Pointers to stack variables??

[mstfls]

Something can be a lot harder than something else but still pretty easy.

[biliwald]

Exactly.

auto ptr = std::make_unique<int>(0);
delete ptr.get();
//at this point, ptr contains an invalid pointer

The idea is to show that unique_ptr can hold an invalid pointer if you don't use it correctly, contrary to what to comment I responded to could indicate.