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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