1// Copyright (C) 1994, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2007, 2009
2// Free Software Foundation
3//
4// This file is part of GCC.
5//
6// GCC is free software; you can redistribute it and/or modify
7// it under the terms of the GNU General Public License as published by
8// the Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// GCC is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25#include "tinfo.h"
26
27namespace __cxxabiv1 {
28
29
30// this is the external interface to the dynamic cast machinery
31/* sub: source address to be adjusted; nonnull, and since the
32 *      source object is polymorphic, *(void**)sub is a virtual pointer.
33 * src: static type of the source object.
34 * dst: destination type (the "T" in "dynamic_cast<T>(v)").
35 * src2dst_offset: a static hint about the location of the
36 *    source subobject with respect to the complete object;
37 *    special negative values are:
38 *       -1: no hint
39 *       -2: src is not a public base of dst
40 *       -3: src is a multiple public base type but never a
41 *           virtual base type
42 *    otherwise, the src type is a unique public nonvirtual
43 *    base type of dst at offset src2dst_offset from the
44 *    origin of dst.  */
45extern "C" void *
46__dynamic_cast (const void *src_ptr,    // object started from
47                const __class_type_info *src_type, // type of the starting object
48                const __class_type_info *dst_type, // desired target type
49                ptrdiff_t src2dst) // how src and dst are related
50  {
51  const void *vtable = *static_cast <const void *const *> (src_ptr);
52  const vtable_prefix *prefix =
53      adjust_pointer <vtable_prefix> (vtable,
54				      -offsetof (vtable_prefix, origin));
55  const void *whole_ptr =
56      adjust_pointer <void> (src_ptr, prefix->whole_object);
57  const __class_type_info *whole_type = prefix->whole_type;
58  __class_type_info::__dyncast_result result;
59
60  whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public,
61                            dst_type, whole_ptr, src_type, src_ptr, result);
62  if (!result.dst_ptr)
63    return NULL;
64  if (contained_public_p (result.dst2src))
65    // Src is known to be a public base of dst.
66    return const_cast <void *> (result.dst_ptr);
67  if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst)))
68    // Both src and dst are known to be public bases of whole. Found a valid
69    // cross cast.
70    return const_cast <void *> (result.dst_ptr);
71  if (contained_nonvirtual_p (result.whole2src))
72    // Src is known to be a non-public nonvirtual base of whole, and not a
73    // base of dst. Found an invalid cross cast, which cannot also be a down
74    // cast
75    return NULL;
76  if (result.dst2src == __class_type_info::__unknown)
77    result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr,
78                                                  src_type, src_ptr);
79  if (contained_public_p (result.dst2src))
80    // Found a valid down cast
81    return const_cast <void *> (result.dst_ptr);
82  // Must be an invalid down cast, or the cross cast wasn't bettered
83  return NULL;
84}
85
86}
87