Ineffective comparison of unsigned value in a macro is always false

The CWARN.NOEFFECT.UCMP.LT.MACRO checker flags code in macros, in which there is a comparison of an unsigned value to zero that is always false.

Vulnerability and risk

If 'a' is an unsigned value, the comparisons a < 0 and 0 > a are always false. These comparisons have no effect, so it's probable that design intent isn't being accomplished.

Vulnerable code example

  #define RETURN_NEGATIVE(x) if (x < 0) return x
  int foo(usigned int a) {
    return 0;

Klocwork flags line 4, in which the macro RETURN_NEGATIVE contains a condition that is always false.