--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/cp/search.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,2622 @@
+/* Breadth-first and depth-first routines for
+   searching multiple-inheritance lattice for GNU C++.
+   Copyright (C) 1987-2017 Free Software Foundation, Inc.
+   Contributed by Michael Tiemann (tiemann@cygnus.com)
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+/* High-level class interface.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "cp-tree.h"
+#include "intl.h"
+#include "toplev.h"
+#include "spellcheck-tree.h"
+#include "stringpool.h"
+#include "attribs.h"
+
+static int is_subobject_of_p (tree, tree);
+static tree dfs_lookup_base (tree, void *);
+static tree dfs_dcast_hint_pre (tree, void *);
+static tree dfs_dcast_hint_post (tree, void *);
+static tree dfs_debug_mark (tree, void *);
+static int check_hidden_convs (tree, int, int, tree, tree, tree);
+static tree split_conversions (tree, tree, tree, tree);
+static int lookup_conversions_r (tree, int, int, tree, tree, tree *);
+static int look_for_overrides_r (tree, tree);
+static tree lookup_field_r (tree, void *);
+static tree dfs_accessible_post (tree, void *);
+static tree dfs_walk_once_accessible (tree, bool,
+				      tree (*pre_fn) (tree, void *),
+				      tree (*post_fn) (tree, void *),
+				      void *data);
+static tree dfs_access_in_type (tree, void *);
+static access_kind access_in_type (tree, tree);
+static tree dfs_get_pure_virtuals (tree, void *);
+
+
+/* Data for lookup_base and its workers.  */
+
+struct lookup_base_data_s
+{
+  tree t;		/* type being searched.  */
+  tree base;		/* The base type we're looking for.  */
+  tree binfo;		/* Found binfo.  */
+  bool via_virtual;	/* Found via a virtual path.  */
+  bool ambiguous;	/* Found multiply ambiguous */
+  bool repeated_base;	/* Whether there are repeated bases in the
+			    hierarchy.  */
+  bool want_any;	/* Whether we want any matching binfo.  */
+};
+
+/* Worker function for lookup_base.  See if we've found the desired
+   base and update DATA_ (a pointer to LOOKUP_BASE_DATA_S).  */
+
+static tree
+dfs_lookup_base (tree binfo, void *data_)
+{
+  struct lookup_base_data_s *data = (struct lookup_base_data_s *) data_;
+
+  if (SAME_BINFO_TYPE_P (BINFO_TYPE (binfo), data->base))
+    {
+      if (!data->binfo)
+	{
+	  data->binfo = binfo;
+	  data->via_virtual
+	    = binfo_via_virtual (data->binfo, data->t) != NULL_TREE;
+
+	  if (!data->repeated_base)
+	    /* If there are no repeated bases, we can stop now.  */
+	    return binfo;
+
+	  if (data->want_any && !data->via_virtual)
+	    /* If this is a non-virtual base, then we can't do
+	       better.  */
+	    return binfo;
+
+	  return dfs_skip_bases;
+	}
+      else
+	{
+	  gcc_assert (binfo != data->binfo);
+
+	  /* We've found more than one matching binfo.  */
+	  if (!data->want_any)
+	    {
+	      /* This is immediately ambiguous.  */
+	      data->binfo = NULL_TREE;
+	      data->ambiguous = true;
+	      return error_mark_node;
+	    }
+
+	  /* Prefer one via a non-virtual path.  */
+	  if (!binfo_via_virtual (binfo, data->t))
+	    {
+	      data->binfo = binfo;
+	      data->via_virtual = false;
+	      return binfo;
+	    }
+
+	  /* There must be repeated bases, otherwise we'd have stopped
+	     on the first base we found.  */
+	  return dfs_skip_bases;
+	}
+    }
+
+  return NULL_TREE;
+}
+
+/* Returns true if type BASE is accessible in T.  (BASE is known to be
+   a (possibly non-proper) base class of T.)  If CONSIDER_LOCAL_P is
+   true, consider any special access of the current scope, or access
+   bestowed by friendship.  */
+
+bool
+accessible_base_p (tree t, tree base, bool consider_local_p)
+{
+  tree decl;
+
+  /* [class.access.base]
+
+     A base class is said to be accessible if an invented public
+     member of the base class is accessible.
+
+     If BASE is a non-proper base, this condition is trivially
+     true.  */
+  if (same_type_p (t, base))
+    return true;
+  /* Rather than inventing a public member, we use the implicit
+     public typedef created in the scope of every class.  */
+  decl = TYPE_FIELDS (base);
+  while (!DECL_SELF_REFERENCE_P (decl))
+    decl = DECL_CHAIN (decl);
+  while (ANON_AGGR_TYPE_P (t))
+    t = TYPE_CONTEXT (t);
+  return accessible_p (t, decl, consider_local_p);
+}
+
+/* Lookup BASE in the hierarchy dominated by T.  Do access checking as
+   ACCESS specifies.  Return the binfo we discover.  If KIND_PTR is
+   non-NULL, fill with information about what kind of base we
+   discovered.
+
+   If the base is inaccessible, or ambiguous, then error_mark_node is
+   returned.  If the tf_error bit of COMPLAIN is not set, no error
+   is issued.  */
+
+tree
+lookup_base (tree t, tree base, base_access access,
+	     base_kind *kind_ptr, tsubst_flags_t complain)
+{
+  tree binfo;
+  tree t_binfo;
+  base_kind bk;
+
+  /* "Nothing" is definitely not derived from Base.  */
+  if (t == NULL_TREE)
+    {
+      if (kind_ptr)
+	*kind_ptr = bk_not_base;
+      return NULL_TREE;
+    }
+
+  if (t == error_mark_node || base == error_mark_node)
+    {
+      if (kind_ptr)
+	*kind_ptr = bk_not_base;
+      return error_mark_node;
+    }
+  gcc_assert (TYPE_P (base));
+
+  if (!TYPE_P (t))
+    {
+      t_binfo = t;
+      t = BINFO_TYPE (t);
+    }
+  else
+    {
+      t = complete_type (TYPE_MAIN_VARIANT (t));
+      t_binfo = TYPE_BINFO (t);
+    }
+
+  base = TYPE_MAIN_VARIANT (base);
+
+  /* If BASE is incomplete, it can't be a base of T--and instantiating it
+     might cause an error.  */
+  if (t_binfo && CLASS_TYPE_P (base) && COMPLETE_OR_OPEN_TYPE_P (base))
+    {
+      struct lookup_base_data_s data;
+
+      data.t = t;
+      data.base = base;
+      data.binfo = NULL_TREE;
+      data.ambiguous = data.via_virtual = false;
+      data.repeated_base = CLASSTYPE_REPEATED_BASE_P (t);
+      data.want_any = access == ba_any;
+
+      dfs_walk_once (t_binfo, dfs_lookup_base, NULL, &data);
+      binfo = data.binfo;
+
+      if (!binfo)
+	bk = data.ambiguous ? bk_ambig : bk_not_base;
+      else if (binfo == t_binfo)
+	bk = bk_same_type;
+      else if (data.via_virtual)
+	bk = bk_via_virtual;
+      else
+	bk = bk_proper_base;
+    }
+  else
+    {
+      binfo = NULL_TREE;
+      bk = bk_not_base;
+    }
+
+  /* Check that the base is unambiguous and accessible.  */
+  if (access != ba_any)
+    switch (bk)
+      {
+      case bk_not_base:
+	break;
+
+      case bk_ambig:
+	if (complain & tf_error)
+	  error ("%qT is an ambiguous base of %qT", base, t);
+	binfo = error_mark_node;
+	break;
+
+      default:
+	if ((access & ba_check_bit)
+	    /* If BASE is incomplete, then BASE and TYPE are probably
+	       the same, in which case BASE is accessible.  If they
+	       are not the same, then TYPE is invalid.  In that case,
+	       there's no need to issue another error here, and
+	       there's no implicit typedef to use in the code that
+	       follows, so we skip the check.  */
+	    && COMPLETE_TYPE_P (base)
+	    && !accessible_base_p (t, base, !(access & ba_ignore_scope)))
+	  {
+	    if (complain & tf_error)
+	      error ("%qT is an inaccessible base of %qT", base, t);
+	    binfo = error_mark_node;
+	    bk = bk_inaccessible;
+	  }
+	break;
+      }
+
+  if (kind_ptr)
+    *kind_ptr = bk;
+
+  return binfo;
+}
+
+/* Data for dcast_base_hint walker.  */
+
+struct dcast_data_s
+{
+  tree subtype;   /* The base type we're looking for.  */
+  int virt_depth; /* Number of virtual bases encountered from most
+		     derived.  */
+  tree offset;    /* Best hint offset discovered so far.  */
+  bool repeated_base;  /* Whether there are repeated bases in the
+			  hierarchy.  */
+};
+
+/* Worker for dcast_base_hint.  Search for the base type being cast
+   from.  */
+
+static tree
+dfs_dcast_hint_pre (tree binfo, void *data_)
+{
+  struct dcast_data_s *data = (struct dcast_data_s *) data_;
+
+  if (BINFO_VIRTUAL_P (binfo))
+    data->virt_depth++;
+
+  if (SAME_BINFO_TYPE_P (BINFO_TYPE (binfo), data->subtype))
+    {
+      if (data->virt_depth)
+	{
+	  data->offset = ssize_int (-1);
+	  return data->offset;
+	}
+      if (data->offset)
+	data->offset = ssize_int (-3);
+      else
+	data->offset = BINFO_OFFSET (binfo);
+
+      return data->repeated_base ? dfs_skip_bases : data->offset;
+    }
+
+  return NULL_TREE;
+}
+
+/* Worker for dcast_base_hint.  Track the virtual depth.  */
+
+static tree
+dfs_dcast_hint_post (tree binfo, void *data_)
+{
+  struct dcast_data_s *data = (struct dcast_data_s *) data_;
+
+  if (BINFO_VIRTUAL_P (binfo))
+    data->virt_depth--;
+
+  return NULL_TREE;
+}
+
+/* The dynamic cast runtime needs a hint about how the static SUBTYPE type
+   started from is related to the required TARGET type, in order to optimize
+   the inheritance graph search. This information is independent of the
+   current context, and ignores private paths, hence get_base_distance is
+   inappropriate. Return a TREE specifying the base offset, BOFF.
+   BOFF >= 0, there is only one public non-virtual SUBTYPE base at offset BOFF,
+      and there are no public virtual SUBTYPE bases.
+   BOFF == -1, SUBTYPE occurs as multiple public virtual or non-virtual bases.
+   BOFF == -2, SUBTYPE is not a public base.
+   BOFF == -3, SUBTYPE occurs as multiple public non-virtual bases.  */
+
+tree
+dcast_base_hint (tree subtype, tree target)
+{
+  struct dcast_data_s data;
+
+  data.subtype = subtype;
+  data.virt_depth = 0;
+  data.offset = NULL_TREE;
+  data.repeated_base = CLASSTYPE_REPEATED_BASE_P (target);
+
+  dfs_walk_once_accessible (TYPE_BINFO (target), /*friends=*/false,
+			    dfs_dcast_hint_pre, dfs_dcast_hint_post, &data);
+  return data.offset ? data.offset : ssize_int (-2);
+}
+
+/* Search for a member with name NAME in a multiple inheritance
+   lattice specified by TYPE.  If it does not exist, return NULL_TREE.
+   If the member is ambiguously referenced, return `error_mark_node'.
+   Otherwise, return a DECL with the indicated name.  If WANT_TYPE is
+   true, type declarations are preferred.  */
+
+/* Return the FUNCTION_DECL, RECORD_TYPE, UNION_TYPE, or
+   NAMESPACE_DECL corresponding to the innermost non-block scope.  */
+
+tree
+current_scope (void)
+{
+  /* There are a number of cases we need to be aware of here:
+			 current_class_type	current_function_decl
+     global			NULL			NULL
+     fn-local			NULL			SET
+     class-local		SET			NULL
+     class->fn			SET			SET
+     fn->class			SET			SET
+
+     Those last two make life interesting.  If we're in a function which is
+     itself inside a class, we need decls to go into the fn's decls (our
+     second case below).  But if we're in a class and the class itself is
+     inside a function, we need decls to go into the decls for the class.  To
+     achieve this last goal, we must see if, when both current_class_ptr and
+     current_function_decl are set, the class was declared inside that
+     function.  If so, we know to put the decls into the class's scope.  */
+  if (current_function_decl && current_class_type
+      && ((DECL_FUNCTION_MEMBER_P (current_function_decl)
+	   && same_type_p (DECL_CONTEXT (current_function_decl),
+			   current_class_type))
+	  || (DECL_FRIEND_CONTEXT (current_function_decl)
+	      && same_type_p (DECL_FRIEND_CONTEXT (current_function_decl),
+			      current_class_type))))
+    return current_function_decl;
+
+  if (current_class_type)
+    return current_class_type;
+
+  if (current_function_decl)
+    return current_function_decl;
+
+  return current_namespace;
+}
+
+/* Returns nonzero if we are currently in a function scope.  Note
+   that this function returns zero if we are within a local class, but
+   not within a member function body of the local class.  */
+
+int
+at_function_scope_p (void)
+{
+  tree cs = current_scope ();
+  /* Also check cfun to make sure that we're really compiling
+     this function (as opposed to having set current_function_decl
+     for access checking or some such).  */
+  return (cs && TREE_CODE (cs) == FUNCTION_DECL
+	  && cfun && cfun->decl == current_function_decl);
+}
+
+/* Returns true if the innermost active scope is a class scope.  */
+
+bool
+at_class_scope_p (void)
+{
+  tree cs = current_scope ();
+  return cs && TYPE_P (cs);
+}
+
+/* Returns true if the innermost active scope is a namespace scope.  */
+
+bool
+at_namespace_scope_p (void)
+{
+  tree cs = current_scope ();
+  return cs && TREE_CODE (cs) == NAMESPACE_DECL;
+}
+
+/* Return the scope of DECL, as appropriate when doing name-lookup.  */
+
+tree
+context_for_name_lookup (tree decl)
+{
+  /* [class.union]
+
+     For the purposes of name lookup, after the anonymous union
+     definition, the members of the anonymous union are considered to
+     have been defined in the scope in which the anonymous union is
+     declared.  */
+  tree context = DECL_CONTEXT (decl);
+
+  while (context && TYPE_P (context)
+	 && (ANON_AGGR_TYPE_P (context) || UNSCOPED_ENUM_P (context)))
+    context = TYPE_CONTEXT (context);
+  if (!context)
+    context = global_namespace;
+
+  return context;
+}
+
+/* Returns true iff DECL is declared in TYPE.  */
+
+static bool
+member_declared_in_type (tree decl, tree type)
+{
+  /* A normal declaration obviously counts.  */
+  if (context_for_name_lookup (decl) == type)
+    return true;
+  /* So does a using or access declaration.  */
+  if (DECL_LANG_SPECIFIC (decl) && !DECL_DISCRIMINATOR_P (decl)
+      && purpose_member (type, DECL_ACCESS (decl)))
+    return true;
+  return false;
+}
+
+/* The accessibility routines use BINFO_ACCESS for scratch space
+   during the computation of the accessibility of some declaration.  */
+
+/* Avoid walking up past a declaration of the member.  */
+
+static tree
+dfs_access_in_type_pre (tree binfo, void *data)
+{
+  tree decl = (tree) data;
+  tree type = BINFO_TYPE (binfo);
+  if (member_declared_in_type (decl, type))
+    return dfs_skip_bases;
+  return NULL_TREE;
+}
+
+#define BINFO_ACCESS(NODE) \
+  ((access_kind) ((TREE_PUBLIC (NODE) << 1) | TREE_PRIVATE (NODE)))
+
+/* Set the access associated with NODE to ACCESS.  */
+
+#define SET_BINFO_ACCESS(NODE, ACCESS)			\
+  ((TREE_PUBLIC (NODE) = ((ACCESS) & 2) != 0),	\
+   (TREE_PRIVATE (NODE) = ((ACCESS) & 1) != 0))
+
+/* Called from access_in_type via dfs_walk.  Calculate the access to
+   DATA (which is really a DECL) in BINFO.  */
+
+static tree
+dfs_access_in_type (tree binfo, void *data)
+{
+  tree decl = (tree) data;
+  tree type = BINFO_TYPE (binfo);
+  access_kind access = ak_none;
+
+  if (context_for_name_lookup (decl) == type)
+    {
+      /* If we have descended to the scope of DECL, just note the
+	 appropriate access.  */
+      if (TREE_PRIVATE (decl))
+	access = ak_private;
+      else if (TREE_PROTECTED (decl))
+	access = ak_protected;
+      else
+	access = ak_public;
+    }
+  else
+    {
+      /* First, check for an access-declaration that gives us more
+	 access to the DECL.  */
+      if (DECL_LANG_SPECIFIC (decl) && !DECL_DISCRIMINATOR_P (decl))
+	{
+	  tree decl_access = purpose_member (type, DECL_ACCESS (decl));
+
+	  if (decl_access)
+	    {
+	      decl_access = TREE_VALUE (decl_access);
+
+	      if (decl_access == access_public_node)
+		access = ak_public;
+	      else if (decl_access == access_protected_node)
+		access = ak_protected;
+	      else if (decl_access == access_private_node)
+		access = ak_private;
+	      else
+		gcc_unreachable ();
+	    }
+	}
+
+      if (!access)
+	{
+	  int i;
+	  tree base_binfo;
+	  vec<tree, va_gc> *accesses;
+
+	  /* Otherwise, scan our baseclasses, and pick the most favorable
+	     access.  */
+	  accesses = BINFO_BASE_ACCESSES (binfo);
+	  for (i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
+	    {
+	      tree base_access = (*accesses)[i];
+	      access_kind base_access_now = BINFO_ACCESS (base_binfo);
+
+	      if (base_access_now == ak_none || base_access_now == ak_private)
+		/* If it was not accessible in the base, or only
+		   accessible as a private member, we can't access it
+		   all.  */
+		base_access_now = ak_none;
+	      else if (base_access == access_protected_node)
+		/* Public and protected members in the base become
+		   protected here.  */
+		base_access_now = ak_protected;
+	      else if (base_access == access_private_node)
+		/* Public and protected members in the base become
+		   private here.  */
+		base_access_now = ak_private;
+
+	      /* See if the new access, via this base, gives more
+		 access than our previous best access.  */
+	      if (base_access_now != ak_none
+		  && (access == ak_none || base_access_now < access))
+		{
+		  access = base_access_now;
+
+		  /* If the new access is public, we can't do better.  */
+		  if (access == ak_public)
+		    break;
+		}
+	    }
+	}
+    }
+
+  /* Note the access to DECL in TYPE.  */
+  SET_BINFO_ACCESS (binfo, access);
+
+  return NULL_TREE;
+}
+
+/* Return the access to DECL in TYPE.  */
+
+static access_kind
+access_in_type (tree type, tree decl)
+{
+  tree binfo = TYPE_BINFO (type);
+
+  /* We must take into account
+
+       [class.paths]
+
+       If a name can be reached by several paths through a multiple
+       inheritance graph, the access is that of the path that gives
+       most access.
+
+    The algorithm we use is to make a post-order depth-first traversal
+    of the base-class hierarchy.  As we come up the tree, we annotate
+    each node with the most lenient access.  */
+  dfs_walk_once (binfo, dfs_access_in_type_pre, dfs_access_in_type, decl);
+
+  return BINFO_ACCESS (binfo);
+}
+
+/* Returns nonzero if it is OK to access DECL named in TYPE through an object
+   of OTYPE in the context of DERIVED.  */
+
+static int
+protected_accessible_p (tree decl, tree derived, tree type, tree otype)
+{
+  /* We're checking this clause from [class.access.base]
+
+       m as a member of N is protected, and the reference occurs in a
+       member or friend of class N, or in a member or friend of a
+       class P derived from N, where m as a member of P is public, private
+       or protected.
+
+    Here DERIVED is a possible P, DECL is m and TYPE is N.  */
+
+  /* If DERIVED isn't derived from N, then it can't be a P.  */
+  if (!DERIVED_FROM_P (type, derived))
+    return 0;
+
+  /* [class.protected]
+
+     When a friend or a member function of a derived class references
+     a protected nonstatic member of a base class, an access check
+     applies in addition to those described earlier in clause
+     _class.access_) Except when forming a pointer to member
+     (_expr.unary.op_), the access must be through a pointer to,
+     reference to, or object of the derived class itself (or any class
+     derived from that class) (_expr.ref_).  If the access is to form
+     a pointer to member, the nested-name-specifier shall name the
+     derived class (or any class derived from that class).  */
+  if (DECL_NONSTATIC_MEMBER_P (decl)
+      && !DERIVED_FROM_P (derived, otype))
+    return 0;
+
+  return 1;
+}
+
+/* Returns nonzero if SCOPE is a type or a friend of a type which would be able
+   to access DECL through TYPE.  OTYPE is the type of the object.  */
+
+static int
+friend_accessible_p (tree scope, tree decl, tree type, tree otype)
+{
+  /* We're checking this clause from [class.access.base]
+
+       m as a member of N is protected, and the reference occurs in a
+       member or friend of class N, or in a member or friend of a
+       class P derived from N, where m as a member of P is public, private
+       or protected.
+
+    Here DECL is m and TYPE is N.  SCOPE is the current context,
+    and we check all its possible Ps.  */
+  tree befriending_classes;
+  tree t;
+
+  if (!scope)
+    return 0;
+
+  if (is_global_friend (scope))
+    return 1;
+
+  /* Is SCOPE itself a suitable P?  */
+  if (TYPE_P (scope) && protected_accessible_p (decl, scope, type, otype))
+    return 1;
+
+  if (DECL_DECLARES_FUNCTION_P (scope))
+    befriending_classes = DECL_BEFRIENDING_CLASSES (scope);
+  else if (TYPE_P (scope))
+    befriending_classes = CLASSTYPE_BEFRIENDING_CLASSES (scope);
+  else
+    return 0;
+
+  for (t = befriending_classes; t; t = TREE_CHAIN (t))
+    if (protected_accessible_p (decl, TREE_VALUE (t), type, otype))
+      return 1;
+
+  /* Nested classes have the same access as their enclosing types, as
+     per DR 45 (this is a change from C++98).  */
+  if (TYPE_P (scope))
+    if (friend_accessible_p (TYPE_CONTEXT (scope), decl, type, otype))
+      return 1;
+
+  if (DECL_DECLARES_FUNCTION_P (scope))
+    {
+      /* Perhaps this SCOPE is a member of a class which is a
+	 friend.  */
+      if (DECL_CLASS_SCOPE_P (scope)
+	  && friend_accessible_p (DECL_CONTEXT (scope), decl, type, otype))
+	return 1;
+    }
+
+  /* Maybe scope's template is a friend.  */
+  if (tree tinfo = get_template_info (scope))
+    {
+      tree tmpl = TI_TEMPLATE (tinfo);
+      if (DECL_CLASS_TEMPLATE_P (tmpl))
+	tmpl = TREE_TYPE (tmpl);
+      else
+	tmpl = DECL_TEMPLATE_RESULT (tmpl);
+      if (tmpl != scope)
+	{
+	  /* Increment processing_template_decl to make sure that
+	     dependent_type_p works correctly.  */
+	  ++processing_template_decl;
+	  int ret = friend_accessible_p (tmpl, decl, type, otype);
+	  --processing_template_decl;
+	  if (ret)
+	    return 1;
+	}
+    }
+
+  /* If is_friend is true, we should have found a befriending class.  */
+  gcc_checking_assert (!is_friend (type, scope));
+
+  return 0;
+}
+
+struct dfs_accessible_data
+{
+  tree decl;
+  tree object_type;
+};
+
+/* Avoid walking up past a declaration of the member.  */
+
+static tree
+dfs_accessible_pre (tree binfo, void *data)
+{
+  dfs_accessible_data *d = (dfs_accessible_data *)data;
+  tree type = BINFO_TYPE (binfo);
+  if (member_declared_in_type (d->decl, type))
+    return dfs_skip_bases;
+  return NULL_TREE;
+}
+
+/* Called via dfs_walk_once_accessible from accessible_p */
+
+static tree
+dfs_accessible_post (tree binfo, void *data)
+{
+  /* access_in_type already set BINFO_ACCESS for us.  */
+  access_kind access = BINFO_ACCESS (binfo);
+  tree N = BINFO_TYPE (binfo);
+  dfs_accessible_data *d = (dfs_accessible_data *)data;
+  tree decl = d->decl;
+  tree scope = current_nonlambda_scope ();
+
+  /* A member m is accessible at the point R when named in class N if */
+  switch (access)
+    {
+    case ak_none:
+      return NULL_TREE;
+
+    case ak_public:
+      /* m as a member of N is public, or */
+      return binfo;
+
+    case ak_private:
+      {
+	/* m as a member of N is private, and R occurs in a member or friend of
+	   class N, or */
+	if (scope && TREE_CODE (scope) != NAMESPACE_DECL
+	    && is_friend (N, scope))
+	  return binfo;
+	return NULL_TREE;
+      }
+
+    case ak_protected:
+      {
+	/* m as a member of N is protected, and R occurs in a member or friend
+	   of class N, or in a member or friend of a class P derived from N,
+	   where m as a member of P is public, private, or protected  */
+	if (friend_accessible_p (scope, decl, N, d->object_type))
+	  return binfo;
+	return NULL_TREE;
+      }
+
+    default:
+      gcc_unreachable ();
+    }
+}
+
+/* Like accessible_p below, but within a template returns true iff DECL is
+   accessible in TYPE to all possible instantiations of the template.  */
+
+int
+accessible_in_template_p (tree type, tree decl)
+{
+  int save_ptd = processing_template_decl;
+  processing_template_decl = 0;
+  int val = accessible_p (type, decl, false);
+  processing_template_decl = save_ptd;
+  return val;
+}
+
+/* DECL is a declaration from a base class of TYPE, which was the
+   class used to name DECL.  Return nonzero if, in the current
+   context, DECL is accessible.  If TYPE is actually a BINFO node,
+   then we can tell in what context the access is occurring by looking
+   at the most derived class along the path indicated by BINFO.  If
+   CONSIDER_LOCAL is true, do consider special access the current
+   scope or friendship thereof we might have.  */
+
+int
+accessible_p (tree type, tree decl, bool consider_local_p)
+{
+  tree binfo;
+  access_kind access;
+
+  /* If this declaration is in a block or namespace scope, there's no
+     access control.  */
+  if (!TYPE_P (context_for_name_lookup (decl)))
+    return 1;
+
+  /* There is no need to perform access checks inside a thunk.  */
+  if (current_function_decl && DECL_THUNK_P (current_function_decl))
+    return 1;
+
+  /* In a template declaration, we cannot be sure whether the
+     particular specialization that is instantiated will be a friend
+     or not.  Therefore, all access checks are deferred until
+     instantiation.  However, PROCESSING_TEMPLATE_DECL is set in the
+     parameter list for a template (because we may see dependent types
+     in default arguments for template parameters), and access
+     checking should be performed in the outermost parameter list.  */
+  if (processing_template_decl
+      && !expanding_concept ()
+      && (!processing_template_parmlist || processing_template_decl > 1))
+    return 1;
+
+  tree otype = NULL_TREE;
+  if (!TYPE_P (type))
+    {
+      /* When accessing a non-static member, the most derived type in the
+	 binfo chain is the type of the object; remember that type for
+	 protected_accessible_p.  */
+      for (tree b = type; b; b = BINFO_INHERITANCE_CHAIN (b))
+	otype = BINFO_TYPE (b);
+      type = BINFO_TYPE (type);
+    }
+  else
+    otype = type;
+
+  /* [class.access.base]
+
+     A member m is accessible when named in class N if
+
+     --m as a member of N is public, or
+
+     --m as a member of N is private, and the reference occurs in a
+       member or friend of class N, or
+
+     --m as a member of N is protected, and the reference occurs in a
+       member or friend of class N, or in a member or friend of a
+       class P derived from N, where m as a member of P is public, private or
+       protected, or
+
+     --there exists a base class B of N that is accessible at the point
+       of reference, and m is accessible when named in class B.
+
+    We walk the base class hierarchy, checking these conditions.  */
+
+  /* We walk using TYPE_BINFO (type) because access_in_type will set
+     BINFO_ACCESS on it and its bases.  */
+  binfo = TYPE_BINFO (type);
+
+  /* Compute the accessibility of DECL in the class hierarchy
+     dominated by type.  */
+  access = access_in_type (type, decl);
+  if (access == ak_public)
+    return 1;
+
+  /* If we aren't considering the point of reference, only the first bullet
+     applies.  */
+  if (!consider_local_p)
+    return 0;
+
+  dfs_accessible_data d = { decl, otype };
+
+  /* Walk the hierarchy again, looking for a base class that allows
+     access.  */
+  return dfs_walk_once_accessible (binfo, /*friends=*/true,
+				   dfs_accessible_pre,
+				   dfs_accessible_post, &d)
+    != NULL_TREE;
+}
+
+struct lookup_field_info {
+  /* The type in which we're looking.  */
+  tree type;
+  /* The name of the field for which we're looking.  */
+  tree name;
+  /* If non-NULL, the current result of the lookup.  */
+  tree rval;
+  /* The path to RVAL.  */
+  tree rval_binfo;
+  /* If non-NULL, the lookup was ambiguous, and this is a list of the
+     candidates.  */
+  tree ambiguous;
+  /* If nonzero, we are looking for types, not data members.  */
+  int want_type;
+  /* If something went wrong, a message indicating what.  */
+  const char *errstr;
+};
+
+/* Nonzero for a class member means that it is shared between all objects
+   of that class.
+
+   [class.member.lookup]:If the resulting set of declarations are not all
+   from sub-objects of the same type, or the set has a  nonstatic  member
+   and  includes members from distinct sub-objects, there is an ambiguity
+   and the program is ill-formed.
+
+   This function checks that T contains no nonstatic members.  */
+
+int
+shared_member_p (tree t)
+{
+  if (VAR_P (t) || TREE_CODE (t) == TYPE_DECL \
+      || TREE_CODE (t) == CONST_DECL)
+    return 1;
+  if (is_overloaded_fn (t))
+    {
+      for (ovl_iterator iter (get_fns (t)); iter; ++iter)
+	if (DECL_NONSTATIC_MEMBER_FUNCTION_P (*iter))
+	  return 0;
+      return 1;
+    }
+  return 0;
+}
+
+/* Routine to see if the sub-object denoted by the binfo PARENT can be
+   found as a base class and sub-object of the object denoted by
+   BINFO.  */
+
+static int
+is_subobject_of_p (tree parent, tree binfo)
+{
+  tree probe;
+
+  for (probe = parent; probe; probe = BINFO_INHERITANCE_CHAIN (probe))
+    {
+      if (probe == binfo)
+	return 1;
+      if (BINFO_VIRTUAL_P (probe))
+	return (binfo_for_vbase (BINFO_TYPE (probe), BINFO_TYPE (binfo))
+		!= NULL_TREE);
+    }
+  return 0;
+}
+
+/* DATA is really a struct lookup_field_info.  Look for a field with
+   the name indicated there in BINFO.  If this function returns a
+   non-NULL value it is the result of the lookup.  Called from
+   lookup_field via breadth_first_search.  */
+
+static tree
+lookup_field_r (tree binfo, void *data)
+{
+  struct lookup_field_info *lfi = (struct lookup_field_info *) data;
+  tree type = BINFO_TYPE (binfo);
+  tree nval = NULL_TREE;
+
+  /* If this is a dependent base, don't look in it.  */
+  if (BINFO_DEPENDENT_BASE_P (binfo))
+    return NULL_TREE;
+
+  /* If this base class is hidden by the best-known value so far, we
+     don't need to look.  */
+  if (lfi->rval_binfo && BINFO_INHERITANCE_CHAIN (binfo) == lfi->rval_binfo
+      && !BINFO_VIRTUAL_P (binfo))
+    return dfs_skip_bases;
+
+  nval = get_class_binding (type, lfi->name, lfi->want_type);
+
+  /* If we're looking up a type (as with an elaborated type specifier)
+     we ignore all non-types we find.  */
+  if (lfi->want_type && nval && !DECL_DECLARES_TYPE_P (nval))
+    {
+      nval = NULL_TREE;
+      if (CLASSTYPE_NESTED_UTDS (type))
+	if (binding_entry e = binding_table_find (CLASSTYPE_NESTED_UTDS (type),
+						  lfi->name))
+	  nval = TYPE_MAIN_DECL (e->type);
+    }
+
+  /* If there is no declaration with the indicated name in this type,
+     then there's nothing to do.  */
+  if (!nval)
+    goto done;
+
+  /* If the lookup already found a match, and the new value doesn't
+     hide the old one, we might have an ambiguity.  */
+  if (lfi->rval_binfo
+      && !is_subobject_of_p (lfi->rval_binfo, binfo))
+
+    {
+      if (nval == lfi->rval && shared_member_p (nval))
+	/* The two things are really the same.  */
+	;
+      else if (is_subobject_of_p (binfo, lfi->rval_binfo))
+	/* The previous value hides the new one.  */
+	;
+      else
+	{
+	  /* We have a real ambiguity.  We keep a chain of all the
+	     candidates.  */
+	  if (!lfi->ambiguous && lfi->rval)
+	    {
+	      /* This is the first time we noticed an ambiguity.  Add
+		 what we previously thought was a reasonable candidate
+		 to the list.  */
+	      lfi->ambiguous = tree_cons (NULL_TREE, lfi->rval, NULL_TREE);
+	      TREE_TYPE (lfi->ambiguous) = error_mark_node;
+	    }
+
+	  /* Add the new value.  */
+	  lfi->ambiguous = tree_cons (NULL_TREE, nval, lfi->ambiguous);
+	  TREE_TYPE (lfi->ambiguous) = error_mark_node;
+	  lfi->errstr = G_("request for member %qD is ambiguous");
+	}
+    }
+  else
+    {
+      lfi->rval = nval;
+      lfi->rval_binfo = binfo;
+    }
+
+ done:
+  /* Don't look for constructors or destructors in base classes.  */
+  if (IDENTIFIER_CDTOR_P (lfi->name))
+    return dfs_skip_bases;
+  return NULL_TREE;
+}
+
+/* Return a "baselink" with BASELINK_BINFO, BASELINK_ACCESS_BINFO,
+   BASELINK_FUNCTIONS, and BASELINK_OPTYPE set to BINFO, ACCESS_BINFO,
+   FUNCTIONS, and OPTYPE respectively.  */
+
+tree
+build_baselink (tree binfo, tree access_binfo, tree functions, tree optype)
+{
+  tree baselink;
+
+  gcc_assert (TREE_CODE (functions) == FUNCTION_DECL
+	      || TREE_CODE (functions) == TEMPLATE_DECL
+	      || TREE_CODE (functions) == TEMPLATE_ID_EXPR
+	      || TREE_CODE (functions) == OVERLOAD);
+  gcc_assert (!optype || TYPE_P (optype));
+  gcc_assert (TREE_TYPE (functions));
+
+  baselink = make_node (BASELINK);
+  TREE_TYPE (baselink) = TREE_TYPE (functions);
+  BASELINK_BINFO (baselink) = binfo;
+  BASELINK_ACCESS_BINFO (baselink) = access_binfo;
+  BASELINK_FUNCTIONS (baselink) = functions;
+  BASELINK_OPTYPE (baselink) = optype;
+
+  return baselink;
+}
+
+/* Look for a member named NAME in an inheritance lattice dominated by
+   XBASETYPE.  If PROTECT is 0 or two, we do not check access.  If it
+   is 1, we enforce accessibility.  If PROTECT is zero, then, for an
+   ambiguous lookup, we return NULL.  If PROTECT is 1, we issue error
+   messages about inaccessible or ambiguous lookup.  If PROTECT is 2,
+   we return a TREE_LIST whose TREE_TYPE is error_mark_node and whose
+   TREE_VALUEs are the list of ambiguous candidates.
+
+   WANT_TYPE is 1 when we should only return TYPE_DECLs.
+
+   If nothing can be found return NULL_TREE and do not issue an error.
+
+   If non-NULL, failure information is written back to AFI.  */
+
+tree
+lookup_member (tree xbasetype, tree name, int protect, bool want_type,
+	       tsubst_flags_t complain, access_failure_info *afi)
+{
+  tree rval, rval_binfo = NULL_TREE;
+  tree type = NULL_TREE, basetype_path = NULL_TREE;
+  struct lookup_field_info lfi;
+
+  /* rval_binfo is the binfo associated with the found member, note,
+     this can be set with useful information, even when rval is not
+     set, because it must deal with ALL members, not just non-function
+     members.  It is used for ambiguity checking and the hidden
+     checks.  Whereas rval is only set if a proper (not hidden)
+     non-function member is found.  */
+
+  const char *errstr = 0;
+
+  if (name == error_mark_node
+      || xbasetype == NULL_TREE
+      || xbasetype == error_mark_node)
+    return NULL_TREE;
+
+  gcc_assert (identifier_p (name));
+
+  if (TREE_CODE (xbasetype) == TREE_BINFO)
+    {
+      type = BINFO_TYPE (xbasetype);
+      basetype_path = xbasetype;
+    }
+  else
+    {
+      if (!RECORD_OR_UNION_CODE_P (TREE_CODE (xbasetype)))
+	return NULL_TREE;
+      type = xbasetype;
+      xbasetype = NULL_TREE;
+    }
+
+  type = complete_type (type);
+
+  /* Make sure we're looking for a member of the current instantiation in the
+     right partial specialization.  */
+  if (flag_concepts && dependent_type_p (type))
+    if (tree t = currently_open_class (type))
+      type = t;
+
+  if (!basetype_path)
+    basetype_path = TYPE_BINFO (type);
+
+  if (!basetype_path)
+    return NULL_TREE;
+
+  memset (&lfi, 0, sizeof (lfi));
+  lfi.type = type;
+  lfi.name = name;
+  lfi.want_type = want_type;
+  dfs_walk_all (basetype_path, &lookup_field_r, NULL, &lfi);
+  rval = lfi.rval;
+  rval_binfo = lfi.rval_binfo;
+  if (rval_binfo)
+    type = BINFO_TYPE (rval_binfo);
+  errstr = lfi.errstr;
+
+  /* If we are not interested in ambiguities, don't report them;
+     just return NULL_TREE.  */
+  if (!protect && lfi.ambiguous)
+    return NULL_TREE;
+
+  if (protect == 2)
+    {
+      if (lfi.ambiguous)
+	return lfi.ambiguous;
+      else
+	protect = 0;
+    }
+
+  /* [class.access]
+
+     In the case of overloaded function names, access control is
+     applied to the function selected by overloaded resolution.  
+
+     We cannot check here, even if RVAL is only a single non-static
+     member function, since we do not know what the "this" pointer
+     will be.  For:
+
+        class A { protected: void f(); };
+        class B : public A { 
+          void g(A *p) {
+            f(); // OK
+            p->f(); // Not OK.
+          }
+        };
+
+    only the first call to "f" is valid.  However, if the function is
+    static, we can check.  */
+  if (rval && protect 
+      && !really_overloaded_fn (rval))
+    {
+      tree decl = is_overloaded_fn (rval) ? get_first_fn (rval) : rval;
+      if (!DECL_NONSTATIC_MEMBER_FUNCTION_P (decl)
+	  && !perform_or_defer_access_check (basetype_path, decl, decl,
+					     complain, afi))
+	rval = error_mark_node;
+    }
+
+  if (errstr && protect)
+    {
+      if (complain & tf_error)
+	{
+	  error (errstr, name, type);
+	  if (lfi.ambiguous)
+	    print_candidates (lfi.ambiguous);
+	}
+      rval = error_mark_node;
+    }
+
+  if (rval && is_overloaded_fn (rval))
+    rval = build_baselink (rval_binfo, basetype_path, rval,
+			   (IDENTIFIER_CONV_OP_P (name)
+			   ? TREE_TYPE (name): NULL_TREE));
+  return rval;
+}
+
+/* Helper class for lookup_member_fuzzy.  */
+
+class lookup_field_fuzzy_info
+{
+ public:
+  lookup_field_fuzzy_info (bool want_type_p) :
+    m_want_type_p (want_type_p), m_candidates () {}
+
+  void fuzzy_lookup_field (tree type);
+
+  /* If true, we are looking for types, not data members.  */
+  bool m_want_type_p;
+  /* The result: a vec of identifiers.  */
+  auto_vec<tree> m_candidates;
+};
+
+/* Locate all fields within TYPE, append them to m_candidates.  */
+
+void
+lookup_field_fuzzy_info::fuzzy_lookup_field (tree type)
+{
+  if (!CLASS_TYPE_P (type))
+    return;
+
+  for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
+    {
+      if (!m_want_type_p || DECL_DECLARES_TYPE_P (field))
+	if (DECL_NAME (field))
+	  m_candidates.safe_push (DECL_NAME (field));
+    }
+}
+
+
+/* Helper function for lookup_member_fuzzy, called via dfs_walk_all
+   DATA is really a lookup_field_fuzzy_info.  Look for a field with
+   the name indicated there in BINFO.  Gathers pertinent identifiers into
+   m_candidates.  */
+
+static tree
+lookup_field_fuzzy_r (tree binfo, void *data)
+{
+  lookup_field_fuzzy_info *lffi = (lookup_field_fuzzy_info *) data;
+  tree type = BINFO_TYPE (binfo);
+
+  lffi->fuzzy_lookup_field (type);
+
+  return NULL_TREE;
+}
+
+/* Like lookup_member, but try to find the closest match for NAME,
+   rather than an exact match, and return an identifier (or NULL_TREE).
+   Do not complain.  */
+
+tree
+lookup_member_fuzzy (tree xbasetype, tree name, bool want_type_p)
+{
+  tree type = NULL_TREE, basetype_path = NULL_TREE;
+  struct lookup_field_fuzzy_info lffi (want_type_p);
+
+  /* rval_binfo is the binfo associated with the found member, note,
+     this can be set with useful information, even when rval is not
+     set, because it must deal with ALL members, not just non-function
+     members.  It is used for ambiguity checking and the hidden
+     checks.  Whereas rval is only set if a proper (not hidden)
+     non-function member is found.  */
+
+  if (name == error_mark_node
+      || xbasetype == NULL_TREE
+      || xbasetype == error_mark_node)
+    return NULL_TREE;
+
+  gcc_assert (identifier_p (name));
+
+  if (TREE_CODE (xbasetype) == TREE_BINFO)
+    {
+      type = BINFO_TYPE (xbasetype);
+      basetype_path = xbasetype;
+    }
+  else
+    {
+      if (!RECORD_OR_UNION_CODE_P (TREE_CODE (xbasetype)))
+	return NULL_TREE;
+      type = xbasetype;
+      xbasetype = NULL_TREE;
+    }
+
+  type = complete_type (type);
+
+  /* Make sure we're looking for a member of the current instantiation in the
+     right partial specialization.  */
+  if (flag_concepts && dependent_type_p (type))
+    type = currently_open_class (type);
+
+  if (!basetype_path)
+    basetype_path = TYPE_BINFO (type);
+
+  if (!basetype_path)
+    return NULL_TREE;
+
+  /* Populate lffi.m_candidates.  */
+  dfs_walk_all (basetype_path, &lookup_field_fuzzy_r, NULL, &lffi);
+
+  return find_closest_identifier (name, &lffi.m_candidates);
+}
+
+/* Like lookup_member, except that if we find a function member we
+   return NULL_TREE.  */
+
+tree
+lookup_field (tree xbasetype, tree name, int protect, bool want_type)
+{
+  tree rval = lookup_member (xbasetype, name, protect, want_type,
+			     tf_warning_or_error);
+
+  /* Ignore functions, but propagate the ambiguity list.  */
+  if (!error_operand_p (rval)
+      && (rval && BASELINK_P (rval)))
+    return NULL_TREE;
+
+  return rval;
+}
+
+/* Like lookup_member, except that if we find a non-function member we
+   return NULL_TREE.  */
+
+tree
+lookup_fnfields (tree xbasetype, tree name, int protect)
+{
+  tree rval = lookup_member (xbasetype, name, protect, /*want_type=*/false,
+			     tf_warning_or_error);
+
+  /* Ignore non-functions, but propagate the ambiguity list.  */
+  if (!error_operand_p (rval)
+      && (rval && !BASELINK_P (rval)))
+    return NULL_TREE;
+
+  return rval;
+}
+
+/* DECL is the result of a qualified name lookup.  QUALIFYING_SCOPE is
+   the class or namespace used to qualify the name.  CONTEXT_CLASS is
+   the class corresponding to the object in which DECL will be used.
+   Return a possibly modified version of DECL that takes into account
+   the CONTEXT_CLASS.
+
+   In particular, consider an expression like `B::m' in the context of
+   a derived class `D'.  If `B::m' has been resolved to a BASELINK,
+   then the most derived class indicated by the BASELINK_BINFO will be
+   `B', not `D'.  This function makes that adjustment.  */
+
+tree
+adjust_result_of_qualified_name_lookup (tree decl,
+					tree qualifying_scope,
+					tree context_class)
+{
+  if (context_class && context_class != error_mark_node
+      && CLASS_TYPE_P (context_class)
+      && CLASS_TYPE_P (qualifying_scope)
+      && DERIVED_FROM_P (qualifying_scope, context_class)
+      && BASELINK_P (decl))
+    {
+      tree base;
+
+      /* Look for the QUALIFYING_SCOPE as a base of the CONTEXT_CLASS.
+	 Because we do not yet know which function will be chosen by
+	 overload resolution, we cannot yet check either accessibility
+	 or ambiguity -- in either case, the choice of a static member
+	 function might make the usage valid.  */
+      base = lookup_base (context_class, qualifying_scope,
+			  ba_unique, NULL, tf_none);
+      if (base && base != error_mark_node)
+	{
+	  BASELINK_ACCESS_BINFO (decl) = base;
+	  tree decl_binfo
+	    = lookup_base (base, BINFO_TYPE (BASELINK_BINFO (decl)),
+			   ba_unique, NULL, tf_none);
+	  if (decl_binfo && decl_binfo != error_mark_node)
+	    BASELINK_BINFO (decl) = decl_binfo;
+	}
+    }
+
+  if (BASELINK_P (decl))
+    BASELINK_QUALIFIED_P (decl) = true;
+
+  return decl;
+}
+
+
+/* Walk the class hierarchy within BINFO, in a depth-first traversal.
+   PRE_FN is called in preorder, while POST_FN is called in postorder.
+   If PRE_FN returns DFS_SKIP_BASES, child binfos will not be
+   walked.  If PRE_FN or POST_FN returns a different non-NULL value,
+   that value is immediately returned and the walk is terminated.  One
+   of PRE_FN and POST_FN can be NULL.  At each node, PRE_FN and
+   POST_FN are passed the binfo to examine and the caller's DATA
+   value.  All paths are walked, thus virtual and morally virtual
+   binfos can be multiply walked.  */
+
+tree
+dfs_walk_all (tree binfo, tree (*pre_fn) (tree, void *),
+	      tree (*post_fn) (tree, void *), void *data)
+{
+  tree rval;
+  unsigned ix;
+  tree base_binfo;
+
+  /* Call the pre-order walking function.  */
+  if (pre_fn)
+    {
+      rval = pre_fn (binfo, data);
+      if (rval)
+	{
+	  if (rval == dfs_skip_bases)
+	    goto skip_bases;
+	  return rval;
+	}
+    }
+
+  /* Find the next child binfo to walk.  */
+  for (ix = 0; BINFO_BASE_ITERATE (binfo, ix, base_binfo); ix++)
+    {
+      rval = dfs_walk_all (base_binfo, pre_fn, post_fn, data);
+      if (rval)
+	return rval;
+    }
+
+ skip_bases:
+  /* Call the post-order walking function.  */
+  if (post_fn)
+    {
+      rval = post_fn (binfo, data);
+      gcc_assert (rval != dfs_skip_bases);
+      return rval;
+    }
+
+  return NULL_TREE;
+}
+
+/* Worker for dfs_walk_once.  This behaves as dfs_walk_all, except
+   that binfos are walked at most once.  */
+
+static tree
+dfs_walk_once_r (tree binfo, tree (*pre_fn) (tree, void *),
+		 tree (*post_fn) (tree, void *), hash_set<tree> *pset,
+		 void *data)
+{
+  tree rval;
+  unsigned ix;
+  tree base_binfo;
+
+  /* Call the pre-order walking function.  */
+  if (pre_fn)
+    {
+      rval = pre_fn (binfo, data);
+      if (rval)
+	{
+	  if (rval == dfs_skip_bases)
+	    goto skip_bases;
+
+	  return rval;
+	}
+    }
+
+  /* Find the next child binfo to walk.  */
+  for (ix = 0; BINFO_BASE_ITERATE (binfo, ix, base_binfo); ix++)
+    {
+      if (BINFO_VIRTUAL_P (base_binfo))
+	if (pset->add (base_binfo))
+	  continue;
+
+      rval = dfs_walk_once_r (base_binfo, pre_fn, post_fn, pset, data);
+      if (rval)
+	return rval;
+    }
+
+ skip_bases:
+  /* Call the post-order walking function.  */
+  if (post_fn)
+    {
+      rval = post_fn (binfo, data);
+      gcc_assert (rval != dfs_skip_bases);
+      return rval;
+    }
+
+  return NULL_TREE;
+}
+
+/* Like dfs_walk_all, except that binfos are not multiply walked.  For
+   non-diamond shaped hierarchies this is the same as dfs_walk_all.
+   For diamond shaped hierarchies we must mark the virtual bases, to
+   avoid multiple walks.  */
+
+tree
+dfs_walk_once (tree binfo, tree (*pre_fn) (tree, void *),
+	       tree (*post_fn) (tree, void *), void *data)
+{
+  static int active = 0;  /* We must not be called recursively. */
+  tree rval;
+
+  gcc_assert (pre_fn || post_fn);
+  gcc_assert (!active);
+  active++;
+
+  if (!CLASSTYPE_DIAMOND_SHAPED_P (BINFO_TYPE (binfo)))
+    /* We are not diamond shaped, and therefore cannot encounter the
+       same binfo twice.  */
+    rval = dfs_walk_all (binfo, pre_fn, post_fn, data);
+  else
+    {
+      hash_set<tree> pset;
+      rval = dfs_walk_once_r (binfo, pre_fn, post_fn, &pset, data);
+    }
+
+  active--;
+
+  return rval;
+}
+
+/* Worker function for dfs_walk_once_accessible.  Behaves like
+   dfs_walk_once_r, except (a) FRIENDS_P is true if special
+   access given by the current context should be considered, (b) ONCE
+   indicates whether bases should be marked during traversal.  */
+
+static tree
+dfs_walk_once_accessible_r (tree binfo, bool friends_p, hash_set<tree> *pset,
+			    tree (*pre_fn) (tree, void *),
+			    tree (*post_fn) (tree, void *), void *data)
+{
+  tree rval = NULL_TREE;
+  unsigned ix;
+  tree base_binfo;
+
+  /* Call the pre-order walking function.  */
+  if (pre_fn)
+    {
+      rval = pre_fn (binfo, data);
+      if (rval)
+	{
+	  if (rval == dfs_skip_bases)
+	    goto skip_bases;
+
+	  return rval;
+	}
+    }
+
+  /* Find the next child binfo to walk.  */
+  for (ix = 0; BINFO_BASE_ITERATE (binfo, ix, base_binfo); ix++)
+    {
+      bool mark = pset && BINFO_VIRTUAL_P (base_binfo);
+
+      if (mark && pset->contains (base_binfo))
+	continue;
+
+      /* If the base is inherited via private or protected
+	 inheritance, then we can't see it, unless we are a friend of
+	 the current binfo.  */
+      if (BINFO_BASE_ACCESS (binfo, ix) != access_public_node)
+	{
+	  tree scope;
+	  if (!friends_p)
+	    continue;
+	  scope = current_scope ();
+	  if (!scope
+	      || TREE_CODE (scope) == NAMESPACE_DECL
+	      || !is_friend (BINFO_TYPE (binfo), scope))
+	    continue;
+	}
+
+      if (mark)
+	pset->add (base_binfo);
+
+      rval = dfs_walk_once_accessible_r (base_binfo, friends_p, pset,
+					 pre_fn, post_fn, data);
+      if (rval)
+	return rval;
+    }
+
+ skip_bases:
+  /* Call the post-order walking function.  */
+  if (post_fn)
+    {
+      rval = post_fn (binfo, data);
+      gcc_assert (rval != dfs_skip_bases);
+      return rval;
+    }
+
+  return NULL_TREE;
+}
+
+/* Like dfs_walk_once except that only accessible bases are walked.
+   FRIENDS_P indicates whether friendship of the local context
+   should be considered when determining accessibility.  */
+
+static tree
+dfs_walk_once_accessible (tree binfo, bool friends_p,
+			    tree (*pre_fn) (tree, void *),
+			    tree (*post_fn) (tree, void *), void *data)
+{
+  hash_set<tree> *pset = NULL;
+  if (CLASSTYPE_DIAMOND_SHAPED_P (BINFO_TYPE (binfo)))
+    pset = new hash_set<tree>;
+  tree rval = dfs_walk_once_accessible_r (binfo, friends_p, pset,
+					  pre_fn, post_fn, data);
+
+  if (pset)
+    delete pset;
+  return rval;
+}
+
+/* Return true iff the code of T is CODE, and it has compatible
+   type with TYPE.  */
+
+static bool
+matches_code_and_type_p (tree t, enum tree_code code, tree type)
+{
+  if (TREE_CODE (t) != code)
+    return false;
+  if (!cxx_types_compatible_p (TREE_TYPE (t), type))
+    return false;
+  return true;
+}
+
+/* Subroutine of direct_accessor_p and reference_accessor_p.
+   Determine if COMPONENT_REF is a simple field lookup of this->FIELD_DECL.
+   We expect a tree of the form:
+	     <component_ref:
+	       <indirect_ref:S>
+		 <nop_expr:P*
+		   <parm_decl (this)>
+		 <field_decl (FIELD_DECL)>>>.  */
+
+static bool
+field_access_p (tree component_ref, tree field_decl, tree field_type)
+{
+  if (!matches_code_and_type_p (component_ref, COMPONENT_REF, field_type))
+    return false;
+
+  tree indirect_ref = TREE_OPERAND (component_ref, 0);
+  if (TREE_CODE (indirect_ref) != INDIRECT_REF)
+    return false;
+
+  tree ptr = STRIP_NOPS (TREE_OPERAND (indirect_ref, 0));
+  if (!is_this_parameter (ptr))
+    return false;
+
+  /* Must access the correct field.  */
+  if (TREE_OPERAND (component_ref, 1) != field_decl)
+    return false;
+  return true;
+}
+
+/* Subroutine of field_accessor_p.
+
+   Assuming that INIT_EXPR has already had its code and type checked,
+   determine if it is a simple accessor for FIELD_DECL
+   (of type FIELD_TYPE).
+
+   Specifically, a simple accessor within struct S of the form:
+       T get_field () { return m_field; }
+   should have a DECL_SAVED_TREE of the form:
+       <return_expr
+	 <init_expr:T
+	   <result_decl:T
+	   <nop_expr:T
+	     <component_ref:
+	       <indirect_ref:S>
+		 <nop_expr:P*
+		   <parm_decl (this)>
+		 <field_decl (FIELD_DECL)>>>.  */
+
+static bool
+direct_accessor_p (tree init_expr, tree field_decl, tree field_type)
+{
+  tree result_decl = TREE_OPERAND (init_expr, 0);
+  if (!matches_code_and_type_p (result_decl, RESULT_DECL, field_type))
+    return false;
+
+  tree component_ref = STRIP_NOPS (TREE_OPERAND (init_expr, 1));
+  if (!field_access_p (component_ref, field_decl, field_type))
+    return false;
+
+  return true;
+}
+
+/* Subroutine of field_accessor_p.
+
+   Assuming that INIT_EXPR has already had its code and type checked,
+   determine if it is a "reference" accessor for FIELD_DECL
+   (of type FIELD_REFERENCE_TYPE).
+
+   Specifically, a simple accessor within struct S of the form:
+       T& get_field () { return m_field; }
+   should have a DECL_SAVED_TREE of the form:
+       <return_expr
+	 <init_expr:T&
+	   <result_decl:T&
+	   <nop_expr: T&
+	     <addr_expr: T*
+	       <component_ref:T
+		 <indirect_ref:S
+		   <nop_expr
+		     <parm_decl (this)>>
+		   <field (FIELD_DECL)>>>>>>.  */
+static bool
+reference_accessor_p (tree init_expr, tree field_decl, tree field_type,
+		      tree field_reference_type)
+{
+  tree result_decl = TREE_OPERAND (init_expr, 0);
+  if (!matches_code_and_type_p (result_decl, RESULT_DECL, field_reference_type))
+    return false;
+
+  tree field_pointer_type = build_pointer_type (field_type);
+  tree addr_expr = STRIP_NOPS (TREE_OPERAND (init_expr, 1));
+  if (!matches_code_and_type_p (addr_expr, ADDR_EXPR, field_pointer_type))
+    return false;
+
+  tree component_ref = STRIP_NOPS (TREE_OPERAND (addr_expr, 0));
+
+  if (!field_access_p (component_ref, field_decl, field_type))
+    return false;
+
+  return true;
+}
+
+/* Return true if FN is an accessor method for FIELD_DECL.
+   i.e. a method of the form { return FIELD; }, with no
+   conversions.
+
+   If CONST_P, then additionally require that FN be a const
+   method.  */
+
+static bool
+field_accessor_p (tree fn, tree field_decl, bool const_p)
+{
+  if (TREE_CODE (fn) != FUNCTION_DECL)
+    return false;
+
+  /* We don't yet support looking up static data, just fields.  */
+  if (TREE_CODE (field_decl) != FIELD_DECL)
+    return false;
+
+  tree fntype = TREE_TYPE (fn);
+  if (TREE_CODE (fntype) != METHOD_TYPE)
+    return false;
+
+  /* If the field is accessed via a const "this" argument, verify
+     that the "this" parameter is const.  */
+  if (const_p)
+    {
+      tree this_type = type_of_this_parm (fntype);
+      if (!TYPE_READONLY (this_type))
+	return false;
+    }
+
+  tree saved_tree = DECL_SAVED_TREE (fn);
+
+  if (saved_tree == NULL_TREE)
+    return false;
+
+  if (TREE_CODE (saved_tree) != RETURN_EXPR)
+    return false;
+
+  tree init_expr = TREE_OPERAND (saved_tree, 0);
+  if (TREE_CODE (init_expr) != INIT_EXPR)
+    return false;
+
+  /* Determine if this is a simple accessor within struct S of the form:
+       T get_field () { return m_field; }.  */
+   tree field_type = TREE_TYPE (field_decl);
+  if (cxx_types_compatible_p (TREE_TYPE (init_expr), field_type))
+    return direct_accessor_p (init_expr, field_decl, field_type);
+
+  /* Failing that, determine if it is an accessor of the form:
+       T& get_field () { return m_field; }.  */
+  tree field_reference_type = cp_build_reference_type (field_type, false);
+  if (cxx_types_compatible_p (TREE_TYPE (init_expr), field_reference_type))
+    return reference_accessor_p (init_expr, field_decl, field_type,
+				 field_reference_type);
+
+  return false;
+}
+
+/* Callback data for dfs_locate_field_accessor_pre.  */
+
+struct locate_field_data
+{
+  locate_field_data (tree field_decl_, bool const_p_)
+  : field_decl (field_decl_), const_p (const_p_) {}
+
+  tree field_decl;
+  bool const_p;
+};
+
+/* Return a FUNCTION_DECL that is an "accessor" method for DATA, a FIELD_DECL,
+   callable via binfo, if one exists, otherwise return NULL_TREE.
+
+   Callback for dfs_walk_once_accessible for use within
+   locate_field_accessor.  */
+
+static tree
+dfs_locate_field_accessor_pre (tree binfo, void *data)
+{
+  locate_field_data *lfd = (locate_field_data *)data;
+  tree type = BINFO_TYPE (binfo);
+
+  vec<tree, va_gc> *member_vec;
+  tree fn;
+  size_t i;
+
+  if (!CLASS_TYPE_P (type))
+    return NULL_TREE;
+
+  member_vec = CLASSTYPE_MEMBER_VEC (type);
+  if (!member_vec)
+    return NULL_TREE;
+
+  for (i = 0; vec_safe_iterate (member_vec, i, &fn); ++i)
+    if (fn)
+      if (field_accessor_p (fn, lfd->field_decl, lfd->const_p))
+	return fn;
+
+  return NULL_TREE;
+}
+
+/* Return a FUNCTION_DECL that is an "accessor" method for FIELD_DECL,
+   callable via BASETYPE_PATH, if one exists, otherwise return NULL_TREE.  */
+
+tree
+locate_field_accessor (tree basetype_path, tree field_decl, bool const_p)
+{
+  if (TREE_CODE (basetype_path) != TREE_BINFO)
+    return NULL_TREE;
+
+  /* Walk the hierarchy, looking for a method of some base class that allows
+     access to the field.  */
+  locate_field_data lfd (field_decl, const_p);
+  return dfs_walk_once_accessible (basetype_path, /*friends=*/true,
+				   dfs_locate_field_accessor_pre,
+				   NULL, &lfd);
+}
+
+/* Check that virtual overrider OVERRIDER is acceptable for base function
+   BASEFN. Issue diagnostic, and return zero, if unacceptable.  */
+
+static int
+check_final_overrider (tree overrider, tree basefn)
+{
+  tree over_type = TREE_TYPE (overrider);
+  tree base_type = TREE_TYPE (basefn);
+  tree over_return = fndecl_declared_return_type (overrider);
+  tree base_return = fndecl_declared_return_type (basefn);
+  tree over_throw, base_throw;
+
+  int fail = 0;
+
+  if (DECL_INVALID_OVERRIDER_P (overrider))
+    return 0;
+
+  if (same_type_p (base_return, over_return))
+    /* OK */;
+  else if ((CLASS_TYPE_P (over_return) && CLASS_TYPE_P (base_return))
+	   || (TREE_CODE (base_return) == TREE_CODE (over_return)
+	       && POINTER_TYPE_P (base_return)))
+    {
+      /* Potentially covariant.  */
+      unsigned base_quals, over_quals;
+
+      fail = !POINTER_TYPE_P (base_return);
+      if (!fail)
+	{
+	  fail = cp_type_quals (base_return) != cp_type_quals (over_return);
+
+	  base_return = TREE_TYPE (base_return);
+	  over_return = TREE_TYPE (over_return);
+	}
+      base_quals = cp_type_quals (base_return);
+      over_quals = cp_type_quals (over_return);
+
+      if ((base_quals & over_quals) != over_quals)
+	fail = 1;
+
+      if (CLASS_TYPE_P (base_return) && CLASS_TYPE_P (over_return))
+	{
+	  /* Strictly speaking, the standard requires the return type to be
+	     complete even if it only differs in cv-quals, but that seems
+	     like a bug in the wording.  */
+	  if (!same_type_ignoring_top_level_qualifiers_p (base_return,
+							  over_return))
+	    {
+	      tree binfo = lookup_base (over_return, base_return,
+					ba_check, NULL, tf_none);
+
+	      if (!binfo || binfo == error_mark_node)
+		fail = 1;
+	    }
+	}
+      else if (can_convert_standard (TREE_TYPE (base_type),
+				     TREE_TYPE (over_type),
+				     tf_warning_or_error))
+	/* GNU extension, allow trivial pointer conversions such as
+	   converting to void *, or qualification conversion.  */
+	{
+	  if (pedwarn (DECL_SOURCE_LOCATION (overrider), 0,
+		       "invalid covariant return type for %q#D", overrider))
+	    inform (DECL_SOURCE_LOCATION (basefn),
+		    "  overriding %q#D", basefn);
+	}
+      else
+	fail = 2;
+    }
+  else
+    fail = 2;
+  if (!fail)
+    /* OK */;
+  else
+    {
+      if (fail == 1)
+	{
+	  error ("invalid covariant return type for %q+#D", overrider);
+	  error ("  overriding %q+#D", basefn);
+	}
+      else
+	{
+	  error ("conflicting return type specified for %q+#D", overrider);
+	  error ("  overriding %q+#D", basefn);
+	}
+      DECL_INVALID_OVERRIDER_P (overrider) = 1;
+      return 0;
+    }
+
+  /* Check throw specifier is at least as strict.  */
+  maybe_instantiate_noexcept (basefn);
+  maybe_instantiate_noexcept (overrider);
+  base_throw = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (basefn));
+  over_throw = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (overrider));
+
+  if (!comp_except_specs (base_throw, over_throw, ce_derived))
+    {
+      error ("looser throw specifier for %q+#F", overrider);
+      error ("  overriding %q+#F", basefn);
+      DECL_INVALID_OVERRIDER_P (overrider) = 1;
+      return 0;
+    }
+
+  /* Check for conflicting type attributes.  But leave transaction_safe for
+     set_one_vmethod_tm_attributes.  */
+  if (!comp_type_attributes (over_type, base_type)
+      && !tx_safe_fn_type_p (base_type)
+      && !tx_safe_fn_type_p (over_type))
+    {
+      error ("conflicting type attributes specified for %q+#D", overrider);
+      error ("  overriding %q+#D", basefn);
+      DECL_INVALID_OVERRIDER_P (overrider) = 1;
+      return 0;
+    }
+
+  /* A function declared transaction_safe_dynamic that overrides a function
+     declared transaction_safe (but not transaction_safe_dynamic) is
+     ill-formed.  */
+  if (tx_safe_fn_type_p (base_type)
+      && lookup_attribute ("transaction_safe_dynamic",
+			   DECL_ATTRIBUTES (overrider))
+      && !lookup_attribute ("transaction_safe_dynamic",
+			    DECL_ATTRIBUTES (basefn)))
+    {
+      error_at (DECL_SOURCE_LOCATION (overrider),
+		"%qD declared %<transaction_safe_dynamic%>", overrider);
+      inform (DECL_SOURCE_LOCATION (basefn),
+	      "overriding %qD declared %<transaction_safe%>", basefn);
+    }
+
+  if (DECL_DELETED_FN (basefn) != DECL_DELETED_FN (overrider))
+    {
+      if (DECL_DELETED_FN (overrider))
+	{
+	  error ("deleted function %q+D", overrider);
+	  error ("overriding non-deleted function %q+D", basefn);
+	  maybe_explain_implicit_delete (overrider);
+	}
+      else
+	{
+	  error ("non-deleted function %q+D", overrider);
+	  error ("overriding deleted function %q+D", basefn);
+	}
+      return 0;
+    }
+  if (DECL_FINAL_P (basefn))
+    {
+      error ("virtual function %q+D", overrider);
+      error ("overriding final function %q+D", basefn);
+      return 0;
+    }
+  return 1;
+}
+
+/* Given a class TYPE, and a function decl FNDECL, look for
+   virtual functions in TYPE's hierarchy which FNDECL overrides.
+   We do not look in TYPE itself, only its bases.
+
+   Returns nonzero, if we find any. Set FNDECL's DECL_VIRTUAL_P, if we
+   find that it overrides anything.
+
+   We check that every function which is overridden, is correctly
+   overridden.  */
+
+int
+look_for_overrides (tree type, tree fndecl)
+{
+  tree binfo = TYPE_BINFO (type);
+  tree base_binfo;
+  int ix;
+  int found = 0;
+
+  /* A constructor for a class T does not override a function T
+     in a base class.  */
+  if (DECL_CONSTRUCTOR_P (fndecl))
+    return 0;
+
+  for (ix = 0; BINFO_BASE_ITERATE (binfo, ix, base_binfo); ix++)
+    {
+      tree basetype = BINFO_TYPE (base_binfo);
+
+      if (TYPE_POLYMORPHIC_P (basetype))
+	found += look_for_overrides_r (basetype, fndecl);
+    }
+  return found;
+}
+
+/* Look in TYPE for virtual functions with the same signature as
+   FNDECL.  */
+
+tree
+look_for_overrides_here (tree type, tree fndecl)
+{
+  tree ovl = get_class_binding (type, DECL_NAME (fndecl));
+
+  for (ovl_iterator iter (ovl); iter; ++iter)
+    {
+      tree fn = *iter;
+
+      if (!DECL_VIRTUAL_P (fn))
+	/* Not a virtual.  */;
+      else if (DECL_CONTEXT (fn) != type)
+	/* Introduced with a using declaration.  */;
+      else if (DECL_STATIC_FUNCTION_P (fndecl))
+	{
+	  tree btypes = TYPE_ARG_TYPES (TREE_TYPE (fn));
+	  tree dtypes = TYPE_ARG_TYPES (TREE_TYPE (fndecl));
+	  if (compparms (TREE_CHAIN (btypes), dtypes))
+	    return fn;
+	}
+      else if (same_signature_p (fndecl, fn))
+	return fn;
+    }
+
+  return NULL_TREE;
+}
+
+/* Look in TYPE for virtual functions overridden by FNDECL. Check both
+   TYPE itself and its bases.  */
+
+static int
+look_for_overrides_r (tree type, tree fndecl)
+{
+  tree fn = look_for_overrides_here (type, fndecl);
+  if (fn)
+    {
+      if (DECL_STATIC_FUNCTION_P (fndecl))
+	{
+	  /* A static member function cannot match an inherited
+	     virtual member function.  */
+	  error ("%q+#D cannot be declared", fndecl);
+	  error ("  since %q+#D declared in base class", fn);
+	}
+      else
+	{
+	  /* It's definitely virtual, even if not explicitly set.  */
+	  DECL_VIRTUAL_P (fndecl) = 1;
+	  check_final_overrider (fndecl, fn);
+	}
+      return 1;
+    }
+
+  /* We failed to find one declared in this class. Look in its bases.  */
+  return look_for_overrides (type, fndecl);
+}
+
+/* Called via dfs_walk from dfs_get_pure_virtuals.  */
+
+static tree
+dfs_get_pure_virtuals (tree binfo, void *data)
+{
+  tree type = (tree) data;
+
+  /* We're not interested in primary base classes; the derived class
+     of which they are a primary base will contain the information we
+     need.  */
+  if (!BINFO_PRIMARY_P (binfo))
+    {
+      tree virtuals;
+
+      for (virtuals = BINFO_VIRTUALS (binfo);
+	   virtuals;
+	   virtuals = TREE_CHAIN (virtuals))
+	if (DECL_PURE_VIRTUAL_P (BV_FN (virtuals)))
+	  vec_safe_push (CLASSTYPE_PURE_VIRTUALS (type), BV_FN (virtuals));
+    }
+
+  return NULL_TREE;
+}
+
+/* Set CLASSTYPE_PURE_VIRTUALS for TYPE.  */
+
+void
+get_pure_virtuals (tree type)
+{
+  /* Clear the CLASSTYPE_PURE_VIRTUALS list; whatever is already there
+     is going to be overridden.  */
+  CLASSTYPE_PURE_VIRTUALS (type) = NULL;
+  /* Now, run through all the bases which are not primary bases, and
+     collect the pure virtual functions.  We look at the vtable in
+     each class to determine what pure virtual functions are present.
+     (A primary base is not interesting because the derived class of
+     which it is a primary base will contain vtable entries for the
+     pure virtuals in the base class.  */
+  dfs_walk_once (TYPE_BINFO (type), NULL, dfs_get_pure_virtuals, type);
+}
+
+/* Debug info for C++ classes can get very large; try to avoid
+   emitting it everywhere.
+
+   Note that this optimization wins even when the target supports
+   BINCL (if only slightly), and reduces the amount of work for the
+   linker.  */
+
+void
+maybe_suppress_debug_info (tree t)
+{
+  if (write_symbols == NO_DEBUG)
+    return;
+
+  /* We might have set this earlier in cp_finish_decl.  */
+  TYPE_DECL_SUPPRESS_DEBUG (TYPE_MAIN_DECL (t)) = 0;
+
+  /* Always emit the information for each class every time. */
+  if (flag_emit_class_debug_always)
+    return;
+
+  /* If we already know how we're handling this class, handle debug info
+     the same way.  */
+  if (CLASSTYPE_INTERFACE_KNOWN (t))
+    {
+      if (CLASSTYPE_INTERFACE_ONLY (t))
+	TYPE_DECL_SUPPRESS_DEBUG (TYPE_MAIN_DECL (t)) = 1;
+      /* else don't set it.  */
+    }
+  /* If the class has a vtable, write out the debug info along with
+     the vtable.  */
+  else if (TYPE_CONTAINS_VPTR_P (t))
+    TYPE_DECL_SUPPRESS_DEBUG (TYPE_MAIN_DECL (t)) = 1;
+
+  /* Otherwise, just emit the debug info normally.  */
+}
+
+/* Note that we want debugging information for a base class of a class
+   whose vtable is being emitted.  Normally, this would happen because
+   calling the constructor for a derived class implies calling the
+   constructors for all bases, which involve initializing the
+   appropriate vptr with the vtable for the base class; but in the
+   presence of optimization, this initialization may be optimized
+   away, so we tell finish_vtable_vardecl that we want the debugging
+   information anyway.  */
+
+static tree
+dfs_debug_mark (tree binfo, void * /*data*/)
+{
+  tree t = BINFO_TYPE (binfo);
+
+  if (CLASSTYPE_DEBUG_REQUESTED (t))
+    return dfs_skip_bases;
+
+  CLASSTYPE_DEBUG_REQUESTED (t) = 1;
+
+  return NULL_TREE;
+}
+
+/* Write out the debugging information for TYPE, whose vtable is being
+   emitted.  Also walk through our bases and note that we want to
+   write out information for them.  This avoids the problem of not
+   writing any debug info for intermediate basetypes whose
+   constructors, and thus the references to their vtables, and thus
+   the vtables themselves, were optimized away.  */
+
+void
+note_debug_info_needed (tree type)
+{
+  if (TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (type)))
+    {
+      TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (type)) = 0;
+      rest_of_type_compilation (type, namespace_bindings_p ());
+    }
+
+  dfs_walk_all (TYPE_BINFO (type), dfs_debug_mark, NULL, 0);
+}
+
+/* Helper for lookup_conversions_r.  TO_TYPE is the type converted to
+   by a conversion op in base BINFO.  VIRTUAL_DEPTH is nonzero if
+   BINFO is morally virtual, and VIRTUALNESS is nonzero if virtual
+   bases have been encountered already in the tree walk.  PARENT_CONVS
+   is the list of lists of conversion functions that could hide CONV
+   and OTHER_CONVS is the list of lists of conversion functions that
+   could hide or be hidden by CONV, should virtualness be involved in
+   the hierarchy.  Merely checking the conversion op's name is not
+   enough because two conversion operators to the same type can have
+   different names.  Return nonzero if we are visible.  */
+
+static int
+check_hidden_convs (tree binfo, int virtual_depth, int virtualness,
+		    tree to_type, tree parent_convs, tree other_convs)
+{
+  tree level, probe;
+
+  /* See if we are hidden by a parent conversion.  */
+  for (level = parent_convs; level; level = TREE_CHAIN (level))
+    for (probe = TREE_VALUE (level); probe; probe = TREE_CHAIN (probe))
+      if (same_type_p (to_type, TREE_TYPE (probe)))
+	return 0;
+
+  if (virtual_depth || virtualness)
+    {
+     /* In a virtual hierarchy, we could be hidden, or could hide a
+	conversion function on the other_convs list.  */
+      for (level = other_convs; level; level = TREE_CHAIN (level))
+	{
+	  int we_hide_them;
+	  int they_hide_us;
+	  tree *prev, other;
+
+	  if (!(virtual_depth || TREE_STATIC (level)))
+	    /* Neither is morally virtual, so cannot hide each other.  */
+	    continue;
+
+	  if (!TREE_VALUE (level))
+	    /* They evaporated away already.  */
+	    continue;
+
+	  they_hide_us = (virtual_depth
+			  && original_binfo (binfo, TREE_PURPOSE (level)));
+	  we_hide_them = (!they_hide_us && TREE_STATIC (level)
+			  && original_binfo (TREE_PURPOSE (level), binfo));
+
+	  if (!(we_hide_them || they_hide_us))
+	    /* Neither is within the other, so no hiding can occur.  */
+	    continue;
+
+	  for (prev = &TREE_VALUE (level), other = *prev; other;)
+	    {
+	      if (same_type_p (to_type, TREE_TYPE (other)))
+		{
+		  if (they_hide_us)
+		    /* We are hidden.  */
+		    return 0;
+
+		  if (we_hide_them)
+		    {
+		      /* We hide the other one.  */
+		      other = TREE_CHAIN (other);
+		      *prev = other;
+		      continue;
+		    }
+		}
+	      prev = &TREE_CHAIN (other);
+	      other = *prev;
+	    }
+	}
+    }
+  return 1;
+}
+
+/* Helper for lookup_conversions_r.  PARENT_CONVS is a list of lists
+   of conversion functions, the first slot will be for the current
+   binfo, if MY_CONVS is non-NULL.  CHILD_CONVS is the list of lists
+   of conversion functions from children of the current binfo,
+   concatenated with conversions from elsewhere in the hierarchy --
+   that list begins with OTHER_CONVS.  Return a single list of lists
+   containing only conversions from the current binfo and its
+   children.  */
+
+static tree
+split_conversions (tree my_convs, tree parent_convs,
+		   tree child_convs, tree other_convs)
+{
+  tree t;
+  tree prev;
+
+  /* Remove the original other_convs portion from child_convs.  */
+  for (prev = NULL, t = child_convs;
+       t != other_convs; prev = t, t = TREE_CHAIN (t))
+    continue;
+
+  if (prev)
+    TREE_CHAIN (prev) = NULL_TREE;
+  else
+    child_convs = NULL_TREE;
+
+  /* Attach the child convs to any we had at this level.  */
+  if (my_convs)
+    {
+      my_convs = parent_convs;
+      TREE_CHAIN (my_convs) = child_convs;
+    }
+  else
+    my_convs = child_convs;
+
+  return my_convs;
+}
+
+/* Worker for lookup_conversions.  Lookup conversion functions in
+   BINFO and its children.  VIRTUAL_DEPTH is nonzero, if BINFO is in a
+   morally virtual base, and VIRTUALNESS is nonzero, if we've
+   encountered virtual bases already in the tree walk.  PARENT_CONVS
+   is a list of conversions within parent binfos.  OTHER_CONVS are
+   conversions found elsewhere in the tree.  Return the conversions
+   found within this portion of the graph in CONVS.  Return nonzero if
+   we encountered virtualness.  We keep template and non-template
+   conversions separate, to avoid unnecessary type comparisons.
+
+   The located conversion functions are held in lists of lists.  The
+   TREE_VALUE of the outer list is the list of conversion functions
+   found in a particular binfo.  The TREE_PURPOSE of both the outer
+   and inner lists is the binfo at which those conversions were
+   found.  TREE_STATIC is set for those lists within of morally
+   virtual binfos.  The TREE_VALUE of the inner list is the conversion
+   function or overload itself.  The TREE_TYPE of each inner list node
+   is the converted-to type.  */
+
+static int
+lookup_conversions_r (tree binfo, int virtual_depth, int virtualness,
+		      tree parent_convs, tree other_convs, tree *convs)
+{
+  int my_virtualness = 0;
+  tree my_convs = NULL_TREE;
+  tree child_convs = NULL_TREE;
+
+  /* If we have no conversion operators, then don't look.  */
+  if (!TYPE_HAS_CONVERSION (BINFO_TYPE (binfo)))
+    {
+      *convs = NULL_TREE;
+
+      return 0;
+    }
+
+  if (BINFO_VIRTUAL_P (binfo))
+    virtual_depth++;
+
+  /* First, locate the unhidden ones at this level.  */
+  if (tree conv = get_class_binding (BINFO_TYPE (binfo), conv_op_identifier))
+  for (ovl_iterator iter (conv); iter; ++iter)
+    {
+      tree fn = *iter;
+      tree type = DECL_CONV_FN_TYPE (fn);
+
+      if (TREE_CODE (fn) != TEMPLATE_DECL && type_uses_auto (type))
+	{
+	  mark_used (fn);
+	  type = DECL_CONV_FN_TYPE (fn);
+	}
+
+      if (check_hidden_convs (binfo, virtual_depth, virtualness,
+			      type, parent_convs, other_convs))
+	{
+	  my_convs = tree_cons (binfo, fn, my_convs);
+	  TREE_TYPE (my_convs) = type;
+	  if (virtual_depth)
+	    {
+	      TREE_STATIC (my_convs) = 1;
+	      my_virtualness = 1;
+	    }
+	}
+    }
+
+  if (my_convs)
+    {
+      parent_convs = tree_cons (binfo, my_convs, parent_convs);
+      if (virtual_depth)
+	TREE_STATIC (parent_convs) = 1;
+    }
+
+  child_convs = other_convs;
+
+  /* Now iterate over each base, looking for more conversions.  */
+  unsigned i;
+  tree base_binfo;
+  for (i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
+    {
+      tree base_convs;
+      unsigned base_virtualness;
+
+      base_virtualness = lookup_conversions_r (base_binfo,
+					       virtual_depth, virtualness,
+					       parent_convs, child_convs,
+					       &base_convs);
+      if (base_virtualness)
+	my_virtualness = virtualness = 1;
+      child_convs = chainon (base_convs, child_convs);
+    }
+
+  *convs = split_conversions (my_convs, parent_convs,
+			      child_convs, other_convs);
+
+  return my_virtualness;
+}
+
+/* Return a TREE_LIST containing all the non-hidden user-defined
+   conversion functions for TYPE (and its base-classes).  The
+   TREE_VALUE of each node is the FUNCTION_DECL of the conversion
+   function.  The TREE_PURPOSE is the BINFO from which the conversion
+   functions in this node were selected.  This function is effectively
+   performing a set of member lookups as lookup_fnfield does, but
+   using the type being converted to as the unique key, rather than the
+   field name.  */
+
+tree
+lookup_conversions (tree type)
+{
+  tree convs;
+
+  complete_type (type);
+  if (!CLASS_TYPE_P (type) || !TYPE_BINFO (type))
+    return NULL_TREE;
+
+  lookup_conversions_r (TYPE_BINFO (type), 0, 0, NULL_TREE, NULL_TREE, &convs);
+
+  tree list = NULL_TREE;
+  
+  /* Flatten the list-of-lists */
+  for (; convs; convs = TREE_CHAIN (convs))
+    {
+      tree probe, next;
+
+      for (probe = TREE_VALUE (convs); probe; probe = next)
+	{
+	  next = TREE_CHAIN (probe);
+
+	  TREE_CHAIN (probe) = list;
+	  list = probe;
+	}
+    }
+
+  return list;
+}
+
+/* Returns the binfo of the first direct or indirect virtual base derived
+   from BINFO, or NULL if binfo is not via virtual.  */
+
+tree
+binfo_from_vbase (tree binfo)
+{
+  for (; binfo; binfo = BINFO_INHERITANCE_CHAIN (binfo))
+    {
+      if (BINFO_VIRTUAL_P (binfo))
+	return binfo;
+    }
+  return NULL_TREE;
+}
+
+/* Returns the binfo of the first direct or indirect virtual base derived
+   from BINFO up to the TREE_TYPE, LIMIT, or NULL if binfo is not
+   via virtual.  */
+
+tree
+binfo_via_virtual (tree binfo, tree limit)
+{
+  if (limit && !CLASSTYPE_VBASECLASSES (limit))
+    /* LIMIT has no virtual bases, so BINFO cannot be via one.  */
+    return NULL_TREE;
+
+  for (; binfo && !SAME_BINFO_TYPE_P (BINFO_TYPE (binfo), limit);
+       binfo = BINFO_INHERITANCE_CHAIN (binfo))
+    {
+      if (BINFO_VIRTUAL_P (binfo))
+	return binfo;
+    }
+  return NULL_TREE;
+}
+
+/* BINFO is for a base class in some hierarchy.  Return true iff it is a
+   direct base.  */
+
+bool
+binfo_direct_p (tree binfo)
+{
+  tree d_binfo = BINFO_INHERITANCE_CHAIN (binfo);
+  if (BINFO_INHERITANCE_CHAIN (d_binfo))
+    /* A second inheritance chain means indirect.  */
+    return false;
+  if (!BINFO_VIRTUAL_P (binfo))
+    /* Non-virtual, so only one inheritance chain means direct.  */
+    return true;
+  /* A virtual base looks like a direct base, so we need to look through the
+     direct bases to see if it's there.  */
+  tree b_binfo;
+  for (int i = 0; BINFO_BASE_ITERATE (d_binfo, i, b_binfo); ++i)
+    if (b_binfo == binfo)
+      return true;
+  return false;
+}
+
+/* BINFO is a base binfo in the complete type BINFO_TYPE (HERE).
+   Find the equivalent binfo within whatever graph HERE is located.
+   This is the inverse of original_binfo.  */
+
+tree
+copied_binfo (tree binfo, tree here)
+{
+  tree result = NULL_TREE;
+
+  if (BINFO_VIRTUAL_P (binfo))
+    {
+      tree t;
+
+      for (t = here; BINFO_INHERITANCE_CHAIN (t);
+	   t = BINFO_INHERITANCE_CHAIN (t))
+	continue;
+
+      result = binfo_for_vbase (BINFO_TYPE (binfo), BINFO_TYPE (t));
+    }
+  else if (BINFO_INHERITANCE_CHAIN (binfo))
+    {
+      tree cbinfo;
+      tree base_binfo;
+      int ix;
+
+      cbinfo = copied_binfo (BINFO_INHERITANCE_CHAIN (binfo), here);
+      for (ix = 0; BINFO_BASE_ITERATE (cbinfo, ix, base_binfo); ix++)
+	if (SAME_BINFO_TYPE_P (BINFO_TYPE (base_binfo), BINFO_TYPE (binfo)))
+	  {
+	    result = base_binfo;
+	    break;
+	  }
+    }
+  else
+    {
+      gcc_assert (SAME_BINFO_TYPE_P (BINFO_TYPE (here), BINFO_TYPE (binfo)));
+      result = here;
+    }
+
+  gcc_assert (result);
+  return result;
+}
+
+tree
+binfo_for_vbase (tree base, tree t)
+{
+  unsigned ix;
+  tree binfo;
+  vec<tree, va_gc> *vbases;
+
+  for (vbases = CLASSTYPE_VBASECLASSES (t), ix = 0;
+       vec_safe_iterate (vbases, ix, &binfo); ix++)
+    if (SAME_BINFO_TYPE_P (BINFO_TYPE (binfo), base))
+      return binfo;
+  return NULL;
+}
+
+/* BINFO is some base binfo of HERE, within some other
+   hierarchy. Return the equivalent binfo, but in the hierarchy
+   dominated by HERE.  This is the inverse of copied_binfo.  If BINFO
+   is not a base binfo of HERE, returns NULL_TREE.  */
+
+tree
+original_binfo (tree binfo, tree here)
+{
+  tree result = NULL;
+
+  if (SAME_BINFO_TYPE_P (BINFO_TYPE (binfo), BINFO_TYPE (here)))
+    result = here;
+  else if (BINFO_VIRTUAL_P (binfo))
+    result = (CLASSTYPE_VBASECLASSES (BINFO_TYPE (here))
+	      ? binfo_for_vbase (BINFO_TYPE (binfo), BINFO_TYPE (here))
+	      : NULL_TREE);
+  else if (BINFO_INHERITANCE_CHAIN (binfo))
+    {
+      tree base_binfos;
+
+      base_binfos = original_binfo (BINFO_INHERITANCE_CHAIN (binfo), here);
+      if (base_binfos)
+	{
+	  int ix;
+	  tree base_binfo;
+
+	  for (ix = 0; (base_binfo = BINFO_BASE_BINFO (base_binfos, ix)); ix++)
+	    if (SAME_BINFO_TYPE_P (BINFO_TYPE (base_binfo),
+				   BINFO_TYPE (binfo)))
+	      {
+		result = base_binfo;
+		break;
+	      }
+	}
+    }
+
+  return result;
+}
+
+/* True iff TYPE has any dependent bases (and therefore we can't say
+   definitively that another class is not a base of an instantiation of
+   TYPE).  */
+
+bool
+any_dependent_bases_p (tree type)
+{
+  if (!type || !CLASS_TYPE_P (type) || !processing_template_decl)
+    return false;
+
+  unsigned i;
+  tree base_binfo;
+  FOR_EACH_VEC_SAFE_ELT (BINFO_BASE_BINFOS (TYPE_BINFO (type)), i, base_binfo)
+    if (BINFO_DEPENDENT_BASE_P (base_binfo))
+      return true;
+
+  return false;
+}