Author: Julia Lawall <julia@diku.dk> arg is checked not to be NULL a few lines before. A simplified version of the semantic patch that makes this change is as follows: (http://www.emn.fr/x-info/coccinelle/) // @r exists@ local idexpression x; expression E; position p1,p2; @@ if (x@p1 == NULL || …) { … when forall return …; } … …