Compilation fails.

[shamefulCake1]

/usr/bin/clang++ -DFMT_SHARED -DSPDLOG_COMPILED_LIB -DSPDLOG_FMT_EXTERNAL -DSPDLOG_SHARED_LIB -Dmatrix_client_EXPORTS -I/tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/include -O2 -fPIC -std=c++23 -fpermissive 		-Wall 		-Wextra 		-Wconversion 		-pipe 		-pedantic 		-fsized-deallocation 		-fdiagnostics-color=always 		-Wno-attributes 		-Wunreachable-code -O3 -DNDEBUG -fPIC -pthread -DNOMINMAX -DSPDLOG_SHARED_LIB -DSPDLOG_COMPILED_LIB -DSPDLOG_FMT_EXTERNAL -std=c++20 -MD -MT CMakeFiles/matrix_client.dir/lib/structs/events/messages/file.cpp.o -MF CMakeFiles/matrix_client.dir/lib/structs/events/messages/file.cpp.o.d -o CMakeFiles/matrix_client.dir/lib/structs/events/messages/file.cpp.o -c /tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/lib/structs/events/messages/file.cpp
In file included from /tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/lib/structs/requests.cpp:1:
In file included from /tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/include/mtx/requests.hpp:7:
/usr/bin/../lib64/gcc/x86_64-slackware-linux/11.2.0/../../../../include/c++/11.2.0/variant:84:43: error: implicit instantiation of undefined template 'std::variant_size<mtx::events::collections::StrippedEvents>'
   84 |     struct variant_size<const _Variant> : variant_size<_Variant> {};
      |                                           ^
/usr/bin/../lib64/gcc/x86_64-slackware-linux/11.2.0/../../../../include/c++/11.2.0/variant:1755:15: note: in instantiation of template class 'std::variant_size<const mtx::events::collections::StrippedEvents>' requested here
 1755 |                 std::variant_size<remove_reference_t<_Variants>...>::value>());
      |                      ^
/tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/lib/structs/requests.cpp:57:36: note: in instantiation of function template specialization 'std::visit<(lambda at /tmp/SBo/mtxclient-f4f0bed1c3723daf83d715b98d94b0cde7b42243/lib/structs/requests.cpp:57:42), const mtx::events::collections::StrippedEvents &>' requested here
   57 |             auto event_json = std::visit([](auto e) { return json(e); }, ev);
      |                                    ^
/usr/bin/../lib64/gcc/x86_64-slackware-linux/11.2.0/../../../../include/c++/11.2.0/variant:81:12: note: template is declared here
   81 |     struct variant_size;
      |            ^

[shamefulCake1]

I retried with Hunter, and it still fails.

The last commit which works is 2f42e4fa49e6de63fd6b06b7e21c3530ded50043.

The commit message says that

Does not work with gcc10.

But it does not work with gcc11.2 too.

And, in fact, this is probably more about libstdc++, not gcc, as building with clang++-17 also fails.

Could you add a compiler check? Like check_compile in cmake, or something like that?

[deepbluev7]

This is specifically about a bugfix, which landed in GCC11.3, which was not backported to gcc10 or older: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90943

I am surprised slackware does have gcc11.2 instead of the latest point release. A compiler check is a bit hard, since this is about libstdc++ and I don't know how to check for that version. I guess a check_compile could work, but we depend on a few other issues fixed in newer compilers and enumerating is a bit hard.

[shamefulCake1]

I am surprised slackware does have gcc11.2 instead of the latest point release.

11.2 was the most recent point release when Slackware 15.0 was released, and it's not even 3 years old.