Move registry fully to c10

[Yangqing]

This does 6 things:

• add c10/util/Registry.h as the unified registry util
  • cleaned up some APIs such as export condition
• fully remove aten/core/registry.h
• fully remove caffe2/core/registry.h
• remove a bogus aten/registry.h
• unifying all macros
• set up registry testing in c10

Also, an important note that we used to mark the templated Registry class as EXPORT - this should not happen, because one should almost never export a template class. This PR fixes that.

[ezyang]

So... what's the directory structure plan for c10. Can we put all "public" headers at the top level? When does something go in "util"?

[Yangqing]

re directory structure, here is what I am thinking (for now):

• for public header: we might want to have a c10/c10.h that dependent libraries use. Similar to aten/aten.h.
• for internal code structure:
  • macros/ contains all macros and does not depend on anything else
  • util/ contains util functions, registry etc that is framework independent
  • (future) core/ contains core abstractions of framework, like tensors, devices etc. We can also choose to call it framework/
  • (future) serde/ contains serialization and deserialization, with PRIVATE HEADERS and PRIVATE DEPENDENCY on protobuf, effectively hiding our protobuf usage as a public header and that will resolve the protobuf version problem once and for all.

Does that make sense?

[facebook-github-bot]

Yangqing has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[Yangqing]

@pytorchbot retest this please - build seems to have timed out on windows.