19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.2 Class error_­category [syserr.errcat]

19.5.2.3 Non-virtual members [syserr.errcat.nonvirtuals]

bool operator==(const error_category& rhs) const noexcept;
Returns: this == &rhs.
strong_ordering operator<=>(const error_category& rhs) const noexcept;
Returns: compare_­three_­way()(this, &rhs).
Note
:
compare_­three_­way ([cmp.object]) provides a total ordering for pointers.
— end note
 ]