[clang] [Clang] Diagnose UB and emit error when identifier has both internal and external linkage (PR #192116)

[Aaron Ballman via cfe-commits]

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AaronBallman wrote:

You should change this status from `No` to `Yes` and be sure to update the row corresponding to N3410 in `clang/www/c_status.html`.

https://github.com/llvm/llvm-project/pull/192116