[PATCH] D133641: [Clang] [Sema] Ignore invalid multiversion function redeclarations

[Evgeny Shulgin via Phabricator via cfe-commits]

Izaron added a comment.

How the bug was working on this example:

  void foo() {}
  [[gnu::target("default")]] void foo() {}
  [[gnu::target("avx2")]] void foo() {}



1. Clang parses the definition of the `foo` function (line 1)
2. When parsing the second definition (line 2), Clang will delete `TargetAttr` in this function <https://github.com/llvm/llvm-project/blob/b51c6130efac2afd183ad71b81c16c713c10a1b5/clang/lib/Sema/SemaDecl.cpp#L2933>
3. Eventually Clang will mark both `foo`s as invalid.
4. When parsing the third definition (line 3), in the `CheckMultiVersionAdditionalDecl` method Clang is trying to compare `TargetAttr` of the 2nd and the 3rd `foo`: link <https://github.com/llvm/llvm-project/blob/b51c6130efac2afd183ad71b81c16c713c10a1b5/clang/lib/Sema/SemaDecl.cpp#L11100-L11101>.
5. The `CurTA` variable is equal to `nullptr` (because we deleted the attribute in the second step), so there is undefined behaviour.

I suggest to stop looking to invalid declarations.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D133641