7a98470824
MK_LIBCPLUSPLUS=yes to enable). This is a work-in-progress. It works for me, but is not guaranteed to work for anyone else and may eat your dog. To build C++ using libc++, add -stdlib=libc++ to your CXX and LD flags. Bug reports welcome, bug fixes even more welcome... Approved by: dim (mentor)
134 lines
3.5 KiB
C++
134 lines
3.5 KiB
C++
#include "typeinfo.h"
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#include <stdio.h>
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using namespace ABI_NAMESPACE;
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/**
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* Vtable header.
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*/
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struct vtable_header
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{
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/** Offset of the leaf object. */
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ptrdiff_t leaf_offset;
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/** Type of the object. */
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const __class_type_info *type;
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};
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/**
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* Simple macro that does pointer arithmetic in bytes but returns a value of
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* the same type as the original.
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*/
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#define ADD_TO_PTR(x, off) (__typeof__(x))(((char*)x) + off)
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bool __class_type_info::can_cast_to(const struct __class_type_info *other) const
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{
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return this == other;
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}
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void *__class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
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{
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if (this == other)
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{
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return obj;
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}
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return 0;
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}
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bool __si_class_type_info::can_cast_to(const struct __class_type_info *other) const
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{
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return this == other || __base_type->can_cast_to(other);
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}
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void *__si_class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
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{
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if (this == other)
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{
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return obj;
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}
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return __base_type->cast_to(obj, other);
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}
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bool __vmi_class_type_info::can_cast_to(const struct __class_type_info *other) const
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{
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if (this == other)
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{
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return true;
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}
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for (unsigned int i=0 ; i<__base_count ; i++)
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{
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const __base_class_type_info *info = &__base_info[i];
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if(info->isPublic() && info->__base_type->can_cast_to(other))
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{
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return true;
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}
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}
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return false;
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}
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void *__vmi_class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
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{
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if (this == other)
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{
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return obj;
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}
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for (unsigned int i=0 ; i<__base_count ; i++)
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{
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const __base_class_type_info *info = &__base_info[i];
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ptrdiff_t offset = info->offset();
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// If this is a virtual superclass, the offset is stored in the
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// object's vtable at the offset requested; 2.9.5.6.c:
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//
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// 'For a non-virtual base, this is the offset in the object of the
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// base subobject. For a virtual base, this is the offset in the
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// virtual table of the virtual base offset for the virtual base
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// referenced (negative).'
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if (info->isVirtual())
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{
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// Object's vtable
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ptrdiff_t *off = *(ptrdiff_t**)obj;
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// Offset location in vtable
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off = ADD_TO_PTR(off, offset);
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offset = *off;
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}
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void *cast = ADD_TO_PTR(obj, offset);
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if (info->__base_type == other)
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{
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return cast;
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}
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if ((cast = info->__base_type->cast_to(cast, other)))
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{
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return cast;
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}
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}
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return 0;
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}
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/**
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* ABI function used to implement the dynamic_cast<> operator. Some cases of
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* this operator are implemented entirely in the compiler (e.g. to void*).
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* This function implements the dynamic casts of the form dynamic_cast<T>(v).
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* This will be translated to a call to this function with the value v as the
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* first argument. The type id of the static type of v is the second argument
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* and the type id of the destination type (T) is the third argument.
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*
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* The third argument is a hint about the compiler's guess at the correct
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* pointer offset. If this value is negative, then -1 indicates no hint, -2
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* that src is not a public base of dst, and -3 that src is a multiple public
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* base type but never a virtual base type
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*/
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extern "C" void* __dynamic_cast(const void *sub,
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const __class_type_info *src,
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const __class_type_info *dst,
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ptrdiff_t src2dst_offset)
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{
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char *vtable_location = *(char**)sub;
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const vtable_header *header =
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(const vtable_header*)(vtable_location - sizeof(vtable_header));
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void *leaf = ADD_TO_PTR((void*)sub, header->leaf_offset);
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return header->type->cast_to(leaf, dst);
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}
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