Ilya Zakharevich on Wed, 20 Jan 1999 21:02:10 -0500

 [Another segfault] in factornf

```(Somehow this does not work with 64M stack, I needed 90M stack to
reach the place I get a segfault.)  This is a debugging cc-compiled
2.0.13 on Solaris.

a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8;i=9;j=10;

\\ homogeneous part
pp=a*x^3+b*x^2*y+c*x*y^2+d*y^3
pp1=deriv(pp,x)
pp2=deriv(pp,y)
pp11=deriv(pp1,x)
pp12=deriv(pp2,x)
pp22=deriv(pp2,y)
qq=pp2^2*pp11-2*pp1*pp2*pp12+pp1^2*pp22
rr=qq/pp

\\ complete cubic
p=a*x^3+b*x^2*y+c*x*y^2+d*y^3 + e*x^2+f*x*y+g*y^2 + h*x+i*y + h
p1=deriv(p,x)
p2=deriv(p,y)
p11=deriv(p1,x)
p12=deriv(p2,x)
p22=deriv(p2,y)

\\ Gives inflection points + 2x points at infinity
q=p2^2*p11-2*p1*p2*p12+p1^2*p22

\\ Gives inflection points
t=q-rr*p-(18*g*a+(-6*f*b+6*e*c))*x*p - (6*g*b + -6*f*c + 18*e*d)*y*p

\\ x-coords of inflection points
res = polresultant(p,t,y)

\\ y-coords of the given inflection point
factornf(p,res)
quit

Results in:

***   segmentation fault: bug in GP (please report).

Ilya
```