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Postings from November 2003
Alan Burlison <Alan.Burlison@sun.com> writes:
>> I have a module (Solaris::Kstat) which implements a tied hash entirely
>> from XSUB code. This works fine in 5.6.1, but cores in 5.8.2.
>
>I've done a bit more digging, and this is failing because in 5.6.1 I was
>setting the keys & values of the tied hashes to be readonly, and this has
>clashed with the way the 'Restricted hash' functionality introduced
>post-5.6.1 which also uses the READONLY flags. The implementation of
>restricted hashes isn't exactly clearly documented on perlguts, so I haven't
>yet figured out exactly what I am doing wrong. I'm setting/unsetting
>READONLY on the hashes themselves, and on the entries returned by
>hv_fetch(), but obviously this isn't correct. I'm getting the SEGV in
>Perl_hv_clear, here:
>
> I32 i;
> HE* entry;
> for (i = 0; i <= (I32) xhv->xhv_max; i++) {
>---> entry = ((HE**)xhv->xhv_array)[i];
>
>because xhv->xhv_array is NULL - I have no idea why yet. Can anyone shed
>any light on exactly how the READONLY flags are supposed to be set to get
>the various restricted hash behaviours?
It is _reasonably_ intuitive - my memory is:
If you set SvREADONLY on the HV then
the keys become fixed - you can't add anything and if you delete
the hash entry remains with value being a place-holder value.
AFAIK the SvREADONLY of the SVs returned from FETCH are not special.
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