OK, I understand; happens just when changing to extended arguments.
Not sure yet how to fix.

Quoting jpff@cs.bath.ac.uk:

> There is a break at 1998 (-PMAX) arguments when it becomes extended   
> arguments
> This code has never been tested strongly so I might have got it wrong.
>
> The error I see is a memory allocation issue leading to a double free.
> Not yet tried with valgrind or even read the code
> ==John ff