gsc_add_seg
static int gsc_add_seg(struct gen_sc *, double, double, double,
gsc_add_seg(gsc, 0.0, 0.0, (double)sc->d, (double)sc->m1);
gsc_add_seg(gsc, (double)sc->d, 0.0, HUGE_VAL, (double)sc->m2);
static int gsc_add_seg(struct gen_sc *, double, double, double, double);
gsc_add_seg(gsc, 0, 0, (double)sc->d, (double)sc->m1);
gsc_add_seg(gsc, (double)sc->d, 0, HUGE_VAL, (double)sc->m2);
if (gsc_add_seg(gsc, x, y, d, -m) < 0)