Merge pull request swiftlang#20912 from dnadoba/master

Refuse to import C arrays that are longer than 4096

Author: jrose-apple

lib/ClangImporter/ImportType.cpp

@@ -480,10 +480,17 @@ namespace {
           Bridgeability::None);
       if (!elementType)
         return Type();
+
+      auto size = type->getSize().getZExtValue();
+      // An array of size N is imported as an N-element tuple which
+      // takes very long to compile. We chose 4096 as the upper limit because
+      // we don't want to break arrays of size PATH_MAX. 
+      if (size > 4096)
+        return Type();
 
       TupleTypeElt elt(elementType);
       SmallVector<TupleTypeElt, 8> elts;
-      for (size_t i = 0, size = type->getSize().getZExtValue(); i < size; ++i)
+      for (size_t i = 0; i < size; ++i)
         elts.push_back(elt);
 
       return TupleType::get(elts, elementType->getASTContext());