22 Diagnostics library [diagnostics]

22.5 System error support [syserr]

22.5.2 Class error_­category [syserr.errcat]

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

constexpr error_category() noexcept;
Effects: Constructs an object of class error_­category.
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 provides a total ordering for pointers.
end note
]