mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-08 14:20:07 +00:00
Fix pow (qNaN, 0) result with -lieee (bug 20919), remove dead parts of wrappers.
The dbl-64 implementation of __ieee754_pow returns a NaN for pow (qNaN, 0) when it should return 1. Normally this is covered up by the wrappers ending up calling __kernel_standard which fixes up the result for this case, but for -lieee the wrappers are bypassed and the bad result gets through as a return value. Now, the wrappers fixing this are dealing with variant error handling that wants a result of NaN for pow (qNaN, 0), and only ever call __kernel_standard for this case if NaN resulted from __ieee754_pow. This leads to a question of whether the dbl-64 code might be deliberately returning NaN in order to use those code paths. However, I can find no sign that this is deliberate. If it were deliberate one would expect other implementations to do the same, and would expect the return of NaN to be very old, but it appears it came in by accident when the present e_pow.c implementation replaced an fdlibm implementation in 2001. So it appears to be unintended that this path through the pow wrapper could be used at all. So this patch fixes the implementation to return 1 in this case as expected. This is consistent with all the other implementations. The relevant path through the wrappers is now unreachable, so is removed (which is the main motivation of this patch: to avoid that path becoming accidentally reachable when implementing TS 18661-1 semantics that pow (sNaN, 0) should return qNaN with "invalid" raised). Another path that would require __ieee754_pow (0, 0) to return 0 is also unreachable (as all implementations return 1, in accordance with C99 semantics), so is removed as well. Note: we don't have anything set up to test -lieee, which in any case is obsolescent (at some point we should remove the ability for new programs to access _LIB_VERSION or define matherr and have it called by glibc). So testing will be implicit through sNaN tests added when making sNaN inputs work correctly for pow functions. Tested for x86_64 and x86. [BZ #20919] * sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return NaN first argument when raised to power 0. * math/w_pow.c (__pow): Do not check for NaN or zero results from raising to power zero. * math/w_powf.c (__powf): Likewise. * math/w_powl.c (__powl): Likewise. * sysdeps/ieee754/k_standard.c (__kernel_standard): Do not handle pow (0, 0) or pow (NaN, 0).
This commit is contained in:
Joseph Myers
parent
84aa75162c
commit
72d839a42f
12
ChangeLog
12
ChangeLog
@ -1,3 +1,15 @@
|
||||
2016-12-02 Joseph Myers <joseph@codesourcery.com>
|
||||
|
||||
[BZ #20919]
|
||||
* sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Do not return
|
||||
NaN first argument when raised to power 0.
|
||||
* math/w_pow.c (__pow): Do not check for NaN or zero results from
|
||||
raising to power zero.
|
||||
* math/w_powf.c (__powf): Likewise.
|
||||
* math/w_powl.c (__powl): Likewise.
|
||||
* sysdeps/ieee754/k_standard.c (__kernel_standard): Do not handle
|
||||
pow (0, 0) or pow (NaN, 0).
|
||||
|
||||
2016-12-02 Carlos O'Donell <carlos@redhat.com>
|
||||
|
||||
[BZ #20918]
|
||||
|
||||
24
math/w_pow.c
24
math/w_pow.c
@ -29,13 +29,7 @@ __pow (double x, double y)
|
||||
{
|
||||
if (_LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (isnan (x))
|
||||
{
|
||||
if (y == 0.0)
|
||||
/* pow(NaN,0.0) */
|
||||
return __kernel_standard (x, y, 42);
|
||||
}
|
||||
else if (isfinite (x) && isfinite (y))
|
||||
if (isfinite (x) && isfinite (y))
|
||||
{
|
||||
if (isnan (z))
|
||||
/* pow neg**non-int */
|
||||
@ -55,19 +49,11 @@ __pow (double x, double y)
|
||||
}
|
||||
}
|
||||
}
|
||||
else if (__builtin_expect (z == 0.0, 0) && isfinite (x) && isfinite (y)
|
||||
else if (__builtin_expect (z == 0.0, 0)
|
||||
&& isfinite (x) && x != 0 && isfinite (y)
|
||||
&& _LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (x == 0.0)
|
||||
{
|
||||
if (y == 0.0)
|
||||
/* pow(0.0,0.0) */
|
||||
return __kernel_standard (x, y, 20);
|
||||
}
|
||||
else
|
||||
/* pow underflow */
|
||||
return __kernel_standard (x, y, 22);
|
||||
}
|
||||
/* pow underflow */
|
||||
return __kernel_standard (x, y, 22);
|
||||
|
||||
return z;
|
||||
}
|
||||
|
||||
@ -29,13 +29,7 @@ __powf (float x, float y)
|
||||
{
|
||||
if (_LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (isnan (x))
|
||||
{
|
||||
if (y == 0.0f)
|
||||
/* pow(NaN,0.0) */
|
||||
return __kernel_standard_f (x, y, 142);
|
||||
}
|
||||
else if (isfinite (x) && isfinite (y))
|
||||
if (isfinite (x) && isfinite (y))
|
||||
{
|
||||
if (isnan (z))
|
||||
/* pow neg**non-int */
|
||||
@ -55,19 +49,11 @@ __powf (float x, float y)
|
||||
}
|
||||
}
|
||||
}
|
||||
else if (__builtin_expect (z == 0.0f, 0) && isfinite (x) && isfinite (y)
|
||||
else if (__builtin_expect (z == 0.0f, 0)
|
||||
&& isfinite (x) && x != 0 && isfinite (y)
|
||||
&& _LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (x == 0.0f)
|
||||
{
|
||||
if (y == 0.0f)
|
||||
/* pow(0.0,0.0) */
|
||||
return __kernel_standard_f (x, y, 120);
|
||||
}
|
||||
else
|
||||
/* pow underflow */
|
||||
return __kernel_standard_f (x, y, 122);
|
||||
}
|
||||
/* pow underflow */
|
||||
return __kernel_standard_f (x, y, 122);
|
||||
|
||||
return z;
|
||||
}
|
||||
|
||||
@ -29,13 +29,7 @@ __powl (long double x, long double y)
|
||||
{
|
||||
if (_LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (isnan (x))
|
||||
{
|
||||
if (y == 0.0L)
|
||||
/* pow(NaN,0.0) */
|
||||
return __kernel_standard_l (x, y, 242);
|
||||
}
|
||||
else if (isfinite (x) && isfinite (y))
|
||||
if (isfinite (x) && isfinite (y))
|
||||
{
|
||||
if (isnan (z))
|
||||
/* pow neg**non-int */
|
||||
@ -55,19 +49,11 @@ __powl (long double x, long double y)
|
||||
}
|
||||
}
|
||||
}
|
||||
else if (__builtin_expect (z == 0.0L, 0) && isfinite (x) && isfinite (y)
|
||||
else if (__builtin_expect (z == 0.0L, 0)
|
||||
&& isfinite (x) && x != 0 && isfinite (y)
|
||||
&& _LIB_VERSION != _IEEE_)
|
||||
{
|
||||
if (x == 0.0L)
|
||||
{
|
||||
if (y == 0.0L)
|
||||
/* pow(0.0,0.0) */
|
||||
return __kernel_standard_l (x, y, 220);
|
||||
}
|
||||
else
|
||||
/* pow underflow */
|
||||
return __kernel_standard_l (x, y, 222);
|
||||
}
|
||||
/* pow underflow */
|
||||
return __kernel_standard_l (x, y, 222);
|
||||
|
||||
return z;
|
||||
}
|
||||
|
||||
@ -73,7 +73,8 @@ __ieee754_pow (double x, double y)
|
||||
{ /* of y */
|
||||
qx = u.i[HIGH_HALF] & 0x7fffffff;
|
||||
/* Is x a NaN? */
|
||||
if (((qx == 0x7ff00000) && (u.i[LOW_HALF] != 0)) || (qx > 0x7ff00000))
|
||||
if ((((qx == 0x7ff00000) && (u.i[LOW_HALF] != 0)) || (qx > 0x7ff00000))
|
||||
&& y != 0)
|
||||
return x;
|
||||
if (y == 1.0)
|
||||
return x;
|
||||
|
||||
@ -60,7 +60,6 @@ static double zero = 0.0; /* used as const */
|
||||
* 17-- log(x<0)
|
||||
* 18-- log10(0)
|
||||
* 19-- log10(x<0)
|
||||
* 20-- pow(0.0,0.0)
|
||||
* 21-- pow(x,y) overflow
|
||||
* 22-- pow(x,y) underflow
|
||||
* 23-- pow(0,negative)
|
||||
@ -82,7 +81,6 @@ static double zero = 0.0; /* used as const */
|
||||
* 39-- yn(x>X_TLOSS, n)
|
||||
* 40-- tgamma(finite) overflow
|
||||
* 41-- tgamma(-integer)
|
||||
* 42-- pow(NaN,0.0)
|
||||
* 43-- +0**neg
|
||||
* 44-- exp2 overflow
|
||||
* 45-- exp2 underflow
|
||||
@ -461,20 +459,6 @@ __kernel_standard(double x, double y, int type)
|
||||
__set_errno (EDOM);
|
||||
}
|
||||
break;
|
||||
case 20:
|
||||
case 120:
|
||||
case 220:
|
||||
/* pow(0.0,0.0) */
|
||||
/* error only if _LIB_VERSION == _SVID_ */
|
||||
exc.type = DOMAIN;
|
||||
exc.name = CSTR ("pow");
|
||||
exc.retval = zero;
|
||||
if (_LIB_VERSION != _SVID_) exc.retval = 1.0;
|
||||
else if (!matherr(&exc)) {
|
||||
(void) WRITE2("pow(0,0): DOMAIN error\n", 23);
|
||||
__set_errno (EDOM);
|
||||
}
|
||||
break;
|
||||
case 21:
|
||||
case 121:
|
||||
case 221:
|
||||
@ -845,20 +829,6 @@ __kernel_standard(double x, double y, int type)
|
||||
__set_errno (EDOM);
|
||||
}
|
||||
break;
|
||||
case 42:
|
||||
case 142:
|
||||
case 242:
|
||||
/* pow(NaN,0.0) */
|
||||
/* error only if _LIB_VERSION == _SVID_ & _XOPEN_ */
|
||||
exc.type = DOMAIN;
|
||||
exc.name = CSTR ("pow");
|
||||
exc.retval = x;
|
||||
if (_LIB_VERSION == _IEEE_ ||
|
||||
_LIB_VERSION == _POSIX_) exc.retval = 1.0;
|
||||
else if (!matherr(&exc)) {
|
||||
__set_errno (EDOM);
|
||||
}
|
||||
break;
|
||||
|
||||
case 44:
|
||||
case 144:
|
||||
|
||||
Loading…
Reference in New Issue
Block a user