When configuring libstdc++, you'll have to configure the entire
gccsrcdir directory. Consider using the
toplevel gcc configuration option
--enable-languages=c++
, which saves time by only
building the C++ toolchain.
Here are all of the configure options specific to libstdc++. Keep in mind that they all have opposite forms as well (enable/disable and with/without). The defaults are for the current development sources, which may be different than those for released versions.
The canonical way to find out the configure options that are available for a given set of libstdc++ sources is to go to the source directory and then type: ./configure --help.
--enable-multilib
[default]This is part of the generic multilib support for building cross compilers. As such, targets like "powerpc-elf" will have libstdc++ built many different ways: "-msoft-float" and not, etc. A different libstdc++ will be built for each of the different multilib versions. This option is on by default.
--enable-version-specific-runtime-libs
Specify that run-time libraries should be installed in the
compiler-specific subdirectory (i.e.,
${libdir}/gcc-lib/${target_alias}/${gcc_version}
)
instead of ${libdir}
. This option is useful if you
intend to use several versions of gcc in parallel. In addition,
libstdc++'s include files will be installed in
${libdir}/gcc-lib/${target_alias}/${gcc_version}/include/g++
,
unless you also specify
--with-gxx-include-dir=
dirname
during configuration.
--with-gxx-include-dir=<include-files dir>
Adds support for named libstdc++ include directory. For instance, the following puts all the libstdc++ headers into a directory called "4.4-20090404" instead of the usual "c++/(version)".
--with-gxx-include-dir=/foo/H-x86-gcc-3-c-gxx-inc/include/4.4-20090404
--enable-cstdio
This is an abbreviated form of '--enable-cstdio=stdio'
(described next).
--enable-cstdio=OPTION
Select a target-specific I/O package. At the moment, the only choice is to use 'stdio', a generic "C" abstraction. The default is 'stdio'. This option can change the library ABI.
--enable-clocale
This is an abbreviated form of '--enable-clocale=generic'
(described next).
--enable-clocale=OPTION
Select a target-specific underlying locale package. The choices are 'ieee_1003.1-2001' to specify an X/Open, Standard Unix (IEEE Std. 1003.1-2001) model based on langinfo/iconv/catgets, 'gnu' to specify a model based on functionality from the GNU C library (langinfo/iconv/gettext) (from glibc, the GNU C library), 'generic' to use a generic "C" abstraction which consists of "C" locale info, 'newlib' to specify the Newlib C library model which only differs from the 'generic' model in the handling of ctype, or 'darwin' which omits the wchar_t specializations needed by the 'generic' model.
If not explicitly specified, the configure process tries
to guess the most suitable package from the choices above. The
default is 'generic'. On glibc-based systems of sufficient
vintage (2.3 and newer), 'gnu' is automatically selected. On newlib-based
systems ('--with_newlib=yes'
) and OpenBSD, 'newlib' is
automatically selected. On Mac OS X 'darwin' is automatically selected.
This option can change the library ABI.
--enable-libstdcxx-allocator
This is an abbreviated form of
'--enable-libstdcxx-allocator=auto'
(described
next).
--enable-libstdcxx-allocator=OPTION
Select a target-specific underlying std::allocator. The choices are 'new' to specify a wrapper for new, 'malloc' to specify a wrapper for malloc, 'mt' for a fixed power of two allocator, 'pool' for the SGI pooled allocator or 'bitmap' for a bitmap allocator. See this page for more information on allocator extensions. This option can change the library ABI.
--enable-cheaders=OPTION
This allows the user to define the approach taken for C header compatibility with C++. Options are c, c_std, and c_global. These correspond to the source directory's include/c, include/c_std, and include/c_global, and may also include include/c_compatibility. The default is 'c_global'.
--enable-threads
This is an abbreviated form of '--enable-threads=yes'
(described next).
--enable-threads=OPTION
Select a threading library. A full description is given in the general compiler configuration instructions. This option can change the library ABI.
--enable-libstdcxx-threads
Enable C++11 threads support. If not explicitly specified, the configure process enables it if possible. This option can change the library ABI.
--enable-libstdcxx-time
This is an abbreviated form of
'--enable-libstdcxx-time=yes'
(described next).
--enable-libstdcxx-time=OPTION
Enables link-type checks for the availability of the clock_gettime clocks, used in the implementation of [time.clock], and of the nanosleep and sched_yield functions, used in the implementation of [thread.thread.this] of the 2011 ISO C++ standard. The choice OPTION=yes checks for the availability of the facilities in libc and libposix4. In case it's needed the latter is also linked to libstdc++ as part of the build process. OPTION=rt also searches (and, if needed, links) librt. Note that the latter is not always desirable because, in glibc, for example, in turn it triggers the linking of libpthread too, which activates locking, a large overhead for single-thread programs. OPTION=no skips the tests completely. The default is OPTION=auto, which skips the checks and enables the features only for targets known to support them.
--enable-libstdcxx-debug
Build separate debug libraries in addition to what is normally built.
By default, the debug libraries are compiled with
CXXFLAGS='-g3 -O0 -fno-inline'
, are installed in ${libdir}/debug
, and have the
same names and versioning information as the non-debug
libraries. This option is off by default.
Note this make command, executed in
the build directory, will do much the same thing, without the
configuration difference and without building everything twice:
make CXXFLAGS='-g3 -O0 -fno-inline' all
--enable-libstdcxx-debug-flags=FLAGS
This option is only valid when --enable-debug
is also specified, and applies to the debug builds only. With
this option, you can pass a specific string of flags to the
compiler to use when building the debug versions of libstdc++.
FLAGS is a quoted string of options, like
--enable-libstdcxx-debug-flags='-g3 -O1 -fno-inline'
--enable-cxx-flags=FLAGS
With this option, you can pass a string of -f (functionality) flags to the compiler to use when building libstdc++. This option can change the library ABI. FLAGS is a quoted string of options, like
--enable-cxx-flags='-fvtable-gc -fomit-frame-pointer -ansi'
Note that the flags don't necessarily have to all be -f flags, as shown, but usually those are the ones that will make sense for experimentation and configure-time overriding.
The advantage of --enable-cxx-flags over setting CXXFLAGS in the 'make' environment is that, if files are automatically rebuilt, the same flags will be used when compiling those files as well, so that everything matches.
Fun flags to try might include combinations of
-fstrict-aliasing -fno-exceptions -ffunction-sections -fvtable-gc
and opposite forms (-fno-) of the same. Tell us (the libstdc++ mailing list) if you discover more!
--enable-c99
The long long type was introduced in C99, along
with many other functions for wide characters, and math
classification macros, etc. If enabled, all C99 functions not
specified by the C++ standard will be put into namespace
__gnu_cxx
, and then all these names will
be injected into namespace std, so that C99 functions can be
used "as if" they were in the C++ standard (as they
will eventually be in some future revision of the standard,
without a doubt). By default, C99 support is on, assuming the
configure probes find all the necessary functions and bits
necessary. This option can change the library ABI.
--enable-wchar_t
[default]Template specializations for the wchar_t type are required for wide character conversion support. Disabling wide character specializations may be expedient for initial porting efforts, but builds only a subset of what is required by ISO, and is not recommended. By default, this option is on. This option can change the library ABI.
--enable-long-long
The long long type was introduced in C99. It is provided as a GNU extension to C++98 in g++. This flag builds support for "long long" into the library (specialized templates and the like for iostreams). This option is on by default: if enabled, users will have to either use the new-style "C" headers by default (i.e., <cmath> not <math.h>) or add appropriate compile-time flags to all compile lines to allow "C" visibility of this feature (on GNU/Linux, the flag is -D_ISOC99_SOURCE, which is added automatically via CPLUSPLUS_CPP_SPEC's addition of _GNU_SOURCE). This option can change the library ABI.
--enable-fully-dynamic-string
This option enables a special version of basic_string avoiding the optimization that allocates empty objects in static memory. Mostly useful together with shared memory allocators, see PR libstdc++/16612 for details.
--enable-concept-checks
This turns on additional compile-time checks for instantiated library templates, in the form of specialized templates described in the Concept Checking section. They can help users discover when they break the rules of the STL, before their programs run. These checks are based on C++03 rules and some of them are not compatible with correct C++11 code.
--enable-symvers[=style]
In 3.1 and later, tries to turn on symbol versioning in the shared library (if a shared library has been requested). Values for 'style' that are currently supported are 'gnu', 'gnu-versioned-namespace', 'darwin', 'darwin-export', and 'sun'. Both gnu- options require that a recent version of the GNU linker be in use. Both darwin options are equivalent. With no style given, the configure script will try to guess correct defaults for the host system, probe to see if additional requirements are necessary and present for activation, and if so, will turn symbol versioning on. This option can change the library ABI.
--enable-libstdcxx-visibility
In 4.2 and later, enables or disables visibility
attributes. If enabled (as by default), and the compiler seems
capable of passing the simple sanity checks thrown at it, adjusts
items in namespace std, namespace std::tr1, namespace std::tr2,
and namespace __gnu_cxx to have visibility ("default")
so that -fvisibility options can be used without affecting the
normal external-visibility of namespace std entities.
Prior to 4.7 this option was spelled --enable-visibility
.
--enable-libstdcxx-pch
In 3.4 and later, tries to turn on the generation of
stdc++.h.gch, a pre-compiled file including all the standard
C++ includes. If enabled (as by default), and the compiler
seems capable of passing the simple sanity checks thrown at
it, try to build stdc++.h.gch as part of the make process.
In addition, this generated file is used later on (by appending
--include bits/stdc++.h
to CXXFLAGS) when running the
testsuite.
--enable-extern-template
[default]Use extern template to pre-instantiate all required
specializations for certain types defined in the standard libraries.
These types include string
and dependents like
char_traits
, the templatized IO classes,
allocator
, and others.
Disabling means that implicit
template generation will be used when compiling these types. By
default, this option is on. This option can change the library ABI.
--disable-hosted-libstdcxx
By default, a complete hosted C++ library is built. The C++ Standard also describes a freestanding environment, in which only a minimal set of headers are provided. This option builds such an environment.
--disable-libstdcxx-verbose
By default, the library is configured to write descriptive messages to standard error for certain events such as calling a pure virtual function or the invocation of the standard terminate handler. Those messages cause the library to depend on the demangler and standard I/O facilities, which might be undesirable in a low-memory environment or when standard error is not available. This option disables those messages. This option does not change the library ABI.
--disable-libstdcxx-dual-abi
Disable support for the new, C++11-conforming implementations of
std::string
, std::list
etc. so that the
library only provides definitions of types using the old ABI
(see Dual ABI).
This option changes the library ABI.
--with-default-libstdcxx-abi=
OPTION
Set the default value for the _GLIBCXX_USE_CXX11_ABI
macro (see Macros).
The default is OPTION=new
which sets the macro to
1
,
use OPTION=gcc4-compatible
to set it to
0
.
This option does not change the library ABI.
--with-libstdcxx-lock-policy=OPTION
Sets the lock policy that controls how
shared_ptr
reference counting is
synchronized.
The choice OPTION=atomic enables use of atomics for updates to
shared_ptr
reference counts.
The choice OPTION=mutex enables use of a mutex to synchronize updates
to shared_ptr
reference counts.
If the compiler's thread model is "single" then this option has no
effect, as no synchronization is used for the reference counts.
The default is OPTION=auto, which checks for the availability of
compiler built-ins for 2-byte and 4-byte atomic compare-and-swap,
and uses OPTION=atomic if they're available, OPTION=mutex otherwise.
This option can change the library ABI.
If the library is configured to use atomics and user programs are
compiled using a target that doesn't natively support the atomic
operations (e.g. the library is configured for armv7 and then code
is compiled with -march=armv5t
) then the program
might rely on support in libgcc to provide the atomics.
--enable-vtable-verify
[default]Use -fvtable-verify=std
to compile the C++
runtime with instrumentation for vtable verification. All virtual
functions in the standard library will be verified at runtime.
Types impacted include locale
and
iostream
, and others. Disabling means that
the C++ runtime is compiled without support for vtable
verification. By default, this option is off.
--enable-libstdcxx-filesystem-ts
[default]Build libstdc++fs.a
as well
as the usual libstdc++ and libsupc++ libraries. This is enabled by
default on select POSIX targets where it is known to work and disabled
otherwise.