std::promise<R>::set_exception
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std::promise
Member functions
Getting the result
Setting the result
promise::set_exception
Non-member Functions
Helper Classes
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).
[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
Run this code
#include <future> #include <iostream> #include <thread> 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
[edit] See also
sets the result to indicate an exception while delivering the notification only at thread exit
(public member function) [edit]
(public member function) [edit]