[llvm] [clang-cl] Fix value of __FUNCTION__ and __FUNC__ in MSVC mode for c++. (PR #66120)

[Richard Dzenis via llvm-commits]

RIscRIpt wrote:

This implementation has bugs, see https://github.com/llvm/llvm-project/issues/66114#issuecomment-1732319259

https://github.com/llvm/llvm-project/pull/66120