# V115. Memsize type is used for throw.

The analyzer found a possible error related to the use of memsize type for throwing an exception. The error may consist in the incorrect exception handling.

Let's examine an example of the code which contains 'throw' and 'catch' operators.

    char *ptr1, *ptr2;
    ...
    try {
      throw ptr2 - ptr1;
    }
    catch(int) {
      Foo();
    }

On 64-bit system the exception handler will not work and the function 'Foo()' will not be called. This results from the fact that expression "ptr2 - ptr1" has type 'ptrdiff_t' which on 64-bit system does not equivalent with type 'int'.

The correction of the situation described consists in use of correct type for catch of exception. In this case is necessary use of 'ptrdiff_t' type, as noted below.

    try {
      throw ptr2 - ptr1;
    }
    catch(ptrdiff_t) {
      Foo();
    }

More right correction will consist in refusal of similar practice of programming. We recommend to use special classes for sending information about the error.

Additional materials on this topic:

- 64-bit Lessons. Lesson 20. Pattern 12. Exceptions.