Source/JavaScriptCore/tools/StackTrace.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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <wtf/PrintStream.h>

namespace JSC {

class StackTrace {
    WTF_MAKE_FAST_ALLOCATED;
public:
    static StackTrace* captureStackTrace(int maxFrames);

    int size() const { return m_size; }

    void dump(PrintStream&) const;

private:
    inline static size_t instanceSize(int capacity);

    StackTrace() { }

    // We structure the top fields this way because the underlying stack capture
    // facility will capture from the top of the stack, and we'll need to skip the
    // top 2 frame which is of no interest. Setting up the fields layout this way
    // allows us to capture the stack in place and minimize space wastage.
    union {
        struct {
            int m_size { 0 };
            int m_capacity;
        };
        struct {
            void* m_skippedFrame0;
            void* m_skippedFrame1;
        };
    };
    void* m_stack[1];
};

} // namespace JSC