> ...requiring/expectinv only one instance of a class to be available is obviously not an anti-pattern. I'll disagree. There are very few situations where rest

> ...requiring/expectinv only one instance of a class to be available is obviously not an anti-pattern. I'll disagree. There are very few situations where restricting class instantiation to one object both solves a problem and doesn't cause unneeded headaches. Almost always a boring global with careful access control is better. It provides a single object just as well without limiting options for future software engineering needs: testing, adding construction parameters, migration, gradual deprecation, etc. As to legitimate uses, anything with system scope can't be controlled within a process. And there are few things that inherently couldn't be instantiated twice that aren't better managed by the OS.