libcxxrt

dynamic_cast.cc (6327B)

---

 /* 
  * Copyright 2010-2011 PathScale, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright notice,
  *    this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  *    this list of conditions and the following disclaimer in the documentation
  *    and/or other materials provided with the distribution.
  * 
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
  * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "typeinfo.h"
 #include <stdio.h>
 
 using namespace ABI_NAMESPACE;
 
 /**
  * Vtable header.
  */
 struct vtable_header
 {
 	/** Offset of the leaf object. */
 	ptrdiff_t leaf_offset;
 	/** Type of the object. */
 	const __class_type_info *type;
 };
 
 /**
  * Simple macro that does pointer arithmetic in bytes but returns a value of
  * the same type as the original.
  */
 #define ADD_TO_PTR(x, off) reinterpret_cast<__typeof__(x)>(reinterpret_cast<char*>(x) + off)
 
 bool std::type_info::__do_catch(std::type_info const *ex_type,
                                 void **exception_object,
                                 unsigned int outer) const
 {
 	const type_info *type = this;
 
 	if (type == ex_type)
 	{
 		return true;
 	}
 	if (const __class_type_info *cti = dynamic_cast<const __class_type_info *>(type))
 	{
 		return ex_type->__do_upcast(cti, exception_object);
 	}
 	return false;
 }
 
 bool __pbase_type_info::__do_catch(std::type_info const *ex_type,
                                    void **exception_object,
                                    unsigned int outer) const
 {
 	if (ex_type == this)
 	{
 		return true;
 	}
 	if (!ex_type->__is_pointer_p())
 	{
 		// Can't catch a non-pointer type in a pointer catch
 		return false;
 	}
 
 	if (!(outer & 1))
 	{
 		// If the low bit is cleared on this means that we've gone
 		// through a pointer that is not const qualified.
 		return false;
 	}
 	// Clear the low bit on outer if we're not const qualified.
 	if (!(__flags & __const_mask))
 	{
 		outer &= ~1;
 	}
 
 	const __pbase_type_info *ptr_type =
 	        static_cast<const __pbase_type_info*>(ex_type);
 
 	if (ptr_type->__flags & ~__flags)
 	{
 		// Handler pointer is less qualified
 		return false;
 	}
 
 	// Special case for void* handler.  
 	if(*__pointee == typeid(void))
 	{
 		return true;
 	}
 
 	return __pointee->__do_catch(ptr_type->__pointee, exception_object, outer);
 }
 
 void *__class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
 {
 	if (this == other)
 	{
 		return obj;
 	}
 	return 0;
 }
 
 void *__si_class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
 {
 	if (this == other)
 	{
 		return obj;
 	}
 	return __base_type->cast_to(obj, other);
 }
 bool __si_class_type_info::__do_upcast(const __class_type_info *target,
                                      void **thrown_object) const
 {
 	if (this == target)
 	{
 		return true;
 	}
 	return __base_type->__do_upcast(target, thrown_object);
 }
 
 void *__vmi_class_type_info::cast_to(void *obj, const struct __class_type_info *other) const
 {
 	if (__do_upcast(other, &obj))
 	{
 		return obj;
 	}
 	return 0;
 }
 
 bool __vmi_class_type_info::__do_upcast(const __class_type_info *target,
 		                      void **thrown_object) const
 {
 	if (this == target)
 	{
 		return true;
 	}
 	for (unsigned int i=0 ; i<__base_count ; i++)
 	{
 		const __base_class_type_info *info = &__base_info[i];
 		ptrdiff_t offset = info->offset();
 		// If this is a virtual superclass, the offset is stored in the
 		// object's vtable at the offset requested; 2.9.5.6.c:
 		//
 		// 'For a non-virtual base, this is the offset in the object of the
 		// base subobject. For a virtual base, this is the offset in the
 		// virtual table of the virtual base offset for the virtual base
 		// referenced (negative).'
 
 		void *obj = *thrown_object;
 		if (info->isVirtual())
 		{
 			// Object's vtable
 			ptrdiff_t *off = *static_cast<ptrdiff_t**>(obj);
 			// Offset location in vtable
 			off = ADD_TO_PTR(off, offset);
 			offset = *off;
 		}
 		void *cast = ADD_TO_PTR(obj, offset);
 
 		if (info->__base_type == target ||
 		    (info->__base_type->__do_upcast(target, &cast)))
 		{
 			*thrown_object = cast;
 			return true;
 		}
 	}
 	return 0;
 }
 
 
 /**
  * ABI function used to implement the dynamic_cast<> operator.  Some cases of
  * this operator are implemented entirely in the compiler (e.g. to void*).
  * This function implements the dynamic casts of the form dynamic_cast<T>(v).
  * This will be translated to a call to this function with the value v as the
  * first argument.  The type id of the static type of v is the second argument
  * and the type id of the destination type (T) is the third argument.
  *
  * The third argument is a hint about the compiler's guess at the correct
  * pointer offset.  If this value is negative, then -1 indicates no hint, -2
  * that src is not a public base of dst, and -3 that src is a multiple public
  * base type but never a virtual base type
  */
 extern "C" void* __dynamic_cast(const void *sub,
                                 const __class_type_info *src,
                                 const __class_type_info *dst,
                                 ptrdiff_t src2dst_offset)
 {
 	const char *vtable_location = *static_cast<const char * const *>(sub);
 	const vtable_header *header =
 		reinterpret_cast<const vtable_header*>(vtable_location - sizeof(vtable_header));
 	void *leaf = ADD_TO_PTR(const_cast<void *>(sub), header->leaf_offset);
 	return header->type->cast_to(leaf, dst);
 }