Re: [PATCH v4 for-5.0] configure: warn if not using a separate build directory

[BALATON Zoltan]

On Fri, 3 Apr 2020, Eric Blake wrote:
> On 4/3/20 8:53 AM, Daniel P. Berrangé wrote:
> > Running configure directly from the source directory is a build
> > configuration that will go away in future. It is also not currently
> > covered by any automated testing. Display a deprecation warning if
> > the user attempts to use an in-srcdir build setup, so that they are
> > aware that they're building QEMU in an undesirable manner.
> >
> > Reviewed-by: Eric Blake <address@hidden>
> > Reviewed-by: Markus Armbruster <address@hidden>
> > Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> > Tested-by: Philippe Mathieu-Daudé <address@hidden>
> > Signed-off-by: Daniel P. Berrangé <address@hidden>
> > ---
> >
> > Changed in v4:
> >    - Adopted Eric's suggested wording
>
> > +if test "$in_srcdir" = "yes"; then
> > +    echo
> > +    echo "WARNING: SUPPORT FOR BUILDING IN THE SOURCE DIR IS DEPRECATED"
> > +    echo
> > +    echo "Support for running the 'configure' script directly from the"
> > +    echo "source directory is deprecated. In-tree builds are not covered"
> > +    echo "by automated testing and thus may not correctly build QEMU."
> > +    echo "Users are recommended to use a separate build directory:"
> > +    echo
> > +    echo "  $ mkdir build"
> > +    echo "  $ cd build"
> > +    echo "  $ ../configure"
> > +    echo "  $ make"
>
> Late question, but:
>
> Since this is just a warning, we still manage to complete the ./configure 
> run, including whatever generated files it leaves in-tree. Is there any 
> additional step we need to recommend prior to 'mkdir build' that will clean 
> up the in-tree artifacts, so that the user then attempting the VPATH build 
> won't still have a broken build due to the leftovers from the in-tree 
> attempt?  'make distclean', perhaps?
>
> /me starts testing; I'll reply back once it finishes...

You proabably also need make distclean before going to use build dir. 
Since in-tree build continues to work as before and hopefully even after 
it won't some convenience functions will take care of it without the user 
having to do it by hand I wonder if such a long warning is really needed 
in configure now. Other than uselessly annoying users, what does this 
patch achieve? The recommended way to build may change again when build 
system is replaced and I won't change my usual way until it works and 
going to just ignore this warning and I guess others who like in-tree 
builds will do the same. But I've already said that so probably won't 
mention it again.

Regards,
BALATON Zoltan