std::error_code::value
From cppreference.com
                    
                                        
                    < cpp | error | error code
                    
                                                            
                    |   int value() const noexcept;  | 
(since C++11) | |
Returns the platform dependent error value.
Parameters
(none)
Return value
The platform-dependent error value.
See also
|    obtains the error_category for this error_code  (public member function)  |