# define _LIBCPP_NO_CFI
#endif
+// If the compiler supports using_if_exists, pretend we have those functions and they'll
+// be picked up if the C library provides them.
+//
+// TODO: Once we drop support for Clang 12, we can assume the compiler supports using_if_exists
+// for platforms that don't have a conforming C11 library, so we can drop this whole thing.
+#if __has_attribute(using_if_exists)
+# define _LIBCPP_HAS_TIMESPEC_GET
+# define _LIBCPP_HAS_QUICK_EXIT
+# define _LIBCPP_HAS_ALIGNED_ALLOC
+#else
#if (defined(__ISO_C_VISIBLE) && (__ISO_C_VISIBLE >= 2011)) || __cplusplus >= 201103L
# if defined(__FreeBSD__)
# define _LIBCPP_HAS_ALIGNED_ALLOC
# endif
# endif // __APPLE__
#endif
+#endif // __has_attribute(using_if_exists)
#ifndef _LIBCPP_CXX03_LANG
# define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp)
// we're detecting this here instead of in <__config> because we can't include
// system headers from <__config>, since it leads to circular module dependencies.
// This is also meant to be a very temporary workaround until the SDKs are fixed.
-#if defined(__APPLE__)
+#if defined(__APPLE__) && !__has_attribute(using_if_exists)
# include <sys/cdefs.h>
# if defined(_LIBCPP_HAS_TIMESPEC_GET) && (__DARWIN_C_LEVEL < __DARWIN_C_FULL)
# define _LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED