[PATCH] D45884: [Sema] Fix parsing of anonymous union in language linkage specification

[Volodymyr Sapsai via Phabricator via cfe-commits]

vsapsai added a comment.

For the record, DR154: Anonymous unions in unnamed namespaces <http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_closed.html#154> is relevant here.



================
Comment at: Sema/SemaDecl.cpp:4654-4656
+      while (OwnerScope->getDeclKind() == Decl::LinkageSpec) {
+        OwnerScope = OwnerScope->getParent();
+      }
----------------
Looks like `DeclContext::isTransparentContext()` might be relevant here. At least I was able to get the assertion failure

> Assertion failed: (II && "Attempt to mangle unnamed decl."), function getMangledNameImpl, file llvm-project/clang/lib/CodeGen/CodeGenModule.cpp, line 913.

for
```lang=c++
// clang -std=c++17 -fmodules-ts test-modules.cpp

export module M;
export {
    union {
        int int_val;
        float float_val;
    };
}
```

Also based on `isTransparentContext()` usage, inline namespaces can cause problems. Currently, there are no problems, we have the error

> error: anonymous unions at namespace or global scope must be declared 'static'

and there are no negative consequences (as far as I can tell). According to my bad standard knowledge that should be OK (haven't found non-static anonymous unions to be allowed in this case).


================
Comment at: Sema/SemaDecl.cpp:4659
       if (DS.getStorageClassSpec() != DeclSpec::SCS_static &&
-          (isa<TranslationUnitDecl>(Owner) ||
-           (isa<NamespaceDecl>(Owner) &&
-            cast<NamespaceDecl>(Owner)->getDeclName()))) {
+          (isa<TranslationUnitDecl>(OwnerScope) ||
+           (isa<NamespaceDecl>(OwnerScope) &&
----------------
Checked if we need to do the same change s/Owner/OwnerScope/ elsewhere in this method and looks like it is not required. We care if the owner is a Record and we don't allow linkage specification in classes, so skipping linkage scopes doesn't give us anything.


Repository:
  rC Clang

https://reviews.llvm.org/D45884