wtf/CheckedArithmetic.h delegates to base/numerics/safe_math.h.

third_party/WebKit/Source/wtf/CheckedArithmetic.h

-/*
- * Copyright (C) 2011 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.
- */
-
-#ifndef CheckedArithmetic_h
-#define CheckedArithmetic_h
-
-#include "wtf/Assertions.h"
-#include "wtf/TypeTraits.h"
-
-#include <limits>
-#include <stdint.h>
-
-/* Checked<T>
- *
- * This class provides a mechanism to perform overflow-safe integer arithmetic
- * without having to manually ensure that you have all the required bounds checks
- * directly in your code.
- *
- * There are two modes of operation:
- *  - The default is Checked<T, CrashOnOverflow>, and crashes at the point
- *    and overflow has occurred.
- *  - The alternative is Checked<T, RecordOverflow>, which uses an additional
- *    byte of storage to track whether an overflow has occurred, subsequent
- *    unchecked operations will crash if an overflow has occured
- *
- * It is possible to provide a custom overflow handler, in which case you need
- * to support these functions:
- *  - void overflowed();
- *    This function is called when an operation has produced an overflow.
- *  - bool hasOverflowed();
- *    This function must return true if overflowed() has been called on an
- *    instance and false if it has not.
- *  - void clearOverflow();
- *    Used to reset overflow tracking when a value is being overwritten with
- *    a new value.
- *
- * Checked<T> works for all integer types, with the following caveats:
- *  - Mixing signedness of operands is only supported for types narrower than
- *    64bits.
- *  - It does have a performance impact, so tight loops may want to be careful
- *    when using it.
- *
- */
-
-namespace WTF {
-
-enum class CheckedState {
-    DidOverflow,
-    DidNotOverflow
-};
-
-class CrashOnOverflow {
-protected:
-    NO_RETURN_DUE_TO_CRASH void overflowed()
-    {
-        CRASH();
-    }
-
-    void clearOverflow() { }
-
-public:
-    bool hasOverflowed() const { return false; }
-};
-
-class RecordOverflow {
-protected:
-    RecordOverflow()
-        : m_overflowed(false)
-    {
-    }
-
-    void overflowed()
-    {
-        m_overflowed = true;
-    }
-
-    void clearOverflow()
-    {
-        m_overflowed = false;
-    }
-
-public:
-    bool hasOverflowed() const { return m_overflowed; }
-
-private:
-    unsigned char m_overflowed;
-};
-
-template <typename T, class OverflowHandler = CrashOnOverflow> class Checked;
-template <typename T> struct RemoveChecked;
-template <typename T> struct RemoveChecked<Checked<T>>;
-
-template <typename Target, typename Source, bool targetSigned = std::numeric_limits<Target>::is_signed, bool sourceSigned = std::numeric_limits<Source>::is_signed> struct BoundsChecker;
-template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, false> {
-    static bool inBounds(Source value)
-    {
-        // Same signedness so implicit type conversion will always increase precision
-        // to widest type
-        return value <= std::numeric_limits<Target>::max();
-    }
-};
-
-template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, true> {
-    static bool inBounds(Source value)
-    {
-        // Same signedness so implicit type conversion will always increase precision
-        // to widest type
-        return std::numeric_limits<Target>::min() <= value && value <= std::numeric_limits<Target>::max();
-    }
-};
-
-template <typename Target, typename Source> struct BoundsChecker<Target, Source, false, true> {
-    static bool inBounds(Source value)
-    {
-        // Target is unsigned so any value less than zero is clearly unsafe
-        if (value < 0)
-            return false;
-        // If our (unsigned) Target is the same or greater width we can
-        // convert value to type Target without losing precision
-        if (sizeof(Target) >= sizeof(Source))
-            return static_cast<Target>(value) <= std::numeric_limits<Target>::max();
-        // The signed Source type has greater precision than the target so
-        // max(Target) -> Source will widen.
-        return value <= static_cast<Source>(std::numeric_limits<Target>::max());
-    }
-};
-
-template <typename Target, typename Source> struct BoundsChecker<Target, Source, true, false> {
-    static bool inBounds(Source value)
-    {
-        // Signed target with an unsigned source
-        if (sizeof(Target) <= sizeof(Source))
-            return value <= static_cast<Source>(std::numeric_limits<Target>::max());
-        // Target is Wider than Source so we're guaranteed to fit any value in
-        // unsigned Source
-        return true;
-    }
-};
-
-template <typename Target, typename Source, bool CanElide = std::is_same<Target, Source>::value || (sizeof(Target) > sizeof(Source)) > struct BoundsCheckElider;
-template <typename Target, typename Source> struct BoundsCheckElider<Target, Source, true> {
-    static bool inBounds(Source) { return true; }
-};
-template <typename Target, typename Source> struct BoundsCheckElider<Target, Source, false> : public BoundsChecker<Target, Source> {
-};
-
-template <typename Target, typename Source> static inline bool isInBounds(Source value)
-{
-    return BoundsCheckElider<Target, Source>::inBounds(value);
-}
-
-template <typename T> struct RemoveChecked {
-    typedef T CleanType;
-    static const CleanType DefaultValue = 0;
-};
-
-template <typename T> struct RemoveChecked<Checked<T, CrashOnOverflow>> {
-    typedef typename RemoveChecked<T>::CleanType CleanType;
-    static const CleanType DefaultValue = 0;
-};
-
-template <typename T> struct RemoveChecked<Checked<T, RecordOverflow>> {
-    typedef typename RemoveChecked<T>::CleanType CleanType;
-    static const CleanType DefaultValue = 0;
-};
-
-// The ResultBase and SignednessSelector are used to workaround typeof not being
-// available in MSVC
-template <typename U, typename V, bool uIsBigger = (sizeof(U) > sizeof(V)), bool sameSize = (sizeof(U) == sizeof(V))> struct ResultBase;
-template <typename U, typename V> struct ResultBase<U, V, true, false> {
-    typedef U ResultType;
-};
-
-template <typename U, typename V> struct ResultBase<U, V, false, false> {
-    typedef V ResultType;
-};
-
-template <typename U> struct ResultBase<U, U, false, true> {
-    typedef U ResultType;
-};
-
-template <typename U, typename V, bool uIsSigned = std::numeric_limits<U>::is_signed, bool vIsSigned = std::numeric_limits<V>::is_signed> struct SignednessSelector;
-template <typename U, typename V> struct SignednessSelector<U, V, true, true> {
-    typedef U ResultType;
-};
-
-template <typename U, typename V> struct SignednessSelector<U, V, false, false> {
-    typedef U ResultType;
-};
-
-template <typename U, typename V> struct SignednessSelector<U, V, true, false> {
-    typedef V ResultType;
-};
-
-template <typename U, typename V> struct SignednessSelector<U, V, false, true> {
-    typedef U ResultType;
-};
-
-template <typename U, typename V> struct ResultBase<U, V, false, true> {
-    typedef typename SignednessSelector<U, V>::ResultType ResultType;
-};
-
-template <typename U, typename V> struct Result : ResultBase<typename RemoveChecked<U>::CleanType, typename RemoveChecked<V>::CleanType> {
-};
-
-template <typename LHS, typename RHS, typename ResultType = typename Result<LHS, RHS>::ResultType,
-    bool lhsSigned = std::numeric_limits<LHS>::is_signed, bool rhsSigned = std::numeric_limits<RHS>::is_signed> struct ArithmeticOperations;
-
-template <typename LHS, typename RHS, typename ResultType> struct ArithmeticOperations<LHS, RHS, ResultType, true, true> {
-    // LHS and RHS are signed types
-
-    // Helper function
-    static inline bool signsMatch(LHS lhs, RHS rhs)
-    {
-        return (lhs ^ rhs) >= 0;
-    }
-
-    static inline bool add(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        if (signsMatch(lhs, rhs)) {
-            if (lhs >= 0) {
-                if ((std::numeric_limits<ResultType>::max() - rhs) < lhs)
-                    return false;
-            } else {
-                ResultType temp = lhs - std::numeric_limits<ResultType>::min();
-                if (rhs < -temp)
-                    return false;
-            }
-        } // if the signs do not match this operation can't overflow
-        result = static_cast<ResultType>(lhs + rhs);
-        return true;
-    }
-
-    static inline bool sub(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        if (!signsMatch(lhs, rhs)) {
-            if (lhs >= 0) {
-                if (lhs > std::numeric_limits<ResultType>::max() + rhs)
-                    return false;
-            } else {
-                if (rhs > std::numeric_limits<ResultType>::max() + lhs)
-                    return false;
-            }
-        } // if the signs match this operation can't overflow
-        result = static_cast<ResultType>(lhs - rhs);
-        return true;
-    }
-
-    static inline bool multiply(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        if (signsMatch(lhs, rhs)) {
-            if (lhs >= 0) {
-                if (lhs && (std::numeric_limits<ResultType>::max() / lhs) < rhs)
-                    return false;
-            } else {
-                if (static_cast<ResultType>(lhs) == std::numeric_limits<ResultType>::min() || static_cast<ResultType>(rhs) == std::numeric_limits<ResultType>::min())
-                    return false;
-                if ((std::numeric_limits<ResultType>::max() / -lhs) < -rhs)
-                    return false;
-            }
-        } else {
-            if (lhs < 0) {
-                if (rhs && lhs < (std::numeric_limits<ResultType>::min() / rhs))
-                    return false;
-            } else {
-                if (lhs && rhs < (std::numeric_limits<ResultType>::min() / lhs))
-                    return false;
-            }
-        }
-        result = static_cast<ResultType>(lhs * rhs);
-        return true;
-    }
-
-    static inline bool equals(LHS lhs, RHS rhs) { return lhs == rhs; }
-
-};
-
-template <typename LHS, typename RHS, typename ResultType> struct ArithmeticOperations<LHS, RHS, ResultType, false, false> {
-    // LHS and RHS are unsigned types so bounds checks are nice and easy
-    static inline bool add(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        ResultType temp = lhs + rhs;
-        if (temp < lhs)
-            return false;
-        result = temp;
-        return true;
-    }
-
-    static inline bool sub(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        ResultType temp = lhs - rhs;
-        if (temp > lhs)
-            return false;
-        result = temp;
-        return true;
-    }
-
-    static inline bool multiply(LHS lhs, RHS rhs, ResultType& result) WARN_UNUSED_RETURN
-    {
-        if (!lhs || !rhs) {
-            result = 0;
-            return true;
-        }
-        if (std::numeric_limits<ResultType>::max() / lhs < rhs)
-            return false;
-        result = lhs * rhs;
-        return true;
-    }
-
-    static inline bool equals(LHS lhs, RHS rhs) { return lhs == rhs; }
-
-};
-
-template <typename ResultType> struct ArithmeticOperations<int, unsigned, ResultType, true, false> {
-    static inline bool add(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        int64_t temp = lhs + rhs;
-        if (temp < std::numeric_limits<ResultType>::min())
-            return false;
-        if (temp > std::numeric_limits<ResultType>::max())
-            return false;
-        result = static_cast<ResultType>(temp);
-        return true;
-    }
-
-    static inline bool sub(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        int64_t temp = lhs - rhs;
-        if (temp < std::numeric_limits<ResultType>::min())
-            return false;
-        if (temp > std::numeric_limits<ResultType>::max())
-            return false;
-        result = static_cast<ResultType>(temp);
-        return true;
-    }
-
-    static inline bool multiply(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        int64_t temp = lhs * rhs;
-        if (temp < std::numeric_limits<ResultType>::min())
-            return false;
-        if (temp > std::numeric_limits<ResultType>::max())
-            return false;
-        result = static_cast<ResultType>(temp);
-        return true;
-    }
-
-    static inline bool equals(int lhs, unsigned rhs)
-    {
-        return static_cast<int64_t>(lhs) == static_cast<int64_t>(rhs);
-    }
-};
-
-template <typename ResultType> struct ArithmeticOperations<unsigned, int, ResultType, false, true> {
-    static inline bool add(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        return ArithmeticOperations<int, unsigned, ResultType>::add(rhs, lhs, result);
-    }
-
-    static inline bool sub(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        return ArithmeticOperations<int, unsigned, ResultType>::sub(lhs, rhs, result);
-    }
-
-    static inline bool multiply(int64_t lhs, int64_t rhs, ResultType& result)
-    {
-        return ArithmeticOperations<int, unsigned, ResultType>::multiply(rhs, lhs, result);
-    }
-
-    static inline bool equals(unsigned lhs, int rhs)
-    {
-        return ArithmeticOperations<int, unsigned, ResultType>::equals(rhs, lhs);
-    }
-};
-
-template <typename U, typename V, typename R> static inline bool safeAdd(U lhs, V rhs, R& result)
-{
-    return ArithmeticOperations<U, V, R>::add(lhs, rhs, result);
-}
-
-template <typename U, typename V, typename R> static inline bool safeSub(U lhs, V rhs, R& result)
-{
-    return ArithmeticOperations<U, V, R>::sub(lhs, rhs, result);
-}
-
-template <typename U, typename V, typename R> static inline bool safeMultiply(U lhs, V rhs, R& result)
-{
-    return ArithmeticOperations<U, V, R>::multiply(lhs, rhs, result);
-}
-
-template <typename U, typename V> static inline bool safeEquals(U lhs, V rhs)
-{
-    return ArithmeticOperations<U, V>::equals(lhs, rhs);
-}
-
-enum ResultOverflowedTag { ResultOverflowed };
-
-template <typename T, class OverflowHandler> class Checked : public OverflowHandler {
-public:
-    template <typename _T, class _OverflowHandler> friend class Checked;
-    Checked()
-        : m_value(0)
-    {
-    }
-
-    Checked(ResultOverflowedTag)
-        : m_value(0)
-    {
-        this->overflowed();
-    }
-
-    template <typename U> Checked(U value)
-    {
-        if (!isInBounds<T>(value))
-            this->overflowed();
-        m_value = static_cast<T>(value);
-    }
-
-    template <typename V> Checked(const Checked<T, V>& rhs)
-        : m_value(rhs.m_value)
-    {
-        if (rhs.hasOverflowed())
-            this->overflowed();
-    }
-
-    template <typename U> Checked(const Checked<U, OverflowHandler>& rhs)
-        : OverflowHandler(rhs)
-    {
-        if (!isInBounds<T>(rhs.m_value))
-            this->overflowed();
-        m_value = static_cast<T>(rhs.m_value);
-    }
-
-    template <typename U, typename V> Checked(const Checked<U, V>& rhs)
-    {
-        if (rhs.hasOverflowed())
-            this->overflowed();
-        if (!isInBounds<T>(rhs.m_value))
-            this->overflowed();
-        m_value = static_cast<T>(rhs.m_value);
-    }
-
-    const Checked& operator=(Checked rhs)
-    {
-        this->clearOverflow();
-        if (rhs.hasOverflowed())
-            this->overflowed();
-        m_value = static_cast<T>(rhs.m_value);
-        return *this;
-    }
-
-    template <typename U> const Checked& operator=(U value)
-    {
-        return *this = Checked(value);
-    }
-
-    template <typename U, typename V> const Checked& operator=(const Checked<U, V>& rhs)
-    {
-        return *this = Checked(rhs);
-    }
-
-    // prefix
-    const Checked& operator++()
-    {
-        if (m_value == std::numeric_limits<T>::max())
-            this->overflowed();
-        m_value++;
-        return *this;
-    }
-
-    const Checked& operator--()
-    {
-        if (m_value == std::numeric_limits<T>::min())
-            this->overflowed();
-        m_value--;
-        return *this;
-    }
-
-    // postfix operators
-    const Checked operator++(int)
-    {
-        if (m_value == std::numeric_limits<T>::max())
-            this->overflowed();
-        return Checked(m_value++);
-    }
-
-    const Checked operator--(int)
-    {
-        if (m_value == std::numeric_limits<T>::min())
-            this->overflowed();
-        return Checked(m_value--);
-    }
-
-    // Boolean operators
-    bool operator!() const
-    {
-        if (this->hasOverflowed())
-            CRASH();
-        return !m_value;
-    }
-
-    typedef void* (Checked::*UnspecifiedBoolType);
-    operator UnspecifiedBoolType*() const
-    {
-        if (this->hasOverflowed())
-            CRASH();
-        return (m_value) ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0;
-    }
-
-    // Value accessors. unsafeGet() will crash if there's been an overflow.
-    T unsafeGet() const
-    {
-        if (this->hasOverflowed())
-            CRASH();
-        return m_value;
-    }
-
-    inline CheckedState safeGet(T& value) const WARN_UNUSED_RETURN
-    {
-        value = m_value;
-        if (this->hasOverflowed())
-            return CheckedState::DidOverflow;
-        return CheckedState::DidNotOverflow;
-    }
-
-    // Mutating assignment
-    template <typename U> const Checked operator+=(U rhs)
-    {
-        if (!safeAdd(m_value, rhs, m_value))
-            this->overflowed();
-        return *this;
-    }
-
-    template <typename U> const Checked operator-=(U rhs)
-    {
-        if (!safeSub(m_value, rhs, m_value))
-            this->overflowed();
-        return *this;
-    }
-
-    template <typename U> const Checked operator*=(U rhs)
-    {
-        if (!safeMultiply(m_value, rhs, m_value))
-            this->overflowed();
-        return *this;
-    }
-
-    const Checked operator*=(double rhs)
-    {
-        double result = rhs * m_value;
-        // Handle +/- infinity and NaN
-        if (!(std::numeric_limits<T>::min() <= result && std::numeric_limits<T>::max() >= result))
-            this->overflowed();
-        m_value = (T)result;
-        return *this;
-    }
-
-    const Checked operator*=(float rhs)
-    {
-        return *this *= (double)rhs;
-    }
-
-    template <typename U, typename V> const Checked operator+=(Checked<U, V> rhs)
-    {
-        if (rhs.hasOverflowed())
-            this->overflowed();
-        return *this += rhs.m_value;
-    }
-
-    template <typename U, typename V> const Checked operator-=(Checked<U, V> rhs)
-    {
-        if (rhs.hasOverflowed())
-            this->overflowed();
-        return *this -= rhs.m_value;
-    }
-
-    template <typename U, typename V> const Checked operator*=(Checked<U, V> rhs)
-    {
-        if (rhs.hasOverflowed())
-            this->overflowed();
-        return *this *= rhs.m_value;
-    }
-
-    // Equality comparisons
-    template <typename V> bool operator==(Checked<T, V> rhs)
-    {
-        return unsafeGet() == rhs.unsafeGet();
-    }
-
-    template <typename U> bool operator==(U rhs)
-    {
-        if (this->hasOverflowed())
-            this->overflowed();
-        return safeEquals(m_value, rhs);
-    }
-
-    template <typename U, typename V> const Checked operator==(Checked<U, V> rhs)
-    {
-        return unsafeGet() == Checked(rhs.unsafeGet());
-    }
-
-    template <typename U> bool operator!=(U rhs)
-    {
-        return !(*this == rhs);
-    }
-
-private:
-    // Disallow implicit conversion of floating point to integer types
-    Checked(float);
-    Checked(double);
-    void operator=(float);
-    void operator=(double);
-    void operator+=(float);
-    void operator+=(double);
-    void operator-=(float);
-    void operator-=(double);
-    T m_value;
-};
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
-{
-    U x = 0;
-    V y = 0;
-    bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
-    typename Result<U, V>::ResultType result = 0;
-    overflowed |= !safeAdd(x, y, result);
-    if (overflowed)
-        return ResultOverflowed;
-    return result;
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
-{
-    U x = 0;
-    V y = 0;
-    bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
-    typename Result<U, V>::ResultType result = 0;
-    overflowed |= !safeSub(x, y, result);
-    if (overflowed)
-        return ResultOverflowed;
-    return result;
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(Checked<U, OverflowHandler> lhs, Checked<V, OverflowHandler> rhs)
-{
-    U x = 0;
-    V y = 0;
-    bool overflowed = lhs.safeGet(x) == CheckedState::DidOverflow || rhs.safeGet(y) == CheckedState::DidOverflow;
-    typename Result<U, V>::ResultType result = 0;
-    overflowed |= !safeMultiply(x, y, result);
-    if (overflowed)
-        return ResultOverflowed;
-    return result;
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(Checked<U, OverflowHandler> lhs, V rhs)
-{
-    return lhs + Checked<V, OverflowHandler>(rhs);
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(Checked<U, OverflowHandler> lhs, V rhs)
-{
-    return lhs - Checked<V, OverflowHandler>(rhs);
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(Checked<U, OverflowHandler> lhs, V rhs)
-{
-    return lhs * Checked<V, OverflowHandler>(rhs);
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator+(U lhs, Checked<V, OverflowHandler> rhs)
-{
-    return Checked<U, OverflowHandler>(lhs) + rhs;
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator-(U lhs, Checked<V, OverflowHandler> rhs)
-{
-    return Checked<U, OverflowHandler>(lhs) - rhs;
-}
-
-template <typename U, typename V, typename OverflowHandler> static inline Checked<typename Result<U, V>::ResultType, OverflowHandler> operator*(U lhs, Checked<V, OverflowHandler> rhs)
-{
-    return Checked<U, OverflowHandler>(lhs) * rhs;
-}
-
-} // namespace WTF
-
-using WTF::Checked;
-using WTF::CheckedState;
-using WTF::RecordOverflow;
-
-#endif