[Bug libstdc++/63500] [4.9/5 Regression] bug in debug version of std::make_move_iterator?

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63500

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fdumont at gcc dot gnu.org

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
François, is there a quick fix for this?
>From gcc-bugs-return-463706-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Oct 09 19:01:49 2014
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From: "sgk at troutmask dot apl.washington.edu" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug libquadmath/63488] large errors in y0q
Date: Thu, 09 Oct 2014 19:01:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc488

--- Comment #8 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Thu, Oct 09, 2014 at 06:27:08PM +0000, zimmerma+gcc at loria dot fr wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?idc488
>
> --- Comment #7 from Paul Zimmermann <zimmerma+gcc at loria dot fr> ---
> I agree that near zeroes we can expect large errors. However for
> other functions I got only small errors in ulps, maybe I was unlucky.
> Also the ultimate goal is to get correct rounding, even near zeroes.
>

I suspect you got lucky :-)  IIRC my testing correctly,
exhaustive testing of values in each interval shows
lgammaf(x) for x < 0 and not an integer also has major
accuracy issues:

Interval:                     Max ULP     Value
[-1.10000e+01, -1.00000e+01): 6.72889 -1.0000009e+01
[-1.00000e+01, -9.00000e+00): 83.4928 -9.0000029e+00
[-9.00000e+00, -8.00000e+00): 24615.2 -8.0000248e+00
[-8.00000e+00, -7.00000e+00): 22575.7 -7.9999752e+00
[-7.00000e+00, -6.00000e+00): 100393. -6.0013852e+00
[-6.00000e+00, -5.00000e+00): 36966.5 -5.0082183e+00
[-5.00000e+00, -4.00000e+00): 324309. -4.0393620e+00
[-4.00000e+00, -3.00000e+00): 2981098 -3.1435809e+00
[-3.00000e+00, -2.00000e+00): 7497618 -2.4570248e+00
[-2.00000e+00, -1.00000e+00): 4.18718 -1.7313151e+00
[-1.00000e+00, -4.76837e-07): 3.46651 -3.5002786e-01

troutmask:fvwm:kargl[209] ./testf -a -3.1435809e+00
libm: -2.38418579e-07, 1
mpfr: -1.96054615e-07, 1

The relevant code in testf is (RND is round-to-nearest).

            x = (float)strtof(optarg, NULL);
            y = lgammaf_r(x,&s);
            mpfr_inits2(DBL_MANT_DIG, t1, t2, NULL);
            mpfr_set_d(t1, (double)x, RND);
            mpfr_lgamma(t2, &si, t1, RND);
            printf("libm: %.8e, %d\n", y, s);
            mpfr_printf("mpfr: %.8Re, %d\n", t2, si);
            mpfr_clears(t1, t2, NULL);