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Postings from January 2004
I repeat my plea for someone with knowlege about using TARG to look at
this. Should the rvalue case just create a new mortal sv to return if
TARG is a PVLV?
On Wed, Oct 15, 2003 at 12:18:16AM -0700, Yitzchak Scott-Thoennes <sthoenna@efn.org> wrote:
> On Mon, Oct 13, 2003 at 05:28:49PM -0000, "mconst@csua.berkeley.edu (via RT)" <perlbug-followup@perl.org> wrote:
> > Under perl v5.8.1 on my i386 Debian Linux system, this script:
> >
> > $foo = "a";
> > sub bar: lvalue { substr $foo, 0 }
> > bar = "XXX";
> > print bar, "\n";
> >
> > produces the output "X". I would have expected it to output "XXX",
> > like it does if you make the calls to substr directly instead of
> > through the lvalue function.
>
> Looks like substr is expecting to always or never return an lvalue.
> It gets confused if you first make it return a PVLV TARG and then
> reuse the TARG not considering it is a PVLV.
>
> This is a start:
>
> --- perl/pp.c.orig 2003-10-14 23:55:45.673918400 -0700
> +++ perl/pp.c 2003-10-14 23:58:14.748276800 -0700
> @@ -3079,6 +3079,8 @@
> SvREFCNT_dec(LvTARG(TARG));
> LvTARG(TARG) = SvREFCNT_inc(sv);
> }
> + }
> + if (SvTYPE(TARG) == SVt_PVLV) {
> LvTARGOFF(TARG) = upos;
> LvTARGLEN(TARG) = urem;
> }
> End of Patch.
>
> but it needs more. The non-lvalue but a PVLV case needs to handle
> TARG REFCNT > 1. (Is that check in the right place in the lvalue
> case? Its already done stuff to TARG at the point it decides to do
> TARG = sv_newmortal(). And does it leak? Seems like it should be
> decrementing the old TARGs refcnt before reassigning it.)
>
> Can someone more familiar with TARG reuse take a look at this?
>
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