2016-01-28  Jakub Jelinek  <jakub@redhat.com>

	PR debug/66869
	* decl.c (wrapup_globals_for_namespace): Warn about unused static
	function declarations.

	* g++.dg/warn/Wunused-function2.C: New test.

--- gcc/cp/decl.c.jj	2016-01-25 09:31:01.000000000 +0100
+++ gcc/cp/decl.c	2016-01-28 13:14:10.783286136 +0100
@@ -879,6 +879,24 @@ wrapup_globals_for_namespace (tree name_
   tree *vec = statics->address ();
   int len = statics->length ();
 
+  if (warn_unused_function)
+    {
+      tree decl;
+      unsigned int i;
+      FOR_EACH_VEC_SAFE_ELT (statics, i, decl)
+	if (TREE_CODE (decl) == FUNCTION_DECL
+	    && DECL_INITIAL (decl) == 0
+	    && DECL_EXTERNAL (decl)
+	    && !TREE_PUBLIC (decl)
+	    && !DECL_ARTIFICIAL (decl)
+	    && !TREE_NO_WARNING (decl))
+	  {
+	    warning (OPT_Wunused_function,
+		     "%q+F declared %<static%> but never defined", decl);
+	    TREE_NO_WARNING (decl) = 1;
+	  }
+    }
+
   /* Write out any globals that need to be output.  */
   return wrapup_global_declarations (vec, len);
 }
--- gcc/testsuite/g++.dg/warn/Wunused-function2.C.jj	2016-01-28 13:40:10.201053364 +0100
+++ gcc/testsuite/g++.dg/warn/Wunused-function2.C	2016-01-28 13:41:43.006788487 +0100
@@ -0,0 +1,6 @@
+// PR debug/66869
+// { dg-do compile }
+// { dg-options "-Wunused-function" }
+
+static void test (void); // { dg-warning "'void test..' declared 'static' but never defined" }
+int i;