Fix c++/67337 (segfault in mangle.c)

	PR c++/67337
	* mangle.c (write_template_prefix): Guard against context==NULL.

From-SVN: r231203

gcc/cp/ChangeLog

+2015-12-02  Markus Trippelsdorf  <markus@trippelsdorf.de>
+
+	PR c++/67337
+	* mangle.c (write_template_prefix): Guard against context==NULL.
+
 2015-12-02  Jason Merrill  <jason@redhat.com>
 
 	* call.c (build_new_op_1): Don't fold arguments to

gcc/cp/mangle.c

@@ -1145,7 +1145,7 @@ write_template_prefix (const tree node)
      So, for the example above, `Outer<int>::Inner' is represented as a
      substitution candidate by a TREE_LIST whose purpose is `Outer<int>'
      and whose value is `Outer<T>::Inner<U>'.  */
-  if (TYPE_P (context))
+  if (context && TYPE_P (context))
     substitution = build_tree_list (context, templ);
   else
     substitution = templ;

gcc/testsuite/g++.dg/template/pr67337.C

+template <class> class A
+{
+  void m_fn1 (int *, int);
+};
+
+template <class> class B
+{
+public:
+  typedef int Type;
+};
+
+template <class> class C
+{
+public:
+  C (int);
+  template <template <class> class T> void m_fn2 (typename T<void>::Type);
+};
+
+template <>
+void
+A<int>::m_fn1 (int *, int)
+{
+  C<int> a (0);
+  a.m_fn2<B> (0);
+}