WenTao Ou

Could you please alse add cmake targets in `exporters/memory/CMakeLists.txt` and `cmake/opentelemetry-cpp-config.cmake.in` .

> > Could you please alse add cmake targets in `exporters/memory/CMakeLists.txt` and `cmake/opentelemetry-cpp-config.cmake.in` . > > Sure, I can add that. I feel supporting/maintaining two build systems is a little...

Could you please revert changes in `/exporters/otlp` ?It's duplicated with #1487 , I belive this PR is just for memory metrics exporter.

> > Could you please revert changes in `/exporters/otlp` ?It's duplicated with #1487 , I belive this PR is just for memory metrics exporter. > > The change under exporters/otlp...

> Note: This issue is simular to https://github.com/grpc/grpc/issues/20194 of grpc We should also support to share our event loop with grpc's in the future.

I think it's difficult to use [bazel-to-cmake][1] like tools. CMake support environment detection better and has a better compatibility then bazel.(e.g. We support gcc 4.8 and use a old version...

Also, nosend shoube be installed when using cmake.

Maybe it's better to remove warning from protobuf? There is a lot warnings which are come from protobuf headers, for example: ``` [build] D:\prebuilt\vcpkg\installed\x64-windows\include\google/protobuf/stubs/logging.h(102,23): warning C4251: “google::protobuf::internal::LogMessage::message_”: class“std::basic_string”需要有 dll 接口由...

> For the suggested flag like `OPENTELEMETRY_HAVE_STD_SHARED_PTR`, could they be detected by CMake automatically so no need to expose these flags to developers? ```cmake check_cxx_source_compiles( " #include #include int main()...

We can use codes like these to export/import APIs of some libraries. ```cpp // ================ import/export: for compilers ================ #if defined(__GNUC__) && !defined(__ibmxl__) // GNU C++/Clang // // Dynamic shared...