[PATCH] D133574: [C2x] reject type definitions in offsetof

[YingChi Long via Phabricator via cfe-commits]

inclyc updated this revision to Diff 461463.
inclyc added a comment.

Switch back to RAIIObject.

Currently clang could not generate diagnostic messages for nested definitions
in C++. I believe using RAIIObject here is logically correct, but in C++ mode,
`ActOnTag` returns `nullptr`, and the comment says

> We can't recover well from the cases where we make the type anonymous



  /* SemaDecl.cpp Sema::ActOnTag Ln 17189 */
  // In C++, don't return an invalid declaration. We can't recover well from
  // the cases where we make the type anonymous.
  if (Invalid && getLangOpts().CPlusPlus) {
    if (New->isBeingDefined())
      if (auto RD = dyn_cast<RecordDecl>(New))
        RD->completeDefinition();
    return nullptr;
  } else if (SkipBody && SkipBody->ShouldSkip) {
    return SkipBody->Previous;
  } else {
    return New;
  }

I believe the state "ParsingBuiltinOffsetof" is correctly passed into
`ParseCXXMemberSpecification` (parsing nested definition), and if clang
recovers invalid declaration in the furture, nested definitions will be caught.

  if (TUK == Sema::TUK_Definition) {
    assert(Tok.is(tok::l_brace) ||
           (getLangOpts().CPlusPlus && Tok.is(tok::colon)) ||
           isClassCompatibleKeyword());
    if (SkipBody.ShouldSkip)
      SkipCXXMemberSpecification(StartLoc, AttrFixitLoc, TagType,
                                 TagOrTempResult.get());
    else if (getLangOpts().CPlusPlus)
      ParseCXXMemberSpecification(StartLoc, AttrFixitLoc, attrs, TagType,
                                  TagOrTempResult.get());  // <----  nullptr, nested declaration skipped
    else {
      Decl *D =
          SkipBody.CheckSameAsPrevious ? SkipBody.New : TagOrTempResult.get();
      // Parse the definition body.
      ParseStructUnionBody(StartLoc, TagType, cast<RecordDecl>(D));
      if (SkipBody.CheckSameAsPrevious &&
          !Actions.ActOnDuplicateDefinition(TagOrTempResult.get(), SkipBody)) {
        DS.SetTypeSpecError();
        return;
      }
    }
  }


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133574/new/

https://reviews.llvm.org/D133574

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/include/clang/Parse/Parser.h
  clang/include/clang/Parse/RAIIObjectsForParser.h
  clang/include/clang/Sema/Sema.h
  clang/lib/Parse/ParseDeclCXX.cpp
  clang/lib/Parse/ParseExpr.cpp
  clang/lib/Sema/SemaDecl.cpp
  clang/test/Parser/declarators.c
  clang/test/Sema/offsetof.c
  clang/test/SemaCXX/offsetof.cpp

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