std::promise::set_exception - cppreference.com (original) (raw)
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).
[edit] Parameters
| p | - | exception pointer to store. The behavior is undefined if p is null |
|---|
[edit] Return value
(none)
[edit] Exceptions
std::future_error on the following conditions:
- *this has no shared state. The error code is set to no_state.
- The shared state already stores a value or exception. The error code is set to promise_already_satisfied.
[edit] Example
#include #include #include int main() { std::promise p; std::future 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