patch 8.0.0078
Problem:    Accessing freed memory in quickfix.
Solution:   Reset pointer when freeing 'errorformat'. (Domenique Pelle)
diff --git a/src/testdir/test_quickfix.vim b/src/testdir/test_quickfix.vim
index 118a015..5af46e8 100644
--- a/src/testdir/test_quickfix.vim
+++ b/src/testdir/test_quickfix.vim
@@ -1648,3 +1648,13 @@
 
   set efm&vim
 endfunction
+
+function Test_caddbuffer()
+  " This used to cause a memory access in freed memory
+  let save_efm = &efm
+  set efm=%EEEE%m,%WWWW,%+CCCC%>%#,%GGGG%.#
+  cgetexpr ['WWWW', 'EEEE', 'CCCC']
+  let &efm = save_efm
+  cad
+  bwipe!
+endfunc