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authorJoseph Myers <joseph@codesourcery.com>2012-04-09 22:31:35 +0000
committerJoseph Myers <joseph@codesourcery.com>2012-04-09 22:31:35 +0000
commitbcc8d6617ba029c288fff9680a02b9a3b1caa9c0 (patch)
tree9cb163731d4d165bfe71bad55f59d88c6b420917 /math/s_ctanf.c
parent8a1fbaaf75536088b4d505409e0e87975d8cf8d5 (diff)
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Fix ctan, ctanh overflow (bug 11521).
Diffstat (limited to 'math/s_ctanf.c')
-rw-r--r--math/s_ctanf.c44
1 files changed, 32 insertions, 12 deletions
diff --git a/math/s_ctanf.c b/math/s_ctanf.c
index 5f7f28ad07..4cba559a44 100644
--- a/math/s_ctanf.c
+++ b/math/s_ctanf.c
@@ -1,5 +1,5 @@
/* Complex tangent function for float.
- Copyright (C) 1997, 2005, 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.
@@ -21,7 +21,7 @@
#include <fenv.h>
#include <math.h>
#include <math_private.h>
-
+#include <float.h>
__complex__ float
__ctanf (__complex__ float x)
@@ -50,25 +50,45 @@ __ctanf (__complex__ float x)
}
else
{
- float sin2rx, cos2rx;
+ float sinrx, cosrx;
float den;
+ const int t = (int) ((FLT_MAX_EXP - 1) * M_LN2 / 2);
- __sincosf (2.0 * __real__ x, &sin2rx, &cos2rx);
-
- den = cos2rx + __ieee754_coshf (2.0 * __imag__ x);
+ /* tan(x+iy) = (sin(2x) + i*sinh(2y))/(cos(2x) + cosh(2y))
+ = (sin(x)*cos(x) + i*sinh(y)*cosh(y)/(cos(x)^2 + sinh(y)^2). */
+ __sincosf (__real__ x, &sinrx, &cosrx);
- if (den == 0.0)
+ if (fabsf (__imag__ x) > t)
{
- __complex__ float ez = __cexpf (1.0i * x);
- __complex__ float emz = __cexpf (-1.0i * x);
+ /* Avoid intermediate overflow when the real part of the
+ result may be subnormal. Ignoring negligible terms, the
+ imaginary part is +/- 1, the real part is
+ sin(x)*cos(x)/sinh(y)^2 = 4*sin(x)*cos(x)/exp(2y). */
+ float exp_2t = __ieee754_expf (2 * t);
- res = (ez - emz) / (ez + emz) * -1.0i;
+ __imag__ res = __copysignf (1.0, __imag__ x);
+ __real__ res = 4 * sinrx * cosrx;
+ __imag__ x = fabsf (__imag__ x);
+ __imag__ x -= t;
+ __real__ res /= exp_2t;
+ if (__imag__ x > t)
+ {
+ /* Underflow (original imaginary part of x has absolute
+ value > 2t). */
+ __real__ res /= exp_2t;
+ }
+ else
+ __real__ res /= __ieee754_expf (2 * __imag__ x);
}
else
{
- __real__ res = sin2rx / den;
- __imag__ res = __ieee754_sinhf (2.0 * __imag__ x) / den;
+ float sinhix = __ieee754_sinhf (__imag__ x);
+ float coshix = __ieee754_coshf (__imag__ x);
+
+ den = cosrx * cosrx + sinhix * sinhix;
+ __real__ res = sinrx * cosrx / den;
+ __imag__ res = sinhix * coshix / den;
}
}