[libc++] Enable availability based on the compiler instead of __has_extension (#84065)

__has_extension(...) doesn't work as intended when -pedantic-errors is
used with Clang. With that flag, __has_extension(...) is equivalent to
__has_feature(...), which means that checks like

    __has_extension(pragma_clang_attribute_external_declaration)

will return 0. In turn, this has the effect of disabling availability
markup in libc++, which is undesirable.

rdar://124078119
(cherry picked from commit 292a28df6c55679fad0589dea35278a8c66b2ae1)
This commit is contained in:
Louis Dionne 2024-03-07 15:12:21 -05:00 committed by Tom Stellard
parent 55193c2ba5
commit c14bf0a13d
2 changed files with 25 additions and 4 deletions

View File

@ -72,11 +72,10 @@
# endif
#endif
// Availability markup is disabled when building the library, or when the compiler
// Availability markup is disabled when building the library, or when a non-Clang
// compiler is used because only Clang supports the necessary attributes.
// doesn't support the proper attributes.
#if defined(_LIBCPP_BUILDING_LIBRARY) || defined(_LIBCXXABI_BUILDING_LIBRARY) || \
!__has_feature(attribute_availability_with_strict) || !__has_feature(attribute_availability_in_templates) || \
!__has_extension(pragma_clang_attribute_external_declaration)
#if defined(_LIBCPP_BUILDING_LIBRARY) || defined(_LIBCXXABI_BUILDING_LIBRARY) || !defined(_LIBCPP_COMPILER_CLANG_BASED)
# if !defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
# define _LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS
# endif

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@ -0,0 +1,22 @@
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// REQUIRES: stdlib=apple-libc++
// Test that using -pedantic-errors doesn't turn off availability annotations.
// This used to be the case because we used __has_extension(...) to enable the
// availability annotations, and -pedantic-errors changes the behavior of
// __has_extension(...) in an incompatible way.
// ADDITIONAL_COMPILE_FLAGS: -pedantic-errors
#include <__availability>
#if defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
# error Availability annotations should be enabled on Apple platforms in the system configuration!
#endif