99 lines
4.3 KiB
C++
99 lines
4.3 KiB
C++
// Copyright (C) 1994-2021 Free Software Foundation, Inc.
|
|
//
|
|
// This file is part of GCC.
|
|
//
|
|
// GCC is free software; you can redistribute it and/or modify
|
|
// it under the terms of the GNU General Public License as published by
|
|
// the Free Software Foundation; either version 3, or (at your option)
|
|
// any later version.
|
|
|
|
// GCC is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
// GNU General Public License for more details.
|
|
|
|
// Under Section 7 of GPL version 3, you are granted additional
|
|
// permissions described in the GCC Runtime Library Exception, version
|
|
// 3.1, as published by the Free Software Foundation.
|
|
|
|
// You should have received a copy of the GNU General Public License and
|
|
// a copy of the GCC Runtime Library Exception along with this program;
|
|
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
|
|
// <http://www.gnu.org/licenses/>.
|
|
|
|
#include "tinfo.h"
|
|
|
|
namespace __cxxabiv1 {
|
|
|
|
|
|
// this is the external interface to the dynamic cast machinery
|
|
/* sub: source address to be adjusted; nonnull, and since the
|
|
* source object is polymorphic, *(void**)sub is a virtual pointer.
|
|
* src: static type of the source object.
|
|
* dst: destination type (the "T" in "dynamic_cast<T>(v)").
|
|
* src2dst_offset: a static hint about the location of the
|
|
* source subobject with respect to the complete object;
|
|
* special negative values are:
|
|
* -1: no hint
|
|
* -2: src is not a public base of dst
|
|
* -3: src is a multiple public base type but never a
|
|
* virtual base type
|
|
* otherwise, the src type is a unique public nonvirtual
|
|
* base type of dst at offset src2dst_offset from the
|
|
* origin of dst. */
|
|
extern "C" void *
|
|
__dynamic_cast (const void *src_ptr, // object started from
|
|
const __class_type_info *src_type, // type of the starting object
|
|
const __class_type_info *dst_type, // desired target type
|
|
ptrdiff_t src2dst) // how src and dst are related
|
|
{
|
|
const void *vtable = *static_cast <const void *const *> (src_ptr);
|
|
const vtable_prefix *prefix =
|
|
(adjust_pointer <vtable_prefix>
|
|
(vtable, -ptrdiff_t (offsetof (vtable_prefix, origin))));
|
|
const void *whole_ptr =
|
|
adjust_pointer <void> (src_ptr, prefix->whole_object);
|
|
const __class_type_info *whole_type = prefix->whole_type;
|
|
__class_type_info::__dyncast_result result;
|
|
|
|
// If the whole object vptr doesn't refer to the whole object type, we're
|
|
// in the middle of constructing a primary base, and src is a separate
|
|
// base. This has undefined behavior and we can't find anything outside
|
|
// of the base we're actually constructing, so fail now rather than
|
|
// segfault later trying to use a vbase offset that doesn't exist.
|
|
const void *whole_vtable = *static_cast <const void *const *> (whole_ptr);
|
|
const vtable_prefix *whole_prefix =
|
|
(adjust_pointer <vtable_prefix>
|
|
(whole_vtable, -ptrdiff_t (offsetof (vtable_prefix, origin))));
|
|
if (whole_prefix->whole_type != whole_type)
|
|
return NULL;
|
|
|
|
whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public,
|
|
dst_type, whole_ptr, src_type, src_ptr, result);
|
|
if (!result.dst_ptr)
|
|
return NULL;
|
|
if (contained_public_p (result.dst2src))
|
|
// Src is known to be a public base of dst.
|
|
return const_cast <void *> (result.dst_ptr);
|
|
if (contained_public_p (__class_type_info::__sub_kind
|
|
(result.whole2src & result.whole2dst)))
|
|
// Both src and dst are known to be public bases of whole. Found a valid
|
|
// cross cast.
|
|
return const_cast <void *> (result.dst_ptr);
|
|
if (contained_nonvirtual_p (result.whole2src))
|
|
// Src is known to be a non-public nonvirtual base of whole, and not a
|
|
// base of dst. Found an invalid cross cast, which cannot also be a down
|
|
// cast
|
|
return NULL;
|
|
if (result.dst2src == __class_type_info::__unknown)
|
|
result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr,
|
|
src_type, src_ptr);
|
|
if (contained_public_p (result.dst2src))
|
|
// Found a valid down cast
|
|
return const_cast <void *> (result.dst_ptr);
|
|
// Must be an invalid down cast, or the cross cast wasn't bettered
|
|
return NULL;
|
|
}
|
|
|
|
}
|