[PATCH] D127462: [Clang] Begin implementing Plan 9 C extensions

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a reviewer: aaron.ballman.
aaron.ballman added a comment.

In D127462#3877815 <https://reviews.llvm.org/D127462#3877815>, @ksaunders wrote:

> Ping.

Sorry for not noticing this patch was languishing! As far as the patch itself goes, I don't see any major concerns.

Because this is the first of quite a few patches adding various extensions to Clang, I think the idea as a whole should get an RFC on Discourse (https://discourse.llvm.org/c/clang/6) to ensure that the community agrees we should adopt and maintain Plan 9 compatibility. It'd be helpful to focus on the criteria we have for adding extensions to the project (https://clang.llvm.org/get_involved.html#criteria) to the extent you can, but having details like you've got in the summary is also very helpful. That said, I have some questions:

I'm wondering if you could go into a bit more detail about what `Automatic embedded structure type decay` and `Embedded structure type name accesses` mean in practice (some code examples would be helpful).

Are you planning to add a new driver for Clang to emulate the Plan 9 compiler driver (similar to how we have a driver for MSVC compatibility)?
Are there other extensions planned, or is the list in the summary pretty complete?
Do I understand correctly that plan 9 compatibility mode forces C89 as the language standard mode, or is it expected that users can do things like `-std=c2x -fplan9-extensions`?

You can feel free to answer my questions in the Discourse RFC if you don't want to fork the discussion.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127462/new/

https://reviews.llvm.org/D127462