Re: [XEN PATCH v6 12/31] build: use subdir-y in test/Makefile

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Jul 13, 2021 at 09:41:03AM +0200, Jan Beulich wrote:
> On 12.07.2021 17:22, Anthony PERARD wrote:
> > On Wed, Jul 07, 2021 at 05:26:13PM +0200, Jan Beulich wrote:
> >> On 01.07.2021 16:09, Anthony PERARD wrote:
> >>> --- a/xen/test/Makefile
> >>> +++ b/xen/test/Makefile
> >>> @@ -4,15 +4,10 @@ tests all: build
> >>>  
> >>>  ifneq ($(XEN_TARGET_ARCH),x86_32)
> >>>  # Xen 32-bit x86 hypervisor no longer supported, so has no test 
> >>> livepatches
> >>> -SUBDIRS += livepatch
> >>> +subdir-y += livepatch
> >>>  endif
> >>
> >> As per xen/Rules.mk having
> >>
> >> subdir-y := $(subdir-y) $(filter %/, $(obj-y))
> >> obj-y    := $(patsubst %/, %/built_in.o, $(obj-y))
> >> ...
> >> subdir-obj-y := $(filter %/built_in.o, $(obj-y))
> >>
> >> this will result in building of livepatch/built_in.o afaict. Is
> >> this an intended but benign side effect?
> > 
> > Actually, nothing in Rules.mk is using $(subdir-y) other than updating
> > it with possible subdir from $(obj-y).
> > Recursion into a subdir only happen if it is listed in $(obj-y) and thus
> > should be part of a built_in.o. Rules.mk doesn't have a mean to recurs
> > otherwise.
> > 
> > So nothing is actually going to try to build livepatch/build_in.o due to
> > $(subdir-y).
> 
> Question then is: Isn't this actually a bug?

No, "obj-y += livepatch/" need to be used instead, to build 
"livepatch/built_in.o".
Because "$(obj-y)" are objects to be included in a "built_in.o".

-- 
Anthony PERARD