[humanrebar]

> ...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.

[nsonha]

> a boring global with careful access control

There is no such thing as "access control to global", unless you mean humans in code review, in that case, OK

[humanrebar]

You can have global linkage and private access control in several ways.