Fix clog, clog10 spurious underflow exceptions (bug 14337).

1 files changed, 14 insertions, 9 deletions

diff --git a/math/s_clog.c b/math/s_clog.c
index 15e5e9c..2249e86 100644
--- a/math/s_clog.c
+++ b/math/s_clog.c
@@ -40,25 +40,30 @@ __clog (__complex__ double x)
   else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
     {
       /* Neither real nor imaginary part is NaN.  */
+      double absx = fabs (__real__ x), absy = fabs (__imag__ x);
       double d;
       int scale = 0;
 
-      if (fabs (__real__ x) > DBL_MAX / 2.0
-	  || fabs (__imag__ x) > DBL_MAX / 2.0)
+      if (absx > DBL_MAX / 2.0)
 	{
 	  scale = -1;
-	  __real__ x = __scalbn (__real__ x, scale);
-	  __imag__ x = __scalbn (__imag__ x, scale);
+	  absx = __scalbn (absx, scale);
+	  absy = (absy >= DBL_MIN * 2.0 ? __scalbn (absy, scale) : 0.0);
 	}
-      else if (fabs (__real__ x) < DBL_MIN
-	       && fabs (__imag__ x) < DBL_MIN)
+      else if (absy > DBL_MAX / 2.0)
+	{
+	  scale = -1;
+	  absx = (absx >= DBL_MIN * 2.0 ? __scalbn (absx, scale) : 0.0);
+	  absy = __scalbn (absy, scale);
+	}
+      else if (absx < DBL_MIN && absy < DBL_MIN)
 	{
 	  scale = DBL_MANT_DIG;
-	  __real__ x = __scalbn (__real__ x, scale);
-	  __imag__ x = __scalbn (__imag__ x, scale);
+	  absx = __scalbn (absx, scale);
+	  absy = __scalbn (absy, scale);
 	}
 
-      d = __ieee754_hypot (__real__ x, __imag__ x);
+      d = __ieee754_hypot (absx, absy);
 
       __real__ result = __ieee754_log (d) - scale * M_LN2;
       __imag__ result = __ieee754_atan2 (__imag__ x, __real__ x);