Source/JavaScriptCore/runtime/DisallowVMReentry.h

/*
 * Copyright (C) 2017 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 "DisallowScope.h"
#include <wtf/NeverDestroyed.h>
#include <wtf/ThreadSpecific.h>

namespace JSC {

class DisallowVMReentry : public DisallowScope<DisallowVMReentry> {
    WTF_MAKE_NONCOPYABLE(DisallowVMReentry);
    typedef DisallowScope<DisallowVMReentry> Base;
public:
#ifdef NDEBUG

    ALWAYS_INLINE DisallowVMReentry(bool = false) { }
    ALWAYS_INLINE static void initialize() { }

#else // not NDEBUG

    DisallowVMReentry(bool enabled = true)
        : Base(enabled)
    { }

    static void initialize()
    {
        s_scopeReentryCount.construct();
    }

private:
    static unsigned scopeReentryCount()
    {
        return *s_scopeReentryCount.get();
    }
    static void setScopeReentryCount(unsigned value)
    {
        *s_scopeReentryCount.get() = value;
    }

    JS_EXPORT_PRIVATE static LazyNeverDestroyed<ThreadSpecific<unsigned, WTF::CanBeGCThread::True>> s_scopeReentryCount;

#endif // NDEBUG

    friend class DisallowScope<DisallowVMReentry>;
};

} // namespace JSC