aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/cxxsupp/libcxxrt/dynamic_cast.cc
blob: 6ae3a4035554ee2cd5903cced47a6aca80b25829 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
/* 
 * 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);
}