Re: [XEN PATCH v5 09/16] xen/build: use if_changed on built_in.o

[Jan Beulich <jbeulich@xxxxxxxx>]

On 01.05.2020 16:42, Anthony PERARD wrote:
> On Tue, Apr 28, 2020 at 03:48:13PM +0200, Jan Beulich wrote:
>> On 21.04.2020 18:12, Anthony PERARD wrote:
>>> In the case where $(obj-y) is empty, we also replace $(c_flags) by
>>> $(XEN_CFLAGS) to avoid generating an .%.d dependency file. This avoid
>>> make trying to include %.h file in the ld command if $(obj-y) isn't
>>> empty anymore on a second run.
>>>
>>> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
>>
>> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> Personally I'd prefer ...
>>
>>> --- a/xen/Rules.mk
>>> +++ b/xen/Rules.mk
>>> @@ -130,15 +130,24 @@ include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
>>>  c_flags += $(CFLAGS-y)
>>>  a_flags += $(CFLAGS-y) $(AFLAGS-y)
>>>  
>>> -built_in.o: $(obj-y) $(extra-y)
>>> -ifeq ($(obj-y),)
>>> -   $(CC) $(c_flags) -c -x c /dev/null -o $@
>>> -else
>>> +quiet_cmd_ld_builtin = LD      $@
>>>  ifeq ($(CONFIG_LTO),y)
>>> -   $(LD_LTO) -r -o $@ $(filter-out $(extra-y),$^)
>>> +cmd_ld_builtin = \
>>> +    $(LD_LTO) -r -o $@ $(filter-out $(extra-y),$(real-prereqs))
>>>  else
>>> -   $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
>>> +cmd_ld_builtin = \
>>> +    $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out $(extra-y),$(real-prereqs))
>>>  endif
>>> +
>>> +quiet_cmd_cc_builtin = LD      $@
>>> +cmd_cc_builtin = \
>>> +    $(CC) $(XEN_CFLAGS) -c -x c /dev/null -o $@
>>> +
>>> +built_in.o: $(obj-y) $(extra-y) FORCE
>>> +ifeq ($(obj-y),)
>>> +   $(call if_changed,cc_builtin)
>>> +else
>>> +   $(call if_changed,ld_builtin)
>>>  endif
>>
>> ...
>>
>>    $(call if_changed,$(if $(obj-y),ld,cc)_builtin)
>>
>> but perhaps I'm the only one.
> 
> I think so. Spelling the full name of the command makes it easier to
> look for where it is used, or for where it is defined.

   $(call if_changed,$(if $(obj-y),ld_builtin,cc_builtin))

then?

Jan