All the usual autoconf configure options are available, run ‘./configure --help’ for a summary. The file INSTALL.autoconf has some generic installation information too.
It might be possible to build without the help of ‘configure’, certainly
all the code is there, but unfortunately you'll be on your own.
cd /my/build/dir
/my/sources/gmp-6.0.0/configure
Not all ‘make’ programs have the necessary features (VPATH) to
support this. In particular, SunOS and Slowaris make have bugs that
make them unable to build in a separate directory. Use GNU make
instead.
--exec-prefix can be used to direct architecture-dependent files like
libgmp.a to a different location. This can be used to share
architecture-independent parts like the documentation, but separate the
dependent parts. Note however that gmp.h and mp.h are
architecture-dependent since they encode certain aspects of libgmp, so
it will be necessary to ensure both $prefix/include and
$exec_prefix/include are available to the compiler.
./configure --build=ultrasparc-sun-solaris2.7
In all cases the ‘OS’ part is important, since it controls how libtool
generates shared libraries. Running ‘./config.guess’ is the simplest way
to see what it should be, if you don't know already.
./configure --build=athlon-pc-freebsd3.5 --host=m68k-mac-linux-gnu
Compiler tools are sought first with the host system type as a prefix. For example m68k-mac-linux-gnu-ranlib is tried, then plain ranlib. This makes it possible for a set of cross-compiling tools to co-exist with native tools. The prefix is the argument to ‘--host’, and this can be an alias, such as ‘m68k-linux’. But note that tools don't have to be setup this way, it's enough to just have a PATH with a suitable cross-compiling cc etc.
Compiling for a different CPU in the same family as the build system is a form of cross-compilation, though very possibly this would merely be special options on a native compiler. In any case ‘./configure’ avoids depending on being able to run code on the build system, which is important when creating binaries for a newer CPU since they very possibly won't run on the build system.
In all cases the compiler must be able to produce an executable (of whatever
format) from a standard C main. Although only object files will go to
make up libgmp, ‘./configure’ uses linking tests for various
purposes, such as determining what functions are available on the host system.
Currently a warning is given unless an explicit ‘--build’ is used when cross-compiling, because it may not be possible to correctly guess the build system type if the PATH has only a cross-compiling cc.
Note that the ‘--target’ option is not appropriate for GMP. It's for use
when building compiler tools, with ‘--host’ being where they will run,
and ‘--target’ what they'll produce code for. Ordinary programs or
libraries like GMP are only interested in the ‘--host’ part, being where
they'll run. (Some past versions of GMP used ‘--target’ incorrectly.)
The following CPUs have specific support. See configure.ac for details of what code and compiler options they select.
CPUs not listed will use generic C code.
Note that this will run quite slowly, but it should be portable and should at
least make it possible to get something running if all else fails.
./configure --host=mips64-sgi-irix6 ABI=n32
See ABI and ISA, for the available choices on relevant CPUs, and what
applications need to do.
For various systems, default compiler flags are set based on the CPU and compiler. The usual ‘CFLAGS="-whatever"’ can be passed to ‘./configure’ to use something different or to set good flags for systems GMP doesn't otherwise know.
The ‘CC’ and ‘CFLAGS’ used are printed during ‘./configure’, and can be found in each generated Makefile. This is the easiest way to check the defaults when considering changing or adding something.
Note that when ‘CC’ and ‘CFLAGS’ are specified on a system supporting multiple ABIs it's important to give an explicit ‘ABI=whatever’, since GMP can't determine the ABI just from the flags and won't be able to select the correct assembly code.
If just ‘CC’ is selected then normal default ‘CFLAGS’ for that
compiler will be used (if GMP recognises it). For example ‘CC=gcc’ can
be used to force the use of GCC, with default flags (and default ABI).
No flags are used with ‘CC_FOR_BUILD’ because a simple invocation like
‘cc foo.c’ should be enough. If some particular options are required
they can be included as for instance ‘CC_FOR_BUILD="cc -whatever"’.
A separate libgmpxx.la has been adopted rather than having C++ objects within libgmp.la in order to ensure dynamic linked C programs aren't bloated by a dependency on the C++ standard library, and to avoid any chance that the C++ compiler could be required when linking plain C programs.
libgmpxx.la will use certain internals from libgmp.la and can only be expected to work with libgmp.la from the same GMP version. Future changes to the relevant internals will be accompanied by renaming, so a mismatch will cause unresolved symbols rather than perhaps mysterious misbehaviour.
In general libgmpxx.la will be usable only with the C++ compiler that
built it, since name mangling and runtime support are usually incompatible
between different compilers.
It's important that the C and C++ compilers match, meaning their startup and runtime support routines are compatible and that they generate code in the same ABI (if there's a choice of ABIs on the system). ‘./configure’ isn't currently able to check these things very well itself, so for that reason ‘--disable-cxx’ is the default, to avoid a build failure due to a compiler mismatch. Perhaps this will change in the future.
Incidentally, it's normally not good enough to set ‘CXX’ to the same as
‘CC’. Although gcc for instance recognises foo.cc as
C++ code, only g++ will invoke the linker the right way when
building an executable or shared library from C++ object files.
For convenience, the following choices are also available. ‘--disable-alloca’ is the same as ‘no’.
alloca if available, otherwise
‘malloc-reentrant’. This is the default.
alloca if available, otherwise
‘malloc-notreentrant’.
alloca is reentrant and fast, and is recommended. It actually allocates
just small blocks on the stack; larger ones use malloc-reentrant.
‘malloc-reentrant’ is, as the name suggests, reentrant and thread safe, but ‘malloc-notreentrant’ is faster and should be used if reentrancy is not required.
The two malloc methods in fact use the memory allocation functions selected by
mp_set_memory_functions, these being malloc and friends by
default. See Custom Allocation.
An additional choice ‘--enable-alloca=debug’ is available, to help when
debugging memory related problems (see Debugging).
MPN_PATH="sparc32/v8 sparc32 generic"
which means look first for v8 code, then plain sparc32 (which is v7), and
finally fall back on generic C. Knowledgeable users with special requirements
can specify a different path. Normally this is completely unnecessary.
Info format ‘doc/gmp.info’ is included in the distribution. The usual automake targets are available to make PostScript, DVI, PDF and HTML (these will require various TeX and Texinfo tools).
DocBook and XML can be generated by the Texinfo makeinfo program too, see Options for makeinfo.
Some supplementary notes can also be found in the doc subdirectory.