GF_POLY_SZ
g = bch_alloc(GF_POLY_SZ(m*t), &err);
bch->poly_2t[i] = bch_alloc(GF_POLY_SZ(2*t), &err);
memcpy(dst, src, GF_POLY_SZ(src->deg));
memset(pelp, 0, GF_POLY_SZ(2*t));
memset(elp, 0, GF_POLY_SZ(2*t));
memset(out, 0, GF_POLY_SZ(f->deg));