Re: [Xen-devel] [RFC] xen/arm: build: add missed dependency for head.S

[Julien Grall <julien.grall@xxxxxxx>]

(CC Ian)

Hi,

On 03/06/16 11:07, Wei Chen wrote:
> When we update the header files that had been included in head.S.
> The build system would not re-compile the head.S. Because in the
> build rules, the dependencies are setting to .*.d (eg. DEPS = .*.d)
> files in the same folder as Makefile.
>
> But head.S is very special, it was used by the Makefile in the parent
> folder: "ALL_OBJS := $(TARGET_SUBARCH)/head.o".
>
> In this case, the build system could not find the dependency in DEPS.
> When we update the header files, the build system is unware of this
> update. If we re-build the Xen without doing make clean or touching
> the head.S, the build system will not recompile the head.S.
>
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxxxxx>
> ---
> In my mind, the better way to fix this bug is converting the DEPS from
> ALL_OBJS. But I am afraid of the impact. I am not sure whether there
> are some dependencies are not generated from obj files.
My knowledge of the build system is limited. Stefano, Ian, Wei, could 
you give a look?
Regards,

> ---
> xen/Rules.mk          | 3 ++-
>   xen/arch/arm/Makefile | 2 ++
>   2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/xen/Rules.mk b/xen/Rules.mk
> index 961d533..1247b61 100644
> --- a/xen/Rules.mk
> +++ b/xen/Rules.mk
> @@ -92,9 +92,10 @@ LDFLAGS += $(LDFLAGS-y)
>
>   include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
>
> +DEPS = .*.d
> +
>   include Makefile
>
> -DEPS = .*.d
>   define gendep
>       ifneq ($(1),$(subst /,:,$(1)))
>           DEPS += $(dir $(1)).$(notdir $(1)).d
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index af4d0e1..9e38da3 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -51,6 +51,8 @@ endif
>
>   ALL_OBJS := $(TARGET_SUBARCH)/head.o $(ALL_OBJS)
>
> +DEPS += $(TARGET_SUBARCH)/.head.o.d
> +
>   $(TARGET): $(TARGET)-syms $(TARGET).axf
>         $(OBJCOPY) -O binary -S $< $@
>   ifeq ($(CONFIG_ARM_64),y)
--
Julien Grall

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