Date: Fri, 12 Sep 2014 15:05:44 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: enh <enh@google.com> Cc: freebsd-numerics@freebsd.org Subject: Re: lgamma_r and lgammaf_r return the wrong sign for -0.f Message-ID: <20140912220544.GA96714@troutmask.apl.washington.edu> In-Reply-To: <CAJgzZopa-d=eR7zkqhffsjMY0NEavhqDA-B3V9bQdaJd6BMO2A@mail.gmail.com> References: <CAJgzZopa-d=eR7zkqhffsjMY0NEavhqDA-B3V9bQdaJd6BMO2A@mail.gmail.com>
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On Fri, Sep 12, 2014 at 02:15:37PM -0700, enh via freebsd-numerics wrote: > if I pass -0.f to lgammaf_r, the sign returned in *signgamp is 1. this > is incorrect --- it should be -1. > > both lgamma_r and lgammaf_r are affected, but the other special cases > in those functions look fine to me. > > this is fixed in OpenBSD and glibc, but FreeBSD and NetBSD both have > the same bug. Are you sure FreeBSD has a bug? From n1256.pdf (committee draft of C99) F.9.5.3 The lgamma functions -- lgamma(1) returns +0. -- lgamma(2) returns +0. -- lgamma(x) returns +inf and raises the ``divide-by-zero'' floating-pointr exception for x a negative integer or zero. -- lgamma(-inf) returns +inf. -- lgamma(+inf) returns +inf. See the 3rd bullet. -0 is 0 and -0 is a negative integer. POSIX appears to defer to ISO C. n1570.pdf (committe draft for C11) has (almost?) identical text. > patch below (whitespace mangled courtesy of gmail). i'd prefer to wait > for this to be fixed in FreeBSD and pull down the fix rather than just > fix it locally. I have a bigger patch coming with ld80 and ld128 version of lgammal and lgammal_r. > btw, it looks like you're missing coshl/sinhl/tanhl for ld128 now? > (they've been removed from imprecise.c without having ld128 > implementations added afaics.) The ld80 and ld128 versions are in the same file. troutmask:fvwm:kargl[226] grep LDBL /usr/src/lib/msun/src/e_coshl.c #if LDBL_MAX_EXP != 0x4000 #define BIAS (LDBL_MAX_EXP - 1) #if LDBL_MANT_DIG == 64 #elif LDBL_MANT_DIG == 113 #endif /* LDBL_MANT_DIG == 64 */ GET_LDBL_EXPSIGN(ix,x); if (ix<BIAS-(LDBL_MANT_DIG+1)/2) /* |x| < TINY */ #if LDBL_MANT_DIG == 64 #elif LDBL_MANT_DIG == 113 see also e_sinhl.c and s_tanhl.c. -- Steve
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