Defined in header <coroutine>
struct noop_coroutine_promise {};
(since C++20)

noop_coroutine_promise is the promise type of no-op coroutines.

A no-op coroutine behaves as if it.

  • does nothing other than the control flow of a coroutine, and
  • is suspended immediately after beginning and resumption, and
  • has a coroutine state such that destroying the state is no-op, and
  • never reaches its final suspended point if there is any std::coroutine_handle referring to it.

No-op coroutines can be started by std::noop_coroutine, and controlled by the coroutine handle it returns. The returned coroutine handle is of type std::noop_coroutine_handle, which is a synonym for std::coroutine_handle<std::noop_coroutine_promise>.

Some operations of a no-op coroutines are determined no-op at compile time through the type std::noop_coroutine_handle.


See also

creates a coroutine handle that has no observable effects when resumed or destroyed
std::coroutine_handle<std::noop_coroutine_promise>, intended to refer to a no-op coroutine

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