Re: deprecation of in-tree builds

[BALATON Zoltan]

On Tue, 31 Mar 2020, Markus Armbruster wrote:
> Peter Maydell <address@hidden> writes:
> > On Mon, 30 Mar 2020 at 14:26, Markus Armbruster <address@hidden> wrote:
> > > Peter Maydell <address@hidden> writes:
> > >
> > > > AIUI from Paolo, the intention is to deprecate and eventually
> > > > stop supporting "in-tree" builds, so that the only option is
> > > > building in a separate build directory. I thought we should
> > > > probably mention that in the 5.0 changelog, so I wrote up some
> > > > text:
> > > >
> > > > https://wiki.qemu.org/ChangeLog/5.0#Build_Information
> > >
> > > Overdue.  Thanks for doing this!
> > >
> > > > Suggestions for changes/comments etc welcome.
> > >
> > > Looks fine to me.
> >
> > Consensus in the thread seemed to lean towards having
> > the 'configure/make' runes auto-create a build directory;
> > if we want to do that we should probably not say anything in
> > the release notes, because we'll cause people to change
> > unnecessarily. Or at least have them say "We recommend
> > out-of-tree builds. In future we might make the commands
> > that currently do an in-tree build automatically create
> > and use a build directory for you." rather than a blanket
> > "we're going to drop this and you should change what you
> > do now".
> >
> > Thoughts?
>
> I'm wary of complicating the build system to save developers a minor
> change of habits.

How much complication is it? Looks like a few lines in configure (like the 
one submitted to print warning but instead of printing a long warning just 
run the commands (which is even shorter then the text). Then a Makefile in 
top level dir to do make -C build like someone has also posted in another 
email. This does not seem too much burden to make life of some people 
easier so I don't see why some of you insist to force everyone to change 
their ways even if it could be solved with some effort.

> We will have to ask developers to change habits anyway when we switch to
> Meson.  I agree with Daniel's recommendation to delay changes requiring
> habit-changes until then.  However, telling people to stay clear of the
> unloved and brittle in-tree build is simply good advice we should not
> withhold.

Can someone please explain why is it brittle and cannot be supported? It 
has worked well so far apart from some breakage due to being untested 
which is also not a techincal necessity just a decision by some 
maintiners to not test it. Adding a CI job to keep it working would also 
not be difficult or much complexity.

Regards,
BALATON Zoltan