[ClangDiagnostics] Silence warning about fallthrough after PrintFatalError

[xbolva00]

Summary

ClangDiagnosticsEmitter.cpp:1047:57: warning: this statement may fall through [-Wimplicit-fallthrough=]

Builder.PrintFatalError("Unknown modifier type: " + Modifier);
                        ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~

ClangDiagnosticsEmitter.cpp:1048:5: note: here

case MT_Select: {
              ^

[rtrieu]

Instead of adding a break, you should add a noreturn attribute to the PrintFatalError function. LLVM has the macro LLVM_ATTRIBUTE_NORETURN to do this. You can confirm that PrintFatalError is a noreturn function by seeing that it unconditionally calls llvm::PrintFatalError which itself is attributed with LLVM_ATTRIBUTE_NORETURN.

[xbolva00]

Add correct NORETURN attribute

[xbolva00]

Ok?

[rtrieu]

lgtm

utils/TableGen/ClangDiagnosticsEmitter.cpp

ModifierType ModType = llvm::StringSwitch<ModifierType>{Modifier}
                                .Case("objcclass", MT_ObjCClass)
                                .Case("objcinstance", MT_ObjCInstance)
                                .Case("", MT_Placeholder)
                                .Default(MT_Unknown);
 
     switch (ModType) {
     case MT_Unknown:
       Builder.PrintFatalError("Unknown modifier type: " + Modifier);
+      break;
     case MT_Select: {
       SelectPiece *Select = New<SelectPiece>(MT_Select);
       do {
         Text = Text.drop_front(); // '{' or '|'
         Select->Options.push_back(parseDiagText(Text, true));
         assert(!Text.empty() && "malformed %select");
       } while (Text.front() == '|');
       // Drop the trailing '}'.