V776. Potentially infinite loop. The variable in 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 Do(int x);
....
int n = Foo();
int x = 0;
while (x < n)
{
  Do(x);
}

The loop's exit condition depends on variable x whose value will always be zero, so the x < n check (if n > 0) will always evaluate to true, causing an infinite loop.

A correct version of this code:

int Do(int x);
....
int n = Foo();
int x = 0;
while (x < n)
{
  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 rule is classified as: