Warning C26453

Arithmetic overflow: Left shift of a negative signed number is undefined behavior (io.4)

Remarks

This warning indicates the code left shifts a negative signed integral value, which is non-portable and triggers implementation defined behavior.

Code analysis name: LEFTSHIFT_NEGATIVE_SIGNED_NUMBER

Example

void leftshift(int shiftCount)
{
  const auto result = -1 << shiftCount;  // C26453 reported here

  // code
}

To correct this warning, use the following code:

void leftshift(int shiftCount)
{
  const auto result = static_cast<unsigned>(-1) << shiftCount; // OK

  // code
}

See also

ES.102: Use signed types for arithmetic