Han-Wen Nienhuys <[EMAIL PROTECTED]> writes: > Does your patch solve the problem that cyclical structures (values that > point back to keys) should also be GC-ed?
I guess you're talking about cyclical structures in doubly-weak alist vectors. If so, it apparently does since if both WEAK_VALUES and WEAK_KEYS are false in both functions, then neither the key nor the value will ever be marked by those functions. Actually, I've spent some time re-reviewing this patch and I'm having starting to have a headache. But anyway, here are a few thoughts. 1. The tests in `weaks.test' are broken in several ways, not only because "we have no way of knowing for certain that the object is really dead" as stated there. * First, they assume that (begin (hashq-set! h "a string" 123) (hashq-ref h "a string)) returns true. This is wrong since `hashq-ref' uses `eq?' to compare keys, and `(eq? "a string" "a string")' returns #f. Instead, it could use `hash-map->list'. * Second, it should perform a `(read-disable 'positions)' since source properties rely on a weakly-keyed hash table where keys are source expressions. 2. The C test I submitted, unlike `weaks.test', can *reliably* determine whether an object was swept. However, it is clearly not as complete as `weaks.test'. 3. Given the level of non-determinism I've been able to observe, I'm afraid leaks are causing us difficulties. For instance, while testing weakly-key alist vectors "by hand" in a REPL, it occurred to me that the weak-key pair would reliably die, *unless* the hash table was written (I mean using `write'): guile> (define h (make-doubly-weak-alist-vector 12)) guile> (hashq-set! h "sdf" "paf") guile> (hashq-set! h "hello" "world") guile> (gc) guile> h #w(() () () () () () () () () () () ()) The same but print H before calling `gc': guile> (hashq-set! h "sdf" "paf") guile> (hashq-set! h "hello" "world") guile> h #w((("hello" . "world") ("sdf" . "paf")) () () () () () () () () () () ()) guile> (gc) guile> (gc) guile> (gc) guile> h #w((("hello" . "world") ("sdf" . "paf")) () () () () () () () () () () ()) 4. Looking a Bruno Haible's paper[0] on this topic, it seems that getting it right is, well, pretty hard. ;-) > Why are you storing SCM references as properties? It's more efficient > both in time and space to use a SCM member in my_object_t. That's the whole point of the test: object properties are used because they involve weak hash tables. Thanks, Ludovic. [0] http://www.haible.de/bruno/papers/cs/weak/WeakDatastructures-writeup.html _______________________________________________ Guile-devel mailing list Guile-devel@gnu.org http://lists.gnu.org/mailman/listinfo/guile-devel