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Date:      Tue, 28 Aug 2012 11:00:59 -0700
From:      Mehmet Erol Sanliturk <m.e.sanliturk@gmail.com>
To:        David Wolfskill <david@catwhisker.org>
Cc:        Jamie Paul Griffin <jamie@kode5.net>, freebsd-stable@freebsd.org
Subject:   Re: Building the kernel and userland with llvm/clang
Message-ID:  <CAOgwaMtYPDCrVh3QJxOefMGohH5=rETOP0P%2BYUXJSsS%2BwMBDQA@mail.gmail.com>
In-Reply-To: <20120828171311.GL10869@albert.catwhisker.org>
References:  <20120828153203.GC38854@kontrol.kode5.net> <20120828154621.GJ10869@albert.catwhisker.org> <20120828165315.GE38854@kontrol.kode5.net> <20120828171311.GL10869@albert.catwhisker.org>

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On Tue, Aug 28, 2012 at 10:13 AM, David Wolfskill <david@catwhisker.org>wrote:

> On Tue, Aug 28, 2012 at 05:53:15PM +0100, Jamie Paul Griffin wrote:
> > ...
> > Thanks David, that's helpful information.
>
> Good; that was the intent. :-)
>
> > I'll likely give it a go. So does clang create better binaries and
> libraries, in terms of performance and such-like? I'm currently reading as
> much as I can find about clang and its associated tools; however, compilers
> are quite complex software and learning about them is, for me at least, a
> lot to take in.
> > ....
>
> I don't know that it creates "better" code, but I believe that at least
> some of its error/warning checking may be a bit better: it certainly
> whines about a fair bit of GNUish code, citing (e.g.) "Tautological
> compares" ... and that sort of thing seems as if it's something I'd want
> to know about if it were my code, so I could fix it.
>
> From the time (a few weeks) when I was building stable/9 with both gcc &
> clang (on different slices, sources updated to the same GRN), I got the
> impression that clang was slower (to compile) than gcc was.
>
> I note that I've had no issues at all with interoperation of executables
> & libraries built with gcc & clang.  I consider this a Good Thing.  :-)
>
> As I understand the issues, FreeBSD uses a (somewhat modified) version
> of the last GPLv2-licensed version of gcc, and there is strong incentive
> to avoid "tainting" FreeBSD with a GPLv3-licensed version of gcc.
>
> Thus, if we want to be able to move forward with our "system compiler,"
> we have little choice but to use something other than gcc.  clang
> appears to work, so I plan to exercise it & report issues if I encounter
> them.
>
> Peace,
> david
> --
> David H. Wolfskill                              david@catwhisker.org
> Depriving a girl or boy of an opportunity for education is evil.
>
> See http://www.catwhisker.org/~david/publickey.gpg for my public key.
>



With respect to messages from FreeBSD mailing lists , my understanding
about GPL issue is as follows  :


The GPL v3 has severe restrictions about use of its licensed software ,
especially Libraries .
Some commercial companies supporting FreeBSD are using FreeBSD in their
proprietary products . The GPL v3 is forcing them to legally in a difficult
position .  Their rescue from this legal threat is to remove GPL parts from
the FreeBSD .


The reason of switching to a permissive licensed compiler such as
clang/LLVM is that .
And reason to stay GPL v2 gcc compiler is that . This gcc compiler blocking
is NOT permitting
to follow new processor developments .


Thank you very much .


Mehmet Erol Sanliturk



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