[Buildroot] [RFCv1 4/4] core: implement per-package SDK and target

[Arnout Vandecappelle]

On 24-11-17 15:43, Thomas Petazzoni wrote:
> Hello,
> 
> A few more answers/topics I wanted to discuss.
> 
> On Tue, 7 Nov 2017 23:50:52 +0100, Arnout Vandecappelle wrote:
> 
>>  Given the possible host-tar and host-lzip dependencies, the rsync
>> should be done here already, not in the configure step. Ouch, that's
>> not good, because the dependencies are only evaluated for the
>> configure step... There are PATCH_DEPENDENCIES, but those are only
>> before patch. Well, I guess that's a reason to keep host-tar and
>> host-lzip as DEPENDENCIES_HOST_PREREQ :-)
> 
> Here is how I'm thinking of solving the problem:
> 
>  - Next to <pkg>_PATCH_DEPENDENCIES, introduce the concept of
>    <pkg>_EXTRACT_DEPENDENCIES.

 _PATCH_DEPENDENCIES is different: it introduces a dependency between foo-patch
and bar-patch. Here you want a dependency between foo-extract and tar.

> 
>  - If there is no suitable tar in the system, then host-tar would be
>    added to <pkg>_EXTRACT_DEPENDENCIES of all packages, except host-tar
>    itself.

 So you need an additional NO_EXTRACT_DEPENDENCIES or something to exclude it
for tar...


>  - If the package needs lzip and there is no lzip available on the
>    system, host-lzip is added to <pkg>_EXTRACT_DEPENDENCIES.
> 
>  - If ccache support is enabled, host-ccache is added to
>    <pkg>_DEPENDENCIES of all packages, except host-tar, which is built
>    with HOSTCC_NOCCACHE.
> 
>  - At the beginning of the extract step of a package, we rsync to its
>    per-package target/host directories the per-package target/host dirs
>    of the packages listed in its <pkg>_EXTRACT_DEPENDENCIES variable.
> 
>  - At the beginning of the patch step of a package, we rsync to its
>    per-package target/host directories the per-package target/host dirs
>    of the packages listed in its <pkg>_PATCH_DEPENDENCIES variable.

 So this bit doesn't make sense: _PATCH_DEPENDENCIES are not (necessarily) built
before foo-patch. So to be reproducible, it should *not* be rsynced yet.

> 
> Thoughts?

 I'm not at all happy with this approach. It adds generic-package stuff that is
used for only one package, and it spreads the logic out over different places.

 I'd rather make the logic explicit in dependencies.mk. Something like

ifneq ($(filter host-tar,$(DEPENDENCIES_HOST_PREREQ)),)
$(filter-out host-tar,$(DEPENDENCIES_HOST_PREREQ)): host-tar
endif

ifneq ($(filter host-ccache,$(DEPENDENCIES_HOST_PREREQ)),)
$(filter-out host-tar host-ccache,$(DEPENDENCIES_HOST_PREREQ)): host-ccache
endif

etc. You'll probably want to introduce a variable to collect the filter-out
things, though.


 Regards,
 Arnout


> 
>>> +$(2)_HOST_DIR		= $$(PER_PACKAGE_DIR)/$(1)/host/
>>> +$(2)_STAGING_DIR	= $$(PER_PACKAGE_DIR)/$(1)/host/$(STAGING_SUBDIR)  
>>
>>  I hate adding more per-package variables. Can't you use the expanded values,
>> substituting $($(PKG)_NAME) for $(1)? Or maybe even better, change the
>> definition of TARGET_DIR etc:
>>
>> TARGET_DIR = $(if
>> $(PKG),$(PER_PACKAGE_DIR)/$($(PKG)_RAWNAME)/target,$(BASE_DIR)/target)
>>
>>  That way you also don't need to pass those variables to each individual stamp rule.
> 
> I've changed this in my new iteration. The only drawback is that since
> we no longer have those shortcut variables, the foreach loops building
> the per-package directories, and building the final global directories
> are a bit less readable:
> 
> Per-package host/target creation:
> 
> 	$(foreach pkg,$($(PKG)_FINAL_DEPENDENCIES),\
> 		rsync -a --link-dest=$(PER_PACKAGE_DIR)/$(pkg)/host/ \
> 		$(PER_PACKAGE_DIR)/$(pkg)/host/ \
> 		$(HOST_DIR)$(sep))
> 	$(foreach pkg,$($(PKG)_FINAL_DEPENDENCIES),\
> 		rsync -a --link-dest=$(PER_PACKAGE_DIR)/$(pkg)/target/ \
> 		$(PER_PACKAGE_DIR)/$(pkg)/target/ \
> 		$(TARGET_DIR)$(sep))
> 
> Global host/target creation in target-finalize:
> 
> 	$(foreach pkg,$(PACKAGES),\
> 		rsync -a --link-dest=$(PER_PACKAGE_DIR)/$(pkg)/target/ \
> 		$(PER_PACKAGE_DIR)/$(pkg)/target/ \
> 		$(TARGET_DIR)$(sep))
> 	@$(call MESSAGE,"Creating global host directory")
> 	$(foreach pkg,$(PACKAGES),\
> 		rsync -a --link-dest=$(PER_PACKAGE_DIR)/$(pkg)/host/ \
> 		$(PER_PACKAGE_DIR)/$(pkg)/host/ \
> 		$(HOST_DIR)$(sep))
> 
> But I guess that's OK. If we find that too weird, I can always
> introduce some some make helpers:
> 
> per-package-target-dir = $(PER_PACKAGE_DIR)/$(1)/target
> per-package-host-dir = $(PER_PACKAGE_DIR)/$(1)/host
> 
> But:
> 
>   $(call per-package-target-dir,$(pkg))
> 
> is not really shorter than
> 
>   $(PER_PACKAGE_DIR)/$(1)/target
> 
> It is actually longer :-)
> 
> Thomas
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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