Re: 2 bugs with pols in 2.0.12

[Ilya Zakharevich <ilya@math.ohio-state.edu>]

On Sun, Jan 17, 1999 at 10:58:32PM +0100, Gerhard Niklasch wrote:
> In response to:
> > ? res=-23708160*x^9 - 225566208*x^8 - 1131314688*x^7 - 3968372736*x^6 - \
> > 7276863744*x^5 - 1112932224*x^4 + 22694392512*x^3 + 49279399488*x^2 + \
> > 50845741200*x + 22483386864;
> > ? polgalois(res)
> >   ***   segmentation fault: bug in GP (please report).
> > 
> > ? factornf(res,subst(res,x,y))
> >   ***   bug in subresext, please report
> > 
> > (The second message is triggered even if we do not do polgalois().)
> 
> This is interesting... I began seeing the second phenomenon on my
> old Linux box on one of the pre-2.0.12 snapshots if memory serves
> (errm... it was present in 2.0.12.7),  but since Karim couldn't
> reproduce it, and I couldn't reproduce it when building with -g [*],
> we ended up blaming it on my ancient libc.  As far as I could tell
> from running instrumented code, memory on the C stack was getting
> corrupted even before subresext() was called.
> 
> Gerhard
> 
> [*] (maybe because of compiler hickups with inlining, maybe because
> whatever causes the corruption interacts with the PARI stack allocation
> machinery, which is implemented differently depending on whether we
> build with -g or not)

OK, since it looks compiler-specific: it is OS/2 EMX 0.9c, which is
based on gcc 2.7.2.(1?), with 2.0.12.

Ilya