* NEWS, doc/posix-functions/open.texi:
* doc/posix-functions/openat.texi: Document this.
* lib/fcntl.in.h (O_CLOEXEC): Default to a nonzero value.
(GNULIB_defined_O_CLOEXEC): New symbol.
* lib/open.c: Include cloexec.h.
(open): Support O_CLOEXEC.
* lib/openat.c: Include cloexec.h.
(rpl_openat): Support O_CLOEXEC.
* lib/popen-safer.c: Do not include cloexec.h.
(open_noinherit): Remove.
(popen_safer): Use O_CLOEXEC instead of set_cloexec_flag.
* lib/save-cwd.c: Do not include cloexec.h.
(save_cwd): Use O_CLOEXEC instead of set_cloexec_flag.
* m4/open-cloexec.m4: New file.
* m4/open.m4 (gl_FUNC_OPEN): Require gl_PREPROC_O_CLOEXEC.
Replace 'open' if O_CLOEXEC is not present.
* m4/openat.m4 (gl_FUNC_OPENAT): Require gl_PREPROC_O_CLOEXEC.
Replace 'openat' if O_CLOEXEC is not present.
* modules/freopen (Depends-on): Depend on 'open' if replacing freopen.
* modules/open (Files): Add m4/open-cloexec.m4.
(Depends-on): Depend on cloexec if replacing 'open'.
* modules/openat (Files): Add m4/open-cloexec.m4.
(Depends-on): Depend on cloexec if replacing openat.
* modules/popen-safer (Depends-on): Remove cloexec.
* modules/save-cwd (Depends-on): Remove cloexec, and add
fd-safer-flag and 'open'.
* modules/popen-safer: New file.
* lib/popen-safer.c: Likewise.
* m4/stdio-safer.m4 (gl_POPEN_SAFER): New macro.
* lib/stdio--.h (popen): Provide override.
* lib/stdio-safer.h (popen_safer): Provide declaration.
* tests/test-popen.c (includes): Partially test this.
* modules/popen-safer-tests: New file, for more tests.
* tests/test-popen-safer.c: Likewise.
* MODULES.html.sh (file stream based Input/Output): Mention it.
Signed-off-by: Eric Blake <ebb9@byu.net>