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From: "Simon 'corecode' Schubert" <corecode at fs.ei.tum.de>
Subject: Re: Hammer on snapshot cd's
Date: Wed, 16 Jul 2008 09:41:20 +0100
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References: <4879c78a$0$849$415eb37d at crater_reader.dragonflybsd.org> <4879D274.6070203 at fs.ei.tum.de> <487bb62c$0$851$415eb37d at crater_reader.dragonflybsd.org> <200807142043.m6EKh2no098817 at apollo.backplane.com> <487cd572$0$852$415eb37d at crater_reader.dragonflybsd.org> <200807151759.m6FHxuUa007901 at apollo.backplane.com> <487CEDA2.30803 at fs.ei.tum.de> <20080715202234.GA25251 at quark.hightek.org> <200807152140.m6FLegnR010083 at apollo.backplane.com> <487D344A.3080605 at fs.ei.tum.de> <200807160123.m6G1NP3a0117
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Matthew Dillon wrote:
> :>     cc -Wall x.c -c -O2
> :>     x.c: In function 'fubar2':
> :>     x.c:16: warning: 'error' is used uninitialized in this function
> :> 
> :>     (edit so *valuep is set to 0)
> :> 
> :>     cc -Wall x.c -c -O2
> :>     (no warning reported)
> :
> :So you need to go -O2?  -O alone doesn't work?  Maybe we should -O2 
> :after the release then :)
> :
> :cheers
> :   simon
> 
>     No, we will always stick to -O.  GCC is a moving target too, even if
>     -O2 works now there is a high chance it will break something in future
>     GCC rolls.

Why should -O2 break things and -O never break things?  That doesn't 
seem obvious to me.  I think all the breakages that happened in the last 
couple of years which were connected with optimization happened with -O, 
-O2 and -Os.

There seems to be a traditional, irrational fear of -O2 in the FreeBSD 
community, which I can't explain.  I've heard something about -O2 and 
inline assembly, but that's probably old as well.

Basically *all* linux distros I've seen (and OSX, for that matter, and 
pkgsrc(!)) use -O2 by default, so if gcc's -O2 was broken, it would be 
discovered fast (and we would be suffering anyways due to pkgsrc).

cheers
   simon