8 @ref{Argp,,Parsing Program Options with Argp,libc},
11 @url{https://www.gnu.org/software/libc/manual/html_node/Argp.html}.
17 Portability problems fixed by Gnulib:
20 This header file is missing on all non-glibc platforms:
21 Mac OS X 10.13, FreeBSD 6.0, NetBSD 9.0, OpenBSD 6.7, Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 11.4, Cygwin, mingw, MSVC 14, Android 9.0.
24 Portability problems not fixed by Gnulib: