patch 8.0.0083
Problem:    Using freed memory with win_getid(). (Domenique Pelle)
Solution:   For the current tab use curwin.
diff --git a/src/testdir/test_window_id.vim b/src/testdir/test_window_id.vim
index 66656e1..b3b506d 100644
--- a/src/testdir/test_window_id.vim
+++ b/src/testdir/test_window_id.vim
@@ -92,3 +92,12 @@
 
   only!
 endfunc
+
+func Test_win_getid_curtab()
+  tabedit X
+  tabfirst
+  copen
+  only
+  call assert_equal(win_getid(1), win_getid(1, 1))
+  tabclose!
+endfunc