[PATCH] D122820: [GH54588]Fix ItaniumMangler for NTTP unnamed unions w/ unnamed structs

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

Unfortunately, this initialization case does allow a situation where



================
Comment at: clang/lib/AST/ItaniumMangle.cpp:5561
+  // field represents an anonymous record type.
+  const CXXRecordDecl *RD = FD->getType()->getAsCXXRecordDecl();
+
----------------
Alas, bit-fields are also allowed to be anonymous.


================
Comment at: clang/lib/AST/ItaniumMangle.cpp:5576
+      "program to refer to the anonymous union, and there is therefore no need "
+      "to mangle its name. '");
+}
----------------
Unfortunately, I think class value mangling has a counter-example to this: you can have an anonymous struct or union which doesn't declare any named members but will of course nonetheless show up in the list of members in the enclosing class.  Code can even give it a non-zero initializer using list-initialization; that value can never be read, but it's there, and presumably it's part of uniquely determining a different template argument value and therefore needs to be mangled.

I don't know what we should do about this in the ABI, but we shouldn't crash in the compiler.


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  https://reviews.llvm.org/D122820/new/

https://reviews.llvm.org/D122820