fixed problem when overflow in destination exponent happens

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@2862 280ebfd0-de03-0410-8827-d642c229c3f4

3 files changed, 35 insertions, 5 deletions

diff --git a/mpn_exp.c b/mpn_exp.c
index c11692744..b0bb88cb3 100644
--- a/mpn_exp.c
+++ b/mpn_exp.c
@@ -30,7 +30,10 @@ MA 02111-1307, USA. */
    that is:
    a*2^exp_r <= b^e <= 2^exp_r (a + 2^f),
    where a represents {a, n}, i.e. the integer
-   a[0] + a[1]*B + ... + a[n-1]*B^(n-1) where B=2^BITS_PER_MP_LIMB */
+   a[0] + a[1]*B + ... + a[n-1]*B^(n-1) where B=2^BITS_PER_MP_LIMB
+   
+   Return -2 if an overflow occurred in the computation of exp_r.
+*/
 
 long
 mpfr_mpn_exp (mp_limb_t *a, mp_exp_t *exp_r, int b, mp_exp_t e, size_t n)
@@ -91,7 +94,17 @@ mpfr_mpn_exp (mp_limb_t *a, mp_exp_t *exp_r, int b, mp_exp_t e, size_t n)
 
       /* set {c+n, 2n1-n} to 0 : {c, n} = {a, n}^2*K^n */
 
-      f = 2 * f + n * BITS_PER_MP_LIMB;
+      /* check overflow on f */
+      {
+        mp_exp_t oldf = f;
+        f = 2 * f;
+        if (f / 2 != oldf)
+          {
+            TMP_FREE(marker);
+            return -2;
+          }
+      }
+      f += n * BITS_PER_MP_LIMB;
       if ((c[2*n - 1] & MPFR_LIMB_HIGHBIT) == 0)
         {
           /* shift A by one bit to the left */
diff --git a/set_str.c b/set_str.c
index d99733791..0c574770e 100644
--- a/set_str.c
+++ b/set_str.c
@@ -269,6 +269,11 @@ mpfr_set_str (mpfr_t x, const char *str, int base, mp_rnd_t rnd)
 	  /* z is allocated at y - n */
 	  z = y - n;
 	  err = mpfr_mpn_exp (z, &exp_z, base, exp_s - (mp_exp_t) pr, n);
+          if (err == -2) /* overflow in exp_z, return Inf */
+            {
+              exp_y = __mpfr_emax;
+              goto free;
+            }
 	  exact = (exact && (err == -1));
 
 	  /* multiply(y = 0.mant_s[0]...mant_s[pr-1])_base by base^(exp_s-g) */
@@ -363,6 +368,7 @@ mpfr_set_str (mpfr_t x, const char *str, int base, mp_rnd_t rnd)
       exp_y ++;
     }
 
+ free:
   TMP_FREE(marker);
 
   /* Set sign of x before exp since check_range needs a valid sign */
@@ -372,7 +378,7 @@ mpfr_set_str (mpfr_t x, const char *str, int base, mp_rnd_t rnd)
     MPFR_SET_POS(x);
   /* DO NOT USE MPFR_SET_EXP. The exp may be out of range! */
   MPFR_EXP (x) = exp_y + n * BITS_PER_MP_LIMB;
-  res = mpfr_check_range (x, res, rnd );
+  res = mpfr_check_range (x, res, rnd);
 
  end:
   (*__gmp_free_func) (str1, size_str1 * sizeof (char));
diff --git a/tests/tset_str.c b/tests/tset_str.c
index f90db1f34..5e486d022 100644
--- a/tests/tset_str.c
+++ b/tests/tset_str.c
@@ -33,12 +33,12 @@ static void
 check_underflow (void)
 {
   mpfr_t a;
-  mp_exp_t emin;
+  mp_exp_t emin, emax;
   int res;
 
   mpfr_init (a);
 
-  /* Check undeflow */
+  /* Check underflow */
   emin = mpfr_get_emin ();
   mpfr_set_emin (-20);
   res = mpfr_set_str (a, "0.00000000001", 10, GMP_RNDZ);
@@ -52,6 +52,17 @@ check_underflow (void)
     }
   mpfr_set_emin (emin);
 
+  /* check overflow */
+  emax = mpfr_get_emax ();
+  mpfr_set_emax (1073741823); /* 2^30-1 */
+  mpfr_set_str (a, "2E1000000000", 10, GMP_RNDN);
+  if (!mpfr_inf_p (a) || mpfr_sgn (a) < 0)
+    {
+      printf("ERROR for mpfr_set_str (a, \"2E1000000000\", 10, GMP_RNDN);\n");
+      exit (1);
+    }
+  mpfr_set_emax (emax);
+
   mpfr_clear (a);
 }