lib/Lex/PPDirectives.cpp

1943   if (const MacroInfo *OtherMI=getMacroInfo(MacroNameTok.getIdentifierInfo())) {
1949       if (!OtherMI->isUsed() && OtherMI->isWarnIfUnused())
1950         Diag(OtherMI->getDefinitionLoc(), diag::pp_macro_not_used);
1954       if (OtherMI->isBuiltinMacro())
1958       else if (!OtherMI->isAllowRedefinitionsWithoutWarning() &&
1959                !MI->isIdenticalTo(*OtherMI, *this, /*Syntactic=*/LangOpts.MicrosoftExt)) {
1962         Diag(OtherMI->getDefinitionLoc(), diag::note_previous_definition);
1965     if (OtherMI->isWarnIfUnused())
1966       WarnUnusedMacroLocs.erase(OtherMI->getDefinitionLoc());