# V1108. Constraint specified in a custom function annotation on the parameter is violated.

The analyzer has detected a violation of user-specified constraints on a function parameter.

A user annotation mechanism in the JSON format enables you to provide the analyzer with more information about types and functions. Moreover, it enables you to set constraints on the parameters of the annotated function.

For example, if you want the analyzer to notify you when a negative value or zero is passed to a function, your annotation may look like this:

    {
      "version": 1,
      "annotations": [
        {
          "type": "function",
          "name": "my_constrained_function",
          "params": [
            {
              "type": "int",
              "constraint": {
                "disallowed": [ "..0" ]
              }
            }
          ]
        }
      ]
    }

When you load a file with such an annotation, the V1108 warning is issued for the following code:

    void my_constrained_function(int);

    void caller(int i)
    {
      if (i < 0)
      {
        return;
      }

      my_constrained_function(i); // <=
    }

In this case, a developer made a mistake by mixing up the '<' and '<=' operators. However, due to the constraints in the annotation, the analyzer knows that no negative values or zero should be passed to the 'my_constrained_function' function.

Here is the fixed code:

    void my_constrained_function(int);

    void caller(int i)
    {
      if (i <= 0)
      {
        return;
      }

      my_constrained_function(i);
    }