Re: [gentoo-dev] Automatically replace -mtune= with -mcpu= if not supported by gcc?!

[Paul de Vrieze <pauldv@gentoo.org>]

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On Sunday 17 April 2005 15:50, Philipp Hasse wrote:
> Hi,
>
> I recently noticed that portage executes the file bashrc located in
> /etc/portage before every ebuild.
> This way it can be used to set the -mcpu and -mtune flags correctly.
> If you add the following to this file everything goes automatically:
>
> <--- SNIP --->
> # Automatically replace -mtune= with -mcpu if not supported by gcc
> # and vice versa.
> echo "" | gcc -mtune=i386 -E - > /dev/null 2> /dev/null
> if [ $? == 0 ]; then
> export CFLAGS=`echo $CFLAGS | /bin/sed 's/-mcpu=/-mtune=/'`
> export CXXFLAGS=`echo $CXXFLAGS | /bin/sed 's/-mcpu=/-mtune=/'`
> else
> export CFLAGS=`echo $CFLAGS | /bin/sed 's/-mtune=/-mcpu=/'`
> export CXXFLAGS=`echo $CXXFLAGS | /bin/sed 's/-mtune=/-mcpu=/'`
> fi
> <--- SNIP --->
>
> Maybe someone can give me a feedback if this is good idea or if I missed
> something for some exotic situation this will fail.
>
> Why doesn't portage do this automatically by itself? If it encounters an
> -mtune´= option in make.conf and gcc doesn't support it it replaces it
> with -mcpu=?!

It actually does (or did) the -mcpu to -mtune for newer gcc versions. This 
creates all kinds of havoc if you want to compile a 3.3 gcc by a 3.4 gcc 
(this works when not specifying -mcpu). It is so agressive that if you do try 
to reverse this in your bashrc, it gets reversed again to -mtune. As it's 
only necessary for compiling \<gcc-3.3 I just let it strip out -mtune 
completely.

Paul

-- 
Paul de Vrieze
Gentoo Developer
Mail: pauldv@gentoo.org
Homepage: http://www.devrieze.net

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