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.

3 files changed, 22 insertions, 6 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);
diff --git a/src/conf_post.h b/src/conf_post.h
index 30c948e39af..95ebd5511ca 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -99,12 +99,6 @@ typedef bool bool_bf;
 #define realloc unexec_realloc
 #define free unexec_free
 #endif
-/* The following solves the problem that Emacs hangs when evaluating
-   (make-comint "test0" "/nodir/nofile" nil "") when /nodir/nofile
-   does not exist.  Also, setsid is not allowed in the vfork child's
-   context as of Darwin 9/Mac OS X 10.5.  */
-#undef HAVE_WORKING_VFORK
-#define vfork fork
 #endif  /* DARWIN_OS */
 
 /* If HYBRID_MALLOC is defined (e.g., on Cygwin), emacs will use
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;