OpenBSD /bin/sh, and some other sh variants, squirrel away file
descriptors before closing them. For example, for "cat 3<&-" they
first dup file descriptor 3 to a fd that is 10 or greater, then
close 3 (because if "cat" had been a builtin command like ":" then
they would have wanted to avoid the fork and restore the fd after
":" finished); and they treat ordinary (forking) commands the same
as builtin commands. This approach fails after "ulimit -n 10".
Work around this deficiency by closing the file descriptors before
invoking ulimit. Problem reported by Christian Weisgerber in
<http://lists.gnu.org/archive/html/bug-tar/2010-10/msg00041.html>;
solution suggested by Jilles Tjoelker in
<http://article.gmane.org/gmane.comp.shells.dash/415>.
* tests/extrac11.at (scarce file descriptors): Close file
descriptors before invoking ulimit -n.
* tests/extrac11.at: Replace "((" with "( (" in shell scripts, as
"((" is not portable to the Korn shell, and POSIX 1003.1-2008 says
that "((" is not portable.
* NEWS: Note the change. Mention dirfd and fdopendir.
* gnulib.modules: Add dirfd and fdopendir. The code was already
using fdopendir; dirfd is a new need.
* src/common.h (open_searchdir_flags, get_directory_entries):
(subfile_open, restore_parent_fd, tar_stat_close): New decls.
(check_exclusion_tags): Adjust signature to match code change.
* src/create.c (IMPOSTOR_ERRNO): New constant.
(check_exclusion_tags): First arg is now a struct tar_stat_info
const *, not an fd. All callers changed.
(dump_regular_file, dump_file0): A zero fd represents an unused
slot, so play it safe if the fd member is zero here. A negative
fd represents the negation of an errno value, so play it safe and
do not assign -1 to fd merely because an open fails.
(open_failure_recover, get_directory_entries, restore_parent_fd):
(subfile_open): New functions. These help to recover from file
descriptor exhaustion.
(dump_dir, dump_file0): Use them.
(dump_file0): Use tar_stat_close instead of rolling our own close.
* src/incremen.c (scan_directory): Use get_directory_entries,
subfile_open, etc., to recover from file descriptor exhaustion.
* src/names.c (add_hierarchy_to_namelist): Likewise.
(collect_and_sort_names): A negative fd represents the negation
of an errno value, so play it safe and do not assign -1 to fd.
* src/tar.c (decode_options): Set open_searchdir_flags.
Add O_CLOEXEC to all the open flags.
(tar_stat_close): New function, which knows how to deal with
new convention for directory streams and file descriptors.
Diagnose 'close' failures.
(tar_stat_destroy): Use it.
* src/tar.h (struct tar_stat_info): New member dirstream.
fd now has the negative of an errno value, not merely -1, if
the file could not be opened, so that failures to reopen directories
are better-diagnosed later.
* tests/Makefile.am (TESTSUITE_AT): Add extrac11.at.
* tests/testsuite.at: Likewise.
* tests/extrac11.at: New file.
