NAME¶

std::future_error - std::future_error

Synopsis¶

Defined in header <future>
class future_error; (since C++11)

The class std::future_error defines an exception object that is thrown on failure by
the functions in the thread library that deal with asynchronous execution and shared
states (std::future, std::promise, etc). Similar to std::system_error, this
exception carries an error code compatible with std::error_code.

std-future error-inheritance.svg

Inheritance diagram

Member functions¶

constructor creates a std::future_error object
(public member function)
operator= replaces the std::future_error object
(public member function)
code returns the error code
(public member function)
what returns the explanatory string specific to the error code
(public member function)

Inherited from std::logic_error

Inherited from std::exception

Member functions¶

destructor destroys the exception object
[virtual] (virtual public member function of std::exception)
what returns an explanatory string
[virtual] (virtual public member function of std::exception)

Example¶

// Run this code

#include <future>
#include <iostream>

int main()
{
std::future<int> empty;
try {
int n = empty.get(); // The behavior is undefined, but
// some implementations throw std::future_error
} catch (const std::future_error& e) {
std::cout << "Caught a future_error with code \"" << e.code()
<< "\"\nMessage: \"" << e.what() << "\"\n";
}
}

Possible output:¶

Caught a future_error with code "future:3"
Message: "No associated state"

See also¶

future_errc identifies the future error codes
(C++11) (enum)