libcxx/include/__coroutine/noop_coroutine_handle.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___COROUTINE_NOOP_COROUTINE_HANDLE_H
  10 #define _LIBCPP___COROUTINE_NOOP_COROUTINE_HANDLE_H
  11
  12 #include <__config>
  13 #include <__coroutine/coroutine_handle.h>
  14
  15 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  16 #  pragma GCC system_header
  17 #endif
  18
  19 #if _LIBCPP_STD_VER >= 20
  20
  21 _LIBCPP_BEGIN_NAMESPACE_STD
  22
  23 #  if __has_builtin(__builtin_coro_noop) || defined(_LIBCPP_COMPILER_GCC)
  24
  25 // [coroutine.noop]
  26 // [coroutine.promise.noop]
  27 struct noop_coroutine_promise {};
  28
  29 // [coroutine.handle.noop]
  30 template <>
  31 struct _LIBCPP_TEMPLATE_VIS coroutine_handle<noop_coroutine_promise> {
  32 public:
  33   // [coroutine.handle.noop.conv], conversion
  34   _LIBCPP_HIDE_FROM_ABI constexpr operator coroutine_handle<>() const noexcept {
  35     return coroutine_handle<>::from_address(address());
  36   }
  37
  38   // [coroutine.handle.noop.observers], observers
  39   _LIBCPP_HIDE_FROM_ABI constexpr explicit operator bool() const noexcept { return true; }
  40   _LIBCPP_HIDE_FROM_ABI constexpr bool done() const noexcept { return false; }
  41
  42   // [coroutine.handle.noop.resumption], resumption
  43   _LIBCPP_HIDE_FROM_ABI constexpr void operator()() const noexcept {}
  44   _LIBCPP_HIDE_FROM_ABI constexpr void resume() const noexcept {}
  45   _LIBCPP_HIDE_FROM_ABI constexpr void destroy() const noexcept {}
  46
  47   // [coroutine.handle.noop.promise], promise access
  48   _LIBCPP_HIDE_FROM_ABI noop_coroutine_promise& promise() const noexcept {
  49     return *static_cast<noop_coroutine_promise*>(
  50         __builtin_coro_promise(this->__handle_, alignof(noop_coroutine_promise), false));
  51   }
  52
  53   // [coroutine.handle.noop.address], address
  54   _LIBCPP_HIDE_FROM_ABI constexpr void* address() const noexcept { return __handle_; }
  55
  56 private:
  57   _LIBCPP_HIDE_FROM_ABI friend coroutine_handle<noop_coroutine_promise> noop_coroutine() noexcept;
  58
  59 #    if __has_builtin(__builtin_coro_noop)
  60   _LIBCPP_HIDE_FROM_ABI coroutine_handle() noexcept { this->__handle_ = __builtin_coro_noop(); }
  61
  62   void* __handle_ = nullptr;
  63
  64 #    elif defined(_LIBCPP_COMPILER_GCC)
  65   // GCC doesn't implement __builtin_coro_noop().
  66   // Construct the coroutine frame manually instead.
  67   struct __noop_coroutine_frame_ty_ {
  68     static void __dummy_resume_destroy_func() {}
  69
  70     void (*__resume_)()  = __dummy_resume_destroy_func;
  71     void (*__destroy_)() = __dummy_resume_destroy_func;
  72     struct noop_coroutine_promise __promise_;
  73   };
  74
  75   static __noop_coroutine_frame_ty_ __noop_coroutine_frame_;
  76
  77   void* __handle_ = &__noop_coroutine_frame_;
  78
  79   _LIBCPP_HIDE_FROM_ABI coroutine_handle() noexcept = default;
  80
  81 #    endif // __has_builtin(__builtin_coro_noop)
  82 };
  83
  84 using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;
  85
  86 #    if defined(_LIBCPP_COMPILER_GCC)
  87 inline noop_coroutine_handle::__noop_coroutine_frame_ty_ noop_coroutine_handle::__noop_coroutine_frame_{};
  88 #    endif
  89
  90 // [coroutine.noop.coroutine]
  91 inline _LIBCPP_HIDE_FROM_ABI noop_coroutine_handle noop_coroutine() noexcept { return noop_coroutine_handle(); }
  92
  93 #  endif // __has_builtin(__builtin_coro_noop) || defined(_LIBCPP_COMPILER_GCC)
  94
  95 _LIBCPP_END_NAMESPACE_STD
  96
  97 #endif // __LIBCPP_STD_VER >= 20
  98
  99 #endif // _LIBCPP___COROUTINE_NOOP_COROUTINE_HANDLE_H