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Change shift operators to throw on undefined behavior instead of assert [UPDATED] #66

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Change shift operators to throw on undefined behavior instead of assert [UPDATED] #66

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a383760
Change shift operators to throw on undefined behavior instead of just…
dcleblanc Aug 7, 2024
be059f0
Build fixes
dcleblanc Aug 9, 2024
988c357
More fixes.
rsmmr Dec 3, 2024
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Change shift operators to throw on undefined behavior instead of just… 
… assert.
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@dcleblanc @rsmmr
dcleblanc authored and rsmmr committed Dec 3, 2024
commit a38376018b6254383cd631a01ba2b5d9afe3bafb
89 changes: 58 additions & 31 deletions SafeInt.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5374,6 +5374,20 @@ template < typename T, typename U > class BinaryXorHelper< T, U, BinaryState_Int
}
};

template < typename T, typename U >
SAFE_INT_NODISCARD _CONSTEXPR14 bool valid_bitcount(U bits)
{
if (!std::numeric_limits< U >::is_signed || bits >= 0)
{
if (bits < (int)safeint_internal::int_traits< T >::bitCount)
{
return true;
}
}

return false;
}

/***************** External functions ****************************************/

// External functions that can be used where you only need to check one operation
Expand Down Expand Up @@ -5988,87 +6002,100 @@ template < typename T, typename E = SafeIntDefaultExceptionHandler > class SafeI
// code path is exactly the same as for SafeInt< U, E > as rhs

// Left shift
// Also, shifting > bitcount is undefined - trap in debug
#define ShiftAssert(x) SAFEINT_ASSERT(x)

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E > operator <<( U bits ) const SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || bits >= 0 );
ShiftAssert( bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
return SafeInt< T, E >((T)(m_int << bits));
}

return SafeInt< T, E >( (T)( m_int << bits ) );
E::SafeIntOnOverflow();
}

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E > operator <<( SafeInt< U, E > bits ) const SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || (U)bits >= 0 );
ShiftAssert( (U)bits < (int)safeint_internal::int_traits< T >::bitCount );

return SafeInt< T, E >( (T)( m_int << (U)bits ) );
if (valid_bitcount<T, U>(bits))
{
return SafeInt< T, E >((T)(m_int << (U)bits));
}
E::SafeIntOnOverflow();
}

// Left shift assignment

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E >& operator <<=( U bits ) SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || bits >= 0 );
ShiftAssert( bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
m_int <<= bits;
return *this;
}

m_int <<= bits;
return *this;
E::SafeIntOnOverflow();
}

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E >& operator <<=( SafeInt< U, E > bits ) SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || (U)bits >= 0 );
ShiftAssert( (U)bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
m_int <<= (U)bits;
return *this;
}

m_int <<= (U)bits;
return *this;
E::SafeIntOnOverflow();
}

// Right shift
template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E > operator >>( U bits ) const SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || bits >= 0 );
ShiftAssert( bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
return SafeInt< T, E >((T)(m_int >> bits));
}

return SafeInt< T, E >( (T)( m_int >> bits ) );
E::SafeIntOnOverflow();
}

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E > operator >>( SafeInt< U, E > bits ) const SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || (U)bits >= 0 );
ShiftAssert( (U)bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
return SafeInt< T, E >((T)(m_int >> (U)bits));
}

return SafeInt< T, E >( (T)(m_int >> (U)bits) );
E::SafeIntOnOverflow();
}

// Right shift assignment
template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E >& operator >>=( U bits ) SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || bits >= 0 );
ShiftAssert( bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
m_int >>= bits;
return *this;
}

m_int >>= bits;
return *this;
E::SafeIntOnOverflow();
}

template < typename U >
SAFEINT_CONSTEXPR14 SafeInt< T, E >& operator >>=( SafeInt< U, E > bits ) SAFEINT_NOTHROW
{
ShiftAssert( !std::numeric_limits< U >::is_signed || (U)bits >= 0 );
ShiftAssert( (U)bits < (int)safeint_internal::int_traits< T >::bitCount );
if (valid_bitcount<T, U>(bits))
{
m_int >>= (U)bits;
return *this;
}

m_int >>= (U)bits;
return *this;
E::SafeIntOnOverflow();
}

// Bitwise operators
Expand Down
2 changes: 1 addition & 1 deletion helpfile.md
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Original file line number Diff line number Diff line change
Expand Up @@ -324,7 +324,7 @@ The shift operators have the following signatures:
SafeInt< U, E > operator >>( U lhs, SafeInt< T, E > bits )

Note:
Shift operations where the right argument is larger than the number of bits in the left argument type minus 1 is implementation-defined behavior. SafeInt will attempt to help you avoid this by causing an assert in debug builds. If you prefer to have a stronger reaction, create a custom SAFEINT_ASSERT that throws or causes a fault in both debug and release builds. Shifting by a negative bit count also doesn't make sense, and is also trapped.
Shift operations where the right argument is larger than the number of bits in the left argument type minus 1 is implementation-defined behavior. Undefined behavior, such as shifting by a negative count or more bits than the type has will throw an exception.

### Methods
SafeInt has a a small number of methods that help with common problems, such as aligning a value, getting a pointer to the raw integer type, and helping to manage pointer arithmetic.
Expand Down