I'm working on a project where we are appling MISRA 2004.
On most of the violations I got the reason, but one I don't understand:
Its in the if-statement with && and || operations.
Example:
uint8 getValue()
{
// Some algorithm, simplified with return 1
uint8 someValue = 1u;
return someValue;
}
int main(int argc, char *argv[]) {
uint8 currentState = 0u;
uint8 var_a = getValue();
uint8 var_b = getValue();
uint8 var_c = getValue();
uint8 var_d = getValue();
const uint8 const_a = 1u;
const uint8 const_b = 2u;
const uint8 const_c1 = 3u;
const uint8 const_c2 = 30u;
const uint8 const_d = 4u;
if ((var_a == const_a) && (var_b == const_b) && ((var_c == const_c1) || (var_c == const_c2)) && (var_d == const_d))
{
currentState = 1;
} else
{
currentState = 2;
}
}
This gives me twice the MISRA violation to rule 12.5 non-primary expression used with logical operator. Both are in the line with the IF-Statement
I don't see a problem with this if-statement, despite its a bit long.
Does anybody know, whats wrong here and how to solve that violation?
Edit: I adjusted the example a bit. I also noticed, that I get only one error if I simplify the if statement to:
if ((var_a == const_a) && ((var_c == const_c1) || (var_c == const_c2)) && (var_d == const_d))
And no violation if its changed to:
if ((var_a == const_a) && ((var_c == const_c1) || (var_c == const_c2)))
This appears to be a false positive by your static analyser. Your code is compliant.
The rationale for MISRA C:2004 12.5 (and the equivalent rules in the 2012 version) is to avoid situations where operator precedence might not be obvious. Overall MISRA insists that sub-expressions involving binary operators ("complex expressions") should always have parenthesis.
In case of the boolean && and || operators specifically, the rule 12.5 allows chaining multiple of them in the same expression, but not mixing && and || in the same expression without parenthesis, since they have different precedence.
Had you written && (var_c == const_c1) || (var_c == const_c2) && then the code would be non-conforming. You didn't however, and you did also put parenthesis around the inner sub-expressions.