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