[libc++][RFC] Always define internal feature test macros (#89178)

Currently, the library-internal feature test macros are only defined if the feature is not available, and always have the prefix `_LIBCPP_HAS_NO_`. This patch changes that, so that they are always defined and have the prefix `_LIBCPP_HAS_` instead. This changes the canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means that using an undefined macro (e.g. due to a missing include) is diagnosed now. While this is rather unlikely currently, a similar change in `<__configuration/availability.h>` caught a few bugs. This also improves readability, since it removes the double-negation of `#ifndef _LIBCPP_HAS_NO_FEATURE`. The current patch only touches the macros defined in `<__config>`. If people are happy with this approach, I'll make a follow-up PR to also change the macros defined in `<__config_site>`.
llvm · Oct 12, 2024 · ba87515 · ba87515
1 parent dbd1971
commit ba87515
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Showing 136 changed files with 1,003 additions and 813 deletions.
diff --git a/libcxx/include/__atomic/aliases.h b/libcxx/include/__atomic/aliases.h
@@ -37,7 +37,7 @@ using atomic_long   = atomic<long>;
 using atomic_ulong  = atomic<unsigned long>;
 using atomic_llong  = atomic<long long>;
 using atomic_ullong = atomic<unsigned long long>;
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#if _LIBCPP_HAS_CHAR8_T
 using atomic_char8_t = atomic<char8_t>;
 #endif
 using atomic_char16_t = atomic<char16_t>;

diff --git a/libcxx/include/__atomic/atomic_lock_free.h b/libcxx/include/__atomic/atomic_lock_free.h
@@ -18,7 +18,7 @@
 #if defined(__CLANG_ATOMIC_BOOL_LOCK_FREE)
 #  define ATOMIC_BOOL_LOCK_FREE __CLANG_ATOMIC_BOOL_LOCK_FREE
 #  define ATOMIC_CHAR_LOCK_FREE __CLANG_ATOMIC_CHAR_LOCK_FREE
-#  ifndef _LIBCPP_HAS_NO_CHAR8_T
+#  if _LIBCPP_HAS_CHAR8_T
 #    define ATOMIC_CHAR8_T_LOCK_FREE __CLANG_ATOMIC_CHAR8_T_LOCK_FREE
 #  endif
 #  define ATOMIC_CHAR16_T_LOCK_FREE __CLANG_ATOMIC_CHAR16_T_LOCK_FREE
@@ -32,7 +32,7 @@
 #elif defined(__GCC_ATOMIC_BOOL_LOCK_FREE)
 #  define ATOMIC_BOOL_LOCK_FREE __GCC_ATOMIC_BOOL_LOCK_FREE
 #  define ATOMIC_CHAR_LOCK_FREE __GCC_ATOMIC_CHAR_LOCK_FREE
-#  ifndef _LIBCPP_HAS_NO_CHAR8_T
+#  if _LIBCPP_HAS_CHAR8_T
 #    define ATOMIC_CHAR8_T_LOCK_FREE __GCC_ATOMIC_CHAR8_T_LOCK_FREE
 #  endif
 #  define ATOMIC_CHAR16_T_LOCK_FREE __GCC_ATOMIC_CHAR16_T_LOCK_FREE

diff --git a/libcxx/include/__bit/byteswap.h b/libcxx/include/__bit/byteswap.h
@@ -32,15 +32,15 @@ template <integral _Tp>
     return __builtin_bswap32(__val);
   } else if constexpr (sizeof(_Tp) == 8) {
     return __builtin_bswap64(__val);
-#  ifndef _LIBCPP_HAS_NO_INT128
+#  if _LIBCPP_HAS_INT128
   } else if constexpr (sizeof(_Tp) == 16) {
 #    if __has_builtin(__builtin_bswap128)
     return __builtin_bswap128(__val);
 #    else
     return static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val))) << 64 |
            static_cast<_Tp>(byteswap(static_cast<uint64_t>(__val >> 64)));
 #    endif // __has_builtin(__builtin_bswap128)
-#  endif   // _LIBCPP_HAS_NO_INT128
+#  endif   // _LIBCPP_HAS_INT128
   } else {
     static_assert(sizeof(_Tp) == 0, "byteswap is unimplemented for integral types of this size");
   }

diff --git a/libcxx/include/__bit/countl.h b/libcxx/include/__bit/countl.h
@@ -39,7 +39,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
   return __builtin_clzll(__x);
 }
 
-#ifndef _LIBCPP_HAS_NO_INT128
+#if _LIBCPP_HAS_INT128
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_clz(__uint128_t __x) _NOEXCEPT {
 #  if __has_builtin(__builtin_clzg)
   return __builtin_clzg(__x);
@@ -57,7 +57,7 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_clz(__uint128_t __x)
                             : __builtin_clzll(static_cast<unsigned long long>(__x >> 64));
 #  endif
 }
-#endif // _LIBCPP_HAS_NO_INT128
+#endif // _LIBCPP_HAS_INT128
 
 template <class _Tp>
 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int __countl_zero(_Tp __t) _NOEXCEPT {

diff --git a/libcxx/include/__charconv/tables.h b/libcxx/include/__charconv/tables.h
@@ -95,7 +95,7 @@ inline constexpr uint64_t __pow10_64[20] = {
     UINT64_C(1000000000000000000),
     UINT64_C(10000000000000000000)};
 
-#  ifndef _LIBCPP_HAS_NO_INT128
+#  if _LIBCPP_HAS_INT128
 inline constexpr int __pow10_128_offset      = 0;
 inline constexpr __uint128_t __pow10_128[40] = {
     UINT64_C(0),

diff --git a/libcxx/include/__charconv/to_chars_base_10.h b/libcxx/include/__charconv/to_chars_base_10.h
@@ -124,7 +124,7 @@ __base_10_u64(char* __buffer, uint64_t __value) noexcept {
   return __itoa::__append10(__buffer, __value);
 }
 
-#  ifndef _LIBCPP_HAS_NO_INT128
+#  if _LIBCPP_HAS_INT128
 /// \returns 10^\a exp
 ///
 /// \pre \a exp [19, 39]

diff --git a/libcxx/include/__charconv/to_chars_integral.h b/libcxx/include/__charconv/to_chars_integral.h
@@ -71,7 +71,7 @@ __to_chars_itoa(char* __first, char* __last, _Tp __value, false_type) {
     return {__last, errc::value_too_large};
 }
 
-#  ifndef _LIBCPP_HAS_NO_INT128
+#  if _LIBCPP_HAS_INT128
 template <>
 inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
 __to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type) {

diff --git a/libcxx/include/__charconv/traits.h b/libcxx/include/__charconv/traits.h
@@ -88,7 +88,7 @@ struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uin
   }
 };
 
-#  ifndef _LIBCPP_HAS_NO_INT128
+#  if _LIBCPP_HAS_INT128
 template <typename _Tp>
 struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__uint128_t)> > {
   using type = __uint128_t;

diff --git a/libcxx/include/__chrono/exception.h b/libcxx/include/__chrono/exception.h
@@ -73,7 +73,7 @@ class nonexistent_local_time : public runtime_error {
 template <class _Duration>
 [[noreturn]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI void __throw_nonexistent_local_time(
     [[maybe_unused]] const local_time<_Duration>& __time, [[maybe_unused]] const local_info& __info) {
-#    ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+#    if _LIBCPP_HAS_EXCEPTIONS
   throw nonexistent_local_time(__time, __info);
 #    else
   _LIBCPP_VERBOSE_ABORT("nonexistent_local_time was thrown in -fno-exceptions mode");
@@ -117,7 +117,7 @@ class ambiguous_local_time : public runtime_error {
 template <class _Duration>
 [[noreturn]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI void __throw_ambiguous_local_time(
     [[maybe_unused]] const local_time<_Duration>& __time, [[maybe_unused]] const local_info& __info) {
-#    ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+#    if _LIBCPP_HAS_EXCEPTIONS
   throw ambiguous_local_time(__time, __info);
 #    else
   _LIBCPP_VERBOSE_ABORT("ambiguous_local_time was thrown in -fno-exceptions mode");

diff --git a/libcxx/include/__chrono/file_clock.h b/libcxx/include/__chrono/file_clock.h
@@ -47,7 +47,7 @@ _LIBCPP_END_NAMESPACE_STD
 #ifndef _LIBCPP_CXX03_LANG
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 struct _FilesystemClock {
-#  if !defined(_LIBCPP_HAS_NO_INT128)
+#  if _LIBCPP_HAS_INT128
   typedef __int128_t rep;
   typedef nano period;
 #  else

diff --git a/libcxx/include/__condition_variable/condition_variable.h b/libcxx/include/__condition_variable/condition_variable.h
@@ -45,7 +45,7 @@ class _LIBCPP_EXPORTED_FROM_ABI condition_variable {
 public:
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR condition_variable() _NOEXCEPT = default;
 
-#  ifdef _LIBCPP_HAS_TRIVIAL_CONDVAR_DESTRUCTION
+#  if _LIBCPP_HAS_TRIVIAL_CONDVAR_DESTRUCTION
   ~condition_variable() = default;
 #  else
   ~condition_variable();
@@ -83,7 +83,7 @@ class _LIBCPP_EXPORTED_FROM_ABI condition_variable {
 private:
   void
   __do_timed_wait(unique_lock<mutex>& __lk, chrono::time_point<chrono::system_clock, chrono::nanoseconds>) _NOEXCEPT;
-#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+#  if _LIBCPP_HAS_COND_CLOCKWAIT
   _LIBCPP_HIDE_FROM_ABI void
   __do_timed_wait(unique_lock<mutex>& __lk, chrono::time_point<chrono::steady_clock, chrono::nanoseconds>) _NOEXCEPT;
 #  endif
@@ -180,7 +180,7 @@ cv_status condition_variable::wait_for(unique_lock<mutex>& __lk, const chrono::d
   using __ns_rep                   = nanoseconds::rep;
   steady_clock::time_point __c_now = steady_clock::now();
 
-#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+#  if _LIBCPP_HAS_COND_CLOCKWAIT
   using __clock_tp_ns     = time_point<steady_clock, nanoseconds>;
   __ns_rep __now_count_ns = std::__safe_nanosecond_cast(__c_now.time_since_epoch()).count();
 #  else
@@ -205,7 +205,7 @@ condition_variable::wait_for(unique_lock<mutex>& __lk, const chrono::duration<_R
   return wait_until(__lk, chrono::steady_clock::now() + __d, std::move(__pred));
 }
 
-#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+#  if _LIBCPP_HAS_COND_CLOCKWAIT
 inline void condition_variable::__do_timed_wait(
     unique_lock<mutex>& __lk, chrono::time_point<chrono::steady_clock, chrono::nanoseconds> __tp) _NOEXCEPT {
   using namespace chrono;