[ObjC] Mark classes that shouldn't be subclassed as such.
Several of the classes vended by the runtime don't really support subclassing,
so mark them as such to get compiler enforcement just in case.
PiperOrigin-RevId: 505221732
diff --git a/objectivec/GPBCodedInputStream.h b/objectivec/GPBCodedInputStream.h
index cbfaaf1..355c9db 100644
--- a/objectivec/GPBCodedInputStream.h
+++ b/objectivec/GPBCodedInputStream.h
@@ -83,6 +83,7 @@
*
* @note Subclassing of @c GPBCodedInputStream is NOT supported.
**/
+__attribute__((objc_subclassing_restricted))
@interface GPBCodedInputStream : NSObject
/**
