Re: Default NO_CLEAN=yes in 15+

On Tue, 23 Jul 2024 17:29:12 -0400
John Baldwin <jhb@FreeBSD.org> wrote:

> On 7/23/24 16:08, Shawn Webb wrote:
> > On Tue, Jul 23, 2024 at 03:58:13PM -0400, John Baldwin wrote:
> >> The buildworld and buildkernel targets include a "clean" step before building
> >> objects dating back before my time to 'make world' (I haven't looked to see
> >> how far back it goes).  To permit incremental builds, this step can be skipped
> >> via NO_CLEAN=yes.  This step is a bit unusual in build systems however.  Most
> >> build systems have separate commands for building vs cleaning (e.g. 'make all'
> >> vs 'make clean') and over time FreeBSD's build system has gained dedicated
> >> clean targets as well (cleanworld and cleankernel).  For myself, I always
> >> use NO_CLEAN=yes when building worlds and kernels.  If I need a clean build
> >> I use the dedicated clean targets (e.g. cleanworld) first.  In particular,
> >> cleanworld/cleankernel are far more efficient since they use a single
> >> recursive 'rm' whereas the "clean" step involves a full tree walk with
> >> nested make invocations of the 'cleandir' target.
> >>
> >> A few years ago, Ed Maste added a MK_CLEAN option to src.opts.mk to as a
> >> WITH/WITHOUT knob for the "clean" step similar to NO_CLEAN=yes.  To preserve
> >> existing behavior this knob currently defaults to on, but I know Ed's goal
> >> was to eventually flip the default so that NO_CLEAN builds would be the
> >> default.  I would like us to do that starting in 15.
> > 
> > It would make sense to me to default MK_CLEAN=no in release branches.
> > Perhaps stable branches, too. While I don't hold a strong opinion on
> > the matter, I would prefer MK_CLEAN=yes to remain the default on the
> > main branch.
> > 
> > I can't give tangible examples, but I remember running into weird
> > issues occasionally when using `make buildworld WITHOUT_CLEAN=yes` in
> > main. I probably should do a better job at documenting those
> > (infrequent) issues when they arise.
> 
> To be clear, the suggestion is that when you hit an issue, just run
> 'make cleanworld' rather than relying on the omission of NO_CLEAN=yes
> to do this for you (and much slower at that).  Have you used any other
> build systems where 'make' does an implicit 'make clean' before it
> builds?  I have never encountered another where this is true.  'clean' is
> always a separate target from 'all' in my experience.
> 
> -- 
> John Baldwin

+1.

And IIRC, *.meta remains after cleanworld / cleankernel on META_MODE
builds.
If I'm correct, it should be properly cleaned, too.

-- 
Tomoaki AOKI    <junchoon@dec.sakura.ne.jp>