Re[2]: [Gc] When disappearing links are colle cted before their targets

 Hi Jim,

Here is a small comment update regarding disappearing links -  https://github.com/ivmai/bdwgc/commit/04879212fb2e3418c1c4dc2f3bc4211476ea0560

Friday, 31 Jan 2014, 14:20 +04:00 from Ivan Maidanski <[email protected]>:
>Hi Jim,
>Yes, you are right.
>It is called dangling link - handled (unregistered) automatically except that if you want to manually free an object with a dissappearing link then you should unregister it manually before free.
>Definitely,  documentation should be improved. I'll add info to gc.h.
>Thank you
>----
>Thu, 30 Jan 2014г., 23:37 +04:00 from Jim Pryor <[email protected]>:
>I'm just starting to work with the Boehm GC library, and am trying to
>add weakref functionality to a project that already uses the main
>functions of the library (including finalizers).
>I think I've got a basic understanding of how
>GC_general_register_disappearing_link and nearby functions work.
>However, I wasn't able to tell from the comments or other documentation
>what is the answer to this question:
>If I create a disappearing link L to another object O, but then L ends
>up being collected before O does, when the time comes around for O to be
>collected, we obviously don't in that case want L to still be cleared.
>So do I have to manually create a finalizer for L to
>GC_unregister_disappearing_link it before it gets collected? Or does the
>library take care of this automatically.
>Looking at the source (finalizer.c): I haven't fully digested everything
>here yet, but superficially at least it looks like the answer to my
>question is that the library takes care of this automatically, when it
>invokes the function GC_remove_dangling_disappearing_links.
>I'm writing the list for two reasons: (1) to invite others to correct me
>if I've misunderstood, and (2) to make this question and answer
>available to others who might search for it. (I wasn't able to find any
>explicit discussion of this in my own searches.) Perhaps (3) it'd be
>good to add a sentence or two to the comments in gc.h (or finalize.c)
>declaring explicitly that this is the designed behavior, and that one
>doesn't need to manually unregister weakrefs on one's own, just before
>they're collected.
>--
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