Installing GCC

Installing GCC

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 via SVN, 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.

Target specification

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’, and ‘libobjc’. 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 ’
  • ‘sparc-sun-solaris2.any ’
  • ‘sparc64-any-solaris2.any ’
--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-solaris2.7’, 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 (e.g. /usr/ccs/bin on Sun Solaris 2).
  • 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-stabs

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.

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.

Normally, GCC uses the ECOFF debugging format by default; if you prefer BSD stabs, specify --with-stabs when you configure GCC.

No matter which default you choose when you configure GCC, the user can use the -gcoff and -gstabs+ options to specify explicitly the debug format for a particular compilation.

--with-stabs is meaningful on the ISC system on the 386, also, if --with-gas 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.

--with-stabs 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.

--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-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.

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 arm*-*-*, sh*-*-* and x86-64-*-linux*. The accepted values and meaning for each target is given below.

arm*-*-*

list is one ofdefault, aprofile or rmprofile. Specifying default is equivalent to omitting this option, ie. only the default runtime library will be enabled. Specifying aprofile or rmprofile builds multilibs for a combination of ISA, architecture, FPU available and floating-point ABI.

The table below gives the combination of ISAs, architectures, FPUs and floating-point ABIs for which multilibs are built for each accepted value.

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
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-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=generic.

--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.

generic

A platform with either unknown or changeable thread support. GCC will provide a layer that permits the runtime system to provide an implementation of the thread model.

--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.

--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 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-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-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.

--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-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 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.

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. This is currently supported by ‘libgfortran’, ‘libstdc++’, and ‘libobjc’.

--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, ada, c, c++, fortran, go, jit, lto, objc, obj-c++. Building the Ada compiler has special requirements, see below. If you do not pass this flag, or specify the option all, then all default languages available in the gcc sub-tree will be configured. Ada, Go, Jit, and Objective-C++ 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.

--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-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.

--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 2 debugging information as the default.

--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-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
--enable-checking=list

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 ‘yes,extra’ by default when building from SVN or snapshots, but ‘release’ for releases. The default for building the stage1 compiler is ‘yes’. More control over the checks may be had by specifying list. The categories of checks available are ‘yes’ (most common checks ‘assert,misc,tree,gc,rtlflag,runtime’), ‘no’ (no checks at all), ‘all’ (all but ‘valgrind’), ‘release’ (cheapest checks ‘assert,runtime’) or ‘none’ (same as ‘no’). Individual checks can be enabled with these flags ‘assert’, ‘df’, ‘fold’, ‘gc’, ‘gcac’, ‘misc’, ‘rtl’, ‘rtlflag’, ‘runtime’, ‘tree’, ‘extra’ and ‘valgrind’. ‘extra’ adds for ‘misc’ checking extra checks that might affect code generation and should therefore not differ between stage1 and later stages.

The ‘valgrind’ check requires the external valgrind simulator, available from http://valgrind.org/. The ‘df’, ‘rtl’, ‘gcac’ and ‘valgrind’ checks are very expensive. To disable all checking, ‘--disable-checking’ or ‘--enable-checking=none’ 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.

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

If no --enable-checking option is specified the stage1 compiler will be 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 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 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.

--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’ means that -fdiagnostics-color=auto will be the default if GCC_COLORS is present and non-empty in the environment, and -fdiagnostics-color=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-unknown-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-unknown-linux-gnu \
    --enable-linker-plugin-configure-flags=--host=i686-pc-linux-gnu \
    --enable-linker-plugin-flags='CC=gcc\ -m32\ -Wl,-rpath,[...]/i686-pc-linux-gnu/lib'
--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-target=i686-unknown-linux-gnu=/path/to/i686/compiler,x86_64-pc-linux-gnu

If ‘hsa’ is specified as one of the targets, the compiler will be built with support for HSA GPU accelerators. Because the same compiler will emit the accelerator code, no path should be specified.

--with-hsa-runtime=pathname
--with-hsa-runtime-include=pathname
--with-hsa-runtime-lib=pathname

If you configure GCC with HSA offloading but do not have the HSA run-time library installed in a standard location then you can explicitly specify the directory where they are installed. The --with-hsa-runtime=hsainstalldir option is a shorthand for --with-hsa-runtime-lib=hsainstalldir/lib and --with-hsa-runtime-include=hsainstalldir/include.

Cross-Compiler-Specific Options

The following options only apply to building cross compilers.

--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

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. 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.

--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 (http://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.

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