Hans Hagen j.hagen at xs4all.nl
Wed May 27 10:05:32 CEST 2020

```On 5/27/2020 9:21 AM, Hironobu Yamashita wrote:
> Hi,
>
>> Thanh has committed a fix to the pdftex repo (r828).
>
> Thanks.  I think the additions of (r<>null) are no-op
> thus can be removed.  (It does no harm, though.)

if there is a loop over a list you want to quit when you run out of
items; vlink(n) doesn't do a check if n equals null, it accesses a field
in a node (and likely the next field in a null node is some weird random
value which then brings you to whatever memory is related etc)

> I wonder if there is still some possibility of uninitialized
> save_tail (which is 0, not null).
null is actually 0 in tex

when used this way save-tail is just a number pointing to a slot in a
memory array where a node blob (of whatever length) sits

Hans

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