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

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

[Philipp Hasse]

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=?!

Regards
Philipp Hasse

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

[Mike Frysinger]

On Sunday 17 April 2005 09:50 am, Philipp Hasse wrote:
> This way it can be used to set the -mcpu and -mtune flags correctly.

not worth the added crap imho
-mike
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Re: [gentoo-dev] Automatically replace -mtune= with -mcpu= if not supported by gcc?!

[Alec Warner]

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Mike Frysinger wrote:
> On Sunday 17 April 2005 09:50 am, Philipp Hasse wrote:
> 
>>This way it can be used to set the -mcpu and -mtune flags correctly.
> 
> 
> not worth the added crap imho
> -mike

Better to have it fail and have the users fix their build-env themselves.
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Re: [gentoo-dev] Automatically replace -mtune= with -mcpu= if not supported by gcc?!

[Paul de Vrieze]

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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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