fdopendir: fix GNU/Hurd bug fdopendir(open("file",O_RDONLY)) mistakenly succeeded, with subsequent readdir() failing with ENOTDIR. * m4/fdopendir.m4 (gl_FUNC_FDOPENDIR): Check for Hurd bug in allowing non-directory fds. * lib/fdopendir.c (rpl_fdopendir): Work around it. * m4/dirent_h.m4 (gl_DIRENT_H_DEFAULTS): New witness. * modules/dirent (Makefile.am): Substitute it. * lib/dirent.in.h (fdopendir): Declare replacement. * doc/posix-functions/fdopendir.texi (fdopendir): Document this. * tests/test-fdopendir.c (main): Test something other than /dev/null, since on Hurd that behaves like a directory. Signed-off-by: Eric Blake <ebb9@byu.net>

--- a/doc/posix-functions/fdopendir.texi
+++ b/doc/posix-functions/fdopendir.texi
@@ -16,6 +16,10 @@
 is not multithread-safe.  Also, the replacement does not guarantee
 that @samp{dirfd(fdopendir(n))==n} (dirfd might fail, or return a
 different file descriptor than n).
+@item
+This function does not reject non-directory file descriptors on some
+platforms:
+GNU/Hurd.
 @end itemize
 
 Portability problems not fixed by Gnulib: