Date: Wed, 20 Jul 2011 14:34:57 +0200 From: "Julian H. Stacey" <jhs@berklix.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org, hackers@freebsd.org, Dan Nelson <dnelson@allantgroup.com> Subject: Re: Freebsd-7.4 + std gcc 4.2.1 fails to honour -march=i586 Message-ID: <201107201235.p6KCYvmT007475@fire.js.berklix.net> In-Reply-To: Your message "Wed, 20 Jul 2011 07:48:05 EDT." <201107200748.05786.jhb@freebsd.org>
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Hi,
Reference:
> From: John Baldwin <jhb@freebsd.org>
> Date: Wed, 20 Jul 2011 07:48:05 -0400
> Message-id: <201107200748.05786.jhb@freebsd.org>
John Baldwin wrote:
> On Wednesday, July 20, 2011 7:33:26 am Julian H. Stacey wrote:
> > What should FreeBSD do ?
> > Add a comment to man gcc ... that -march=i586 is not
> > enough, & feed the comment back to gcc project & see how
> > they want to handle it ?
>
> No, this is not a GCC bug. If you want to use a single build machine that
> will compile programs for other machines on a network to use, it must use the
> lowest common denominator for its CPUTYPE in /etc/make.conf.
>
> The out-of-the-box crt files from a FreeBSD install will work fine on a 486
> and above, so can only get yourself into this quandry by building a new world
> with a CPUTYPE (or similar CFLAGS) setting in /etc/make.conf that violates
> this rule.
>
> You can fix your machine by fixing the CPUTYPE in your build machine and
> building and installing a new world (do use NO_CLEAN=yes for your build, do a
> full build). You will also want to rebuild any other binaries on this machine
> that you share with other machines.
>
> --
> John Baldwin
Hi John,
Yes I realise all that now thanks.
The point now is man gcc is misleading/ incomplete:
"-march=cpu-type
Generate instructions for the machine type cpu-type."
Those instructions will not make a program that runs on a lesser CPU type
without alternate crt for lesse CPU.
CFLAGS in make.conf is fine for single developer/ host debugging,
but is not appropriate for multi user multi make builds os src/ ports/ other
Its seems just that gcc -march fails to select alternate crt.
One gross ugly solution needing root would be to create chroots,
but Too ugly.
I suggest gcc via -march should also be used as a selection for sub
dirs for crt ? & we should co-operate with gcc project on that,
*BSD & *linux must all face same phenomena so lets not develop
a non standard solution.
Even if we're too lazy to do anything more, we should at least
document it as a patch to man gcc.
Cheers,
Julian
--
Julian Stacey, BSD Unix Linux C Sys Eng Consultants Munich http://berklix.com
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