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From: Borsenkow Andrej <Andrej.Borsenkow@mow.siemens.ru>
To: Zsh hackers list <zsh-workers@sunsite.dk>
Subject: RE: Nasty bug in array-element typeset assignments
Date: Thu, 26 Jul 2001 15:08:38 +0400
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> > > Yes, recent changes has enabled it.
>

Commit log does not have article number, but diffs are here:

<http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/zsh/zsh/Src/builtin.c.diff?r
1=1.44&r2=1.45>

> Really? So what would it do? Make the whole foo array local or just the
> first element? Clearly neither works.
>

Probably, intent was to create new local array.

> > Yuk.  Whoever decided on this has got a job on their hands.
>
> > Typeset is going to get *very* confused.  Each change like this
> multiplies,
>

The problem is here:

   /* Take arguments literally.  Don't glob */
    while ((asg = getasg(*argv++))) {
        if (!typeset_single(name, asg->name,
                            (Param) (paramtab == realparamtab ?
                                     gethashnode2(paramtab, asg->name) :
                                     paramtab->getnode(paramtab,
asg->name)),
                            func, on, off, roff, asg->value, NULL))
            returnval = 1;
    }

We get foo[1]=bar and try to fetch parameter `foo[1]' that does not exist of
course, so later on in typeset_single we believe there is no such parameter.
It means, that we just set element of existing one in

        } else if (PM_TYPE(on) == PM_SCALAR) {
            /*
             * This will either complain about bad identifiers, or will set
             * a hash element or array slice.  This once worked by accident,
             * creating a stray parameter along the way via createparam(),
             * now called below in the isident() branch.
             */
            if (!(pm = setsparam(pname, ztrdup(value ? value : ""))))
                return NULL;
            value = NULL;

Later on we obviously change locality of this array in

    if (keeplocal)
        pm->level = keeplocal;

So, this may work assuming that we change getasg() to properly recognize
subscription.

Note, that this bug affects 4.0.2 as well so we better fix it and issue
4.0.3.

-andrej