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Scope minimization helps developers to avoid common programming errors, improves code readability by connecting the declaration and actual use of a variable, and improves maintainability because unused variables are more easily detected and removed.

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This noncompliant code example shows a variable that is declared outside the for loop. This reduces reusability Reusability is reduced because the value of the loop index, i, is modified by the for statement. ConsiderSuppose, for example, the case when this code snippet is copied and pasted with the intent to use a different index, j. If the index variable change were omitted, the new loop would then attempt to iterate over index i. Unexpected behavior can follow because i remains in scope.

public class Scope {
  public static void main(String[] args) {
    int i = 0;
    for (i = 0; i < 10; i++) {
      // Do operations
    }
  }
}

It should be noted that this This code is noncompliant because i is not used outside the for loop. The variable i would need to be declared local to the method if, for example, the loop contained a break statement and the value of i was inspected outside the loop.

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This noncompliant code example shows a variable count that is declared outside the counter method, although the variable is not used outside the counter method. This reduces the reusability of the method because the count variable would need to be redefined in the new context.

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Detecting local variables that are declared in a larger scope than is required by the code as - written code is straightforward and can avoid any eliminate the possibility of false positives.

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C Secure Coding Standard: "DCL19-C. Minimize the scope of variables and functions"
C++ Secure Coding Standard: "DCL07-CPP. Minimize the scope of variables and methods"

Bibliography

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