1/*
2 * Copyright (C) 2016-2018 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include "DestructionMode.h"
29
30namespace JSC {
31
32class CellContainer;
33class Heap;
34class LargeAllocation;
35class MarkedBlock;
36class Subspace;
37class VM;
38struct CellAttributes;
39
40class HeapCell {
41public:
42 enum Kind : int8_t {
43 JSCell,
44 JSCellWithInteriorPointers,
45 Auxiliary
46 };
47
48 HeapCell() { }
49
50 void zap() { *reinterpret_cast_ptr<uintptr_t**>(this) = 0; }
51 bool isZapped() const { return !*reinterpret_cast_ptr<uintptr_t* const*>(this); }
52
53 bool isLive();
54
55 bool isLargeAllocation() const;
56 CellContainer cellContainer() const;
57 MarkedBlock& markedBlock() const;
58 LargeAllocation& largeAllocation() const;
59
60 // If you want performance and you know that your cell is small, you can do this instead:
61 // ASSERT(!cell->isLargeAllocation());
62 // cell->markedBlock().vm()
63 // We currently only use this hack for callees to make ExecState::vm() fast. It's not
64 // recommended to use it for too many other things, since the large allocation cutoff is
65 // a runtime option and its default value is small (400 bytes).
66 Heap* heap() const;
67 VM* vm() const;
68
69 size_t cellSize() const;
70 CellAttributes cellAttributes() const;
71 DestructionMode destructionMode() const;
72 Kind cellKind() const;
73 Subspace* subspace() const;
74
75 // Call use() after the last point where you need `this` pointer to be kept alive. You usually don't
76 // need to use this, but it might be necessary if you're otherwise referring to an object's innards
77 // but not the object itself.
78#if COMPILER(GCC_COMPATIBLE)
79 void use() const
80 {
81 asm volatile ("" : : "r"(this) : "memory");
82 }
83#else
84 void use() const;
85#endif
86};
87
88inline bool isJSCellKind(HeapCell::Kind kind)
89{
90 return kind == HeapCell::JSCell || kind == HeapCell::JSCellWithInteriorPointers;
91}
92
93inline bool hasInteriorPointers(HeapCell::Kind kind)
94{
95 return kind == HeapCell::Auxiliary || kind == HeapCell::JSCellWithInteriorPointers;
96}
97
98} // namespace JSC
99
100namespace WTF {
101
102class PrintStream;
103
104void printInternal(PrintStream&, JSC::HeapCell::Kind);
105
106} // namespace WTF
107
108