Merge fixes from trunk.

src/nvcore/StrLib.h

@@ -14,7 +14,7 @@ namespace nv
 
 	uint strHash(const char * str, uint h) NV_PURE;
 
-	/// String hash vased on Bernstein's hash.
+	/// String hash based on Bernstein's hash.
 	inline uint strHash(const char * data, uint h = 5381)
 	{
 		uint i;
@@ -213,9 +213,12 @@ namespace nv
 		/// Implement value semantics.
 		String & operator=( const String & str )
 		{
-			release();
-			data = str.data;
-			addRef();
+			if (str.data != data)
+			{
+				release();
+				data = str.data;
+				addRef();
+			}
 			return *this;
 		}