std::future_error

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.

Inheritance diagram

Inherited from std::logic_error

Inherited from std::exception

Member functions

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

[edit] 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"

[edit] See also

future_errc

(C++11)

identifies the future error codes
(enum)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member functions
future_error::future_error
future_error::code
future_error::what

(constructor)	creates a `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)