void set_exception( std::exception_ptr p ); | (since C++11) |
Atomically stores the exception pointer p into the shared state and makes the state ready.
The operation behaves as though set_value, set_exception, set_value_at_thread_exit, and set_exception_at_thread_exit acquire a single mutex associated with the promise object while updating the promise object.
An exception is thrown if there is no shared state or the shared state already stores a value or exception.
Calls to this function do not introduce data races with calls to get_future (therefore they need not synchronize with each other).
| p | - | exception pointer to store. The behavior is undefined if p is null. |
(none).
std::future_error on the following conditions:
*this has no shared state. The error code is set to no_state. promise_already_satisfied. #include <thread>
#include <iostream>
#include <future>
int main()
{
std::promise<int> p;
std::future<int> f = p.get_future();
std::thread t([&p]{
try {
// code that may throw
throw std::runtime_error("Example");
} catch(...) {
try {
// store anything thrown in the promise
p.set_exception(std::current_exception());
// or throw a custom exception instead
// p.set_exception(std::make_exception_ptr(MyException("mine")));
} catch(...) {} // set_exception() may throw too
}
});
try {
std::cout << f.get();
} catch(const std::exception& e) {
std::cout << "Exception from the thread: " << e.what() << '\n';
}
t.join();
}Output:
Exception from the thread: Example
| sets the result to indicate an exception while delivering the notification only at thread exit (public member function) |
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