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/*
* Copyright (C) 2017-2020 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 <wtf/ForbidHeapAllocation.h>
namespace JSC {
class VM;
// The only reason we implement DisallowVMEntry as specialization of a template
// is so that we can work around having to #include VM.h, which can hurt build
// time. This defers the cost of #include'ing VM.h to only the clients that
// need it.
template<typename VMType = VM>
class DisallowVMEntryImpl {
WTF_FORBID_HEAP_ALLOCATION;
public:
DisallowVMEntryImpl(VMType& vm)
: m_vm(&vm)
{
m_vm->disallowVMEntryCount++;
}
DisallowVMEntryImpl(const DisallowVMEntryImpl& other)
: m_vm(other.m_vm)
{
m_vm->disallowVMEntryCount++;
}
~DisallowVMEntryImpl()
{
RELEASE_ASSERT(m_vm->disallowVMEntryCount);
m_vm->disallowVMEntryCount--;
m_vm = nullptr;
}
DisallowVMEntryImpl& operator=(const DisallowVMEntryImpl& other)
{
RELEASE_ASSERT(m_vm && m_vm == other.m_vm);
RELEASE_ASSERT(m_vm->disallowVMEntryCount);
// Conceptually, we need to decrement the disallowVMEntryCount of the
// old m_vm, and increment the disallowVMEntryCount of the new m_vm.
// But since the old and the new m_vm should always be the same, the
// decrementing and incrementing cancels out, and there's nothing more
// to do here.
return *this;
}
private:
VMType* m_vm;
};
using DisallowVMEntry = DisallowVMEntryImpl<VM>;
} // namespace JSC
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