Re: [XEN PATCH v4 05/18] xen/build: use new $(c_flags) and $(a_flags) instead of $(CFLAGS)

[Jan Beulich <jbeulich@xxxxxxxx>]

On 31.03.2020 12:30, Anthony PERARD wrote:
> In a later patch ("xen/build: have the root Makefile generates the
> CFLAGS), we want to generate the CFLAGS in xen/Makefile, then export
> it and have Rules.mk use a CFLAGS from the environment variables. That
> changes the flavor of the CFLAGS and flags intended for one target
> (like -D__OBJECT_FILE__ and -M%) gets propagated and duplicated. So we
> start by moving such flags out of $(CFLAGS) and into $(c_flags) which
> is to be modified by only Rules.mk.
> 
> __OBJECT_FILE__ is only used by arch/x86/mm/*.c files, so having it in
> $(c_flags) is enough, we don't need it in $(a_flags).
> 
> For include/Makefile and as-insn we can keep using CFLAGS, but since
> it doesn't have -M* flags anymore there is no need to filter them out.
> 
> The XEN_BUILD_EFI tests in arch/x86/Makefile was filtering out
> CFLAGS-y, but according to dd40177c1bc8 ("x86-64/EFI: add CFLAGS to
> check compile"), it was done to filter out -MF. CFLAGS doesn't
> have those flags anymore, so no filtering is needed.
> 
> This is inspired by the way Kbuild generates CFLAGS for each targets.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>