Re: [XEN PATCH v5 04/16] xen/build: have the root Makefile generates the CFLAGS

From: Julien Grall <julien@xen.org>
To: Anthony PERARD <anthony.perard@citrix.com>,
	xen-devel@lists.xenproject.org
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Daniel De Graaf" <dgdegra@tycho.nsa.gov>,
	"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [XEN PATCH v5 04/16] xen/build: have the root Makefile generates the CFLAGS
Date: Fri, 24 Apr 2020 10:26:23 +0100	[thread overview]
Message-ID: <01254b5c-7383-1b3c-53ce-8683e61549c1@xen.org> (raw)
In-Reply-To: <20200421161208.2429539-5-anthony.perard@citrix.com>

Hi Anthony,

On 21/04/2020 17:11, Anthony PERARD wrote:
> Instead of generating the CFLAGS in Rules.mk everytime we enter a new
> subdirectory, we are going to generate most of them a single time, and
> export the result in the environment so that Rules.mk can use it.  The
> only flags left to be generated are the ones that depend on the
> targets, but the variable $(c_flags) takes care of that.
> 
> Arch specific CFLAGS are generated by a new file "arch/*/arch.mk"
> which is included by the root Makefile.
> 
> We export the *FLAGS via the environment variables XEN_*FLAGS because
> Rules.mk still includes Config.mk and would add duplicated flags to
> CFLAGS.
> 
> When running Rules.mk in the root directory (xen/), the variable
> `root-make-done' is set, so `need-config' will remain undef and so the
> root Makefile will not generate the cflags again.
> 
> We can't use CFLAGS in subdirectories to add flags to particular
> targets, instead start to use CFLAGS-y. Idem for AFLAGS.
> So there are two different CFLAGS-y, the one in xen/Makefile (and
> arch.mk), and the one in subdirs that Rules.mk is going to use.
> We can't add to XEN_CFLAGS because it is exported, so making change to
> it might be propagated to subdirectory which isn't intended.
> 
> Some style change are introduced in this patch:
>      when LDFLAGS_DIRECT is included in LDFLAGS
>      use of CFLAGS-$(CONFIG_INDIRECT_THUNK) instead of ifeq().
> 
> The LTO change hasn't been tested properly, as LTO is marked as
> broken.
> 
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>

For the Arm bits:

Acked-by: Julien Grall <jgrall@amazon.com>

Cheers,

-- 
Julien Grall