Re: [Qemu-devel] [PATCH 1/2] Makefile: Remove BUILD_DIR from qapi-dir

[Stefan Hajnoczi <stefanha@gmail.com>]

On Tue, Jun 12, 2012 at 3:14 PM, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> On Tue, Jun 12, 2012 at 10:49:57AM +0100, Stefan Hajnoczi wrote:
>> On Sat, Jun 09, 2012 at 09:08:38AM +0200, Stefan Weil wrote:
>> > qapi-dir does not need an absolute path. All other build directories
>> > are relative. When BUILD_DIR is removed, the build output looks better
>> > (no long lines with absolute paths when everything else uses short
>> > lines):
>> >
>> >   GEN   qapi-generated/qga-qapi-types.c
>> >   CC    qapi-generated/qga-qapi-types.o
>> >   GEN   qapi-generated/qga-qapi-visit.c
>> >   CC    qapi-generated/qga-qapi-visit.o
>> >   GEN   qapi-generated/qga-qmp-marshal.c
>> >   CC    qapi-generated/qga-qmp-marshal.o
>> >
>> > Using a relative path also avoids potential problems when BUILD_DIR
>> > includes blanks.
>> >
>> > Signed-off-by: Stefan Weil <sw@weilnetz.de>
>> > ---
>> >  Makefile |    2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> I merged this but have CCed Michael Roth to take a look.  qemu.git
>> contains an earlier commit to explicitly add $(BUILD_DIR):
>>
>> commit 9b129408589b2ed7bb2cdea03d2aba46a5fd74d4
>> Author: Michael Roth <mdroth@linux.vnet.ibm.com>
>> Date:   Tue Nov 29 16:47:49 2011 -0600
>>
>>     Makefile: use full path for qapi-generated directory
>>
>>     Generally $(BUILD_DIR) == $(CURDIR), but that isn't necessarilly the
>>     case, so use $(BUILD_DIR)/qapi-generated for generated files to
>>     avoid potentionally sticking generating files in odd places outside
>>     the build's include paths.
>>
>>     Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
>>
>> Does this rationale still apply?  Is it really a good ideal to remove
>> $(BUILD_DIR)?
>
> Here's some context for the patch:
>
> http://lists.gnu.org/archive/html/qemu-devel/2011-11/msg03474.html
>
> Originally a change was made to add a $(SRC_DIR) prefix to fix a build.
> This triggered an unrelated bug, and was not quite correct. I submitted
> a patch to fix the bug it triggered, and then a patch that used
> $(BUILD_DIR) instead.
>
> I'm not sure the latter was ever needed however, it looks like it was
> just the classic issue of someone having a dirty $(SRC_DIR) and
> subsequently switching to out of tree builds. I think the original issue
> was simple a stale qapi-generated/ directory sitting in $(SRC_DIR) that
> was taking precedence over the one being created in $(BUILD_DIR)
>
> So, while having the $(BUILD_DIR) prefix does make the build safer in
> this regard, I think it addresses a use-case that was never supported to
> begin with. So I'd be fine with applying Stefan's patch if it makes
> things cleaner/more consistent with everything else.

Thanks for explaining.  I will include Stefan Weil's patch.

Stefan