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/*
* Copyright (C) 2016-2020 Apple 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 APPLE INC. ``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 APPLE INC. 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.
*/
#pragma once
#include "DestructionMode.h"
#include "EnsureStillAliveHere.h"
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace JSC {
class CellContainer;
class Heap;
class PreciseAllocation;
class MarkedBlock;
class Subspace;
class VM;
struct CellAttributes;
class HeapCell {
public:
enum Kind : int8_t {
JSCell,
JSCellWithIndexingHeader,
Auxiliary
};
HeapCell() { }
// We're intentionally only zapping the bits for the structureID and leaving
// the rest of the cell header bits intact for crash analysis uses.
enum ZapReason : int8_t { Unspecified, Destruction, StopAllocating };
void zap(ZapReason reason)
{
uint32_t* cellWords = std::bit_cast<uint32_t*>(this);
cellWords[0] = 0;
// Leaving cellWords[1] alone for crash analysis if needed.
cellWords[2] = reason;
}
bool isZapped() const { return !*std::bit_cast<const uint32_t*>(this); }
void notifyNeedsDestruction() const;
// isPendingDestruction returns true iff the cell is no longer alive but has not yet
// been swept and therefore its destructor (if it has one) has not yet run.
bool isPendingDestruction();
bool isPreciseAllocation() const;
CellContainer cellContainer() const;
MarkedBlock& markedBlock() const;
PreciseAllocation& preciseAllocation() const;
// If you want performance and you know that your cell is small, you can do this instead:
// ASSERT(!cell->isPreciseAllocation());
// cell->markedBlock().vm()
// We currently only use this hack for callees to make CallFrame::vm() fast. It's not
// recommended to use it for too many other things, since the large allocation cutoff is
// a runtime option and its default value is small (400 bytes).
JSC::Heap* heap() const;
VM& vm() const;
size_t cellSize() const;
CellAttributes cellAttributes() const;
DestructionMode destructionMode() const;
Kind cellKind() const;
Subspace* subspace() const;
// Call use() after the last point where you need `this` pointer to be kept alive. You usually don't
// need to use this, but it might be necessary if you're otherwise referring to an object's innards
// but not the object itself.
ALWAYS_INLINE void use() const
{
ensureStillAliveHere(this);
}
};
inline bool isJSCellKind(HeapCell::Kind kind)
{
return kind == HeapCell::JSCell || kind == HeapCell::JSCellWithIndexingHeader;
}
inline bool mayHaveIndexingHeader(HeapCell::Kind kind)
{
return kind == HeapCell::Auxiliary || kind == HeapCell::JSCellWithIndexingHeader;
}
} // namespace JSC
namespace WTF {
class PrintStream;
void printInternal(PrintStream&, JSC::HeapCell::Kind);
} // namespace WTF
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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