trivial-garbage-devel

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trivial-garbage-devel@common-lisp.net

July 2019

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2 discussions

Re: Testing if the implementation can support weak pointers
by Luís Oliveira 30 Jul '19

30 Jul '19

OK. I'd like to cover the other features too. How about signalling a tg:unsupported-weak-operation error? Would that work for your use case? This would be similar to the current mode of operation (except we currently signal a generic simple-error). Cheers, Luís On Tue, Jul 30, 2019, 2:12 AM Name Here <theemacsshibe(a)gmail.com> wrote: > Yes, we're trying to factor out the implementation-specific code so that > only trivial-garbage needs to be updated for new implementations with weak > pointers, but we also want Flexichain to mostly work if the implementation > does not support weak pointers, falling back to strong pointers in that > case. >

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Testing if the implementation can support weak pointers
by Name Here 29 Jul '19

29 Jul '19

Hello everyone, I was wondering if there is a way to test if the implementation we are running on can create weak pointers. In the case of Flexichain (and I think this might be a possibility for other libraries) using weak pointers isn't completely required, but it's preferred to avoid leaking memory slowly. Currently Flexichain has its own 15-line function that creates weak pointers, which is very similar to that of trivial-garbage, except that it returns the provided value if it cannot create a weak pointer (after warning the user at load-time). We'd like to replace this with a call to trivial-garbage:make-weak-pointer to avoid duplication, but we also want to fall back to just returning the value as previously mentioned; I could do (or (tg:make-weak-pointer value) value) as it will fall through to returning nil, but that feels icky and then I need to figure out a similar trick for weak-pointer-value. If there isn't such a test, I have written a trivial implementation, simply gathering all the #+ forms to choose a constant to return: https://github.com/nodefunallowed/trivial-garbage/blob/master/trivial-garba… Again, this is probably good for a class of programs that uses weak pointers in a way that isn't strictly necessary but very useful. Thanks very much.

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