33 Thread support library [thread]

33.6 Futures [futures]

33.6.3 Error handling [futures.errors]

const error_category& future_category() noexcept;
Returns:  A reference to an object of a type derived from class error_­category.
The object's default_­error_­condition and equivalent virtual functions shall behave as specified for the class error_­category.
The object's name virtual function shall return a pointer to the string "future".
error_code make_error_code(future_errc e) noexcept;
Returns: error_­code(static_­cast<int>(e), future_­category()).
error_condition make_error_condition(future_errc e) noexcept;
Returns: error_­condition(static_­cast<int>(e), future_­category()).