1// Copyright (C) 1994-2017 Free Software Foundation, Inc.
2//
3// This file is part of GCC.
4//
5// GCC is free software; you can redistribute it and/or modify
6// it under the terms of the GNU General Public License as published by
7// the Free Software Foundation; either version 3, or (at your option)
8// any later version.
9
10// GCC is distributed in the hope that it will be useful,
11// but WITHOUT ANY WARRANTY; without even the implied warranty of
12// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13// GNU General Public License for more details.
14
15// Under Section 7 of GPL version 3, you are granted additional
16// permissions described in the GCC Runtime Library Exception, version
17// 3.1, as published by the Free Software Foundation.
18
19// You should have received a copy of the GNU General Public License and
20// a copy of the GCC Runtime Library Exception along with this program;
21// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
22// <http://www.gnu.org/licenses/>.
23
24#include "tinfo.h"
25
26namespace __cxxabiv1 {
27
28__vmi_class_type_info::
29~__vmi_class_type_info ()
30{}
31
32__class_type_info::__sub_kind __vmi_class_type_info::
33__do_find_public_src (ptrdiff_t src2dst,
34 const void *obj_ptr,
35 const __class_type_info *src_type,
36 const void *src_ptr) const
37{
38 if (obj_ptr == src_ptr && *this == *src_type)
39 return __contained_public;
40
41 for (std::size_t i = __base_count; i--;)
42 {
43 if (!__base_info[i].__is_public_p ())
44 continue; // Not public, can't be here.
45
46 const void *base = obj_ptr;
47 ptrdiff_t offset = __base_info[i].__offset ();
48 bool is_virtual = __base_info[i].__is_virtual_p ();
49
50 if (is_virtual)
51 {
52 if (src2dst == -3)
53 continue; // Not a virtual base, so can't be here.
54 }
55 base = convert_to_base (base, is_virtual, offset);
56
57 __sub_kind base_kind = __base_info[i].__base_type->__do_find_public_src
58 (src2dst, base, src_type, src_ptr);
59 if (contained_p (base_kind))
60 {
61 if (is_virtual)
62 base_kind = __sub_kind (base_kind | __contained_virtual_mask);
63 return base_kind;
64 }
65 }
66
67 return __not_contained;
68}
69
70// This is a big hairy function. Although the run-time behaviour of
71// dynamic_cast is simple to describe, it gives rise to some non-obvious
72// behaviour. We also desire to determine as early as possible any definite
73// answer we can get. Because it is unknown what the run-time ratio of
74// succeeding to failing dynamic casts is, we do not know in which direction
75// to bias any optimizations. To that end we make no particular effort towards
76// early fail answers or early success answers. Instead we try to minimize
77// work by filling in things lazily (when we know we need the information),
78// and opportunisticly take early success or failure results.
79bool __vmi_class_type_info::
80__do_dyncast (ptrdiff_t src2dst,
81 __sub_kind access_path,
82 const __class_type_info *dst_type,
83 const void *obj_ptr,
84 const __class_type_info *src_type,
85 const void *src_ptr,
86 __dyncast_result &__restrict result) const
87{
88 if (result.whole_details & __flags_unknown_mask)
89 result.whole_details = __flags;
90
91 if (obj_ptr == src_ptr && *this == *src_type)
92 {
93 // The src object we started from. Indicate how we are accessible from
94 // the most derived object.
95 result.whole2src = access_path;
96 return false;
97 }
98 if (*this == *dst_type)
99 {
100 result.dst_ptr = obj_ptr;
101 result.whole2dst = access_path;
102 if (src2dst >= 0)
103 result.dst2src = adjust_pointer <void> (obj_ptr, src2dst) == src_ptr
104 ? __contained_public : __not_contained;
105 else if (src2dst == -2)
106 result.dst2src = __not_contained;
107 return false;
108 }
109
110 // If src_type is a unique non-virtual base of dst_type, we have a good
111 // guess at the address we want, so in the first pass try skipping any
112 // bases which don't contain that address.
113 const void *dst_cand = NULL;
114 if (src2dst >= 0)
115 dst_cand = adjust_pointer<void>(src_ptr, -src2dst);
116 bool first_pass = true;
117 bool skipped = false;
118
119 bool result_ambig = false;
120 again:
121 for (std::size_t i = __base_count; i--;)
122 {
123 __dyncast_result result2 (result.whole_details);
124 void const *base = obj_ptr;
125 __sub_kind base_access = access_path;
126 ptrdiff_t offset = __base_info[i].__offset ();
127 bool is_virtual = __base_info[i].__is_virtual_p ();
128
129 if (is_virtual)
130 base_access = __sub_kind (base_access | __contained_virtual_mask);
131 base = convert_to_base (base, is_virtual, offset);
132
133 if (dst_cand)
134 {
135 bool skip_on_first_pass = base > dst_cand;
136 if (skip_on_first_pass == first_pass)
137 {
138 // We aren't interested in this base on this pass: either
139 // we're on the first pass and this base doesn't contain the
140 // likely address, or we're on the second pass and we checked
141 // this base on the first pass.
142 skipped = true;
143 continue;
144 }
145 }
146
147 if (!__base_info[i].__is_public_p ())
148 {
149 if (src2dst == -2 &&
150 !(result.whole_details
151 & (__non_diamond_repeat_mask | __diamond_shaped_mask)))
152 // The hierarchy has no duplicate bases (which might ambiguate
153 // things) and where we started is not a public base of what we
154 // want (so it cannot be a downcast). There is nothing of interest
155 // hiding in a non-public base.
156 continue;
157 base_access = __sub_kind (base_access & ~__contained_public_mask);
158 }
159
160 bool result2_ambig
161 = __base_info[i].__base_type->__do_dyncast (src2dst, base_access,
162 dst_type, base,
163 src_type, src_ptr, result2);
164 result.whole2src = __sub_kind (result.whole2src | result2.whole2src);
165 if (result2.dst2src == __contained_public
166 || result2.dst2src == __contained_ambig)
167 {
168 result.dst_ptr = result2.dst_ptr;
169 result.whole2dst = result2.whole2dst;
170 result.dst2src = result2.dst2src;
171 // Found a downcast which can't be bettered or an ambiguous downcast
172 // which can't be disambiguated
173 return result2_ambig;
174 }
175
176 if (!result_ambig && !result.dst_ptr)
177 {
178 // Not found anything yet.
179 result.dst_ptr = result2.dst_ptr;
180 result.whole2dst = result2.whole2dst;
181 result_ambig = result2_ambig;
182 if (result.dst_ptr && result.whole2src != __unknown
183 && !(__flags & __non_diamond_repeat_mask))
184 // Found dst and src and we don't have repeated bases.
185 return result_ambig;
186 }
187 else if (result.dst_ptr && result.dst_ptr == result2.dst_ptr)
188 {
189 // Found at same address, must be via virtual. Pick the most
190 // accessible path.
191 result.whole2dst =
192 __sub_kind (result.whole2dst | result2.whole2dst);
193 }
194 else if ((result.dst_ptr != 0 && result2.dst_ptr != 0)
195 || (result.dst_ptr != 0 && result2_ambig)
196 || (result2.dst_ptr != 0 && result_ambig))
197 {
198 // Found two different DST_TYPE bases, or a valid one and a set of
199 // ambiguous ones, must disambiguate. See whether SRC_PTR is
200 // contained publicly within one of the non-ambiguous choices. If it
201 // is in only one, then that's the choice. If it is in both, then
202 // we're ambiguous and fail. If it is in neither, we're ambiguous,
203 // but don't yet fail as we might later find a third base which does
204 // contain SRC_PTR.
205
206 __sub_kind new_sub_kind = result2.dst2src;
207 __sub_kind old_sub_kind = result.dst2src;
208
209 if (contained_p (result.whole2src)
210 && (!virtual_p (result.whole2src)
211 || !(result.whole_details & __diamond_shaped_mask)))
212 {
213 // We already found SRC_PTR as a base of most derived, and
214 // either it was non-virtual, or the whole hierarchy is
215 // not-diamond shaped. Therefore if it is in either choice, it
216 // can only be in one of them, and we will already know.
217 if (old_sub_kind == __unknown)
218 old_sub_kind = __not_contained;
219 if (new_sub_kind == __unknown)
220 new_sub_kind = __not_contained;
221 }
222 else
223 {
224 if (old_sub_kind >= __not_contained)
225 ;// already calculated
226 else if (contained_p (new_sub_kind)
227 && (!virtual_p (new_sub_kind)
228 || !(__flags & __diamond_shaped_mask)))
229 // Already found inside the other choice, and it was
230 // non-virtual or we are not diamond shaped.
231 old_sub_kind = __not_contained;
232 else
233 old_sub_kind = dst_type->__find_public_src
234 (src2dst, result.dst_ptr, src_type, src_ptr);
235
236 if (new_sub_kind >= __not_contained)
237 ;// already calculated
238 else if (contained_p (old_sub_kind)
239 && (!virtual_p (old_sub_kind)
240 || !(__flags & __diamond_shaped_mask)))
241 // Already found inside the other choice, and it was
242 // non-virtual or we are not diamond shaped.
243 new_sub_kind = __not_contained;
244 else
245 new_sub_kind = dst_type->__find_public_src
246 (src2dst, result2.dst_ptr, src_type, src_ptr);
247 }
248
249 // Neither sub_kind can be contained_ambig -- we bail out early
250 // when we find those.
251 if (contained_p (__sub_kind (new_sub_kind ^ old_sub_kind)))
252 {
253 // Only on one choice, not ambiguous.
254 if (contained_p (new_sub_kind))
255 {
256 // Only in new.
257 result.dst_ptr = result2.dst_ptr;
258 result.whole2dst = result2.whole2dst;
259 result_ambig = false;
260 old_sub_kind = new_sub_kind;
261 }
262 result.dst2src = old_sub_kind;
263 if (public_p (result.dst2src))
264 return false; // Can't be an ambiguating downcast for later discovery.
265 if (!virtual_p (result.dst2src))
266 return false; // Found non-virtually can't be bettered
267 }
268 else if (contained_p (__sub_kind (new_sub_kind & old_sub_kind)))
269 {
270 // In both.
271 result.dst_ptr = NULL;
272 result.dst2src = __contained_ambig;
273 return true; // Fail.
274 }
275 else
276 {
277 // In neither publicly, ambiguous for the moment, but keep
278 // looking. It is possible that it was private in one or
279 // both and therefore we should fail, but that's just tough.
280 result.dst_ptr = NULL;
281 result.dst2src = __not_contained;
282 result_ambig = true;
283 }
284 }
285
286 if (result.whole2src == __contained_private)
287 // We found SRC_PTR as a private non-virtual base, therefore all
288 // cross casts will fail. We have already found a down cast, if
289 // there is one.
290 return result_ambig;
291 }
292
293 if (skipped && first_pass)
294 {
295 // We didn't find dst where we expected it, so let's go back and try
296 // the bases we skipped (if any).
297 first_pass = false;
298 goto again;
299 }
300
301 return result_ambig;
302}
303
304bool __vmi_class_type_info::
305__do_upcast (const __class_type_info *dst, const void *obj_ptr,
306 __upcast_result &__restrict result) const
307{
308 if (__class_type_info::__do_upcast (dst, obj_ptr, result))
309 return true;
310
311 int src_details = result.src_details;
312 if (src_details & __flags_unknown_mask)
313 src_details = __flags;
314
315 for (std::size_t i = __base_count; i--;)
316 {
317 __upcast_result result2 (src_details);
318 const void *base = obj_ptr;
319 ptrdiff_t offset = __base_info[i].__offset ();
320 bool is_virtual = __base_info[i].__is_virtual_p ();
321 bool is_public = __base_info[i].__is_public_p ();
322
323 if (!is_public && !(src_details & __non_diamond_repeat_mask))
324 // original cannot have an ambiguous base, so skip private bases
325 continue;
326
327 if (base)
328 base = convert_to_base (base, is_virtual, offset);
329
330 if (__base_info[i].__base_type->__do_upcast (dst, base, result2))
331 {
332 if (result2.base_type == nonvirtual_base_type && is_virtual)
333 result2.base_type = __base_info[i].__base_type;
334 if (contained_p (result2.part2dst) && !is_public)
335 result2.part2dst = __sub_kind (result2.part2dst & ~__contained_public_mask);
336
337 if (!result.base_type)
338 {
339 result = result2;
340 if (!contained_p (result.part2dst))
341 return true; // found ambiguously
342
343 if (result.part2dst & __contained_public_mask)
344 {
345 if (!(__flags & __non_diamond_repeat_mask))
346 return true; // cannot have an ambiguous other base
347 }
348 else
349 {
350 if (!virtual_p (result.part2dst))
351 return true; // cannot have another path
352 if (!(__flags & __diamond_shaped_mask))
353 return true; // cannot have a more accessible path
354 }
355 }
356 else if (result.dst_ptr != result2.dst_ptr)
357 {
358 // Found an ambiguity.
359 result.dst_ptr = NULL;
360 result.part2dst = __contained_ambig;
361 return true;
362 }
363 else if (result.dst_ptr)
364 {
365 // Ok, found real object via a virtual path.
366 result.part2dst
367 = __sub_kind (result.part2dst | result2.part2dst);
368 }
369 else
370 {
371 // Dealing with a null pointer, need to check vbase
372 // containing each of the two choices.
373 if (result2.base_type == nonvirtual_base_type
374 || result.base_type == nonvirtual_base_type
375 || !(*result2.base_type == *result.base_type))
376 {
377 // Already ambiguous, not virtual or via different virtuals.
378 // Cannot match.
379 result.part2dst = __contained_ambig;
380 return true;
381 }
382 result.part2dst
383 = __sub_kind (result.part2dst | result2.part2dst);
384 }
385 }
386 }
387 return result.part2dst != __unknown;
388}
389
390}
391