make pd_unbind safe (+ improve stack overflow protection) #849
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the current overflow protection only works for a *single* recursion path. for more than 1 path (e.g. several outlets feeding back to the same inlet), Pd would end up in an infinite loop. once the stacklimit is reached, we set an overflow flag to prevent any further messaging until the stack got completely unwound.
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umlaeute
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Sep 14, 2022
… symbols use arrays instead of intrinsic lists to optimize for copying and iterating. unbinding may be slightly slower, but it doesn't happen too often anyway.
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a) make
pd_unbindsafeCurrently, it is unsafe to dynamically unbind symbols because some other object could be sending to them.
The solution is to simply make a copy of the bind list before iterating over it. A counter keeps track of the total number of items. We use stack allocation up to a certain limit and then switch to heap allocation to avoid a stack overflow.
To make copying as fast as possible, I changed the bind list implementation to a dynamically sized array instead of a linked list. (This is also better for cache coherency).
In a way, this not much different than how
[list]has to output a copy of the stored list to prevent other objects to modify the list while iterating over it.This PR would finally make it possible to safely implement dyamically settable
[receive]objects (#604), and make existing similar objects safe, for example iemgui's[receive(method.b) improve stack overflow protection
The current overflow protection only works for a single recursion path. For more than 1 path (e.g. several outlets feeding back to the same inlet), Pd would end up in an infinite loop. Once the stacklimit is reached, I set an overflow flag to prevent any further messaging until the stack got completely unwound.