[src/{div_2si.c,div_2ui.c,mul_2si.c}] Fixed overflow case when n = 0.

[tests/tmul_2exp.c] Added overflow tests (triggering the above bugs).
(merged changesets r9593,9595-9598 from the trunk, with mpfr_flags_t
replaced by unsigned int)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/3.1@9608 280ebfd0-de03-0410-8827-d642c229c3f4

4 files changed, 78 insertions, 3 deletions

diff --git a/src/div_2si.c b/src/div_2si.c
index c7da6a058..0a86b79f2 100644
--- a/src/div_2si.c
+++ b/src/div_2si.c
@@ -49,7 +49,7 @@ mpfr_div_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mpfr_rnd_t rnd_mode)
             rnd_mode = MPFR_RNDZ;
           return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y));
         }
-      else if (MPFR_UNLIKELY(n < 0 && (__gmpfr_emax < MPFR_EMIN_MIN - n ||
+      else if (MPFR_UNLIKELY(n <= 0 && (__gmpfr_emax < MPFR_EMIN_MIN - n ||
                                        exp > __gmpfr_emax + n)) )
         return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y));
 
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/src/mul_2si.c b/src/mul_2si.c
index b9293e2a1..0b02e2940 100644
--- a/src/mul_2si.c
+++ b/src/mul_2si.c
@@ -39,7 +39,7 @@ mpfr_mul_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mpfr_rnd_t rnd_mode)
     {
       mpfr_exp_t exp = MPFR_GET_EXP (x);
       MPFR_SETRAW (inexact, y, x, exp, rnd_mode);
-      if (MPFR_UNLIKELY( n > 0 && (__gmpfr_emax < MPFR_EMIN_MIN + n ||
+      if (MPFR_UNLIKELY(n >= 0 && (__gmpfr_emax < MPFR_EMIN_MIN + n ||
                                    exp > __gmpfr_emax - n)))
         return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y));
       else if (MPFR_UNLIKELY(n < 0 && (__gmpfr_emin > MPFR_EMAX_MAX + n ||
diff --git a/tests/tmul_2exp.c b/tests/tmul_2exp.c
index 61ad34d82..5c5972bad 100644
--- a/tests/tmul_2exp.c
+++ b/tests/tmul_2exp.c
@@ -242,6 +242,76 @@ large0 (void)
   large (MPFR_EMAX_MAX);
 }
 
+/* Cases where the function overflows on n = 0 when rounding is like
+   away from zero. */
+static void
+overflow0 (mpfr_exp_t emax)
+{
+  mpfr_exp_t old_emax;
+  mpfr_t x, y1, y2;
+  int neg, r, op;
+  static char *sop[4] = { "mul_2ui", "mul_2si", "div_2ui", "div_2si" };
+
+  old_emax = mpfr_get_emax ();
+  set_emax (emax);
+
+  mpfr_init2 (x, 8);
+  mpfr_inits2 (6, y1, y2, (mpfr_ptr) 0);
+
+  mpfr_set_inf (x, 1);
+  mpfr_nextbelow (x);
+
+  for (neg = 0; neg <= 1; neg++)
+    {
+      RND_LOOP (r)
+        {
+          int inex1, inex2;
+          unsigned int 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;
+          for (op = 0; op < 4; op++)
+            {
+              mpfr_clear_flags ();
+              inex2 =
+                op == 0 ? mpfr_mul_2ui (y2, x, 0, (mpfr_rnd_t) r) :
+                op == 1 ? mpfr_mul_2si (y2, x, 0, (mpfr_rnd_t) r) :
+                op == 2 ? mpfr_div_2ui (y2, x, 0, (mpfr_rnd_t) r) :
+                op == 3 ? mpfr_div_2si (y2, x, 0, (mpfr_rnd_t) r) :
+                (MPFR_ASSERTN (0), 0);
+              flags2 = __gmpfr_flags;
+              if (!(mpfr_equal_p (y1, y2) &&
+                    SAME_SIGN (inex1, inex2) &&
+                    flags1 == flags2))
+                {
+                  printf ("Error in overflow0 for %s, mpfr_%s, emax = %"
+                          MPFR_EXP_FSPEC "d,\nx = ",
+                          mpfr_print_rnd_mode ((mpfr_rnd_t) r), sop[op],
+                          (mpfr_eexp_t) emax);
+                  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, y1, y2, (mpfr_ptr) 0);
+  set_emax (old_emax);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -334,6 +404,11 @@ main (int argc, char *argv[])
   underflow0 ();
   large0 ();
 
+  if (mpfr_get_emax () != MPFR_EMAX_MAX)
+    overflow0 (mpfr_get_emax ());
+  overflow0 (MPFR_EMAX_MAX);
+  overflow0 (-1);
+
   tests_end_mpfr ();
   return 0;
 }