S2197 — Modulus results should not be checked for direct equality

Why is this an issue?

When the modulus of a negative number is calculated, the result will either be negative or zero. Thus, comparing the modulus of a variable for equality with a positive number (or a negative one) could result in unexpected results.

Noncompliant code example

public bool IsOdd(int x)
{
  return x % 2 == 1;  // Noncompliant; if x is an odd negative, x % 2 == -1
}

Compliant solution

public bool IsOdd(int x)
{
  return x % 2 != 0;
}

or

public bool IsOdd(uint x)
{
  return x % 2 == 1;
}