dl-fldigi/m4/c++11.m4

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m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [[
template <typename T>
struct check
{
static_assert(sizeof(int) <= sizeof(T), "not big enough");
};
struct Base {
virtual void f() {}
};
struct Child : public Base {
virtual void f() {}
};
typedef check<check<bool>> right_angle_brackets;
int a;
decltype(a) b;
typedef check<int> check_type;
check_type c;
check_type&& cr = static_cast<check_type&&>(c);
auto d = a;
auto l = [](){};
]])
AC_DEFUN([AX_CXX_COMPILE_STDCXX_11], [dnl
m4_if([$1], [], [],
[$1], [ext], [],
[$1], [noext], [],
[m4_fatal([invalid argument `$1' to AX_CXX_COMPILE_STDCXX_11])])dnl
m4_if([$2], [], [ax_cxx_compile_cxx11_required=true],
[$2], [mandatory], [ax_cxx_compile_cxx11_required=true],
[$2], [optional], [ax_cxx_compile_cxx11_required=false],
[m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX_11])])
AC_LANG_PUSH([C++])dnl
ac_success=no
AC_CACHE_CHECK(whether $CXX supports C++11 features by default,
ax_cv_cxx_compile_cxx11,
[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[ax_cv_cxx_compile_cxx11=yes],
[ax_cv_cxx_compile_cxx11=no])])
if test x$ax_cv_cxx_compile_cxx11 = xyes; then
ac_success=yes
fi
m4_if([$1], [noext], [], [dnl
if test x$ac_success = xno; then
for switch in -std=gnu++11 -std=gnu++0x; do
cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
$cachevar,
[ac_save_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $switch"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[eval $cachevar=yes],
[eval $cachevar=no])
CXXFLAGS="$ac_save_CXXFLAGS"])
if eval test x\$$cachevar = xyes; then
CXXFLAGS="$CXXFLAGS $switch"
CXX11_SWITCH="$switch"
AC_SUBST(CXX11_SWITCH)
ac_success=yes
break
fi
done
fi])
m4_if([$1], [ext], [], [dnl
if test x$ac_success = xno; then
for switch in -std=c++11 -std=c++0x; do
cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx11_$switch])
AC_CACHE_CHECK(whether $CXX supports C++11 features with $switch,
$cachevar,
[ac_save_CXXFLAGS="$CXXFLAGS"
CXXFLAGS="$CXXFLAGS $switch"
AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
[eval $cachevar=yes],
[eval $cachevar=no])
CXXFLAGS="$ac_save_CXXFLAGS"])
if eval test x\$$cachevar = xyes; then
CXXFLAGS="$CXXFLAGS $switch"
CXX11_SWITCH="$switch"
AC_SUBST(CXX11_SWITCH)
ac_success=yes
break
fi
done
fi])
AC_LANG_POP([C++])
if test x$ax_cxx_compile_cxx11_required = xtrue; then
if test x$ac_success = xno; then
AC_MSG_ERROR([*** A compiler with support for C++11 language features is required.])
fi
else
if test x$ac_success = xno; then
HAVE_CXX11=0
AC_MSG_NOTICE([No compiler with C++11 support was found])
else
HAVE_CXX11=1
AC_DEFINE(HAVE_CXX11,1,
[define if the compiler supports basic C++11 syntax])
fi
AC_SUBST(HAVE_CXX11)
fi
])