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The presence of unused values in code may indicate significant logic errors. To prevent such errors, unused values should be identified and removed from code.

Noncompliant Code Example (

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Dead Code)

This noncompliant code example demonstrates how dead code can be introduced into a program [Fortify 06]. 

public int func(boolean condition) {
    int x = 0;
    if (condition) {
        x = foo();
        /* Process x */
        return x;
    }
    /* ... */
    if (x != 0) {
        /* This code is never executed */
    }
    return x;
}

The condition in the second conditional if statement, if (x != 0), will never evaluate to true because the only path where x can be assigned a non-zero value ends with a return statement.

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int func(int condition) {
    int x = 0;
    if (condition) {
        x = foo();
        /* Process x */
    }
    /* ... */
    if (x != 0) {
        /* This code is now executed */
    }
    return 0;
}

Noncompliant Code Example (

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Dead Code)

In this example, the length() function is used to limit the number of times the function string_loop() will iterate. The conditional condition of the if statement inside the loop evaluates to true when the current index is the length of str. However, because str.length() is not i is always strictly less than str.length(), that will never happen.

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public int string_loop(String str) {
  for (int i=0; i < str.length(); i++) {
    /* ... */
    if (i==str.length()-1) {
      /* This code is now executed */
    }
  }
  return 0;
}

Noncompliant Code Example (

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Code with no

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Effect)

In this noncompliant code example, the comparison of s to t has no effect.

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String s;
String t;

// ...

if (s.equals(t)) {
  System.out.println("Strings equal");
} else {
  System.out.println("Strings unequal");
}

Noncompliant Code Example (

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Unused Values)

In this example, p2 is assigned the value returned by bar(), but that value is never used.

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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 into a program and the effort required to remove it can be complex. As a result, resolving dead code can be an in-depth process requiring significant analysis.

In some exceptional situations, dead code may make software resilient to future changes. An example of this is the presence of a default case in a switch statement even though all possible switch labels are specified (see MSC60-JG. Strive for logical completeness for an illustration of this example).

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The presence of code that has no effect can indicate logic errors that may result in unexpected behavior and vulnerabilities.

Unused values in code may indicate significant logic errors.

Code and values that has have no effect can be detected by suitable static analysis.Unused values in code may indicate significant logic errors.

Related Guidelines

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