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// Copyright (C) 1994-2015 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
// 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
// <>.
#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,
-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,
-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;