Testing `for` loop termination using an equality operator (`==` and `!=`) is dangerous, because it could set up an infinite loop. Using a relational operator instead casts a wider net, and makes it harder (but not impossible) to accidentally write an infinite loop.

## Noncompliant Code Example

    for (var i = 1; i != 10; i += 2)  // Noncompliant. Infinite; i goes from 9 straight to 11.
    {
      //...
    }

## Compliant Solution

    for (var i = 1; i <= 10; i += 2)  // Compliant
    {
      //...
    }

## Exceptions

An equality operator may be used if the loop counter is not modified within the body of the loop and either:

- starts below the ending value and is incremented by 1 on each iteration.
- starts above the ending value and is decremented by 1 on each iteration.

Equality operators are also ignored when the test is against `null`.

    for (int i = 0; arr[i] != null; i++) {
      // ...
    }

    for (int i = 0; (item = arr[i]) != null; i++) {
      // ...
    }

## See

- MISRA C++:2008, 6-5-2
- MITRE, CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')
- CERT, MSC21-C - Use robust loop termination conditions
- CERT, MSC21-CPP - Use inequality to terminate a loop whose counter changes by more than one