[libcxx] remove checks for __STDCPP_THREADS__ as it is defined by compiler

[rnk]

libcxx/include/__config

1159

Let's continue defining __STDCPP_THREADS__ if it's not defined. It's safe. It makes new libc++ work with old clang.

[zequanwu]

address comment.

[rnk]

Looks good, but change the commit message: you are changing libc++, not libc++abi.

[thakis]

(See also https://reviews.llvm.org/D65370 for prior discussion.)

[ldionne]

@zequanwu In the future, please refrain from committing to libc++ or libc++abi unless you have approval of the libcxx or libcxxabi review group. There's a reason why that group is added as a "blocking reviewer", it's because you should wait for it to be green before proceeding.

[zequanwu]

In D92349#2425794, @ldionne wrote:

@zequanwu In the future, please refrain from committing to libc++ or libc++abi unless you have approval of the libcxx or libcxxabi review group. There's a reason why that group is added as a "blocking reviewer", it's because you should wait for it to be green before proceeding.

Okay.

libcxx/include/__config

#error _LIBCPP_HAS_THREAD_API_EXTERNAL may not be defined when \
        _LIBCPP_HAS_NO_THREADS is defined.
 #endif
 
 #if defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(_LIBCPP_HAS_NO_THREADS)
 #error _LIBCPP_HAS_NO_MONOTONIC_CLOCK may only be defined when \
        _LIBCPP_HAS_NO_THREADS is defined.
 #endif
 
-#if defined(__STDCPP_THREADS__) && defined(_LIBCPP_HAS_NO_THREADS)
-#error _LIBCPP_HAS_NO_THREADS cannot be set when __STDCPP_THREADS__ is set.
-#endif
-
 #if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(__STDCPP_THREADS__)
 #define __STDCPP_THREADS__ 1
 #endif
 
 // The glibc and Bionic implementation of pthreads implements
 // pthread_mutex_destroy as nop for regular mutexes. Additionally, Win32
 // mutexes have no destroy mechanism.
 //
 // This optimization can't be performed on Apple platforms, where