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1 | // Copyright (C) 1994-2024 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 | ||
26 | namespace __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. | |
79 | bool __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 | ||
304 | bool __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 | } |