fixed bug when imax>an

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@796 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 4 insertions, 3 deletions

diff --git a/sub.c b/sub.c
index 9b718896f..feb583e0d 100644
--- a/sub.c
+++ b/sub.c
@@ -303,12 +303,13 @@ mpfr_sub1(a, b, c, rnd_mode, diff_exp)
     if (MPFR_PREC(b)<=MPFR_PREC(a)+cancel) { int i, imax;
       overlap += 2;
       /* invert low limbs */
-      imax = (int)an-(int)bn+cancel1;
+      imax = (int)an - (int)bn + cancel1;
+      if (imax > an) imax = an;
       for (i=0;i<imax;i++) ap[i] = ~ap[i];
       cc = (i) ? mpn_add_1(ap, ap, i, 1) : 1;
-      if (cancel1<bn) mpn_sub_lshift_n(ap+i, bp, bn-cancel1, cancel2, an);
+      if (cancel1 < bn) mpn_sub_lshift_n(ap+i, bp, bn-cancel1, cancel2, an);
       /* warning: mpn_sub_1 doesn't accept a zero length */
-      if (i<an) mpn_sub_1(ap+i, ap+i, an-i, ONE-cc);
+      if (i < an) mpn_sub_1(ap+i, ap+i, an-i, ONE-cc);
     }
     else /* MPFR_PREC(b) > MPFR_PREC(a): we have to truncate b */
       mpn_sub_lshift_n(ap, bp+(bn-an-cancel1), an, cancel2, an);