On Tue, May 19, 2009 at 08:18:17AM -0500, John E. Malmberg wrote:
> Craig A. Berry wrote:
> >So you're saying that these lines in Perl_magic_get in mg.c:
> >
> > case '?':
> > {
> > sv_setiv(sv, (IV)STATUS_CURRENT);
> >#ifdef COMPLEX_STATUS
> > LvTARGOFF(sv) = PL_statusvalue;
> > LvTARGLEN(sv) = PL_statusvalue_vms;
> >#endif
> > }
> >
> >
> >are where the damage occurs? So it looks like the SV in question does
> >not even have the relevant slots (xlv_targlen) we're trying to update
> >here.
>
> Yes.
>
> > I wonder if it's because IPC::Cmd declares $? as local. Maybe we
> >are assuming $? is always lexical but it's not?
>
> I do not know.
That code rings a bell. The only thing I can find that I did near it was:
http://perl5.git.perl.org/perl.git/commit/35f998ddd1e1665f7d0899ae3e50f9262c59d848
However I had a suspicion that I also did something that restricted the upgrade
to the minimal case.
I don't think that "lexical" has anything to do with it - I suspect that the
bug is because IPC::Cmd localises $?, and the new scalar is created like this:
STATIC SV *
S_save_scalar_at(pTHX_ SV **sptr, const U32 flags)
{
dVAR;
SV * const osv = *sptr;
register SV * const sv = *sptr = newSV(0);
PERL_ARGS_ASSERT_SAVE_SCALAR_AT;
if (SvTYPE(osv) >= SVt_PVMG && SvMAGIC(osv) && SvTYPE(osv) != SVt_PVGV) {
if (SvGMAGICAL(osv)) {
const bool oldtainted = PL_tainted;
SvFLAGS(osv) |= (SvFLAGS(osv) &
(SVp_IOK|SVp_NOK|SVp_POK)) >> PRIVSHIFT;
PL_tainted = oldtainted;
}
mg_localize(osv, sv, (flags & SAVEf_SETMAGIC) != 0);
}
return sv;
}
where that call to mg_localize() will upgrade it to PVMG, but not PVLV.
If this is the cause, I'm not sure whether the correct fix is to make
mg_localize generally upgrade the new scalar to the type of the existing
scalar, or special case it for $?.
Nicholas Clark
