Bug 275872 – error: pack expansion contains parameter pack '_UTypes' that has a different length (3 vs. 1) from outer parameter packs

• Status: NEW
• Component: WebKitGTK

[Michael Catanzaro]

I failed to build WebKitGTK 2.45.4 for GNOME. The error message is a little impressive:

/usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/tuple:691:2: error: pack expansion contains parameter pack '_UTypes' that has a different length (3 vs. 1) from outer parameter packs
      691 |         using __convertible = __and_<is_convertible<_UTypes, _Types>...>;
          |         ^~~~~
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/tuple:853:27: note: in instantiation of template type alias '__convertible' requested here
      853 |           = _TCC<true>::template __convertible<_Args...>::value;
          |                                  ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/tuple:948:12: note: in instantiation of static data member 'std::tuple<gl::TextureType, unsigned int, unsigned int>::__convertible<const std::tuple<gl::TextureType, unsigned int, unsigned int> &>' requested here
      948 |         explicit(!__convertible<_UElements&...>)
          |                   ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/type_traits:1108:57: note: while substituting deduced template arguments into function template 'tuple' [with _UElements = <const std::tuple<gl::TextureType, unsigned int, unsigned int> &>]
     1108 |       = __bool_constant<__is_nothrow_constructible(_Tp, _Args...)>;
          |                                                         ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/type_traits:1108:57: note: while substituting deduced template arguments into function template 'tuple' [with _NotEmpty = (no value), $1 = (no value)]
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/type_traits:1114:14: note: in instantiation of template type alias '__is_nothrow_constructible_impl' requested here
     1114 |     : public __is_nothrow_constructible_impl<_Tp, _Args...>
          |              ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/alloc_traits.h:534:16: note: (skipping 3 contexts in backtrace; use -ftemplate-backtrace-limit=0 to see all)
      534 |         noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
          |                       ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_tree.h:614:4: note: in instantiation of function template specialization 'std::_Rb_tree<std::tuple<gl::TextureType, unsigned int, unsigned int>, std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>, std::_Select1st<std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>>, std::less<std::tuple<gl::TextureType, unsigned int, unsigned int>>>::_M_construct_node<const std::piecewise_construct_t &, std::tuple<const std::tuple<gl::TextureType, unsigned int, unsigned int> &>, std::tuple<>>' requested here
      614 |           _M_construct_node(__tmp, std::forward<_Args>(__args)...);
          |           ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_tree.h:1637:18: note: in instantiation of function template specialization 'std::_Rb_tree<std::tuple<gl::TextureType, unsigned int, unsigned int>, std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>, std::_Select1st<std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>>, std::less<std::tuple<gl::TextureType, unsigned int, unsigned int>>>::_M_create_node<const std::piecewise_construct_t &, std::tuple<const std::tuple<gl::TextureType, unsigned int, unsigned int> &>, std::tuple<>>' requested here
     1637 |             _M_node(__t._M_create_node(std::forward<_Args>(__args)...))
          |                         ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_tree.h:2462:13: note: in instantiation of function template specialization 'std::_Rb_tree<std::tuple<gl::TextureType, unsigned int, unsigned int>, std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>, std::_Select1st<std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>>, std::less<std::tuple<gl::TextureType, unsigned int, unsigned int>>>::_Auto_node::_Auto_node<const std::piecewise_construct_t &, std::tuple<const std::tuple<gl::TextureType, unsigned int, unsigned int> &>, std::tuple<>>' requested here
     2462 |         _Auto_node __z(*this, std::forward<_Args>(__args)...);
          |                    ^
    /usr/bin/../lib/gcc/x86_64-unknown-linux-gnu/13.2.0/../../../../include/c++/13.2.0/bits/stl_map.h:513:15: note: in instantiation of function template specialization 'std::_Rb_tree<std::tuple<gl::TextureType, unsigned int, unsigned int>, std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>, std::_Select1st<std::pair<const std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>>, std::less<std::tuple<gl::TextureType, unsigned int, unsigned int>>>::_M_emplace_hint_unique<const std::piecewise_construct_t &, std::tuple<const std::tuple<gl::TextureType, unsigned int, unsigned int> &>, std::tuple<>>' requested here
      513 |           __i = _M_t._M_emplace_hint_unique(__i, std::piecewise_construct,
          |                      ^
    /buildstream/gnome/sdk/webkit2gtk-4.1.bst/Source/ThirdParty/ANGLE/src/libANGLE/renderer/gl/BlitGL.cpp:1481:40: note: in instantiation of member function 'std::map<std::tuple<gl::TextureType, unsigned int, unsigned int>, rx::BlitGL::BlitProgram>::operator[]' requested here
     1481 |     BlitProgram &result = mBlitPrograms[programType];
          |                                        ^

Not sure what's wrong yet.

[Michael Catanzaro]

https://gitlab.gnome.org/GNOME/gnome-build-meta/-/jobs/4014334

[Alberto Garcia]

This only happens with clang, with gcc it works fine

[Michael Catanzaro]

Yes. I have switched the GNOME runtime from Clang back to GCC due to this issue because I cannot reproduce it on my host system with libstdc++ 14. I'm guessing only libstdc++ 13 is affected, but I'm not sure.

[Michael Catanzaro]

By coincidence, GNOME just did its annual upgrade from GCC 13 to GCC 14. This Clang build failure is now fixed with the newer libstdc++.

[Michael Catanzaro]

(In reply to Michael Catanzaro from comment #4)
> By coincidence, GNOME just did its annual upgrade from GCC 13 to GCC 14.
> This Clang build failure is now fixed with the newer libstdc++.

Turns out this is a regression between 2.44 -> 2.46. I'm going to switch the GNOME 46 build back to GCC rather than Clang so that I can upgrade to 2.46. This means we lose all those Skia optimizations, but it's easier than trying to figure out what this error message goo is trying to tell us.

[Michael Catanzaro]

(In reply to Michael Catanzaro from comment #4)
> By coincidence, GNOME just did its annual upgrade from GCC 13 to GCC 14.
> This Clang build failure is now fixed with the newer libstdc++.

(For avoidance of doubt, GNOME 47 gets the new libstdc++. GNOME 46 stays on GCC 13 forever, just as Linux distros would do.)