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C26453

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

07/15/2020

reference

C26453

C++

Warning C26453

Arithmetic overflow: Left shift of a negative signed number is undefined behavior

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

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
}