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Noncompliant Code Example (Improper &)

Wiki MarkupThis noncompliant code example, derived from Flanagan \[ [Flanagan 2005|AA. References#Flanagan 05]\], has two variables, with no guarantees regarding their current values. The code must validate its data and then check whether {{array\[i\]}} is nonnegative.

int array[]; // may be null
int i;       // may be a valid index for array
if (array != null &
    i >= 0 & i < array.length &
    array[i] >= 0) {
  // handle array
} else {
  // handle error
}

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This code can fail as a result of the same errors it is attempting to prevent. When {{array}} is {{NULL}} or when {{i}} is not a valid index, the reference to {{array\[i\]}} will cause a {{NullPointerException}} or an {{ArrayIndexOutOfBoundsException}} to be thrown. This happens because the {{&}} operator fails to prevent evaluation of its right operand even when evaluation of its left operand proves that the right operand is invalid.

Compliant Solution (Use &&)

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CERT C Secure Coding Standard: EXP02-C. Be aware of the short-circuit behavior of the logical AND and OR operators
CERT C++ Secure Coding Standard: EXP02-CPP. Be aware of the short-circuit behavior of the logical AND and OR operators

Bibliography

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