Use vfork if possible on Darwin (bug#26397)

Co-authored-by: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>

* src/conf_post.h (HAVE_WORKING_VFORK): Don't undef.
(vfork): Don't define.
* src/process.c (create_process) [DARWIN_OS]: Use fork if pty_flag is
set, otherwise vfork.
* src/callproc.c (call_process) [DARWIN_OS]: Use TIOCNOTTY to detach
the controlling terminal instead of setsid.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/callproc.c b/src/callproc.c
index 05048576ce9..792556c8e02 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -52,6 +52,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "syswait.h"
 #include "blockinput.h"
 #include "frame.h"
+#include "systty.h"
+#include "keyboard.h"
 
 #ifdef MSDOS
 #include "msdos.h"
@@ -626,7 +628,18 @@ call_process (ptrdiff_t nargs, Lisp_Object *args, int filefd,
     {
       unblock_child_signal (&oldset);
 
+#ifdef DARWIN_OS
+      /* Darwin doesn't let us run setsid after a vfork, so use
+         TIOCNOTTY when necessary. */
+      int j = emacs_open (DEV_TTY, O_RDWR, 0);
+      if (j >= 0)
+        {
+          ioctl (j, TIOCNOTTY, 0);
+          emacs_close (j);
+        }
+#else
       setsid ();
+#endif
 
       /* Emacs ignores SIGPIPE, but the child should not.  */
       signal (SIGPIPE, SIG_DFL);