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98 lines
4.2 KiB
C++
98 lines
4.2 KiB
C++
// Copyright (C) 1994-2017 Free Software Foundation, Inc.
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//
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// This file is part of GCC.
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//
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// GCC is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// GCC is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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#include "tinfo.h"
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namespace __cxxabiv1 {
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// this is the external interface to the dynamic cast machinery
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/* sub: source address to be adjusted; nonnull, and since the
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* source object is polymorphic, *(void**)sub is a virtual pointer.
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* src: static type of the source object.
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* dst: destination type (the "T" in "dynamic_cast<T>(v)").
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* src2dst_offset: a static hint about the location of the
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* source subobject with respect to the complete object;
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* special negative values are:
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* -1: no hint
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* -2: src is not a public base of dst
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* -3: src is a multiple public base type but never a
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* virtual base type
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* otherwise, the src type is a unique public nonvirtual
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* base type of dst at offset src2dst_offset from the
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* origin of dst. */
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extern "C" void *
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__dynamic_cast (const void *src_ptr, // object started from
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const __class_type_info *src_type, // type of the starting object
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const __class_type_info *dst_type, // desired target type
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ptrdiff_t src2dst) // how src and dst are related
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{
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const void *vtable = *static_cast <const void *const *> (src_ptr);
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const vtable_prefix *prefix =
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adjust_pointer <vtable_prefix> (vtable,
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-offsetof (vtable_prefix, origin));
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const void *whole_ptr =
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adjust_pointer <void> (src_ptr, prefix->whole_object);
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const __class_type_info *whole_type = prefix->whole_type;
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__class_type_info::__dyncast_result result;
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// If the whole object vptr doesn't refer to the whole object type, we're
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// in the middle of constructing a primary base, and src is a separate
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// base. This has undefined behavior and we can't find anything outside
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// of the base we're actually constructing, so fail now rather than
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// segfault later trying to use a vbase offset that doesn't exist.
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const void *whole_vtable = *static_cast <const void *const *> (whole_ptr);
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const vtable_prefix *whole_prefix =
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adjust_pointer <vtable_prefix> (whole_vtable,
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-offsetof (vtable_prefix, origin));
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if (whole_prefix->whole_type != whole_type)
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return NULL;
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whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public,
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dst_type, whole_ptr, src_type, src_ptr, result);
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if (!result.dst_ptr)
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return NULL;
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if (contained_public_p (result.dst2src))
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// Src is known to be a public base of dst.
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return const_cast <void *> (result.dst_ptr);
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if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst)))
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// Both src and dst are known to be public bases of whole. Found a valid
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// cross cast.
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return const_cast <void *> (result.dst_ptr);
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if (contained_nonvirtual_p (result.whole2src))
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// Src is known to be a non-public nonvirtual base of whole, and not a
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// base of dst. Found an invalid cross cast, which cannot also be a down
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// cast
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return NULL;
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if (result.dst2src == __class_type_info::__unknown)
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result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr,
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src_type, src_ptr);
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if (contained_public_p (result.dst2src))
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// Found a valid down cast
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return const_cast <void *> (result.dst_ptr);
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// Must be an invalid down cast, or the cross cast wasn't bettered
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return NULL;
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}
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}
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