CERT C: Rec. EXP13-C

Possibly unintended evaluation of expression because of operator precedence rules occurs when an arithmetic expression result is possibly unintended because operator precedence rules dictate an evaluation order that you do not expect.

The defect highlights expressions of the form x op_1 y op_2 z. Here, op_1 and op_2 are operator combinations that commonly induce this error. For instance, x == y | z.

The checker does not flag all operator combinations. For instance, x == y || z is not flagged because you most likely intended to perform a logical OR between x == y and z. Specifically, the checker flags these combinations:

The defect can cause the following issues:

See if the order of evaluation is what you intend. If not, apply parentheses to implement the evaluation order that you want.

For better readability of your code, it is good practice to apply parenthesis to implement an evaluation order even when operator precedence rules impose that order.

int test(int a, int b, int c) {
    return(a & b == c); //Noncompliant
}

In this example, the == operation happens first, followed by the & operation. If you intended the reverse order of operations, the result is not what you expect.

One possible correction is to apply parenthesis to implement the intended evaluation order.

int test(int a, int b, int c) {
    return((a & b) == c);
}