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Fix clog10 (-0 +/- 0i) (bug 16362).

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This patch fixes the imaginary part of clog10 (-0 +/- 0i), which
should be +/-pi / log(10) by analogy with clog (the functions were
wrongly returning a result with imaginary part +/-pi, same as for
clog, and the tests matched the incorrect result, though both
functions and tests were correct for the similar case of clog10 (-inf
+/- 0i)).  Tested x86_64 and x86.

	[BZ #16362]
	* math/s_clog10.c (M_PI_LOG10E): New macro.
	(__clog10): Use M_PI_LOG10E instead of M_PI when real and
	imaginary parts are 0.
	* math/s_clog10f.c (M_PI_LOG10Ef): New macro.
	(__clog10f): Use M_PI_LOG10Ef instead of M_PI when real and
	imaginary parts are 0.
	* math/s_clog10l.c (M_PI_LOG10El): New macro.
	(__clog10l): Use M_PI_LOG10El instead of M_PIl when real and
	imaginary parts are 0.
	* math/libm-test.inc (clog10_test_data): Update expected results
	for when real and imaginary parts are 0.
This commit is contained in:
Joseph Myers
2014-03-28 20:53:32 +00:00
parent 277ae3f186
commit 289e077957
6 changed files with 34 additions and 10 deletions
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5
math/s_clog10.c
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@ -25,6 +25,9 @@
/* log_10 (2). */
#define M_LOG10_2 0.3010299956639811952137388947244930267682
/* pi * log10 (e). */
#define M_PI_LOG10E 1.364376353841841347485783625431355770210
__complex__ double
__clog10 (__complex__ double x)
{
@ -35,7 +38,7 @@ __clog10 (__complex__ double x)
if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
{
/* Real and imaginary part are 0.0. */
__imag__ result = signbit (__real__ x) ? M_PI : 0.0;
__imag__ result = signbit (__real__ x) ? M_PI_LOG10E : 0.0;
__imag__ result = __copysign (__imag__ result, __imag__ x);
/* Yes, the following line raises an exception. */
__real__ result = -1.0 / fabs (__real__ x);