WenTao Ou

@lalitb This issue has not be finished completely.I'm waiting for #1413 and then continue to implement `LogEmitter`, there may be more conflicts if I do it now.

BTW: Why don't we upgrade gRPC to the latest version of gRPC(v1.48.0)?

I vote for upgrade the minimum version of cmake.It will be easier to maintain.

> There are few more cmake constructs in code not supported in cmake v3.1.0: > > https://github.com/open-telemetry/opentelemetry-cpp/blob/a847d0ce42209e458f8f98a5751626a33adfad95/CMakeLists.txt#L9 > > https://github.com/open-telemetry/opentelemetry-cpp/blob/76c664a20b8219b91ead69ded6b7ee873b1a85ba/ext/test/http/CMakeLists.txt#L4 I think `add_compile_definitions(WITH_CURL) ` can be removed now.

Could we keep few CI jobs for the old metrics, just like `LogName` in log APIs? There are some projects use the old implements and it will take some time...

I have add more examples [here](https://github.com/open-telemetry/opentelemetry-cpp/issues/1520#issuecomment-1198104171), and `__declspec (selectany)` of MSVC works well, but `__attribute__ ((selectany))` of GCC on Windows do not work as expected,do I miss anything?

> Resources: > > > Paper from Ulrich Drepper, see section 2.2 export control, page 17: > > https://akkadia.org/drepper/dsohowto.pdf > > > Gnu visibility doc > > https://gcc.gnu.org/wiki/Visibility I have...

> @owent - We agreed this PR to be scoped for Linux and Mac. Let us know if you have any comment on that. Fine by me. I think we...

> @lalitb , @esigo , @owent > > I added a singleton_test unit test, and makefiles for both CMake and Bazel. > > This test does not build properly on...

We use cmake CONFIG file and bazel dependency to auto declaration macros now. We can use [configure_file](https://cmake.org/cmake/help/latest/command/configure_file.html) to generate header file which include all macros during configure time.But I'm not...