fixed problem reported by valgrind (thanks to Michael Abshoff)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@4951 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 6 insertions, 4 deletions

diff --git a/mul.c b/mul.c
index 73ad904d3..66c4d0cb6 100644
--- a/mul.c
+++ b/mul.c
@@ -347,7 +347,7 @@ mpfr_mul (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
         mpn_lshift (tmp, tmp, tn, 1); /* tn <= k, so no stack corruption */
     }
   else
-    /* Mulder mulhigh. Disable if squaring, since it is not tuned for
+    /* Mulders' mulhigh. Disable if squaring, since it is not tuned for
        such a case */
     if (MPFR_UNLIKELY (bn > MPFR_MUL_THRESHOLD && b != c))
       {
@@ -450,7 +450,7 @@ mpfr_mul (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
           }
         MPFR_LOG_MSG (("Use mpfr_mulhigh (%lu VS %lu)\n", MPFR_PREC (a), p));
         /* Compute an approximation of the product of b and c */
-        mpfr_mulhigh_n (tmp+k-2*n, bp, cp, n);
+        mpfr_mulhigh_n (tmp + k - 2 * n, bp, cp, n);
         /* now tmp[0]..tmp[k-1] contains the product of both mantissa,
            with tmp[k-1]>=2^(BITS_PER_MP_LIMB-2) */
         b1 = tmp[k-1] >> (BITS_PER_MP_LIMB - 1); /* msb from the product */
@@ -458,9 +458,11 @@ mpfr_mul (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
         /* If the mantissas of b and c are uniformly distributed in (1/2, 1],
            then their product is in (1/4, 1/2] with probability 2*ln(2)-1
            ~ 0.386 and in [1/2, 1] with probability 2-2*ln(2) ~ 0.614 */
-        tmp += k - tn;
         if (MPFR_UNLIKELY (b1 == 0))
-          mpn_lshift (tmp, tmp, tn, 1);
+          /* Warning: the mpfr_mulhigh_n call above only surely affects
+             tmp[k-n-1..k-1], thus we shift only those limbs */
+          mpn_lshift (tmp + k - n - 1, tmp + k - n - 1, n + 1, 1);
+        tmp += k - tn;
         MPFR_ASSERTD (MPFR_LIMB_MSB (tmp[tn-1]) != 0);
 
         if (MPFR_UNLIKELY (!mpfr_round_p (tmp, tn, p+b1-1, MPFR_PREC(a)