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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 04.08.2020 17:57, Wei Liu wrote:
> 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@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).
> 
> 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?

Yes - until we support out-of-tree builds, nothing more can be expected
to work.

Jan