Makefile.target: include top level build dir in vpath

Using ccache with CCACHE_BASEDIR set to $(SRC_PATH) or a parent will
rewrite all absolute paths to relative paths. This interacts poorly with
QEMU's two-level build directory scheme. For example, lets say
BUILD_DIR=$(SRC_PATH)/build so build/blockdev.d will contain:

  blockdev.o: ../blockdev.c ../include/sysemu/block-backend.h \

Now the target build under build/x86_64-softmmu or similar will depend
on ../blockdev.o which in turn will get make to source ../blockdev.d to
check its dependencies. Since make always considers paths relative to
the current working directory rather than the makefile the path appeared
in the relative path to ../blockdev.c is useless.

This change simply adds the top level build directory to vpath so paths
relative to the source directory, top build directory, and target build
directory all work just fine.
---
 Makefile.target | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On 09/08/2015 09:02, Michael Marineau wrote:
> Using ccache with CCACHE_BASEDIR set to $(SRC_PATH) or a parent will
> rewrite all absolute paths to relative paths. This interacts poorly with
> QEMU's two-level build directory scheme. For example, lets say
> BUILD_DIR=$(SRC_PATH)/build so build/blockdev.d will contain:
> 
>   blockdev.o: ../blockdev.c ../include/sysemu/block-backend.h \
> 
> Now the target build under build/x86_64-softmmu or similar will depend
> on ../blockdev.o which in turn will get make to source ../blockdev.d to
> check its dependencies. Since make always considers paths relative to
> the current working directory rather than the makefile the path appeared
> in the relative path to ../blockdev.c is useless.
> 
> This change simply adds the top level build directory to vpath so paths
> relative to the source directory, top build directory, and target build
> directory all work just fine.
> ---
>  Makefile.target | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile.target b/Makefile.target
> index 3e7aafd..dc32294 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -7,7 +7,7 @@ include config-target.mak
>  include config-devices.mak
>  include $(SRC_PATH)/rules.mak
>  
> -$(call set-vpath, $(SRC_PATH))
> +$(call set-vpath, $(SRC_PATH):$(BUILD_DIR))
>  ifdef CONFIG_LINUX
>  QEMU_CFLAGS += -I../linux-headers
>  endif
> 

Hi,

can you reply with "Signed-off-by: Michael Marineau
<michael.marineau@coreos.com>", representing that you've read and agreed
to the Developer Certificate of Origin (http://developercertificate.org/)?

This is necessary to include your patch in QEMU.

Paolo

On Aug 12, 2015 6:32 AM, "Paolo Bonzini" <pbonzini@redhat.com> wrote:
>
>
>
> On 09/08/2015 09:02, Michael Marineau wrote:
> > Using ccache with CCACHE_BASEDIR set to $(SRC_PATH) or a parent will
> > rewrite all absolute paths to relative paths. This interacts poorly with
> > QEMU's two-level build directory scheme. For example, lets say
> > BUILD_DIR=$(SRC_PATH)/build so build/blockdev.d will contain:
> >
> >   blockdev.o: ../blockdev.c ../include/sysemu/block-backend.h \
> >
> > Now the target build under build/x86_64-softmmu or similar will depend
> > on ../blockdev.o which in turn will get make to source ../blockdev.d to
> > check its dependencies. Since make always considers paths relative to
> > the current working directory rather than the makefile the path appeared
> > in the relative path to ../blockdev.c is useless.
> >
> > This change simply adds the top level build directory to vpath so paths
> > relative to the source directory, top build directory, and target build
> > directory all work just fine.
> > ---
> >  Makefile.target | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Makefile.target b/Makefile.target
> > index 3e7aafd..dc32294 100644
> > --- a/Makefile.target
> > +++ b/Makefile.target
> > @@ -7,7 +7,7 @@ include config-target.mak
> >  include config-devices.mak
> >  include $(SRC_PATH)/rules.mak
> >
> > -$(call set-vpath, $(SRC_PATH))
> > +$(call set-vpath, $(SRC_PATH):$(BUILD_DIR))
> >  ifdef CONFIG_LINUX
> >  QEMU_CFLAGS += -I../linux-headers
> >  endif
> >
>
> Hi,
>
> can you reply with "Signed-off-by: Michael Marineau
> <michael.marineau@coreos.com>", representing that you've read and agreed
> to the Developer Certificate of Origin (http://developercertificate.org/)?
>
> This is necessary to include your patch in QEMU.
>
> Paolo

Oops, forgot about that.

Signed-off-by: Michael Marineau
<michael.marineau@coreos.com>