[thirdparty/gcc.git] / libstdc++-v3 / libsupc++ / vmi_class_type_info.cc

// Copyright (C) 1994, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2007, 2009
// Free Software Foundation
//
// 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.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

#include "tinfo.h"

namespace __cxxabiv1 {

__vmi_class_type_info::
~__vmi_class_type_info ()
{}

__class_type_info::__sub_kind __vmi_class_type_info::
__do_find_public_src (ptrdiff_t src2dst,
                      const void *obj_ptr,
                      const __class_type_info *src_type,
                      const void *src_ptr) const
{
  if (obj_ptr == src_ptr && *this == *src_type)
    return __contained_public;
  
  for (std::size_t i = __base_count; i--;)
    {
      if (!__base_info[i].__is_public_p ())
        continue; // Not public, can't be here.
      
      const void *base = obj_ptr;
      ptrdiff_t offset = __base_info[i].__offset ();
      bool is_virtual = __base_info[i].__is_virtual_p ();
      
      if (is_virtual)
        {
          if (src2dst == -3)
            continue; // Not a virtual base, so can't be here.
        }
      base = convert_to_base (base, is_virtual, offset);
      
      __sub_kind base_kind = __base_info[i].__base_type->__do_find_public_src
                              (src2dst, base, src_type, src_ptr);
      if (contained_p (base_kind))
        {
          if (is_virtual)
            base_kind = __sub_kind (base_kind | __contained_virtual_mask);
          return base_kind;
        }
    }
  
  return __not_contained;
}

// This is a big hairy function. Although the run-time behaviour of
// dynamic_cast is simple to describe, it gives rise to some non-obvious
// behaviour. We also desire to determine as early as possible any definite
// answer we can get. Because it is unknown what the run-time ratio of
// succeeding to failing dynamic casts is, we do not know in which direction
// to bias any optimizations. To that end we make no particular effort towards
// early fail answers or early success answers. Instead we try to minimize
// work by filling in things lazily (when we know we need the information),
// and opportunisticly take early success or failure results.
bool __vmi_class_type_info::
__do_dyncast (ptrdiff_t src2dst,
              __sub_kind access_path,
              const __class_type_info *dst_type,
              const void *obj_ptr,
              const __class_type_info *src_type,
              const void *src_ptr,
              __dyncast_result &__restrict result) const
{
  if (result.whole_details & __flags_unknown_mask)
    result.whole_details = __flags;
  
  if (obj_ptr == src_ptr && *this == *src_type)
    {
      // The src object we started from. Indicate how we are accessible from
      // the most derived object.
      result.whole2src = access_path;
      return false;
    }
  if (*this == *dst_type)
    {
      result.dst_ptr = obj_ptr;
      result.whole2dst = access_path;
      if (src2dst >= 0)
        result.dst2src = adjust_pointer <void> (obj_ptr, src2dst) == src_ptr
              ? __contained_public : __not_contained;
      else if (src2dst == -2)
        result.dst2src = __not_contained;
      return false;
    }

  bool result_ambig = false;
  for (std::size_t i = __base_count; i--;)
    {
      __dyncast_result result2 (result.whole_details);
      void const *base = obj_ptr;
      __sub_kind base_access = access_path;
      ptrdiff_t offset = __base_info[i].__offset ();
      bool is_virtual = __base_info[i].__is_virtual_p ();
      
      if (is_virtual)
        base_access = __sub_kind (base_access | __contained_virtual_mask);
      base = convert_to_base (base, is_virtual, offset);

      if (!__base_info[i].__is_public_p ())
        {
          if (src2dst == -2 &&
              !(result.whole_details
                & (__non_diamond_repeat_mask | __diamond_shaped_mask)))
            // The hierarchy has no duplicate bases (which might ambiguate
            // things) and where we started is not a public base of what we
            // want (so it cannot be a downcast). There is nothing of interest
            // hiding in a non-public base.
            continue;
          base_access = __sub_kind (base_access & ~__contained_public_mask);
        }
      
      bool result2_ambig
          = __base_info[i].__base_type->__do_dyncast (src2dst, base_access,
                                             dst_type, base,
                                             src_type, src_ptr, result2);
      result.whole2src = __sub_kind (result.whole2src | result2.whole2src);
      if (result2.dst2src == __contained_public
          || result2.dst2src == __contained_ambig)
        {
          result.dst_ptr = result2.dst_ptr;
          result.whole2dst = result2.whole2dst;
          result.dst2src = result2.dst2src;
          // Found a downcast which can't be bettered or an ambiguous downcast
          // which can't be disambiguated
          return result2_ambig;
        }
      
      if (!result_ambig && !result.dst_ptr)
        {
          // Not found anything yet.
          result.dst_ptr = result2.dst_ptr;
          result.whole2dst = result2.whole2dst;
          result_ambig = result2_ambig;
          if (result.dst_ptr && result.whole2src != __unknown
              && !(__flags & __non_diamond_repeat_mask))
            // Found dst and src and we don't have repeated bases.
            return result_ambig;
        }
      else if (result.dst_ptr && result.dst_ptr == result2.dst_ptr)
        {
          // Found at same address, must be via virtual.  Pick the most
          // accessible path.
          result.whole2dst =
              __sub_kind (result.whole2dst | result2.whole2dst);
        }
      else if ((result.dst_ptr != 0 && result2.dst_ptr != 0)
	       || (result.dst_ptr != 0 && result2_ambig)
	       || (result2.dst_ptr != 0 && result_ambig))
        {
          // Found two different DST_TYPE bases, or a valid one and a set of
          // ambiguous ones, must disambiguate. See whether SRC_PTR is
          // contained publicly within one of the non-ambiguous choices. If it
          // is in only one, then that's the choice. If it is in both, then
          // we're ambiguous and fail. If it is in neither, we're ambiguous,
          // but don't yet fail as we might later find a third base which does
          // contain SRC_PTR.
        
          __sub_kind new_sub_kind = result2.dst2src;
          __sub_kind old_sub_kind = result.dst2src;
          
          if (contained_p (result.whole2src)
              && (!virtual_p (result.whole2src)
                  || !(result.whole_details & __diamond_shaped_mask)))
            {
              // We already found SRC_PTR as a base of most derived, and
              // either it was non-virtual, or the whole hierarchy is
              // not-diamond shaped. Therefore if it is in either choice, it
              // can only be in one of them, and we will already know.
              if (old_sub_kind == __unknown)
                old_sub_kind = __not_contained;
              if (new_sub_kind == __unknown)
                new_sub_kind = __not_contained;
            }
          else
            {
              if (old_sub_kind >= __not_contained)
                ;// already calculated
              else if (contained_p (new_sub_kind)
                       && (!virtual_p (new_sub_kind)
                           || !(__flags & __diamond_shaped_mask)))
                // Already found inside the other choice, and it was
                // non-virtual or we are not diamond shaped.
                old_sub_kind = __not_contained;
              else
                old_sub_kind = dst_type->__find_public_src
                                (src2dst, result.dst_ptr, src_type, src_ptr);
          
              if (new_sub_kind >= __not_contained)
                ;// already calculated
              else if (contained_p (old_sub_kind)
                       && (!virtual_p (old_sub_kind)
                           || !(__flags & __diamond_shaped_mask)))
                // Already found inside the other choice, and it was
                // non-virtual or we are not diamond shaped.
                new_sub_kind = __not_contained;
              else
                new_sub_kind = dst_type->__find_public_src
                                (src2dst, result2.dst_ptr, src_type, src_ptr);
            }
          
          // Neither sub_kind can be contained_ambig -- we bail out early
          // when we find those.
          if (contained_p (__sub_kind (new_sub_kind ^ old_sub_kind)))
            {
              // Only on one choice, not ambiguous.
              if (contained_p (new_sub_kind))
                {
                  // Only in new.
                  result.dst_ptr = result2.dst_ptr;
                  result.whole2dst = result2.whole2dst;
                  result_ambig = false;
                  old_sub_kind = new_sub_kind;
                }
              result.dst2src = old_sub_kind;
              if (public_p (result.dst2src))
                return false; // Can't be an ambiguating downcast for later discovery.
              if (!virtual_p (result.dst2src))
                return false; // Found non-virtually can't be bettered
            }
          else if (contained_p (__sub_kind (new_sub_kind & old_sub_kind)))
            {
              // In both.
              result.dst_ptr = NULL;
              result.dst2src = __contained_ambig;
              return true;  // Fail.
            }
          else
            {
              // In neither publicly, ambiguous for the moment, but keep
              // looking. It is possible that it was private in one or
              // both and therefore we should fail, but that's just tough.
              result.dst_ptr = NULL;
              result.dst2src = __not_contained;
              result_ambig = true;
            }
        }
      
      if (result.whole2src == __contained_private)
        // We found SRC_PTR as a private non-virtual base, therefore all
        // cross casts will fail. We have already found a down cast, if
        // there is one.
        return result_ambig;
    }

  return result_ambig;
}

bool __vmi_class_type_info::
__do_upcast (const __class_type_info *dst, const void *obj_ptr,
             __upcast_result &__restrict result) const
{
  if (__class_type_info::__do_upcast (dst, obj_ptr, result))
    return true;
  
  int src_details = result.src_details;
  if (src_details & __flags_unknown_mask)
    src_details = __flags;
  
  for (std::size_t i = __base_count; i--;)
    {
      __upcast_result result2 (src_details);
      const void *base = obj_ptr;
      ptrdiff_t offset = __base_info[i].__offset ();
      bool is_virtual = __base_info[i].__is_virtual_p ();
      bool is_public = __base_info[i].__is_public_p ();
      
      if (!is_public && !(src_details & __non_diamond_repeat_mask))
        // original cannot have an ambiguous base, so skip private bases
        continue;

      if (base)
        base = convert_to_base (base, is_virtual, offset);
      
      if (__base_info[i].__base_type->__do_upcast (dst, base, result2))
        {
          if (result2.base_type == nonvirtual_base_type && is_virtual)
            result2.base_type = __base_info[i].__base_type;
          if (contained_p (result2.part2dst) && !is_public)
            result2.part2dst = __sub_kind (result2.part2dst & ~__contained_public_mask);
          
          if (!result.base_type)
            {
              result = result2;
              if (!contained_p (result.part2dst))
                return true; // found ambiguously
              
              if (result.part2dst & __contained_public_mask)
                {
                  if (!(__flags & __non_diamond_repeat_mask))
                    return true;  // cannot have an ambiguous other base
                }
              else
                {
                  if (!virtual_p (result.part2dst))
                    return true; // cannot have another path
                  if (!(__flags & __diamond_shaped_mask))
                    return true; // cannot have a more accessible path
                }
            }
          else if (result.dst_ptr != result2.dst_ptr)
            {
              // Found an ambiguity.
	      result.dst_ptr = NULL;
	      result.part2dst = __contained_ambig;
	      return true;
            }
          else if (result.dst_ptr)
            {
              // Ok, found real object via a virtual path.
              result.part2dst
                  = __sub_kind (result.part2dst | result2.part2dst);
            }
          else
            {
              // Dealing with a null pointer, need to check vbase
              // containing each of the two choices.
              if (result2.base_type == nonvirtual_base_type
                  || result.base_type == nonvirtual_base_type
                  || !(*result2.base_type == *result.base_type))
                {
                  // Already ambiguous, not virtual or via different virtuals.
                  // Cannot match.
                  result.part2dst = __contained_ambig;
                  return true;
                }
              result.part2dst
                  = __sub_kind (result.part2dst | result2.part2dst);
            }
        }
    }
  return result.part2dst != __unknown;
}

}
Commit	Line	Data
748086b7	1	// Copyright (C) 1994, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2007, 2009
bd994a48 MM	2	// Free Software Foundation
	3	//
	4	// This file is part of GCC.
	5	//
	6	// GCC is free software; you can redistribute it and/or modify
	7	// it under the terms of the GNU General Public License as published by
748086b7	8	// the Free Software Foundation; either version 3, or (at your option)
bd994a48 MM	9	// any later version.
	10
	11	// GCC is distributed in the hope that it will be useful,
	12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	// GNU General Public License for more details.
	15
748086b7 JJ	16	// Under Section 7 of GPL version 3, you are granted additional
	17	// permissions described in the GCC Runtime Library Exception, version
	18	// 3.1, as published by the Free Software Foundation.
bd994a48	19
748086b7 JJ	20	// You should have received a copy of the GNU General Public License and
	21	// a copy of the GCC Runtime Library Exception along with this program;
	22	// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	23	// <http://www.gnu.org/licenses/>.
bd994a48 MM	24
	25	#include "tinfo.h"
	26
	27	namespace __cxxabiv1 {
	28
	29	__vmi_class_type_info::
	30	~__vmi_class_type_info ()
	31	{}
	32
	33	__class_type_info::__sub_kind __vmi_class_type_info::
	34	__do_find_public_src (ptrdiff_t src2dst,
	35	const void *obj_ptr,
	36	const __class_type_info *src_type,
	37	const void *src_ptr) const
	38	{
	39	if (obj_ptr == src_ptr && this == src_type)
	40	return __contained_public;
	41
	42	for (std::size_t i = __base_count; i--;)
	43	{
	44	if (!__base_info[i].__is_public_p ())
	45	continue; // Not public, can't be here.
	46
	47	const void *base = obj_ptr;
	48	ptrdiff_t offset = __base_info[i].__offset ();
	49	bool is_virtual = __base_info[i].__is_virtual_p ();
	50
	51	if (is_virtual)
	52	{
	53	if (src2dst == -3)
	54	continue; // Not a virtual base, so can't be here.
	55	}
	56	base = convert_to_base (base, is_virtual, offset);
	57
	58	__sub_kind base_kind = __base_info[i].__base_type->__do_find_public_src
	59	(src2dst, base, src_type, src_ptr);
	60	if (contained_p (base_kind))
	61	{
	62	if (is_virtual)
	63	base_kind = __sub_kind (base_kind \| __contained_virtual_mask);
	64	return base_kind;
	65	}
	66	}
	67
	68	return __not_contained;
	69	}
	70
	71	// This is a big hairy function. Although the run-time behaviour of
	72	// dynamic_cast is simple to describe, it gives rise to some non-obvious
	73	// behaviour. We also desire to determine as early as possible any definite
	74	// answer we can get. Because it is unknown what the run-time ratio of
	75	// succeeding to failing dynamic casts is, we do not know in which direction
	76	// to bias any optimizations. To that end we make no particular effort towards
	77	// early fail answers or early success answers. Instead we try to minimize
	78	// work by filling in things lazily (when we know we need the information),
	79	// and opportunisticly take early success or failure results.
	80	bool __vmi_class_type_info::
	81	__do_dyncast (ptrdiff_t src2dst,
	82	__sub_kind access_path,
	83	const __class_type_info *dst_type,
	84	const void *obj_ptr,
	85	const __class_type_info *src_type,
	86	const void *src_ptr,
	87	__dyncast_result &__restrict result) const
88	{
89	if (result.whole_details & __flags_unknown_mask)
90	result.whole_details = __flags;
91
92	if (obj_ptr == src_ptr && this == src_type)
93	{
94	// The src object we started from. Indicate how we are accessible from
95	// the most derived object.
96	result.whole2src = access_path;
97	return false;
98	}
99	if (this == dst_type)
100	{
101	result.dst_ptr = obj_ptr;
102	result.whole2dst = access_path;
103	if (src2dst >= 0)
104	result.dst2src = adjust_pointer <void> (obj_ptr, src2dst) == src_ptr
105	? __contained_public : __not_contained;
106	else if (src2dst == -2)
107	result.dst2src = __not_contained;
108	return false;
109	}
110
111	bool result_ambig = false;
112	for (std::size_t i = __base_count; i--;)
113	{
114	__dyncast_result result2 (result.whole_details);
115	void const *base = obj_ptr;
116	__sub_kind base_access = access_path;
117	ptrdiff_t offset = __base_info[i].__offset ();
118	bool is_virtual = __base_info[i].__is_virtual_p ();
119
120	if (is_virtual)
121	base_access = __sub_kind (base_access \| __contained_virtual_mask);
122	base = convert_to_base (base, is_virtual, offset);
123
124	if (!__base_info[i].__is_public_p ())
125	{
126	if (src2dst == -2 &&
127	!(result.whole_details
128	& (__non_diamond_repeat_mask \| __diamond_shaped_mask)))
129	// The hierarchy has no duplicate bases (which might ambiguate
130	// things) and where we started is not a public base of what we
131	// want (so it cannot be a downcast). There is nothing of interest
132	// hiding in a non-public base.
133	continue;
134	base_access = __sub_kind (base_access & ~__contained_public_mask);
135	}
136
137	bool result2_ambig
138	= __base_info[i].__base_type->__do_dyncast (src2dst, base_access,
139	dst_type, base,
140	src_type, src_ptr, result2);
141	result.whole2src = __sub_kind (result.whole2src \| result2.whole2src);
142	if (result2.dst2src == __contained_public
143	\|\| result2.dst2src == __contained_ambig)
144	{
145	result.dst_ptr = result2.dst_ptr;
146	result.whole2dst = result2.whole2dst;
147	result.dst2src = result2.dst2src;
148	// Found a downcast which can't be bettered or an ambiguous downcast
149	// which can't be disambiguated
150	return result2_ambig;
151	}
152
153	if (!result_ambig && !result.dst_ptr)
154	{
155	// Not found anything yet.
156	result.dst_ptr = result2.dst_ptr;
157	result.whole2dst = result2.whole2dst;
158	result_ambig = result2_ambig;
159	if (result.dst_ptr && result.whole2src != __unknown
160	&& !(__flags & __non_diamond_repeat_mask))
161	// Found dst and src and we don't have repeated bases.
162	return result_ambig;
163	}
164	else if (result.dst_ptr && result.dst_ptr == result2.dst_ptr)
165	{
166	// Found at same address, must be via virtual. Pick the most
167	// accessible path.
168	result.whole2dst =
169	__sub_kind (result.whole2dst \| result2.whole2dst);
170	}
171	else if ((result.dst_ptr != 0 && result2.dst_ptr != 0)
172	\|\| (result.dst_ptr != 0 && result2_ambig)
173	\|\| (result2.dst_ptr != 0 && result_ambig))
174	{
175	// Found two different DST_TYPE bases, or a valid one and a set of
176	// ambiguous ones, must disambiguate. See whether SRC_PTR is
177	// contained publicly within one of the non-ambiguous choices. If it
178	// is in only one, then that's the choice. If it is in both, then
179	// we're ambiguous and fail. If it is in neither, we're ambiguous,
180	// but don't yet fail as we might later find a third base which does
181	// contain SRC_PTR.
182
183	__sub_kind new_sub_kind = result2.dst2src;
184	__sub_kind old_sub_kind = result.dst2src;
185
186	if (contained_p (result.whole2src)
187	&& (!virtual_p (result.whole2src)
188	\|\| !(result.whole_details & __diamond_shaped_mask)))
189	{
190	// We already found SRC_PTR as a base of most derived, and
191	// either it was non-virtual, or the whole hierarchy is
192	// not-diamond shaped. Therefore if it is in either choice, it
193	// can only be in one of them, and we will already know.
194	if (old_sub_kind == __unknown)
195	old_sub_kind = __not_contained;
196	if (new_sub_kind == __unknown)
197	new_sub_kind = __not_contained;
198	}
199	else
200	{
201	if (old_sub_kind >= __not_contained)
202	;// already calculated
203	else if (contained_p (new_sub_kind)
204	&& (!virtual_p (new_sub_kind)
205	\|\| !(__flags & __diamond_shaped_mask)))
206	// Already found inside the other choice, and it was
207	// non-virtual or we are not diamond shaped.
208	old_sub_kind = __not_contained;
209	else
210	old_sub_kind = dst_type->__find_public_src
211	(src2dst, result.dst_ptr, src_type, src_ptr);
212
213	if (new_sub_kind >= __not_contained)
214	;// already calculated
215	else if (contained_p (old_sub_kind)
216	&& (!virtual_p (old_sub_kind)
217	\|\| !(__flags & __diamond_shaped_mask)))
218	// Already found inside the other choice, and it was
219	// non-virtual or we are not diamond shaped.
220	new_sub_kind = __not_contained;
221	else
222	new_sub_kind = dst_type->__find_public_src
223	(src2dst, result2.dst_ptr, src_type, src_ptr);
224	}
225
226	// Neither sub_kind can be contained_ambig -- we bail out early
227	// when we find those.
228	if (contained_p (__sub_kind (new_sub_kind ^ old_sub_kind)))
229	{
230	// Only on one choice, not ambiguous.
231	if (contained_p (new_sub_kind))
232	{
233	// Only in new.
234	result.dst_ptr = result2.dst_ptr;
235	result.whole2dst = result2.whole2dst;
236	result_ambig = false;
237	old_sub_kind = new_sub_kind;
238	}
239	result.dst2src = old_sub_kind;
240	if (public_p (result.dst2src))
241	return false; // Can't be an ambiguating downcast for later discovery.
242	if (!virtual_p (result.dst2src))
243	return false; // Found non-virtually can't be bettered
244	}
245	else if (contained_p (__sub_kind (new_sub_kind & old_sub_kind)))
246	{
247	// In both.
248	result.dst_ptr = NULL;
249	result.dst2src = __contained_ambig;
250	return true; // Fail.
251	}
252	else
253	{
254	// In neither publicly, ambiguous for the moment, but keep
255	// looking. It is possible that it was private in one or
256	// both and therefore we should fail, but that's just tough.
257	result.dst_ptr = NULL;
258	result.dst2src = __not_contained;
259	result_ambig = true;
260	}
261	}
262
263	if (result.whole2src == __contained_private)
264	// We found SRC_PTR as a private non-virtual base, therefore all
265	// cross casts will fail. We have already found a down cast, if
266	// there is one.
267	return result_ambig;
268	}
269
270	return result_ambig;
271	}
272
273	bool __vmi_class_type_info::
274	__do_upcast (const __class_type_info dst, const void obj_ptr,
275	__upcast_result &__restrict result) const
276	{
277	if (__class_type_info::__do_upcast (dst, obj_ptr, result))
278	return true;
279
280	int src_details = result.src_details;
281	if (src_details & __flags_unknown_mask)
282	src_details = __flags;
283
284	for (std::size_t i = __base_count; i--;)
285	{
286	__upcast_result result2 (src_details);
287	const void *base = obj_ptr;
288	ptrdiff_t offset = __base_info[i].__offset ();
289	bool is_virtual = __base_info[i].__is_virtual_p ();
290	bool is_public = __base_info[i].__is_public_p ();
291
292	if (!is_public && !(src_details & __non_diamond_repeat_mask))
293	// original cannot have an ambiguous base, so skip private bases
294	continue;
295
296	if (base)
297	base = convert_to_base (base, is_virtual, offset);
298
299	if (__base_info[i].__base_type->__do_upcast (dst, base, result2))
300	{
301	if (result2.base_type == nonvirtual_base_type && is_virtual)
302	result2.base_type = __base_info[i].__base_type;
303	if (contained_p (result2.part2dst) && !is_public)
304	result2.part2dst = __sub_kind (result2.part2dst & ~__contained_public_mask);
305
306	if (!result.base_type)
307	{
308	result = result2;
309	if (!contained_p (result.part2dst))
310	return true; // found ambiguously
311
312	if (result.part2dst & __contained_public_mask)
313	{
314	if (!(__flags & __non_diamond_repeat_mask))
315	return true; // cannot have an ambiguous other base
316	}
317	else
318	{
319	if (!virtual_p (result.part2dst))
320	return true; // cannot have another path
321	if (!(__flags & __diamond_shaped_mask))
322	return true; // cannot have a more accessible path
323	}
324	}
325	else if (result.dst_ptr != result2.dst_ptr)
326	{
327	// Found an ambiguity.
328	result.dst_ptr = NULL;
329	result.part2dst = __contained_ambig;
330	return true;
331	}
332	else if (result.dst_ptr)
333	{
334	// Ok, found real object via a virtual path.
335	result.part2dst
336	= __sub_kind (result.part2dst \| result2.part2dst);
337	}
338	else
339	{
340	// Dealing with a null pointer, need to check vbase
341	// containing each of the two choices.
342	if (result2.base_type == nonvirtual_base_type
343	\|\| result.base_type == nonvirtual_base_type
344	\|\| !(result2.base_type == result.base_type))
345	{
346	// Already ambiguous, not virtual or via different virtuals.
347	// Cannot match.
348	result.part2dst = __contained_ambig;
349	return true;
350	}
351	result.part2dst
352	= __sub_kind (result.part2dst \| result2.part2dst);
353	}
354	}
355	}
356	return result.part2dst != __unknown;
357	}
358
359	}