MISRA C++:2008 Rule 5-2-1

Each operand of a logical && or || shall be a postfix-expression

Description

Rule Definition

Each operand of a logical && or || shall be a postfix-expression.

Rationale

This rule effectively requires that operands of a logical && or || operation be appropriately parenthesized. For instance, instead of a + b || c, the rule requires (a + b) || c or a + (b || c). In both compliant cases, the left operand of ||, that is (a + b) or b, is a primary expression and therefore also a postfix expression. For more information on postfix expressions, see the C++03 Standard (Section 5.2).

Enclosing operands in parentheses improves readability of code and makes sure that the operations occur in the order that the developer intends.

Polyspace Implementation

The checker raises a violation if a logical && or || operand is not a postfix expression.

A postfix expression can be a primary expression such as a simple identifier or a combination of identifiers enclosed in parentheses, but also one of the following:

• Function call such as func().

• Array element access such as arr[].

• Structure member access such as aStructVar.aMember.

For the complete list of postfix expressions, see the C++03 Standard (Section 5.2).

The checker allows exceptions on associative chains such as (a && b && c) or (a || b || c).

Troubleshooting

If you expect a rule violation but do not see it, refer to Coding Standard Violations Not Displayed.

Examples

Noncompliant and Compliant Expressions Involving Logical Operations

bool Operations(bool a, bool b, bool c, bool priority) {
    bool res;
    if(priority) {
        res = a && b || c;  //Noncompliant
    }
    else {
        res = a && (b || c); //Compliant
    }
    return res;
}

In this example, the expression a && b || c violates the rule because the right operand of && and the left operand of || are not postfix expressions.

Check Information

Group: Expressions

Category: Required