From ebc01bbc7a6758743e6383af34619ef1423afa15 Mon Sep 17 00:00:00 2001 From: Louis Dionne Date: Tue, 17 Aug 2021 11:23:48 -0400 Subject: [PATCH] [libc++] Skip logic for detecting C11 features when using_if_exists is supported In the future, we'll want to rely exclusively on using_if_exists for this job, but for now, only rely on it when the compiler supports that attribute. That removes the possibility for getting the logic wrong. Differential Revision: https://reviews.llvm.org/D108297 --- libcxx/include/__config | 11 +++++++++++ libcxx/include/ctime | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/libcxx/include/__config b/libcxx/include/__config index 0f2a231..740106c 100644 --- a/libcxx/include/__config +++ b/libcxx/include/__config @@ -354,6 +354,16 @@ # 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 @@ -408,6 +418,7 @@ # endif # endif // __APPLE__ #endif +#endif // __has_attribute(using_if_exists) #ifndef _LIBCPP_CXX03_LANG # define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp) diff --git a/libcxx/include/ctime b/libcxx/include/ctime index 8b2efd7..2a3fdd1 100644 --- a/libcxx/include/ctime +++ b/libcxx/include/ctime @@ -59,7 +59,7 @@ int timespec_get( struct timespec *ts, int base); // C++17 // 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 # if defined(_LIBCPP_HAS_TIMESPEC_GET) && (__DARWIN_C_LEVEL < __DARWIN_C_FULL) # define _LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED -- 2.7.4