5 POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/fmtmsg.html}
9 Portability problems fixed by Gnulib:
13 Portability problems not fixed by Gnulib:
16 This function is missing on some platforms:
17 OpenBSD 6.7, Minix 3.1.8, Cygwin 2.9, mingw, MSVC 14, Android 9.0.