Re: [Qemu-devel] [Qemu-trivial] [PATCH 2/2] Makefile: use full path for qapi-generated directory

[Anthony Liguori <anthony@codemonkey.ws>]

On 12/01/2011 12:11 PM, Stefan Weil wrote:
> Am 01.12.2011 16:19, schrieb Stefano Stabellini:
>> On Wed, 30 Nov 2011, Stefan Weil wrote:
>>> It's common to use either out-of-tree builds or in-tree builds,
>>> but not to mix both variants with a common root directory.
>>> I think QEMU should explicitly forbid that mixed scenario (like
>>> other projects do).
>>>
>>> Even with your fix there can remain problems with generated
>>> header files.
>>
>> Really? Can you provide more specific details?
>
> Yes. Suppose different generated header files with the same name
> exist in the source directory tree and in the build directory tree.
>
> Then compiler options (the order of -I options) will determine
> which of two header files with same name will be used in out-of-tree
> builds. If the wrong one (that from the source directory tree) is used,
> the compiler might fail or produce wrong code (for example when
> macro values changed).
>>> The mixed scenario creates unnecessary complexity.
>>> Without the mixed scenario, your patch is not needed.
>>
>> I agree that supporting the mixed scenario shouldn't be a priority.
>> However without this last patch a "make clean" on the main tree is not
>> enough to allow out of tree builds.
>>
>> Try the following scenario:
>>
>> - cd qemu; ./configure; make
>>
>> - make clean
>>
>> - cd ../temp; ./configure --source-path=../qemu; make
>
> Which ./configure do you run in an empty temp directory?
> This example (like similar ones in your previous mail) won't work.

Yes, you must do external builds only from a clean source directory.  This is a 
perfectly normal requirement.  In fact, I can't think of a project that doesn't 
require this.

Regards,

Anthony Liguori

>
>>
>> this has to work, right? It does not without the patch to fix the
>> generation of config-devices.mak.
>
> No. You'll need a 'make distclean'. If that does what it should do,
> a following out-of-tree build will work.
>
> Regards,
> Stefan Weil
>
>