Re: [gentoo-dev] [RFC] CFLAGS paragraph for the GWN

[Lionel Bouton <lionel-dev@bouton.name>]

Ciaran McCreesh wrote the following on 03.10.2006 14:26 :
> On Tue, 03 Oct 2006 02:56:42 +0200 Lionel Bouton
> <lionel-dev@bouton.name> wrote:
> | Being able to tune the CFLAGS is part of one of the core principles of
> | Gentoo: let the user be in control.
>
> What? No it isn't.
>   

Maybe it depends on what you mean by 'in control'. What I mean is that
you have a good stable base from which to work on, but nothing prevents
you to tweak things like you want: Gentoo doesn't get in your way.
http://www.gentoo.org/main/en/about.xml mentions "Extreme
Configurabiliy" and the main picture states "Larry the Cow was in
control. And he liked it.".

> | <li>nss_ldap stopped working with <c>-ffast-math</c> (reported to
> | break many packages changing with the actual gcc version)</li>
>
> Uh, -ffast-math has never been and will never be a safe thing to stick
> in CFLAGS.
>   

I agree (how could I say otherwise after spending several days with a
hole in my foot finally finding that I had a gun named fast-math in my
hand :-) ).
Apparently many developpers think that it might be in CFLAGS though (see
the amount of 'filter-flags -ffast-math' in ebuilds) so a reminder might
not be wasted for some users.

>
> | Users with unsupported CFLAGS (see the <uri
> | link='http://gentoo-wiki.com/CFLAGS_matrix'>CFLAGS matrix</uri> for
> | example) might want to return to safe CFLAGS (see <uri
> | link='http://gentoo-wiki.com/Safe_Cflags'>Safe CFLAGS</uri>) if recent
> | updates caused them stability problems. On the other hand, more
> | adventurous users might want to experiment with CFLAGS that didn't
> | work properly with gcc-3.4.6... As always, the user is in control.
>
> Linking to that is a very bad idea. The wiki is in control of the
> minority ricer fringe.
>
>   

Ok. Anyway I'm now convinced that a dev-proofed version of its content
in the GWN would be far better.

> GWN shouldn't be advocating this kind of thing at all. Here's a better
> paragraph:
>
> <p>We would like to remind you that using anything beyond -O2
> -fomit-frame-pointer -march/-mcpu/-mtune in CFLAGS or CXXLFAGS (and
> -mieee, -mabi etc on selected archs that tell you to do this), and using
> anything at all in LDFLAGS or ASFLAGS, is pointless and will lead to a
> broken system. Your penis length is not proportional to the size of your
> CFLAGS.</p>
>
>   

Hum, I'll leave out the last sentence or rephrase it... I'd prefer to be
more soft-spoken: pointless might be a little too much too. Let's say
that the cost-risk/benefit ratio is not worth it for the vast majority
of users. CFLAGS tuning should probably only be used by people with very
specific needs (gcc devs/testers, HPTC people with extensive
knowledge/experience of the problems involved). For LDFLAGS and ASFLAGS
I'll take your word for it (I never even tried modifying them myself).

Lionel.
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