Page History

...

Non-Compliant Code Example 1

This

 non-compliant code example demonstrates how dead code can be introduced into a program \[[Fortify 06|AA. C References#Fortify 06]\]. The second conditional statement, {{if (s)}} will never evaluate true because it requires that {{s}} not be assigned {{NULL}}, and the only path where {{s}} can be assigned a non\-{{NULL}} value ends with a return statement.

int func(int condition) {
    char *s = NULL;
    if (condition) {
        s = malloc(10);
        if (s == NULL) {
           /* Handle Error */
        }
        /* Process s */
        return 0;
    }
    /* ... */
    if (s) {
        /* This code is never reached */
    }
    return 0;
}

Compliant Solution 1

Remediating Remediation of dead code requires the programmer to determine why the code is never executed and then resolve that situation appropriately. To correct the example above, the return is removed from the body of the first conditional statement.

...

int string_loop(char *str) {
    size_t i;
    for (i=0; i < strlen(str); i++) {
        /* ... */
	if (str[i+1] == '\0')
	    /* This code is now reached */
    }
    return 0;
}

Exceptions

MSC00-EX1 In some situations, dead code may make software more robust against future changes. An example of this is adding a default case to a switch statement even when all possible switch labels are specified (see MSC01-A. Strive for logical completeness for an illustration of this example).

Risk Assessment

The presence of dead code may indicate logic errors that can lead to unintended program behavior. The ways in which dead code can be introduced in to a program and the effort required to remove it can be complex. Given this, resolving dead code can be an in-depth process requiring significant changes.

...