Date: Mon, 23 Jul 2018 14:59:28 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Bruce Evans <brde@optusnet.com.au> Cc: enh via freebsd-numerics <freebsd-numerics@freebsd.org> Subject: Re: fmod nan_mix usage Message-ID: <20180723215928.GA98418@troutmask.apl.washington.edu> In-Reply-To: <20180724071036.O868@besplex.bde.org> References: <CAJgzZopb_0fxM9jbVjUEZ0JPOfcrgeQo_Ki-afZ5aRNr38tKVg@mail.gmail.com> <20180723193418.GA66380@troutmask.apl.washington.edu> <20180724071036.O868@besplex.bde.org>
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On Tue, Jul 24, 2018 at 07:41:17AM +1000, Bruce Evans wrote: > On Mon, 23 Jul 2018, Steve Kargl wrote: > > > > Can you share the code for the relevant tests? > > This simple program gives the expected results > > on amd64. > > > > #include <math.h> > > #include <stdio.h> > > > > int > > main(void) > > { > > printf("%e %d\n", fmodf(3.f, 0.f), isnan(fmodf(3.f, 0.f))); > > printf("%le %d\n", fmod(3.0, 0.0), isnan(fmod(3.0, 0.0))); > > printf("%Le %d\n", fmodl(3.L, 0.L), isnan(fmodl(3.L, 0.L))); > > return 0; > > } > > > > % cc -o z -O a.c -lm && ./z > > nan 1 > > nan 1 > > nan 1 > > clang normally evaluates this at compile, so it doesn't test the libary. > This is arguably a bug in clang, since it doesn't set the exception flags. > #pragma FENV_ACCESS should control this, but it is hard to use and rarely > works. > > The test data needs to be non-literal and perhaps even volatile to prevent > the compiler evaluating it at compile time. > Whoops. I should know better! I have -fno-builtins hardcoded in my development trees and completely forgot about constant folding. -- Steve
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