mkvtoolnix/ac/c++-features.m4
Moritz Bunkus 540ba7f122
configure: remove tests for C++11 & C++14 features & corresponding -std= flags
The compilers that I support that implement the required C++17
functionality also implement the full C++11 and C++14 specifications.
2020-05-13 16:37:44 +02:00

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AC_DEFUN([AX_CXX_STD_CXX_FLAG],[
AC_CACHE_CHECK([for support for the "-std=c++17" flag], [ax_cv_std_cxx_flag],[
AC_LANG_PUSH(C++)
CXXFLAGS_SAVED="$CXXFLAGS"
for flag in c++17; do
CXXFLAGS="$CXXFLAGS_SAVED -std=$flag"
AC_TRY_COMPILE([], [true;], [ax_cv_std_cxx_flag="-std=$flag"], [ax_cv_std_cxx_flag="undecided"])
if test x"$ax_cv_std_cxx_flag" != xundecided ; then
break
fi
done
if test x"$ax_cv_std_cxx_flag" = xundecided ; then
ax_cv_std_cxx_flag="no"
fi
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
STD_CXX=""
if test x"$ax_cv_std_cxx_flag" != xno ; then
STD_CXX=$ax_cv_std_cxx_flag
fi
AC_SUBST(STD_CXX)
])
AC_DEFUN([AX_CXX17_ATTRIBUTE_MAYBE_UNUSED],[
AC_CACHE_CHECK([for support for C++17 feature "attribute 'maybe_unused'"], [ax_cv_cxx17_attribute_maybe_unused],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[
int testme([[maybe_unused]] int the_var) {
return 42;
}
],
[return testme(54);],
[ax_cv_cxx17_attribute_maybe_unused="yes"],
[ax_cv_cxx17_attribute_maybe_unused="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_attribute_maybe_unused" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * attribute 'maybe_unused' (C++17)"
fi
])
AC_DEFUN([AX_CXX17_STRUCTURED_BINDINGS],[
AC_CACHE_CHECK([for support for C++17 feature "structured bindings"], [ax_cv_cxx17_structured_bindings],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[
#include <utility>
std::pair<int, char> testme() {
return std::make_pair(42, '!');
}
],
[
auto const &[the_int, the_char] = testme();
return the_int;
],
[ax_cv_cxx17_structured_bindings="yes"],
[ax_cv_cxx17_structured_bindings="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_structured_bindings" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * structured bindings (C++17)"
fi
])
AC_DEFUN([AX_CXX17_NESTED_NAMESPACE_DEFINITION],[
AC_CACHE_CHECK([for support for C++17 feature "nested namespace definition"], [ax_cv_cxx17_nested_namespace_definition],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[namespace A::B::C { int d; }],
[A::B::C::d = 1; return A::B::C::d;],
[ax_cv_cxx17_nested_namespace_definition="yes"],
[ax_cv_cxx17_nested_namespace_definition="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_nested_namespace_definition" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * nested namespace definition (C++17)"
fi
])
AC_DEFUN([AX_CXX17_STD_OPTIONAL],[
AC_CACHE_CHECK([for support for C++17 feature "std::optional"], [ax_cv_cxx17_std_optional],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[#include <optional>],
[
std::optional<int> moo;
moo = 42;
return moo ? moo.value() : moo.value_or(54);
],
[ax_cv_cxx17_std_optional="yes"],
[ax_cv_cxx17_std_optional="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_std_optional" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * std::optional (C++17)"
fi
])
AC_DEFUN([AX_CXX17_STD_GCD],[
AC_CACHE_CHECK([for support for C++17 feature "std::gcd"], [ax_cv_cxx17_std_gcd],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[#include <numeric>],
[return std::gcd(42, 54);],
[ax_cv_cxx17_std_gcd="yes"],
[ax_cv_cxx17_std_gcd="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_std_gcd" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * std::gcd (C++17)"
fi
])
AC_DEFUN([AX_CXX17_CONSTEXPR_IF],[
AC_CACHE_CHECK([for support for C++17 feature "constexpr if"], [ax_cv_cxx17_constexpr_if],[
CXXFLAGS_SAVED=$CXXFLAGS
CXXFLAGS="$CXXFLAGS $STD_CXX"
export CXXFLAGS
AC_LANG_PUSH(C++)
AC_TRY_COMPILE(
[],
[if constexpr (true) return 42; else return 54;],
[ax_cv_cxx17_constexpr_if="yes"],
[ax_cv_cxx17_constexpr_if="no"])
AC_LANG_POP
CXXFLAGS="$CXXFLAGS_SAVED"
])
if ! test x"$ax_cv_cxx17_constexpr_if" = xyes ; then
missing_cxx_features="$missing_cxx_features\n * constexpr if (C++17)"
fi
])
dnl AC_DEFUN([AX_CXX17_DEF_NAME],[
dnl AC_CACHE_CHECK([for support for C++17 feature "human"], [ax_cv_cxx17_def_name],[
dnl
dnl CXXFLAGS_SAVED=$CXXFLAGS
dnl CXXFLAGS="$CXXFLAGS $STD_CXX"
dnl export CXXFLAGS
dnl
dnl AC_LANG_PUSH(C++)
dnl AC_TRY_COMPILE(
dnl [],
dnl [],
dnl [ax_cv_cxx17_def_name="yes"],
dnl [ax_cv_cxx17_def_name="no"])
dnl AC_LANG_POP
dnl
dnl CXXFLAGS="$CXXFLAGS_SAVED"
dnl ])
dnl
dnl if ! test x"$ax_cv_cxx17_def_name" = xyes ; then
dnl missing_cxx_features="$missing_cxx_features\n * human (C++17)"
dnl fi
dnl ])
AX_CXX_STD_CXX_FLAG
AX_CXX17_ATTRIBUTE_MAYBE_UNUSED
AX_CXX17_NESTED_NAMESPACE_DEFINITION
AX_CXX17_STRUCTURED_BINDINGS
AX_CXX17_STD_OPTIONAL
AX_CXX17_STD_GCD
AX_CXX17_CONSTEXPR_IF
if test x"$missing_cxx_features" != x ; then
printf "The following features of the C++17 standards are not supported by $CXX:$missing_cxx_features\n"
printf "If you are using the GNU C compiler collection (gcc), you need\n"
printf "at least v7; for clang v4 and newer should work.\n"
AC_MSG_ERROR([support for required C++17 features incomplete])
fi