[Buildroot] [PATCH] package/qt5/qt5tools: mark qdoc option as broken

Thomas Petazzoni thomas.petazzoni at bootlin.com
Thu Feb 27 08:03:39 UTC 2020


On Thu, 27 Feb 2020 07:51:51 +0100
<yann.morin at orange.com> wrote:

> > So in the current state, host-clang is added to qt5tools
> > dependency without taking into account BR2_PACKAGE_LLVM_ARCH_SUPPORTS.  
> Then when don't we simply add that depednency instead of hiding it
> behind BROKEN?

I think the idea was that since BR2_PACKAGE_LLVM_ARCH_SUPPORTS only
exposes whether the target architecture is supported by LLVM, it does
not make sense to use that, and for now, we don't have an option to
indicate that the the host architecture is supported by LLVM.

> > But even with host native support in llvm/clang host packages, the
> > host-clang dependency itself increase a lot the build time.
> > 
> > On a laptop with a i7-8565U CPU @ 1.80GHz, host-llvm takes 1100 sec
> > (18,3min) to build and host-clang takes 1200 sec (20min) to build.
> > qt5tools takes 18sec to build.
> > 
> > Increasing the build time by 40min just for the sake of building qdoc
> > is not great.  
> Yes, and so what? If people want to build qdoc because they want to
> generate documentation for their Qt-based programs, and upstream Qt has
> decided they need clang, there is not much we can do about that, can we?
> The build time is no reason to hide away a feature, so there is no
> reason to reference that in the commit log (it could be a post-commit
> note, though).

I agree that the phrasing here is not ideal.

> > Instead we may consider adding a new check in support/dependencies/dependencies.sh
> > for llvm/clang installed on the build machine.
> > This llvm/clang would be used for building qdoc (or mabe other host package).
> > 
> > But we need to be careful for the case where host-llvm and host-clang
> > package are already build.
> > 
> > Then, the qt5tools package would set LLVM_INSTALL_DIR in the
> > additional environment variables to pass to make in the build step,
> > to provide the patch to llvm/clang headers and libraries.
> > 
> > Something like:
> > 	$(TARGET_MAKE_ENV) LLVM_INSTALL_DIR="`/usr/bin/llvm-config --prefix`" \
> > 		$(MAKE) -C $(@D) sub-src-qmake_all
> > [...]  
> All those proposals do not belogn to the commit log, but to a
> post-commit note, too.

Not sure here. Post-commit notes are lost. Commit logs are not. So a
commit log can easily be found by someone who sees the dependency,
finds it annoying, and wants to find what are the alternative solutions.

> Here's my counter-proposal:
>         bool "qdoc host tool"
>         # Needs llvm-config and libclang for the host, which is not
>         # currently supported in Buildroot, unless the target is
>         # already supported by llvm.
>         depends on BR2_PACKAGE_LLVM_ARCH_SUPPORTS

If that works, then that's fine by me.

What I discussed with Romain yesterday is that I didn't want for
2020.02 to do all the work to supports LLVM just for the host (i.e when
the target architecture is not supported), and wanted a more minimal

If your solution works, fine with me. Romain, Yann, could you
coordinate to send an updated patch ?


Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering

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