Fix casinh, casin overflow (bug 14996).

1 files changed, 21 insertions, 7 deletions

diff --git a/math/s_casinhf.c b/math/s_casinhf.c
index 8f4315cbf9..f865e14490 100644
--- a/math/s_casinhf.c
+++ b/math/s_casinhf.c
@@ -20,7 +20,7 @@
 #include <complex.h>
 #include <math.h>
 #include <math_private.h>
-
+#include <float.h>
 
 __complex__ float
 __casinhf (__complex__ float x)
@@ -69,15 +69,29 @@ __casinhf (__complex__ float x)
       rx = fabsf (__real__ x);
       ix = fabsf (__imag__ x);
 
-      __real__ y = (rx - ix) * (rx + ix) + 1.0;
-      __imag__ y = 2.0 * rx * ix;
+      if (rx >= 1.0f / FLT_EPSILON || ix >= 1.0f / FLT_EPSILON)
+	{
+	  /* For large x in the first quadrant, x + csqrt (1 + x * x)
+	     is sufficiently close to 2 * x to make no significant
+	     difference to the result; avoid possible overflow from
+	     the squaring and addition.  */
+	  __real__ y = rx;
+	  __imag__ y = ix;
+	  res = __clogf (y);
+	  __real__ res += (float) M_LN2;
+	}
+      else
+	{
+	  __real__ y = (rx - ix) * (rx + ix) + 1.0;
+	  __imag__ y = 2.0 * rx * ix;
 
-      y = __csqrtf (y);
+	  y = __csqrtf (y);
 
-      __real__ y += rx;
-      __imag__ y += ix;
+	  __real__ y += rx;
+	  __imag__ y += ix;
 
-      res = __clogf (y);
+	  res = __clogf (y);
+	}
 
       /* Give results the correct sign for the original argument.  */
       __real__ res = __copysignf (__real__ res, __real__ x);