dyncast.cc revision 1.1.1.1.8.1
1// Copyright (C) 1994-2013 Free Software Foundation, Inc. 2// 3// This file is part of GCC. 4// 5// GCC is free software; you can redistribute it and/or modify 6// it under the terms of the GNU General Public License as published by 7// the Free Software Foundation; either version 3, or (at your option) 8// any later version. 9 10// GCC is distributed in the hope that it will be useful, 11// but WITHOUT ANY WARRANTY; without even the implied warranty of 12// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13// GNU General Public License for more details. 14 15// Under Section 7 of GPL version 3, you are granted additional 16// permissions described in the GCC Runtime Library Exception, version 17// 3.1, as published by the Free Software Foundation. 18 19// You should have received a copy of the GNU General Public License and 20// a copy of the GCC Runtime Library Exception along with this program; 21// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 22// <http://www.gnu.org/licenses/>. 23 24#include "tinfo.h" 25 26namespace __cxxabiv1 { 27 28 29// this is the external interface to the dynamic cast machinery 30/* sub: source address to be adjusted; nonnull, and since the 31 * source object is polymorphic, *(void**)sub is a virtual pointer. 32 * src: static type of the source object. 33 * dst: destination type (the "T" in "dynamic_cast<T>(v)"). 34 * src2dst_offset: a static hint about the location of the 35 * source subobject with respect to the complete object; 36 * special negative values are: 37 * -1: no hint 38 * -2: src is not a public base of dst 39 * -3: src is a multiple public base type but never a 40 * virtual base type 41 * otherwise, the src type is a unique public nonvirtual 42 * base type of dst at offset src2dst_offset from the 43 * origin of dst. */ 44extern "C" void * 45__dynamic_cast (const void *src_ptr, // object started from 46 const __class_type_info *src_type, // type of the starting object 47 const __class_type_info *dst_type, // desired target type 48 ptrdiff_t src2dst) // how src and dst are related 49 { 50 const void *vtable = *static_cast <const void *const *> (src_ptr); 51 const vtable_prefix *prefix = 52 adjust_pointer <vtable_prefix> (vtable, 53 -offsetof (vtable_prefix, origin)); 54 const void *whole_ptr = 55 adjust_pointer <void> (src_ptr, prefix->whole_object); 56 const __class_type_info *whole_type = prefix->whole_type; 57 __class_type_info::__dyncast_result result; 58 59 whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public, 60 dst_type, whole_ptr, src_type, src_ptr, result); 61 if (!result.dst_ptr) 62 return NULL; 63 if (contained_public_p (result.dst2src)) 64 // Src is known to be a public base of dst. 65 return const_cast <void *> (result.dst_ptr); 66 if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst))) 67 // Both src and dst are known to be public bases of whole. Found a valid 68 // cross cast. 69 return const_cast <void *> (result.dst_ptr); 70 if (contained_nonvirtual_p (result.whole2src)) 71 // Src is known to be a non-public nonvirtual base of whole, and not a 72 // base of dst. Found an invalid cross cast, which cannot also be a down 73 // cast 74 return NULL; 75 if (result.dst2src == __class_type_info::__unknown) 76 result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr, 77 src_type, src_ptr); 78 if (contained_public_p (result.dst2src)) 79 // Found a valid down cast 80 return const_cast <void *> (result.dst_ptr); 81 // Must be an invalid down cast, or the cross cast wasn't bettered 82 return NULL; 83} 84 85} 86