# V6031. The variable 'X' is being used for this loop and for the outer loop.

The analyzer detected a potential error: a nested loop utilizes a variable as its counter, which is also used in an outer loop.

In a schematic form, this error looks in the following way:

    int i = 0, j = 0;
    for (i = 0; i < 5; i++)
      for (i = 0; i < 5; i++)
        arr[i][j] = 0;

Of course, this is an artificial sample, so we may easily see the error, but in a real application, the error might be not so apparent. This is the correct code:

    int i = 0, j = 0;
    for (i = 0; i < 5; i++)
      for (j = 0; j < 5; j++)
        arr[i][j] = 0;

Using one variable both for the outer and inner loops is not always a mistake. Consider a sample of correct code the analyzer won't generate the warning for:

    for (c = lb; c <= ub; c++)
    {
      if (!(xlb <= calc(c) && calc(c) <= ub))
      {
        Range r = new Range(xlb, xlb + 1);
        for (c = lb + 1; c <= ub; c++)
          r = DoUnion(r, new Range(calc(c), calc(c) + 1));
        return r;
      }
    }

In this code, the inner loop "for (c = lb + 1; c <= ub; c++)" utilizes the "c" variable as a counter. The outer loop also uses the "c" variable. But there is no error here. After the inner loop is executed, the "return r;" operator will perform exit from the function.

This diagnostic is classified as:

CWE-691 CERT-MSC57-J