path: root/gcc/cp/search.c

/* Breadth-first and depth-first routines for
   searching multiple-inheritance lattice for GNU C++.
   Copyright (C) 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   1999, 2000, 2002, 2003, 2004 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 2, 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 COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* High-level class interface.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "tree.h"
#include "cp-tree.h"
#include "obstack.h"
#include "flags.h"
#include "rtl.h"
#include "output.h"
#include "toplev.h"
#include "stack.h"

/* Obstack used for remembering decision points of breadth-first.  */

static struct obstack search_obstack;

/* Methods for pushing and popping objects to and from obstacks.  */

struct stack_level *
push_stack_level (struct obstack *obstack, char *tp,/* Sony NewsOS 5.0 compiler doesn't like void * here.  */
		  int size)
{
  struct stack_level *stack;
  obstack_grow (obstack, tp, size);
  stack = (struct stack_level *) ((char*)obstack_next_free (obstack) - size);
  obstack_finish (obstack);
  stack->obstack = obstack;
  stack->first = (tree *) obstack_base (obstack);
  stack->limit = obstack_room (obstack) / sizeof (tree *);
  return stack;
}

struct stack_level *
pop_stack_level (struct stack_level *stack)
{
  struct stack_level *tem = stack;
  struct obstack *obstack = tem->obstack;
  stack = tem->prev;
  obstack_free (obstack, tem);
  return stack;
}

#define search_level stack_level
static struct search_level *search_stack;

struct vbase_info 
{
  /* The class dominating the hierarchy.  */
  tree type;
  /* A pointer to a complete object of the indicated TYPE.  */
  tree decl_ptr;
  tree inits;
};

static tree dfs_check_overlap (tree, void *);
static tree dfs_no_overlap_yet (tree, int, void *);
static base_kind lookup_base_r (tree, tree, base_access, bool, tree *);
static int dynamic_cast_base_recurse (tree, tree, bool, tree *);
static tree marked_pushdecls_p (tree, int, void *);
static tree unmarked_pushdecls_p (tree, int, void *);
static tree dfs_debug_unmarkedp (tree, int, void *);
static tree dfs_debug_mark (tree, void *);
static tree dfs_push_type_decls (tree, void *);
static tree dfs_push_decls (tree, void *);
static tree dfs_unuse_fields (tree, void *);
static tree add_conversions (tree, void *);
static int look_for_overrides_r (tree, tree);
static struct search_level *push_search_level (struct stack_level *,
					       struct obstack *);
static struct search_level *pop_search_level (struct stack_level *);
static tree bfs_walk (tree, tree (*) (tree, void *),
		      tree (*) (tree, int, void *), void *);
static tree lookup_field_queue_p (tree, int, void *);
static int shared_member_p (tree);
static tree lookup_field_r (tree, void *);
static tree dfs_accessible_queue_p (tree, int, void *);
static tree dfs_accessible_p (tree, void *);
static tree dfs_access_in_type (tree, void *);
static access_kind access_in_type (tree, tree);
static int protected_accessible_p (tree, tree, tree);
static int friend_accessible_p (tree, tree, tree);
static void setup_class_bindings (tree, int);
static int template_self_reference_p (tree, tree);
static tree dfs_get_pure_virtuals (tree, void *);

/* Allocate a level of searching.  */

static struct search_level *
push_search_level (struct stack_level *stack, struct obstack *obstack)
{
  struct search_level tem;

  tem.prev = stack;
  return push_stack_level (obstack, (char *)&tem, sizeof (tem));
}

/* Discard a level of search allocation.  */

static struct search_level *
pop_search_level (struct stack_level *obstack)
{
  struct search_level *stack = pop_stack_level (obstack);

  return stack;
}

/* Variables for gathering statistics.  */
#ifdef GATHER_STATISTICS
static int n_fields_searched;
static int n_calls_lookup_field, n_calls_lookup_field_1;
static int n_calls_lookup_fnfields, n_calls_lookup_fnfields_1;
static int n_calls_get_base_type;
static int n_outer_fields_searched;
static int n_contexts_saved;
#endif /* GATHER_STATISTICS */


/* Worker for lookup_base.  BINFO is the binfo we are searching at,
   BASE is the RECORD_TYPE we are searching for.  ACCESS is the
   required access checks.  IS_VIRTUAL indicates if BINFO is morally
   virtual.

   If BINFO is of the required type, then *BINFO_PTR is examined to
   compare with any other instance of BASE we might have already
   discovered. *BINFO_PTR is initialized and a base_kind return value
   indicates what kind of base was located.

   Otherwise BINFO's bases are searched.  */

static base_kind
lookup_base_r (tree binfo, tree base, base_access access,
	       bool is_virtual,			/* inside a virtual part */
	       tree *binfo_ptr)
{
  int i;
  tree bases, accesses;
  base_kind found = bk_not_base;
  
  if (same_type_p (BINFO_TYPE (binfo), base))
    {
      /* We have found a base. Check against what we have found
         already.  */
      found = bk_same_type;
      if (is_virtual)
	found = bk_via_virtual;
      
      if (!*binfo_ptr)
	*binfo_ptr = binfo;
      else if (binfo != *binfo_ptr)
	{
	  if (access != ba_any)
	    *binfo_ptr = NULL;
	  else if (!is_virtual)
	    /* Prefer a non-virtual base.  */
	    *binfo_ptr = binfo;
	  found = bk_ambig;
	}
      
      return found;
    }
  
  bases = BINFO_BASETYPES (binfo);
  accesses = BINFO_BASEACCESSES (binfo);
  if (!bases)
    return bk_not_base;
  
  for (i = TREE_VEC_LENGTH (bases); i--;)
    {
      tree base_binfo = TREE_VEC_ELT (bases, i);
      base_kind bk;

      bk = lookup_base_r (base_binfo, base,
		    	  access,
			  is_virtual || TREE_VIA_VIRTUAL (base_binfo),
			  binfo_ptr);

      switch (bk)
	{
	case bk_ambig:
	  if (access != ba_any)
	    return bk;
	  found = bk;
	  break;
	  
	case bk_same_type:
	  bk = bk_proper_base;
	  /* Fall through.  */
	case bk_proper_base:
	  my_friendly_assert (found == bk_not_base, 20010723);
	  found = bk;
	  break;
	  
	case bk_via_virtual:
	  if (found != bk_ambig)
	    found = bk;
	  break;
	  
	case bk_not_base:
	  break;

	default:
	  abort ();
	}
    }
  return found;
}

/* Returns true if type BASE is accessible in T.  (BASE is known to be
   a base class of T.)  */

bool
accessible_base_p (tree t, tree base)
{
  tree decl;

  /* [class.access.base]

     A base class is said to be accessible if an invented public
     member of the base class is accessible.  */
  /* 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 = TREE_CHAIN (decl);
  while (ANON_AGGR_TYPE_P (t))
    t = TYPE_CONTEXT (t);
  return accessible_p (t, decl);
}

/* 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, and the ba_quiet bit is
   not set in ACCESS, then an error is issued and error_mark_node is
   returned.  If the ba_quiet bit is set, then no error is issued and
   NULL_TREE is returned.  */

tree
lookup_base (tree t, tree base, base_access access, base_kind *kind_ptr)
{
  tree binfo = NULL;		/* The binfo we've found so far.  */
  tree t_binfo = NULL;
  base_kind bk;
  
  if (t == error_mark_node || base == error_mark_node)
    {
      if (kind_ptr)
	*kind_ptr = bk_not_base;
      return error_mark_node;
    }
  my_friendly_assert (TYPE_P (base), 20011127);
  
  if (!TYPE_P (t))
    {
      t_binfo = t;
      t = BINFO_TYPE (t);
    }
  else 
    t_binfo = TYPE_BINFO (t);

  /* Ensure that the types are instantiated.  */
  t = complete_type (TYPE_MAIN_VARIANT (t));
  base = complete_type (TYPE_MAIN_VARIANT (base));
  
  bk = lookup_base_r (t_binfo, base, access, 0, &binfo);

  /* Check that the base is unambiguous and accessible.  */
  if (access != ba_any)
    switch (bk)
      {
      case bk_not_base:
	break;

      case bk_ambig:
	binfo = NULL_TREE;
	if (!(access & ba_quiet))
	  {
	    error ("`%T' is an ambiguous base of `%T'", base, t);
	    binfo = error_mark_node;
	  }
	break;

      default:
	if ((access & ~ba_quiet) != ba_ignore
	    /* 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))
	  {
	    if (!(access & ba_quiet))
	      {
		error ("`%T' is an inaccessible base of `%T'", base, t);
		binfo = error_mark_node;
	      }
	    else
	      binfo = NULL_TREE;
	    bk = bk_inaccessible;
	  }
	break;
      }

  if (kind_ptr)
    *kind_ptr = bk;
  
  return binfo;
}

/* Worker function for get_dynamic_cast_base_type.  */

static int
dynamic_cast_base_recurse (tree subtype, tree binfo, bool is_via_virtual,
			   tree *offset_ptr)
{
  tree binfos, accesses;
  int i, n_baselinks;
  int worst = -2;
  
  if (BINFO_TYPE (binfo) == subtype)
    {
      if (is_via_virtual)
        return -1;
      else
        {
          *offset_ptr = BINFO_OFFSET (binfo);
          return 0;
        }
    }
  
  binfos = BINFO_BASETYPES (binfo);
  accesses = BINFO_BASEACCESSES (binfo);
  n_baselinks = binfos ? TREE_VEC_LENGTH (binfos) : 0;
  for (i = 0; i < n_baselinks; i++)
    {
      tree base_binfo = TREE_VEC_ELT (binfos, i);
      tree base_access = TREE_VEC_ELT (accesses, i);
      int rval;
      
      if (base_access != access_public_node)
        continue;
      rval = dynamic_cast_base_recurse
             (subtype, base_binfo,
              is_via_virtual || TREE_VIA_VIRTUAL (base_binfo), offset_ptr);
      if (worst == -2)
        worst = rval;
      else if (rval >= 0)
        worst = worst >= 0 ? -3 : worst;
      else if (rval == -1)
        worst = -1;
      else if (rval == -3 && worst != -1)
        worst = -3;
    }
  return worst;
}

/* 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
get_dynamic_cast_base_type (tree subtype, tree target)
{
  tree offset = NULL_TREE;
  int boff = dynamic_cast_base_recurse (subtype, TYPE_BINFO (target),
                                        false, &offset);
  
  if (!boff)
    return offset;
  offset = build_int_2 (boff, -1);
  TREE_TYPE (offset) = ssizetype;
  return offset;
}

/* 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.  */

/* Do a 1-level search for NAME as a member of TYPE.  The caller must
   figure out whether it can access this field.  (Since it is only one
   level, this is reasonable.)  */

tree
lookup_field_1 (tree type, tree name, bool want_type)
{
  tree field;

  if (TREE_CODE (type) == TEMPLATE_TYPE_PARM
      || TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM
      || TREE_CODE (type) == TYPENAME_TYPE)
    /* The TYPE_FIELDS of a TEMPLATE_TYPE_PARM and 
       BOUND_TEMPLATE_TEMPLATE_PARM are not fields at all;
       instead TYPE_FIELDS is the TEMPLATE_PARM_INDEX.  (Miraculously,
       the code often worked even when we treated the index as a list
       of fields!)
       The TYPE_FIELDS of TYPENAME_TYPE is its TYPENAME_TYPE_FULLNAME.  */
    return NULL_TREE;

  if (TYPE_NAME (type)
      && DECL_LANG_SPECIFIC (TYPE_NAME (type))
      && DECL_SORTED_FIELDS (TYPE_NAME (type)))
    {
      tree *fields = &DECL_SORTED_FIELDS (TYPE_NAME (type))->elts[0];
      int lo = 0, hi = DECL_SORTED_FIELDS (TYPE_NAME (type))->len;
      int i;

      while (lo < hi)
	{
	  i = (lo + hi) / 2;

#ifdef GATHER_STATISTICS
	  n_fields_searched++;
#endif /* GATHER_STATISTICS */

	  if (DECL_NAME (fields[i]) > name)
	    hi = i;
	  else if (DECL_NAME (fields[i]) < name)
	    lo = i + 1;
	  else
	    {
	      field = NULL_TREE;

	      /* We might have a nested class and a field with the
		 same name; we sorted them appropriately via
		 field_decl_cmp, so just look for the first or last
		 field with this name.  */
	      if (want_type)
		{
		  do
		    field = fields[i--];
		  while (i >= lo && DECL_NAME (fields[i]) == name);
		  if (TREE_CODE (field) != TYPE_DECL
		      && !DECL_CLASS_TEMPLATE_P (field))
		    field = NULL_TREE;
		}
	      else
		{
		  do
		    field = fields[i++];
		  while (i < hi && DECL_NAME (fields[i]) == name);
		}
	      return field;
	    }
	}
      return NULL_TREE;
    }

  field = TYPE_FIELDS (type);

#ifdef GATHER_STATISTICS
  n_calls_lookup_field_1++;
#endif /* GATHER_STATISTICS */
  for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field))
    {
#ifdef GATHER_STATISTICS
      n_fields_searched++;
#endif /* GATHER_STATISTICS */
      my_friendly_assert (DECL_P (field), 0);
      if (DECL_NAME (field) == NULL_TREE
	  && ANON_AGGR_TYPE_P (TREE_TYPE (field)))
	{
	  tree temp = lookup_field_1 (TREE_TYPE (field), name, want_type);
	  if (temp)
	    return temp;
	}
      if (TREE_CODE (field) == USING_DECL)
	/* For now, we're just treating member using declarations as
	   old ARM-style access declarations.  Thus, there's no reason
	   to return a USING_DECL, and the rest of the compiler can't
	   handle it.  Once the class is defined, these are purged
	   from TYPE_FIELDS anyhow; see handle_using_decl.  */
	continue;

      if (DECL_NAME (field) == name
	  && (!want_type 
	      || TREE_CODE (field) == TYPE_DECL
	      || DECL_CLASS_TEMPLATE_P (field)))
	return field;
    }
  /* Not found.  */
  if (name == vptr_identifier)
    {
      /* Give the user what s/he thinks s/he wants.  */
      if (TYPE_POLYMORPHIC_P (type))
	return TYPE_VFIELD (type);
    }
  return NULL_TREE;
}

/* 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.  */

tree
current_scope (void)
{
  if (current_function_decl == NULL_TREE)
    return current_class_type;
  if (current_class_type == NULL_TREE)
    return current_function_decl;
  if ((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;

  return current_class_type;
}

/* 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 ();
  return cs && TREE_CODE (cs) == 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)
{
  /* We are in a namespace scope if we are not it a class scope or a
     function scope.  */
  return !current_scope();
}

/* 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))
    context = TYPE_CONTEXT (context);
  if (!context)
    context = global_namespace;

  return context;
}

/* The accessibility routines use BINFO_ACCESS for scratch space
   during the computation of the accessibility of some declaration.  */

#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.  The CONST_DECL for an enumeration
	 constant will not have DECL_LANG_SPECIFIC, and thus no
	 DECL_ACCESS.  */
      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
		my_friendly_assert (false, 20030217);
	    }
	}

      if (!access)
	{
	  int i;
	  int n_baselinks;
	  tree binfos, accesses;
	  
	  /* Otherwise, scan our baseclasses, and pick the most favorable
	     access.  */
	  binfos = BINFO_BASETYPES (binfo);
	  accesses = BINFO_BASEACCESSES (binfo);
	  n_baselinks = binfos ? TREE_VEC_LENGTH (binfos) : 0;
	  for (i = 0; i < n_baselinks; ++i)
	    {
	      tree base_binfo = TREE_VEC_ELT (binfos, i);
	      tree base_access = TREE_VEC_ELT (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);

  /* Mark TYPE as visited so that if we reach it again we do not
     duplicate our efforts here.  */
  BINFO_MARKED (binfo) = 1;

  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_real (binfo, 0, dfs_access_in_type, unmarkedp, decl);
  dfs_walk (binfo, dfs_unmark, markedp,  0);

  return BINFO_ACCESS (binfo);
}

/* Called from accessible_p via dfs_walk.  */

static tree
dfs_accessible_queue_p (tree derived, int ix, void *data ATTRIBUTE_UNUSED)
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  if (BINFO_MARKED (binfo))
    return NULL_TREE;

  /* If this class is inherited via private or protected inheritance,
     then we can't see it, unless we are a friend of the derived class.  */
  if (BINFO_BASEACCESS (derived, ix) != access_public_node
      && !is_friend (BINFO_TYPE (derived), current_scope ()))
    return NULL_TREE;

  return binfo;
}

/* Called from accessible_p via dfs_walk.  */

static tree
dfs_accessible_p (tree binfo, void *data ATTRIBUTE_UNUSED)
{
  access_kind access;

  BINFO_MARKED (binfo) = 1;
  access = BINFO_ACCESS (binfo);
  if (access != ak_none
      && is_friend (BINFO_TYPE (binfo), current_scope ()))
    return binfo;

  return NULL_TREE;
}

/* Returns nonzero if it is OK to access DECL through an object
   indicated by BINFO in the context of DERIVED.  */

static int
protected_accessible_p (tree decl, tree derived, tree binfo)
{
  access_kind access;

  /* 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 private or
       protected.  

    Here DERIVED is a possible P and DECL is m.  accessible_p will
    iterate over various values of N, but the access to m in DERIVED
    does not change.

    Note that I believe that the passage above is wrong, and should read
    "...is private or protected or public"; otherwise you get bizarre results
    whereby a public using-decl can prevent you from accessing a protected
    member of a base.  (jason 2000/02/28)  */

  /* If DERIVED isn't derived from m's class, then it can't be a P.  */
  if (!DERIVED_FROM_P (context_for_name_lookup (decl), derived))
    return 0;

  access = access_in_type (derived, decl);

  /* If m is inaccessible in DERIVED, then it's not a P.  */
  if (access == ak_none)
    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))
    {
      /* We can tell through what the reference is occurring by
	 chasing BINFO up to the root.  */
      tree t = binfo;
      while (BINFO_INHERITANCE_CHAIN (t))
	t = BINFO_INHERITANCE_CHAIN (t);
      
      if (!DERIVED_FROM_P (derived, BINFO_TYPE (t)))
	return 0;
    }

  return 1;
}

/* Returns nonzero if SCOPE is a friend of a type which would be able
   to access DECL through the object indicated by BINFO.  */

static int
friend_accessible_p (tree scope, tree decl, tree binfo)
{
  tree befriending_classes;
  tree t;

  if (!scope)
    return 0;

  if (TREE_CODE (scope) == FUNCTION_DECL
      || DECL_FUNCTION_TEMPLATE_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), binfo))
      return 1;

  /* Nested classes are implicitly friends of their enclosing types, as
     per core issue 45 (this is a change from the standard).  */
  if (TYPE_P (scope))
    for (t = TYPE_CONTEXT (scope); t && TYPE_P (t); t = TYPE_CONTEXT (t))
      if (protected_accessible_p (decl, t, binfo))
	return 1;

  if (TREE_CODE (scope) == FUNCTION_DECL
      || DECL_FUNCTION_TEMPLATE_P (scope))
    {
      /* Perhaps this SCOPE is a member of a class which is a 
	 friend.  */ 
      if (DECL_CLASS_SCOPE_P (decl)
	  && friend_accessible_p (DECL_CONTEXT (scope), decl, binfo))
	return 1;

      /* Or an instantiation of something which is a friend.  */
      if (DECL_TEMPLATE_INFO (scope))
	return friend_accessible_p (DECL_TI_TEMPLATE (scope), decl, binfo);
    }
  else if (CLASSTYPE_TEMPLATE_INFO (scope))
    return friend_accessible_p (CLASSTYPE_TI_TEMPLATE (scope), decl, binfo);

  return 0;
}

/* 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.  */

int 
accessible_p (tree type, tree decl)
{
  tree binfo;
  tree t;
  tree scope;
  access_kind access;

  /* Nonzero if it's OK to access DECL if it has protected
     accessibility in TYPE.  */
  int protected_ok = 0;

  /* 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.  */
  scope = current_scope ();
  if (scope && DECL_THUNK_P (scope))
    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.  */
  if (processing_template_decl)
    return 1;

  if (!TYPE_P (type))
    {
      binfo = type;
      type = BINFO_TYPE (type);
    }
  else
    binfo = TYPE_BINFO (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 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.  */

  /* Figure out where the reference is occurring.  Check to see if
     DECL is private or protected in this scope, since that will
     determine whether protected access is allowed.  */
  if (current_class_type)
    protected_ok = protected_accessible_p (decl, current_class_type, binfo);

  /* Now, loop through the classes of which we are a friend.  */
  if (!protected_ok)
    protected_ok = friend_accessible_p (scope, decl, binfo);

  /* Standardize the binfo that access_in_type will use.  We don't
     need to know what path was chosen from this point onwards.  */
  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
      || (access == ak_protected && protected_ok))
    return 1;
  else
    {
      /* Walk the hierarchy again, looking for a base class that allows
	 access.  */
      t = dfs_walk (binfo, dfs_accessible_p, dfs_accessible_queue_p, 0);
      /* Clear any mark bits.  Note that we have to walk the whole tree
	 here, since we have aborted the previous walk from some point
	 deep in the tree.  */
      dfs_walk (binfo, dfs_unmark, 0,  0);

      return t != 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;
};

/* Returns nonzero if BINFO is not hidden by the value found by the
   lookup so far.  If BINFO is hidden, then there's no need to look in
   it.  DATA is really a struct lookup_field_info.  Called from
   lookup_field via breadth_first_search.  */

static tree
lookup_field_queue_p (tree derived, int ix, void *data)
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  struct lookup_field_info *lfi = (struct lookup_field_info *) data;

  /* Don't look for constructors or destructors in base classes.  */
  if (IDENTIFIER_CTOR_OR_DTOR_P (lfi->name))
    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 && original_binfo (binfo, lfi->rval_binfo))
    return NULL_TREE;

  /* If this is a dependent base, don't look in it.  */
  if (BINFO_DEPENDENT_BASE_P (binfo))
    return NULL_TREE;
  
  return binfo;
}

/* Within the scope of a template class, you can refer to the to the
   current specialization with the name of the template itself.  For
   example:
   
     template <typename T> struct S { S* sp; }

   Returns nonzero if DECL is such a declaration in a class TYPE.  */

static int
template_self_reference_p (tree type, tree decl)
{
  return  (CLASSTYPE_USE_TEMPLATE (type)
	   && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (type))
	   && TREE_CODE (decl) == TYPE_DECL
	   && DECL_ARTIFICIAL (decl)
	   && DECL_NAME (decl) == constructor_name (type));
}


/* 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.  */

static int
shared_member_p (tree t)
{
  if (TREE_CODE (t) == VAR_DECL || TREE_CODE (t) == TYPE_DECL \
      || TREE_CODE (t) == CONST_DECL)
    return 1;
  if (is_overloaded_fn (t))
    {
      for (; t; t = OVL_NEXT (t))
	{
	  tree fn = OVL_CURRENT (t);
	  if (DECL_NONSTATIC_MEMBER_FUNCTION_P (fn))
	    return 0;
	}
      return 1;
    }
  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;

  /* First, look for a function.  There can't be a function and a data
     member with the same name, and if there's a function and a type
     with the same name, the type is hidden by the function.  */
  if (!lfi->want_type)
    {
      int idx = lookup_fnfields_1 (type, lfi->name);
      if (idx >= 0)
	nval = TREE_VEC_ELT (CLASSTYPE_METHOD_VEC (type), idx);
    }

  if (!nval)
    /* Look for a data member or type.  */
    nval = lookup_field_1 (type, lfi->name, lfi->want_type);

  /* If there is no declaration with the indicated name in this type,
     then there's nothing to do.  */
  if (!nval)
    return NULL_TREE;

  /* If we're looking up a type (as with an elaborated type specifier)
     we ignore all non-types we find.  */
  if (lfi->want_type && TREE_CODE (nval) != TYPE_DECL
      && !DECL_CLASS_TEMPLATE_P (nval))
    {
      if (lfi->name == TYPE_IDENTIFIER (type))
	{
	  /* If the aggregate has no user defined constructors, we allow
	     it to have fields with the same name as the enclosing type.
	     If we are looking for that name, find the corresponding
	     TYPE_DECL.  */
	  for (nval = TREE_CHAIN (nval); nval; nval = TREE_CHAIN (nval))
	    if (DECL_NAME (nval) == lfi->name
		&& TREE_CODE (nval) == TYPE_DECL)
	      break;
	}
      else
	nval = NULL_TREE;
      if (!nval && CLASSTYPE_NESTED_UTDS (type) != NULL)
	{
          binding_entry e = binding_table_find (CLASSTYPE_NESTED_UTDS (type),
                                                lfi->name);
	  if (e != NULL)
	    nval = TYPE_MAIN_DECL (e->type);
	  else 
	    return NULL_TREE;
	}
    }

  /* You must name a template base class with a template-id.  */
  if (!same_type_p (type, lfi->type) 
      && template_self_reference_p (type, nval))
    return NULL_TREE;

  /* 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 && !original_binfo (lfi->rval_binfo, binfo))
    {
      if (nval == lfi->rval && shared_member_p (nval))
	/* The two things are really the same.  */
	;
      else if (original_binfo (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 = "request for member `%D' is ambiguous";
	}
    }
  else
    {
      lfi->rval = nval;
      lfi->rval_binfo = binfo;
    }

  return NULL_TREE;
}

/* Return a "baselink" which 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;

  my_friendly_assert (TREE_CODE (functions) == FUNCTION_DECL
		      || TREE_CODE (functions) == TEMPLATE_DECL
		      || TREE_CODE (functions) == TEMPLATE_ID_EXPR
		      || TREE_CODE (functions) == OVERLOAD,
		      20020730);
  my_friendly_assert (!optype || TYPE_P (optype), 20020730);
  my_friendly_assert (TREE_TYPE (functions), 20020805);

  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.  */

tree
lookup_member (tree xbasetype, tree name, int protect, bool want_type)
{
  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;

  my_friendly_assert (TREE_CODE (name) == IDENTIFIER_NODE, 20030624);

  if (TREE_CODE (xbasetype) == TREE_VEC)
    {
      type = BINFO_TYPE (xbasetype);
      basetype_path = xbasetype;
    }
  else
    {
      my_friendly_assert (IS_AGGR_TYPE_CODE (TREE_CODE (xbasetype)), 20030624);
      type = xbasetype;
      basetype_path = TYPE_BINFO (type);
      my_friendly_assert (!BINFO_INHERITANCE_CHAIN (basetype_path), 980827);
    }

  if (type == current_class_type && TYPE_BEING_DEFINED (type)
      && IDENTIFIER_CLASS_VALUE (name))
    {
      tree field = IDENTIFIER_CLASS_VALUE (name);
      if (! is_overloaded_fn (field)
	  && ! (want_type && TREE_CODE (field) != TYPE_DECL))
	/* We're in the scope of this class, and the value has already
	   been looked up.  Just return the cached value.  */
	return field;
    }

  complete_type (type);

#ifdef GATHER_STATISTICS
  n_calls_lookup_field++;
#endif /* GATHER_STATISTICS */

  memset (&lfi, 0, sizeof (lfi));
  lfi.type = type;
  lfi.name = name;
  lfi.want_type = want_type;
  bfs_walk (basetype_path, &lookup_field_r, &lookup_field_queue_p, &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.  */
  if (rval && protect && !is_overloaded_fn (rval))
    perform_or_defer_access_check (basetype_path, rval);

  if (errstr && protect)
    {
      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_TYPENAME_P (name)
			   ? TREE_TYPE (name): NULL_TREE));
  return rval;
}

/* 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);
  
  /* Ignore functions.  */
  if (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);

  /* Ignore non-functions.  */
  if (rval && !BASELINK_P (rval))
    return NULL_TREE;

  return rval;
}

/* Return the index in the CLASSTYPE_METHOD_VEC for CLASS_TYPE
   corresponding to "operator TYPE ()", or -1 if there is no such
   operator.  Only CLASS_TYPE itself is searched; this routine does
   not scan the base classes of CLASS_TYPE.  */

static int
lookup_conversion_operator (tree class_type, tree type)
{
  int pass;
  int i;

  tree methods = CLASSTYPE_METHOD_VEC (class_type);

  for (pass = 0; pass < 2; ++pass)
    for (i = CLASSTYPE_FIRST_CONVERSION_SLOT; 
	 i < TREE_VEC_LENGTH (methods);
	 ++i)
      {
	tree fn = TREE_VEC_ELT (methods, i);
	/* The size of the vector may have some unused slots at the
	   end.  */
	if (!fn)
	  break;

	/* All the conversion operators come near the beginning of the
	   class.  Therefore, if FN is not a conversion operator, there
	   is no matching conversion operator in CLASS_TYPE.  */
	fn = OVL_CURRENT (fn);
	if (!DECL_CONV_FN_P (fn))
	  break;
	
	if (pass == 0)
	  {
	    /* On the first pass we only consider exact matches.  If
	       the types match, this slot is the one where the right
	       conversion operators can be found.  */
	    if (TREE_CODE (fn) != TEMPLATE_DECL
		&& same_type_p (DECL_CONV_FN_TYPE (fn), type))
	      return i;
	  }
	else
	  {
	    /* On the second pass we look for template conversion
	       operators.  It may be possible to instantiate the
	       template to get the type desired.  All of the template
	       conversion operators share a slot.  By looking for
	       templates second we ensure that specializations are
	       preferred over templates.  */
	    if (TREE_CODE (fn) == TEMPLATE_DECL)
	      return i;
	  }
      }

  return -1;
}

/* TYPE is a class type. Return the index of the fields within
   the method vector with name NAME, or -1 is no such field exists.  */

int
lookup_fnfields_1 (tree type, tree name)
{
  tree method_vec;
  tree *methods;
  tree tmp;
  int i;
  int len;

  if (!CLASS_TYPE_P (type))
    return -1;

  method_vec = CLASSTYPE_METHOD_VEC (type);

  if (!method_vec)
    return -1;

  methods = &TREE_VEC_ELT (method_vec, 0);
  len = TREE_VEC_LENGTH (method_vec);

#ifdef GATHER_STATISTICS
  n_calls_lookup_fnfields_1++;
#endif /* GATHER_STATISTICS */

  /* Constructors are first...  */
  if (name == ctor_identifier)
    return (methods[CLASSTYPE_CONSTRUCTOR_SLOT] 
	    ? CLASSTYPE_CONSTRUCTOR_SLOT : -1);
  /* and destructors are second.  */
  if (name == dtor_identifier)
    return (methods[CLASSTYPE_DESTRUCTOR_SLOT]
	    ? CLASSTYPE_DESTRUCTOR_SLOT : -1);
  if (IDENTIFIER_TYPENAME_P (name))
    return lookup_conversion_operator (type, TREE_TYPE (name));

  /* Skip the conversion operators.  */
  i = CLASSTYPE_FIRST_CONVERSION_SLOT;
  while (i < len && methods[i] && DECL_CONV_FN_P (OVL_CURRENT (methods[i])))
    i++;

  /* If the type is complete, use binary search.  */
  if (COMPLETE_TYPE_P (type))
    {
      int lo = i;
      int hi = len;

      while (lo < hi)
	{
	  i = (lo + hi) / 2;

#ifdef GATHER_STATISTICS
	  n_outer_fields_searched++;
#endif /* GATHER_STATISTICS */

	  tmp = methods[i];
	  /* This slot may be empty; we allocate more slots than we
	     need.  In that case, the entry we're looking for is
	     closer to the beginning of the list.  */
	  if (tmp)
	    tmp = DECL_NAME (OVL_CURRENT (tmp));
	  if (!tmp || tmp > name)
	    hi = i;
	  else if (tmp < name)
	    lo = i + 1;
	  else
	    return i;
	}
    }
  else
    for (; i < len && methods[i]; ++i)
      {
#ifdef GATHER_STATISTICS
	n_outer_fields_searched++;
#endif /* GATHER_STATISTICS */
	
	tmp = OVL_CURRENT (methods[i]);
	if (DECL_NAME (tmp) == name)
	  return i;
      }

  return -1;
}

/* 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 && CLASS_TYPE_P (qualifying_scope) 
      && DERIVED_FROM_P (qualifying_scope, context_class)
      && BASELINK_P (decl))
    {
      tree base;

      my_friendly_assert (CLASS_TYPE_P (context_class), 20020808);

      /* 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_ignore | ba_quiet, NULL);
      if (base)
	{
	  BASELINK_ACCESS_BINFO (decl) = base;
	  BASELINK_BINFO (decl) 
	    = lookup_base (base, BINFO_TYPE (BASELINK_BINFO (decl)),
			   ba_ignore | ba_quiet,
			   NULL);
	}
    }

  return decl;
}


/* Walk the class hierarchy dominated by TYPE.  FN is called for each
   type in the hierarchy, in a breadth-first preorder traversal.
   If it ever returns a non-NULL value, that value is immediately
   returned and the walk is terminated.  At each node, FN is passed a
   BINFO indicating the path from the currently visited base-class to
   TYPE.  Before each base-class is walked QFN is called.  If the
   value returned is nonzero, the base-class is walked; otherwise it
   is not.  If QFN is NULL, it is treated as a function which always
   returns 1.  Both FN and QFN are passed the DATA whenever they are
   called.

   Implementation notes: Uses a circular queue, which starts off on
   the stack but gets moved to the malloc arena if it needs to be
   enlarged.  The underflow and overflow conditions are
   indistinguishable except by context: if head == tail and we just
   moved the head pointer, the queue is empty, but if we just moved
   the tail pointer, the queue is full.  
   Start with enough room for ten concurrent base classes.  That
   will be enough for most hierarchies.  */
#define BFS_WALK_INITIAL_QUEUE_SIZE 10

static tree
bfs_walk (tree binfo,
	  tree (*fn) (tree, void *),
	  tree (*qfn) (tree, int, void *),
	  void *data)
{
  tree rval = NULL_TREE;

  tree bases_initial[BFS_WALK_INITIAL_QUEUE_SIZE];
  /* A circular queue of the base classes of BINFO.  These will be
     built up in breadth-first order, except where QFN prunes the
     search.  */
  size_t head, tail;
  size_t base_buffer_size = BFS_WALK_INITIAL_QUEUE_SIZE;
  tree *base_buffer = bases_initial;

  head = tail = 0;
  base_buffer[tail++] = binfo;

  while (head != tail)
    {
      int n_bases, ix;
      tree binfo = base_buffer[head++];
      if (head == base_buffer_size)
	head = 0;

      /* Is this the one we're looking for?  If so, we're done.  */
      rval = fn (binfo, data);
      if (rval)
	goto done;

      n_bases = BINFO_N_BASETYPES (binfo);
      for (ix = 0; ix != n_bases; ix++)
	{
	  tree base_binfo;
	  
	  if (qfn)
	    base_binfo = (*qfn) (binfo, ix, data);
	  else
	    base_binfo = BINFO_BASETYPE (binfo, ix);
	  
 	  if (base_binfo)
	    {
	      base_buffer[tail++] = base_binfo;
	      if (tail == base_buffer_size)
		tail = 0;
	      if (tail == head)
		{
		  tree *new_buffer = xmalloc (2 * base_buffer_size
					      * sizeof (tree));
		  memcpy (&new_buffer[0], &base_buffer[0],
			  tail * sizeof (tree));
		  memcpy (&new_buffer[head + base_buffer_size],
			  &base_buffer[head],
			  (base_buffer_size - head) * sizeof (tree));
		  if (base_buffer_size != BFS_WALK_INITIAL_QUEUE_SIZE)
		    free (base_buffer);
		  base_buffer = new_buffer;
		  head += base_buffer_size;
		  base_buffer_size *= 2;
		}
	    }
	}
    }

 done:
  if (base_buffer_size != BFS_WALK_INITIAL_QUEUE_SIZE)
    free (base_buffer);
  return rval;
}

/* Exactly like bfs_walk, except that a depth-first traversal is
   performed, and PREFN is called in preorder, while POSTFN is called
   in postorder.  */

tree
dfs_walk_real (tree binfo,
	       tree (*prefn) (tree, void *),
	       tree (*postfn) (tree, void *),
	       tree (*qfn) (tree, int, void *),
	       void *data)
{
  tree rval = NULL_TREE;

  /* Call the pre-order walking function.  */
  if (prefn)
    {
      rval = (*prefn) (binfo, data);
      if (rval)
	return rval;
    }

  /* Process the basetypes.  */
  if (BINFO_BASETYPES (binfo))
    {
      int i, n = TREE_VEC_LENGTH (BINFO_BASETYPES (binfo));
      for (i = 0; i != n; i++)
	{
	  tree base_binfo;
      
	  if (qfn)
	    base_binfo = (*qfn) (binfo, i, data);
	  else
	    base_binfo = BINFO_BASETYPE (binfo, i);
	  
	  if (base_binfo)
	    {
	      rval = dfs_walk_real (base_binfo, prefn, postfn, qfn, data);
	      if (rval)
		return rval;
	    }
	}
    }

  /* Call the post-order walking function.  */
  if (postfn)
    rval = (*postfn) (binfo, data);
  
  return rval;
}

/* Exactly like bfs_walk, except that a depth-first post-order traversal is
   performed.  */

tree
dfs_walk (tree binfo,
	  tree (*fn) (tree, void *),
	  tree (*qfn) (tree, int, void *),
	  void *data)
{
  return dfs_walk_real (binfo, 0, fn, qfn, data);
}

/* Check that virtual overrider OVERRIDER is acceptable for base function
   BASEFN. Issue diagnostic, and return zero, if unacceptable.  */

int
check_final_overrider (tree overrider, tree basefn)
{
  tree over_type = TREE_TYPE (overrider);
  tree base_type = TREE_TYPE (basefn);
  tree over_return = TREE_TYPE (over_type);
  tree base_return = TREE_TYPE (base_type);
  tree over_throw = TYPE_RAISES_EXCEPTIONS (over_type);
  tree base_throw = TYPE_RAISES_EXCEPTIONS (base_type);
  int fail = 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))
	{
	  tree binfo = lookup_base (over_return, base_return,
				    ba_check | ba_quiet, NULL);

	  if (!binfo)
	    fail = 1;
	}
      else if (!pedantic
	       && can_convert (TREE_TYPE (base_type), TREE_TYPE (over_type)))
	/* GNU extension, allow trivial pointer conversions such as
	   converting to void *, or qualification conversion.  */
	{
	  /* can_convert will permit user defined conversion from a
	     (reference to) class type. We must reject them.  */
	  over_return = non_reference (TREE_TYPE (over_type));
	  if (CLASS_TYPE_P (over_return))
	    fail = 2;
	}
      else
	fail = 2;
    }
  else
    fail = 2;
  if (!fail)
    /* OK */;
  else if (IDENTIFIER_ERROR_LOCUS (DECL_ASSEMBLER_NAME (overrider)))
    return 0;
  else
    {
      if (fail == 1)
	{
	  cp_error_at ("invalid covariant return type for `%#D'", overrider);
	  cp_error_at ("  overriding `%#D'", basefn);
	}
      else
	{
	  cp_error_at ("conflicting return type specified for `%#D'",
		       overrider);
	  cp_error_at ("  overriding `%#D'", basefn);
	}
      SET_IDENTIFIER_ERROR_LOCUS (DECL_ASSEMBLER_NAME (overrider),
                                  DECL_CONTEXT (overrider));
      return 0;
    }
  
  /* Check throw specifier is at least as strict.  */
  if (!comp_except_specs (base_throw, over_throw, 0))
    {
      if (!IDENTIFIER_ERROR_LOCUS (DECL_ASSEMBLER_NAME (overrider)))
	{
	  cp_error_at ("looser throw specifier for `%#F'", overrider);
	  cp_error_at ("  overriding `%#F'", basefn);
	  SET_IDENTIFIER_ERROR_LOCUS (DECL_ASSEMBLER_NAME (overrider),
				      DECL_CONTEXT (overrider));
	}
      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 basebinfos = BINFO_BASETYPES (binfo);
  int nbasebinfos = basebinfos ? TREE_VEC_LENGTH (basebinfos) : 0;
  int ix;
  int found = 0;

  for (ix = 0; ix != nbasebinfos; ix++)
    {
      tree basetype = BINFO_TYPE (TREE_VEC_ELT (basebinfos, ix));
      
      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)
{
  int ix;

  if (DECL_MAYBE_IN_CHARGE_DESTRUCTOR_P (fndecl))
    ix = CLASSTYPE_DESTRUCTOR_SLOT;
  else
    ix = lookup_fnfields_1 (type, DECL_NAME (fndecl));
  if (ix >= 0)
    {
      tree fns = TREE_VEC_ELT (CLASSTYPE_METHOD_VEC (type), ix);
  
      for (; fns; fns = OVL_NEXT (fns))
        {
          tree fn = OVL_CURRENT (fns);

          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.  */
	  cp_error_at ("`%#D' cannot be declared", fndecl);
	  cp_error_at ("  since `%#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)))
	  CLASSTYPE_PURE_VIRTUALS (type) 
	    = tree_cons (NULL_TREE, BV_FN (virtuals),
			 CLASSTYPE_PURE_VIRTUALS (type));
    }
  
  BINFO_MARKED (binfo) = 1;

  return NULL_TREE;
}

/* Set CLASSTYPE_PURE_VIRTUALS for TYPE.  */

void
get_pure_virtuals (tree type)
{
  tree vbases;

  /* Clear the CLASSTYPE_PURE_VIRTUALS list; whatever is already there
     is going to be overridden.  */
  CLASSTYPE_PURE_VIRTUALS (type) = NULL_TREE;
  /* 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 (TYPE_BINFO (type), dfs_get_pure_virtuals, unmarkedp, type);
  dfs_walk (TYPE_BINFO (type), dfs_unmark, markedp, type);

  /* Put the pure virtuals in dfs order.  */
  CLASSTYPE_PURE_VIRTUALS (type) = nreverse (CLASSTYPE_PURE_VIRTUALS (type));

  for (vbases = CLASSTYPE_VBASECLASSES (type); 
       vbases; 
       vbases = TREE_CHAIN (vbases))
    {
      tree virtuals;

      for (virtuals = BINFO_VIRTUALS (TREE_VALUE (vbases));
	   virtuals;
	   virtuals = TREE_CHAIN (virtuals))
	{
	  tree base_fndecl = BV_FN (virtuals);
	  if (DECL_NEEDS_FINAL_OVERRIDER_P (base_fndecl))
	    error ("`%#D' needs a final overrider", base_fndecl);
	}
    }
}

/* DEPTH-FIRST SEARCH ROUTINES.  */

tree 
markedp (tree derived, int ix, void *data ATTRIBUTE_UNUSED) 
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  return BINFO_MARKED (binfo) ? binfo : NULL_TREE; 
}

tree
unmarkedp (tree derived, int ix, void *data ATTRIBUTE_UNUSED) 
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  return !BINFO_MARKED (binfo) ? binfo : NULL_TREE; 
}

static tree
marked_pushdecls_p (tree derived, int ix, void *data ATTRIBUTE_UNUSED)
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  return (!BINFO_DEPENDENT_BASE_P (binfo)
	  && BINFO_PUSHDECLS_MARKED (binfo)) ? binfo : NULL_TREE; 
}

static tree
unmarked_pushdecls_p (tree derived, int ix, void *data ATTRIBUTE_UNUSED)
{ 
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  return (!BINFO_DEPENDENT_BASE_P (binfo)
	  && !BINFO_PUSHDECLS_MARKED (binfo)) ? binfo : NULL_TREE;
}

/* The worker functions for `dfs_walk'.  These do not need to
   test anything (vis a vis marking) if they are paired with
   a predicate function (above).  */

tree
dfs_unmark (tree binfo, void *data ATTRIBUTE_UNUSED)
{
  BINFO_MARKED (binfo) = 0;
  return NULL_TREE;
}


/* 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)
{
  /* We can't do the usual TYPE_DECL_SUPPRESS_DEBUG thing with DWARF, which
     does not support name references between translation units.  It supports
     symbolic references between translation units, but only within a single
     executable or shared library.

     For DWARF 2, we handle TYPE_DECL_SUPPRESS_DEBUG by pretending
     that the type was never defined, so we only get the members we
     actually define.  */
  if (write_symbols == DWARF_DEBUG || write_symbols == NO_DEBUG)
    return;

  /* We might have set this earlier in cp_finish_decl.  */
  TYPE_DECL_SUPPRESS_DEBUG (TYPE_MAIN_DECL (t)) = 0;

  /* 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 ATTRIBUTE_UNUSED)
{
  tree t = BINFO_TYPE (binfo);

  CLASSTYPE_DEBUG_REQUESTED (t) = 1;

  return NULL_TREE;
}

/* Returns BINFO if we haven't already noted that we want debugging
   info for this base class.  */

static tree 
dfs_debug_unmarkedp (tree derived, int ix, void *data ATTRIBUTE_UNUSED)
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  
  return (!CLASSTYPE_DEBUG_REQUESTED (BINFO_TYPE (binfo)) 
	  ? binfo : 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, toplevel_bindings_p ());
    }

  dfs_walk (TYPE_BINFO (type), dfs_debug_mark, dfs_debug_unmarkedp, 0);
}

/* Subroutines of push_class_decls ().  */

static void
setup_class_bindings (tree name, int type_binding_p)
{
  tree type_binding = NULL_TREE;
  tree value_binding;

  /* If we've already done the lookup for this declaration, we're
     done.  */
  if (IDENTIFIER_CLASS_VALUE (name))
    return;

  /* First, deal with the type binding.  */
  if (type_binding_p)
    {
      type_binding = lookup_member (current_class_type, name,
				    /*protect=*/2, /*want_type=*/true);
      if (TREE_CODE (type_binding) == TREE_LIST 
	  && TREE_TYPE (type_binding) == error_mark_node)
	/* NAME is ambiguous.  */
	push_class_level_binding (name, type_binding);
      else
	pushdecl_class_level (type_binding);
    }

  /* Now, do the value binding.  */
  value_binding = lookup_member (current_class_type, name,
				 /*protect=*/2, /*want_type=*/false);

  if (type_binding_p
      && (TREE_CODE (value_binding) == TYPE_DECL
	  || DECL_CLASS_TEMPLATE_P (value_binding)
	  || (TREE_CODE (value_binding) == TREE_LIST
	      && TREE_TYPE (value_binding) == error_mark_node
	      && (TREE_CODE (TREE_VALUE (value_binding))
		  == TYPE_DECL))))
    /* We found a type-binding, even when looking for a non-type
       binding.  This means that we already processed this binding
       above.  */;
  else if (value_binding)
    {
      if (TREE_CODE (value_binding) == TREE_LIST 
	  && TREE_TYPE (value_binding) == error_mark_node)
	/* NAME is ambiguous.  */
	push_class_level_binding (name, value_binding);
      else
	{
	  if (BASELINK_P (value_binding))
	    /* NAME is some overloaded functions.  */
	    value_binding = BASELINK_FUNCTIONS (value_binding);
	  /* Two conversion operators that convert to the same type
	     may have different names.  (See
	     mangle_conv_op_name_for_type.)  To avoid recording the
	     same conversion operator declaration more than once we
	     must check to see that the same operator was not already
	     found under another name.  */
	  if (IDENTIFIER_TYPENAME_P (name)
	      && is_overloaded_fn (value_binding))
	    {
	      tree fns;
	      for (fns = value_binding; fns; fns = OVL_NEXT (fns))
		if (IDENTIFIER_CLASS_VALUE (DECL_NAME (OVL_CURRENT (fns))))
		  return;
	    }
	  pushdecl_class_level (value_binding);
	}
    }
}

/* Push class-level declarations for any names appearing in BINFO that
   are TYPE_DECLS.  */

static tree
dfs_push_type_decls (tree binfo, void *data ATTRIBUTE_UNUSED)
{
  tree type;
  tree fields;

  type = BINFO_TYPE (binfo);
  for (fields = TYPE_FIELDS (type); fields; fields = TREE_CHAIN (fields))
    if (DECL_NAME (fields) && TREE_CODE (fields) == TYPE_DECL
	&& !(!same_type_p (type, current_class_type)
	     && template_self_reference_p (type, fields)))
      setup_class_bindings (DECL_NAME (fields), /*type_binding_p=*/1);

  /* We can't just use BINFO_MARKED because envelope_add_decl uses
     DERIVED_FROM_P, which calls get_base_distance.  */
  BINFO_PUSHDECLS_MARKED (binfo) = 1;

  return NULL_TREE;
}

/* Push class-level declarations for any names appearing in BINFO that
   are not TYPE_DECLS.  */

static tree
dfs_push_decls (tree binfo, void *data)
{
  tree type = BINFO_TYPE (binfo);
  tree method_vec;
  tree fields;
  
  for (fields = TYPE_FIELDS (type); fields; fields = TREE_CHAIN (fields))
    if (DECL_NAME (fields) 
	&& TREE_CODE (fields) != TYPE_DECL
	&& TREE_CODE (fields) != USING_DECL
	&& !DECL_ARTIFICIAL (fields))
      setup_class_bindings (DECL_NAME (fields), /*type_binding_p=*/0);
    else if (TREE_CODE (fields) == FIELD_DECL
	     && ANON_AGGR_TYPE_P (TREE_TYPE (fields)))
      dfs_push_decls (TYPE_BINFO (TREE_TYPE (fields)), data);
  
  method_vec = (CLASS_TYPE_P (type) 
		? CLASSTYPE_METHOD_VEC (type) : NULL_TREE);
  
  if (method_vec && TREE_VEC_LENGTH (method_vec) >= 3)
    {
      tree *methods;
      tree *end;
      
      /* Farm out constructors and destructors.  */
      end = TREE_VEC_END (method_vec);
      
      for (methods = &TREE_VEC_ELT (method_vec, 2);
	   methods < end && *methods;
	   methods++)
	setup_class_bindings (DECL_NAME (OVL_CURRENT (*methods)), 
			      /*type_binding_p=*/0);
    }

  BINFO_PUSHDECLS_MARKED (binfo) = 0;

  return NULL_TREE;
}

/* When entering the scope of a class, we cache all of the
   fields that that class provides within its inheritance
   lattice.  Where ambiguities result, we mark them
   with `error_mark_node' so that if they are encountered
   without explicit qualification, we can emit an error
   message.  */

void
push_class_decls (tree type)
{
  search_stack = push_search_level (search_stack, &search_obstack);

  /* Enter type declarations and mark.  */
  dfs_walk (TYPE_BINFO (type), dfs_push_type_decls, unmarked_pushdecls_p, 0);

  /* Enter non-type declarations and unmark.  */
  dfs_walk (TYPE_BINFO (type), dfs_push_decls, marked_pushdecls_p, 0);
}

/* Here's a subroutine we need because C lacks lambdas.  */

static tree
dfs_unuse_fields (tree binfo, void *data ATTRIBUTE_UNUSED)
{
  tree type = TREE_TYPE (binfo);
  tree fields;

  for (fields = TYPE_FIELDS (type); fields; fields = TREE_CHAIN (fields))
    {
      if (TREE_CODE (fields) != FIELD_DECL || DECL_ARTIFICIAL (fields))
	continue;

      TREE_USED (fields) = 0;
      if (DECL_NAME (fields) == NULL_TREE
	  && ANON_AGGR_TYPE_P (TREE_TYPE (fields)))
	unuse_fields (TREE_TYPE (fields));
    }

  return NULL_TREE;
}

void
unuse_fields (tree type)
{
  dfs_walk (TYPE_BINFO (type), dfs_unuse_fields, unmarkedp, 0);
}

void
pop_class_decls (void)
{
  /* We haven't pushed a search level when dealing with cached classes,
     so we'd better not try to pop it.  */
  if (search_stack)
    search_stack = pop_search_level (search_stack);
}

void
print_search_statistics (void)
{
#ifdef GATHER_STATISTICS
  fprintf (stderr, "%d fields searched in %d[%d] calls to lookup_field[_1]\n",
	   n_fields_searched, n_calls_lookup_field, n_calls_lookup_field_1);
  fprintf (stderr, "%d fnfields searched in %d calls to lookup_fnfields\n",
	   n_outer_fields_searched, n_calls_lookup_fnfields);
  fprintf (stderr, "%d calls to get_base_type\n", n_calls_get_base_type);
#else /* GATHER_STATISTICS */
  fprintf (stderr, "no search statistics\n");
#endif /* GATHER_STATISTICS */
}

void
init_search_processing (void)
{
  gcc_obstack_init (&search_obstack);
}

void
reinit_search_statistics (void)
{
#ifdef GATHER_STATISTICS
  n_fields_searched = 0;
  n_calls_lookup_field = 0, n_calls_lookup_field_1 = 0;
  n_calls_lookup_fnfields = 0, n_calls_lookup_fnfields_1 = 0;
  n_calls_get_base_type = 0;
  n_outer_fields_searched = 0;
  n_contexts_saved = 0;
#endif /* GATHER_STATISTICS */
}

static tree
add_conversions (tree binfo, void *data)
{
  int i;
  tree method_vec = CLASSTYPE_METHOD_VEC (BINFO_TYPE (binfo));
  tree *conversions = (tree *) data;

  /* Some builtin types have no method vector, not even an empty one.  */
  if (!method_vec)
    return NULL_TREE;

  for (i = 2; i < TREE_VEC_LENGTH (method_vec); ++i)
    {
      tree tmp = TREE_VEC_ELT (method_vec, i);
      tree name;

      if (!tmp || ! DECL_CONV_FN_P (OVL_CURRENT (tmp)))
	break;

      name = DECL_NAME (OVL_CURRENT (tmp));

      /* Make sure we don't already have this conversion.  */
      if (! IDENTIFIER_MARKED (name))
	{
	  tree t;

	  /* Make sure that we do not already have a conversion
	     operator for this type.  Merely checking the NAME is not
	     enough because two conversion operators to the same type
	     may not have the same NAME.  */
	  for (t = *conversions; t; t = TREE_CHAIN (t))
	    {
	      tree fn;
	      for (fn = TREE_VALUE (t); fn; fn = OVL_NEXT (fn))
		if (same_type_p (TREE_TYPE (name),
				 DECL_CONV_FN_TYPE (OVL_CURRENT (fn))))
		  break;
	      if (fn)
		break;
	    }
	  if (!t)
	    {
	      *conversions = tree_cons (binfo, tmp, *conversions);
	      IDENTIFIER_MARKED (name) = 1;
	    }
	}
    }
  return NULL_TREE;
}

/* 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 a FUNCTION_DECL or an OVERLOAD
   containing the conversion functions.  The TREE_PURPOSE is the BINFO
   from which the conversion functions in this node were selected.  */

tree
lookup_conversions (tree type)
{
  tree t;
  tree conversions = NULL_TREE;

  complete_type (type);
  bfs_walk (TYPE_BINFO (type), add_conversions, 0, &conversions);

  for (t = conversions; t; t = TREE_CHAIN (t))
    IDENTIFIER_MARKED (DECL_NAME (OVL_CURRENT (TREE_VALUE (t)))) = 0;

  return conversions;
}

struct overlap_info 
{
  tree compare_type;
  int found_overlap;
};

/* Check whether the empty class indicated by EMPTY_BINFO is also present
   at offset 0 in COMPARE_TYPE, and set found_overlap if so.  */

static tree
dfs_check_overlap (tree empty_binfo, void *data)
{
  struct overlap_info *oi = (struct overlap_info *) data;
  tree binfo;
  for (binfo = TYPE_BINFO (oi->compare_type); 
       ; 
       binfo = BINFO_BASETYPE (binfo, 0))
    {
      if (BINFO_TYPE (binfo) == BINFO_TYPE (empty_binfo))
	{
	  oi->found_overlap = 1;
	  break;
	}
      else if (BINFO_BASETYPES (binfo) == NULL_TREE)
	break;
    }

  return NULL_TREE;
}

/* Trivial function to stop base traversal when we find something.  */

static tree
dfs_no_overlap_yet (tree derived, int ix, void *data)
{
  tree binfo = BINFO_BASETYPE (derived, ix);
  struct overlap_info *oi = (struct overlap_info *) data;
  
  return !oi->found_overlap ? binfo : NULL_TREE;
}

/* Returns nonzero if EMPTY_TYPE or any of its bases can also be found at
   offset 0 in NEXT_TYPE.  Used in laying out empty base class subobjects.  */

int
types_overlap_p (tree empty_type, tree next_type)
{
  struct overlap_info oi;

  if (! IS_AGGR_TYPE (next_type))
    return 0;
  oi.compare_type = next_type;
  oi.found_overlap = 0;
  dfs_walk (TYPE_BINFO (empty_type), dfs_check_overlap,
	    dfs_no_overlap_yet, &oi);
  return oi.found_overlap;
}

/* Given a vtable VAR, determine which of the inherited classes the vtable
   inherits (in a loose sense) functions from.

   FIXME: This does not work with the new ABI.  */

tree
binfo_for_vtable (tree var)
{
  tree main_binfo = TYPE_BINFO (DECL_CONTEXT (var));
  tree binfos = TYPE_BINFO_BASETYPES (BINFO_TYPE (main_binfo));
  int n_baseclasses = CLASSTYPE_N_BASECLASSES (BINFO_TYPE (main_binfo));
  int i;

  for (i = 0; i < n_baseclasses; i++)
    {
      tree base_binfo = TREE_VEC_ELT (binfos, i);
      if (base_binfo != NULL_TREE && BINFO_VTABLE (base_binfo) == var)
	return base_binfo;
    }

  /* If no secondary base classes matched, return the primary base, if
     there is one.  */
  if (CLASSTYPE_HAS_PRIMARY_BASE_P (BINFO_TYPE (main_binfo)))
    return get_primary_binfo (main_binfo);

  return main_binfo;
}

/* 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 (TREE_VIA_VIRTUAL (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)
{
  for (; binfo && (!limit || !same_type_p (BINFO_TYPE (binfo), limit));
       binfo = BINFO_INHERITANCE_CHAIN (binfo))
    {
      if (TREE_VIA_VIRTUAL (binfo))
	return binfo;
    }
  return NULL_TREE;
}

/* 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 (TREE_VIA_VIRTUAL (binfo))
    {
      tree t;

      for (t = here; BINFO_INHERITANCE_CHAIN (t);
	   t = BINFO_INHERITANCE_CHAIN (t))
	continue;
      
      result = purpose_member (BINFO_TYPE (binfo),
			       CLASSTYPE_VBASECLASSES (BINFO_TYPE (t)));
      result = TREE_VALUE (result);
    }
  else if (BINFO_INHERITANCE_CHAIN (binfo))
    {
      tree base_binfos;
      int ix, n;
      
      base_binfos = copied_binfo (BINFO_INHERITANCE_CHAIN (binfo), here);
      base_binfos = BINFO_BASETYPES (base_binfos);
      n = TREE_VEC_LENGTH (base_binfos);
      for (ix = 0; ix != n; ix++)
	{
	  tree base = TREE_VEC_ELT (base_binfos, ix);
	  
	  if (BINFO_TYPE (base) == BINFO_TYPE (binfo))
	    {
	      result = base;
	      break;
	    }
	}
    }
  else
    {
      my_friendly_assert (BINFO_TYPE (here) == BINFO_TYPE (binfo), 20030202);
      result = here;
    }

  my_friendly_assert (result, 20030202);
  return result;
}

/* 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 (BINFO_TYPE (binfo) == BINFO_TYPE (here))
    result = here;
  else if (TREE_VIA_VIRTUAL (binfo))
    {
      result = purpose_member (BINFO_TYPE (binfo),
			       CLASSTYPE_VBASECLASSES (BINFO_TYPE (here)));
      if (result)
	result = TREE_VALUE (result);
    }
  else if (BINFO_INHERITANCE_CHAIN (binfo))
    {
      tree base_binfos;
      
      base_binfos = original_binfo (BINFO_INHERITANCE_CHAIN (binfo), here);
      if (base_binfos)
	{
	  int ix, n;
	  
	  base_binfos = BINFO_BASETYPES (base_binfos);
	  n = TREE_VEC_LENGTH (base_binfos);
	  for (ix = 0; ix != n; ix++)
	    {
	      tree base = TREE_VEC_ELT (base_binfos, ix);
	      
	      if (BINFO_TYPE (base) == BINFO_TYPE (binfo))
		{
		  result = base;
		  break;
		}
	    }
	}
    }
  
  return result;
}