In QROMB.C is the code:

if (j >= K) {
polint(&h[j-K],&s[j-K],K,0.0,&ss,&dss);
if (fabs(dss) <= EPS*fabs(ss)) return ss;
}

If j equals K, the first argument of polint will point to h[0], which has not been set to anything.

Dear Richard,

The code is just passing the address of the start of the array in this case. However, polint itself never uses data in h[0], only from h[1] on.

Saul Teukolsky