[libc++][NFC] Remove __has_keyword

[philnik]

Summary

has_keyword is almost not used anymore. There are only two cases. One can be replaced by has_builtin and the other seems entirely redundant, so we can remove the definition.

[Mordante]

libcxx/include/__config

1157

Why is this NFC?

[philnik]

libcxx/include/__config

1157

Because this is always false for GCC and always true for Clang.

[Mordante]

LGTM!

[hubert.reinterpretcast]

libcxx/include/__config

1157

This is not NFC: -std=gnu++98 -pedantic-errors has this evaluate to false for Clang.

https://godbolt.org/z/xsfvhEfz9

[hubert.reinterpretcast]

This causes #include <algorithm> to fail with -std=gnu++98 -pedantic-errors:

$ clang++ -xc++ -<<<'#include <algorithm>' -std=gnu++98 -pedantic-errors 2>&1 | sed 's#/.*/bin#/bin#;' | head -n 20
In file included from <stdin>:1:
In file included from /bin/../include/c++/v1/algorithm:1811:
In file included from /bin/../include/c++/v1/__algorithm/pstl_any_all_none_of.h:12:
In file included from /bin/../include/c++/v1/__algorithm/pstl_find.h:14:
In file included from /bin/../include/c++/v1/__algorithm/pstl_backend.h:12:
In file included from /bin/../include/c++/v1/__algorithm/pstl_backends/cpu_backend.h:49:
In file included from /bin/../include/c++/v1/__algorithm/pstl_backends/cpu_backends/any_of.h:15:
In file included from /bin/../include/c++/v1/__atomic/atomic.h:12:
In file included from /bin/../include/c++/v1/__atomic/atomic_base.h:12:
In file included from /bin/../include/c++/v1/__atomic/atomic_sync.h:12:
In file included from /bin/../include/c++/v1/__atomic/contention_t.h:12:
/bin/../include/c++/v1/__atomic/cxx_atomic_impl.h:816:28: error: no template named '__cxx_atomic_base_impl'
  816 |           typename _Base = __cxx_atomic_base_impl<_Tp> >
      |                            ^
In file included from <stdin>:1:
In file included from /bin/../include/c++/v1/algorithm:1811:
In file included from /bin/../include/c++/v1/__algorithm/pstl_any_all_none_of.h:12:
In file included from /bin/../include/c++/v1/__algorithm/pstl_find.h:14:
In file included from /bin/../include/c++/v1/__algorithm/pstl_backend.h:12:
In file included from /bin/../include/c++/v1/__algorithm/pstl_backends/cpu_backend.h:49:
Return:  0x00:0   Thu Sep  7 14:34:31 2023 EDT

[xingxue]

I've reverted this patch to unblock the internal AIX buildbot.

[Mordante]

In D158215#4641153, @xingxue wrote:

I've reverted this patch to unblock the internal AIX buildbot.

Thanks! This should at least not be NFC. Since it breaks things I think we should abandon this patch.
At least the new information should be taken into account for the review.

libcxx/include/__config

 #  ifndef __is_identifier
 #    define __is_identifier(__x) 1
 #  endif
 
 #  ifndef __has_declspec_attribute
 #    define __has_declspec_attribute(__x) 0
 #  endif
 
-#  define __has_keyword(__x) !(__is_identifier(__x))
-
 #  ifndef __has_include
 #    define __has_include(...) 0
 #  endif
 
 #  if !defined(_LIBCPP_COMPILER_CLANG_BASED) && __cplusplus < 201103L
 #    error "libc++ only supports C++03 with Clang-based compilers. Please enable C++11"
 #  endif
 

 #    define _LIBCPP_C_HAS_NO_GETS
 #  endif
 
 #  if defined(__BIONIC__) || defined(__NuttX__) || defined(__Fuchsia__) || defined(__wasi__) ||                        \
       defined(_LIBCPP_HAS_MUSL_LIBC) || defined(__OpenBSD__)
 #    define _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE
 #  endif
 
-#  if __has_feature(cxx_atomic) || __has_extension(c_atomic) || __has_keyword(_Atomic)
+#  if __has_feature(cxx_atomic) || __has_extension(c_atomic)
 #    define _LIBCPP_HAS_C_ATOMIC_IMP
 #  elif defined(_LIBCPP_COMPILER_GCC)
 #    define _LIBCPP_HAS_GCC_ATOMIC_IMP
 #  endif
 
 #  if !defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_GCC_ATOMIC_IMP) &&                                    \
       !defined(_LIBCPP_HAS_EXTERNAL_ATOMIC_IMP)
 #    define _LIBCPP_HAS_NO_ATOMIC_HEADER

libcxx/include/tuple

 
 template <size_t _Ip, class _Hp, bool>
 class __tuple_leaf
 {
     _Hp __value_;
 
     template <class _Tp>
     static _LIBCPP_HIDE_FROM_ABI constexpr bool __can_bind_reference() {
-#if __has_keyword(__reference_binds_to_temporary)
+#if __has_builtin(__reference_binds_to_temporary)
       return !__reference_binds_to_temporary(_Hp, _Tp);
 #else
       return true;
 #endif
     }
 
     _LIBCPP_CONSTEXPR_SINCE_CXX14
     __tuple_leaf& operator=(const __tuple_leaf&);