vim-patch:8.0.0069

Problem:    Compiler warning for self-comparison.
Solution:   Define ONE_WINDOW and add vim/vim#ifdef.

a1f4cb93ba

src/nvim/globals.h

@@ -494,6 +494,7 @@ EXTERN int updating_screen INIT(= FALSE);
 EXTERN win_T    *firstwin;              /* first window */
 EXTERN win_T    *lastwin;               /* last window */
 EXTERN win_T    *prevwin INIT(= NULL);  /* previous window */
+# define ONE_WINDOW (firstwin == lastwin)
 /*
  * When using this macro "break" only breaks out of the inner loop. Use "goto"
  * to break out of the tabpage loop.