tahonermann added inline comments.
================ Comment at: clang/lib/Serialization/ASTReaderDecl.cpp:2925-2926 for (unsigned I = 0, E = readInt(); I != E; ++I) - Attrs.push_back(readAttr()); + if (auto *Attr = readAttr()) + Attrs.push_back(Attr); } ---------------- Interesting, this looks like a pre-existing issue. It looks like `readBTFTypeTagAttr()` in `clang/include/clang/Serialization/ASTRecordReader.h` has an assumption that `readAttr()` always returns non-null. I wonder if that should be modified to use `cast_or_null` rather than `cast`. I don't see any need to address that issue (if it actually exists) in this review though. ================ Comment at: clang/lib/Serialization/ASTWriter.cpp:4353 + // https://github.com/llvm/llvm-project/issues/56490 for example. + if (!A || (isa<PreferredNameAttr>(A) && Writer->isWritingNamedModules())) return Record.push_back(0); ---------------- ChuanqiXu wrote: > The `Writer->isWritingNamedModules()` part is necessary. Otherwise we would > break the > https://github.com/llvm/llvm-project/blob/main/clang/test/PCH/decl-attrs.cpp > test. The reason why the bug is not found by the user of PCH or clang modules > is that a header generally would be guarded by `#ifndef ... #define` fashion. > And if we remove the guard, the compiler would emit an error for duplicated > definition. So the problem only lives in C++20 Named Modules. Correct me if I'm mistaken, but I think this issue only occurs because, in the test, both modules have the problematic declarations in the global module fragment; thus creating duplicate definitions that have to be merged which then exposes the ODR mismatch. I'm suspicious that this actually fixes all possible scenarios. For example: //--- X1.cpp #include "foo.h" import A; //--- X2.cpp import A; #include "foo.h" I would expect the proposed change to cause an ODR issue in these scenarios since the definition from the module still needs to be merged in non-modular TUs, but now the imported module will lack the attribute present in the non-modular TUs. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D130331/new/ https://reviews.llvm.org/D130331 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
