Merge from Gnulib; use ‘open’ for O_CLOEXEC

This incorporates:
2017-08-15 renameat: ensure declaration in <stdio.h> on NetBSD
2017-08-15 extensions: enable NetBSD specific extensions
2017-08-14 open: support O_CLOEXEC
2017-08-13 reallocarray: new module
* admin/merge-gnulib (AVOIDED_MODULES): Remove ‘open’, since
it now supports O_CLOEXEC and this simplifies Emacs.
* build-aux/config.guess, lib/fcntl.in.h, lib/stdio.in.h:
* lib/stdlib.in.h, m4/extensions.m4, m4/stdlib_h.m4:
Copy from Gnulib.
* lib/cloexec.c, lib/cloexec.h, lib/open.c:
* m4/mode_t.m4, m4/open-cloexec.m4, m4/open.m4:
New files, copied from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib-src/etags.c (O_CLOEXEC) [WINDOWSNT]:
Remove, as Gnulib does this for us.
* src/filelock.c (create_lock_file):
* src/sysdep.c (emacs_open, emacs_pipe):
Don’t worry about O_CLOEXEC == 0, as Gnulib no longer sets it to 0.

1 files changed, 83 insertions, 0 deletions

diff --git a/lib/cloexec.c b/lib/cloexec.c
new file mode 100644
index 00000000000..e34aef87976
--- /dev/null
+++ b/lib/cloexec.c
@@ -0,0 +1,83 @@
+/* cloexec.c - set or clear the close-on-exec descriptor flag
+
+   Copyright (C) 1991, 2004-2006, 2009-2017 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+   The code is taken from glibc/manual/llio.texi  */
+
+#include <config.h>
+
+#include "cloexec.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+/* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true,
+   or clear the flag if VALUE is false.
+   Return 0 on success, or -1 on error with 'errno' set.
+
+   Note that on MingW, this function does NOT protect DESC from being
+   inherited into spawned children.  Instead, either use dup_cloexec
+   followed by closing the original DESC, or use interfaces such as
+   open or pipe2 that accept flags like O_CLOEXEC to create DESC
+   non-inheritable in the first place.  */
+
+int
+set_cloexec_flag (int desc, bool value)
+{
+#ifdef F_SETFD
+
+  int flags = fcntl (desc, F_GETFD, 0);
+
+  if (0 <= flags)
+    {
+      int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC);
+
+      if (flags == newflags
+          || fcntl (desc, F_SETFD, newflags) != -1)
+        return 0;
+    }
+
+  return -1;
+
+#else /* !F_SETFD */
+
+  /* Use dup2 to reject invalid file descriptors; the cloexec flag
+     will be unaffected.  */
+  if (desc < 0)
+    {
+      errno = EBADF;
+      return -1;
+    }
+  if (dup2 (desc, desc) < 0)
+    /* errno is EBADF here.  */
+    return -1;
+
+  /* There is nothing we can do on this kind of platform.  Punt.  */
+  return 0;
+#endif /* !F_SETFD */
+}
+
+
+/* Duplicates a file handle FD, while marking the copy to be closed
+   prior to exec or spawn.  Returns -1 and sets errno if FD could not
+   be duplicated.  */
+
+int
+dup_cloexec (int fd)
+{
+  return fcntl (fd, F_DUPFD_CLOEXEC, 0);
+}