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:

Was this page helpful?

Message submitted.

Your message has been sent. We will email you at

If you do not see the email in your inbox, please check if it is filtered to one of the following folders:

• Promotion
• Updates
• Spam

If you can’t find an answer to your question, fill in the form below and our developers will contact you

By clicking this button you agree to our Privacy Policy statement