Make window(1) actually work again. It has been broken for quite some

time now.

For whatever reason, the kernel seems to have generated SIGIOs
previously without an initial fcntl(...,F_SETOWN), but does no longer.
This caused window(1) to wait indefinitely for input.

Also, undo rev 1.3 of wwspawn.c, it was not well-thought, and
apparently not even tested at all.  The blindly (even in a nonsensical
place like the comment on top of the function) applied replacement of
vfork() by fork() totally ignored that window(1) *does* abuse the
feature of vfork() where a modification of the parent's address space
is possible (in this case, to notify the parent of an erred exec*).
Also, with vfork(), it is guaranteed that the parent is only woken up
after the exec*() happened, where the replacement by fork() made the
parent to almost always become runnable again before the child, in
which case the parent simply told `subprocess died'.  Unfortunately,
working around _this_ seems to be a lot more of redesign work compared
to little gained value, so i think relying on the specifics of vfork()
is the simpler way.

Submitted by:	Philipp Mergenthaler <un1i@rz.uni-karlsruhe.de>

usr.bin/window/wwinit.c

@@ -314,6 +314,7 @@ wwinit()
 			wwerrno = WWE_SYS;
 			goto bad;
 		}
+	fcntl(0,F_SETOWN,getpid());
 	/* catch typeahead before ASYNC was set */
 	(void) kill(getpid(), SIGIO);
 	wwstart1();

usr.bin/window/wwspawn.c

@@ -42,7 +42,7 @@ static char sccsid[] = "@(#)wwspawn.c	8.1 (Berkeley) 6/6/93";
 #include <signal.h>
 
 /*
- * There is a dead lock with fork and closing of pseudo-ports.
+ * There is a dead lock with vfork and closing of pseudo-ports.
  * So we have to be sneaky about error reporting.
  */
 wwspawn(wp, file, argv)
@@ -56,7 +56,7 @@ char **argv;
 	int s;
 
 	s = sigblock(sigmask(SIGCHLD));
-	switch (pid = fork()) {
+	switch (pid = vfork()) {
 	case -1:
 		wwerrno = WWE_SYS;
 		ret = -1;