c++ - How to use error_condition in boost::system library? -

is necessary use when return error_code functions? think necessary pass single object class derived error_category error_code object error value. provide error message in category class. error_condition necessary use? difference between , error_code?

quoting this article:

• class error_code - represents specific error value returned operation (such system call).
• class error_condition - want test and, potentially, react in code.

instead of comparing error_code::value os-specific value, 1 should compare error_code against portable error_condition.