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

[Jan Beulich <jbeulich@xxxxxxxx>]

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@xxxxxxx> 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).

Jan