Block subclassing

objectivec/GPBBootstrap.h

@@ -115,6 +115,11 @@
 // Meant to be used internally by generated code.
 #define GPB_METHOD_FAMILY_NONE __attribute__((objc_method_family(none)))
 
+// Prevent subclassing of generated proto classes.
+#ifndef GPB_FINAL
+#define GPB_FINAL __attribute__((objc_subclassing_restricted))
+#endif  // GPB_FINAL
+
 // ----------------------------------------------------------------------------
 // These version numbers are all internal to the ObjC Protobuf runtime; they
 // are used to ensure compatibility between the generated sources and the

objectivec/Tests/GPBMessageTests+ClassNames.m

@@ -38,14 +38,14 @@
 #import "GPBRootObject_PackagePrivate.h"
 
 // Support classes for tests using old class name (vs classrefs) interfaces.
-@interface MessageLackingClazzRoot : GPBRootObject
+GPB_FINAL @interface MessageLackingClazzRoot : GPBRootObject
 @end
 
 @interface MessageLackingClazzRoot (DynamicMethods)
 + (GPBExtensionDescriptor *)ext1;
 @end
 
-@interface MessageLackingClazz : GPBMessage
+GPB_FINAL @interface MessageLackingClazz : GPBMessage
 @property(copy, nonatomic) NSString *foo;
 @end
 

src/google/protobuf/compiler/objectivec/objectivec_file.cc

@@ -303,7 +303,7 @@ void FileGenerator::GenerateHeader(io::Printer *printer) {
       " * which is a @c GPBExtensionRegistry that includes all the extensions defined by\n"
       " * this file and all files that it depends on.\n"
       " **/\n"
-      "@interface $root_class_name$ : GPBRootObject\n"
+      "GPB_FINAL @interface $root_class_name$ : GPBRootObject\n"
       "@end\n"
       "\n",
       "root_class_name", root_class_name_);

src/google/protobuf/compiler/objectivec/objectivec_message.cc

@@ -334,7 +334,7 @@ void MessageGenerator::GenerateMessageHeader(io::Printer* printer) {
   }
 
   printer->Print(
-      "$comments$$deprecated_attribute$@interface $classname$ : GPBMessage\n\n",
+      "$comments$$deprecated_attribute$GPB_FINAL @interface $classname$ : GPBMessage\n\n",
       "classname", class_name_,
       "deprecated_attribute", deprecated_attribute_,
       "comments", message_comments);