Unable to link

[kershnerd]

I am on a mac and having trouble compiling. I needed to implement @lsarkisov PR (#1) and I was able to compile.

Now I am having a linker error and I have no idea what this means:

/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake --build /Users/jeff/projects/personal/cpp_weekly_game_project/cmake-build-debug --target game -- -j 6
[ 50%] Linking CXX executable ../bin/game
Undefined symbols for architecture x86_64:
  "fmt::v6::internal::basic_data<void>::signs", referenced from:
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<float, 0>(float, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::nonfinite_writer<char>::operator()<char*>(char*&&) const in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::nonfinite_writer<char>::operator()<char*&>(char*&) const in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::float_writer<char>::operator()<char*>(char*&&) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::float_writer<char>::operator()<char*&>(char*&) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<double, 0>(double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<long double, 0>(long double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
      ...
  "fmt::v6::internal::assert_fail(char const*, int, char const*)", referenced from:
      fmt::v6::basic_memory_buffer<char, 250ul, std::__1::allocator<char> >::operator=(fmt::v6::basic_memory_buffer<char, 250ul, std::__1::allocator<char> >&&) in libspdlogd.a(spdlog.cpp.o)
      std::__1::make_unsigned<long>::type fmt::v6::internal::to_unsigned<long>(long) in libspdlogd.a(spdlog.cpp.o)
      char const* fmt::v6::internal::parse_arg_id<char, fmt::v6::internal::id_adapter<fmt::v6::format_handler<fmt::v6::arg_formatter<fmt::v6::buffer_range<char> >, char, fmt::v6::basic_format_context<std::__1::back_insert_iterator<fmt::v6::internal::buffer<char> >, char> >&, char> >(char const*, char const*, fmt::v6::internal::id_adapter<fmt::v6::format_handler<fmt::v6::arg_formatter<fmt::v6::buffer_range<char> >, char, fmt::v6::basic_format_context<std::__1::back_insert_iterator<fmt::v6::internal::buffer<char> >, char> >&, char>&&) in libspdlogd.a(spdlog.cpp.o)
      decltype(fp(0)) fmt::v6::visit_format_arg<fmt::v6::arg_formatter<fmt::v6::buffer_range<char> >, fmt::v6::basic_format_context<std::__1::back_insert_iterator<fmt::v6::internal::buffer<char> >, char> >(fmt::v6::arg_formatter<fmt::v6::buffer_range<char> >&&, fmt::v6::basic_format_arg<fmt::v6::basic_format_context<std::__1::back_insert_iterator<fmt::v6::internal::buffer<char> >, char> > const&) in libspdlogd.a(spdlog.cpp.o)
      fmt::v6::internal::arg_formatter_base<fmt::v6::buffer_range<char>, fmt::v6::internal::error_handler>::operator()(fmt::v6::monostate) in libspdlogd.a(spdlog.cpp.o)
      std::__1::make_unsigned<int>::type fmt::v6::internal::to_unsigned<int>(int) in libspdlogd.a(spdlog.cpp.o)
      unsigned int fmt::v6::internal::format_decimal<char, unsigned int, char*, char* fmt::v6::internal::format_decimal<char, char*, unsigned int>(char*, unsigned int, int)::'lambda'(char*)>(unsigned int, char*, int, char* fmt::v6::internal::format_decimal<char, char*, unsigned int>(char*, unsigned int, int)::'lambda'(char*)) in libspdlogd.a(spdlog.cpp.o)
      ...
  "int fmt::v6::internal::format_float<double>(double, int, fmt::v6::internal::float_specs, fmt::v6::internal::buffer<char>&)", referenced from:
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<float, 0>(float, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<double, 0>(double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
  "int fmt::v6::internal::format_float<long double>(long double, int, fmt::v6::internal::float_specs, fmt::v6::internal::buffer<char>&)", referenced from:
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<long double, 0>(long double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping_impl<char>(fmt::v6::internal::locale_ref)", referenced from:
      std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping<char>(fmt::v6::internal::locale_ref) in libspdlogd.a(spdlog.cpp.o)
  "int fmt::v6::internal::snprintf_float<double>(double, int, fmt::v6::internal::float_specs, fmt::v6::internal::buffer<char>&)", referenced from:
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<float, 0>(float, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<double, 0>(double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
  "int fmt::v6::internal::snprintf_float<long double>(long double, int, fmt::v6::internal::float_specs, fmt::v6::internal::buffer<char>&)", referenced from:
      void fmt::v6::internal::basic_writer<fmt::v6::buffer_range<char> >::write<long double, 0>(long double, fmt::v6::basic_format_specs<char>) in libspdlogd.a(spdlog.cpp.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [bin/game] Error 1
make[2]: *** [src/CMakeFiles/game.dir/all] Error 2
make[1]: *** [src/CMakeFiles/game.dir/rule] Error 2
make: *** [game] Error 2

Any ideas?

[ddalcino]

I am on Fedora, and I was having a very similar link-time problem with spdlog, using g++-9 rather than clang. It looks like spdlog 1.5.0 wants to work with a newer version of fmt.

There are (at least) two solutions to this that require modifying src/Conan.cmake:

1. Update fmt to version 6.1.2 (this appears to work with spdlog 1.5.0)
2. Downgrade spdlog to version 1.4.2 (this appears to work with fmt 6.0.0)

Both of these approaches allowed me to get a successful build.

If you are wondering how I figured this out, look at the last few lines of the error message. The spdlog library, libspdlogd.a(spdlog.cpp.o), wants to link to some functions in fmt. That made me think that I should try using different versions of each library. So, I looked up what versions were available at https://conan.io/center/.

I am unclear as to why lefticus was not having the same problem on Ubuntu.

[kershnerd]

Thank you @ddalcino