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
35     constexpr operator coroutine_handle<>() const noexcept {
36         return coroutine_handle<>::from_address(address());
37     }
38 
39     // [coroutine.handle.noop.observers], observers
40     _LIBCPP_HIDE_FROM_ABI
41     constexpr explicit operator bool() const noexcept { return true; }
42     _LIBCPP_HIDE_FROM_ABI
43     constexpr bool done() const noexcept { return false; }
44 
45     // [coroutine.handle.noop.resumption], resumption
46     _LIBCPP_HIDE_FROM_ABI
47     constexpr void operator()() const noexcept {}
48     _LIBCPP_HIDE_FROM_ABI
49     constexpr void resume() const noexcept {}
50     _LIBCPP_HIDE_FROM_ABI
51     constexpr void destroy() const noexcept {}
52 
53     // [coroutine.handle.noop.promise], promise access
54     _LIBCPP_HIDE_FROM_ABI
55     noop_coroutine_promise& promise() const noexcept {
56         return *static_cast<noop_coroutine_promise*>(
57             __builtin_coro_promise(this->__handle_, alignof(noop_coroutine_promise), false));
58     }
59 
60     // [coroutine.handle.noop.address], address
61     _LIBCPP_HIDE_FROM_ABI
62     constexpr void* address() const noexcept { return __handle_; }
63 
64 private:
65     _LIBCPP_HIDE_FROM_ABI
66     friend coroutine_handle<noop_coroutine_promise> noop_coroutine() noexcept;
67 
68 #if __has_builtin(__builtin_coro_noop)
69     _LIBCPP_HIDE_FROM_ABI coroutine_handle() noexcept {
70         this->__handle_ = __builtin_coro_noop();
71     }
72 
73     void* __handle_ = nullptr;
74 
75 #elif defined(_LIBCPP_COMPILER_GCC)
76     // GCC doesn't implement __builtin_coro_noop().
77     // Construct the coroutine frame manually instead.
78     struct __noop_coroutine_frame_ty_ {
79         static void __dummy_resume_destroy_func() { }
80 
81         void (*__resume_)() = __dummy_resume_destroy_func;
82         void (*__destroy_)() = __dummy_resume_destroy_func;
83         struct noop_coroutine_promise __promise_;
84     };
85 
86     static __noop_coroutine_frame_ty_ __noop_coroutine_frame_;
87 
88     void* __handle_ = &__noop_coroutine_frame_;
89 
90     _LIBCPP_HIDE_FROM_ABI coroutine_handle() noexcept = default;
91 
92 #endif // __has_builtin(__builtin_coro_noop)
93 };
94 
95 using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;
96 
97 #if defined(_LIBCPP_COMPILER_GCC)
98 inline noop_coroutine_handle::__noop_coroutine_frame_ty_
99     noop_coroutine_handle::__noop_coroutine_frame_{};
100 #endif
101 
102 // [coroutine.noop.coroutine]
103 inline _LIBCPP_HIDE_FROM_ABI
104 noop_coroutine_handle noop_coroutine() noexcept { return noop_coroutine_handle(); }
105 
106 #endif // __has_builtin(__builtin_coro_noop) || defined(_LIBCPP_COMPILER_GCC)
107 
108 _LIBCPP_END_NAMESPACE_STD
109 
110 #endif // __LIBCPP_STD_VER >= 20
111 
112 #endif // _LIBCPP___COROUTINE_NOOP_COROUTINE_HANDLE_H
113