[src/div_2ui.c] Fixed overflow case (can occur only when n = 0).

[tests/tmul_2exp.c] Completed the overflow test.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@9595 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 34 insertions, 6 deletions

diff --git a/src/div_2ui.c b/src/div_2ui.c
index 12df43bb7..3aa8b6ae8 100644
--- a/src/div_2ui.c
+++ b/src/div_2ui.c
@@ -32,7 +32,7 @@ mpfr_div_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long n, mpfr_rnd_t rnd_mode)
      rnd_mode),
     ("y[%Pu]=%.*Rg inexact=%d", mpfr_get_prec(y), mpfr_log_prec, y, inexact));
 
-  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
+  if (MPFR_UNLIKELY (n == 0 || MPFR_IS_SINGULAR (x)))
     return mpfr_set (y, x, rnd_mode);
   else
     {
diff --git a/tests/tmul_2exp.c b/tests/tmul_2exp.c
index abbc46915..1e4314b38 100644
--- a/tests/tmul_2exp.c
+++ b/tests/tmul_2exp.c
@@ -239,19 +239,19 @@ large0 (void)
   large (MPFR_EMAX_MAX);
 }
 
-/* Cases where mpfr_div_2ui overflows. */
+/* Cases where mpfr_div_2ui overflows when rounding is like away from zero. */
 static void
 div_overflow (mpfr_exp_t e)
 {
   mpfr_exp_t emax;
-  mpfr_t x, y;
+  mpfr_t x, y1, y2;
   int neg, r;
 
   emax = mpfr_get_emax ();
   set_emax (e);
 
   mpfr_init2 (x, 8);
-  mpfr_init2 (y, 6);
+  mpfr_inits2 (6, y1, y2, (mpfr_ptr) 0);
 
   mpfr_set_inf (x, 1);
   mpfr_nextbelow (x);
@@ -260,12 +260,40 @@ div_overflow (mpfr_exp_t e)
     {
       RND_LOOP (r)
         {
-          mpfr_div_2ui (y, x, 0, (mpfr_rnd_t) r);
+          int inex1, inex2;
+          mpfr_flags_t flags1, flags2;
+
+          /* Even if there isn't an overflow (rounding ~ toward zero),
+             the result is the same as the one of an overflow. */
+          inex1 = mpfr_overflow (y1, (mpfr_rnd_t) r, neg ? -1 : 1);
+          flags1 = MPFR_FLAGS_INEXACT;
+          if (mpfr_inf_p (y1))
+            flags1 |= MPFR_FLAGS_OVERFLOW;
+          mpfr_clear_flags ();
+          inex2 = mpfr_div_2ui (y2, x, 0, (mpfr_rnd_t) r);
+          flags2 = __gmpfr_flags;
+          if (!(mpfr_equal_p (y1, y2) &&
+                SAME_SIGN (inex1, inex2) &&
+                flags1 == flags2))
+            {
+              printf ("Error in div_overflow for %s, x = ",
+                      mpfr_print_rnd_mode ((mpfr_rnd_t) r));
+              mpfr_dump (x);
+              printf ("Expected ");
+              mpfr_dump (y1);
+              printf ("  with inex = %d, flags =", inex1);
+              flags_out (flags1);
+              printf ("Got      ");
+              mpfr_dump (y2);
+              printf ("  with inex = %d, flags =", inex2);
+              flags_out (flags2);
+              exit (1);
+            }
         }
       mpfr_neg (x, x, MPFR_RNDN);
     }
 
-  mpfr_clears (x, y, (mpfr_ptr) 0);
+  mpfr_clears (x, y1, y2, (mpfr_ptr) 0);
   set_emax (emax);
 }