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Don't let tgammal() modify signgam. Only lgamma*() should modify it.

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Letting tgammal() modify signgam has two disadvantages:

- It breaks valid code that assumes that the value of signgam is not
  clobbered by calls to tgammal().
- It makes this function depend on the presence of signgam. signgam is
  an X/Open System Interface. It is not part of the C standard.
This commit is contained in:
Ed Schouten 2015-01-08 09:49:31 +01:00
parent 0b2a647742
commit b6cd89849e
2 changed files with 9 additions and 22 deletions
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12
ld128/e_tgammal.c
View file

@ -26,20 +26,14 @@ tgammal(long double x)
int64_t i0,i1; int64_t i0,i1;
GET_LDOUBLE_WORDS64(i0,i1,x); GET_LDOUBLE_WORDS64(i0,i1,x);
if (((i0&0x7fffffffffffffffLL)|i1) == 0) { if (((i0&0x7fffffffffffffffLL)|i1) == 0)
signgam = 0;
return (1.0/x); return (1.0/x);
}
if (i0<0 && (u_int64_t)i0<0xffff000000000000ULL && rintl(x)==x) { if (i0<0 && (u_int64_t)i0<0xffff000000000000ULL && rintl(x)==x)
signgam = 0;
return (x-x)/(x-x); return (x-x)/(x-x);
}
if (i0==0xffff000000000000ULL && i1==0) { if (i0==0xffff000000000000ULL && i1==0)
signgam = 0;
return (x-x); return (x-x);
}
return expl(lgammal(x)); return expl(lgammal(x));
} }

19
ld80/e_tgammal.c
View file

@ -25,7 +25,6 @@
* SYNOPSIS: * SYNOPSIS:
* *
* long double x, y, tgammal(); * long double x, y, tgammal();
* extern int signgam;
* *
* y = tgammal( x ); * y = tgammal( x );
* *
@ -33,10 +32,8 @@
* *
* DESCRIPTION: * DESCRIPTION:
* *
* Returns gamma function of the argument. The result is * Returns gamma function of the argument. The result is correctly
* correctly signed, and the sign (+1 or -1) is also * signed. This variable is also filled in by the logarithmic gamma
* returned in a global (extern) variable named signgam.
* This variable is also filled in by the logarithmic gamma
* function lgamma(). * function lgamma().
* *
* Arguments |x| <= 13 are reduced by recurrence and the function * Arguments |x| <= 13 are reduced by recurrence and the function
@ -61,7 +58,6 @@
#include <openlibm.h> #include <openlibm.h>
#include "math_private.h" #include "math_private.h"
extern int signgam;
/* /*
tgamma(x+2) = tgamma(x+2) P(x)/Q(x) tgamma(x+2) = tgamma(x+2) P(x)/Q(x)
@ -224,7 +220,6 @@ tgammal(long double x)
long double p, q, z; long double p, q, z;
int i; int i;
signgam = 1;
if( isnan(x) ) if( isnan(x) )
return(NAN); return(NAN);
if(x == INFINITY) if(x == INFINITY)
@ -237,6 +232,7 @@ q = fabsl(x);
if( q > 13.0L ) if( q > 13.0L )
{ {
int sign = 1;
if( q > MAXGAML ) if( q > MAXGAML )
goto goverf; goto goverf;
if( x < 0.0L ) if( x < 0.0L )
@ -246,7 +242,7 @@ if( q > 13.0L )
return (x - x) / (x - x); return (x - x) / (x - x);
i = p; i = p;
if( (i & 1) == 0 ) if( (i & 1) == 0 )
signgam = -1; sign = -1;
z = q - p; z = q - p;
if( z > 0.5L ) if( z > 0.5L )
{ {
@ -258,7 +254,7 @@ if( q > 13.0L )
if( z <= PIL/LDBL_MAX ) if( z <= PIL/LDBL_MAX )
{ {
goverf: goverf:
return( signgam * INFINITY); return( sign * INFINITY);
} }
z = PIL/z; z = PIL/z;
} }
@ -266,7 +262,7 @@ goverf:
{ {
z = stirf(x); z = stirf(x);
} }
return( signgam * z ); return( sign * z );
} }
z = 1.0L; z = 1.0L;
@ -298,8 +294,6 @@ x -= 2.0L;
p = __polevll( x, P, 7 ); p = __polevll( x, P, 7 );
q = __polevll( x, Q, 8 ); q = __polevll( x, Q, 8 );
z = z * p / q; z = z * p / q;
if( z < 0 )
signgam = -1;
return z; return z;
small: small:
@ -311,7 +305,6 @@ else
{ {
x = -x; x = -x;
q = z / (x * __polevll( x, SN, 8 )); q = z / (x * __polevll( x, SN, 8 ));
signgam = -1;
} }
else else
q = z / (x * __polevll( x, S, 8 )); q = z / (x * __polevll( x, S, 8 ));