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authorJoseph Myers <joseph@codesourcery.com>2012-03-19 20:13:10 +0000
committerJoseph Myers <joseph@codesourcery.com>2012-03-19 20:14:26 +0000
commit1897ad44326bb7761dcda46132ae303f7288aba9 (patch)
treefd8357b0066902deb5b6b9476b8c456f68ffc56e /math/s_clog10.c
parent7726d6a95d5a2c08c8d43186002f040b9b889c27 (diff)
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Fix clog overflow/underflow (bug 13629).
Diffstat (limited to 'math/s_clog10.c')
-rw-r--r--math/s_clog10.c28
1 files changed, 25 insertions, 3 deletions
diff --git a/math/s_clog10.c b/math/s_clog10.c
index 3eb9c518a8..9d366d6f2b 100644
--- a/math/s_clog10.c
+++ b/math/s_clog10.c
@@ -1,5 +1,5 @@
 /* Compute complex base 10 logarithm.
-   Copyright (C) 1997, 2011 Free Software Foundation, Inc.
+   Copyright (C) 1997-2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
 
@@ -20,7 +20,10 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
+#include <float.h>
 
+/* log_10 (2).  */
+#define M_LOG10_2 0.3010299956639811952137388947244930267682
 
 __complex__ double
 __clog10 (__complex__ double x)
@@ -40,8 +43,27 @@ __clog10 (__complex__ double x)
   else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
     {
       /* Neither real nor imaginary part is NaN.  */
-      __real__ result = __ieee754_log10 (__ieee754_hypot (__real__ x,
-							  __imag__ x));
+      double d;
+      int scale = 0;
+
+      if (fabs (__real__ x) > DBL_MAX / 2.0
+	  || fabs (__imag__ x) > DBL_MAX / 2.0)
+	{
+	  scale = -1;
+	  __real__ x = __scalbn (__real__ x, scale);
+	  __imag__ x = __scalbn (__imag__ x, scale);
+	}
+      else if (fabs (__real__ x) < DBL_MIN
+	       && fabs (__imag__ x) < DBL_MIN)
+	{
+	  scale = DBL_MANT_DIG;
+	  __real__ x = __scalbn (__real__ x, scale);
+	  __imag__ x = __scalbn (__imag__ x, scale);
+	}
+
+      d = __ieee754_hypot (__real__ x, __imag__ x);
+
+      __real__ result = __ieee754_log10 (d) - scale * M_LOG10_2;
       __imag__ result = M_LOG10E * __ieee754_atan2 (__imag__ x, __real__ x);
     }
   else