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, 9 insertions, 0 deletions

diff --git a/src/process.c b/src/process.c
index b81c7b459e3..0edd092ef66 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2049,7 +2049,16 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
   int volatile forkerr_volatile = forkerr;
   struct Lisp_Process *p_volatile = p;
 
+#ifdef DARWIN_OS
+  /* Darwin doesn't let us run setsid after a vfork, so use fork when
+     necessary. */
+  if (pty_flag)
+    pid = fork ();
+  else
+    pid = vfork ();
+#else
   pid = vfork ();
+#endif
 
   current_dir = current_dir_volatile;
   lisp_pty_name = lisp_pty_name_volatile;