package/qt5/qt5tools: mark qdoc option as broken
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Message ID 20200226232237.292826-1-romain.naour@smile.fr
State Changes Requested
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  • package/qt5/qt5tools: mark qdoc option as broken
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Commit Message

Romain Naour Feb. 26, 2020, 11:22 p.m. UTC
When qdoc option was added by [1] for Qt 5.12, the host-clang
dependecy was added as if host-clang would provide a host native
compiler.

The host-clang package provide host libclang libraries needed by
the cross-build process for target packages. The default target
arch is set with the target architecture. It would require adding
compiler flag to select the architecture to generate binaries
(host or target).

We can consider adding native build suport by merging the
patch [3]. But it was not merged in time for Buildroot
2020.02.

So in the current state, host-clang is added to qt5tools
dependency without taking into account BR2_PACKAGE_LLVM_ARCH_SUPPORTS.

For some architectures supported by Qt5 (i.e riscv), two
llvm build options are not correcltly set:

-DLLVM_TARGETS_TO_BUILD="" -DLLVM_TARGET_ARCH=

So the build is broken.

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.

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:
define QT5TOOLS_BUILD_CMDS
	$(TARGET_MAKE_ENV) LLVM_INSTALL_DIR="`/usr/bin/llvm-config --prefix`" \
		$(MAKE) -C $(@D) sub-src-qmake_all
[...]

Since all possible solution are too late for 2020.02 release, disable
BR2_PACKAGE_QT5TOOLS_QDOC_TOOL option.

Fixes:
http://autobuild.buildroot.net/results/3c0/3c0f27e953fa41bd973003a4b42b768b1636c91a/build-end.log

[1] 57c1d3be4ecadd6802414a0943185c4ab6d82937
[2] https://www.linuxembedded.fr/2018/07/llvmclang-integration-into-buildroot
[3] http://patchwork.ozlabs.org/patch/1204740/

Signed-off-by: Romain Naour <romain.naour@smile.fr>
Cc: Yann E. MORIN <yann.morin@orange.com>
Cc: Julien Corjon <corjon.j@ecagroup.com>
Cc: Peter Seiderer <ps.report@gmx.net>
---
 package/qt5/qt5tools/Config.in | 3 +++
 1 file changed, 3 insertions(+)

Comments

Yann E. MORIN Feb. 27, 2020, 6:51 a.m. UTC | #1
Romain, All,

On 2020-02-27 00:22 +0100, Romain Naour spake thusly:
> When qdoc option was added by [1] for Qt 5.12, the host-clang
> dependecy was added as if host-clang would provide a host native
> compiler.
> 
> The host-clang package provide host libclang libraries needed by
> the cross-build process for target packages. The default target
> arch is set with the target architecture. It would require adding
> compiler flag to select the architecture to generate binaries
> (host or target).
> 
> We can consider adding native build suport by merging the
> patch [3]. But it was not merged in time for Buildroot
> 2020.02.
> 
> 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?

See below for a phrasing proposal...

> 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).

> 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:
> define QT5TOOLS_BUILD_CMDS
> 	$(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.

> Since all possible solution are too late for 2020.02 release, disable

*solution_s_.

> BR2_PACKAGE_QT5TOOLS_QDOC_TOOL option.
> 
> Fixes:
> http://autobuild.buildroot.net/results/3c0/3c0f27e953fa41bd973003a4b42b768b1636c91a/build-end.log
> 
> [1] 57c1d3be4ecadd6802414a0943185c4ab6d82937
> [2] https://www.linuxembedded.fr/2018/07/llvmclang-integration-into-buildroot
> [3] http://patchwork.ozlabs.org/patch/1204740/
> 
> Signed-off-by: Romain Naour <romain.naour@smile.fr>
> Cc: Yann E. MORIN <yann.morin@orange.com>
> Cc: Julien Corjon <corjon.j@ecagroup.com>
> Cc: Peter Seiderer <ps.report@gmx.net>
> ---
>  package/qt5/qt5tools/Config.in | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/package/qt5/qt5tools/Config.in b/package/qt5/qt5tools/Config.in
> index 14178abc29..5ef85a88b3 100644
> --- a/package/qt5/qt5tools/Config.in
> +++ b/package/qt5/qt5tools/Config.in
> @@ -19,6 +19,9 @@ config BR2_PACKAGE_QT5TOOLS_LINGUIST_TOOLS
>  
>  config BR2_PACKAGE_QT5TOOLS_QDOC_TOOL
>  	bool "qdoc host tool"
> +	# Needs llvm-config and libclang installed on the build machine.

No, that's wrong: it does not need them to be "installed on the build
machine". It just needs them.

> +	# host-llvm and host-clang packages doesn't provide a host compiler.
> +	depends on BROKEN

Here's my counter-proposal:

    config BR2_PACKAGE_QT5TOOLS_QDOC_TOOL
        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

And a comment about it:

    comment "qdoc not supported for current target"
        depends on !BR2_PACKAGE_LLVM_ARCH_SUPPORTS

Regards,
Yann E. MORIN.

>  	help
>  	  This option enables the qdoc host tool.
>  
> -- 
> 2.24.1
>
Thomas Petazzoni Feb. 27, 2020, 8:03 a.m. UTC | #2
Hello,

On Thu, 27 Feb 2020 07:51:51 +0100
<yann.morin@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:
> > define QT5TOOLS_BUILD_CMDS
> > 	$(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:
> 
>     config BR2_PACKAGE_QT5TOOLS_QDOC_TOOL
>         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
solution.

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

Thanks!

Thomas
Romain Naour Feb. 27, 2020, 8:56 p.m. UTC | #3
Hello Yann, Thomas,

Le 27/02/2020 à 09:03, Thomas Petazzoni a écrit :
> Hello,
> 
> On Thu, 27 Feb 2020 07:51:51 +0100
> <yann.morin@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.

Indeed. If we add this dependency BR2_PACKAGE_LLVM_ARCH_SUPPORTS for the failing
build below on riscv [1] the qdoc option would be unavailable. Even we only need
to build host-llvm and host-clang.

> 
>>> 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.

Ok, the patch is too "aggressive" against the qdoc option... But the build time
is certainly important for users. I would suggest to use llvm/clang installed on
the host to avoid spend 40min to build them.

> 
>>> 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:
>>> define QT5TOOLS_BUILD_CMDS
>>> 	$(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.

That is exactly why I added the proposal here. To suggest something in the
commit log for those who want to generate documentation.

> 
> 
>> Here's my counter-proposal:
>>
>>     config BR2_PACKAGE_QT5TOOLS_QDOC_TOOL
>>         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
> solution.

This is the more minimal solution, but it require to build host-llvm and host-clang.

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

I'm fine for 2020.02.

Best regards,
Romain

> 
> Thanks!
> 
> Thomas
>

Patch
diff mbox series

diff --git a/package/qt5/qt5tools/Config.in b/package/qt5/qt5tools/Config.in
index 14178abc29..5ef85a88b3 100644
--- a/package/qt5/qt5tools/Config.in
+++ b/package/qt5/qt5tools/Config.in
@@ -19,6 +19,9 @@  config BR2_PACKAGE_QT5TOOLS_LINGUIST_TOOLS
 
 config BR2_PACKAGE_QT5TOOLS_QDOC_TOOL
 	bool "qdoc host tool"
+	# Needs llvm-config and libclang installed on the build machine.
+	# host-llvm and host-clang packages doesn't provide a host compiler.
+	depends on BROKEN
 	help
 	  This option enables the qdoc host tool.