Re: [PATCH] libxl: avoid golang building without CONFIG_GOLANG=y

From: Wei Liu <wl@xen.org>
To: Jan Beulich <jbeulich@suse.com>
Cc: Wei Liu <wl@xen.org>, Ian Jackson <ian.jackson@eu.citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Nick Rosbrook <rosbrookn@gmail.com>,
	Anthony Perard <anthony.perard@citrix.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] libxl: avoid golang building without CONFIG_GOLANG=y
Date: Tue, 4 Aug 2020 15:57:07 +0000	[thread overview]
Message-ID: <20200804155707.rrtzkksrle2nojbj@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <12790d2b-020d-b6fe-4924-2233a4e93d83@suse.com>

On Tue, Aug 04, 2020 at 05:53:49PM +0200, Jan Beulich wrote:
> On 04.08.2020 17:50, Wei Liu wrote:
> > On Tue, Aug 04, 2020 at 05:30:40PM +0200, Jan Beulich wrote:
> >> On 04.08.2020 17:22, Nick Rosbrook wrote:
> >>> On Tue, Aug 4, 2020 at 10:17 AM Wei Liu <wl@xen.org> wrote:
> >>>>
> >>>> On Mon, Aug 03, 2020 at 10:06:32AM +0200, Jan Beulich wrote:
> >>>>> While this doesn't address the real problem I've run into (attempting to
> >>>>> update r/o source files), not recursing into tools/golang/xenlight/ is
> >>>>> enough to fix the build for me for the moment. I don't currently see why
> >>>>> 60db5da62ac0 ("libxl: Generate golang bindings in libxl Makefile") found
> >>>>> it necessary to invoke this build step unconditionally.
> >>>>>
> >>>>
> >>>> Perhaps an oversight?
> >>>
> >>> This is intentional, and I think the commit message in 60db5da62ac0
> >>> ("libxl: Generate golang bindings in libxl Makefile") explains the
> >>> reasoning well. But, to summarize, CONFIG_GOLANG is only used to
> >>> control the bindings actually being compiled (i.e. with `go build`).
> >>> However, we always want the code generation script
> >>> (tools/golang/xenlight/gengotypes.py) to run if e.g.
> >>> tools/libxl/libxl_types.idl is modified.
> >>>
> >>> I hope this helps.
> >>
> >> Not really - I'm still not seeing the "why" behind this behavior. I.e.
> >> why build _anything_ that's not used further in the build, nor getting
> >> installed? Also if (aiui) you effectively object to the change that
> >> Wei has given his ack for, would you mind providing an alternative fix
> >> for the problem at hand?
> > 
> > Is the solution here to make the target check if IDL definition file is
> > actually changed before regenerating the bindings?
> 
> I don't know - Nick? A move-if-changed based approach would likely deal
> with the r/o source problem at the same time (at least until such time
> where the directory containing the file(s) is also r/o).

To make sure Nick and I understand your use case correct -- "r/o source
problem" means you want the tools source to be read-only? But you would
be fine recursing into tools directory to build all the libraries and
programs?

Wei.

> 
> Jan