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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

// 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

// .

#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(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  (src_ptr);

  const vtable_prefix *prefix =

      adjust_pointer  (vtable,

				      -offsetof (vtable_prefix, origin));

  const void *whole_ptr =

      adjust_pointer  (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  (whole_ptr);

  const vtable_prefix *whole_prefix =

    adjust_pointer  (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  (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  (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  (result.dst_ptr);

  // Must be an invalid down cast, or the cross cast wasn't bettered

  return NULL;

}

}