Re: [Qemu-devel] [PATCH v3 4/4] configure: Add workaround for ccache and clang

[Peter Maydell]

On 19 March 2015 at 19:01, John Snow <address@hidden> wrote:
> Test if ccache is interfering with our life, and
> disable its habit of trying to compile already pre-processed
> versions of code if so.
>
> In particular, clang has different semantic warnings based on
> if the warning arose from a macro or not. By trying to build
> preprocessed versions of code, we get more errors than we should.
>
> ccache allows us to disable this feature, opting instead to
> compile the original version instead of its preprocessed version.
>
> This makes ccache much slower for cache misses, but at least it
> becomes usable with QEMU/clang.
>
> Thanks to Peter Eisentraut for his writeup on the issue:
> http://peter.eisentraut.org/blog/2014/12/01/ccache-and-clang-part-3/

This is really working around a bug in either ccache or
in the way Fedora has configured ccache, so I kind of
feel it ought to be dealt with there. However I don't
object too much to our including the workaround in our
configure...

-- PMM