[llvm] [BPF] Handle nested wrapper structs in BPF map definition traversal (PR #144097)

[via llvm-commits]

eddyz87 wrote:

> Accessing the actual map definition requires traversing:
> ```
>  HASH_MAP -> __0 -> value
> ```

I don't understand where the `__0` comes from? Is a field of a structure generated for `pub struct MyKey(u32)`?

https://github.com/llvm/llvm-project/pull/144097