7.0 KiB
[syserr.errcode]
19 Diagnostics library [diagnostics]
19.5 System error support [syserr]
19.5.4 Class error_code [syserr.errcode]
19.5.4.1 Overview [syserr.errcode.overview]
The class error_code describes an object used to hold error code values, such as those originating from the operating system or other low-level application program interfaces.
[Note 1:
Class error_code is an adjunct to error reporting by exception.
â end note]
namespace std {class error_code {public:// [syserr.errcode.constructors], constructors error_code() noexcept; error_code(int val, const error_category& cat) noexcept; template error_code(ErrorCodeEnum e) noexcept; // [syserr.errcode.modifiers], modifiersvoid assign(int val, const error_category& cat) noexcept; template error_code& operator=(ErrorCodeEnum e) noexcept; void clear() noexcept; // [syserr.errcode.observers], observersint value() const noexcept; const error_category& category() const noexcept; error_condition default_error_condition() const noexcept; string message() const; explicit operator bool() const noexcept; private:int val_; // exposition onlyconst error_category* cat_; // exposition only}; // [syserr.errcode.nonmembers], non-member functions 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);}
19.5.4.2 Constructors [syserr.errcode.constructors]
error_code() noexcept;
Effects: Initializes val_ with 0 and cat_ with &system_category().
error_code(int val, const error_category& cat) noexcept;
Effects: Initializes val_ with val and cat_ with &cat.
template<class ErrorCodeEnum> error_code(ErrorCodeEnum e) noexcept;
Constraints: is_error_code_enum_v is true.
Effects: Equivalent to:error_code ec = make_error_code(e); assign(ec.value(), ec.category());
19.5.4.3 Modifiers [syserr.errcode.modifiers]
void assign(int val, const error_category& cat) noexcept;
Postconditions: val_ == val and cat_ == &cat.
template<class ErrorCodeEnum> error_code& operator=(ErrorCodeEnum e) noexcept;
Constraints: is_error_code_enum_v is true.
Effects: Equivalent to:error_code ec = make_error_code(e); assign(ec.value(), ec.category());
Returns: *this.
void clear() noexcept;
Postconditions: value() == 0 and category() == system_category().
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.
19.5.4.5 Non-member functions [syserr.errcode.nonmembers]
error_code make_error_code(errc e) noexcept;
Returns: error_code(static_cast(e), generic_category()).
template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const error_code& ec);
Effects: Equivalent to: return os << ec.category().name() << ':' << ec.value();