Re: [gentoo-dev] Re: Dying on some CFLAGS instead of filtering them.

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

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On Tuesday 11 July 2006 04:32, Ryan Hill wrote:
>  If yes, why ? And what is your better idea ?
>
> I prefer a filter-flags with a ewarn (or elog, haven't read that thread yet
> ;)) message.
>
> * The -ffast-math option is known to break this package and has been
> filtered from your CFLAGS.  Link to Safe CFLAGS wiki page, blah blah blah.
>
> I like this better because it informs me of what I did wrong, what was done
> to correct it, and how I can correct it for myself in the future if I
> choose to.  I don't like artificial barriers and things not working without
> immediate attention.  Call me lazy but it's annoying when you know what
> you're doing yet you have to jump through hoops to get it done.

The die would use the same message. Next, it would actually stop immediately 
instead of letting you continue further and break in the long run. 
Using -ffast-math globally is just broken. In some packages it may work. In 
others it doesn't.

My argument is that we must not filter -ffast-math or any other dangerous 
cflags. The reason being that people will request more filters for all 
packages that don't work with it. Many users will either ignore or miss the 
warning messages. Filtering the flag basically tells them that even though 
the message says it is dangerous, their use of the flag is still more or less 
supported, while it is not.

> Okay, bad joke aside, there are always going to be users who tweak GCC
> flags. This has to be expected, as they're mysterious, and technical, and
> kinda cool. I like the tweaker crowd and I am a dummy, so no offense was
> intended to either groups.  I meant that if you safety-proof a complex
> system, people never learn that they're doing anything wrong in the first
> place.

Exactly, filtering the flags is safety-proofing. So just die, or not filter at 
all.

> Right, but how are people supposed to learn something is dangerous if all
> the sharp edges have been filed off?  And how can you decide which flags
> are "bad" and "good" on a global level when for the most part compiler
> parameters are akin to black magic?

In this case the compiler documentation itself says it is dangerous. That 
should be enough.

Paul

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

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