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Postings from December 2011
On Fri Dec 02 11:08:09 2011, davem wrote:
>
> This is a bug report for perl from davem@iabyn.com,
> generated with the help of perlbug 1.39 running under perl 5.15.5.
>
> This fails:
>
> use threads;
>
> my $s = threads->new(sub { return sub { $::x = 1} })->join;
> $s->();
> print "ok\n" if $::x == 1;
>
> When the thread is created, *::x (and thus $::x) are cloned into the
> child
> thread. When it returns the anon sub, that sub is cloned back into the
> parent thread, and by extension, everything in its pad, including,
> *::x.
> This leaves two copies of *::x in the parent thread, one linked to
> from
> %::, and one from &$s's pad.
>
> I spotted this due to my work in the 're_eval' bug; now that qr//s are
> proper closures, this returns a regex that sets the wrong $::x:
>
> my $s = threads->new(sub { return qr/(?{ $::x = 1})/ })->join;
The cloning code avoids duplicating stashes during a join if they exist
in the parent thread. The relevant code is in S_sv_dup_common in sv.c:
if(param->flags & CLONEf_JOIN_IN) {
/** We are joining here so we don't want do clone
something that is bad **/
if (SvTYPE(sstr) == SVt_PVHV) {
const HEK * const hvname = HvNAME_HEK(sstr);
if (hvname) {
/** don't clone stashes if they already exist **/
dstr = MUTABLE_SV(gv_stashpvn(HEK_KEY(hvname), HEK_LEN(hvname),
HEK_UTF8(hvname) ?
SVf_UTF8 : 0));
ptr_table_store(PL_ptr_table, sstr, dstr);
return dstr;
}
}
}
Should this be changed to include globs as well? (And I suppose
orphaned globs *should* be cloned, right?) Would it apply just to those
in op trees, or to typeglobs in general?
--
Father Chrysostomos
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