5 POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/waitid.html}
9 Portability problems fixed by Gnulib:
13 Portability problems not fixed by Gnulib:
16 This function is missing on some platforms:
17 FreeBSD 6.0, NetBSD 7.1, OpenBSD 6.7, Minix 3.1.8, Cygwin 2.9, mingw, MSVC 14.
19 As of 2005, no system is known on which @code{waitid} with flag @code{WNOWAIT}