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

[Jan Beulich <jbeulich@xxxxxxxx>]

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.

Jan