Re: Clang and DragonFlyBSD

[Juan Francisco Cantero Hurtado <iam@xxxxxxxxxxxx>]

On 10/14/2011 05:33 AM, Sascha Wildner wrote:
> On Fri, 14 Oct 2011 05:05:41 +0200, Juan Francisco Cantero Hurtado
> <iam@juanfra.info> wrote:
>
> > Hi. I remember in the past someone tried compile DragonFlyBSD with
> > clang and corrected various warnings and errors. I don't know if
> > this person continues with this "project" but I think no. Also a
> > few days ago I found this old page in the wiki
> > http://www.dragonflybsd.org/docs/developer/clang/ .
>
> Alex Hornung and I did some clang work in the past.
>
> Yeah, the wiki page is old and not up-to-date.
>
> > DragonFlyBSD works very good with GCC but also clang is very good
> > reporting errors or inconsistencies in the code. This week I've
> > found a intermediate solution for to have the best of both worlds
> > without extra work.
> >
> > In the "tools" directory of clang exists a tool for generate the
> > same reports of clang but without using clang for compile.
> > scan-build is a (perl) wrapper for gcc and generates html reports
> > with the warnings and errors of clang, but stills compiling the
> > code with gcc (or other compiler).
> > http://clang-analyzer.llvm.org/scan-build.html .
> >
> > I think this tool is perfect for complement the daily snapshots
> > build. The developers don't need work with two compilers different
> > and they can look just the results in the server. scan-build
> > generates static html files, so you can copy the directory with
> > the results to http://mirror-master.dragonflybsd.org/snapshots/ .
> >
> > Example: # cd /usr/src # scan-build make nativekernel
>
> I've done many a scan-build on both our world and our kernel in the
> past and fixed things.
>
> The thing with scan-build is that you'll have to wade through all
> the HTML to find the few issues that are actually _worth_ fixing.

But you also need browse for all files affected if compile with clang.
The same problem. Choose your poison :)

> Not everything it reports is something we want to fix (for various
> reasons), some categories are more interesting than others, and some
> are simply false positive, etc.

Sure.

> I wouldn't want to run it daily as part of the snapshot build
> though, as it takes a lot of time.

Yes, scan-build is very slow. nativekernel took me hours in my netbook.
My point is if the daily build include scan-build, the developers don't
need spend time in to compile with clang or the very big extra time in
scan-build.

I'm curious about how long takes the "scan-build make buildworld" in a
good computer :P

> My overall experience is that people will be enthusiastic to get
> such reports when you ask, but if you put them up, everyone quickly
> goes on to do other things after viewing the first three reports or
> so, because it really takes time to review. The issues worth fixing
> are not delivered on a silver plate unfortunately. :)
>
> > This command generates the binaries with gcc but create a directory
> > with the reports in /tmp:
> > http://juanfra.info/bugs-y-listas/clang-dragonflybsd-201110/dragonflybsd-scan-build-2011-10-13-2.tar.xz
> >
> >
> >
> > (download, decompress and open the index.html file)
> >
> > The clang version in pkgsrc doesn't install scan-build. I've
> > reported the problem to the maintainer. Anyway, exists a temporary
> > solution for this problem:
>
> I usually take clang's trunk which should build fine on dfly (though
> I haven't tried lately) and copy the scan-build stuff to
> /usr/local/bin.
>
> > - Install clang from pkgsrc. - Download the latest build for OSX
> > of scan-build from http://clang-analyzer.llvm.org/installation.html
> > . - Console: # tar -xjf checker-257.tar.bz2 # cd checker-257 # rm
> > -Rf bin # (with this scan-build will use the clang in PATH) #
> > export PATH=$PATH:`pwd` # cd /usr/src # scan-build make
> > buildkernel
> >
> > Let me know if you have any question. Cheers :)


--
Juan Francisco Cantero Hurtado http://juanfra.info