Template:cpp/memory/owner before

Checks whether this precedes  in implementation defined owner-based (as opposed to value-based) order. The order is such that two smart pointers compare equivalent only if they are both empty or if they both own the same object, even if the values of the pointers obtained by get are different (e.g. because they point at different subobjects within the same object)

This ordering is used to make shared and weak pointers usable as keys in associative containers, typically through std.

Return value
if precedes,  otherwise. Common implementations compare the addresses of the control blocks.