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Start an asynchronous operation to wait for a signal to be delivered.

    typename SignalToken = default_completion_token_t<executor_type>>
auto async_wait(
    SignalToken && token = default_completion_token_t< executor_type >());

This function may be used to initiate an asynchronous wait against the signal set. It is an initiating function for an asynchronous operation, and always returns immediately.

For each call to async_wait(), the completion handler will be called exactly once. The completion handler will be called when:



The completion token that will be used to produce a completion handler, which will be called when the wait completes. Potential completion tokens include use_future, use_awaitable, yield_context, or a function object with the correct completion signature. The function signature of the completion handler must be:

void handler(
  const boost::system::error_code& error, // Result of operation.
  int signal_number // Indicates which signal occurred.

Regardless of whether the asynchronous operation completes immediately or not, the completion handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using post.

Completion Signature
void(boost::system::error_code, int)
Per-Operation Cancellation

This asynchronous operation supports cancellation for the following cancellation_type values: