Re: [PATCH for-4.15] automation/alpine: add g++ to the list of build depends

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 2 Mar 2021, Stefano Stabellini wrote:
> On Tue, 2 Mar 2021, Jan Beulich wrote:
> > On 02.03.2021 10:36, Roger Pau Monné wrote:
> > > On Tue, Mar 02, 2021 at 09:53:41AM +0100, Jan Beulich wrote:
> > >> On 02.03.2021 09:14, Roger Pau Monné wrote:
> > >>> On Mon, Mar 01, 2021 at 06:01:36PM +0000, Andrew Cooper wrote:
> > >>>> On 01/03/2021 17:59, Andrew Cooper wrote:
> > >>>>> On 01/03/2021 09:58, Roger Pau Monne wrote:
> > >>>>>> clang++ relies on the C++ headers installed by g++, or else a clang
> > >>>>>> build will hit the following error:
> > >>>>>>
> > >>>>>> <built-in>:3:10: fatal error: 'cstring' file not found
> > >>>>>> #include "cstring"
> > >>>>>>          ^~~~~~~~~
> > >>>>>> 1 error generated.
> > >>>>>> make[10]: *** [Makefile:120: headers++.chk] Error 1
> > >>>>>>
> > >>>>>> Reported-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > >>>>>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> > >>>>>> ---
> > >>>>>> Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>
> > >>>>>> No real risk here from a release PoV, it's just pulling a package
> > >>>>>> required for the Alpine clang build. Worse that cold happen is that
> > >>>>>> the Alpine clang build broke, but it's already broken.
> > >>>>> Shouldn't this be fixed upstream in Alpine?  Its clearly a packaging 
> > >>>>> bug.
> > >>>>
> > >>>> Or (thinking about it), we've got a build system bug using g++ when it
> > >>>> should be using clang++.
> > >>>
> > >>> No, the check is using clang++, the issue is that clang++ doesn't
> > >>> install the standard c++ headers, and thus trying to use them (cstring
> > >>> in this case) fails. Installing the g++ package solves the issue
> > >>> because it installs the headers.
> > >>
> > >> I have to admit that I consider this odd. The g++ package should
> > >> neither provide nor depend on the headers. It may recommend their
> > >> installation. On my distro (SLES) the headers come from the
> > >> libstdc++-devel package, as I would have expected. There
> > >> additionally is a dependency of libclang5 (no -devel suffix!) on
> > >> libstdc++-devel (I suppose this is an indication that things
> > >> aren't quite right here either; I haven't checked an up-to-date
> > >> version of the distro yet, though).
> > > 
> > > Yes, that was indeed my first attempt as I've tried to install
> > > libstdc++, but there's no -devel counterpart for the package, and it
> > > only installs the libraries but not the headers.
> > > 
> > > Then if I list the contents of the g++ package, I do see:
> > > 
> > > ...
> > > usr/include/c++/10.2.1/cstring
> > > ...
> > > 
> > > And clang++'s include path is:
> > > 
> > > #include <...> search starts here:
> > >  
> > > /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/10.2.1/../../../../include/c++/10.2.1
> > >  
> > > /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/10.2.1/../../../../include/c++/10.2.1/x86_64-alpine-linux-musl
> > >  
> > > /usr/bin/../lib/gcc/x86_64-alpine-linux-musl/10.2.1/../../../../include/c++/10.2.1/backward
> > >  /usr/include
> > >  /usr/lib/clang/10.0.1/include
> > > 
> > > So it does seem clang depends on the gcc c++ headers, I assume this is
> > > done in order to avoid having a duplicate set of c++ headers for clang
> > > and gcc? I really have no idea, but I do think clang package should
> > > depend on g++.
> > 
> > As long as the g++ package is what provides the headers (i.e. if that's
> > their concept), I agree.
> 
> That makes sense to me too.
> 
> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

If nobody speaks up, I'll commit this patch and this patch:

https://marc.info/?l=xen-devel&m=161433737432684

(both of them already acked by Ian and only affecting automation/)
within the next day or two.