Fix erfc errno setting on underflow (bug 6786).

1 files changed, 11 insertions, 2 deletions

diff --git a/sysdeps/ieee754/ldbl-128/s_erfl.c b/sysdeps/ieee754/ldbl-128/s_erfl.c
index d9d4195ad2..ef65ed8922 100644
--- a/sysdeps/ieee754/ldbl-128/s_erfl.c
+++ b/sysdeps/ieee754/ldbl-128/s_erfl.c
@@ -96,6 +96,7 @@
  *		erfc/erf(NaN) is NaN
  */
 
+#include <errno.h>
 #include <math.h>
 #include <math_private.h>
 
@@ -918,14 +919,22 @@ __erfcl (long double x)
       r = __ieee754_expl (-z * z - 0.5625) *
 	__ieee754_expl ((z - x) * (z + x) + p);
       if ((sign & 0x80000000) == 0)
-	return r / x;
+	{
+	  long double ret = r / x;
+	  if (ret == 0)
+	    __set_errno (ERANGE);
+	  return ret;
+	}
       else
 	return two - r / x;
     }
   else
     {
       if ((sign & 0x80000000) == 0)
-	return tiny * tiny;
+	{
+	  __set_errno (ERANGE);
+	  return tiny * tiny;
+	}
       else
 	return two - tiny;
     }