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Warning C26453

  • Article

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 nonportable 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 = ~0u << shiftCount; // OK

  // code
}

See also

26450
26451
26452
26454
ES.101: Use unsigned types for bit manipulation
ES.102: Use signed types for arithmetic