Date: Sat, 30 Jan 2010 20:11:45 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Bruce Evans <brde@optusnet.com.au> Cc: das@freebsd.org, gavin@freebsd.org, freebsd-standards@freebsd.org, freebsd-amd64@freebsd.org Subject: Re: standards/143358: nearbyint raises spurious inexact exception Message-ID: <20100130181145.GA3877@deviant.kiev.zoral.com.ua> In-Reply-To: <20100131014341.J78095@delplex.bde.org> References: <201001301251.o0UCpSEP077706@freefall.freebsd.org> <20100131014341.J78095@delplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--lWZ9pouYHbrmKLtT Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Jan 31, 2010 at 02:20:30AM +1100, Bruce Evans wrote: > On Sat, 30 Jan 2010 gavin@freebsd.org wrote: >=20 > >Synopsis: nearbyint raises spurious inexact exception >=20 > >Note that a comment in the function itself in lib/msun/src/s_nearbyint.c > >does also suggest that this PR is valid, "We save and restore the > >floating-point environment to avoid raising an inexact exception." I've > >also verified Solaris 10, Linux and FreeBSD 7.2 show the expected=20 > >behaviour. >=20 > This seems to be a bug in gcc-4.2, or perhaps a bug in the inline asms. > gcc-4.2 still works with -O0, but with -O it removes the entire fesetenv() > in nearbyint(). The fegetenv() isn't removed though its result is never > used. I didn't get anywhere good trying to fix this, but I got to the > following worse place of interest: after replacing the fesetenv(&env) by > fesetenv(&xenv) where xenv is an invalidly initialized global variable > (all 0's), the fegetenv(&env) corrupted the current environment (looks > a bit like xenv was used to initialize the current environment). >=20 > Removing fesetenv() in other contexts would give larger bugs. While looking at this, I tried to run the example on custom-build gcc 4.4.3/binutils 2.20 toolchain, and bumped into the issue fixed by http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/3eac7944b4112632ad6= fb257c7ce31deda72d89f --lWZ9pouYHbrmKLtT Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (FreeBSD) iEYEARECAAYFAktkdmAACgkQC3+MBN1Mb4hasgCfZQ3GFXJIWUX++8mi6QjlfaMP czMAoMCz9Zw3TohtRMr8EkYKCpEH6F3J =ZL8P -----END PGP SIGNATURE----- --lWZ9pouYHbrmKLtT--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20100130181145.GA3877>