CERT C: Rule EXP46-C

Use of bitwise operator with a Boolean-like operand occurs when you use bitwise operators, such as:

with:

Using Boolean type variables as array indices, in Boolean arithmetic expression, and in shifting operations does not raise this defect.

Boolean-like operands, such as variables of type bool and outputs of relational operators typically appear in logical expressions. Using a bitwise operator in an expression containing Boolean variables and relational operators might be a sign of logic error. Because bitwise operators and logical operators look similar, you might inadvertently use a bitwise operator instead of a logical operator. Such logic errors do not raise any compilation error and can introduce bugs in your code that are difficult to find.

Use logical operators in expressions that contain Boolean variables and relational operator. To indicate that you intend to use a bitwise operator in such an expression, use parentheses.

int getuid();
int geteuid();
void func ()
{
	if (getuid () & geteuid () == 0) {//Noncompliant   
		/* ... */
	}else{
		/*...*/
	}
}

In this example, the if-else block is executed conditionally. The conditional statement uses the bitwise AND (&) instead of the logical AND (&&), perhaps by mistake. Consider when the function geteuid() evaluates to 0, and getuid() evaluates to 2. In this case, the else block of code executes if you use & because 2&1 evaluates to false. Conversely, the if block of code executes when you use && because 2&&1 evaluates to true. Using & instead of && might introduce logic errors and bugs in your code that are difficult to find. Polyspace^® flags the use of bitwise operators in these kinds of expressions where relational operators are also used.

One possible correction is to use logical operators in expressions that contain relational operators and Boolean variables.

int getuid();
int geteuid();
void func ()
{
	if (getuid () && geteuid () == 0) { //Compliant   
		/* ... */
	}else{
		/*...*/
	}
}

Another possible correction, if your intent is to use the & operator, is to enclose the operands in parentheses to preserve the order of operations and the intended logic.

int getuid();
int geteuid();
void func ()
{
	if ((getuid ()) & (geteuid () == 0)) { //Compliant  
		/* ... */
	}else{
		/*...*/
	}
}