[PATCH] D155895: Anonymous unions should be transparent wrt `[[clang::trivial_abi]]`.

[Łukasz Anforowicz via Phabricator via cfe-commits]

lukasza added inline comments.


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Comment at: clang/lib/Sema/SemaDeclCXX.cpp:10299
 
   if (!HasNonDeletedCopyOrMoveConstructor()) {
     PrintDiagAndRemoveAttr(0);
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I tried to change this condition to `!RD.isAnonymousStructOrUnion() && !HasNonDeletedCopyOrMoveConstructor()` but it seems that at this point `isAnonymousStructOrUnion` doesn't yet work because `setAnonymousStructOrUnion` is called at a later point.


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Comment at: clang/lib/Sema/SemaDeclCXX.cpp:10350
   }
 }
 
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Alternative fix I've considered:
1.1. `setHasTrivialSpecialMemberForCall` for anonymous unions *if* their `DeclContext` is trivial.
1.2. Don't check `!HasNonDeletedCopyOrMoveConstructor()` for anonymous unions.

I don't know how to do 1.1 - this seems like a chicken-and-egg problem.  We can't know if `DeclContext` is trivial until we check `checkIllFormedTrivialABIStruct`, but when `checkIllFormedTrivialABIStruct` checks fields it requires that the triviality of the anonymous union is already known.

I don't know how to do 1.2 - changing the condition above to `!RD.isAnonymousStructOrUnion() && !HasNonDeletedCopyOrMoveConstructor()` doesn't work because at that point `isAnonymousStructOrUnion` doesn't yet work because `setAnonymousStructOrUnion` is called at a later point.




Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D155895/new/

https://reviews.llvm.org/D155895