C++ PATCH for c++/49663 (ICE in lookup_base)

commit cb313e9af17f34b12a85433a34c14605d3388fc7
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jul 6 18:00:29 2011 -0400

    	PR c++/49663
    	* pt.c (push_deduction_access_scope): Preserve
    	processing_template_decl across push_to_top_level.
    	And revert:
    	* class.c (pushclass): Accept NULL argument.
    	(popclass): Deal with popping null class.
    	* pt.c (push_access_scope, pop_access_scope): Use them rather than
    	push_to_top_level/pop_from_top_level.
    	* name-lookup.c (lookup_name_real_1): Check current_class_type.

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 6aefd68..7de104d 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6125,9 +6125,6 @@  restore_class_cache (void)
    So that we may avoid calls to lookup_name, we cache the _TYPE
    nodes of local TYPE_DECLs in the TREE_TYPE field of the name.
 
-   For use by push_access_scope, we allow TYPE to be null to temporarily
-   push out of class scope.  This does not actually change binding levels.
-
    For multiple inheritance, we perform a two-pass depth-first search
    of the type lattice.  */
 
@@ -6136,6 +6133,8 @@  pushclass (tree type)
 {
   class_stack_node_t csn;
 
+  type = TYPE_MAIN_VARIANT (type);
+
   /* Make sure there is enough room for the new entry on the stack.  */
   if (current_class_depth + 1 >= current_class_stack_size)
     {
@@ -6154,15 +6153,6 @@  pushclass (tree type)
   csn->hidden = 0;
   current_class_depth++;
 
-  if (type == NULL_TREE)
-    {
-      current_class_name = current_class_type = NULL_TREE;
-      csn->hidden = true;
-      return;
-    }
-
-  type = TYPE_MAIN_VARIANT (type);
-
   /* Now set up the new type.  */
   current_class_name = TYPE_NAME (type);
   if (TREE_CODE (current_class_name) == TYPE_DECL)
@@ -6207,11 +6197,7 @@  invalidate_class_lookup_cache (void)
 void
 popclass (void)
 {
-  if (current_class_type)
-    poplevel_class ();
-  else
-    gcc_assert (current_class_depth
-		&& current_class_stack[current_class_depth - 1].hidden);
+  poplevel_class ();
 
   current_class_depth--;
   current_class_name = current_class_stack[current_class_depth].name;
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 615e177..06726da 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -4473,7 +4473,7 @@  lookup_name_real_1 (tree name, int prefer_type, int nonclass, bool block_p,
   /* Conversion operators are handled specially because ordinary
      unqualified name lookup will not find template conversion
      operators.  */
-  if (IDENTIFIER_TYPENAME_P (name) && current_class_type)
+  if (IDENTIFIER_TYPENAME_P (name))
     {
       struct cp_binding_level *level;
 
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 17ca44c..2c64dd4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -214,7 +214,7 @@  push_access_scope (tree t)
   else if (DECL_CLASS_SCOPE_P (t))
     push_nested_class (DECL_CONTEXT (t));
   else
-    pushclass (NULL_TREE);
+    push_to_top_level ();
 
   if (TREE_CODE (t) == FUNCTION_DECL)
     {
@@ -239,7 +239,7 @@  pop_access_scope (tree t)
   if (DECL_FRIEND_CONTEXT (t) || DECL_CLASS_SCOPE_P (t))
     pop_nested_class ();
   else
-    popclass ();
+    pop_from_top_level ();
 }
 
 /* Do any processing required when DECL (a member template
@@ -13843,7 +13843,13 @@  static void
 push_deduction_access_scope (tree tmpl)
 {
   if (cxx_dialect >= cxx0x)
-    push_access_scope (DECL_TEMPLATE_RESULT (tmpl));
+    {
+      int ptd = processing_template_decl;
+      push_access_scope (DECL_TEMPLATE_RESULT (tmpl));
+      /* Preserve processing_template_decl across push_to_top_level.  */
+      if (ptd && !processing_template_decl)
+	++processing_template_decl;
+    }
   else
     push_deferring_access_checks (dk_no_check);
 }
diff --git a/gcc/testsuite/g++.dg/cpp0x/regress/regress4.C b/gcc/testsuite/g++.dg/cpp0x/regress/regress4.C
new file mode 100644
index 0000000..b56263a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/regress/regress4.C
@@ -0,0 +1,62 @@ 
+// PR c++/49663
+// { dg-options -std=c++0x }
+
+struct Nosm
+{
+    int m_R;
+};
+
+namespace dx {
+
+    struct onc
+    {
+        typedef void(*Cb)();
+
+        onc(Cb cb);
+    };
+
+    struct grac
+    {
+        template<class Derived> static void once();
+    };
+
+    template<class Derived>
+        struct tonc : onc
+        {
+            tonc() : onc(&grac::once<Derived>) {}
+
+            static Derived& get();
+        };
+
+    template<class Derived> void grac::once()
+    {
+        tonc<Derived>::get().h();
+    }
+}
+
+namespace
+{
+    template<typename T, int = sizeof(&T::m_R)>
+        struct has_R { };
+
+    template<typename T>
+        inline void
+        setR(T* m, has_R<T>* = 0)
+        { }
+
+    inline void setR(...) { }
+}
+
+template<typename M>
+    struct Qmi
+    : dx::tonc<Qmi<M> >
+    {
+        void h()
+        {
+            setR(&msg);
+        }
+
+        M msg;
+    };
+
+Qmi<Nosm> x;