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Postings from September 2011
On Tue Sep 06 21:44:13 2011, sprout wrote:
> On Tue Sep 06 18:02:19 2011, sprout wrote:
> > The best way to attach a destructor to the shared SV would be to use
> > custom free magic.
>
> But that causes problems if our free magic function looks like this:
>
> int
> sharedsv_scalar_mg_free(pTHX_ SV *sv, MAGIC *mg)
> {
> PERL_UNUSED_ARG(mg);
> /* We do not use CALLER_CONTEXT here, as whatever code herein
triggered
> this free might still need its temps. */
> aTHX = caller_perl;
> sv_2mortal(S_sharedsv_new_private(aTHX_ sv));
> return (0);
> }
>
> We have to use sv_2mortal, rather than SvREFCNT_dec, as the latter could
> cause a DESTROY method to be called while a lock is held. So I use
> sv_2mortal instead, but that means the sv’s refcount is increased. But
> sv_clear has no logic to handle magic giving an SV a new lease on life.
> It’ll just go ahead and free it anyway, probably causing crashes.
>
> On the other hand, I could dissociate the private SV from the shared SV,
> allowing the shared one to be freed.
But that would mean copying the whole thing, which, while trivial for
scalars, is more complicated for hashes and arrays.
> > An alternative plan would be to push new proxy scalars on to the calling
> > context’s mortals stack in sharedsv_scalar_store and
> > sharedsv_array_mg_CLEAR, but that would require two iterations when
> > freeing any array or hash.
>
> That’s my fallback if the above does not work.
But that plan does not deal with ref refs.
Oh dear....
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