Re: [PATCH v3 1/8] xen: fix build when $(obj-y) consists of just blanks

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Thu, Dec 10, 2020 at 11:21:53AM +0100, Jan Beulich wrote:
> On 09.12.2020 18:40, Anthony PERARD wrote:
> > How about using $(XEN_CFLAGS) instead of $(c_flags)? That should prevent
> > CC from generating the .*.o.d files while keeping the relevant flags.
> 
> What does "relevant" cover? For an empty .o it may not be important
> right now, but I could see
> 
> c_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_CFLAGS) '-D__OBJECT_FILE__="$@"'
> a_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_AFLAGS)
> 
> include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
> 
> c_flags += $(CFLAGS-y)
> a_flags += $(CFLAGS-y) $(AFLAGS-y)
> 
> leading to CFLAGS-y / AFLAGS-y which need to be consistent across
> _all_ object files (e.g. some recording of ABI used).
> 
> > Do we need to worry about having a object file been listed twice?
> > Wouldn't that be a mistake?
> 
> No. The list approach (obj-$(CONFIG_xyz) += ...) easily allows for
> this to happen. See xen/arch/x86/mm/Makefile for an existing example.


Sounds good,
Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

Thanks,

-- 
Anthony PERARD