Discriminant of non-monic polynomials

[Igor Schein <igor@txc.com>]

Hi, I've encountered several problems with poldisc and nfdisc
commands.  Here's the demonstration:
------------------------------------------------------------------------------
? g(pol)=subst(pol,x,2*x+1) \\ If pol is f(x) then g(pol) is f(2*x+1)
? poldisc(g(polcyclo(57)))
  ***   Warning: normalizing a polynomial with 0 leading term.
  ***   bus error: bug in GP (please report).

? nfdisc(g(x^12-x-1))
  ***   impossible assignment I-->S
? nfdisc(g(polcyclo(23)))
  ***   the PARI stack overflows !!!

  ***   Warning: doubling stack size; new stack = 8000000.
? nfdisc(g(polcyclo(23)))
  ***   the PARI stack overflows !!!

  ***   Warning: doubling stack size; new stack = 16000000.                    
\\keeps doubling until memory is exhausted
------------------------------------------------------------------------------

??nfdisc tells me "preferably monic".  How do I interprete this?  Does
it mean that nfdisc will give reliable output only for monic
polynomials?

??poldisc on the other hand doesn't impose any restrictions on the
input, so the first one must be a true bug.

Thanks
Igor