19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.4 Class error_code [syserr.errcode]

19.5.4.4 Observers [syserr.errcode.observers]

int value() const noexcept;
Returns: val_.
const error_category& category() const noexcept;
Returns: *cat_.
error_condition default_error_condition() const noexcept;
Returns: category().default_error_condition(value()).
string message() const;
Returns: category().message(value()).
explicit operator bool() const noexcept;
Returns: value() != 0.