cxx_have_friend_in_template_declaration.m4

FreeFEM is an implementation of the GFEM language dedicated to the finite element method. It provid

dnl ----------------------------------------------------------------------
dnl
dnl CXX_HAVE_FRIEND_IN_TEMPLATE_DECLARATION
dnl ---------------------------------------------
dnl
dnl If the C++ compiler support explicit template instantiation, 
dnl                         define `HAVE_FRIEND_IN_TEMPLATE_DECLARATION'.
dnl
dnl This program is free software; you can redistribute it and/or modify
dnl  it under the terms of the GNU General Public License as published by
dnl  the Free Software Foundation; either version 2 of the License, or
dnl  (at your option) any later version.
dnl  
dnl  This program is distributed in the hope that it will be useful,
dnl  but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
dnl  GNU General Public License 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., 675 Mass Ave, Cambridge, MA 02139, USA.

AC_DEFUN(CXX_HAVE_FRIEND_IN_TEMPLATE_DECLARATION,
[
AC_REQUIRE([AC_PROG_CXX])
AC_MSG_CHECKING(whether the C++ compiler (${CXX}) supports friend<> in template)
AC_CACHE_VAL(ddec_cv_have_friend_in_template_declaration,
[
AC_LANG_SAVE
AC_LANG_CPLUSPLUS
AC_TRY_COMPILE([
template<class T> class A { public: A();};
template<class T> operator==(A<T> const& a, A<T> const& b);
template<class T> class B { public: B();
    friend int operator== <>(A<T> const& a, A<T> const& b);
};
template B<int>;
],[return 0;],
ddec_cv_have_friend_in_template_declaration=yes,
ddec_cv_have_friend_in_template_declaration=no)
AC_LANG_RESTORE
])
AC_MSG_RESULT($ddec_cv_have_friend_in_template_declaration)
if test "$ddec_cv_have_friend_in_template_declaration" = yes; then
AC_DEFINE(HAVE_FRIEND_IN_TEMPLATE_DECLARATION)
fi
])dnl