Basic demo for std::error_code

error_code_example.cpp

// Taken from http://stackoverflow.com/questions/11973798/comparing-an-error-code-enum-with-stderror-code

#include <iostream>
using namespace std;
#include <system_error>
#include <cassert>
 
namespace mylib
{
    namespace errc {
 
        enum my_error
        {
            failed = 0
        };
 
        inline const char* error_message(int c)
        {
            static const char* err_msg[] = 
            {
                "Failed",
            };
 
            assert(c < sizeof(err_msg) / sizeof(err_msg[0]));
            return err_msg[c];
        }
 
        class my_error_category : public std::error_category
        {
            public:
 
            my_error_category()
            { }
 
            std::string message(int c) const
            { 
                return error_message(c); 
            }
 
            const char* name() const { return "My Error Category"; }
 
            const static error_category& get()
            {
                const static my_error_category category_const;
                return category_const;
            }
        };
 
	inline std::error_code make_error_code(my_error e)
	{
    		return std::error_code(static_cast<int>(e), my_error_category::get());
	}
 
    } // end namespace errc
} // end namespace mylib
 
namespace std {
 
template<>
struct is_error_code_enum<mylib::errc::my_error>
    : std::true_type
{ }; 
 
} // end namespace std
 
int main()
{
    std::error_code ec1 = mylib::errc::make_error_code(mylib::errc::failed); // works
    std::error_code ec2 = mylib::errc::failed; // works
    bool result = (ec2 == mylib::errc::failed); // works
 
    std::cout << ec1 << std::endl;
}