Fix bug of overflow.

Fix bug of ternary value in case of overflow.


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@3585 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 48 insertions, 12 deletions

diff --git a/cosh.c b/cosh.c
index fe90e2907..3f107057c 100644
--- a/cosh.c
+++ b/cosh.c
@@ -57,15 +57,12 @@ mpfr_cosh (mpfr_ptr y, mpfr_srcptr xt , mp_rnd_t rnd_mode)
 
   MPFR_SAVE_EXPO_MARK (expo);
   MPFR_TMP_INIT_ABS(x, xt);
-  
   /* General case */
   {
     /* Declaration of the intermediary variable */
     mpfr_t t, te;
-    
     /* Declaration of the size variable */
     mp_prec_t Ny = MPFR_PREC(y);   /* Precision of output variable */
-    
     mp_prec_t Nt;                  /* Precision of the intermediary variable */
     long int err;                  /* Precision of error */
     MPFR_ZIV_DECL (loop);
@@ -73,7 +70,7 @@ mpfr_cosh (mpfr_ptr y, mpfr_srcptr xt , mp_rnd_t rnd_mode)
     /* compute the precision of intermediary variable */
     /* The optimal number of bits : see algorithms.tex */
     Nt = Ny + 3 + MPFR_INT_CEIL_LOG2 (Ny);
-        
+
     /* initialise of intermediary variables */
     mpfr_init2 (t, Nt);
     mpfr_init2 (te, Nt);
@@ -83,18 +80,28 @@ mpfr_cosh (mpfr_ptr y, mpfr_srcptr xt , mp_rnd_t rnd_mode)
     for (;;)
       {
 	/* Compute cosh */
+        mpfr_clear_flags ();
 	mpfr_exp (te, x, GMP_RNDD);         /* exp(x) */
+        /* exp can overflow (but not underflow since x>0) */
+        /* BUG/TODO/FIXME: exp can overflow but cosh may be representable! */
+        if (MPFR_UNLIKELY (mpfr_overflow_p ()))
+          {
+            inexact = mpfr_overflow (y, rnd_mode, MPFR_SIGN_POS);
+            MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, MPFR_FLAGS_OVERFLOW);
+            break;
+          }
 	mpfr_ui_div (t, 1, te, GMP_RNDU);   /* 1/exp(x) */
 	mpfr_add (t, te, t, GMP_RNDU);      /* exp(x) + 1/exp(x)*/
 	mpfr_div_2ui (t, t, 1, GMP_RNDN);   /* 1/2(exp(x) + 1/exp(x))*/
-	
-	/* Estimation of the error */
+
+        /* Estimation of the error */
 	err = Nt - 3;
-	 
 	/* Check if we can round */
-	if (MPFR_UNLIKELY (MPFR_IS_INF (t)) 
-	    || MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
-	  break;
+	if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
+          {
+            inexact = mpfr_set (y, t, rnd_mode);
+            break;
+          }
 
 	/* Actualisation of the precision */
 	MPFR_ZIV_NEXT (loop, Nt);
@@ -102,7 +109,6 @@ mpfr_cosh (mpfr_ptr y, mpfr_srcptr xt , mp_rnd_t rnd_mode)
         mpfr_set_prec (te, Nt);
       }
     MPFR_ZIV_FREE (loop);
-    inexact = mpfr_set (y, t, rnd_mode);
 
     mpfr_clear (te);
     mpfr_clear (t);
diff --git a/tests/tcosh.c b/tests/tcosh.c
index 74b138a7b..8f953adb3 100644
--- a/tests/tcosh.c
+++ b/tests/tcosh.c
@@ -32,6 +32,7 @@ static void
 special (void)
 {
   mpfr_t  x, y;
+  int i;
 
   mpfr_init (x);
   mpfr_init (y);
@@ -95,7 +96,36 @@ special (void)
     {
       printf ("Error: mpfr_cosh for prec=32 (2)\n");
       exit (1);
-    }  
+    }
+
+  mpfr_set_prec (x, 2);
+  mpfr_clear_flags ();
+  mpfr_set_str_binary (x, "1E1000000000");
+  i = mpfr_cosh (x, x, GMP_RNDN);
+  MPFR_ASSERTN (MPFR_IS_INF (x) && MPFR_SIGN (x) > 0);
+  MPFR_ASSERTN (mpfr_overflow_p ());
+  MPFR_ASSERTN (i == 1);
+
+  mpfr_clear_flags ();
+  mpfr_set_str_binary (x, "-1E1000000000");
+  i = mpfr_cosh (x, x, GMP_RNDN);
+  MPFR_ASSERTN (MPFR_IS_INF (x) && MPFR_SIGN (x) > 0);
+  MPFR_ASSERTN (mpfr_overflow_p () && !mpfr_underflow_p ());
+  MPFR_ASSERTN (i == 1);
+
+  mpfr_clear_flags ();
+  mpfr_set_str_binary (x, "-1E1000000000");
+  i = mpfr_cosh (x, x, GMP_RNDD);
+  MPFR_ASSERTN (!MPFR_IS_INF (x) && MPFR_SIGN (x) > 0);
+  MPFR_ASSERTN (mpfr_overflow_p () && !mpfr_underflow_p ());
+  MPFR_ASSERTN (i == -1);
+
+  mpfr_clear_flags ();
+  mpfr_set_str_binary (x, "-1E1000000000");
+  i = mpfr_cosh (x, x, GMP_RNDU);
+  MPFR_ASSERTN (MPFR_IS_INF (x) && MPFR_SIGN (x) > 0);
+  MPFR_ASSERTN (mpfr_overflow_p () && !mpfr_underflow_p ());
+  MPFR_ASSERTN (i == 1);
 
   mpfr_clear (x);
   mpfr_clear (y);