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Keith Packard via Newlib 1f8e5847df libm: Fix 'gamma' and 'gammaf' functions. Clean up other gamma code. [v2]
The current gamma, gamma_r, gammaf and gammaf_r functions return
|gamma(x)| instead of ln(|gamma(x)|) due to a change made back in 2002
to the __ieee754_gamma_r implementation. This patch fixes that, making
all of these functions map too their lgamma equivalents.

To fix the underlying bug, the __ieee754_gamma functions have been
changed to return gamma(x), removing the _r variants as those are no
longer necessary. Their names have been changed to __ieee754_tgamma to
avoid potential confusion from users.

Now that the __ieee754_tgamma functions return the correctly signed
value, the tgamma functions have been modified to use them.

libm.a now exposes the following gamma functions:

    ln(|gamma(x)|):

	__ieee754_lgamma_r
	__ieee754_lgammaf_r

	lgamma
	lgamma_r
	gamma
	gamma_r

	lgammaf
	lgammaf_r
	gammaf
	gammaf_r

	lgammal	(on machines where long double is double)

    gamma(x):

	__ieee754_tgamma
	__ieee754_tgammaf
	tgamma
	tgammaf
	tgammal (on machines where long double is double)

Additional aliases for any of the above functions can be added if
necessary; in particular, I'm not sure if we need to include
__ieee754_gamma*_r functions (which would return ln(|(gamma(x)|).

Signed-off-by: Keith Packard <keithp@keithp.com>

----

v2:
	Switch commit message to ASCII
2020-09-04 21:27:11 +02:00

34 lines
803 B
C

/* @(#)wr_gamma.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
* wrapper double gamma_r(double x, int *signgamp)
*/
#include "fdlibm.h"
#include <errno.h>
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
double gamma_r(double x, int *signgamp) /* wrapper lgamma_r */
#else
double gamma_r(x,signgamp) /* wrapper lgamma_r */
double x; int *signgamp;
#endif
{
return lgamma_r(x, signgamp);
}
#endif /* defined(_DOUBLE_IS_32BITS) */