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AC_DEFUN([AX_ISC_CPP20], [
AC_MSG_CHECKING(c++20 support)
# Save flags.
CPPFLAGS_SAVED="${CPPFLAGS}"
LIBS_SAVED="${LIBS}"
# Provide -std=c++20 flag temporarily.
CPPFLAGS="${CPPFLAGS} -std=c++20"
# Simulate the definition of std::derived_from.
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[#include <concepts>
template<class Derived, class Base>
concept derived_from =
std::is_base_of_v<Base, Derived> &&
std::is_convertible_v<const volatile Derived*, const volatile Base*>;
struct BaseClass {};
struct DerivedClass : BaseClass {};
],
[static_assert(std::derived_from<BaseClass, DerivedClass> == false);
static_assert(std::derived_from<DerivedClass, BaseClass> == true);]
)],
[AC_MSG_RESULT([yes])
CPP20_SUPPORTED=true],
[AC_MSG_RESULT([no])
CPP20_SUPPORTED=false])
# Restore flags.
CPPFLAGS="${CPPFLAGS_SAVED}"
])
|
