Fix some Newton lengths

Author: fredrik-johansson

src/gr_poly/div_series_newton.c

@@ -63,7 +63,9 @@ _gr_poly_div_series_newton(gr_ptr res, gr_srcptr A, slong Alen, gr_srcptr B, slo
         Bnlen = FLINT_MIN(Blen, n);
         Wlen = FLINT_MIN(Bnlen + m - 1, n);
         W2len = Wlen - m;
+
         FLINT_ASSERT(W2len != 0);
+        FLINT_ASSERT(m < Wlen);
 
         if (have_mulmid)
         {
@@ -89,6 +91,7 @@ _gr_poly_div_series_newton(gr_ptr res, gr_srcptr A, slong Alen, gr_srcptr B, slo
 
     if (have_mulmid)
     {
+        FLINT_ASSERT(m < Wlen);
         status |= _gr_poly_mulmid(W, B, Bnlen, T, m, m, Wlen, ctx);
         status |= _gr_poly_sub(W, GR_ENTRY(A, m, sz), FLINT_MAX(0, FLINT_MIN(Alen - m, n - m)), W, n - m, ctx);
         status |= _gr_poly_mullow(GR_ENTRY(res, m, sz), res, m, W, n - m, n - m, ctx);

src/gr_poly/inv_series_newton.c

@@ -56,7 +56,9 @@ _gr_poly_inv_series_newton(gr_ptr Qinv, gr_srcptr Q, slong Qlen, slong len, slon
         Qnlen = FLINT_MIN(Qlen, n);
         Wlen = FLINT_MIN(Qnlen + m - 1, n);
         W2len = Wlen - m;
+
         FLINT_ASSERT(W2len != 0);
+        FLINT_ASSERT(m < Wlen);
 
         if (have_mulmid)
         {

src/gr_poly/sqrt_series_newton.c

@@ -86,7 +86,8 @@ _gr_poly_sqrt_series_newton(gr_ptr g,
 
     if (have_mulmid)
     {
-        status |= _gr_poly_mulmid(t, v, m, v, m, m, tlen, ctx);
+        if (m < tlen)
+            status |= _gr_poly_mulmid(t, v, m, v, m, m, tlen, ctx);
         status |= _gr_poly_sub(GR_ENTRY(u, m, sz), GR_ENTRY(h, m, sz),
             FLINT_MAX(0, FLINT_MIN(hlen - m, n - m)), t, FLINT_MAX(0, FLINT_MIN(tlen - m, n - m)), ctx);
     }