and build phases.

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

If you have previously built GCC in the same directory for a different target machine, do ‘`make distclean`’ to delete all files that might be invalid. One of the files this deletes is `Makefile`; if ‘`make distclean`’ complains that `Makefile` does not exist or issues a message like “don’t know how to make distclean” it probably means that the directory is already suitably clean. However, with the recommended method of building in a separate objdir, you should simply use a different objdir for each target.

Second, when configuring a native system, either `cc` or `gcc` must be in your path or you must set `CC` in your environment before running configure. Otherwise the configuration scripts may fail.

To configure GCC:

    % mkdir objdir
    % cd objdir
    % srcdir/configure [options] [target]

### Distributor options

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.

`--with-pkgversion=version`

  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 `gcc --version`. This suffix does not replace the default version string, only the ‘`GCC`’ part.

  The default value is ‘`GCC`’.

`--with-bugurl=url`

  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.

  The default value refers to the FSF’s GCC bug tracker.

`--with-documentation-root-url=url`

  Specify the URL root that contains GCC option documentation. The url should end with a `/` character.

  The default value is https://gcc.gnu.org/onlinedocs/.

`--with-changes-root-url=url`

  Specify the URL root that contains information about changes in GCC releases like `gcc-version/changes.html`. The url should end with a `/` character.

  The default value is https://gcc.gnu.org/.

### Host, Build and Target specification

Specify the host, build and target machine configurations. You do this when you run the `configure` script.

The build machine is the system which you are using, the host machine is the system where you want to run the resulting compiler (normally the build machine), and the target machine is the system for which you want the compiler to generate code.

If you are building a compiler to produce code for the machine it runs on (a native compiler), you normally do not need to specify any operands to `configure`; it will try to guess the type of machine you are on and use that as the build, host and target machines. So you don’t need to specify a configuration when building a native compiler unless `configure` cannot figure out what your configuration is or guesses wrong.

In those cases, specify the build machine’s configuration name with the `--host` option; the host and target will default to be the same as the host machine.

Here is an example:

    ./configure --host=x86_64-pc-linux-gnu

A configuration name may be canonical or it may be more or less abbreviated (`config.sub` script produces canonical versions).

A canonical configuration name has three parts, separated by dashes. It looks like this: ‘`cpu-company-system`’.

Here are the possible CPU types:

> aarch64, aarch64_be, alpha, alpha64, amdgcn, arc, arceb, arm, armeb, avr, bfin, bpf, cris, csky, epiphany, fido, fr30, frv, ft32, h8300, hppa, hppa2.0, hppa64, i486, i686, ia64, iq2000, lm32, loongarch64, m32c, m32r, m32rle, m68k, mcore, microblaze, microblazeel, mips, mips64, mips64el, mips64octeon, mips64orion, mips64vr, mipsel, mipsisa32, mipsisa32r2, mipsisa64, mipsisa64r2, mipsisa64r2el, mipsisa64sb1, mipsisa64sr71k, mipstx39, mmix, mn10300, moxie, msp430, nds32be, nds32le, nios2, nvptx, or1k, pdp11, powerpc, powerpc64, powerpc64le, powerpcle, pru, riscv32, riscv32be, riscv64, riscv64be, rl78, rx, s390, s390x, sh, shle, sparc, sparc64, tic6x, v850, v850e, v850e1, vax, visium, x86_64, xstormy16, xtensa

Here is a list of system types:

> aixversion, amdhsa, aout, cygwin, darwinversion, eabi, eabialtivec, eabisim, eabisimaltivec, elf, elf32, elfbare, elfoabi, freebsdversion, gnu, hpux, hpuxversion, kfreebsd-gnu, kopensolaris-gnu, linux-androideabi, linux-gnu, linux-gnu_altivec, linux-musl, linux-uclibc, lynxos, mingw32, mingw32crt, mmixware, msdosdjgpp, netbsd, netbsdelfversion, nto-qnx, openbsd, rtems, solarisversion, symbianelf, tpf, uclinux, uclinux_eabi, vms, vxworks, vxworksae, vxworksmils

### Options specification

Use options to override several configure time options for GCC. A list of supported options follows; ‘`configure --help`’ may list other options, but those not listed below may not work and should not normally be used.

Note that each `--enable` option has a corresponding `--disable` option and that each `--with` option has a corresponding `--without` option.

`--prefix=dirname`

  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 `/usr/local`.

  We highly recommend against dirname being the same or a subdirectory of objdir or vice versa. If specifying a directory beneath a user’s home directory tree, some shells will not expand dirname correctly if it contains the ‘`~`’ metacharacter; use `$HOME` instead.

  The following standard `autoconf` options are supported. Normally you should not need to use these options.

  `--exec-prefix=dirname`

    Specify the toplevel installation directory for architecture-dependent files. The default is `prefix`.

  `--bindir=dirname`

    Specify the installation directory for the executables called by users (such as `gcc` and `g++`). The default is `exec-prefix/bin`.

  `--libdir=dirname`

    Specify the installation directory for object code libraries and internal data files of GCC. The default is `exec-prefix/lib`.

  `--libexecdir=dirname`

    Specify the installation directory for internal executables of GCC. The default is `exec-prefix/libexec`.

  `--with-slibdir=dirname`

    Specify the installation directory for the shared libgcc library. The default is `libdir`.

  `--datarootdir=dirname`

    Specify the root of the directory tree for read-only architecture-independent data files referenced by GCC. The default is `prefix/share`.

  `--infodir=dirname`

    Specify the installation directory for documentation in info format. The default is `datarootdir/info`.

  `--datadir=dirname`

    Specify the installation directory for some architecture-independent data files referenced by GCC. The default is `datarootdir`.

  `--docdir=dirname`

    Specify the installation directory for documentation files (other than Info) for GCC. The default is `datarootdir/doc`.

  `--htmldir=dirname`

    Specify the installation directory for HTML documentation files. The default is `docdir`.

  `--pdfdir=dirname`

    Specify the installation directory for PDF documentation files. The default is `docdir`.

  `--mandir=dirname`

    Specify the installation directory for manual pages. The default is `datarootdir/man`. (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.)

  `--with-gxx-include-dir=dirname`

    Specify the installation directory for G++ header files. The default depends on other configuration options, and differs between cross and native configurations.

  `--with-specs=specs`

    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 `--with-specs=%{!fcommon:%{!fno-common:-fno-common}}`. See “Spec Files” in the main manual

`--program-prefix=prefix`

  GCC supports some transformations of the names of its programs when installing them. This option prepends prefix to the names of programs to install in bindir (see above). For example, specifying `--program-prefix=foo-` would result in ‘`gcc`’ being installed as `/usr/local/bin/foo-gcc`.

`--program-suffix=suffix`

  Appends suffix to the names of programs to install in bindir (see above). For example, specifying `--program-suffix=-3.1` would result in ‘`gcc`’ being installed as `/usr/local/bin/gcc-3.1`.

`--program-transform-name=pattern`

  Applies the ‘`sed`’ script pattern to be applied to the names of programs to install in bindir (see above). pattern has to consist of one or more basic ‘`sed`’ editing commands, separated by semicolons. For example, if you want the ‘`gcc`’ program name to be transformed to the installed program `/usr/local/bin/myowngcc` and the ‘`g++`’ program name to be transformed to `/usr/local/bin/gspecial++` without changing other program names, you could use the pattern `--program-transform-name='s/^gcc$/myowngcc/; s/^g++$/gspecial++/'` to achieve this effect.

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

  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.

  For native builds, some of the installed programs are also installed with the target alias in front of their name, as in ‘`i686-pc-linux-gnu-gcc`’. All of the above transformations happen before the target alias is prepended to the name—so, specifying `--program-prefix=foo-` and `program-suffix=-3.1`, the resulting binary would be installed as `/usr/local/bin/i686-pc-linux-gnu-foo-gcc-3.1`.

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

`--with-local-prefix=dirname`

  Specify the installation directory for local include files. The default is `/usr/local`. Specify this option if you want the compiler to search directory `dirname/include` for locally installed header files instead of `/usr/local/include`.

  You should specify `--with-local-prefix` only if your site has a different convention (not `/usr/local`) for where to put site-specific files.

  The default value for `--with-local-prefix` is `/usr/local` regardless of the value of `--prefix`. Specifying `--prefix` has no effect on which directory GCC searches for local header files. This may seem counterintuitive, but actually it is logical.

  The purpose of `--prefix` is to specify where to install GCC. The local header files in `/usr/local/include`—if you put any in that directory—are not part of GCC. They are part of other programs—perhaps many others. (GCC installs its own header files in another directory which is based on the `--prefix` value.)

  Both the local-prefix include directory and the GCC-prefix include directory are part of GCC’s “system include” 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.

  Some autoconf macros add `-I directory` options to the compiler command line, to ensure that directories containing installed packages’ headers are searched. When directory 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.

  GCC automatically searches for ordinary libraries using `GCC_EXEC_PREFIX`. 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 `/usr`.

  Sites that need to install multiple versions of GCC may not want to use the above simple configuration. It is possible to use the `--program-prefix`, `--program-suffix` and `--program-transform-name` options to install multiple versions into a single directory, but it may be simpler to use different prefixes and the `--with-local-prefix` 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 `LIBRARY_PATH`).

  The same value can be used for both `--with-local-prefix` and `--prefix` provided it is not `/usr`. This can be used to avoid the default search of `/usr/local/include`.

  Do not specify `/usr` as the `--with-local-prefix`! The directory you use for `--with-local-prefix` must not 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 `fixincludes` script.

  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.

`--with-gcc-major-version-only`

  Specifies that GCC should use only the major number rather than major.minor.patchlevel in filesystem paths.

`--with-native-system-header-dir=dirname`

  Specifies that dirname is the directory that contains native system header files, rather than `/usr/include`. 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 `--with-sysroot` option and will cause GCC to search dirname inside the system root specified by that option.

`--enable-shared[=package[,…]]`

  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.

  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 ‘`libgcc`’ (also known as ‘`gcc`’), ‘`libstdc++`’ (not ‘`libstdc++-v3`’), ‘`libffi`’, ‘`zlib`’, ‘`boehm-gc`’, ‘`ada`’, ‘`libada`’, ‘`libgo`’, ‘`libobjc`’, and ‘`libphobos`’. Note ‘`libiberty`’ does not support shared libraries at all.

  Use `--disable-shared` to build only static libraries. Note that `--disable-shared` does not accept a list of package names as argument, only `--enable-shared` does.

  Contrast with `--enable-host-shared`, which affects host code.

`--enable-host-shared`

  Specify that the host 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.

  This option is required when building the libgccjit.so library.

  Contrast with `--enable-shared`, which affects target libraries.

`--with-gnu-as`

  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 `--with-gnu-as`.) If you have more than one assembler installed on your system, you may want to use this option in connection with `--with-as=pathname` or `--with-build-time-tools=pathname`.

  The following systems are the only ones where it makes a difference whether you use the GNU assembler. On any other system, `--with-gnu-as` has no effect.

  - ‘`hppa1.0-any-any`’
  - ‘`hppa1.1-any-any`’
  - ‘`*-*-solaris2.11`’
`--with-as=pathname`

  Specify that the compiler should use the assembler pointed to by pathname, rather than the one found by the standard rules to find an assembler, which are:

  - Unless GCC is being built with a cross compiler, check the `libexec/gcc/target/version` directory. libexec defaults to `exec-prefix/libexec`; exec-prefix defaults to prefix, which defaults to `/usr/local` unless overridden by the `--prefix=pathname` switch described above. target is the target system triple, such as ‘`sparc-sun-solaris2.11`’, and version denotes the GCC version, such as 3.0.
  - If the target system is the same that you are building on, check operating system specific directories.
  - Check in the `PATH` for a tool whose name is prefixed by the target system triple.
  - Check in the `PATH` 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).

  You may want to use `--with-as` 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.

`--with-gnu-ld`

  Same as `--with-gnu-as` but for the linker.

`--with-ld=pathname`

  Same as `--with-as` but for the linker.

`--with-dsymutil=pathname`

  Same as `--with-as` but for the debug linker (only used on Darwin platforms so far).

`--with-tls=dialect`

  Specify the default TLS dialect, for systems were there is a choice. For ARM targets, possible values for dialect are `gnu` or `gnu2`, which select between the original GNU dialect and the GNU TLS descriptor-based dialect.

`--enable-multiarch`

  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 `--with-sysroot`, and without `--with-native-system-header-dir`. More documentation about multiarch can be found at https://wiki.debian.org/Multiarch.

`--enable-sjlj-exceptions`

  Force use of the `setjmp`/`longjmp`-based scheme for exceptions. ‘`configure`’ ordinarily picks the correct value based on the platform. Only use this option if you are sure you need a different setting.

`--enable-vtable-verify`

  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 `--disable-libvtv` to turn off building libvtv). `--disable-vtable-verify` is the default.

`--disable-gcov`

  Specify that the run-time library used for coverage analysis and associated host tools should not be built.

`--disable-multilib`

  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.

  Some targets provide finer-grained control over which multilibs are built (e.g., `--disable-softfloat`):

  `arm-*-*`

    fpu, 26bit, underscore, interwork, biendian, nofmult.

  `m68*-*-*`

    softfloat, m68881, m68000, m68020.

  `mips*-*-*`

    single-float, biendian, softfloat.

  `msp430-*-*`

    no-exceptions

  `powerpc*-*-*, rs6000*-*-*`

    aix64, pthread, softfloat, powercpu, powerpccpu, powerpcos, biendian, sysv, aix.

`--with-multilib-list=list`
`--without-multilib-list`

  Specify what multilibs to build. list is a comma separated list of values, possibly consisting of a single value. Currently only implemented for aarch64*-*-*, arm*-*-*, loongarch64-*-*, riscv*-*-*, sh*-*-* and x86-64-*-linux*. The accepted values and meaning for each target is given below.

  `aarch64*-*-*`

    list is a comma separated list of `ilp32`, and `lp64` to enable ILP32 and LP64 run-time libraries, respectively. If list is empty, then there will be no multilibs and only the default run-time library will be built. If list is `default` or –with-multilib-list= is not specified, then the default set of libraries is selected based on the value of `--target`.

  `arm*-*-*`

    list is a comma separated list of `aprofile` and `rmprofile` to build multilibs for A or R and M architecture profiles respectively. Note that, due to some limitation of the current multilib framework, using the combined `aprofile,rmprofile` multilibs selects in some cases a less optimal multilib than when using the multilib profile for the architecture targetted. The special value `default` is also accepted and is equivalent to omitting the option, i.e., only the default run-time library will be enabled.

    list may instead contain `@name`, to use the multilib configuration Makefile fragment `name` in `gcc/config/arm` in the source tree (it is part of the corresponding sources, after all). It is recommended, but not required, that files used for this purpose to be named starting with `t-ml-`, to make their intended purpose self-evident, in line with GCC conventions. Such files enable custom, user-chosen multilib lists to be configured. Whether multiple such files can be used together depends on the contents of the supplied files. See `gcc/config/arm/t-multilib` and its supplementary `gcc/config/arm/t-*profile` files for an example of what such Makefile fragments might look like for this version of GCC. The macros expected to be defined in these fragments are not stable across GCC releases, so make sure they define the `MULTILIB`-related macros expected by the version of GCC you are building. See “Target Makefile Fragments” in the internals manual.

    The table below gives the combination of ISAs, architectures, FPUs and floating-point ABIs for which multilibs are built for each predefined profile. The union of these options is considered when specifying both `aprofile` and `rmprofile`.

    Option | aprofile | rmprofile
    ISAs | `-marm` and `-mthumb` | `-mthumb`
    Architectures | default architecture `-march=armv7-a` `-march=armv7ve` `-march=armv8-a` | default architecture `-march=armv6s-m` `-march=armv7-m` `-march=armv7e-m` `-march=armv8-m.base` `-march=armv8-m.main` `-march=armv7`
    FPUs | none `-mfpu=vfpv3-d16` `-mfpu=neon` `-mfpu=vfpv4-d16` `-mfpu=neon-vfpv4` `-mfpu=neon-fp-armv8` | none `-mfpu=vfpv3-d16` `-mfpu=fpv4-sp-d16` `-mfpu=fpv5-sp-d16` `-mfpu=fpv5-d16`
    floating-point ABIs | `-mfloat-abi=soft` `-mfloat-abi=softfp` `-mfloat-abi=hard` | `-mfloat-abi=soft` `-mfloat-abi=softfp` `-mfloat-abi=hard`

  `loongarch*-*-*`

    list is a comma-separated list of the following ABI identifiers: `lp64d[/base]` `lp64f[/base]` `lp64d[/base]`, where the `/base` suffix may be omitted, to enable their respective run-time libraries. If list is empty or `default`, or if `--with-multilib-list` is not specified, then the default ABI as specified by `--with-abi` or implied by `--target` is selected.

  `riscv*-*-*`

    list is a single ABI name. The target architecture must be either `rv32gc` or `rv64gc`. This will build a single multilib for the specified architecture and ABI pair. If `--with-multilib-list` is not given, then a default set of multilibs is selected based on the value of `--target`. This is usually a large set of multilibs.

  `sh*-*-*`

    list is a comma separated list of CPU names. These must be of the form `sh*` or `m*` (in which case they match the compiler option for that processor). The list should not contain any endian options - these are handled by `--with-endian`.

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

    As a special case, if an entry in the list starts with a `!` (exclamation point), then it is added to the list of excluded multilibs. Entries of this sort should be compatible with ‘`MULTILIB_EXCLUDES`’ (once the leading `!` has been stripped).

    If `--with-multilib-list` is not given, then a default set of multilibs is selected based on the value of `--target`. This is usually the complete set of libraries, but some targets imply a more specialized subset.

    Example 1: to configure a compiler for SH4A only, but supporting both endians, with little endian being the default:

        --with-cpu=sh4a --with-endian=little,big --with-multilib-list=

    Example 2: to configure a compiler for both SH4A and SH4AL-DSP, but with only little endian SH4AL:

        --with-cpu=sh4a --with-endian=little,big \
        --with-multilib-list=sh4al,!mb/m4al

  `x86-64-*-linux*`

    list is a comma separated list of `m32`, `m64` and `mx32` to enable 32-bit, 64-bit and x32 run-time libraries, respectively. If list is empty, then there will be no multilibs and only the default run-time library will be enabled.

    If `--with-multilib-list` is not given, then only 32-bit and 64-bit run-time libraries will be enabled.

`--with-multilib-generator=config`

  Specify what multilibs to build. config is a semicolon separated list of values, possibly consisting of a single value. Currently only implemented for riscv*-*-elf*. The accepted values and meanings are given below.

  Every config is constructed with four components: architecture string, ABI, reuse rule with architecture string and reuse rule with sub-extension.

  Example 1: Add multi-lib suppport for rv32i with ilp32.

      rv32i-ilp32--

  Example 2: Add multi-lib suppport for rv32i with ilp32 and rv32imafd with ilp32.

      rv32i-ilp32--;rv32imafd-ilp32--

  Example 3: Add multi-lib suppport for rv32i with ilp32; rv32im with ilp32 and rv32ic with ilp32 will reuse this multi-lib set.

      rv32i-ilp32-rv32im-c

  Example 4: Add multi-lib suppport for rv64ima with lp64; rv64imaf with lp64, rv64imac with lp64 and rv64imafc with lp64 will reuse this multi-lib set.

      rv64ima-lp64--f,c,fc

  `--with-multilib-generator` have an optional configuration argument `--cmodel=val` for code model, this option will expand with other config options, val is a comma separated list of possible code model, currently we support medlow and medany.

  Example 5: Add multi-lib suppport for rv64ima with lp64; rv64ima with lp64 and medlow code model

      rv64ima-lp64--;--cmodel=medlow

  Example 6: Add multi-lib suppport for rv64ima with lp64; rv64ima with lp64 and medlow code model; rv64ima with lp64 and medany code model

      rv64ima-lp64--;--cmodel=medlow,medany

`--with-endian=endians`

  Specify what endians to use. Currently only implemented for sh*-*-*.

  endians may be one of the following:

  `big`

    Use big endian exclusively.

  `little`

    Use little endian exclusively.

  `big,little`

    Use big endian by default. Provide a multilib for little endian.

  `little,big`

    Use little endian by default. Provide a multilib for big endian.

`--enable-threads`

  Specify that the target supports threads. This affects the Objective-C compiler and runtime library, and exception handling for other languages like C++. On some systems, this is the default.

  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, `--enable-threads` is an alias for `--enable-threads=single`.

`--disable-threads`

  Specify that threading support should be disabled for the system. This is an alias for `--enable-threads=single`.

`--enable-threads=lib`

  Specify that lib is the thread support library. This affects the Objective-C compiler and runtime library, and exception handling for other languages like C++. The possibilities for lib are:

  `aix`

    AIX thread support.

  `dce`

    DCE thread support.

  `lynx`

    LynxOS thread support.

  `mipssde`

    MIPS SDE thread support.

  `no`

    This is an alias for ‘`single`’.

  `posix`

    Generic POSIX/Unix98 thread support.

  `rtems`

    RTEMS thread support.

  `single`

    Disable thread support, should work for all platforms.

  `tpf`

    TPF thread support.

  `vxworks`

    VxWorks thread support.

  `win32`

    Microsoft Win32 API thread support.

`--enable-tls`

  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 `--enable-tls` or `--disable-tls`. 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.

`--disable-tls`

  Specify that the target does not support TLS. This is an alias for `--enable-tls=no`.

`--disable-tm-clone-registry`

  Disable TM clone registry in libgcc. It is enabled in libgcc by default. This option helps to reduce code size for embedded targets which do not use transactional memory.

`--with-cpu=cpu`
`--with-cpu-32=cpu`
`--with-cpu-64=cpu`

  Specify which cpu variant the compiler should generate code for by default. cpu will be used as the default value of the `-mcpu=` switch. This option is only supported on some targets, including ARC, ARM, i386, M68k, PowerPC, and SPARC. It is mandatory for ARC. The `--with-cpu-32` and `--with-cpu-64` options specify separate default CPUs for 32-bit and 64-bit modes; these options are only supported for aarch64, i386, x86-64, PowerPC, and SPARC.

`--with-schedule=cpu`
`--with-arch=cpu`
`--with-arch-32=cpu`
`--with-arch-64=cpu`
`--with-tune=cpu`
`--with-tune-32=cpu`
`--with-tune-64=cpu`
`--with-abi=abi`
`--with-fpu=type`
`--with-float=type`

  These configure options provide default values for the `-mschedule=`, `-march=`, `-mtune=`, `-mabi=`, and `-mfpu=` options and for `-mhard-float` or `-msoft-float`. As with `--with-cpu`, which switches will be accepted and acceptable values of the arguments depend on the target.

`--with-mode=mode`

  Specify if the compiler should default to `-marm` or `-mthumb`. This option is only supported on ARM targets.

`--with-stack-offset=num`

  This option sets the default for the -mstack-offset=num option, and will thus generally also control the setting of this option for libraries. This option is only supported on Epiphany targets.

`--with-fpmath=isa`

  This options sets `-mfpmath=sse` by default and specifies the default ISA for floating-point arithmetics. You can select either ‘`sse`’ which enables `-msse2` or ‘`avx`’ which enables `-mavx` by default. This option is only supported on i386 and x86-64 targets.

`--with-fp-32=mode`

  On MIPS targets, set the default value for the `-mfp` option when using the o32 ABI. The possibilities for mode are:

  `32`

    Use the o32 FP32 ABI extension, as with the `-mfp32` command-line option.

  `xx`

    Use the o32 FPXX ABI extension, as with the `-mfpxx` command-line option.

  `64`

    Use the o32 FP64 ABI extension, as with the `-mfp64` command-line option.

  In the absence of this configuration option the default is to use the o32 FP32 ABI extension.

`--with-odd-spreg-32`

  On MIPS targets, set the `-modd-spreg` option by default when using the o32 ABI.

`--without-odd-spreg-32`

  On MIPS targets, set the `-mno-odd-spreg` option by default when using the o32 ABI. This is normally used in conjunction with `--with-fp-32=64` in order to target the o32 FP64A ABI extension.

`--with-nan=encoding`

  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 encoding are:

  `legacy`

    Use the legacy encoding, as with the `-mnan=legacy` command-line option.

  `2008`

    Use the 754-2008 encoding, as with the `-mnan=2008` command-line option.

  To use this configuration option you must have an assembler version installed that supports the `-mnan=` command-line option too. In the absence of this configuration option the default convention is the legacy encoding, as when neither of the `-mnan=2008` and `-mnan=legacy` command-line options has been used.

`--with-divide=type`

  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 type are:

  `traps`

    Division by zero checks use conditional traps (this is the default on systems that support conditional traps).

  `breaks`

    Division by zero checks use the break instruction.

`--with-compact-branches=policy`

  Specify how the compiler should generate branch instructions. This option is only supported on the MIPS target. The possibilities for type are:

  `optimal`

    Cause a delay slot branch to be used if one is available in the current ISA and the delay slot is successfully filled. If the delay slot is not filled, a compact branch will be chosen if one is available.

  `never`

    Ensures that compact branch instructions will never be generated.

  `always`

    Ensures that a compact branch instruction will be generated if available. If a compact branch instruction is not available, a delay slot form of the branch will be used instead. This option is supported from MIPS Release 6 onwards. For pre-R6/microMIPS/MIPS16, this option is just same as never/optimal.

`--with-llsc`

  On MIPS targets, make `-mllsc` the default when no `-mno-llsc` option is passed. This is the default for Linux-based targets, as the kernel will emulate them if the ISA does not provide them.

`--without-llsc`

  On MIPS targets, make `-mno-llsc` the default when no `-mllsc` option is passed.

`--with-synci`

  On MIPS targets, make `-msynci` the default when no `-mno-synci` option is passed.

`--without-synci`

  On MIPS targets, make `-mno-synci` the default when no `-msynci` option is passed. This is the default.

`--with-lxc1-sxc1`

  On MIPS targets, make `-mlxc1-sxc1` the default when no `-mno-lxc1-sxc1` option is passed. This is the default.

`--without-lxc1-sxc1`

  On MIPS targets, make `-mno-lxc1-sxc1` the default when no `-mlxc1-sxc1` option is passed. The indexed load/store instructions are not directly a problem but can lead to unexpected behaviour when deployed in an application intended for a 32-bit address space but run on a 64-bit processor. The issue is seen because all known MIPS 64-bit Linux kernels execute o32 and n32 applications with 64-bit addressing enabled which affects the overflow behaviour of the indexed addressing mode. GCC will assume that ordinary 32-bit arithmetic overflow behaviour is the same whether performed as an `addu` instruction or as part of the address calculation in `lwxc1` type instructions. This assumption holds true in a pure 32-bit environment and can hold true in a 64-bit environment if the address space is accurately set to be 32-bit for o32 and n32.

`--with-madd4`

  On MIPS targets, make `-mmadd4` the default when no `-mno-madd4` option is passed. This is the default.

`--without-madd4`

  On MIPS targets, make `-mno-madd4` the default when no `-mmadd4` option is passed. The `madd4` instruction family can be problematic when targeting a combination of cores that implement these instructions differently. There are two known cores that implement these as fused operations instead of unfused (where unfused is normally expected). Disabling these instructions is the only way to ensure compatible code is generated; this will incur a performance penalty.

`--with-msa`

  On MIPS targets, make `-mmsa` the default when no `-mno-msa` option is passed.

`--without-msa`

  On MIPS targets, make `-mno-msa` the default when no `-mmsa` option is passed. This is the default.

`--with-mips-plt`

  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.

`--with-stack-clash-protection-guard-size=size`

  On certain targets this option sets the default stack clash protection guard size as a power of two in bytes. On AArch64 size is required to be either 12 (4KB) or 16 (64KB).

`--with-isa-spec=ISA-spec-string`

  On RISC-V targets specify the default version of the RISC-V Unprivileged (formerly User-Level) ISA specification to produce code conforming to. The possibilities for ISA-spec-string are:

  `2.2`

    Produce code conforming to version 2.2.

  `20190608`

    Produce code conforming to version 20190608.

  `20191213`

    Produce code conforming to version 20191213.

  In the absence of this configuration option the default version is 20191213.

`--enable-__cxa_atexit`

  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 `-fuse-cxa-atexit` to be passed by default.

`--enable-gnu-indirect-function`

  Define if you want to enable the `ifunc` attribute. This option is currently only available on systems with GNU libc on certain targets.

`--enable-target-optspace`

  Specify that target libraries should be optimized for code space instead of code speed. This is the default for the m32r platform.

`--with-cpp-install-dir=dirname`

  Specify that the user visible `cpp` program should be installed in `prefix/dirname/cpp`, in addition to bindir.

`--enable-comdat`

  Enable COMDAT group support. This is primarily used to override the automatically detected value.

`--enable-initfini-array`

  Force the use of sections `.init_array` and `.fini_array` (instead of `.init` and `.fini`) for constructors and destructors. Option `--disable-initfini-array` has the opposite effect. If neither option is specified, the configure script will try to guess whether the `.init_array` and `.fini_array` sections are supported and, if they are, use them.

`--enable-link-mutex`

  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.

`--enable-link-serialization`

  When building GCC, use make dependencies to serialize linking the compilers for multiple languages, to avoid thrashing on build systems with limited free memory. The default is not to add such dependencies and thus with parallel make potentially link different compilers concurrently. If the argument is a positive integer, allow that number of concurrent link processes for the large binaries.

`--enable-maintainer-mode`

  The build rules that regenerate the Autoconf and Automake output files as well as the GCC master message catalog `gcc.pot` 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 `--enable-maintainer-mode` will enable this. Note that you need a recent version of the `gettext` tools to do so.

`--disable-bootstrap`

  For a native build, the default configuration is to perform a 3-stage bootstrap of the compiler when ‘`make`’ is invoked, testing that GCC can compile itself correctly. If you want to disable this process, you can configure with `--disable-bootstrap`.

`--enable-bootstrap`

  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 `--enable-bootstrap`.

`--enable-generated-files-in-srcdir`

  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 repository 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.

  If you configure with `--enable-generated-files-in-srcdir` 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.

`--enable-version-specific-runtime-libs`

  Specify that runtime libraries should be installed in the compiler specific subdirectory (`libdir/gcc`) rather than the usual places. In addition, ‘`libstdc++`’’s include files will be installed into `libdir` unless you overruled it by using `--with-gxx-include-dir=dirname`. Using this option is particularly useful if you intend to use several versions of GCC in parallel. The default is ‘`yes`’ for ‘`libada`’, and ‘`no`’ for the remaining libraries.

`--with-aix-soname=‘`aix`’, ‘`svr4`’ or ‘`both`’`

  Traditional AIX shared library versioning (versioned `Shared Object` files as members of unversioned `Archive Library` files named ‘`lib.a`’) causes numerous headaches for package managers. However, `Import Files` as members of `Archive Library` files allow for filename-based versioning of shared libraries as seen on Linux/SVR4, where this is called the "SONAME". But as they prevent static linking, `Import Files` may be used with `Runtime Linking` only, where the linker does search for ‘`libNAME.so`’ before ‘`libNAME.a`’ library filenames with the ‘`-lNAME`’ linker flag.

  For detailed information please refer to the AIX ld Command reference.

  As long as shared library creation is enabled, upon:

  `--with-aix-soname=aix`
  `--with-aix-soname=both`

    A (traditional AIX) `Shared Archive Library` file is created:

    - using the ‘`libNAME.a`’ filename scheme
    - with the `Shared Object` file as archive member named ‘`libNAME.so.V`’ (except for ‘`libgcc_s`’, where the `Shared Object` file is named ‘`shr.o`’ for backwards compatibility), which
      - - is used for runtime loading from inside the ‘`libNAME.a`’ file
      - - is used for dynamic loading via `dlopen("libNAME.a(libNAME.so.V)", RTLD_MEMBER)`
      - - is used for shared linking
      - - is used for static linking, so no separate `Static Archive Library` file is needed
  `--with-aix-soname=both`
  `--with-aix-soname=svr4`

    A (second) `Shared Archive Library` file is created:

    - using the ‘`libNAME.so.V`’ filename scheme
    - with the `Shared Object` file as archive member named ‘`shr.o`’, which
      - - is created with the `-G linker flag`
      - - has the `F_LOADONLY` flag set
      - - is used for runtime loading from inside the ‘`libNAME.so.V`’ file
      - - is used for dynamic loading via `dlopen("libNAME.so.V(shr.o)", RTLD_MEMBER)`
    - with the `Import File` as archive member named ‘`shr.imp`’, which
      - - refers to ‘`libNAME.so.V(shr.o)`’ as the "SONAME", to be recorded in the `Loader Section` of subsequent binaries
      - - indicates whether ‘`libNAME.so.V(shr.o)`’ is 32 or 64 bit
      - - lists all the public symbols exported by ‘`lib.so.V(shr.o)`’, eventually decorated with the `‘`weak`’ Keyword`
      - - is necessary for shared linking against ‘`lib.so.V(shr.o)`’

    A symbolic link using the ‘`libNAME.so`’ filename scheme is created:

    - pointing to the ‘`libNAME.so.V`’ `Shared Archive Library` file
    - to permit the `ld Command` to find ‘`lib.so.V(shr.imp)`’ via the ‘`-lNAME`’ argument (requires `Runtime Linking` to be enabled)
    - to permit dynamic loading of ‘`lib.so.V(shr.o)`’ without the need to specify the version number via `dlopen("libNAME.so(shr.o)", RTLD_MEMBER)`

  As long as static library creation is enabled, upon:

  `--with-aix-soname=svr4`

    A `Static Archive Library` is created:

    - using the ‘`libNAME.a`’ filename scheme
    - with all the `Static Object` files as archive members, which
      - - are used for static linking

  While the aix-soname=‘`svr4`’ option does not create `Shared Object` files as members of unversioned `Archive Library` files any more, package managers still are responsible to transfer `Shared Object` files found as member of a previously installed unversioned `Archive Library` file into the newly installed `Archive Library` file with the same filename.

  WARNING: Creating `Shared Object` files with `Runtime Linking` enabled may bloat the TOC, eventually leading to `TOC overflow` errors, requiring the use of either the `-Wl,-bbigtoc` linker flag (seen to break with the `GDB` debugger) or some of the TOC-related compiler flags, see “RS/6000 and PowerPC Options” in the main manual.

  `--with-aix-soname` is currently supported by ‘`libgcc_s`’ only, so this option is still experimental and not for normal use yet.

  Default is the traditional behavior `--with-aix-soname=‘`aix`’`.

`--enable-languages=lang1,lang2,…`

  Specify that only a particular subset of compilers and their runtime libraries should be built. For a list of valid values for langN you can issue the following command in the `gcc` directory of your GCC source tree:

      grep ^language= */config-lang.in

  Currently, you can use any of the following: `all`, `default`, `ada`, `c`, `c++`, `d`, `fortran`, `go`, `jit`, `lto`, `m2`, `objc`, `obj-c++`. Building the Ada compiler has special requirements, see below. If you do not pass this flag, or specify the option `default`, then the default languages available in the `gcc` sub-tree will be configured. Ada, D, Go, Jit, Objective-C++ and Modula-2 are not default languages. LTO is not a default language, but is built by default because `--enable-lto` is enabled by default. The other languages are default languages. If `all` is specified, then all available languages are built. An exception is `jit` language, which requires `--enable-host-shared` to be included with `all`.

`--enable-stage1-languages=lang1,lang2,…`

  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 `--enable-languages`, and the option `all` will select all of the languages enabled by `--enable-languages`. 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 `make stage1-bubble all-target`, or run the testsuite on the stage-1 compiler for the specified languages using `make stage1-start check-gcc`.

`--disable-libada`

  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 ‘`make -C gcc gnatlib_and_tools`’.

`--disable-libgm2`

  Specify that the run-time libraries and tools used by Modula-2 should not be built. This can be useful for debugging.

`--disable-libsanitizer`

  Specify that the run-time libraries for the various sanitizers should not be built.

`--disable-libssp`

  Specify that the run-time libraries for stack smashing protection should not be built or linked against. On many targets library support is provided by the C library instead.

`--disable-libquadmath`

  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 `--disable-libquadmath-support` is used.

`--disable-libquadmath-support`

  Specify that the Fortran front end and `libgfortran` do not add support for `libquadmath` on systems supporting it.

`--disable-libgomp`

  Specify that the GNU Offloading and Multi Processing Runtime Library should not be built.

`--disable-libvtv`

  Specify that the run-time libraries used by vtable verification should not be built.

`--with-dwarf2`

  Specify that the compiler should use DWARF debugging information as the default; the exact DWARF version that is the default is target-specific.

`--with-advance-toolchain=at`

  On 64-bit PowerPC Linux systems, configure the compiler to use the header files, library files, and the dynamic linker from the Advance Toolchain release at instead of the default versions that are provided by the Linux distribution. In general, this option is intended for the developers of GCC, and it is not intended for general use.

`--enable-targets=all`
`--enable-targets=target_list`

  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.

`--enable-default-pie`

  Turn on `-fPIE` and `-pie` by default.

`--enable-secureplt`

  This option enables `-msecure-plt` by default for powerpc-linux. See “RS/6000 and PowerPC Options” in the main manual

`--enable-default-ssp`

  Turn on `-fstack-protector-strong` by default.

`--enable-cld`

  This option enables `-mcld` by default for 32-bit x86 targets. See “i386 and x86-64 Options” in the main manual

`--enable-large-address-aware`

  The `--enable-large-address-aware` option arranges for MinGW executables to be linked using the `--large-address-aware` option, that enables the use of more than 2GB of memory. If GCC is configured with this option, its effects can be reversed by passing the `-Wl,--disable-large-address-aware` option to the so-configured compiler driver.

`--enable-win32-registry`
`--enable-win32-registry=key`
`--disable-win32-registry`

  The `--enable-win32-registry` option enables Microsoft Windows-hosted GCC to look up installations paths in the registry using the following key:

      HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\key

  key defaults to GCC version number, and can be overridden by the `--enable-win32-registry=key` 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 `--disable-win32-registry` option. This option has no effect on the other hosts.

`--nfp`

  Specify that the machine does not have a floating point unit. This option only applies to ‘`m68k-sun-sunosn`’. On any other system, `--nfp` has no effect.

`--enable-werror`
`--disable-werror`
`--enable-werror=yes`
`--enable-werror=no`

  When you specify this option, it controls whether certain files in the compiler are built with `-Werror` in bootstrap stage2 and later. If you don’t specify it, `-Werror` is turned on for the main development trunk. However it defaults to off for release branches and final releases. The specific files which get `-Werror` are controlled by the Makefiles.

`--enable-checking`
`--disable-checking`
`--enable-checking=list`

  This option controls performing internal consistency checks in the compiler. It does not change the generated code, but adds error checking of the requested complexity. This slows down the compiler and may only work properly if you are building the compiler with GCC.

  When the option is not specified, the active set of checks depends on context. Namely, bootstrap stage 1 defaults to ‘`--enable-checking=yes`’, builds from release branches or release archives default to ‘`--enable-checking=release`’, and otherwise ‘`--enable-checking=yes,extra`’ is used. When the option is specified without a list, the result is the same as ‘`--enable-checking=yes`’. Likewise, ‘`--disable-checking`’ is equivalent to ‘`--enable-checking=no`’.

  The categories of checks available in list are ‘`yes`’ (most common checks ‘`assert,misc,gc,gimple,rtlflag,runtime,tree,types`’), ‘`no`’ (no checks at all), ‘`all`’ (all but ‘`valgrind`’), ‘`release`’ (cheapest checks ‘`assert,runtime`’) or ‘`none`’ (same as ‘`no`’). ‘`release`’ checks are always on and to disable them ‘`--disable-checking`’ or ‘`--enable-checking=no[,<other checks>]`’ must be explicitly requested. Disabling assertions makes the compiler and runtime slightly faster but increases the risk of undetected internal errors causing wrong code to be generated.

  Individual checks can be enabled with these flags: ‘`assert`’, ‘`df`’, ‘`extra`’, ‘`fold`’, ‘`gc`’, ‘`gcac`’, ‘`gimple`’, ‘`misc`’, ‘`rtl`’, ‘`rtlflag`’, ‘`runtime`’, ‘`tree`’, ‘`types`’ and ‘`valgrind`’. ‘`extra`’ extends ‘`misc`’ checking with extra checks that might affect code generation and should therefore not differ between stage1 and later stages in bootstrap.

  The ‘`valgrind`’ check requires the external `valgrind` simulator, available from https://valgrind.org. The ‘`rtl`’ checks are expensive and the ‘`df`’, ‘`gcac`’ and ‘`valgrind`’ checks are very expensive.

`--disable-stage1-checking`
`--enable-stage1-checking`
`--enable-stage1-checking=list`

  This option affects only bootstrap build. If no `--enable-checking` option is specified the stage1 compiler is built with ‘`yes`’ checking enabled, otherwise the stage1 checking flags are the same as specified by `--enable-checking`. To build the stage1 compiler with different checking options use `--enable-stage1-checking`. The list of checking options is the same as for `--enable-checking`. If your system is too slow or too small to bootstrap a released compiler with checking for stage1 enabled, you can use ‘`--disable-stage1-checking`’ to disable checking for the stage1 compiler.

`--enable-coverage`
`--enable-coverage=level`

  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 level argument controls whether the compiler is built optimized or not, values are ‘`opt`’ and ‘`noopt`’. 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.

`--enable-gather-detailed-mem-stats`

  When this option is specified more detailed information on memory allocation is gathered. This information is printed when using `-fmem-report`.

`--enable-valgrind-annotations`

  Mark selected memory related operations in the compiler when run under valgrind to suppress false positives.

`--enable-nls`
`--disable-nls`

  The `--enable-nls` 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 `--disable-nls` option disables NLS.

`--with-included-gettext`

  If NLS is enabled, the `--with-included-gettext` option causes the build procedure to prefer its copy of GNU `gettext`.

`--with-catgets`

  If NLS is enabled, and if the host lacks `gettext` but has the inferior `catgets` interface, the GCC build procedure normally ignores `catgets` and instead uses GCC’s copy of the GNU `gettext` library. The `--with-catgets` option causes the build procedure to use the host’s `catgets` in this situation.

`--with-libiconv-prefix=dir`

  Search for libiconv header files in `dir/include` and libiconv library files in `dir/lib`.

`--enable-obsolete`

  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.

  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.

`--enable-decimal-float`
`--enable-decimal-float=yes`
`--enable-decimal-float=no`
`--enable-decimal-float=bid`
`--enable-decimal-float=dpd`
`--disable-decimal-float`

  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 AArch64, 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 ‘`bid`’ or ‘`dpd`’). The ‘`bid`’ (binary integer decimal) format is default on AArch64, i386 and x86_64 systems, and the ‘`dpd`’ (densely packed decimal) format is default on PowerPC systems.

`--enable-fixed-point`
`--disable-fixed-point`

  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.

`--with-long-double-128`

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

`--with-long-double-format=ibm`
`--with-long-double-format=ieee`

  Specify whether `long double` uses the IBM extended double format or the IEEE 128-bit floating point format on PowerPC Linux systems. This configuration switch will only work on little endian PowerPC Linux systems and on big endian 64-bit systems where the default cpu is at least power7 (i.e. `--with-cpu=power7`, `--with-cpu=power8`, or `--with-cpu=power9` is used).

  If you use the `--with-long-double-64` configuration option, the `--with-long-double-format=ibm` and `--with-long-double-format=ieee` options are ignored.

  The default `long double` format is to use IBM extended double. Until all of the libraries are converted to use IEEE 128-bit floating point, it is not recommended to use `--with-long-double-format=ieee`.

`--enable-fdpic`

  On SH Linux systems, generate ELF FDPIC code.

`--with-gmp=pathname`
`--with-gmp-include=pathname`
`--with-gmp-lib=pathname`
`--with-mpfr=pathname`
`--with-mpfr-include=pathname`
`--with-mpfr-lib=pathname`
`--with-mpc=pathname`
`--with-mpc-include=pathname`
`--with-mpc-lib=pathname`

  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 (‘`--with-gmp=gmpinstalldir`’, ‘`--with-mpfr=mpfrinstalldir`’, ‘`--with-mpc=mpcinstalldir`’). The `--with-gmp=gmpinstalldir` option is shorthand for `--with-gmp-lib=gmpinstalldir/lib` and `--with-gmp-include=gmpinstalldir/include`. Likewise the `--with-mpfr=mpfrinstalldir` option is shorthand for `--with-mpfr-lib=mpfrinstalldir/lib` and `--with-mpfr-include=mpfrinstalldir/include`, also the `--with-mpc=mpcinstalldir` option is shorthand for `--with-mpc-lib=mpcinstalldir/lib` and `--with-mpc-include=mpcinstalldir/include`. 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 (`LD_LIBRARY_PATH` on GNU/Linux and Solaris systems).

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

`--with-isl=pathname`
`--with-isl-include=pathname`
`--with-isl-lib=pathname`

  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 (‘`--with-isl=islinstalldir`’). The `--with-isl=islinstalldir` option is shorthand for `--with-isl-lib=islinstalldir/lib` and `--with-isl-include=islinstalldir/include`. If this shorthand assumption is not correct, you can use the explicit include and lib options directly.

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

`--with-stage1-ldflags=flags`

  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 `--disable-bootstrap`. If `--with-stage1-libs` is not set to a value, then the default is ‘`-static-libstdc++ -static-libgcc`’, if supported.

`--with-stage1-libs=libs`

  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 `--disable-bootstrap`.

`--with-boot-ldflags=flags`

  This option may be used to set linker flags to be used when linking stage 2 and later when bootstrapping GCC. If –with-boot-libs is not is set to a value, then the default is ‘`-static-libstdc++ -static-libgcc`’.

`--with-boot-libs=libs`

  This option may be used to set libraries to be used when linking stage 2 and later when bootstrapping GCC.

`--with-debug-prefix-map=map`

  Convert source directory names using `-fdebug-prefix-map` when building runtime libraries. ‘`map`’ is a space-separated list of maps of the form ‘`old=new`’.

`--enable-linker-build-id`

  Tells GCC to pass `--build-id` option to the linker for all final links (links performed without the `-r` or `--relocatable` option), if the linker supports it. If you specify `--enable-linker-build-id`, but your linker does not support `--build-id` option, a warning is issued and the `--enable-linker-build-id` option is ignored. The default is off.

`--with-linker-hash-style=choice`

  Tells GCC to pass `--hash-style=choice` option to the linker for all final links. choice can be one of ‘`sysv`’, ‘`gnu`’, and ‘`both`’ where ‘`sysv`’ is the default.

`--enable-gnu-unique-object`
`--disable-gnu-unique-object`

  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.

`--with-diagnostics-color=choice`

  Tells GCC to use choice as the default for `-fdiagnostics-color=` option (if not used explicitly on the command line). choice can be one of ‘`never`’, ‘`auto`’, ‘`always`’, and ‘`auto-if-env`’ where ‘`auto`’ is the default. ‘`auto-if-env`’ makes `-fdiagnostics-color=auto` the default if `GCC_COLORS` is present and non-empty in the environment of the compiler, and `-fdiagnostics-color=never` otherwise.

`--with-diagnostics-urls=choice`

  Tells GCC to use choice as the default for `-fdiagnostics-urls=` option (if not used explicitly on the command line). choice can be one of ‘`never`’, ‘`auto`’, ‘`always`’, and ‘`auto-if-env`’ where ‘`auto`’ is the default. ‘`auto-if-env`’ makes `-fdiagnostics-urls=auto` the default if `GCC_URLS` or `TERM_URLS` is present and non-empty in the environment of the compiler, and `-fdiagnostics-urls=never` otherwise.

`--enable-lto`
`--disable-lto`

  Enable support for link-time optimization (LTO). This is enabled by default, and may be disabled using `--disable-lto`.

`--enable-linker-plugin-configure-flags=FLAGS`
`--enable-linker-plugin-flags=FLAGS`

  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 (‘`x86_64-pc-linux-gnu`’) host system, but have a 32-bit x86 GNU/Linux (‘`i686-pc-linux-gnu`’) linker executable (which is executable on the former system), you can configure GCC as follows for getting compatible linker plugins:

      % srcdir/configure \
          --host=x86_64-pc-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'

`--with-plugin-ld=pathname`

  Enable an alternate linker to be used at link-time optimization (LTO) link time when `-fuse-linker-plugin` 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 `-fuse-linker-plugin` for details.

`--enable-canonical-system-headers`
`--disable-canonical-system-headers`

  Enable system header path canonicalization for `libcpp`. 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 `--disable-canonical-system-headers`.

`--with-glibc-version=major.minor`

  Tell GCC that when the GNU C Library (glibc) is used on the target it will be version major.minor 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.

  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.

`--enable-as-accelerator-for=target`

  Build as offload target compiler. Specify offload host triple by target.

`--enable-offload-targets=target1[=path1],…,targetN[=pathN]`

  Enable offloading to targets target1, …, targetN. Offload compilers are expected to be already installed. Default search path for them is `exec-prefix`, but it can be changed by specifying paths path1, …, pathN.

      % srcdir/configure \
          --enable-offload-targets=amdgcn-amdhsa,nvptx-none

`--enable-offload-defaulted`

  Tell GCC that configured but not installed offload compilers and libgomp plugins are silently ignored. Useful for distribution compilers where those are in separate optional packages and where the presence or absence of those optional packages should determine the actual supported offloading target set rather than the GCC configure-time selection.

`--enable-cet`
`--disable-cet`

  Enable building target run-time libraries with control-flow instrumentation, see `-fcf-protection` option. When `--enable-cet` is specified target libraries are configured to add `-fcf-protection` and, if needed, other target specific options to a set of building options.

  `--enable-cet=auto` is default. CET is enabled on Linux/x86 if target binutils supports `Intel CET` instructions and disabled otherwise. In this case, the target libraries are configured to get additional `-fcf-protection` option.

`--with-riscv-attribute=‘`yes`’, ‘`no`’ or ‘`default`’`

  Generate RISC-V attribute by default, in order to record extra build information in object.

  The option is disabled by default. It is enabled on RISC-V/ELF (bare-metal) target if target binutils supported.

`--enable-s390-excess-float-precision`
`--disable-s390-excess-float-precision`

  On s390(x) targets, enable treatment of float expressions with double precision when in standards-compliant mode (e.g., when `--std=c99` or `-fexcess-precision=standard` are given).

  For a native build and cross compiles that have target headers, the option’s default is derived from glibc’s behavior. When glibc clamps float_t to double, GCC follows and enables the option. For other cross compiles, the default is disabled.

`--with-zstd=pathname`
`--with-zstd-include=pathname`
`--with-zstd-lib=pathname`

  If you do not have the `zstd` library installed in a standard location and you want to build GCC, you can explicitly specify the directory where it is installed (‘`--with-zstd=zstdinstalldir`’). The `--with-zstd=zstdinstalldir` option is shorthand for `--with-zstd-lib=zstdinstalldir/lib` and `--with-zstd-include=zstdinstalldir/include`. If this shorthand assumption is not correct, you can use the explicit include and lib options directly.

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

#### Cross-Compiler-Specific Options

The following options only apply to building cross compilers.

`--with-toolexeclibdir=dir`

  Specify the installation directory for libraries built with a cross compiler. The default is `${gcc_tooldir}/lib`.

`--with-sysroot`
`--with-sysroot=dir`

  Tells GCC to consider dir 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 `--sysroot=dir` was added to the default options of the built compiler. The specified directory is not copied into the install tree, unlike the options `--with-headers` and `--with-libs` that this option obsoletes. The default value, in case `--with-sysroot` is not given an argument, is `${gcc_tooldir}/sys-root`. If the specified directory is a subdirectory of `${exec_prefix}`, then it will be found relative to the GCC binaries if the installation tree is moved.

  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 `make install`; it does not affect the compiler which is used to build GCC itself.

  If you specify the `--with-native-system-header-dir=dirname` option then the compiler will search that directory within dirname for native system headers rather than the default `/usr/include`.

`--with-build-sysroot`
`--with-build-sysroot=dir`

  Tells GCC to consider dir as the system root (see `--with-sysroot`) while building target libraries, instead of the directory specified with `--with-sysroot`. This option is only useful when you are already using `--with-sysroot`. You can use `--with-build-sysroot` when you are configuring with `--prefix` set to a directory that is different from the one in which you are installing GCC and your target libraries.

  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.

  If you specify the `--with-native-system-header-dir=dirname` option then the compiler will search that directory within dirname for native system headers rather than the default `/usr/include`.

`--with-headers`
`--with-headers=dir`

  Deprecated in favor of `--with-sysroot`. Specifies that target headers are available when building a cross compiler. The dir argument specifies a directory which has the target include files. These include files will be copied into the `gcc` install directory. This option with the dir argument is required when building a cross compiler, if `prefix/target/sys-include` doesn’t pre-exist. If `prefix/target/sys-include` does pre-exist, the dir argument may be omitted. `fixincludes` will be run on these files to make them compatible with GCC.

`--without-headers`

  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.

`--with-libs`
`--with-libs="dir1 dir2 … dirN"`

  Deprecated in favor of `--with-sysroot`. Specifies a list of directories which contain the target runtime libraries. These libraries will be copied into the `gcc` install directory. If the directory list is omitted, this option has no effect.

`--with-newlib`

  Specifies that ‘`newlib`’ is being used as the target C library. This causes `__eprintf` to be omitted from `libgcc.a` on the assumption that it will be provided by ‘`newlib`’.

`--with-avrlibc`

  Only supported for the AVR target. Specifies that ‘`AVR-Libc`’ is being used as the target C library. This causes float support functions like `__addsf3` to be omitted from `libgcc.a` on the assumption that it will be provided by `libm.a`. For more technical details, cf. PR54461. 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.

`--with-double={32|64|32,64|64,32}`
`--with-long-double={32|64|32,64|64,32|double}`

  Only supported for the AVR target since version 10. Specify the default layout available for the C/C++ ‘`double`’ and ‘`long double`’ type, respectively. The following rules apply:

  - The first value after the ‘`=`’ specifies the default layout (in bits) of the type and also the default for the `-mdouble=` resp. `-mlong-double=` compiler option.
  - If more than one value is specified, respective multilib variants are available, and `-mdouble=` resp. `-mlong-double=` acts as a multilib option.
  - If `--with-long-double=double` is specified, ‘`double`’ and ‘`long double`’ will have the same layout.
  - The defaults are `--with-long-double=64,32` and `--with-double=32,64`. The default ‘`double`’ layout imposed by the latter is compatible with older versions of the compiler that implement ‘`double`’ as a 32-bit type, which does not comply to the language standard.

  Not all combinations of `--with-double=` and `--with-long-double=` are valid. For example, the combination `--with-double=32,64` `--with-long-double=32` will be rejected because the first option specifies the availability of multilibs for ‘`double`’, whereas the second option implies that ‘`long double`’ — and hence also ‘`double`’ — is always 32 bits wide.

`--with-double-comparison={tristate|bool|libf7}`

  Only supported for the AVR target since version 10. Specify what result format is returned by library functions that compare 64-bit floating point values (`DFmode`). The GCC default is ‘`tristate`’. If the floating point implementation returns a boolean instead, set it to ‘`bool`’.

`--with-libf7={libgcc|math|math-symbols|no}`

  Only supported for the AVR target since version 10. Specify to which degree code from LibF7 is included in libgcc. LibF7 is an ad-hoc, AVR-specific, 64-bit floating point emulation written in C and (inline) assembly. ‘`libgcc`’ adds support for functions that one would usually expect in libgcc like double addition, double comparisons and double conversions. ‘`math`’ also adds routines that one would expect in `libm.a`, but with `__` (two underscores) prepended to the symbol names as specified by `math.h`. ‘`math-symbols`’ also defines weak aliases for the functions declared in `math.h`. However, `--with-libf7` won’t install no `math.h` header file whatsoever, this file must come from elsewhere. This option sets `--with-double-comparison` to ‘`bool`’.

`--with-nds32-lib=library`

  Specifies that library setting is used for building `libgcc.a`. Currently, the valid library is ‘`newlib`’ or ‘`mculib`’. This option is only supported for the NDS32 target.

`--with-build-time-tools=dir`

  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.

  For example, on an ‘`ia64-hp-hpux`’ system, you may have the GNU assembler and linker in `/usr/bin`, and the native tools in a different path, and build a toolchain that expects to find the native tools in `/usr/bin`.

  When you use this option, you should ensure that dir includes `ar`, `as`, `ld`, `nm`, `ranlib` and `strip` if necessary, and possibly `objdump`. Otherwise, GCC may use an inconsistent set of tools.

#### Overriding `configure` test results

Sometimes, it might be necessary to override the result of some `configure` test, for example in order to ease porting to a new system or work around a bug in a test. The toplevel `configure` script provides three variables for this:

`build_configargs`

  The contents of this variable is passed to all build `configure` scripts.

`host_configargs`

  The contents of this variable is passed to all host `configure` scripts.

`target_configargs`

  The contents of this variable is passed to all target `configure` scripts.

In order to avoid shell and `make` quoting issues for complex overrides, you can pass a setting for `CONFIG_SITE` and set variables in the site file.

#### Objective-C-Specific Options

The following options apply to the build of the Objective-C runtime library.

`--enable-objc-gc`

  Specify that an additional variant of the GNU Objective-C runtime library is built, using an external build of the Boehm-Demers-Weiser garbage collector (https://www.hboehm.info/gc/). This library needs to be available for each multilib variant, unless configured with `--enable-objc-gc=‘`auto`’` in which case the build of the additional runtime library is skipped when not available and the build continues.

`--with-target-bdw-gc=list`
`--with-target-bdw-gc-include=list`
`--with-target-bdw-gc-lib=list`

  Specify search directories for the garbage collector header files and libraries. list is a comma separated list of key value pairs of the form ‘`multilibdir=path`’, where the default multilib key is named as ‘`.`’ (dot), or is omitted (e.g. ‘`--with-target-bdw-gc=/opt/bdw-gc,32=/opt-bdw-gc32`’).

  The options `--with-target-bdw-gc-include` and `--with-target-bdw-gc-lib` must always be specified together for each multilib variant and they take precedence over `--with-target-bdw-gc`. If `--with-target-bdw-gc-include` is missing values for a multilib, then the value for the default multilib is used (e.g. ‘`--with-target-bdw-gc-include=/opt/bdw-gc/include`’ ‘`--with-target-bdw-gc-lib=/opt/bdw-gc/lib64,32=/opt-bdw-gc/lib32`’). If none of these options are specified, the library is assumed in default locations.

#### D-Specific Options

The following options apply to the build of the D runtime library.

`--enable-libphobos-checking`
`--disable-libphobos-checking`
`--enable-libphobos-checking=list`

  This option controls whether run-time checks and contracts are compiled into the D runtime library. When the option is not specified, the library is built with ‘`release`’ checking. When the option is specified without a list, the result is the same as ‘`--enable-libphobos-checking=yes`’. Likewise, ‘`--disable-libphobos-checking`’ is equivalent to ‘`--enable-libphobos-checking=no`’.

  The categories of checks available in list are ‘`yes`’ (compiles libphobos with `-fno-release`), ‘`no`’ (compiles libphobos with `-frelease`), ‘`all`’ (same as ‘`yes`’), ‘`none`’ or ‘`release`’ (same as ‘`no`’).

  Individual checks available in list are ‘`assert`’ (compiles libphobos with an extra option `-fassert`).

`--with-libphobos-druntime-only`
`--with-libphobos-druntime-only=choice`

  Specify whether to build only the core D runtime library (druntime), or both the core and standard library (phobos) into libphobos. This is useful for targets that have full support in druntime, but no or incomplete support in phobos. choice can be one of ‘`auto`’, ‘`yes`’, and ‘`no`’ where ‘`auto`’ is the default.

  When the option is not specified, the default choice ‘`auto`’ means that it is inferred whether the target has support for the phobos standard library. When the option is specified without a choice, the result is the same as ‘`--with-libphobos-druntime-only=yes`’.

`--with-target-system-zlib`

  Use installed ‘`zlib`’ rather than that included with GCC. This needs to be available for each multilib variant, unless configured with `--with-target-system-zlib=‘`auto`’` in which case the GCC included ‘`zlib`’ is only used when the system installed library is not available.

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