diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e416c463c34a..2c77b39666d3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2016-02-23  Mark Wielaard  <mjw@redhat.com>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/69911
+	* cgraphunit.c (check_global_declaration): Check main_input_filename
+	and DECL_SOURCE_FILE are not NULL.
+
 2016-02-23  Martin Jambor  <mjambor@suse.cz>
 
 	PR tree-optimization/69666
diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 27a073a63be1..8b3fddc435eb 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -917,6 +917,7 @@ walk_polymorphic_call_targets (hash_set<void *> *reachable_call_targets,
 static void
 check_global_declaration (symtab_node *snode)
 {
+  const char *decl_file;
   tree decl = snode->decl;
 
   /* Warn about any function declared static but not defined.  We don't
@@ -944,8 +945,10 @@ check_global_declaration (symtab_node *snode)
        || (((warn_unused_variable && ! TREE_READONLY (decl))
 	    || (warn_unused_const_variable > 0 && TREE_READONLY (decl)
 		&& (warn_unused_const_variable == 2
-		    || filename_cmp (main_input_filename,
-				     DECL_SOURCE_FILE (decl)) == 0)))
+		    || (main_input_filename != NULL
+			&& (decl_file = DECL_SOURCE_FILE (decl)) != NULL
+			&& filename_cmp (main_input_filename,
+					 decl_file) == 0))))
 	   && TREE_CODE (decl) == VAR_DECL))
       && ! DECL_IN_SYSTEM_HEADER (decl)
       && ! snode->referred_to_p (/*include_self=*/false)