False negative: always-true logic hidden behind boolean temporaries

[Rodri]

Hi, I found a false negative regarding the rule incorrectLogicOperator.

Cppcheck reports incorrectLogicOperator for the direct condition x >= 0 || x <= 10, because the disjunction is always true. However, if the two comparisons are stored in boolean temporaries first, cppcheck reports no warning even though the condition is semantically equivalent.

Original seed program

static void foo(int x) {
    if (x >= 0 || x <= 10) {}
}

Reproducing program

#include <stdbool.h>

static void foo(int x) {
  bool b1 = x >= 0;
  bool b2 = x <= 10;
  if (b1 || b2) {
  }
}

The condition b1 || b2 is equivalent to x >= 0 || x <= 10, which is always true for any integer x.

Actual result

Cppcheck reports no incorrectLogicOperator warning for the reproducing program.

Expected result

Cppcheck should report incorrectLogicOperator for the condition b1 || b2.

Verification

The issue was reproduced with:

cppcheck --output-format=xmlv2 --enable=all incorrect_logic_operator_bool_temps.c

Version: 2.21.0

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/14943