@item
This header file is missing on some platforms:
mingw, MSVC 9.
+@item
+This header does not declare @code{pid_t} on all platforms:
+glibc on some architectures, FreeBSD 6.4, OpenBSD 4.9, Cygwin 1.7.11.
@end itemize
Portability problems not fixed by Gnulib: