Rule Definition
Having the same name refer to two different objects can lead to confusion. In case of refactoring, when the code is moved around, a line of code can pick-up a different variable from the one intended. Hiding is also an indication that names may have been poorly chosen, and not informative enough. Hiding with global names is not checked, because a modification in one part of the code could lead to a violation in another unrelated part.

Remediation
To correct that problem, choose different variable names.

Violation Code Sample

int i;

int main()
{
    int i = 3; // Not a violation
    int j = 2;
    for (int j = 0 ; j<10 ; ++j) // Violation
    {
    }
}

High Integrity C++ Coding Standard Manual