[libc++] Rely solely on using_if_exists for ::aligned_alloc, ::quick_exit and ::timespec_get

[ldionne]

Summary

Instead of carrying around #ifdefs to determine whether those functions
are available on the platform, use the using_if_exists attribute (with
Clang) to import it into namespace std only when available. That was the
purpose of this attribute from the start.

This change means that trying to use libc++ with an old SDK (or on an
old platform for platforms that ship system headers in /usr/include)
will require a recent Clang that supports the using_if_exists attribute.
When using an older Clang or GCC, the underlying platform has to support
a C11 standard library.

The motivation for this change is that our logic for determining whether
those functions are provided was wrong in at least some cases (some Apple
platforms). Instead of fixing that logic, the goal has always been to
remove it entirely in favour of the using_if_exists attribute, so that's
what this patch does.

[ldionne]

Pinging a few vendors to make sure this change isn't an issue for them (please read the change description to understand the impact).

[ldionne]

Expand the change to timespec_get and quick_exit.

Note that we'll have to wait for a while before we can submit this change, since we need to drop support
for Clang 12 (which doesn't support the attribute). I'm putting this patch up for review to give a heads
up to vendors and to show that this is the ideal direction for the library, but I'll also have to fix the
incorrect logic separately on Apple platforms.

[phosek]

We always build libc++ with the just built Clang so from our perspective this change should have no impact but thanks for checking.

[dim]

In D108203#2949462, @ldionne wrote:

Expand the change to timespec_get and quick_exit.

Note that we'll have to wait for a while before we can submit this change, since we need to drop support
for Clang 12 (which doesn't support the attribute).

Hm, that's a pity, I wasn't aware that this attribute was introduced so relatively recently. We have clang (and libc++) 11.0.1 in FreeBSD 12.x, which is going to be supported for a while, still. FreeBSD 13.0 and later have clang/libc++ 12.0.1.

I'm putting this patch up for review to give a heads
up to vendors and to show that this is the ideal direction for the library, but I'll also have to fix the
incorrect logic separately on Apple platforms.

In FreeBSD we always import mostly complete copies of the llvm-project tree (except for the parts we don't use), so clang and libc++ are always upgraded at the same time. That said, we also support building the base system (including libc++) using other toolchains such as external gcc's, but we will be able to add version checks for those.

@emaste I think FreeBSD has had aligned_alloc, quick_exit and timespec_get for a very long time now? At least for all supported versions?

[ldionne]

In D108203#2950077, @dim wrote:

In D108203#2949462, @ldionne wrote:

Expand the change to timespec_get and quick_exit.

Note that we'll have to wait for a while before we can submit this change, since we need to drop support
for Clang 12 (which doesn't support the attribute).

Hm, that's a pity, I wasn't aware that this attribute was introduced so relatively recently. We have clang (and libc++) 11.0.1 in FreeBSD 12.x, which is going to be supported for a while, still. FreeBSD 13.0 and later have clang/libc++ 12.0.1.

FWIW, I think that's fine. We have a compiler support policy and we should stand by it. We negotiated that policy so it would be reasonable for both users of libc++ and the libc++ project itself, waiting approximately a year before ripping out this workaround is really not a big deal. What's important is that we can do it in a reasonable time frame, and I think that's enough.

For the time being, I'm about to check-in a patch that bypasses this whole logic whenever the compiler supports using_if_exists, so from our perspective, this code won't be used anymore anyways.

[ldionne]

Rebase onto D108297. I'll land this once we drop support for Clang 12.

[ldionne]

Rebase onto main

[ldionne]

Rebase onto main. This should be ready to land since we don't support compilers without using_if_exists (except GCC, but we assume a proper C11 implementation on that compiler).

libcxx/include/__config

 // a MS compatibility version is specified.
 #  if defined(_MSC_VER) && !defined(__MINGW32__)
 #    define _LIBCPP_MSVCRT // Using Microsoft's C Runtime library
 #  endif
 #  if (defined(_M_AMD64) || defined(__x86_64__)) || (defined(_M_ARM) || defined(__arm__))
 #    define _LIBCPP_HAS_BITSCAN64
 #  endif
 #  define _LIBCPP_HAS_OPEN_WITH_WCHAR
-#  if defined(_LIBCPP_MSVCRT)
-#    define _LIBCPP_HAS_QUICK_EXIT
-#  endif
 
 // Some CRT APIs are unavailable to store apps
 #  if defined(WINAPI_FAMILY)
 #    include <winapifamily.h>
 #    if !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP) &&                  \
         (!defined(WINAPI_PARTITION_SYSTEM) ||                                  \
          !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_SYSTEM))
 #      define _LIBCPP_WINDOWS_STORE_APP

 #endif // !defined(_LIBCPP_LITTLE_ENDIAN) && !defined(_LIBCPP_BIG_ENDIAN)
 
 #if __has_attribute(__no_sanitize__) && !defined(_LIBCPP_COMPILER_GCC)
 #  define _LIBCPP_NO_CFI __attribute__((__no_sanitize__("cfi")))
 #else
 #  define _LIBCPP_NO_CFI
 #endif
 
-#if (defined(__ISO_C_VISIBLE) && (__ISO_C_VISIBLE >= 2011)) || __cplusplus >= 201103L
-#  if defined(__FreeBSD__)
-#    define _LIBCPP_HAS_ALIGNED_ALLOC
-#    define _LIBCPP_HAS_QUICK_EXIT
-#    if __FreeBSD_version >= 1300064 || \
-       (__FreeBSD_version >= 1201504 && __FreeBSD_version < 1300000)
-#      define _LIBCPP_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(__BIONIC__)
-#    if __ANDROID_API__ >= 21
-#      define _LIBCPP_HAS_QUICK_EXIT
-#    endif
-#    if __ANDROID_API__ >= 28
-#      define _LIBCPP_HAS_ALIGNED_ALLOC
-#    endif
-#    if __ANDROID_API__ >= 29
-#      define _LIBCPP_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(__Fuchsia__) || defined(__wasi__) || defined(__NetBSD__)
-#    define _LIBCPP_HAS_ALIGNED_ALLOC
-#    define _LIBCPP_HAS_QUICK_EXIT
-#    define _LIBCPP_HAS_TIMESPEC_GET
-#  elif defined(__OpenBSD__)
-#    define _LIBCPP_HAS_ALIGNED_ALLOC
-#    define _LIBCPP_HAS_TIMESPEC_GET
-#  elif defined(__linux__)
-#    if !defined(_LIBCPP_HAS_MUSL_LIBC)
-#      if _LIBCPP_GLIBC_PREREQ(2, 15) || defined(__BIONIC__)
-#        define _LIBCPP_HAS_QUICK_EXIT
-#      endif
-#      if _LIBCPP_GLIBC_PREREQ(2, 17)
-#        define _LIBCPP_HAS_ALIGNED_ALLOC
-#        define _LIBCPP_HAS_TIMESPEC_GET
-#      endif
-#    else // defined(_LIBCPP_HAS_MUSL_LIBC)
-#      define _LIBCPP_HAS_ALIGNED_ALLOC
-#      define _LIBCPP_HAS_QUICK_EXIT
-#      define _LIBCPP_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(_LIBCPP_MSVCRT)
-     // Using Microsoft's C Runtime library, not MinGW
-#    define _LIBCPP_HAS_TIMESPEC_GET
-#  elif defined(__APPLE__)
-     // timespec_get and aligned_alloc were introduced in macOS 10.15 and
-     // aligned releases
-#    if ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101500) || \
-         (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 130000) || \
-         (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 130000) || \
-         (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 60000))
-#      define _LIBCPP_HAS_ALIGNED_ALLOC
-#      define _LIBCPP_HAS_TIMESPEC_GET
-#    endif
-#  endif // __APPLE__
-#endif
-
 #ifndef _LIBCPP_CXX03_LANG
 # define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp)
 #elif defined(_LIBCPP_COMPILER_CLANG_BASED)
 # define _LIBCPP_ALIGNOF(_Tp) _Alignof(_Tp)
 #else
 # error "We don't know a correct way to implement alignof(T) in C++03 outside of Clang"
 #endif
 

libcxx/include/cstdlib

 #ifndef _LIBCPP_HAS_NO_LONG_LONG
 using ::lldiv _LIBCPP_USING_IF_EXISTS;
 #endif // _LIBCPP_HAS_NO_LONG_LONG
 using ::mblen _LIBCPP_USING_IF_EXISTS;
 using ::mbtowc _LIBCPP_USING_IF_EXISTS;
 using ::wctomb _LIBCPP_USING_IF_EXISTS;
 using ::mbstowcs _LIBCPP_USING_IF_EXISTS;
 using ::wcstombs _LIBCPP_USING_IF_EXISTS;
-#if !defined(_LIBCPP_CXX03_LANG) && defined(_LIBCPP_HAS_QUICK_EXIT)
+#if !defined(_LIBCPP_CXX03_LANG)
 using ::at_quick_exit _LIBCPP_USING_IF_EXISTS;
 using ::quick_exit _LIBCPP_USING_IF_EXISTS;
 #endif
-#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_ALIGNED_ALLOC)
+#if _LIBCPP_STD_VER > 14
 using ::aligned_alloc _LIBCPP_USING_IF_EXISTS;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_CSTDLIB

libcxx/include/ctime

 
 #include <__config>
 #include <time.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-// FIXME:
-// Apple SDKs don't define ::timespec_get unconditionally in C++ mode. This
-// should be fixed in future SDKs, but for the time being we need to avoid
-// trying to use that declaration when the SDK doesn't provide it. Note that
-// 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__)
-#   include <sys/cdefs.h>
-#   if defined(_LIBCPP_HAS_TIMESPEC_GET) && (__DARWIN_C_LEVEL < __DARWIN_C_FULL)
-#       define _LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED
-#   endif
-#endif
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 using ::clock_t _LIBCPP_USING_IF_EXISTS;
 using ::size_t _LIBCPP_USING_IF_EXISTS;
 using ::time_t _LIBCPP_USING_IF_EXISTS;
 using ::tm _LIBCPP_USING_IF_EXISTS;
-#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_TIMESPEC_GET)
+#if _LIBCPP_STD_VER > 14
 using ::timespec _LIBCPP_USING_IF_EXISTS;
 #endif
 using ::clock _LIBCPP_USING_IF_EXISTS;
 using ::difftime _LIBCPP_USING_IF_EXISTS;
 using ::mktime _LIBCPP_USING_IF_EXISTS;
 using ::time _LIBCPP_USING_IF_EXISTS;
 #ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
 using ::asctime _LIBCPP_USING_IF_EXISTS;
 using ::ctime _LIBCPP_USING_IF_EXISTS;
 using ::gmtime _LIBCPP_USING_IF_EXISTS;
 using ::localtime _LIBCPP_USING_IF_EXISTS;
 #endif
 using ::strftime _LIBCPP_USING_IF_EXISTS;
-#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_TIMESPEC_GET) && !defined(_LIBCPP_HAS_TIMESPEC_GET_NOT_ACTUALLY_PROVIDED)
+#if _LIBCPP_STD_VER > 14
 using ::timespec_get _LIBCPP_USING_IF_EXISTS;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_CTIME

libcxx/test/libcxx/language.support/has_aligned_alloc.compile.pass.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14
-
-// Make sure TEST_HAS_ALIGNED_ALLOC (defined by the test suite) and
-// _LIBCPP_HAS_ALIGNED_ALLOC (defined by libc++) stay in sync.
-
-#include <__config>
-#include "test_macros.h"
-
-#if defined(TEST_HAS_ALIGNED_ALLOC) != defined(_LIBCPP_HAS_ALIGNED_ALLOC)
-#   error "TEST_HAS_ALIGNED_ALLOC and _LIBCPP_HAS_ALIGNED_ALLOC are out of sync"
-#endif

libcxx/test/libcxx/language.support/has_quick_exit.compile.pass.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14
-
-// Make sure TEST_HAS_QUICK_EXIT (defined by the test suite) and
-// _LIBCPP_HAS_QUICK_EXIT (defined by libc++) stay in sync.
-
-#include <__config>
-#include "test_macros.h"
-
-#if defined(TEST_HAS_QUICK_EXIT) != defined(_LIBCPP_HAS_QUICK_EXIT)
-#   error "TEST_HAS_QUICK_EXIT and _LIBCPP_HAS_QUICK_EXIT are out of sync"
-#endif

libcxx/test/libcxx/language.support/has_timespec_get.compile.pass.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14
-
-// Make sure TEST_HAS_TIMESPEC_GET (defined by the test suite) and
-// _LIBCPP_HAS_TIMESPEC_GET (defined by libc++) stay in sync.
-
-#include <__config>
-#include "test_macros.h"
-
-#if defined(TEST_HAS_TIMESPEC_GET) != defined(_LIBCPP_HAS_TIMESPEC_GET)
-#   error "TEST_HAS_TIMESPEC_GET and _LIBCPP_HAS_TIMESPEC_GET are out of sync"
-#endif

libcxx/test/std/depr/depr.c.headers/stdlib_h.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 // test <stdlib.h>
 
+// ::aligned_alloc is provided by the C library, but it's marked as unavailable
+// until macOS 10.15
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 #include <stdlib.h>
 #include <type_traits>
 #include <cassert>
 
 #include "test_macros.h"
 
 // As of 1/10/2015 clang emits a -Wnonnull warnings even if the warning occurs
 // in an unevaluated context. For this reason we manually suppress the warning.
int main(int, char**)
     static_assert((std::is_same<decltype(strtold("", endptr)), long double>::value), "");
     static_assert((std::is_same<decltype(strtol("", endptr,0)), long>::value), "");
     static_assert((std::is_same<decltype(strtoll("", endptr,0)), long long>::value), "");
     static_assert((std::is_same<decltype(strtoul("", endptr,0)), unsigned long>::value), "");
     static_assert((std::is_same<decltype(strtoull("", endptr,0)), unsigned long long>::value), "");
     static_assert((std::is_same<decltype(rand()), int>::value), "");
     static_assert((std::is_same<decltype(srand(0)), void>::value), "");
 
-#if TEST_STD_VER > 14 && defined(TEST_HAS_ALIGNED_ALLOC)
-    static_assert((std::is_same<decltype(aligned_alloc(1, 0)), void*>::value),
-                  "");
+#if TEST_STD_VER > 14
+    static_assert((std::is_same<decltype(aligned_alloc(1, 0)), void*>::value), "");
 #endif
 
     void* pv = 0;
     void (*handler)() = 0;
     int (*comp)(void const*, void const*) = 0;
     static_assert((std::is_same<decltype(calloc(0,0)), void*>::value), "");
     static_assert((std::is_same<decltype(free(0)), void>::value), "");
     static_assert((std::is_same<decltype(malloc(0)), void*>::value), "");

libcxx/test/std/language.support/support.runtime/cstdlib.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 // test <cstdlib>
 
+// ::aligned_alloc is provided by the C library, but it's marked as unavailable
+// until macOS 10.15
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{9|10|11|12|13|14}}
+
 #include <cstdlib>
 #include <type_traits>
 #include <cassert>
 
 #include "test_macros.h"
 
 // As of 1/10/2015 clang emits a -Wnonnull warnings even if the warning occurs
 // in an unevaluated context. For this reason we manually suppress the warning.
int main(int, char**)
     static_assert((std::is_same<decltype(std::strtold("", endptr)), long double>::value), "");
     static_assert((std::is_same<decltype(std::strtol("", endptr,0)), long>::value), "");
     static_assert((std::is_same<decltype(std::strtoll("", endptr,0)), long long>::value), "");
     static_assert((std::is_same<decltype(std::strtoul("", endptr,0)), unsigned long>::value), "");
     static_assert((std::is_same<decltype(std::strtoull("", endptr,0)), unsigned long long>::value), "");
     static_assert((std::is_same<decltype(std::rand()), int>::value), "");
     static_assert((std::is_same<decltype(std::srand(0)), void>::value), "");
 
-#if TEST_STD_VER > 14 && defined(TEST_HAS_ALIGNED_ALLOC)
-    static_assert(
-        (std::is_same<decltype(std::aligned_alloc(1, 0)), void*>::value), "");
+#if TEST_STD_VER > 14
+    static_assert((std::is_same<decltype(std::aligned_alloc(1, 0)), void*>::value), "");
 #endif
 
     void* pv = 0;
     void (*handler)() = 0;
     int (*comp)(void const*, void const*) = 0;
     static_assert((std::is_same<decltype(std::calloc(0,0)), void*>::value), "");
     static_assert((std::is_same<decltype(std::free(0)), void>::value), "");
     static_assert((std::is_same<decltype(std::malloc(0)), void*>::value), "");

libcxx/test/std/language.support/support.runtime/ctime.pass.cpp

 #ifndef NULL
 #error NULL not defined
 #endif
 
 #ifndef CLOCKS_PER_SEC
 #error CLOCKS_PER_SEC not defined
 #endif
 
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
 #ifndef TIME_UTC
 #error TIME_UTC not defined
 #endif
 #endif
 
 int main(int, char**)
 {
     std::clock_t c = 0;
     std::size_t s = 0;
     std::time_t t = 0;
     std::tm tm = {};
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
     std::timespec tmspec = {};
     ((void)tmspec); // Prevent unused warning
 #endif
     ((void)c); // Prevent unused warning
     ((void)s); // Prevent unused warning
     ((void)t); // Prevent unused warning
     ((void)tm); // Prevent unused warning
     static_assert((std::is_same<decltype(std::clock()), std::clock_t>::value), "");
     static_assert((std::is_same<decltype(std::difftime(t,t)), double>::value), "");
     static_assert((std::is_same<decltype(std::mktime(&tm)), std::time_t>::value), "");
     static_assert((std::is_same<decltype(std::time(&t)), std::time_t>::value), "");
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
     static_assert((std::is_same<decltype(std::timespec_get(&tmspec, 0)), int>::value), "");
 #endif
 #ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(std::asctime(&tm)), char*>::value), "");
     static_assert((std::is_same<decltype(std::ctime(&t)), char*>::value), "");
     static_assert((std::is_same<decltype(std::gmtime(&t)), std::tm*>::value), "");
     static_assert((std::is_same<decltype(std::localtime(&t)), std::tm*>::value), "");
 #endif
     char* c1 = 0;
     const char* c2 = 0;
     ((void)c1); // Prevent unused warning
     ((void)c2); // Prevent unused warning
     static_assert((std::is_same<decltype(std::strftime(c1,s,c2,&tm)), std::size_t>::value), "");
 
   return 0;
 }

libcxx/test/std/language.support/support.start.term/at_quick_exit.compile.fail.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03
-
-// test that referencing at_quick_exit when TEST_HAS_QUICK_EXIT is not defined
-// results in a compile error.
-
-#include <cstdlib>
-
-#include "test_macros.h"
-
-void f() { }
-
-int main(int, char**) {
-#if !defined(TEST_HAS_QUICK_EXIT)
-    std::at_quick_exit(f);
-#else
-#   error
-#endif
-    return 0;
-}

libcxx/test/std/language.support/support.start.term/quick_exit.compile.fail.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03
-
-// test that referencing quick_exit when TEST_HAS_QUICK_EXIT is not defined
-// results in a compile error.
-
-#include <cstdlib>
-
-#include "test_macros.h"
-
-int main(int, char**) {
-#if !defined(TEST_HAS_QUICK_EXIT)
-    std::quick_exit(0);
-#else
-#   error
-#endif
-    return 0;
-}

libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03
 
 // test quick_exit and at_quick_exit
 
 #include <cstdlib>
 
-#include "test_macros.h"
-
 void f() {}
 
-int main(int, char**)
-{
-#ifdef TEST_HAS_QUICK_EXIT
+int main(int, char**) {
     std::at_quick_exit(f);
     std::quick_exit(0);
-#endif
-
     return 0;
 }

libcxx/test/std/utilities/time/date.time/ctime.pass.cpp

 #ifndef NULL
 #error NULL not defined
 #endif
 
 #ifndef CLOCKS_PER_SEC
 #error CLOCKS_PER_SEC not defined
 #endif
 
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
 #ifndef TIME_UTC
 #error TIME_UTC not defined
 #endif
 #endif
 
 #if defined(__GNUC__)
 #pragma GCC diagnostic ignored "-Wformat-zero-length"
 #endif
 
 int main(int, char**)
 {
     std::clock_t c = 0;
     std::size_t s = 0;
     std::time_t t = 0;
     std::tm tm = {};
     char str[3];
     ((void)c); // Prevent unused warning
     ((void)s); // Prevent unused warning
     ((void)t); // Prevent unused warning
     ((void)tm); // Prevent unused warning
     ((void)str); // Prevent unused warning
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
     std::timespec tmspec = {};
     ((void)tmspec); // Prevent unused warning
 #endif
 
     static_assert((std::is_same<decltype(std::clock()), std::clock_t>::value), "");
     static_assert((std::is_same<decltype(std::difftime(t,t)), double>::value), "");
     static_assert((std::is_same<decltype(std::mktime(&tm)), std::time_t>::value), "");
     static_assert((std::is_same<decltype(std::time(&t)), std::time_t>::value), "");
-#if TEST_STD_VER > 14 && defined(TEST_HAS_TIMESPEC_GET)
+#if TEST_STD_VER > 14
     static_assert((std::is_same<decltype(std::timespec_get(&tmspec, 0)), int>::value), "");
 #endif
 #ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
     static_assert((std::is_same<decltype(std::asctime(&tm)), char*>::value), "");
     static_assert((std::is_same<decltype(std::ctime(&t)), char*>::value), "");
     static_assert((std::is_same<decltype(std::gmtime(&t)), std::tm*>::value), "");
     static_assert((std::is_same<decltype(std::localtime(&t)), std::tm*>::value), "");
 #endif
     static_assert((std::is_same<decltype(std::strftime(str,s,"",&tm)), std::size_t>::value), "");
 
   return 0;
 }

libcxx/test/support/test_macros.h

 #endif
 
 #if TEST_STD_VER >= 20
 # define TEST_CONSTEXPR_CXX20 constexpr
 #else
 # define TEST_CONSTEXPR_CXX20
 #endif
 
-// Sniff out to see if the underlying C library has C11 features
-// This is cribbed from __config; but lives here as well because we can't assume libc++
-#if (defined(__ISO_C_VISIBLE) && (__ISO_C_VISIBLE >= 2011)) ||                 \
-    TEST_STD_VER >= 11
-#  if defined(__FreeBSD__)
-#    if __FreeBSD_version >= 1300064 || \
-       (__FreeBSD_version >= 1201504 && __FreeBSD_version < 1300000)
-#      define TEST_HAS_TIMESPEC_GET
-#    endif
-#    define TEST_HAS_ALIGNED_ALLOC
-#    define TEST_HAS_QUICK_EXIT
-#  elif defined(__BIONIC__)
-#    if __ANDROID_API__ >= 21
-#      define TEST_HAS_QUICK_EXIT
-#    endif
-#    if __ANDROID_API__ >= 28
-#      define TEST_HAS_ALIGNED_ALLOC
-#    endif
-#    if __ANDROID_API__ >= 29
-#      define TEST_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(__Fuchsia__) || defined(__wasi__) || defined(__NetBSD__)
-#    define TEST_HAS_QUICK_EXIT
-#    define TEST_HAS_ALIGNED_ALLOC
-#    define TEST_HAS_TIMESPEC_GET
-#  elif defined(__linux__)
-// This block preserves the old behavior used by include/__config:
-// _LIBCPP_GLIBC_PREREQ would be defined to 0 if __GLIBC_PREREQ was not
-// available. The configuration here may be too vague though, as Bionic, uClibc,
-// newlib, etc may all support these features but need to be configured.
-#    if defined(TEST_GLIBC_PREREQ)
-#      if TEST_GLIBC_PREREQ(2, 15)
-#        define TEST_HAS_QUICK_EXIT
-#      endif
-#      if TEST_GLIBC_PREREQ(2, 17)
-#        define TEST_HAS_ALIGNED_ALLOC
-#        define TEST_HAS_TIMESPEC_GET
-#      endif
-#    elif defined(_LIBCPP_HAS_MUSL_LIBC)
-#      define TEST_HAS_QUICK_EXIT
-#      define TEST_HAS_ALIGNED_ALLOC
-#      define TEST_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(_WIN32)
-#    if defined(_MSC_VER) && !defined(__MINGW32__)
-#      define TEST_HAS_QUICK_EXIT
-#      define TEST_HAS_TIMESPEC_GET
-#    endif
-#  elif defined(__APPLE__)
-     // timespec_get and aligned_alloc were introduced in macOS 10.15 and
-     // aligned releases
-#    if ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101500) || \
-         (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 130000) || \
-         (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 130000) || \
-         (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 60000))
-#      define TEST_HAS_ALIGNED_ALLOC
-#      define TEST_HAS_TIMESPEC_GET
-#    endif
-#  endif // __APPLE__
-#endif
-
 /* Features that were introduced in C++14 */
 #if TEST_STD_VER >= 14
 #define TEST_HAS_EXTENDED_CONSTEXPR
 #define TEST_HAS_VARIABLE_TEMPLATES
 #endif
 
 /* Features that were introduced in C++17 */
 #if TEST_STD_VER >= 17