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| author | Eric Blake <eblake@redhat.com> | 2012-10-02 15:29:13 -0600 |
|---|---|---|
| committer | Eric Blake <eblake@redhat.com> | 2012-10-02 19:39:20 -0600 |
| commit | 9500a55f083bb8e55ee938e4532ae6baea702e6b (patch) | |
| tree | 763986d43ad9152c39da431080287959e3c8d5e9 /m4 | |
| parent | 2f58d08d66740bfe7fe5c581027965da04afecd7 (diff) | |
| download | gnulib-9500a55f083bb8e55ee938e4532ae6baea702e6b.tar.gz | |
select: reject invalid file descriptors
POSIX requires invalid file descriptors to be detected rather than
silently ignored. FreeBSD 8.2 detects if fd 0 has been closed
and appears in a set while fd 1 is still open, but mistakenly
optimizes and refuses to check any fds in the set beyond the
maximum open fd.
* 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.
Diffstat (limited to 'm4')
| -rw-r--r-- | m4/select.m4 | 40 |
1 files changed, 39 insertions, 1 deletions
diff --git a/m4/select.m4 b/m4/select.m4 index 037b3d3cfc..d135a39db9 100644 --- a/m4/select.m4 +++ b/m4/select.m4 @@ -1,4 +1,4 @@ -# 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, @@ -46,6 +46,44 @@ changequote([,])dnl *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. |