[Buildroot] Build failure on qt5webkit

[Buildroot] Build failure on qt5webkit

[Alexis Lothoré via buildroot]

Hello Buildroot community,

I am facing a build issue with qt5webkit package on buildroot 2025.02.x.
The build outputs the following error:

/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1237:52: error: non-constant condition for static assertion
 1237 |       static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1237:52: error: ‘constexpr std::true_type std::__is_complete_or_unbounded(__type_identity<_Tp>) [with _Tp = WTF::Vector<unsigned char>; unsigned int <anonymous> = 12; true_type = true_type]’ used before its definition
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits: In instantiation of ‘struct std::is_move_assignable<WebCore::ContentSecurityPolicyHashAlgorithm>’:
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:183:35:   required by substitution of ‘template<class ... _Bn> std::__detail::__first_t<std::integral_constant<bool, true>, typename std::enable_if<(bool)(_Bn::value), void>::type ...> std::__detail::__and_fn(int) [with _Bn = {std::is_move_assignable<WebCore::ContentSecurityPolicyHashAlgorithm>, std::is_move_assignable<WTF::Vector<unsigned char, 0, WTF::CrashOnOverflow, 16> >}]’
  183 |                                       __enable_if_t<bool(_Bn::value)>...>;
      |                                                               ^~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:199:42:   required from ‘struct std::__and_<std::is_move_assignable<WebCore::ContentSecurityPolicyHashAlgorithm>, std::is_move_assignable<WTF::Vector<unsigned char, 0, WTF::CrashOnOverflow, 16> > >’
  199 |     : decltype(__detail::__and_fn<_Bn...>(0))
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/bits/stl_pair.h:932:38:   required from ‘struct std::pair<WebCore::ContentSecurityPolicyHashAlgorithm, WTF::Vector<unsigned char> >’
  932 |                                        is_move_assignable<_T2>>::value,
      |                                                                  ^~~~~
/home/alexis/src/buildroot/output/build/qt5webkit-5.212.0-alpha4/Source/WebCore/page/csp/ContentSecurityPolicy.cpp:235:56:   required from here
  235 |             if ((policy.get()->*allowed)(std::make_pair(algorithm, digest)))
      |                                          ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1246:52: error: non-constant condition for static assertion
 1246 |       static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1246:52: error: ‘constexpr std::true_type std::__is_complete_or_unbounded(__type_identity<_Tp>) [with _Tp = WebCore::ContentSecurityPolicyHashAlgorithm; unsigned int <anonymous> = 4; true_type = true_type]’ used before its definition
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits: In instantiation of ‘struct std::is_move_assignable<WTF::Vector<unsigned char> >’:
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:183:35:   required by substitution of ‘template<class ... _Bn> std::__detail::__first_t<std::integral_constant<bool, true>, typename std::enable_if<(bool)(_Bn::value), void>::type ...> std::__detail::__and_fn(int) [with _Bn = {std::is_move_assignable<WebCore::ContentSecurityPolicyHashAlgorithm>, std::is_move_assignable<WTF::Vector<unsigned char, 0, WTF::CrashOnOverflow, 16> >}]’
  183 |                                       __enable_if_t<bool(_Bn::value)>...>;
      |                                                               ^~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:199:42:   required from ‘struct std::__and_<std::is_move_assignable<WebCore::ContentSecurityPolicyHashAlgorithm>, std::is_move_assignable<WTF::Vector<unsigned char, 0, WTF::CrashOnOverflow, 16> > >’
  199 |     : decltype(__detail::__and_fn<_Bn...>(0))
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/bits/stl_pair.h:932:38:   required from ‘struct std::pair<WebCore::ContentSecurityPolicyHashAlgorithm, WTF::Vector<unsigned char> >’
  932 |                                        is_move_assignable<_T2>>::value,
      |                                                                  ^~~~~
/home/alexis/src/buildroot/output/build/qt5webkit-5.212.0-alpha4/Source/WebCore/page/csp/ContentSecurityPolicy.cpp:235:56:   required from here
  235 |             if ((policy.get()->*allowed)(std::make_pair(algorithm, digest)))
      |                                          ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1246:52: error: non-constant condition for static assertion
 1246 |       static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
/home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1246:52: error: ‘constexpr std::true_type std::__is_complete_or_unbounded(__type_identity<_Tp>) [with _Tp = WTF::Vector<unsigned char>; unsigned int <anonymous> = 12; true_type = true_type]’ used before its definition

The issue can be replicated with the following minimal defconfig:
  BR2_arm=y
  BR2_cortex_a9=y
  BR2_ARM_ENABLE_NEON=y
  BR2_ARM_ENABLE_VFP=y
  BR2_ARM_FPU_NEON=y
  BR2_TOOLCHAIN_EXTERNAL=y
  BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y
  BR2_PACKAGE_QT5=y
  BR2_PACKAGE_QT5WEBKIT=y

I am not very fluent in C++, so I struggle to fix it. Based on the build
logs, I guess it relates to some missing some header include
(ContentSecurityPolicyHash.h, containing the definition for
ContentSecurityPolicyHashAlgorithm definition ?), so I tried to sprinkle some
includes in the modules consuming it, but without success so far. I also
took a look at both webkit and qtwebkit upstream sources, hoping that the
issue could have been observed and fixed, but I found nothing yet (and
qtwebkit does not look alive, based on latest commits dates).

I am posting this issue here in case anyone has already encountered it and
found a fix that could be properly integrated in buildroot, but otherwise I
guess the next step will be to notify the upstream webkit community.

Thanks,

Alexis

-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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Re: [Buildroot] Build failure on qt5webkit

[Philipp Ludwig]

On 7/15/25 14:42, Alexis Lothoré via buildroot wrote:
> I am facing a build issue with qt5webkit package on buildroot 2025.02.x.
> The build outputs the following error:
> 
> /home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1237:52: error: non-constant condition for static assertion

> I am not very fluent in C++, so I struggle to fix it. Based on the build
> logs, I guess it relates to some missing some header include
> (ContentSecurityPolicyHash.h, I believe it has to do with the qt5webkit source not working with the
g++ version you got. Your g++ might be too new. type_traits has changed 
a bit over the past, so that *might* have something to do with it.

 > and qtwebkit does not look alive, based on latest commits dates).
It was deprecated in Qt 5.5 back in 2015. Some people forked it and kept 
it alive until 2019 or so, and now there is another fork going on here:

https://github.com/movableink/webkit

The "official" recommendation is to use QtWebEngine or QtWebView, 
whatever is more appropriate. But I could not get either of them to 
build with buildroot, so YMMV.

An embedded version of webkit is WPE, which is also available in 
buildroot as WPEWEBKIT: https://webkit.org/wpe/

Best regards
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Re: [Buildroot] Build failure on qt5webkit

[Alexis Lothoré via buildroot]

Hi  Philipp,

On Wed Jul 16, 2025 at 8:19 AM CEST, Philipp Ludwig wrote:
> On 7/15/25 14:42, Alexis Lothoré via buildroot wrote:
>> I am facing a build issue with qt5webkit package on buildroot 2025.02.x.
>> The build outputs the following error:
>> 
>> /home/alexis/src/buildroot/output/host/opt/ext-toolchain/arm-buildroot-linux-gnueabihf/include/c++/14.2.0/type_traits:1237:52: error: non-constant condition for static assertion
>
>> I am not very fluent in C++, so I struggle to fix it. Based on the build
>> logs, I guess it relates to some missing some header include
>> (ContentSecurityPolicyHash.h, I believe it has to do with the qt5webkit source not working with the
> g++ version you got. Your g++ might be too new. type_traits has changed 
> a bit over the past, so that *might* have something to do with it.

Yes, that's very likely my new toolchain version that is triggering this
issue. I had a build passing with a slightly older toolchain. The toolchain
update has been driven by the need of fresher kernel headers for other
packages, but a solution could be to use a custom toolchain with only the
kernel headers update, not updating g++.

>  > and qtwebkit does not look alive, based on latest commits dates).
> It was deprecated in Qt 5.5 back in 2015. Some people forked it and kept 
> it alive until 2019 or so, and now there is another fork going on here:
>
> https://github.com/movableink/webkit
>
> The "official" recommendation is to use QtWebEngine or QtWebView, 
> whatever is more appropriate. But I could not get either of them to 
> build with buildroot, so YMMV.
>
> An embedded version of webkit is WPE, which is also available in 
> buildroot as WPEWEBKIT: https://webkit.org/wpe/

Thanks for the confirmation and the hints for new packages. I have given a
quick try to the fork, but it does not look any better. Some branches
mentioned in the README can not even be found in the repo. I guess I'll
need to get rid of/replace those dependencies.

Thanks,

Alexis
>
> Best regards
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot




-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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Re: [Buildroot] Build failure on qt5webkit

[Thomas Petazzoni via buildroot]

Hello Alexis,

On Tue, 15 Jul 2025 14:42:21 +0200
Alexis Lothoré via buildroot <buildroot@buildroot.org> wrote:

> I am facing a build issue with qt5webkit package on buildroot 2025.02.x.
> The build outputs the following error:

FYI, I also faced this issue today, and I have a fix for it. I'll
submit together with several other qt5webkit fixes (I have a successful
qt5webkit build with gcc 15.x).

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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