Date: Thu, 22 Mar 2001 03:50:04 -0800 (PST) From: Peter Pentchev <roam@orbitel.bg> To: freebsd-ports@FreeBSD.org Subject: Re: ports/25750: rrdtool port fails to build with -ffast-math -mfancy-math-387 Message-ID: <200103221150.f2MBo3740764@freefall.freebsd.org>
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The following reply was made to PR ports/25750; it has been noted by GNATS.
From: Peter Pentchev <roam@orbitel.bg>
To: khera@kciLink.com
Cc: FreeBSD-gnats-submit@freebsd.org
Subject: Re: ports/25750: rrdtool port fails to build with -ffast-math -mfancy-math-387
Date: Thu, 22 Mar 2001 13:48:02 +0200
From the gcc infopage (Invoking GCC >> Optimize options):
`-ffast-math'
This option allows GCC to violate some ANSI or IEEE rules and/or
specifications in the interest of optimizing code for speed. For
example, it allows the compiler to assume arguments to the `sqrt'
function are non-negative numbers and that no floating-point values
are NaNs.
This option should never be turned on by any `-O' option since it
can result in incorrect output for programs which depend on an
exact implementation of IEEE or ANSI rules/specifications for math
functions.
So.. if you're turning on -ffast-math, you should know what you are doing;
in particular, you should know you are breaking IEEE rules :)
Maybe the rrdtool port Makefile should check for -ffast-math in CFLAGS,
and warn the user / cancel the build / just remove it?
G'luck,
Peter
--
I had to translate this sentence into English because I could not read the original Sanskrit.
On Mon, Mar 12, 2001 at 04:04:01PM -0500, khera@kciLink.com wrote:
>
> >Number: 25750
> >Category: ports
> >Synopsis: ports/net/rrdtool fails to build with CC hardware math options
> >Originator: Vivek Khera
> >Release: FreeBSD 4.3-BETA i386
> >Organization:
> >Environment:
> System: FreeBSD onceler.kciLink.com 4.3-BETA FreeBSD 4.3-BETA #1: Wed Mar 7 13:44:04 EST 2001 khera@yertle.kciLink.com:/u/yertle2/usr.obj/amd/onceler/u/onceler1/usr/src/sys/ONCELER i386
>
> ports cvsup'd today; world from march 7.
>
> >Description:
>
>
> in /etc/make.conf, I have
> CFLAGS+= -ffast-math -mfancy-math-387
>
> which apparently causes IEEE math to fail in GCC, leading to my problem:
>
> rrdtool dies during its self config at build time. When it croaks, it
> spits out the entire config.log making it hard to see the real
> error... this is what you get if you can scroll back a bazillion lines:
>
> checking if IEEE math works with the -OPT:IEEE_comparisons=ON switch... no
> checking if IEEE math works with fpsetmask(0)... not isnan(NaN) ... no
> checking if IEEE math works with signal(SIGFPE,SIG_IGN)... not isnan(NaN) ... no
> configure: error:
> Your Compiler does not do propper IEEE math ... Please find out how to
> make IEEE math work with your compiler and let me know (oetiker@ee.ethz.ch).
> Check config.log to see what went wrong ...
>
> >How-To-Repeat:
> cd /usr/ports/net/rrdtool
> make
>
> >Fix:
>
> don't specify -ffast-math -mfancy-math-387 to the compiler.
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