1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "private_typeinfo.h"
10
11// The flag _LIBCXXABI_FORGIVING_DYNAMIC_CAST is used to make dynamic_cast
12// more forgiving when type_info's mistakenly have hidden visibility and
13// thus multiple type_infos can exist for a single type.
14//
15// When _LIBCXXABI_FORGIVING_DYNAMIC_CAST is defined, and only in the case where
16// there is a detected inconsistency in the type_info hierarchy during a
17// dynamic_cast, then the equality operation will fall back to using strcmp
18// on type_info names to determine type_info equality.
19//
20// This change happens *only* under dynamic_cast, and only when
21// dynamic_cast is faced with the choice: abort, or possibly give back the
22// wrong answer. If when the dynamic_cast is done with this fallback
23// algorithm and an inconsistency is still detected, dynamic_cast will call
24// abort with an appropriate message.
25//
26// The current implementation of _LIBCXXABI_FORGIVING_DYNAMIC_CAST requires a
27// printf-like function called syslog:
28//
29// void syslog(int facility_priority, const char* format, ...);
30//
31// If you want this functionality but your platform doesn't have syslog,
32// just implement it in terms of fprintf(stderr, ...).
33//
34// _LIBCXXABI_FORGIVING_DYNAMIC_CAST is currently off by default.
35
36// On Windows, typeids are different between DLLs and EXEs, so comparing
37// type_info* will work for typeids from the same compiled file but fail
38// for typeids from a DLL and an executable. Among other things, exceptions
39// are not caught by handlers since can_catch() returns false.
40//
41// Defining _LIBCXXABI_FORGIVING_DYNAMIC_CAST does not help since can_catch() calls
42// is_equal() with use_strcmp=false so the string names are not compared.
43
44#include <cstdint>
45#include <cassert>
46#include <string.h>
47#include "abort_message.h"
48
49#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
50#include <sys/syslog.h>
51#include <atomic>
52#endif
53
54#if __has_feature(ptrauth_calls)
55#include <ptrauth.h>
56#endif
57
58
59template<typename T>
60static inline
61T *
62get_vtable(T *vtable) {
63#if __has_feature(ptrauth_calls)
64 vtable = ptrauth_strip(vtable, ptrauth_key_cxx_vtable_pointer);
65#endif
66 return vtable;
67}
68
69static inline
70bool
71is_equal(const std::type_info* x, const std::type_info* y, bool use_strcmp)
72{
73 // Use std::type_info's default comparison unless we've explicitly asked
74 // for strcmp.
75 if (!use_strcmp)
76 return *x == *y;
77 // Still allow pointer equality to short circut.
78 return x == y || strcmp(x->name(), y->name()) == 0;
79}
80
81static inline ptrdiff_t update_offset_to_base(const char* vtable,
82 ptrdiff_t offset_to_base) {
83#if __has_feature(cxx_abi_relative_vtable)
84 // VTable components are 32 bits in the relative vtables ABI.
85 return *reinterpret_cast<const int32_t*>(vtable + offset_to_base);
86#else
87 return *reinterpret_cast<const ptrdiff_t*>(vtable + offset_to_base);
88#endif
89}
90
91namespace __cxxabiv1
92{
93
94namespace {
95
96struct derived_object_info {
97 const void* dynamic_ptr;
98 const __class_type_info* dynamic_type;
99 std::ptrdiff_t offset_to_derived;
100};
101
102/// A helper function that gets (dynamic_ptr, dynamic_type, offset_to_derived) from static_ptr.
103void dyn_cast_get_derived_info(derived_object_info* info, const void* static_ptr)
104{
105#if __has_feature(cxx_abi_relative_vtable)
106 // The vtable address will point to the first virtual function, which is 8
107 // bytes after the start of the vtable (4 for the offset from top + 4 for
108 // the typeinfo component).
109 const int32_t* vtable =
110 *reinterpret_cast<const int32_t* const*>(static_ptr);
111 info->offset_to_derived = static_cast<std::ptrdiff_t>(vtable[-2]);
112 info->dynamic_ptr = static_cast<const char*>(static_ptr) + info->offset_to_derived;
113
114 // The typeinfo component is now a relative offset to a proxy.
115 int32_t offset_to_ti_proxy = vtable[-1];
116 const uint8_t* ptr_to_ti_proxy =
117 reinterpret_cast<const uint8_t*>(vtable) + offset_to_ti_proxy;
118 info->dynamic_type = *(reinterpret_cast<const __class_type_info* const*>(ptr_to_ti_proxy));
119#else
120 void **vtable = *static_cast<void ** const *>(static_ptr);
121 vtable = get_vtable(vtable);
122 info->offset_to_derived = reinterpret_cast<ptrdiff_t>(vtable[-2]);
123 info->dynamic_ptr = static_cast<const char*>(static_ptr) + info->offset_to_derived;
124 info->dynamic_type = static_cast<const __class_type_info*>(vtable[-1]);
125#endif
126}
127
128/// A helper function for __dynamic_cast that casts a base sub-object pointer
129/// to the object's dynamic type.
130///
131/// This function returns the casting result directly. No further processing
132/// required.
133///
134/// Specifically, this function can only be called if the following pre-
135/// condition holds:
136/// * The dynamic type of the object pointed to by `static_ptr` is exactly
137/// the same as `dst_type`.
138const void* dyn_cast_to_derived(const void* static_ptr,
139 const void* dynamic_ptr,
140 const __class_type_info* static_type,
141 const __class_type_info* dst_type,
142 std::ptrdiff_t offset_to_derived,
143 std::ptrdiff_t src2dst_offset)
144{
145 // We're downcasting from src_type to the complete object's dynamic type.
146 // This is a really hot path that can be further optimized with the
147 // `src2dst_offset` hint.
148 // In such a case, dynamic_ptr already gives the casting result if the
149 // casting ever succeeds. All we have to do now is to check static_ptr
150 // points to a public base sub-object of dynamic_ptr.
151
152 if (src2dst_offset >= 0)
153 {
154 // The static type is a unique public non-virtual base type of
155 // dst_type at offset `src2dst_offset` from the origin of dst.
156 // Note that there might be other non-public static_type bases. The
157 // hint only guarantees that the public base is non-virtual and
158 // unique. So we have to check whether static_ptr points to that
159 // unique public base sub-object.
160 if (offset_to_derived != -src2dst_offset)
161 return nullptr;
162 return dynamic_ptr;
163 }
164
165 if (src2dst_offset == -2)
166 {
167 // static_type is not a public base of dst_type.
168 return nullptr;
169 }
170
171 // If src2dst_offset == -3, then:
172 // src_type is a multiple public base type but never a virtual
173 // base type. We can't conclude that static_ptr points to those
174 // public base sub-objects because there might be other non-
175 // public static_type bases. The search is inevitable.
176
177 // Fallback to the slow path to check that static_type is a public
178 // base type of dynamic_type.
179 // Using giant short cut. Add that information to info.
180 __dynamic_cast_info info = {dst_type, static_ptr, static_type, src2dst_offset, 0, 0, 0, 0, 0, 0, 0, 0,
181 1, // number_of_dst_type
182 false, false, false, true, nullptr};
183 // Do the search
184 dst_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, false);
185#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
186 // The following if should always be false because we should
187 // definitely find (static_ptr, static_type), either on a public
188 // or private path
189 if (info.path_dst_ptr_to_static_ptr == unknown)
190 {
191 // We get here only if there is some kind of visibility problem
192 // in client code.
193 static_assert(std::atomic<size_t>::is_always_lock_free, "");
194 static std::atomic<size_t> error_count(0);
195 size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
196 if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
197 syslog(LOG_ERR, "dynamic_cast error 1: Both of the following type_info's "
198 "should have public visibility. At least one of them is hidden. %s"
199 ", %s.\n", static_type->name(), dst_type->name());
200 // Redo the search comparing type_info's using strcmp
201 info = {dst_type, static_ptr, static_type, src2dst_offset, 0, 0, 0, 0, 0, 0,
202 0, 0, 0, false, false, false, true, nullptr};
203 info.number_of_dst_type = 1;
204 dst_type->search_above_dst(&info, dynamic_ptr, dynamic_ptr, public_path, true);
205 }
206#endif // _LIBCXXABI_FORGIVING_DYNAMIC_CAST
207 // Query the search.
208 if (info.path_dst_ptr_to_static_ptr != public_path)
209 return nullptr;
210
211 return dynamic_ptr;
212}
213
214/// A helper function for __dynamic_cast that tries to perform a downcast
215/// before giving up and falling back to the slow path.
216const void* dyn_cast_try_downcast(const void* static_ptr,
217 const void* dynamic_ptr,
218 const __class_type_info* dst_type,
219 const __class_type_info* dynamic_type,
220 std::ptrdiff_t src2dst_offset)
221{
222 if (src2dst_offset < 0)
223 {
224 // We can only optimize the case if the static type is a unique public
225 // base of dst_type. Give up.
226 return nullptr;
227 }
228
229 // Pretend there is a dst_type object that leads to static_ptr. Later we
230 // will check whether this imagined dst_type object exists. If it exists
231 // then it will be the casting result.
232 const void* dst_ptr_to_static = reinterpret_cast<const char*>(static_ptr) - src2dst_offset;
233
234 if (reinterpret_cast<std::intptr_t>(dst_ptr_to_static) < reinterpret_cast<std::intptr_t>(dynamic_ptr))
235 {
236 // The imagined dst_type object does not exist. Bail-out quickly.
237 return nullptr;
238 }
239
240 // Try to search a path from dynamic_type to dst_type.
241 __dynamic_cast_info dynamic_to_dst_info = {dynamic_type,
242 dst_ptr_to_static,
243 dst_type,
244 src2dst_offset,
245 0,
246 0,
247 0,
248 0,
249 0,
250 0,
251 0,
252 0,
253 1, // number_of_dst_type
254 false,
255 false,
256 false,
257 true,
258 nullptr};
259 dynamic_type->search_above_dst(&dynamic_to_dst_info, dynamic_ptr, dynamic_ptr, public_path, false);
260 if (dynamic_to_dst_info.path_dst_ptr_to_static_ptr != unknown) {
261 // We have found at least one path from dynamic_ptr to dst_ptr. The
262 // downcast can succeed.
263 return dst_ptr_to_static;
264 }
265
266 return nullptr;
267}
268
269const void* dyn_cast_slow(const void* static_ptr,
270 const void* dynamic_ptr,
271 const __class_type_info* static_type,
272 const __class_type_info* dst_type,
273 const __class_type_info* dynamic_type,
274 std::ptrdiff_t src2dst_offset)
275{
276 // Not using giant short cut. Do the search
277
278 // Initialize info struct for this search.
279 __dynamic_cast_info info = {dst_type, static_ptr, static_type, src2dst_offset, 0, 0, 0, 0, 0, 0,
280 0, 0, 0, false, false, false, true, nullptr};
281
282 dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, false);
283#ifdef _LIBCXXABI_FORGIVING_DYNAMIC_CAST
284 // The following if should always be false because we should
285 // definitely find (static_ptr, static_type), either on a public
286 // or private path
287 if (info.path_dst_ptr_to_static_ptr == unknown &&
288 info.path_dynamic_ptr_to_static_ptr == unknown)
289 {
290 static_assert(std::atomic<size_t>::is_always_lock_free, "");
291 static std::atomic<size_t> error_count(0);
292 size_t error_count_snapshot = error_count.fetch_add(1, std::memory_order_relaxed);
293 if ((error_count_snapshot & (error_count_snapshot-1)) == 0)
294 syslog(LOG_ERR, "dynamic_cast error 2: One or more of the following type_info's "
295 "has hidden visibility or is defined in more than one translation "
296 "unit. They should all have public visibility. "
297 "%s, %s, %s.\n", static_type->name(), dynamic_type->name(),
298 dst_type->name());
299 // Redo the search comparing type_info's using strcmp
300 info = {dst_type, static_ptr, static_type, src2dst_offset, 0, 0, 0, 0, 0, 0,
301 0, 0, 0, false, false, false, true, nullptr};
302 dynamic_type->search_below_dst(&info, dynamic_ptr, public_path, true);
303 }
304#endif // _LIBCXXABI_FORGIVING_DYNAMIC_CAST
305 // Query the search.
306 switch (info.number_to_static_ptr)
307 {
308 case 0:
309 if (info.number_to_dst_ptr == 1 &&
310 info.path_dynamic_ptr_to_static_ptr == public_path &&
311 info.path_dynamic_ptr_to_dst_ptr == public_path)
312 return info.dst_ptr_not_leading_to_static_ptr;
313 break;
314 case 1:
315 if (info.path_dst_ptr_to_static_ptr == public_path ||
316 (
317 info.number_to_dst_ptr == 0 &&
318 info.path_dynamic_ptr_to_static_ptr == public_path &&
319 info.path_dynamic_ptr_to_dst_ptr == public_path
320 )
321 )
322 return info.dst_ptr_leading_to_static_ptr;
323 break;
324 }
325
326 return nullptr;
327}
328
329} // namespace
330
331// __shim_type_info
332
333__shim_type_info::~__shim_type_info()
334{
335}
336
337void __shim_type_info::noop1() const {}
338void __shim_type_info::noop2() const {}
339
340// __fundamental_type_info
341
342// This miraculously (compiler magic) emits the type_info's for:
343// 1. all of the fundamental types
344// 2. pointers to all of the fundamental types
345// 3. pointers to all of the const fundamental types
346__fundamental_type_info::~__fundamental_type_info()
347{
348}
349
350// __array_type_info
351
352__array_type_info::~__array_type_info()
353{
354}
355
356// __function_type_info
357
358__function_type_info::~__function_type_info()
359{
360}
361
362// __enum_type_info
363
364__enum_type_info::~__enum_type_info()
365{
366}
367
368// __class_type_info
369
370__class_type_info::~__class_type_info()
371{
372}
373
374// __si_class_type_info
375
376__si_class_type_info::~__si_class_type_info()
377{
378}
379
380// __vmi_class_type_info
381
382__vmi_class_type_info::~__vmi_class_type_info()
383{
384}
385
386// __pbase_type_info
387
388__pbase_type_info::~__pbase_type_info()
389{
390}
391
392// __pointer_type_info
393
394__pointer_type_info::~__pointer_type_info()
395{
396}
397
398// __pointer_to_member_type_info
399
400__pointer_to_member_type_info::~__pointer_to_member_type_info()
401{
402}
403
404// can_catch
405
406// A handler is a match for an exception object of type E if
407// 1. The handler is of type cv T or cv T& and E and T are the same type
408// (ignoring the top-level cv-qualifiers), or
409// 2. the handler is of type cv T or cv T& and T is an unambiguous public
410// base class of E, or
411// 3. the handler is of type cv1 T* cv2 and E is a pointer type that can be
412// converted to the type of the handler by either or both of
413// A. a standard pointer conversion (4.10) not involving conversions to
414// pointers to private or protected or ambiguous classes
415// B. a qualification conversion
416// 4. the handler is a pointer or pointer to member type and E is
417// std::nullptr_t.
418
419// adjustedPtr:
420//
421// catch (A& a) : adjustedPtr == &a
422// catch (A* a) : adjustedPtr == a
423// catch (A** a) : adjustedPtr == a
424//
425// catch (D2& d2) : adjustedPtr == &d2 (d2 is base class of thrown object)
426// catch (D2* d2) : adjustedPtr == d2
427// catch (D2*& d2) : adjustedPtr == d2
428//
429// catch (...) : adjustedPtr == & of the exception
430//
431// If the thrown type is nullptr_t and the caught type is a pointer to
432// member type, adjustedPtr points to a statically-allocated null pointer
433// representation of that type.
434
435// Handles bullet 1
436bool
437__fundamental_type_info::can_catch(const __shim_type_info* thrown_type,
438 void*&) const
439{
440 return is_equal(x: this, y: thrown_type, use_strcmp: false);
441}
442
443bool
444__array_type_info::can_catch(const __shim_type_info*, void*&) const
445{
446 // We can get here if someone tries to catch an array by reference.
447 // However if someone tries to throw an array, it immediately gets
448 // converted to a pointer, which will not convert back to an array
449 // at the catch clause. So this can never catch anything.
450 return false;
451}
452
453bool
454__function_type_info::can_catch(const __shim_type_info*, void*&) const
455{
456 // We can get here if someone tries to catch a function by reference.
457 // However if someone tries to throw a function, it immediately gets
458 // converted to a pointer, which will not convert back to a function
459 // at the catch clause. So this can never catch anything.
460 return false;
461}
462
463// Handles bullet 1
464bool
465__enum_type_info::can_catch(const __shim_type_info* thrown_type,
466 void*&) const
467{
468 return is_equal(x: this, y: thrown_type, use_strcmp: false);
469}
470
471#ifdef __clang__
472#pragma clang diagnostic push
473#pragma clang diagnostic ignored "-Wmissing-field-initializers"
474#endif
475
476// Handles bullets 1 and 2
477bool
478__class_type_info::can_catch(const __shim_type_info* thrown_type,
479 void*& adjustedPtr) const
480{
481 // bullet 1
482 if (is_equal(x: this, y: thrown_type, use_strcmp: false))
483 return true;
484 const __class_type_info* thrown_class_type =
485 dynamic_cast<const __class_type_info*>(thrown_type);
486 if (thrown_class_type == 0)
487 return false;
488 // bullet 2
489 _LIBCXXABI_ASSERT(adjustedPtr, "catching a class without an object?");
490 __dynamic_cast_info info = {thrown_class_type, 0, this, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, true, nullptr};
491 info.number_of_dst_type = 1;
492 thrown_class_type->has_unambiguous_public_base(&info, adjustedPtr, public_path);
493 if (info.path_dst_ptr_to_static_ptr == public_path)
494 {
495 adjustedPtr = const_cast<void*>(info.dst_ptr_leading_to_static_ptr);
496 return true;
497 }
498 return false;
499}
500
501#ifdef __clang__
502#pragma clang diagnostic pop
503#endif
504
505// When we have an object to inspect - we just pass the pointer to the sub-
506// object that matched the static_type we just checked. If that is different
507// from any previously recorded pointer to that object type, then we have
508// an ambiguous case.
509
510// When we have no object to inspect, we need to account for virtual bases
511// explicitly.
512// info->vbase_cookie is a pointer to the name of the innermost virtual base
513// type, or nullptr if there is no virtual base on the path so far.
514// adjustedPtr points to the subobject we just found.
515// If vbase_cookie != any previously recorded (including the case of nullptr
516// representing an already-found static sub-object) then we have an ambiguous
517// case. Assuming that the vbase_cookie values agree; if then we have a
518// different offset (adjustedPtr) from any previously recorded, this indicates
519// an ambiguous case within the virtual base.
520
521void
522__class_type_info::process_found_base_class(__dynamic_cast_info* info,
523 void* adjustedPtr,
524 int path_below) const
525{
526 if (info->number_to_static_ptr == 0) {
527 // First time we found this base
528 info->dst_ptr_leading_to_static_ptr = adjustedPtr;
529 info->path_dst_ptr_to_static_ptr = path_below;
530 // stash the virtual base cookie.
531 info->dst_ptr_not_leading_to_static_ptr = info->vbase_cookie;
532 info->number_to_static_ptr = 1;
533 } else if (info->dst_ptr_not_leading_to_static_ptr == info->vbase_cookie &&
534 info->dst_ptr_leading_to_static_ptr == adjustedPtr) {
535 // We've been here before. Update path to "most public"
536 if (info->path_dst_ptr_to_static_ptr == not_public_path)
537 info->path_dst_ptr_to_static_ptr = path_below;
538 } else {
539 // We've detected an ambiguous cast from (thrown_class_type, adjustedPtr)
540 // to a static_type.
541 info->number_to_static_ptr += 1;
542 info->path_dst_ptr_to_static_ptr = not_public_path;
543 info->search_done = true;
544 }
545}
546
547void
548__class_type_info::has_unambiguous_public_base(__dynamic_cast_info* info,
549 void* adjustedPtr,
550 int path_below) const
551{
552 if (is_equal(this, info->static_type, false))
553 process_found_base_class(info, adjustedPtr, path_below);
554}
555
556void
557__si_class_type_info::has_unambiguous_public_base(__dynamic_cast_info* info,
558 void* adjustedPtr,
559 int path_below) const
560{
561 if (is_equal(this, info->static_type, false))
562 process_found_base_class(info, adjustedPtr, path_below);
563 else
564 __base_type->has_unambiguous_public_base(info, adjustedPtr, path_below);
565}
566
567void
568__base_class_type_info::has_unambiguous_public_base(__dynamic_cast_info* info,
569 void* adjustedPtr,
570 int path_below) const
571{
572 bool is_virtual = __offset_flags & __virtual_mask;
573 ptrdiff_t offset_to_base = 0;
574 if (info->have_object) {
575 /* We have an object to inspect, we can look through its vtables to
576 find the layout. */
577 offset_to_base = __offset_flags >> __offset_shift;
578 if (is_virtual) {
579 const char* vtable = *static_cast<const char* const*>(adjustedPtr);
580 vtable = get_vtable(vtable);
581 offset_to_base = update_offset_to_base(vtable, offset_to_base);
582 }
583 } else if (!is_virtual) {
584 /* We have no object; however, for non-virtual bases, (since we do not
585 need to inspect any content) we can pretend to have an object based
586 at '0'. */
587 offset_to_base = __offset_flags >> __offset_shift;
588 } else {
589 /* No object to inspect, and the next base is virtual.
590 We cannot indirect through the vtable to find the actual object offset.
591 So, update vbase_cookie to the new innermost virtual base using the
592 pointer to the typeinfo name as a key. */
593 info->vbase_cookie = static_cast<const void*>(__base_type->name());
594 // .. and reset the pointer.
595 adjustedPtr = nullptr;
596 }
597 __base_type->has_unambiguous_public_base(
598 info,
599 static_cast<char*>(adjustedPtr) + offset_to_base,
600 (__offset_flags & __public_mask) ? path_below : not_public_path);
601}
602
603void
604__vmi_class_type_info::has_unambiguous_public_base(__dynamic_cast_info* info,
605 void* adjustedPtr,
606 int path_below) const
607{
608 if (is_equal(this, info->static_type, false))
609 process_found_base_class(info, adjustedPtr, path_below);
610 else
611 {
612 typedef const __base_class_type_info* Iter;
613 const Iter e = __base_info + __base_count;
614 Iter p = __base_info;
615 p->has_unambiguous_public_base(info, adjustedPtr, path_below);
616 if (++p < e)
617 {
618 do
619 {
620 p->has_unambiguous_public_base(info, adjustedPtr, path_below);
621 if (info->search_done)
622 break;
623 } while (++p < e);
624 }
625 }
626}
627
628// Handles bullet 1 for both pointers and member pointers
629bool
630__pbase_type_info::can_catch(const __shim_type_info* thrown_type,
631 void*&) const
632{
633 bool use_strcmp = this->__flags & (__incomplete_class_mask |
634 __incomplete_mask);
635 if (!use_strcmp) {
636 const __pbase_type_info* thrown_pbase = dynamic_cast<const __pbase_type_info*>(
637 thrown_type);
638 if (!thrown_pbase) return false;
639 use_strcmp = thrown_pbase->__flags & (__incomplete_class_mask |
640 __incomplete_mask);
641 }
642 return is_equal(x: this, y: thrown_type, use_strcmp);
643}
644
645#ifdef __clang__
646#pragma clang diagnostic push
647#pragma clang diagnostic ignored "-Wmissing-field-initializers"
648#endif
649
650// Handles bullets 1, 3 and 4
651// NOTE: It might not be safe to adjust the pointer if it is not not a pointer
652// type. Only adjust the pointer after we know it is safe to do so.
653bool
654__pointer_type_info::can_catch(const __shim_type_info* thrown_type,
655 void*& adjustedPtr) const
656{
657 // bullet 4
658 if (is_equal(thrown_type, &typeid(std::nullptr_t), false)) {
659 adjustedPtr = nullptr;
660 return true;
661 }
662
663 // bullet 1
664 if (__pbase_type_info::can_catch(thrown_type, adjustedPtr)) {
665 if (adjustedPtr != NULL)
666 adjustedPtr = *static_cast<void**>(adjustedPtr);
667 return true;
668 }
669 // bullet 3
670 const __pointer_type_info* thrown_pointer_type =
671 dynamic_cast<const __pointer_type_info*>(thrown_type);
672 if (thrown_pointer_type == 0)
673 return false;
674 // Do the dereference adjustment
675 if (adjustedPtr != NULL)
676 adjustedPtr = *static_cast<void**>(adjustedPtr);
677 // bullet 3B and 3C
678 if (thrown_pointer_type->__flags & ~__flags & __no_remove_flags_mask)
679 return false;
680 if (__flags & ~thrown_pointer_type->__flags & __no_add_flags_mask)
681 return false;
682 if (is_equal(x: __pointee, y: thrown_pointer_type->__pointee, use_strcmp: false))
683 return true;
684 // bullet 3A
685 if (is_equal(__pointee, &typeid(void), false)) {
686 // pointers to functions cannot be converted to void*.
687 // pointers to member functions are not handled here.
688 const __function_type_info* thrown_function =
689 dynamic_cast<const __function_type_info*>(thrown_pointer_type->__pointee);
690 return (thrown_function == nullptr);
691 }
692 // Handle pointer to pointer
693 const __pointer_type_info* nested_pointer_type =
694 dynamic_cast<const __pointer_type_info*>(__pointee);
695 if (nested_pointer_type) {
696 if (~__flags & __const_mask) return false;
697 return nested_pointer_type->can_catch_nested(thrown_pointer_type->__pointee);
698 }
699
700 // Handle pointer to pointer to member
701 const __pointer_to_member_type_info* member_ptr_type =
702 dynamic_cast<const __pointer_to_member_type_info*>(__pointee);
703 if (member_ptr_type) {
704 if (~__flags & __const_mask) return false;
705 return member_ptr_type->can_catch_nested(thrown_pointer_type->__pointee);
706 }
707
708 // Handle pointer to class type
709 const __class_type_info* catch_class_type =
710 dynamic_cast<const __class_type_info*>(__pointee);
711 if (catch_class_type == 0)
712 return false;
713 const __class_type_info* thrown_class_type =
714 dynamic_cast<const __class_type_info*>(thrown_pointer_type->__pointee);
715 if (thrown_class_type == 0)
716 return false;
717 bool have_object = adjustedPtr != nullptr;
718 __dynamic_cast_info info = {thrown_class_type, 0, catch_class_type, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
719 have_object, nullptr};
720 info.number_of_dst_type = 1;
721 thrown_class_type->has_unambiguous_public_base(&info, adjustedPtr, public_path);
722 if (info.path_dst_ptr_to_static_ptr == public_path)
723 {
724 // In the case of a thrown null pointer, we have no object but we might
725 // well have computed the offset to where a public sub-object would be.
726 // However, we do not want to return that offset to the user; we still
727 // want them to catch a null ptr.
728 if (have_object)
729 adjustedPtr = const_cast<void*>(info.dst_ptr_leading_to_static_ptr);
730 else
731 adjustedPtr = nullptr;
732 return true;
733 }
734 return false;
735}
736
737bool __pointer_type_info::can_catch_nested(
738 const __shim_type_info* thrown_type) const
739{
740 const __pointer_type_info* thrown_pointer_type =
741 dynamic_cast<const __pointer_type_info*>(thrown_type);
742 if (thrown_pointer_type == 0)
743 return false;
744 // bullet 3B
745 if (thrown_pointer_type->__flags & ~__flags)
746 return false;
747 if (is_equal(x: __pointee, y: thrown_pointer_type->__pointee, use_strcmp: false))
748 return true;
749 // If the pointed to types differ then the catch type must be const
750 // qualified.
751 if (~__flags & __const_mask)
752 return false;
753
754 // Handle pointer to pointer
755 const __pointer_type_info* nested_pointer_type =
756 dynamic_cast<const __pointer_type_info*>(__pointee);
757 if (nested_pointer_type) {
758 return nested_pointer_type->can_catch_nested(
759 thrown_pointer_type->__pointee);
760 }
761
762 // Handle pointer to pointer to member
763 const __pointer_to_member_type_info* member_ptr_type =
764 dynamic_cast<const __pointer_to_member_type_info*>(__pointee);
765 if (member_ptr_type) {
766 return member_ptr_type->can_catch_nested(thrown_pointer_type->__pointee);
767 }
768
769 return false;
770}
771
772bool __pointer_to_member_type_info::can_catch(
773 const __shim_type_info* thrown_type, void*& adjustedPtr) const {
774 // bullet 4
775 if (is_equal(thrown_type, &typeid(std::nullptr_t), false)) {
776 // We assume that the pointer to member representation is the same for
777 // all pointers to data members and for all pointers to member functions.
778 struct X {};
779 if (dynamic_cast<const __function_type_info*>(__pointee)) {
780 static int (X::*const null_ptr_rep)() = nullptr;
781 adjustedPtr = const_cast<int (X::**)()>(&null_ptr_rep);
782 } else {
783 static int X::*const null_ptr_rep = nullptr;
784 adjustedPtr = const_cast<int X::**>(&null_ptr_rep);
785 }
786 return true;
787 }
788
789 // bullet 1
790 if (__pbase_type_info::can_catch(thrown_type, adjustedPtr))
791 return true;
792
793 const __pointer_to_member_type_info* thrown_pointer_type =
794 dynamic_cast<const __pointer_to_member_type_info*>(thrown_type);
795 if (thrown_pointer_type == 0)
796 return false;
797 if (thrown_pointer_type->__flags & ~__flags & __no_remove_flags_mask)
798 return false;
799 if (__flags & ~thrown_pointer_type->__flags & __no_add_flags_mask)
800 return false;
801 if (!is_equal(x: __pointee, y: thrown_pointer_type->__pointee, use_strcmp: false))
802 return false;
803 if (is_equal(x: __context, y: thrown_pointer_type->__context, use_strcmp: false))
804 return true;
805
806 // [except.handle] does not allow the pointer-to-member conversions mentioned
807 // in [mem.conv] to take place. For this reason we don't check Derived->Base
808 // for Derived->Base conversions.
809
810 return false;
811}
812
813bool __pointer_to_member_type_info::can_catch_nested(
814 const __shim_type_info* thrown_type) const
815{
816 const __pointer_to_member_type_info* thrown_member_ptr_type =
817 dynamic_cast<const __pointer_to_member_type_info*>(thrown_type);
818 if (thrown_member_ptr_type == 0)
819 return false;
820 if (~__flags & thrown_member_ptr_type->__flags)
821 return false;
822 if (!is_equal(x: __pointee, y: thrown_member_ptr_type->__pointee, use_strcmp: false))
823 return false;
824 if (!is_equal(x: __context, y: thrown_member_ptr_type->__context, use_strcmp: false))
825 return false;
826 return true;
827}
828
829#ifdef __clang__
830#pragma clang diagnostic pop
831#endif
832
833#ifdef __clang__
834#pragma clang diagnostic push
835#pragma clang diagnostic ignored "-Wmissing-field-initializers"
836#endif
837
838// __dynamic_cast
839
840// static_ptr: pointer to an object of type static_type; nonnull, and since the
841// object is polymorphic, *(void**)static_ptr is a virtual table pointer.
842// static_ptr is &v in the expression dynamic_cast<T>(v).
843// static_type: static type of the object pointed to by static_ptr.
844// dst_type: destination type of the cast (the "T" in "dynamic_cast<T>(v)").
845// src2dst_offset: a static hint about the location of the
846// source subobject with respect to the complete object;
847// special negative values are:
848// -1: no hint
849// -2: static_type is not a public base of dst_type
850// -3: static_type is a multiple public base type but never a
851// virtual base type
852// otherwise, the static_type type is a unique public nonvirtual
853// base type of dst_type at offset src2dst_offset from the
854// origin of dst_type.
855//
856// (dynamic_ptr, dynamic_type) are the run time type of the complete object
857// referred to by static_ptr and a pointer to it. These can be found from
858// static_ptr for polymorphic types.
859// static_type is guaranteed to be a polymorphic type.
860//
861// (dynamic_ptr, dynamic_type) is the root of a DAG that grows upward. Each
862// node of the tree represents a base class/object of its parent (or parents) below.
863// Each node is uniquely represented by a pointer to the object, and a pointer
864// to a type_info - its type. Different nodes may have the same pointer and
865// different nodes may have the same type. But only one node has a specific
866// (pointer-value, type) pair. In C++ two objects of the same type can not
867// share the same address.
868//
869// There are two flavors of nodes which have the type dst_type:
870// 1. Those that are derived from (below) (static_ptr, static_type).
871// 2. Those that are not derived from (below) (static_ptr, static_type).
872//
873// Invariants of the DAG:
874//
875// There is at least one path from the root (dynamic_ptr, dynamic_type) to
876// the node (static_ptr, static_type). This path may or may not be public.
877// There may be more than one such path (some public some not). Such a path may
878// or may not go through a node having type dst_type.
879//
880// No node of type T appears above a node of the same type. That means that
881// there is only one node with dynamic_type. And if dynamic_type == dst_type,
882// then there is only one dst_type in the DAG.
883//
884// No node of type dst_type appears above a node of type static_type. Such
885// DAG's are possible in C++, but the compiler computes those dynamic_casts at
886// compile time, and only calls __dynamic_cast when dst_type lies below
887// static_type in the DAG.
888//
889// dst_type != static_type: The compiler computes the dynamic_cast in this case too.
890// dynamic_type != static_type: The compiler computes the dynamic_cast in this case too.
891//
892// Returns:
893//
894// If there is exactly one dst_type of flavor 1, and
895// If there is a public path from that dst_type to (static_ptr, static_type), or
896// If there are 0 dst_types of flavor 2, and there is a public path from
897// (dynamic_ptr, dynamic_type) to (static_ptr, static_type) and a public
898// path from (dynamic_ptr, dynamic_type) to the one dst_type, then return
899// a pointer to that dst_type.
900// Else if there are 0 dst_types of flavor 1 and exactly 1 dst_type of flavor 2, and
901// if there is a public path from (dynamic_ptr, dynamic_type) to
902// (static_ptr, static_type) and a public path from (dynamic_ptr, dynamic_type)
903// to the one dst_type, then return a pointer to that one dst_type.
904// Else return nullptr.
905//
906// If dynamic_type == dst_type, then the above algorithm collapses to the
907// following cheaper algorithm:
908//
909// If there is a public path from (dynamic_ptr, dynamic_type) to
910// (static_ptr, static_type), then return dynamic_ptr.
911// Else return nullptr.
912
913extern "C" _LIBCXXABI_FUNC_VIS void *
914__dynamic_cast(const void *static_ptr, const __class_type_info *static_type,
915 const __class_type_info *dst_type,
916 std::ptrdiff_t src2dst_offset) {
917 // Get (dynamic_ptr, dynamic_type) from static_ptr
918 derived_object_info derived_info;
919 dyn_cast_get_derived_info(info: &derived_info, static_ptr);
920
921 // Initialize answer to nullptr. This will be changed from the search
922 // results if a non-null answer is found. Regardless, this is what will
923 // be returned.
924 const void* dst_ptr = 0;
925
926 // Find out if we can use a giant short cut in the search
927 if (is_equal(x: derived_info.dynamic_type, y: dst_type, use_strcmp: false))
928 {
929 dst_ptr = dyn_cast_to_derived(static_ptr,
930 dynamic_ptr: derived_info.dynamic_ptr,
931 static_type,
932 dst_type,
933 offset_to_derived: derived_info.offset_to_derived,
934 src2dst_offset);
935 }
936 else
937 {
938 // Optimize toward downcasting: let's first try to do a downcast before
939 // falling back to the slow path.
940 dst_ptr = dyn_cast_try_downcast(static_ptr,
941 dynamic_ptr: derived_info.dynamic_ptr,
942 dst_type,
943 dynamic_type: derived_info.dynamic_type,
944 src2dst_offset);
945
946 if (!dst_ptr)
947 {
948 dst_ptr = dyn_cast_slow(static_ptr,
949 dynamic_ptr: derived_info.dynamic_ptr,
950 static_type,
951 dst_type,
952 dynamic_type: derived_info.dynamic_type,
953 src2dst_offset);
954 }
955 }
956
957 return const_cast<void*>(dst_ptr);
958}
959
960#ifdef __clang__
961#pragma clang diagnostic pop
962#endif
963
964// Call this function when you hit a static_type which is a base (above) a dst_type.
965// Let caller know you hit a static_type. But only start recording details if
966// this is (static_ptr, static_type) -- the node we are casting from.
967// If this is (static_ptr, static_type)
968// Record the path (public or not) from the dst_type to here. There may be
969// multiple paths from the same dst_type to here, record the "most public" one.
970// Record the dst_ptr as pointing to (static_ptr, static_type).
971// If more than one (dst_ptr, dst_type) points to (static_ptr, static_type),
972// then mark this dyanmic_cast as ambiguous and stop the search.
973void
974__class_type_info::process_static_type_above_dst(__dynamic_cast_info* info,
975 const void* dst_ptr,
976 const void* current_ptr,
977 int path_below) const
978{
979 // Record that we found a static_type
980 info->found_any_static_type = true;
981 if (current_ptr == info->static_ptr)
982 {
983 // Record that we found (static_ptr, static_type)
984 info->found_our_static_ptr = true;
985 if (info->dst_ptr_leading_to_static_ptr == 0)
986 {
987 // First time here
988 info->dst_ptr_leading_to_static_ptr = dst_ptr;
989 info->path_dst_ptr_to_static_ptr = path_below;
990 info->number_to_static_ptr = 1;
991 // If there is only one dst_type in the entire tree and the path from
992 // there to here is public then we are done!
993 if (info->number_of_dst_type == 1 && info->path_dst_ptr_to_static_ptr == public_path)
994 info->search_done = true;
995 }
996 else if (info->dst_ptr_leading_to_static_ptr == dst_ptr)
997 {
998 // We've been here before. Update path to "most public"
999 if (info->path_dst_ptr_to_static_ptr == not_public_path)
1000 info->path_dst_ptr_to_static_ptr = path_below;
1001 // If there is only one dst_type in the entire tree and the path from
1002 // there to here is public then we are done!
1003 if (info->number_of_dst_type == 1 && info->path_dst_ptr_to_static_ptr == public_path)
1004 info->search_done = true;
1005 }
1006 else
1007 {
1008 // We've detected an ambiguous cast from (static_ptr, static_type)
1009 // to a dst_type
1010 info->number_to_static_ptr += 1;
1011 info->search_done = true;
1012 }
1013 }
1014}
1015
1016// Call this function when you hit a static_type which is not a base (above) a dst_type.
1017// If this is (static_ptr, static_type)
1018// Record the path (public or not) from (dynamic_ptr, dynamic_type) to here. There may be
1019// multiple paths from (dynamic_ptr, dynamic_type) to here, record the "most public" one.
1020void
1021__class_type_info::process_static_type_below_dst(__dynamic_cast_info* info,
1022 const void* current_ptr,
1023 int path_below) const
1024{
1025 if (current_ptr == info->static_ptr)
1026 {
1027 // Record the most public path from (dynamic_ptr, dynamic_type) to
1028 // (static_ptr, static_type)
1029 if (info->path_dynamic_ptr_to_static_ptr != public_path)
1030 info->path_dynamic_ptr_to_static_ptr = path_below;
1031 }
1032}
1033
1034// Call this function when searching below a dst_type node. This function searches
1035// for a path to (static_ptr, static_type) and for paths to one or more dst_type nodes.
1036// If it finds a static_type node, there is no need to further search base classes
1037// above.
1038// If it finds a dst_type node it should search base classes using search_above_dst
1039// to find out if this dst_type points to (static_ptr, static_type) or not.
1040// Either way, the dst_type is recorded as one of two "flavors": one that does
1041// or does not point to (static_ptr, static_type).
1042// If this is neither a static_type nor a dst_type node, continue searching
1043// base classes above.
1044// All the hoopla surrounding the search code is doing nothing but looking for
1045// excuses to stop the search prematurely (break out of the for-loop). That is,
1046// the algorithm below is simply an optimization of this:
1047// void
1048// __vmi_class_type_info::search_below_dst(__dynamic_cast_info* info,
1049// const void* current_ptr,
1050// int path_below) const
1051// {
1052// typedef const __base_class_type_info* Iter;
1053// if (this == info->static_type)
1054// process_static_type_below_dst(info, current_ptr, path_below);
1055// else if (this == info->dst_type)
1056// {
1057// // Record the most public access path that got us here
1058// if (info->path_dynamic_ptr_to_dst_ptr != public_path)
1059// info->path_dynamic_ptr_to_dst_ptr = path_below;
1060// bool does_dst_type_point_to_our_static_type = false;
1061// for (Iter p = __base_info, e= __base_info + __base_count; p < e; ++p)
1062// {
1063// p->search_above_dst(info, current_ptr, current_ptr, public_path);
1064// if (info->found_our_static_ptr)
1065// does_dst_type_point_to_our_static_type = true;
1066// // break out early here if you can detect it doesn't matter if you do
1067// }
1068// if (!does_dst_type_point_to_our_static_type)
1069// {
1070// // We found a dst_type that doesn't point to (static_ptr, static_type)
1071// // So record the address of this dst_ptr and increment the
1072// // count of the number of such dst_types found in the tree.
1073// info->dst_ptr_not_leading_to_static_ptr = current_ptr;
1074// info->number_to_dst_ptr += 1;
1075// }
1076// }
1077// else
1078// {
1079// // This is not a static_type and not a dst_type.
1080// for (Iter p = __base_info, e = __base_info + __base_count; p < e; ++p)
1081// {
1082// p->search_below_dst(info, current_ptr, public_path);
1083// // break out early here if you can detect it doesn't matter if you do
1084// }
1085// }
1086// }
1087void
1088__vmi_class_type_info::search_below_dst(__dynamic_cast_info* info,
1089 const void* current_ptr,
1090 int path_below,
1091 bool use_strcmp) const
1092{
1093 typedef const __base_class_type_info* Iter;
1094 if (is_equal(this, info->static_type, use_strcmp))
1095 process_static_type_below_dst(info, current_ptr, path_below);
1096 else if (is_equal(this, info->dst_type, use_strcmp))
1097 {
1098 // We've been here before if we've recorded current_ptr in one of these
1099 // two places:
1100 if (current_ptr == info->dst_ptr_leading_to_static_ptr ||
1101 current_ptr == info->dst_ptr_not_leading_to_static_ptr)
1102 {
1103 // We've seen this node before, and therefore have already searched
1104 // its base classes above.
1105 // Update path to here that is "most public".
1106 if (path_below == public_path)
1107 info->path_dynamic_ptr_to_dst_ptr = public_path;
1108 }
1109 else // We have haven't been here before
1110 {
1111 // Record the access path that got us here
1112 // If there is more than one dst_type this path doesn't matter.
1113 info->path_dynamic_ptr_to_dst_ptr = path_below;
1114 bool does_dst_type_point_to_our_static_type = false;
1115 // Only search above here if dst_type derives from static_type, or
1116 // if it is unknown if dst_type derives from static_type.
1117 if (info->is_dst_type_derived_from_static_type != no)
1118 {
1119 // Set up flags to record results from all base classes
1120 bool is_dst_type_derived_from_static_type = false;
1121
1122 // We've found a dst_type with a potentially public path to here.
1123 // We have to assume the path is public because it may become
1124 // public later (if we get back to here with a public path).
1125 // We can stop looking above if:
1126 // 1. We've found a public path to (static_ptr, static_type).
1127 // 2. We've found an ambiguous cast from (static_ptr, static_type) to a dst_type.
1128 // This is detected at the (static_ptr, static_type).
1129 // 3. We can prove that there is no public path to (static_ptr, static_type)
1130 // above here.
1131 const Iter e = __base_info + __base_count;
1132 for (Iter p = __base_info; p < e; ++p)
1133 {
1134 // Zero out found flags
1135 info->found_our_static_ptr = false;
1136 info->found_any_static_type = false;
1137 p->search_above_dst(info, current_ptr, current_ptr, public_path, use_strcmp);
1138 if (info->search_done)
1139 break;
1140 if (info->found_any_static_type)
1141 {
1142 is_dst_type_derived_from_static_type = true;
1143 if (info->found_our_static_ptr)
1144 {
1145 does_dst_type_point_to_our_static_type = true;
1146 // If we found what we're looking for, stop looking above.
1147 if (info->path_dst_ptr_to_static_ptr == public_path)
1148 break;
1149 // We found a private path to (static_ptr, static_type)
1150 // If there is no diamond then there is only one path
1151 // to (static_ptr, static_type) and we just found it.
1152 if (!(__flags & __diamond_shaped_mask))
1153 break;
1154 }
1155 else
1156 {
1157 // If we found a static_type that isn't the one we're looking
1158 // for, and if there are no repeated types above here,
1159 // then stop looking.
1160 if (!(__flags & __non_diamond_repeat_mask))
1161 break;
1162 }
1163 }
1164 }
1165 // If we found no static_type,s then dst_type doesn't derive
1166 // from static_type, else it does. Record this result so that
1167 // next time we hit a dst_type we will know not to search above
1168 // it if it doesn't derive from static_type.
1169 if (is_dst_type_derived_from_static_type)
1170 info->is_dst_type_derived_from_static_type = yes;
1171 else
1172 info->is_dst_type_derived_from_static_type = no;
1173 }
1174 if (!does_dst_type_point_to_our_static_type)
1175 {
1176 // We found a dst_type that doesn't point to (static_ptr, static_type)
1177 // So record the address of this dst_ptr and increment the
1178 // count of the number of such dst_types found in the tree.
1179 info->dst_ptr_not_leading_to_static_ptr = current_ptr;
1180 info->number_to_dst_ptr += 1;
1181 // If there exists another dst with a private path to
1182 // (static_ptr, static_type), then the cast from
1183 // (dynamic_ptr, dynamic_type) to dst_type is now ambiguous,
1184 // so stop search.
1185 if (info->number_to_static_ptr == 1 &&
1186 info->path_dst_ptr_to_static_ptr == not_public_path)
1187 info->search_done = true;
1188 }
1189 }
1190 }
1191 else
1192 {
1193 // This is not a static_type and not a dst_type.
1194 const Iter e = __base_info + __base_count;
1195 Iter p = __base_info;
1196 p->search_below_dst(info, current_ptr, path_below, use_strcmp);
1197 if (++p < e)
1198 {
1199 if ((__flags & __diamond_shaped_mask) || info->number_to_static_ptr == 1)
1200 {
1201 // If there are multiple paths to a base above from here, or if
1202 // a dst_type pointing to (static_ptr, static_type) has been found,
1203 // then there is no way to break out of this loop early unless
1204 // something below detects the search is done.
1205 do
1206 {
1207 if (info->search_done)
1208 break;
1209 p->search_below_dst(info, current_ptr, path_below, use_strcmp);
1210 } while (++p < e);
1211 }
1212 else if (__flags & __non_diamond_repeat_mask)
1213 {
1214 // There are not multiple paths to any base class from here and a
1215 // dst_type pointing to (static_ptr, static_type) has not yet been
1216 // found.
1217 do
1218 {
1219 if (info->search_done)
1220 break;
1221 // If we just found a dst_type with a public path to (static_ptr, static_type),
1222 // then the only reason to continue the search is to make sure
1223 // no other dst_type points to (static_ptr, static_type).
1224 // If !diamond, then we don't need to search here.
1225 if (info->number_to_static_ptr == 1 &&
1226 info->path_dst_ptr_to_static_ptr == public_path)
1227 break;
1228 p->search_below_dst(info, current_ptr, path_below, use_strcmp);
1229 } while (++p < e);
1230 }
1231 else
1232 {
1233 // There are no repeated types above this node.
1234 // There are no nodes with multiple parents above this node.
1235 // no dst_type has been found to (static_ptr, static_type)
1236 do
1237 {
1238 if (info->search_done)
1239 break;
1240 // If we just found a dst_type with a public path to (static_ptr, static_type),
1241 // then the only reason to continue the search is to make sure
1242 // no other dst_type points to (static_ptr, static_type).
1243 // If !diamond, then we don't need to search here.
1244 // if we just found a dst_type with a private path to (static_ptr, static_type),
1245 // then we're only looking for a public path to (static_ptr, static_type)
1246 // and to check for other dst_types.
1247 // If !diamond & !repeat, then there is not a pointer to (static_ptr, static_type)
1248 // and not a dst_type under here.
1249 if (info->number_to_static_ptr == 1)
1250 break;
1251 p->search_below_dst(info, current_ptr, path_below, use_strcmp);
1252 } while (++p < e);
1253 }
1254 }
1255 }
1256}
1257
1258// This is the same algorithm as __vmi_class_type_info::search_below_dst but
1259// simplified to the case that there is only a single base class.
1260void
1261__si_class_type_info::search_below_dst(__dynamic_cast_info* info,
1262 const void* current_ptr,
1263 int path_below,
1264 bool use_strcmp) const
1265{
1266 if (is_equal(this, info->static_type, use_strcmp))
1267 process_static_type_below_dst(info, current_ptr, path_below);
1268 else if (is_equal(this, info->dst_type, use_strcmp))
1269 {
1270 // We've been here before if we've recorded current_ptr in one of these
1271 // two places:
1272 if (current_ptr == info->dst_ptr_leading_to_static_ptr ||
1273 current_ptr == info->dst_ptr_not_leading_to_static_ptr)
1274 {
1275 // We've seen this node before, and therefore have already searched
1276 // its base classes above.
1277 // Update path to here that is "most public".
1278 if (path_below == public_path)
1279 info->path_dynamic_ptr_to_dst_ptr = public_path;
1280 }
1281 else // We have haven't been here before
1282 {
1283 // Record the access path that got us here
1284 // If there is more than one dst_type this path doesn't matter.
1285 info->path_dynamic_ptr_to_dst_ptr = path_below;
1286 bool does_dst_type_point_to_our_static_type = false;
1287 // Only search above here if dst_type derives from static_type, or
1288 // if it is unknown if dst_type derives from static_type.
1289 if (info->is_dst_type_derived_from_static_type != no)
1290 {
1291 // Set up flags to record results from all base classes
1292 bool is_dst_type_derived_from_static_type = false;
1293 // Zero out found flags
1294 info->found_our_static_ptr = false;
1295 info->found_any_static_type = false;
1296 __base_type->search_above_dst(info, current_ptr, current_ptr, public_path, use_strcmp);
1297 if (info->found_any_static_type)
1298 {
1299 is_dst_type_derived_from_static_type = true;
1300 if (info->found_our_static_ptr)
1301 does_dst_type_point_to_our_static_type = true;
1302 }
1303 // If we found no static_type,s then dst_type doesn't derive
1304 // from static_type, else it does. Record this result so that
1305 // next time we hit a dst_type we will know not to search above
1306 // it if it doesn't derive from static_type.
1307 if (is_dst_type_derived_from_static_type)
1308 info->is_dst_type_derived_from_static_type = yes;
1309 else
1310 info->is_dst_type_derived_from_static_type = no;
1311 }
1312 if (!does_dst_type_point_to_our_static_type)
1313 {
1314 // We found a dst_type that doesn't point to (static_ptr, static_type)
1315 // So record the address of this dst_ptr and increment the
1316 // count of the number of such dst_types found in the tree.
1317 info->dst_ptr_not_leading_to_static_ptr = current_ptr;
1318 info->number_to_dst_ptr += 1;
1319 // If there exists another dst with a private path to
1320 // (static_ptr, static_type), then the cast from
1321 // (dynamic_ptr, dynamic_type) to dst_type is now ambiguous.
1322 if (info->number_to_static_ptr == 1 &&
1323 info->path_dst_ptr_to_static_ptr == not_public_path)
1324 info->search_done = true;
1325 }
1326 }
1327 }
1328 else
1329 {
1330 // This is not a static_type and not a dst_type
1331 __base_type->search_below_dst(info, current_ptr, path_below, use_strcmp);
1332 }
1333}
1334
1335// This is the same algorithm as __vmi_class_type_info::search_below_dst but
1336// simplified to the case that there is no base class.
1337void
1338__class_type_info::search_below_dst(__dynamic_cast_info* info,
1339 const void* current_ptr,
1340 int path_below,
1341 bool use_strcmp) const
1342{
1343 if (is_equal(this, info->static_type, use_strcmp))
1344 process_static_type_below_dst(info, current_ptr, path_below);
1345 else if (is_equal(this, info->dst_type, use_strcmp))
1346 {
1347 // We've been here before if we've recorded current_ptr in one of these
1348 // two places:
1349 if (current_ptr == info->dst_ptr_leading_to_static_ptr ||
1350 current_ptr == info->dst_ptr_not_leading_to_static_ptr)
1351 {
1352 // We've seen this node before, and therefore have already searched
1353 // its base classes above.
1354 // Update path to here that is "most public".
1355 if (path_below == public_path)
1356 info->path_dynamic_ptr_to_dst_ptr = public_path;
1357 }
1358 else // We have haven't been here before
1359 {
1360 // Record the access path that got us here
1361 // If there is more than one dst_type this path doesn't matter.
1362 info->path_dynamic_ptr_to_dst_ptr = path_below;
1363 // We found a dst_type that doesn't point to (static_ptr, static_type)
1364 // So record the address of this dst_ptr and increment the
1365 // count of the number of such dst_types found in the tree.
1366 info->dst_ptr_not_leading_to_static_ptr = current_ptr;
1367 info->number_to_dst_ptr += 1;
1368 // If there exists another dst with a private path to
1369 // (static_ptr, static_type), then the cast from
1370 // (dynamic_ptr, dynamic_type) to dst_type is now ambiguous.
1371 if (info->number_to_static_ptr == 1 &&
1372 info->path_dst_ptr_to_static_ptr == not_public_path)
1373 info->search_done = true;
1374 // We found that dst_type does not derive from static_type
1375 info->is_dst_type_derived_from_static_type = no;
1376 }
1377 }
1378}
1379
1380// Call this function when searching above a dst_type node. This function searches
1381// for a public path to (static_ptr, static_type).
1382// This function is guaranteed not to find a node of type dst_type.
1383// Theoretically this is a very simple function which just stops if it finds a
1384// static_type node: All the hoopla surrounding the search code is doing
1385// nothing but looking for excuses to stop the search prematurely (break out of
1386// the for-loop). That is, the algorithm below is simply an optimization of this:
1387// void
1388// __vmi_class_type_info::search_above_dst(__dynamic_cast_info* info,
1389// const void* dst_ptr,
1390// const void* current_ptr,
1391// int path_below) const
1392// {
1393// if (this == info->static_type)
1394// process_static_type_above_dst(info, dst_ptr, current_ptr, path_below);
1395// else
1396// {
1397// typedef const __base_class_type_info* Iter;
1398// // This is not a static_type and not a dst_type
1399// for (Iter p = __base_info, e = __base_info + __base_count; p < e; ++p)
1400// {
1401// p->search_above_dst(info, dst_ptr, current_ptr, public_path);
1402// // break out early here if you can detect it doesn't matter if you do
1403// }
1404// }
1405// }
1406void
1407__vmi_class_type_info::search_above_dst(__dynamic_cast_info* info,
1408 const void* dst_ptr,
1409 const void* current_ptr,
1410 int path_below,
1411 bool use_strcmp) const
1412{
1413 if (is_equal(this, info->static_type, use_strcmp))
1414 process_static_type_above_dst(info, dst_ptr, current_ptr, path_below);
1415 else
1416 {
1417 typedef const __base_class_type_info* Iter;
1418 // This is not a static_type and not a dst_type
1419 // Save flags so they can be restored when returning to nodes below.
1420 bool found_our_static_ptr = info->found_our_static_ptr;
1421 bool found_any_static_type = info->found_any_static_type;
1422 // We've found a dst_type below with a path to here. If the path
1423 // to here is not public, there may be another path to here that
1424 // is public. So we have to assume that the path to here is public.
1425 // We can stop looking above if:
1426 // 1. We've found a public path to (static_ptr, static_type).
1427 // 2. We've found an ambiguous cast from (static_ptr, static_type) to a dst_type.
1428 // This is detected at the (static_ptr, static_type).
1429 // 3. We can prove that there is no public path to (static_ptr, static_type)
1430 // above here.
1431 const Iter e = __base_info + __base_count;
1432 Iter p = __base_info;
1433 // Zero out found flags
1434 info->found_our_static_ptr = false;
1435 info->found_any_static_type = false;
1436 p->search_above_dst(info, dst_ptr, current_ptr, path_below, use_strcmp);
1437 found_our_static_ptr |= info->found_our_static_ptr;
1438 found_any_static_type |= info->found_any_static_type;
1439 if (++p < e)
1440 {
1441 do
1442 {
1443 if (info->search_done)
1444 break;
1445 if (info->found_our_static_ptr)
1446 {
1447 // If we found what we're looking for, stop looking above.
1448 if (info->path_dst_ptr_to_static_ptr == public_path)
1449 break;
1450 // We found a private path to (static_ptr, static_type)
1451 // If there is no diamond then there is only one path
1452 // to (static_ptr, static_type) from here and we just found it.
1453 if (!(__flags & __diamond_shaped_mask))
1454 break;
1455 }
1456 else if (info->found_any_static_type)
1457 {
1458 // If we found a static_type that isn't the one we're looking
1459 // for, and if there are no repeated types above here,
1460 // then stop looking.
1461 if (!(__flags & __non_diamond_repeat_mask))
1462 break;
1463 }
1464 // Zero out found flags
1465 info->found_our_static_ptr = false;
1466 info->found_any_static_type = false;
1467 p->search_above_dst(info, dst_ptr, current_ptr, path_below, use_strcmp);
1468 found_our_static_ptr |= info->found_our_static_ptr;
1469 found_any_static_type |= info->found_any_static_type;
1470 } while (++p < e);
1471 }
1472 // Restore flags
1473 info->found_our_static_ptr = found_our_static_ptr;
1474 info->found_any_static_type = found_any_static_type;
1475 }
1476}
1477
1478// This is the same algorithm as __vmi_class_type_info::search_above_dst but
1479// simplified to the case that there is only a single base class.
1480void
1481__si_class_type_info::search_above_dst(__dynamic_cast_info* info,
1482 const void* dst_ptr,
1483 const void* current_ptr,
1484 int path_below,
1485 bool use_strcmp) const
1486{
1487 if (is_equal(this, info->static_type, use_strcmp))
1488 process_static_type_above_dst(info, dst_ptr, current_ptr, path_below);
1489 else
1490 __base_type->search_above_dst(info, dst_ptr, current_ptr, path_below, use_strcmp);
1491}
1492
1493// This is the same algorithm as __vmi_class_type_info::search_above_dst but
1494// simplified to the case that there is no base class.
1495void
1496__class_type_info::search_above_dst(__dynamic_cast_info* info,
1497 const void* dst_ptr,
1498 const void* current_ptr,
1499 int path_below,
1500 bool use_strcmp) const
1501{
1502 if (is_equal(this, info->static_type, use_strcmp))
1503 process_static_type_above_dst(info, dst_ptr, current_ptr, path_below);
1504}
1505
1506// The search functions for __base_class_type_info are simply convenience
1507// functions for adjusting the current_ptr and path_below as the search is
1508// passed up to the base class node.
1509
1510void
1511__base_class_type_info::search_above_dst(__dynamic_cast_info* info,
1512 const void* dst_ptr,
1513 const void* current_ptr,
1514 int path_below,
1515 bool use_strcmp) const
1516{
1517 ptrdiff_t offset_to_base = __offset_flags >> __offset_shift;
1518 if (__offset_flags & __virtual_mask)
1519 {
1520 const char* vtable = *static_cast<const char*const*>(current_ptr);
1521 vtable = get_vtable(vtable);
1522 offset_to_base = update_offset_to_base(vtable, offset_to_base);
1523 }
1524 __base_type->search_above_dst(info, dst_ptr,
1525 static_cast<const char*>(current_ptr) + offset_to_base,
1526 (__offset_flags & __public_mask) ?
1527 path_below :
1528 not_public_path,
1529 use_strcmp);
1530}
1531
1532void
1533__base_class_type_info::search_below_dst(__dynamic_cast_info* info,
1534 const void* current_ptr,
1535 int path_below,
1536 bool use_strcmp) const
1537{
1538 ptrdiff_t offset_to_base = __offset_flags >> __offset_shift;
1539 if (__offset_flags & __virtual_mask)
1540 {
1541 const char* vtable = *static_cast<const char*const*>(current_ptr);
1542 vtable = get_vtable(vtable);
1543 offset_to_base = update_offset_to_base(vtable, offset_to_base);
1544 }
1545 __base_type->search_below_dst(info,
1546 static_cast<const char*>(current_ptr) + offset_to_base,
1547 (__offset_flags & __public_mask) ?
1548 path_below :
1549 not_public_path,
1550 use_strcmp);
1551}
1552
1553} // __cxxabiv1
1554

source code of libcxxabi/src/private_typeinfo.cpp