Source/WTF/wtf/InstanceCounted.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

// This class implements "instance count" management for regression test coverage.
// Since it adds runtime overhead to manage the count variable, the actual
// functionality of the class is limited to debug builds.

namespace WTF {

template<typename T> class InstanceCounted {
public:
    static size_t instanceCount()
    {
#ifndef NDEBUG
        return s_instanceCount;
#else
        return 0;
#endif
    }

#ifndef NDEBUG
protected:
    InstanceCounted()
    {
        ++s_instanceCount;
    }

    InstanceCounted(const InstanceCounted&)
    {
        ++s_instanceCount;
    }

    InstanceCounted(InstanceCounted&&)
    {
        ++s_instanceCount;
    }

    ~InstanceCounted()
    {
        ASSERT(s_instanceCount);
        --s_instanceCount;
    }

private:
    static std::atomic_size_t s_instanceCount;
#endif // NDEBUG
};

#ifndef NDEBUG
template<typename T> std::atomic_size_t InstanceCounted<T>::s_instanceCount;
#endif

} // namespace WTF

using WTF::InstanceCounted;