Dear Roberto,

I must say I was aware of the problem but could not find a portable solution (I know too little about shared libraries and libtool and so on and never find the time to fill this gap).

AC_LIB_LINKFLAGS is meant to be this portable solution.

I agree the problem is very annoying: for example, if you happen to have one libgmp installed into a standard location, but you want to experiment with another version of libgmp, our --with-gmp-* options are of little help.

Would you be so kind to tell us more about the solution you suggest? Is adding AC_LIB_LINKFLAGS(gmpxx, gmp) to configure.ac really all what needs to be done? Shouldn't ac_check_gmp.m4 also be modified so that the directory specified with the option --with-gmp-dir can be taken into account?

When you do AC_LIB_LINKFLAGS(gmpxx, gmp), the configure script will automatically accept an option --with-libgmpxx-dir=<someDirectory> though which the user can specify where he instealled libgmpxx. In your current scheme, the equivalent options would be

--with-libgmpxx-includes=<someDirectory>/include \ --with-libgmpxx-lib=<someDirectory>/lib

The AC_LIB_LINKFLAGS macro also looks in $prefix, i.e. if the user has specified --prefix=<someDirectory> and does not specify --with-libgmpxx-dir, then the macros will look in $prefix/include and $prefix/lib. (Because it's quite common that prerequisites have already been installed with the same --prefix.)

In ac_check_gmp.m4 you also check whether the library is really present. I'd order the checks as follows:

1) [Optional] Call AC_LIB_LINKFLAGS(gmp). 2) Call AC_LIB_LINKFLAGS(gmpxx, gmp). This sets the variable LIBGMPXX and augments CPPFLAGS. If the library isn't found, LIBGMPXX will just be "-lgmpxx -lgmp". 3) Now temporarily augment LIBS ac_save_LIBS=$LIBS compile and run the test program LIBS=$ac_save_LIBS

And in the Makefiles, you add @LTLIBGMPXX@ to the link command line. That's it.

ac_check_gmp.m4 will then look similar the one below (untested).

I also guess the position into configure.ac must be chosen carefully.

Yes. Since the macro changes CPPFLAGS, it should come right after the detection of the C/C++ compiler, before other checks for include files and libraries.

And you will need a copy of config.rpath in your package. That's needed since runpath handling is so platform dependent.

Best, Bruno

========================================================================= dnl A function to check for the existence and usability of GMP. dnl Copyright (C) 2001-2003 Roberto Bagnara bagnara@cs.unipr.it dnl dnl This file is part of the Parma Polyhedra Library (PPL). dnl dnl The PPL is free software; you can redistribute it and/or modify it dnl under the terms of the GNU General Public License as published by the dnl Free Software Foundation; either version 2 of the License, or (at your dnl option) any later version. dnl dnl The PPL is distributed in the hope that it will be useful, but WITHOUT dnl ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or dnl FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License dnl for more details. dnl dnl You should have received a copy of the GNU General Public License dnl along with this program; if not, write to the Free Software dnl Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, dnl USA. dnl dnl For the most up-to-date information see the Parma Polyhedra Library dnl site: http://www.cs.unipr.it/ppl/ . dnl AC_DEFUN([AC_CHECK_GMP], [ dnl Check how to link with libgmp. AC_LIB_LINKFLAGS([gmp])

dnl Check how to link with libgmpxx. AC_LIB_LINKFLAGS([gmpxx], [gmp])

ac_save_LIBS="$LIBS" LIBS="$LIBS $LIBGMPXX" AC_LANG_PUSH(C++)

AC_MSG_CHECKING([for the GMP library]) AC_RUN_IFELSE([AC_LANG_SOURCE([[ #include <gmpxx.h>

using namespace std;

int main() { mpz_class pie("3141592653589793238462643383279502884"); exit(0); } ]])], AC_MSG_RESULT(yes) ac_cv_have_gmp=yes, AC_MSG_RESULT(no) ac_cv_have_gmp=no, AC_MSG_RESULT(no) ac_cv_have_gmp=no)

have_gmp=${ac_cv_have_gmp}

if test x"$ac_cv_have_gmp" = xyes then

AC_MSG_CHECKING([size of GMP mp_limb_t]) ac_cv_sizeof_mp_limb_t=none for size in 2 4 8 do AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ #include <gmp.h>

int main() { switch (0) { case 0: case (sizeof(mp_limb_t) == $size): ; } return 0; } ]])], ac_cv_sizeof_mp_limb_t=$size; break) done AC_MSG_RESULT($size) AC_DEFINE_UNQUOTED(SIZEOF_MP_LIMB_T, $size, [Size of GMP's mp_limb_t.])

AC_MSG_CHECKING([whether GMP has been compiled with support for exceptions]) AC_RUN_IFELSE([AC_LANG_SOURCE([[ #include <gmpxx.h> #include <new> #include <cstddef> #include <cstdlib>

using namespace std;

static void* x_malloc(size_t) { throw bad_alloc(); }

static void* x_realloc(void*, size_t, size_t) { throw bad_alloc(); }

static void x_free(void*, size_t) { }

int main() { mp_set_memory_functions(x_malloc, x_realloc, x_free); try { mpz_class pie("3141592653589793238462643383279502884"); } catch (bad_alloc) { exit(0); } exit(1); } ]])], AC_MSG_RESULT(yes) ac_cv_gmp_supports_exceptions=yes, AC_MSG_RESULT(no) ac_cv_gmp_supports_exceptions=no, AC_MSG_RESULT(no) ac_cv_gmp_supports_exceptions=no)

gmp_supports_exceptions=${ac_cv_gmp_supports_exceptions} if test x"$gmp_supports_exceptions" = xyes then value=1 else value=0 fi AC_DEFINE_UNQUOTED(GMP_SUPPORTS_EXCEPTIONS, $value, [Not zero if GMP has been compiled with support for exceptions.])

fi

AC_LANG_POP(C++) LIBS="$ac_save_LIBS"

dnl We use libtool, therefore we take $LTLIBGMPXX, not $LIBGMPXX. gmp_library_option="$LTLIBGMPXX" ])