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

[John Brawn via Phabricator via cfe-commits]

john.brawn 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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aaron.ballman wrote:
> Why do we diagnose the undef but not the define?
After the undef the builtin macro definition no longer exists, so when Preprocessor::HandleDefineDirective checks for an existing definition to see if it's a builtin it doesn't find one.


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

https://reviews.llvm.org/D144654