[PATCH] D52339: Support enums with a fixed underlying type in all language modes

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In https://reviews.llvm.org/D52339#1242202, @erik.pilkington wrote:

> From the last line in the paper, it seems that C++ compatibility is a goal of the paper (or at least a consideration). We should probably think about this if/when the final wording gets accepted though.


Agreed. WG14's charter explicitly prefers compatibility with C++ when possible.

The part that I wasn't quite sure on were the type constraints in the proposal. C++ allows any integral type and ignores cv qualifiers, but the proposal lists specific types and doesn't discuss qualifiers. By my reading, this is code allowed in C++ but prohibited in the proposed wording:

  enum E : const int32_t {
    One
  };

(Because the type is int32_t and is cv-qualified.) However, it's possible that's an oversight rather than an intentional design. I'll bring it up with Clive to see, but perhaps we can spot other divergences and can provide him with a list of concerns on the implementation side.



================
Comment at: clang/include/clang/Basic/Features.def:233
 EXTENSION(cxx_variadic_templates, LangOpts.CPlusPlus)
+EXTENSION(cxx_fixed_enum, true)
 // C++14 features supported by other languages as extensions.
----------------
erik.pilkington wrote:
> aaron.ballman wrote:
> > Are we sure we want to make this decision for things like OpenCL, Cuda, etc?
> I can't think of any reason why not, seems there are a handful of other EXTENSION(*, true) features. Do you have a preference?
I think we should probably ask folks from the projects to see if they're okay with the extension or not, but I'd guess this won't be contentious.


Repository:
  rC Clang

https://reviews.llvm.org/D52339