Date: Tue, 23 Jul 2024 20:33:28 +0000 From: Brooks Davis <brooks@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: arch@freebsd.org Subject: Re: Default NO_CLEAN=yes in 15+ Message-ID: <ZqATmFveqAkvs0P4@spindle.one-eyed-alien.net> In-Reply-To: <9bbb12ee-d5e0-4e9c-a832-bbfe5eea0ba6@FreeBSD.org> References: <9bbb12ee-d5e0-4e9c-a832-bbfe5eea0ba6@FreeBSD.org>
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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. +1 We should continue spot cleanups for things like foo.c -> foo.S as required rather than pointlessly rebuilding everything every time. It's much better for a small number of people to spend time tidying things up than to make expensive cleaning the default. > Further off, I would suggest that we remove the "clean" step outright, > perhaps in 16.x. Regardless, we will need to update documentation to > prefer the clean targets over WITH_CLEAN=yes if our docs do not do this > already. I strongly agree. It's all weird and unnecessary with things like git-clean(1) available. Eventually I'd like to get rid of cleandir and its weird behavior differences based on .OBJDIR's existence. This is tooling for the distant past. -- Brooks
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