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Warning C26453

Describes the causes of MSVC code analysis warning C26453, and shows how to fix it.

05/11/2023

C26453

LEFTSHIFT_NEGATIVE_SIGNED_NUMBER

C26453

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 nonportable and triggers implementation defined behavior.

Code analysis name: LEFTSHIFT_NEGATIVE_SIGNED_NUMBER

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
}