[kvm-unit-tests PATCH] build: retain intermediate .aux.o targets

[Thomas Huth]

On 26/07/2024 06.15, Nicholas Piggin wrote:
> On Fri Jun 14, 2024 at 6:38 PM AEST, Nicholas Piggin wrote:
>> On Fri Jun 14, 2024 at 11:08 AM AEST, Segher Boessenkool wrote:
>>> On Fri, Jun 14, 2024 at 10:43:39AM +1000, Nicholas Piggin wrote:
>>>> On Wed Jun 12, 2024 at 6:28 PM AEST, Segher Boessenkool wrote:
>>>>> On Wed, Jun 12, 2024 at 02:42:32PM +1000, Nicholas Piggin wrote:
>>>>>> arm, powerpc, riscv, build .aux.o targets with implicit pattern rules
>>>>>> in dependency chains that cause them to be made as intermediate files,
>>>>>> which get removed when make finishes. This results in unnecessary
>>>>>> partial rebuilds. If make is run again, this time the .aux.o targets
>>>>>> are not intermediate, possibly due to being made via different
>>>>>> dependencies.
>>>>>>
>>>>>> Adding .aux.o files to .PRECIOUS prevents them being removed and solves
>>>>>> the rebuild problem.
>>>>>>
>>>>>> s390x does not have the problem because .SECONDARY prevents dependancies
>>>>>> from being built as intermediate. However the same change is made for
>>>>>> s390x, for consistency.
>>>>>
>>>>> This is exactly what .SECONDARY is for, as its documentation says,
>>>>> even.  Wouldn't it be better to just add a .SECONDARY to the other
>>>>> targets as well?
>>>>
>>>> Yeah we were debating that and agreed .PRECIOUS may not be the
>>>> cleanest fix but since we already use that it's okay for a
>>>> minimal fix.
>>>
>>> But why add it to s390x then?  It is not a fix there at all!
>>
>> Eh, not a big deal. I mentioned that in the changelog it doesn't seem to
>> pracicaly fix something. And I rather the makefiles converge as much as
>> possible rather than diverge more.
>>
>> .SECONDARY was added independently and not to fix this problem in
>> s390x. And s390x has .SECONDARY slightly wrong AFAIKS. It mentions
>> .SECONDARY: twice in a way that looks like it was meant to depend on
>> specific targets, it actually gives it no dependencies and the
>> resulting semantics are that all intermediate files in the build are
>> treated as secondary. So somethig there should be cleaned up. If the
>> .SECONDARY was changed to only depend on the .gobj and .hdr.obj then
>> suddenly that would break .aux.o if I don't make the change.
>>
>> So I'm meaning to work out what to do with all that, i.e., whether to
>> add blanket .SECONDARY for all and trim or remove the .PRECIOUS files,
>> or remove s390x's secondary, or make it more specific, or something
>> else. But it takes a while for me to do makefile work.
> 
> Hi Thomas,
> 
> Ping on this patch?

I assumed that Marc would chime in on the s390x part here?

  Thomas