Re: [XEN PATCH 12/15] build: avoid Config.mk's CFLAGS

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.05.2023 18:38, Anthony PERARD wrote:
> The variable $(CFLAGS) is too often set in the environment,
> especially when building a package for a distribution. Often, those
> CFLAGS are intended to be use to build user spaces binaries, not a
> kernel. This mean packager needs to takes extra steps to build Xen by
> overriding the CFLAGS provided by the package build environment.
> 
> With this patch, we avoid using the variable $(CFLAGS). Also, the
> hypervisor's build system have complete control over which CFLAGS are
> used.

"..., apart from $(EXTRA_CFLAGS_XEN_CORE)", as you say ...

> No change intended to XEN_CFLAGS used, beside some flags which may be
> in a different order on the command line.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> ---
> 
> Notes:
>     There's still $(EXTRA_CFLAGS_XEN_CORE) which allows to add more CFLAGS
>     if someone building Xen needs to add more CFLAGS to the hypervisor
>     build.

... only here.

> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -259,7 +259,16 @@ export KBUILD_DEFCONFIG := $(ARCH)_defconfig
>  export XEN_TREEWIDE_CFLAGS := $(CFLAGS)
>  
>  XEN_AFLAGS =
> -XEN_CFLAGS = $(CFLAGS)
> +XEN_CFLAGS =
> +ifeq ($(XEN_OS),SunOS)
> +    XEN_CFLAGS +=  -Wa,--divide -D_POSIX_C_SOURCE=200112L -D__EXTENSIONS__

So this (and the arch.mk additions) duplicate stuff we have in config/*.mk.
Such duplication isn't really nice. Setting AS, CC, etc also happens there,
and hence I expect you're going to duplicate that as well in a later patch.
Can't we massage (if necessary) the config/*.mk relevant to the hypervisor
build, so they can be included from xen/Makefile? That way all such basic
settings could remain in a central place, which has been well known for
many years.

Jan