aaron.ballman added inline comments.
================ Comment at: clang/lib/Parse/ParseDeclCXX.cpp:2069-2078 + if (auto *TagDecl = Actions.ActOnTag( + getCurScope(), TagType, TUK, StartLoc, SS, Name, NameLoc, attrs, AS, + DS.getModulePrivateSpecLoc(), TParams, Owned, IsDependent, + SourceLocation(), false, clang::TypeResult(), + DSC == DeclSpecContext::DSC_type_specifier, + DSC == DeclSpecContext::DSC_template_param || + DSC == DeclSpecContext::DSC_template_type_arg, ---------------- hokein wrote: > hokein wrote: > > aaron.ballman wrote: > > > I think this is the wrong approach to fixing the issue. None of the other > > > assignments to `TagOrTempResult` test for nullptr first, such as: > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2037 > > > and > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2029. > > > > > > An `ActionResult` can be both valid/invalid *and* usable/unusable (and a > > > `DeclResult` is a kind of `ActionResult`). When it's assigned *any > > > pointer value* (including nullptr), it's a valid `ActionResult` but it's > > > not a usable `ActionResult` > > > (https://github.com/llvm/llvm-project/blob/main/clang/include/clang/Sema/Ownership.h#L166). > > > > > > I think the correct fix is to find the places assuming a valid > > > `ActionResult` means a nonnull pointer from `get()`, such as > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2121 > > > and switch them over to looking for a usable `ActionResult` instead. > > Thanks for the comment! > > > > > None of the other assignments to TagOrTempResult test for nullptr first > > > > I think the problem here is: > > - most of the `ActOn*` methods return a `DeclResult` (and inside these > > method implementations, they return an Invalid `DeclResult` if the Decl is > > nullptr), so `TagOrTempResult = Actions.ActOn*` is a fine pattern. > > - Only two exceptions `ActOnTagDecl` and `ActOnTemplatedFriendTag`, they > > return a `Decl*`, so the `TagOrTempResult = Action.ActOn*` is a very > > suspicious pattern. (IMO, they're not intentional, likely bugs). > > > > > such as: > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2037 > > > and > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2029. > > > > The first one is the other exception; the second one is not > > (ActOnExplicitInstantiation returns a `DeclResult`). > > > > > I think the correct fix is to find the places assuming a valid > > > ActionResult means a nonnull pointer from get(), such as > > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2121 > > > and switch them over to looking for a usable ActionResult instead. > > > > This is one of the solutions. But instead of justifying every places of > > DeclResult, I think we should fix the two exception places (by adding the > > nullptr check in > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2037 > > and > > https://github.com/llvm/llvm-project/blob/main/clang/lib/Parse/ParseDeclCXX.cpp#L2069), > > what do you think? > I have updated the patch to check nullptr for ActOnTemplatedFriendTag as > well. Let me know what you think (I'm also happy to do the change). Actually, I think the best solution is to make those APIs return a correctly constructed (invalid) `DeclResult` rather than a `Decl *` that turns into a valid-but-unusable `DeclResult`. I tried the change out locally and it seems to have the same fallout as your changes with only a small amount of extra work involved. I have this done locally, would you like me to go ahead and clean it up to commit it or hand a patch off to you to finish? Or do you think that's not a good approach? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D141580/new/ https://reviews.llvm.org/D141580 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
