1 // Copyright (C) 1994, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2007, 2009 2 // Free Software Foundation 3 // 4 // This file is part of GCC. 5 // 6 // GCC is free software; you can redistribute it and/or modify 7 // it under the terms of the GNU General Public License as published by 8 // the Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // GCC is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 #include "tinfo.h" 26 27 namespace __cxxabiv1 { 28 29 30 // this is the external interface to the dynamic cast machinery 31 /* sub: source address to be adjusted; nonnull, and since the 32 * source object is polymorphic, *(void**)sub is a virtual pointer. 33 * src: static type of the source object. 34 * dst: destination type (the "T" in "dynamic_cast<T>(v)"). 35 * src2dst_offset: a static hint about the location of the 36 * source subobject with respect to the complete object; 37 * special negative values are: 38 * -1: no hint 39 * -2: src is not a public base of dst 40 * -3: src is a multiple public base type but never a 41 * virtual base type 42 * otherwise, the src type is a unique public nonvirtual 43 * base type of dst at offset src2dst_offset from the 44 * origin of dst. */ 45 extern "C" void * 46 __dynamic_cast (const void *src_ptr, // object started from 47 const __class_type_info *src_type, // type of the starting object 48 const __class_type_info *dst_type, // desired target type 49 ptrdiff_t src2dst) // how src and dst are related 50 { 51 const void *vtable = *static_cast <const void *const *> (src_ptr); 52 const vtable_prefix *prefix = 53 adjust_pointer <vtable_prefix> (vtable, 54 -offsetof (vtable_prefix, origin)); 55 const void *whole_ptr = 56 adjust_pointer <void> (src_ptr, prefix->whole_object); 57 const __class_type_info *whole_type = prefix->whole_type; 58 __class_type_info::__dyncast_result result; 59 60 whole_type->__do_dyncast (src2dst, __class_type_info::__contained_public, 61 dst_type, whole_ptr, src_type, src_ptr, result); 62 if (!result.dst_ptr) 63 return NULL; 64 if (contained_public_p (result.dst2src)) 65 // Src is known to be a public base of dst. 66 return const_cast <void *> (result.dst_ptr); 67 if (contained_public_p (__class_type_info::__sub_kind (result.whole2src & result.whole2dst))) 68 // Both src and dst are known to be public bases of whole. Found a valid 69 // cross cast. 70 return const_cast <void *> (result.dst_ptr); 71 if (contained_nonvirtual_p (result.whole2src)) 72 // Src is known to be a non-public nonvirtual base of whole, and not a 73 // base of dst. Found an invalid cross cast, which cannot also be a down 74 // cast 75 return NULL; 76 if (result.dst2src == __class_type_info::__unknown) 77 result.dst2src = dst_type->__find_public_src (src2dst, result.dst_ptr, 78 src_type, src_ptr); 79 if (contained_public_p (result.dst2src)) 80 // Found a valid down cast 81 return const_cast <void *> (result.dst_ptr); 82 // Must be an invalid down cast, or the cross cast wasn't bettered 83 return NULL; 84 } 85 86 } 87