[PATCH] D144654: [Lex] Warn when defining or undefining any builtin macro

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

This seems to cause precommit CI failures that should be addressed, and it should also have a release note about the fix.

Also, should this cover things like `clang -U__cplusplus -D__STDC__=1 foo.cpp` as well?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D144654/new/

https://reviews.llvm.org/D144654