error_code vs errno
c++, c++11, errno, error-handling
Solution
`errno` is used by the those functions that document that as a side effect of their encountering an error - those functions are C library or OS functions that never throw exceptions. `system_error` is a used by the C++ Standard Library for when you're using library facilities documented to throw that exception. Completely separate. Ultimately, read your docs!
Problem
I am studying C++11 standards. I wanted to understand if error_code and errno related to each other? If yes then how? If no then in which conditions i should expect errno to be set and in which conditions error_code will be set? I did a small test program to understand this but still little confused. Please help. ``` #include <iostream> #include <system_error> #include <thread> #include <cstring> #include <cerrno> #include <cstdio> using namespace std; int main() { try { thread().detach(); } catch (const system_error & e) { cout<<"Error code value - "<<e.code().value()<<" ; Meaning - "<<e.what()<<endl; cout<<"Error no. - "<<errno<<" ; Meaning - "<<strerror(errno)<<endl; } } Output - Error code value - 22 ; Meaning - Invalid argument Error no. - 0 ; Meaning - Success ```