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

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


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Comment at: clang/test/Preprocessor/macro-reserved.cpp:15
 
-#undef __cplusplus
+#undef __cplusplus // expected-warning {{undefining builtin macro}}
 #define __cplusplus
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Why do we diagnose the undef but not the define?


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

https://reviews.llvm.org/D144654