patch 8.0.0069
Problem:    Compiler warning for self-comparison.
Solution:   Define ONE_WINDOW and add #ifdef.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 6802b8b..dcb5cfe 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -7239,7 +7239,7 @@
 	 * :h|wincmd w|1q     - don't quit
 	 * :h|wincmd w|q      - quit
 	 */
-	if (only_one_window() && (firstwin == lastwin || eap->addr_count == 0))
+	if (only_one_window() && (ONE_WINDOW || eap->addr_count == 0))
 #endif
 	    getout(0);
 #ifdef FEAT_WINDOWS