AGI Stack Overflow

Creating AGI Stack Overflow Information

By Nick Sonneveld

Last updated 23/2/2001

 

Windows users may encounter the "stack blown error". Most Sierra AGI games work just under Windows. This happens when the stack is becomes filled. The culprits are AGI itself (in the case with Pimp Quest because it is filling around a brushed object in the title screen.. so there's lots of little lines to fill up and all these lines get pushed onto stack) and Windows. I'm not quite sure, but I think Windows has some sort of timer running in DOS mode that is called and pushes a bit too much on the stack.

So while the picture fill routine has a lot of information pushed onto the stack, Windows pushes some extra stuff on and the stack overflows. AGI actually checks if the head of the stack is overwritten and so trips this stack error in the middle of a screen write.