Standard library header <coroutine> (C++20)

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Standard library headers

Language support <cfloat> <climits> <compare> (C++20) <contracts> (C++26) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <type_traits> (C++11) <ratio> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <stdbit.h> (C++26) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <hive> (C++26) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <simd> (C++26) <stdckdint.h> (C++26) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

This header is part of the language support library.

Includes
<compare> (C++20)	Three-way comparison operator support
Classes
coroutine_traits (C++20)	trait type for discovering coroutine promise types (class template)
coroutine_handle (C++20)	used to refer to a suspended or executing coroutine (class template)
std::hash<std::coroutine_handle> (C++20)	hash support for std::coroutine_handle (class template specialization)
No-op Coroutines
noop_coroutine_promise (C++20)	used for coroutines with no observable effects (class)
noop_coroutine_handle (C++20)	std::coroutine_handle<std::noop_coroutine_promise>, intended to refer to a no-op coroutine (typedef)
Trivial Awaitables
suspend_never (C++20)	indicates that an await-expression should never suspend (class)
suspend_always (C++20)	indicates that an await-expression should always suspend (class)
Functions
operator==operator<=> (C++20)	compares two coroutine_handle objects (function)
No-op Coroutines
noop_coroutine (C++20)	creates a coroutine handle that has no observable effects when resumed or destroyed (function)

Synopsis

#include <compare>   namespace std { // coroutine traits template<class R, class... ArgTypes> struct coroutine_traits;   // coroutine handle template<class Promise = void> struct coroutine_handle;   // comparison operators constexpr bool operator==(coroutine_handle<> x, coroutine_handle<> y) noexcept; constexpr strong_ordering operator<=>(coroutine_handle<> x, coroutine_handle<> y) noexcept;   // hash support template<class T> struct hash; template<class P> struct hash<coroutine_handle<P>>;   // no-op coroutines struct noop_coroutine_promise;   template<> struct coroutine_handle<noop_coroutine_promise>; using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;   noop_coroutine_handle noop_coroutine() noexcept;   // trivial awaitables struct suspend_never; struct suspend_always; }

Class template std::coroutine_handle

namespace std { template<> struct coroutine_handle<void> { // construct/reset constexpr coroutine_handle() noexcept; constexpr coroutine_handle(nullptr_t) noexcept; coroutine_handle& operator=(nullptr_t) noexcept;   // export/import constexpr void* address() const noexcept; static constexpr coroutine_handle from_address(void* addr);   // observers constexpr explicit operator bool() const noexcept; bool done() const;   // resumption void operator()() const; void resume() const; void destroy() const;   private: void* ptr; // exposition only };   template<class Promise> struct coroutine_handle { // construct/reset constexpr coroutine_handle() noexcept; constexpr coroutine_handle(nullptr_t) noexcept; static coroutine_handle from_promise(Promise&); coroutine_handle& operator=(nullptr_t) noexcept;   // export/import constexpr void* address() const noexcept; static constexpr coroutine_handle from_address(void* addr);   // conversion constexpr operator coroutine_handle<>() const noexcept;   // observers constexpr explicit operator bool() const noexcept; bool done() const;   // resumption void operator()() const; void resume() const; void destroy() const;   // promise access Promise& promise() const;   private: void* ptr; // exposition only  }; }

Class std::noop_coroutine_promise

namespace std { struct noop_coroutine_promise {}; }

Class std::coroutine_handle<std::noop_coroutine_promise>

namespace std { template<> struct coroutine_handle<noop_coroutine_promise> { // conversion constexpr operator coroutine_handle<>() const noexcept;   // observers constexpr explicit operator bool() const noexcept; constexpr bool done() const noexcept;   // resumption constexpr void operator()() const noexcept; constexpr void resume() const noexcept; constexpr void destroy() const noexcept;   // promise access noop_coroutine_promise& promise() const noexcept;   // address constexpr void* address() const noexcept; private: coroutine_handle(/* unspecified */); void* ptr; // exposition only  }; }

Class std::suspend_never

namespace std { struct suspend_never { constexpr bool await_ready() const noexcept { return true; } constexpr void await_suspend(coroutine_handle<>) const noexcept {} constexpr void await_resume() const noexcept {} }; }

Class std::suspend_always

namespace std { struct suspend_always { constexpr bool await_ready() const noexcept { return false; } constexpr void await_suspend(coroutine_handle<>) const noexcept {} constexpr void await_resume() const noexcept {} }; }