[PATCH] D125167: [WIP] Fix member access of anonymous struct/union fields in C

Mon May 9 09:19:32 PDT 2022

tahonermann added inline comments.

================
Comment at: clang/test/Sema/anonymous-struct-union.c:137-140
+  // It's the access path that picks up the qualifiers, not the direct
+  // declaration of the field itself. So 'i' and 'j' are both 'int'.
+  _Static_assert(_Generic(x.i, int : 1, default : 0), "i is not int?");
+  _Static_assert(_Generic(x.j, int : 1, default : 0), "j is not int?");
----------------
aaron.ballman wrote:
> tahonermann wrote:
> > Top-level cv-qualifiers are ignored in generic selection expressions, so I'm not sure what these assertions are intended to ensure.
> I think this is the second time I've been caught by that. I keep expecting that the "no two associations can use compatible types" to make that situation an error.
> 
> I almost wonder if we should give a warning in cases where an association type is qualified (or is an array/function type rather than a decayed pointer)?
I was surprised when I first learned of this behavior too; it hobbles the utility of generic selection expressions in some cases.

A warning like you suggest does seem appropriate. I'm not aware of any way in which a cv-qualified or non-decayed association type can be  used in any useful manner (other than to show that a compiler is not behaving properly). If there is such a use, I would be interested in knowing what it is!

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125167/new/

https://reviews.llvm.org/D125167