[src/ai.c] Fixed handling of reduced exponent range.

[tests/tai.c] Added corresponding test cases (in addition to what
  has been done in tgeneric.c).
(merged changesets r12070-12072,12074-12075 from the trunk)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/4.0@12094 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 46 insertions, 2 deletions

diff --git a/src/ai.c b/src/ai.c
index abfd0ec84..9f022e6c8 100644
--- a/src/ai.c
+++ b/src/ai.c
@@ -576,7 +576,6 @@ mpfr_ai2 (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd)
     } /* End of ZIV loop */
 
   MPFR_ZIV_FREE (loop);
-  MPFR_SAVE_EXPO_FREE (expo);
 
   r = mpfr_set (y, result, rnd);
 
@@ -592,7 +591,8 @@ mpfr_ai2 (mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd)
   mpfr_clear (temp1);
   mpfr_clear (temp2);
 
-  return r;
+  MPFR_SAVE_EXPO_FREE (expo);
+  return mpfr_check_range (y, r, rnd);
 }
 
 /* We consider that the boundary between the area where the naive method
diff --git a/tests/tai.c b/tests/tai.c
index 9df0c2a94..c6b82b20c 100644
--- a/tests/tai.c
+++ b/tests/tai.c
@@ -90,11 +90,55 @@ check_zero (void)
   mpfr_clear (r);
 }
 
+static void
+bug20180107 (void)
+{
+  mpfr_t x, y, z;
+  mpfr_exp_t emin;
+  int inex;
+  mpfr_flags_t flags;
+
+  mpfr_init2 (x, 152);
+  mpfr_init2 (y, 11);
+  mpfr_init2 (z, 11);
+  mpfr_set_str_binary (x, "0.11010101100111000111001001010110101001100001011110101111000010100111011101011110000100111011101100100100001010000110100011001000111010010001110000011100E5");
+  emin = mpfr_get_emin ();
+  mpfr_set_emin (-134);
+  mpfr_clear_flags ();
+  inex = mpfr_ai (y, x, MPFR_RNDA);
+  flags = __gmpfr_flags;
+  /* result should be 0.10011100000E-135 with unlimited exponent range,
+     and thus should be rounded to 0.1E-134 */
+  mpfr_set_str_binary (z, "0.1E-134");
+  MPFR_ASSERTN (mpfr_equal_p (y, z));
+  MPFR_ASSERTN (inex > 0);
+  MPFR_ASSERTN (flags == (MPFR_FLAGS_UNDERFLOW | MPFR_FLAGS_INEXACT));
+
+  mpfr_set_prec (x, 2);
+  mpfr_set_str_binary (x, "0.11E7");
+  mpfr_set_prec (y, 2);
+  mpfr_clear_flags ();
+  inex = mpfr_ai (y, x, MPFR_RNDA);
+  flags = __gmpfr_flags;
+  /* result should be 1.0E-908 with unlimited exponent range,
+     and thus should be rounded to 0.1E-134 */
+  mpfr_set_str_binary (z, "0.1E-134");
+  MPFR_ASSERTN (mpfr_equal_p (y, z));
+  MPFR_ASSERTN (inex > 0);
+  MPFR_ASSERTN (flags == (MPFR_FLAGS_UNDERFLOW | MPFR_FLAGS_INEXACT));
+
+  mpfr_set_emin (emin);
+  mpfr_clear (x);
+  mpfr_clear (y);
+  mpfr_clear (z);
+}
+
 int
 main (int argc, char *argv[])
 {
   tests_start_mpfr ();
 
+  bug20180107 ();
   check_large ();
   check_zero ();