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Re: [PATCH][BZ #22244] Fix yn(n,0) without SVID wrapper
- From: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Cc: nd at arm dot com
- Date: Tue, 03 Oct 2017 18:43:07 +0100
- Subject: Re: [PATCH][BZ #22244] Fix yn(n,0) without SVID wrapper
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On 03/10/17 18:34, Szabolcs Nagy wrote:
> On 03/10/17 18:28, Szabolcs Nagy wrote:
>> Without SVID compat wrapper yn(n,0) and ynf(n,0) does not raise
>> the divide-by-zero excpetion and it may return inf with the wrong
>> sign for n < 0.
>>
>> 2017-10-03 Szabolcs Nagy <szabolcs.nagy@arm.com>
>>
>> [BZ #22244]
>> * sysdeps/ieee754/dbl-64/e_jn.c (__ieee754_yn): Fix x == 0 case.
>> * sysdeps/ieee754/flt-32/e_jnf.c (__ieee754_ynf): Likewise.
>>
>
> sorry, wrong patch (this one breaks yn(n,-0))
>
now with fixed patch.
diff --git a/sysdeps/ieee754/dbl-64/e_jn.c b/sysdeps/ieee754/dbl-64/e_jn.c
index 3ac91df2b0..a244df0e0a 100644
--- a/sysdeps/ieee754/dbl-64/e_jn.c
+++ b/sysdeps/ieee754/dbl-64/e_jn.c
@@ -268,11 +268,6 @@ __ieee754_yn (int n, double x)
/* if Y(n,NaN) is NaN */
if (__glibc_unlikely ((ix | ((uint32_t) (lx | -lx)) >> 31) > 0x7ff00000))
return x + x;
- if (__glibc_unlikely ((ix | lx) == 0))
- return -HUGE_VAL + x;
- /* -inf and overflow exception. */;
- if (__glibc_unlikely (hx < 0))
- return zero / (zero * x);
sign = 1;
if (n < 0)
{
@@ -281,6 +276,11 @@ __ieee754_yn (int n, double x)
}
if (n == 0)
return (__ieee754_y0 (x));
+ if (__glibc_unlikely ((ix | lx) == 0))
+ return -sign / zero;
+ /* -inf and overflow exception. */;
+ if (__glibc_unlikely (hx < 0))
+ return zero / (zero * x);
{
SET_RESTORE_ROUND (FE_TONEAREST);
if (n == 1)
diff --git a/sysdeps/ieee754/flt-32/e_jnf.c b/sysdeps/ieee754/flt-32/e_jnf.c
index 82b9ba3300..4b78ecea6c 100644
--- a/sysdeps/ieee754/flt-32/e_jnf.c
+++ b/sysdeps/ieee754/flt-32/e_jnf.c
@@ -194,15 +194,15 @@ __ieee754_ynf(int n, float x)
ix = 0x7fffffff&hx;
/* if Y(n,NaN) is NaN */
if(__builtin_expect(ix>0x7f800000, 0)) return x+x;
- if(__builtin_expect(ix==0, 0))
- return -HUGE_VALF+x; /* -inf and overflow exception. */
- if(__builtin_expect(hx<0, 0)) return zero/(zero*x);
sign = 1;
if(n<0){
n = -n;
sign = 1 - ((n&1)<<1);
}
if(n==0) return(__ieee754_y0f(x));
+ if(__builtin_expect(ix==0, 0))
+ return -sign/zero;
+ if(__builtin_expect(hx<0, 0)) return zero/(zero*x);
SET_RESTORE_ROUNDF (FE_TONEAREST);
if(n==1) {
ret = sign*__ieee754_y1f(x);