How to fix a "Stack Overflow" error in recursive procedures in Modula-2?

First, identify the recursive procedure that's causing the "Stack Overflow" error. The error message or debugging tools should give you a clue. Look at the call stack at the time the error occurs to see which procedures are being called.

Understand what the recursive procedure is supposed to do. You need to know what condition it's testing to stop the recursion and how it changes its arguments or local variables each time it calls itself.

The cause of a "Stack Overflow" error in a recursive procedure is often that the recursion goes too deep because the exit condition is never met. Understand the exit condition and investigate whether it can ever be met.

For example, maybe the arguments to the procedure or the local variables in the procedure are supposed to change each time the procedure is called so that they eventually meet the exit condition. If they don't change as expected, or change in the wrong way, the exit condition may never be met, resulting in infinite recursion and a "Stack Overflow" error.

Test the recursive procedure with a variety of inputs to see whether it always results in a "Stack Overflow" error or only with certain inputs. This can give you an idea of where the problem lies.

Modify the recursive procedure to avoid the "Stack Overflow" error. This could involve changing the exit condition, or changing how the arguments or local variables are modified.

Here are a few common ways to fix a "Stack Overflow" error in a recursive procedure:

* **Change the exit condition**: Check your exit condition and adjust it if necessary. Perhaps the condition is incorrect or too restrictive, causing the recursion to continue endlessly.

* **Change the recursion**: If the call stack is filling up because the recursion goes too deep, even if the exit condition is correct, you may need to reduce the depth of the recursion. You could do this by changing the logic of the procedure so that it doesn't need to recurse as deeply, or by using an iterative process instead of a recursive one.

* **Increase the call stack size**: If the recursion needs to go deep and you can't or don't want to change the procedure, you might consider increasing the size of the call stack. However, this is usually not a good solution because it just delays the problem and can unnecessarily consume system resources.

Remember that you will need to recompile and test your code after making any changes to ensure the modifications have addressed the problem.

Finally, verify that the fix worked by retesting the recursive procedure. Make sure it now works correctly for all expected inputs and doesn't cause a "Stack Overflow" error.

Bear in mind that recursion is a powerful tool but can lead to problems like "Stack Overflow" errors if not used carefully. If a recursive procedure can be replaced by one that uses iteration, consider doing so. Iterative solutions are usually more efficient in terms of memory usage and performance, as they don't suffer from the risk of stack overflow errors that can occur with recursive solutions.