Stack Overflow in Delphi

Make sure to compile your project with "optimization" off, "stack frames" on and "use debug .dcu" on to get the most detailed callstack possible. Then post the callstack you get when you hit the stack overflow here (if you have trouble identifying the nature of the problem from it).

Stack overflows could be caused by endless recursion.

You have to be very careful when you write code that has event handlers in it. One thing you can do to help you debug this is, as David says, step INTO rather than over such calls. F7 steps into a call.

Another thing you can do is put a breakpoint at the top of the function GetCategoryById. Now look at your Call Stack. Do you see the repeated name in the stack? This should make it very clear.

What doesn't show up in your question : the "OnCategoryRename" function you posted up here is a subfunction called from a "TForm.Skype1Reply" callback.

To see this, I had to click on your github link - yet I think it is an important point of your problem.

My guess :

• Your "GetCategoryById" function actually sends a query, which triggers "Skype1Reply".
• If the groupname has changed, "Skype1Reply" calls "OnCategoryRename".
• "OnCategoryRename" calls "GetCategoryById"
• "GetCategoryById" triggers "Skype1Reply"
• Somehow, the test saying "if groupname has changed" is still true, so "Skype1Reply" calls "OnCategoryRename"
• "OnCategoryRename" calls "GetCategoryById"
• rinse, repeat

I think a quick and dirty fix would be to change

sCtgName := GetCategoryByID(CategoryID).DisplayName; // Removing THIS line does not produce a Stack Overflow!

with

sCtgName := //find another way to get the new name, which you can probably get from your ICommand object
            pCommand.Reply.ReadDataFromReplyAndGetNewDisplayName;

In the future, I suggest you post your complete code sample for this kind of question.