There are two key characteristics in the current Stack class:1. an array may get bigger, but it will never get smaller, even when a stack is copied, and even if the stack size shrinks.2. popped objects won't be clobbered from an array.Therefore, once an object is recorded to ostack or rstack, the only way for them to be removed is for the entry to be overwritten by another object, but this may never happen (the stack size may never grows back to the same size.) IOW, a Stack retain references to objects even after they are popped (this alone is OK, as popped objects are just copied into stack), and those unnecessary references get copied to successive Stack objects created from it. This causes memory leak for a long running "thread".The fix is actually easy, which is to change the copy constructor of Stack so that it only copies the valid region of the parent array.
Sure ...makes sense. Good finding!
The only algorithm I can think of to do this require a lot of additional local variables on each stack frame (6 ints to record the stack top while Continuation1 is being restored --- we can use this value while capturing Continuation2.)I don't know if this cost is worth the benefit. If the memory foot print is a concern, maybe it's easier to capture all stack frames first and then find the common part later. I suspect we need more user experience.It's also bit tricky because Stacks will share their tops, not their roots.
I know it's a bit tricky ...and whether it's worth the hassle is really the question. But we can leave that for later ;) cheers -- Torsten
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