[PATCH] D41553: Support parsing double square-bracket attributes in ObjC

John McCall via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Jan 2 19:29:40 PST 2018

rjmccall added inline comments.

Comment at: include/clang/Basic/Attr.td:239
+  bit IncludeC = includeC;
I have no objection to allowing ObjC attributes to be spelled in [[clang::objc_whatever]] style.  We can debate giving them a more appropriate standard name in the objc namespace at a later time — or even the primary namespace, if we really want to flex our Somewhat Major Language muscles.

I feel like this IncludeC is not the best name for this tablegen property.  Perhaps AllowInC?

Also, a random positional 1 argument is pretty obscure TableGen design.  Do we really expect to be making very many attributes that intentionally disallow C2x?  What would these be, just C++-specific attributes without C analogues?  It doesn't seem important to prohibit those at the parsing level rather than at the semantic level, since, after all, we are still allowing the GNU-style spelling, and these would still qualified with ``clang::``.

I would suggest standardizing in the opposite direction:  instead of forcing attributes to opt in to being allowed in C, we should make attributes that we really don't want to allow in the C2x [[clang::]] namespace be explicit about it.  If there are a lot of C++-specific attributes like that, we can make a ClangCXXOnly subclass.


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