Cygwin: spawn: apply PID_NEW_PG flag to spawned child

Previously, it was always applied to "myself", which is only appropriate
in the case of _P_OVERLAY (aka exec).  Apply the flag to "myself" only
in that case, and apply it to the new child instead in other cases.
Also, clear the flag from "myself" in the case of a failed exec.

Fixes: 8d8724e ("Cygwin: pty: Fix Ctrl-C handling further for non-cygwin apps.")
Signed-off-by: Jeremy Drake <[email protected]>

Author: jeremyd2019

winsup/cygwin/spawn.cc

@@ -544,9 +544,6 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	c_flags |= CREATE_NEW_PROCESS_GROUP;
       refresh_cygheap ();
 
-      if (c_flags & CREATE_NEW_PROCESS_GROUP)
-	InterlockedOr ((LONG *) &myself->process_state, PID_NEW_PG);
-
       if (mode == _P_DETACH)
 	/* all set */;
       else if (mode != _P_OVERLAY || !my_wr_proc_pipe)
@@ -605,7 +602,12 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
       ::cygheap->user.deimpersonate ();
 
       if (!real_path.iscygexec () && mode == _P_OVERLAY)
-	InterlockedOr ((LONG *) &myself->process_state, PID_NOTCYGWIN);
+	{
+	  LONG pidflags = PID_NOTCYGWIN;
+	  if (c_flags & CREATE_NEW_PROCESS_GROUP)
+	    pidflags |= PID_NEW_PG;
+	  InterlockedOr ((LONG *) &myself->process_state, pidflags);
+	}
 
       cygpid = (mode != _P_OVERLAY) ? create_cygwin_pid () : myself->pid;
 
@@ -707,7 +709,8 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	      myself->sendsig = myself->exec_sendsig;
 	      myself->exec_sendsig = NULL;
 	    }
-	  InterlockedAnd ((LONG *) &myself->process_state, ~PID_NOTCYGWIN);
+	  InterlockedAnd ((LONG *) &myself->process_state,
+			  ~(PID_NOTCYGWIN|PID_NEW_PG));
 	  /* Reset handle inheritance to default when the execution of a'
 	     non-Cygwin process fails.  Only need to do this for _P_OVERLAY
 	     since the handle will be closed otherwise.  Don't need to do
@@ -769,7 +772,9 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	  myself->set_has_pgid_children ();
 	  ProtectHandle (pi.hThread);
 	  pinfo child (cygpid,
-		       PID_IN_USE | (real_path.iscygexec () ? 0 : PID_NOTCYGWIN));
+		       PID_IN_USE |
+		       (real_path.iscygexec () ? 0 : PID_NOTCYGWIN) |
+		       ((c_flags & CREATE_NEW_PROCESS_GROUP) ? PID_NEW_PG : 0));
 	  if (!child)
 	    {
 	      syscall_printf ("pinfo failed");