Re: [kvm-unit-tests PATCH 2/2] powerpc/ppc64: Makefile cleanup

[Thomas Huth <thuth@redhat.com>]

On 10.05.2016 09:44, Laurent Vivier wrote:
> 
> On 10/05/2016 08:35, Andrew Jones wrote:
>> On Tue, May 10, 2016 at 08:19:36AM +0200, Thomas Huth wrote:
>>> On 09.05.2016 16:01, Andrew Jones wrote:
>>>> This does the same cleanup as 'x86: Makefile refine'
>>>>
>>>> Signed-off-by: Andrew Jones <drjones@redhat.com>
>>>> ---
>>>>  powerpc/Makefile.common | 13 ++++---------
>>>>  1 file changed, 4 insertions(+), 9 deletions(-)
>>>>
>>>> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
>>>> index 4449aec616853..60d545c98e38c 100644
>>>> --- a/powerpc/Makefile.common
>>>> +++ b/powerpc/Makefile.common
>>>> @@ -22,6 +22,9 @@ CFLAGS += -I lib -I lib/libfdt
>>>>  CFLAGS += -Wa,-mregnames
>>>>  CFLAGS += -fpie
>>>>  
>>>> +# We want to keep intermediate files: %.elf and %.o
>>>> +.PRECIOUS: %.elf %.o
>>>
>>> If you just want to keep intermediate files, wouldn't it be better to
>>> use .SECONDARY instead of .PRECIOUS? .PRECIOUS seems to contain some
>>> more magic that comes into action when make is killed by a signal... not
>>> sure if we want to have that here?
>>
>> I should extend the commit message to explain that. Wei Yang found
>> (and I confirmed) that .SECONDARY doesn't seem to work[*] - we tried it,
>> but the intermediate files still got removed. We both agree it would be
>> the more appropriate choice though. Did you have better luck with it?

I also only had a look at the info pages of make, to understand what
PRECIOUS is doing (since I didn't know that command yet), and so I
stumbled upon SECONDARY which sounded like a better match.
But I now gave it a try, and it also does not work here.
According to some comments on stackoverlow.com, SECONDARY does not work
with patterns. This is also indirectly documented in the info page of
make. For PRECIOUS, it says:

"You can also list the target pattern of an implicit rule (such as
 `%.o') as a prerequisite file of the special target `.PRECIOUS' to
 preserve intermediate files created by rules whose target patterns
 match that file's name."

But that paragraph is missing for SECONDARY, i.e. indicating that this
does not work there.

> I don't understand why you want to keep intermediate files. If they have
> to be kept, they should be primary targets.
> 
> It seems for, at least ppc64, we don't need the .PRECIOUS.

They could be useful for debugging purposes, e.g. for running "objdump"
on them... ?

Anyway, I think you can at least remove the "%.elf" from the PRECIOUS
line, since the elf files are our primary target on powerpc and thus do
not have to be listed here.

 Thomas