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Code within a program that is never executed is known as dead code. The presence of dead code often indicates that a logic error has occurred. Typically, this error is an a result of changes to the program or the environment. Dead code is often identified and optimized out dead code during compilation. However, it should be identified, understood, and removed from a program's source code to improve readability and ensure that logic errors are resolved.

Non-Compliant Code Example

This example, inspired by Fortify demonstrates how dead code can be introduced into a program. Because s is set to NULL everything inside if (s) will never be executed. It requires that condition

from fortifysoftware:

ABSTRACT

This statement will never be executed.
EXPLANATION

The surrounding code makes it impossible for this statement to ever be executed.

Example: The condition for the second if statement is impossible to satisfy. It requires that the variable s be non-null, while on the only path where s can be assigned a non-null value there is a return statement.

String s = null;

if (b) {
s = "Yes";
return;
}

int func(int condition) {
    int *s = NULL;
    if (condition) {
        s = malloc(10);
        if (s == NULL) {
           /* Handle Error */ 
        }
        /* insert data into s */
        return;
    }
    /* ... */
    if (s) {
        /* This statement is never reached */
    }
}

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