--- ray/src/hd/rholo4.c	1998/05/22 08:30:41	3.18
+++ ray/src/hd/rholo4.c	1998/10/06 18:09:49	3.20
@@ -1,4 +1,4 @@
-/* Copyright (c) 1997 Silicon Graphics, Inc. */
+/* Copyright (c) 1998 Silicon Graphics, Inc. */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ SGI";
@@ -105,10 +105,12 @@ int	block;
 		return(2);		/* acceptable failure */
 	}
 	if (msg.nbytes) {		/* get the message body */
+		if (msg.nbytes < 0)
+			error(INTERNAL, "anti-message from display process");
 		buf = (char *)malloc(msg.nbytes);
 		if (buf == NULL)
 			error(SYSTEM, "out of memory in disp_check");
-		if (fcntl(dpd[0], F_SETFL, inp_flags=0) < 0)
+		if (inp_flags != 0 && fcntl(dpd[0], F_SETFL, inp_flags=0) < 0)
 			goto fcntlerr;
 		if (readbuf(dpd[0], buf, msg.nbytes) != msg.nbytes)
 			goto readerr;
@@ -122,12 +124,17 @@ int	block;
 	case DR_NEWSET:		/* new calculation set */
 		if (msg.nbytes % sizeof(PACKHEAD))
 			error(INTERNAL, "bad DR_NEWSET from display process");
-		disp_result(DS_STARTIMM, 0, NULL);
+		if (msg.nbytes)
+			disp_result(DS_STARTIMM, 0, NULL);
 		bundle_set(BS_NEW, (PACKHEAD *)buf, msg.nbytes/sizeof(PACKHEAD));
-		disp_result(DS_ENDIMM, 0, NULL);
-		disp_flush();
+		if (msg.nbytes) {
+			disp_result(DS_ENDIMM, 0, NULL);
+			disp_flush();
+		}
 		break;
 	case DR_ADDSET:		/* add to calculation set */
+		if (!msg.nbytes)
+			break;
 		if (msg.nbytes % sizeof(PACKHEAD))
 			error(INTERNAL, "bad DR_ADDSET from display process");
 		disp_result(DS_STARTIMM, 0, NULL);
@@ -136,6 +143,8 @@ int	block;
 		disp_flush();
 		break;
 	case DR_ADJSET:		/* adjust calculation set members */
+		if (!msg.nbytes)
+			break;
 		if (msg.nbytes % sizeof(PACKHEAD))
 			error(INTERNAL, "bad DR_ADJSET from display process");
 		disp_result(DS_STARTIMM, 0, NULL);
@@ -144,6 +153,8 @@ int	block;
 		disp_flush();
 		break;
 	case DR_DELSET:		/* delete from calculation set */
+		if (!msg.nbytes)
+			break;
 		if (msg.nbytes % sizeof(PACKHEAD))
 			error(INTERNAL, "bad DR_DELSET from display process");
 		bundle_set(BS_DEL, (PACKHEAD *)buf, msg.nbytes/sizeof(PACKHEAD));
@@ -220,7 +231,11 @@ int	type, nbytes;
 char	*p;
 {
 	MSGHEAD	msg;
-
+					/* consistency checks */
+#ifdef DEBUG
+	if (nbytes < 0 || nbytes > 0 & p == NULL)
+		error(CONSISTENCY, "bad buffer handed to disp_result");
+#endif
 	if (dpout == NULL)
 		return;
 	msg.type = type;