How do you use std::system_error with GetLastError?

Question

If I call a Win32 function that reports errors via GetLastError, for example RegisterClassEx, how do I throw a std::system_error for that error?

Answer 1

Check on the value of GetLastError() like

DWORD dwErrVal = GetLastError();
std::error_code ec (dwErrVal, std::system_category());
throw std::system_error(ec, "Exception occurred");

See here for error_code and here for std::system_error.