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f1717362 | 1 | // Copyright (C) 1994-2016 Free Software Foundation, Inc. |
f779f82c | 2 | // |
3 | // This file is part of GCC. | |
4 | // | |
5 | // GCC is free software; you can redistribute it and/or modify | |
6 | // it under the terms of the GNU General Public License as published by | |
6bc9506f | 7 | // the Free Software Foundation; either version 3, or (at your option) |
f779f82c | 8 | // any later version. |
9 | ||
10 | // GCC is distributed in the hope that it will be useful, | |
11 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | // GNU General Public License for more details. | |
14 | ||
6bc9506f | 15 | // Under Section 7 of GPL version 3, you are granted additional |
16 | // permissions described in the GCC Runtime Library Exception, version | |
17 | // 3.1, as published by the Free Software Foundation. | |
f779f82c | 18 | |
6bc9506f | 19 | // You should have received a copy of the GNU General Public License and |
20 | // a copy of the GCC Runtime Library Exception along with this program; | |
21 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
22 | // <http://www.gnu.org/licenses/>. | |
f779f82c | 23 | |
24 | #include "tinfo.h" | |
25 | ||
26 | namespace __cxxabiv1 { | |
27 | ||
28 | ||
29 | // this is the external interface to the dynamic cast machinery | |
4f0132f2 | 30 | /* sub: source address to be adjusted; nonnull, and since the |
31 | * source object is polymorphic, *(void**)sub is a virtual pointer. | |
32 | * src: static type of the source object. | |
33 | * dst: destination type (the "T" in "dynamic_cast<T>(v)"). | |
34 | * src2dst_offset: a static hint about the location of the | |
35 | * source subobject with respect to the complete object; | |
36 | * special negative values are: | |
37 | * -1: no hint | |
38 | * -2: src is not a public base of dst | |
39 | * -3: src is a multiple public base type but never a | |
40 | * virtual base type | |
41 | * otherwise, the src type is a unique public nonvirtual | |
42 | * base type of dst at offset src2dst_offset from the | |
43 | * origin of dst. */ | |
f779f82c | 44 | extern "C" void * |
45 | __dynamic_cast (const void *src_ptr, // object started from | |
46 | const __class_type_info *src_type, // type of the starting object | |
47 | const __class_type_info *dst_type, // desired target type | |
48 | ptrdiff_t src2dst) // how src and dst are related | |
4f0132f2 | 49 | { |
f779f82c | 50 | const void *vtable = *static_cast <const void *const *> (src_ptr); |
51 | const vtable_prefix *prefix = | |
52 | adjust_pointer <vtable_prefix> (vtable, | |
53 | -offsetof (vtable_prefix, origin)); | |
54 | const void *whole_ptr = | |
55 | adjust_pointer <void> (src_ptr, prefix->whole_object); | |
56 | const __class_type_info *whole_type = prefix->whole_type; | |
57 | __class_type_info::__dyncast_result result; | |
b42f9c36 | 58 | |
59 | // If the whole object vptr doesn't refer to the whole object type, we're | |
60 | // in the middle of constructing a primary base, and src is a separate | |
61 | // base. This has undefined behavior and we can't find anything outside | |
62 | // of the base we're actually constructing, so fail now rather than | |
63 | // segfault later trying to use a vbase offset that doesn't exist. | |
64 | const void *whole_vtable = *static_cast <const void *const *> (whole_ptr); | |
65 | const vtable_prefix *whole_prefix = | |
66 | adjust_pointer <vtable_prefix> (whole_vtable, | |
67 | -offsetof (vtable_prefix, origin)); | |
68 | if (whole_prefix->whole_type != whole_type) | |
69 | return NULL; | |
f779f82c | 70 | |
71 | whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public, | |
72 | dst_type, whole_ptr, src_type, src_ptr, result); | |
73 | if (!result.dst_ptr) | |
74 | return NULL; | |
75 | if (contained_public_p (result.dst2src)) | |
76 | // Src is known to be a public base of dst. | |
77 | return const_cast <void *> (result.dst_ptr); | |
78 | if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst))) | |
79 | // Both src and dst are known to be public bases of whole. Found a valid | |
80 | // cross cast. | |
81 | return const_cast <void *> (result.dst_ptr); | |
82 | if (contained_nonvirtual_p (result.whole2src)) | |
83 | // Src is known to be a non-public nonvirtual base of whole, and not a | |
84 | // base of dst. Found an invalid cross cast, which cannot also be a down | |
85 | // cast | |
86 | return NULL; | |
87 | if (result.dst2src == __class_type_info::__unknown) | |
88 | result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr, | |
89 | src_type, src_ptr); | |
90 | if (contained_public_p (result.dst2src)) | |
91 | // Found a valid down cast | |
92 | return const_cast <void *> (result.dst_ptr); | |
93 | // Must be an invalid down cast, or the cross cast wasn't bettered | |
94 | return NULL; | |
95 | } | |
96 | ||
97 | } |