2012-10-02 Eric Blake <eblake@redhat.com>
+ select: reject invalid file descriptors
+ * m4/select.m4 (gl_FUNC_SELECT): Probe for FreeBSD bug.
+ * lib/select.c (rpl_select) [!win32]: Work around it.
+ * modules/select (Depends-on): Add dup2.
+ * doc/posix-functions/select.texi (select): Document this.
+
select: enhance test
* tests/test-select.h (do_select_bad_nfd_nowait, test_bad_nfd):
New functions.
@item
This function fails when the @code{nfds} argument is 0 on some platforms:
Interix 3.5.
+@item
+On some platforms, this function fails to detect invalid fds with
+EBADF, but only if they lie beyond the current maximum open fd:
+FreeBSD 8.2.
@end itemize
Portability problems not fixed by Gnulib:
#include <sys/select.h>
#include <stddef.h> /* NULL */
+#include <errno.h>
+#include <unistd.h>
#undef select
rpl_select (int nfds, fd_set *rfds, fd_set *wfds, fd_set *xfds,
struct timeval *timeout)
{
+ int i;
+
+ /* FreeBSD 8.2 has a bug: it does not always detect invalid fds. */
+ if (nfds < 0 || nfds > FD_SETSIZE)
+ {
+ errno = EINVAL;
+ return -1;
+ }
+ for (i = 0; i < nfds; i++)
+ {
+ if (((rfds && FD_ISSET (i, rfds))
+ || (wfds && FD_ISSET (i, wfds))
+ || (xfds && FD_ISSET (i, xfds)))
+ && dup2 (i, i) != i)
+ return -1;
+ }
+
/* Interix 3.5 has a bug: it does not support nfds == 0. */
if (nfds == 0)
{
-# select.m4 serial 6
+# select.m4 serial 7
dnl Copyright (C) 2009-2012 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
*yes) ;;
*) REPLACE_SELECT=1 ;;
esac
+
+ dnl On FreeBSD 8.2, select() doesn't always reject bad fds.
+ AC_CACHE_CHECK([whether select detects invalid fds],
+ [gl_cv_func_select_detects_ebadf],
+ [
+ AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+#include <sys/types.h>
+#include <sys/time.h>
+#if HAVE_SYS_SELECT_H
+# include <sys/select.h>
+#endif
+#include <unistd.h>
+#include <errno.h>
+]],[[
+ fd_set set;
+ dup2(0, 16);
+ FD_ZERO(&set);
+ FD_SET(16, &set);
+ close(16);
+ struct timeval timeout;
+ timeout.tv_sec = 0;
+ timeout.tv_usec = 5;
+ return select (17, &set, NULL, NULL, &timeout) != -1 || errno != EBADF;
+]])], [gl_cv_func_select_detects_ebadf=yes],
+ [gl_cv_func_select_detects_ebadf=no],
+ [
+ case "$host_os" in
+ # Guess yes on glibc systems.
+ *-gnu*) gl_cv_func_select_detects_ebadf="guessing yes" ;;
+ # If we don't know, assume the worst.
+ *) gl_cv_func_select_detects_ebadf="guessing no" ;;
+ esac
+ ])
+ ])
+ case $gl_cv_func_select_detects_ebadf in
+ *yes) ;;
+ *) REPLACE_SELECT=1 ;;
+ esac
fi
dnl Determine the needed libraries.
Depends-on:
sys_select
alloca [test $REPLACE_SELECT = 1]
+dup2 [test $REPLACE_SELECT = 1]
sockets [test $REPLACE_SELECT = 1]
sys_time [test $REPLACE_SELECT = 1]
msvc-nothrow [test $REPLACE_SELECT = 1]