C++ PATCH for c++/48211 (ICE in gc code)

[Jason Merrill <jason at redhat dot com>]

The problem in this PR was that we had a cxx_binding embedded in another 
object and then put a pointer to the cxx_binding in another gc-able 
object.  So when GC ran we tried to mark the cxx_binding and crash, 
because it wasn't allocated separately.

Conveniently, the fix to allocate it separately makes the code simpler.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 47d35e93b23a66a5bb43614875c7ad772e2eb4c5
Author: Jason Merrill <jason@redhat.com>
Date:   Thu May 26 12:59:47 2011 -0400

    	PR c++/48211
    	* name-lookup.h (cp_class_binding): Make base a pointer.
    	* name-lookup.c (new_class_binding): Adjust.
    	(poplevel_class): Adjust.

diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index bb6d4b9..935dd2a 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -319,33 +319,11 @@ new_class_binding (tree name, tree value, tree type, cxx_scope *scope)
   cp_class_binding *cb;
   cxx_binding *binding;
 
-  if (VEC_length (cp_class_binding, scope->class_shadowed))
-    {
-      cp_class_binding *old_base;
-      old_base = VEC_index (cp_class_binding, scope->class_shadowed, 0);
-      if (VEC_reserve (cp_class_binding, gc, scope->class_shadowed, 1))
-	{
-	  /* Fixup the current bindings, as they might have moved.  */
-	  size_t i;
-
-	  FOR_EACH_VEC_ELT (cp_class_binding, scope->class_shadowed, i, cb)
-	    {
-	      cxx_binding **b;
-	      b = &IDENTIFIER_BINDING (cb->identifier);
-	      while (*b != &old_base[i].base)
-		b = &((*b)->previous);
-	      *b = &cb->base;
-	    }
-	}
-      cb = VEC_quick_push (cp_class_binding, scope->class_shadowed, NULL);
-    }
-  else
     cb = VEC_safe_push (cp_class_binding, gc, scope->class_shadowed, NULL);
 
   cb->identifier = name;
-  binding = &cb->base;
+  cb->base = binding = cxx_binding_make (value, type);
   binding->scope = scope;
-  cxx_binding_init (binding, value, type);
   return binding;
 }
 
@@ -2725,7 +2703,10 @@ poplevel_class (void)
   if (level->class_shadowed)
     {
       FOR_EACH_VEC_ELT (cp_class_binding, level->class_shadowed, i, cb)
-	IDENTIFIER_BINDING (cb->identifier) = cb->base.previous;
+	{
+	  IDENTIFIER_BINDING (cb->identifier) = cb->base->previous;
+	  cxx_binding_free (cb->base);
+	}
       ggc_free (level->class_shadowed);
       level->class_shadowed = NULL;
     }
diff --git a/gcc/cp/name-lookup.h b/gcc/cp/name-lookup.h
index 4bf253f..3309f0a 100644
--- a/gcc/cp/name-lookup.h
+++ b/gcc/cp/name-lookup.h
@@ -140,7 +140,7 @@ typedef enum tag_scope {
 } tag_scope;
 
 typedef struct GTY(()) cp_class_binding {
-  cxx_binding base;
+  cxx_binding *base;
   /* The bound name.  */
   tree identifier;
 } cp_class_binding;