Building the kernel and userland with llvm/clang

Mehmet Erol Sanliturk m.e.sanliturk at
Tue Aug 28 18:01:00 UTC 2012

On Tue, Aug 28, 2012 at 10:13 AM, David Wolfskill <david at>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 at
> Depriving a girl or boy of an opportunity for education is evil.
> See 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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