CheckMetricName about prometheus-cpp

[QuanjieDeng]

BTW, I'm using version 1.1.0

[gjasny]

Please check with nm how the CheckMetricName symbol looks like in your lib. This is for example on macOS:

nm -C cmake-build-debug/lib/libprometheus-cpp-core.a | grep CheckMetricName

0000000000000000 T prometheus::CheckMetricName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)
0000000000000178 t std::__1::__wrap_iter<char const*> std::__1::find_if_not[abi:v160006]<std::__1::__wrap_iter<char const*>, prometheus::CheckMetricName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)::$_0>(std::__1::__wrap_iter<char const*>, std::__1::__wrap_iter<char const*>, prometheus::CheckMetricName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)::$_0)
0000000000000900 t prometheus::CheckMetricName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)::$_0::operator()(char) const
                 U prometheus::CheckMetricName(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&)

The line with T shows the definition of the function. It should be exactly the same as in the ld error message.

Another source of problems is the ordering of libs (and object files). The libprometheus-cpp-core.a lib should come last.