Looking into the C++ 17 working draft (http://open-std.org/JTC1/SC22/WG21/ docs/papers/2017/n4659.pdf) <cerrno> is actually the same as the POSIX header.
In section 22.4 (page 517) >The contents of the header<cerrno>are the same as the POSIX header<errno.h>, except thaterrnoshallbe defined as a macro. [Note:The intent is to remain in close alignment with the POSIX standard.— endnote] A separateerrnovalue shall be provided for each thread. And at the bottom of 22.4.1 >The meaning of the macros in this header is defined by the POSIX standard. Regards, David P.S. In the latest working draft this seems now to be section 19.4 instead
