[M3devel] m3override

[Olaf Wagner]

I wouldn't worry much about the warning Jay removed.
It only said that an override wasn't used, which is the default
behaviour of cm3 (without -x or -override option). One could argue
that if one wanted this warning, one should use an option like
-warn=overrides or -warn=all (which don't actually exist (yet)).

However, I'd still like others to think about the two perspectives
one can take here, and what should be the direction we are tweaking
our build system.

Traditionally, the focus was on the package view, i.e. the view of
one developer, and not a whole system. The builder was designed to
work well in this setup (more or less). For one notable exception,
which others have noticed (who were involved with the original design):
linking has never been tried implement portably in a general way.
With this focus, overrides are the sole responsibility of the
developer, and one could argue that he should know exactly what
he does if he uses them.

In the CM3 distribution, I used the override feature to allow
building the whole set of package in the workspace, which can be
seen equivalent to use a completely different package pool.
The scripts (which originally were only meant as a tool for the
distribution maintainer) distinguish between build(local) and
buildglobal (or buildship). In the first case, the global package
store isn't involved at all.

Jay has suggested to optimize towards building the whole distribution,
but I'm not sure yet if that's the correct direction. Obviously,
we need to support both perspectives. Much of the charm of the
M3 build system for large projects is based on the way the work
of the single developers can be split up and isolated. And in large
projects there are of course more developers than build or release
engineers. But then, there seems to have been no real use of CM3 for this
kind of development for many years; most (all?) active users seem to
work on their projects alone. So perhaps Jay is right after all?

Olaf
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