Question of proper usage for F Macro Here are three use cases. Are all preferred or is the use of the F() macro pointless on some?

1.

Serial.println(F("some string"); // definitely useful here


2.

String str = F("some string");
Serial.println(str);


3.

int num = 5;
String str = F("some string with int ");
str += (String)num;
Serial.println(str);
Any time String is involved F() becomes pointless. Avoid String like the plague if you value your memory integrity.