[luatex] Fatal error when removing nodelist's tail.

Taco Hoekwater taco at elvenkind.com
Mon Mar 5 09:20:11 CET 2012

On 03/03/2012 12:21 PM, Paul Isambert wrote:
> Hello all,
> The following code produces a fatal error:
> callback.register("ligaturing",
>    function (head)
>      node.remove(head, node.tail(last))
>    end)
> The error is:
> ! This can't happen (linebreak_tail).
> !  ==>  Fatal error occurred, no output PDF file produced!
> The same happens in the "kerning" callback. It also happens even if you add
> another node after the tail (and then remove the latter). I know the manual says
> something about the tail of the list being recalculated, but I wouldn't expect
> that removing the tail would cause an error. As far as I can tell, the error
> happens at paragraph-building time (i.e. in "linebreak_filter").
> Am I doing something wrong, or contemplating a bug?

I think this is a documentation bug. If your callback does not actually
return anything, luatex assumes that the list is unaltered so does not
do any recalculations (in the interest of speed).

Best wishes,

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