Potential upcoming issues with clang

[krono]

It seems it will be harder to deal with Tagged Pointers in Clang 13: llvm/llvm-project#59889

This could impact a lot of our generated cod.e

[rmacnak]

Doesn't Cog represent tagged pointers as C integer types? It's only representing tagged pointers as C++ pointer types that's a problem.

Dart and Primordial Soup's workaround for this is basically to represent tagged pointers as a C++ value type wrapping an integer, always untag before casting to a C++ pointer type to dereference members, and use an overload of operator -> on the tagged pointer type to avoid needing to rewrite most obj->untag()->field as obj.untag()->field.

[dtlewis290]

If the concern is for the way that immediates are represented in object pointers, then this clang issue will not be a problem. We do not use C++ and the mappings between integral object points and pointer addresses is not affected.