This works as well,
--- FRAMECTL.C.orig     2023-06-06 20:22:56.000000000 -0700
+++ FRAMECTL.C  2023-06-06 20:23:04.000000000 -0700
@@ -360,7 +360,7 @@
         /******************************************************************/
         /* Allow default proc to draw all of the frame.                   */
         /******************************************************************/
-        BOOL rc = (BOOL)DefFrameWndProc( hWnd, msg, mp1, mp2 );
+        DefFrameWndProc( hWnd, msg, mp1, mp2 );
         /******************************************************************/
         /* Get presentation space handle for drawing.                     */
But as Lars said, sometimes these variables should be left in as they may be needed for error checking at some point. The toolkit documentation often shows rc = foo()