# V3120. Potentially infinite loop. The variable from the loop exit condition does not change its value between iterations.

The analyzer detected a potentially infinite loop with its exit condition depending on a variable whose value never changes between iterations.

Consider the following example:

    int x = 0;
    while (x < 10)
    {
      Do(x);
    }

The loop's exit condition depends on variable 'x' whose value will always be zero, so the 'x < 10' check will always evaluate to "true", causing an infinite loop. A correct version of this code could look like this:

    int x = 0;
    while (x < 10)
    {
      x = Do(x);
    }

Here is another example where the loop exit condition depends on a variable whose value, in its turn, changes depending on other variables that never change inside the loop. Suppose we have the following method:

    int Foo(int a)
    {
      int j = 0;
      while (true)
      {
        if (a >= 32)
        {
          return j * a;
        }

        if (j == 10)
        {
          j = 0;
        }
        j++;
      }
    }

The loop's exit condition depends on the 'a' parameter. If 'a' does not pass the 'a >= 32' check, the loop will become infinite, as the value of 'a' does not change between iterations. This is one of the ways to fix this code:

    int Foo(int a)
    {
      int j = 0;
      while (true)
      {
        if (a >= 32)
        {
          return j * a;
        }

        if (j == 10)
        {
          j = 0;
          a++; // <=
        }
        j++;
      }
    }

In the fixed version, the local variable 'j' controls how the 'a' parameter's value changes.

This diagnostic is classified as:

CWE-835