MISRA.LOGIC.OPERATOR.NOT_BOOL

Operand of non-logical operator is effectively boolean.

MISRA-C Rule 12.6 (advisory): The operands of logical operators (&&, || and !) should be effectively Boolean. Expressions that are effectively Boolean should not be used as operands to operators other than (&&, ||, !, =, ==, != and ?:).

This rule is also covered by MISRA.LOGIC.OPERAND.NOT BOOL.

[Koenig 48]

The logical operators &&, || and ! can be easily confused with the bitwise operators &, | and ~. See "Boolean Expressions" in the glossary.

MISRA-C++ Rule 4-5-1 (required): Expressions with type bool shall not be used as operands to built-in operators other than the assignment operator =, the logical operators &&, ||, !, the equality operators == and !=, the unary & operator, and the conditional operator.

Rationale

The use of bool operands with other operators is unlikely to be meaningful (or intended). This rule allows the detection of such uses, which often occur because the logical operators (&&, || and !) can be easily confused with the bitwise operators (&, | and ~).

Example

bool b1 = true;
bool b2 = false;
int8_t s8a;

if ( b1 & b2 )      // Non-compliant
if ( b1 < b2 )      // Non-compliant
if ( ~b1 )          // Non-compliant
if ( b1 ^ b2 )      // Non-compliant
if ( b1 == false )  // Compliant
if ( b1 == b2 )     // Compliant
if ( b1 != b2 )     // Compliant
if ( b1 && b2 )     // Compliant
if ( !b1 )          // Compliant
s8a = b1 ? 3 : 7;   // Compliant