virtual const char* name() const noexcept = 0;
virtual error_condition default_error_condition(int ev) const noexcept;
virtual bool equivalent(int code, const error_condition& condition) const noexcept;
virtual bool equivalent(const error_code& code, int condition) const noexcept;
virtual string message(int ev) const = 0;
bool operator==(const error_category& rhs) const noexcept;
strong_ordering operator<=>(const error_category& rhs) const noexcept;
virtual const char* name() const noexcept = 0;
virtual error_condition default_error_condition(int ev) const noexcept;
virtual bool equivalent(int code, const error_condition& condition) const noexcept;
virtual bool equivalent(const error_code& code, int condition) const noexcept;
const error_category& generic_category() noexcept;
const error_category& system_category() noexcept;
error_code() noexcept;
error_code(int val, const error_category& cat) noexcept;
template<class ErrorCodeEnum>
error_code(ErrorCodeEnum e) noexcept;
void assign(int val, const error_category& cat) noexcept;
template<class ErrorCodeEnum>
error_code& operator=(ErrorCodeEnum e) noexcept;
void clear() noexcept;
int value() const noexcept;
const error_category& category() const noexcept;
error_condition default_error_condition() const noexcept;
string message() const;
explicit operator bool() const noexcept;
error_code make_error_code(errc e) noexcept;
template<class charT, class traits>
basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const error_code& ec);
error_condition() noexcept;
error_condition(int val, const error_category& cat) noexcept;
template<class ErrorConditionEnum>
error_condition(ErrorConditionEnum e) noexcept;
void assign(int val, const error_category& cat) noexcept;
template<class ErrorConditionEnum>
error_condition& operator=(ErrorConditionEnum e) noexcept;
void clear() noexcept;
int value() const noexcept;
const error_category& category() const noexcept;
string message() const;
explicit operator bool() const noexcept;
bool operator==(const error_code& lhs, const error_code& rhs) noexcept;
bool operator==(const error_code& lhs, const error_condition& rhs) noexcept;
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept;
strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept;
strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
template<> struct hash<error_code>;
template<> struct hash<error_condition>;
system_error(error_code ec, const string& what_arg);
system_error(error_code ec, const char* what_arg);
system_error(error_code ec);
system_error(int ev, const error_category& ecat, const string& what_arg);
system_error(int ev, const error_category& ecat, const char* what_arg);
system_error(int ev, const error_category& ecat);
const error_code& code() const noexcept;
const char* what() const noexcept override;