Re: [RFC kvm-unit-tests PATCH] build: fix .aux.o target building

["Marc Hartmayer" <mhartmay@linux.ibm.com>]

On Wed, Jun 05, 2024 at 08:53 PM +1000, "Nicholas Piggin" <npiggin@gmail.com> wrote:
> On Wed Jun 5, 2024 at 8:42 PM AEST, Marc Hartmayer wrote:
>> On Wed, Jun 05, 2024 at 06:16 PM +1000, Nicholas Piggin <npiggin@gmail.com> wrote:
>> > Here's another oddity I ran into with the build system. Try run make
>> > twice. With arm64 and ppc64, the first time it removes some intermediate
>> > files and the second causes another rebuild of several files. After
>> > that it's fine. s390x seems to follow a similar pattern but does not
>> > suffer from the problem. Also, the .PRECIOUS directive is not preventing
>> > them from being deleted inthe first place. So... that probably means I
>> > haven't understood it properly and the fix may not be correct, but it
>> > does appear to DTRT... Anybody with some good Makefile knowledge might
>> > have a better idea.
>> >
>>
>> $ make clean -j &>/dev/null && make -d
>> …
>> Successfully remade target file 'all'.
>> Removing intermediate files...
>> rm powerpc/emulator.aux.o powerpc/tm.aux.o powerpc/spapr_hcall.aux.o powerpc/interrupts.aux.o powerpc/selftest.aux.o powerpc/smp.aux.o powerpc/selftest-migration.aux.o powerpc/spapr_vpa.aux.o powerpc/sprs.aux.o powerpc/rtas.aux.o powerpc/memory-verify.aux.o
>>
>> So an easier fix would be to add %.aux.o to .PRECIOUS (but that’s probably still not clean).
>>
>> .PRECIOUS: %.o %.aux.o
>
> Ah, so %.o does not match %.aux.o. That answers that. Did you see
> why s390x is immune? Maybe it defines the target explicitly somewhere.

Not yet :/ But what was also interesting is that if I’m using multiple
jobs I don’t see the issue.

make clean -j; make -j; make -j # <- the last make has nothing to do

if I’m using:

make clean -j; make; make -j # <- the last make has something to do…
                                  that something that irritates me

>
> Is it better to define explicit targets if we want to keep them, or
> add to .PRECIOUS? Your patch would be simpler.

Normally, I would say without .PRECIOUS it’s cleaner, but there is
already a .PRECIOUS for %.so… So as Andrew has already written

.PRECIOUS: %.so %.aux.o

should also be fine.

>
> Thanks,
> Nick
>
-- 
Kind regards / Beste Grüße
   Marc Hartmayer

IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Wolfgang Wendt
Geschäftsführung: David Faller
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294