fixed bug in mpfr_set_f for huge argument

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@3979 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 42 insertions, 2 deletions

diff --git a/set_f.c b/set_f.c
index eeb7baf7b..57707a067 100644
--- a/set_f.c
+++ b/set_f.c
@@ -80,7 +80,19 @@ mpfr_set_f (mpfr_ptr y, mpf_srcptr x, mp_rnd_t rnd_mode)
       inexact = 0;
     }
 
-  MPFR_SET_EXP(y, EXP(x) * BITS_PER_MP_LIMB - cnt + carry);
+  /* warning: EXP(x) * BITS_PER_MP_LIMB may exceed the maximal exponent */
+  if (EXP(x) > 1 + (__mpfr_emax - 1) / BITS_PER_MP_LIMB)
+    {
+      /* EXP(x) >= 2 + floor((__mpfr_emax-1)/BITS_PER_MP_LIMB)
+	 EXP(x) >= 2 + (__mpfr_emax - BITS_PER_MP_LIMB) / BITS_PER_MP_LIMB
+	        >= 1 + __mpfr_emax / BITS_PER_MP_LIMB
+         EXP(x) * BITS_PER_MP_LIMB >= __mpfr_emax + BITS_PER_MP_LIMB
+	 Since 0 <= cnt <= BITS_PER_MP_LIMB-1, and 0 <= carry <= 1,
+	 we have then EXP(x) * BITS_PER_MP_LIMB - cnt + carry > __mpfr_emax */
+      MPFR_SET_EXP(y, __mpfr_emax + 1);
+    }
+  else
+    MPFR_SET_EXP(y, EXP(x) * BITS_PER_MP_LIMB - (mp_exp_t) cnt + carry);
 
-  return inexact;
+  return mpfr_check_range (y, inexact, rnd_mode);
 }
diff --git a/tests/tset_f.c b/tests/tset_f.c
index b96f4abbc..716e1814f 100644
--- a/tests/tset_f.c
+++ b/tests/tset_f.c
@@ -22,6 +22,7 @@ MA 02110-1301, USA. */
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
+#include <limits.h> /* for ULONG_MAX */
 
 #include "mpfr-test.h"
 
@@ -131,6 +132,33 @@ main (void)
       mpf_mul_2exp (y, y, 1);
     }
 
+  mpf_set_ui (y, 1);
+  mpf_mul_2exp (y, y, ULONG_MAX);
+  mpfr_set_f (x, y, GMP_RNDN);
+  if (mpfr_inf_p (x) == 0 || mpfr_cmp_ui (x, 0) < 0)
+    {
+      printf ("Error: mpfr_set_f (x, y, GMP_RNDN) for y=2^ULONG_MAX\n");
+      exit (1);
+    }
+
+  mpf_set_ui (y, 1);
+  mpf_mul_2exp (y, y, __mpfr_emax);
+  mpfr_set_f (x, y, GMP_RNDN);
+  if (mpfr_inf_p (x) == 0 || mpfr_cmp_ui (x, 0) < 0)
+    {
+      printf ("Error: mpfr_set_f (x, y, GMP_RNDN) for y=2^__mpfr_emax\n");
+      exit (1);
+    }
+
+  mpf_set_ui (y, 1);
+  mpf_mul_2exp (y, y, __mpfr_emax - 1);
+  mpfr_set_f (x, y, GMP_RNDN);
+  if (mpfr_cmp_ui_2exp (x, 1, __mpfr_emax - 1) != 0)
+    {
+      printf ("Error: mpfr_set_f (x, y, GMP_RNDN) for y=2^(__mpfr_emax-1)\n");
+      exit (1);
+    }
+
   mpfr_clear (x);
   mpf_clear (y);
   mpf_clear (z);