19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.1 Class error_category [syserr.errcat]

19.5.1.3 Class error_category non-virtual members [syserr.errcat.nonvirtuals]

bool operator==(const error_category& rhs) const noexcept;

Returns: this == &rhs.

bool operator!=(const error_category& rhs) const noexcept;

Returns: !(*this == rhs).

bool operator<(const error_category& rhs) const noexcept;

Returns: less<const error_category*>()(this, &rhs).

Note: less ([comparisons]) provides a total ordering for pointers.  — end note ]