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

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

It looks like there's still relevant precommit CI failures: `clang-tidy/checkers/readability/identifier-naming-case-violation.cpp` looked related to this patch.



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Comment at: clang/lib/Lex/PPDirectives.cpp:3189-3192
+    if ((MI->isBuiltinMacro() ||
+         SourceMgr.isWrittenInBuiltinFile(MI->getDefinitionLoc())) &&
+        !(getLangOpts().ObjC && isObjCProtectedMacro(II)))
+      Diag(MacroNameTok, diag::ext_pp_undef_builtin_macro);
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john.brawn wrote:
> aaron.ballman wrote:
> > Should this diagnostic be suppressed in a system header on the assumption that system headers are part of the implementation and thus free to undefine/redefine macros at will?
> It's already suppressed. ShowInSystemHeader in the Diagnostic tablegen class determines if a diagnostic is shown when it happens in a system header, and it's false by default for warnings.
Ah, good point!


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D144654/new/

https://reviews.llvm.org/D144654