getdtablesize: work around cygwin issue Cygwin 1.7.25 has a bug that even though it claims to support RLIMIT_NOFILE inheritance, there is no enforcement of the soft limit, and getdtablesize() automatically grows until it reaches the hard limit which cannot be changed by setrlimit(). Best is to just treat things as an invariant limit, as several other modules assume that getdtablesize() will not change without an intervening setrlimit(). * m4/getdtablesize.m4 (gl_FUNC_GETDTABLESIZE): Detect problem. * modules/getdtablesize (configure.ac): Build replacement. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Set up a witness. * modules/unistd (Makefile.am): Expose the witness. * lib/unistd.in.h (getdtablesize): Declare replacement. * lib/getdtablesize.c (rpl_getdtablesize): Work around it. * tests/test-getdtablesize.c (main): Test it. * doc/glibc-functions/getdtablesize.texi (getdtablesize): Document it. Signed-off-by: Eric Blake <eblake@redhat.com>

@node getdtablesize
@subsection @code{getdtablesize}
@findex getdtablesize

Gnulib module: getdtablesize

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
mingw, MSVC 9.

@item
This function does not represent the true @code{RLIMIT_NOFILE} soft
limit on some platforms:
Cygwin 1.7.25.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@end itemize