One Door Problem

A colleague proposes using a Singleton for a logging service, arguing that there should only ever be one logger. Which of the following is the strongest design argument against this approach?

Singletons violate the Open-Closed Principle because you cannot extend them

Singletons use heap memory, which is slower than stack allocation

Singletons introduce hidden global state and make unit testing difficult

Singletons are incompatible with multithreaded programs