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Standard library header <system_error>

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< cpp‎ | header
 
 
 

This header is part of the error handling library.

Contents

Includes

(C++20)
Three-way comparison operator support [edit]

Classes

base class for error categories
(class) [edit]
holds a portable error code
(class) [edit]
(C++11)
the std::error_condition enumeration listing all standard <cerrno> macro constants
(class) [edit]
holds a platform-dependent error code
(class) [edit]
exception class used to report conditions that have an error_code
(class) [edit]
identifies a class as an error_code enumeration
(class template) [edit]
identifies an enumeration as an std::error_condition
(class template) [edit]
hash support for std::error_code
(class template specialization) [edit]
Forward declarations
Defined in header <functional>
(C++11)
hash function object
(class template) [edit]

Functions

identifies the generic error category
(function) [edit]
identifies the operating system error category
(function) [edit]
(removed in C++20)(removed in C++20)(C++20)
compares two error_codes
(function) [edit]
outputs the value and the category name to an output stream
(function) [edit]
constructs an std::errc error code
(function) [edit]
(removed in C++20)(removed in C++20)(C++20)
compares error_conditions and error_codes
(function) [edit]
constructs an std::errc error condition
(function) [edit]

[edit] Synopsis

#include <compare>
 
namespace std {
  class error_category;
  const error_category& generic_category() noexcept;
  const error_category& system_category() noexcept;
 
  class error_code;
  class error_condition;
  class system_error;
 
  template<class T>
    struct is_error_code_enum : public false_type {};
 
  template<class T>
    struct is_error_condition_enum : public false_type {};
 
  enum class errc {
    address_family_not_supported,       // EAFNOSUPPORT
    address_in_use,                     // EADDRINUSE
    address_not_available,              // EADDRNOTAVAIL
    already_connected,                  // EISCONN
    argument_list_too_long,             // E2BIG
    argument_out_of_domain,             // EDOM
    bad_address,                        // EFAULT
    bad_file_descriptor,                // EBADF
    bad_message,                        // EBADMSG
    broken_pipe,                        // EPIPE
    connection_aborted,                 // ECONNABORTED
    connection_already_in_progress,     // EALREADY
    connection_refused,                 // ECONNREFUSED
    connection_reset,                   // ECONNRESET
    cross_device_link,                  // EXDEV
    destination_address_required,       // EDESTADDRREQ
    device_or_resource_busy,            // EBUSY
    directory_not_empty,                // ENOTEMPTY
    executable_format_error,            // ENOEXEC
    file_exists,                        // EEXIST
    file_too_large,                     // EFBIG
    filename_too_long,                  // ENAMETOOLONG
    function_not_supported,             // ENOSYS
    host_unreachable,                   // EHOSTUNREACH
    identifier_removed,                 // EIDRM
    illegal_byte_sequence,              // EILSEQ
    inappropriate_io_control_operation, // ENOTTY
    interrupted,                        // EINTR
    invalid_argument,                   // EINVAL
    invalid_seek,                       // ESPIPE
    io_error,                           // EIO
    is_a_directory,                     // EISDIR
    message_size,                       // EMSGSIZE
    network_down,                       // ENETDOWN
    network_reset,                      // ENETRESET
    network_unreachable,                // ENETUNREACH
    no_buffer_space,                    // ENOBUFS
    no_child_process,                   // ECHILD
    no_link,                            // ENOLINK
    no_lock_available,                  // ENOLCK
    no_message_available,               // ENODATA
    no_message,                         // ENOMSG
    no_protocol_option,                 // ENOPROTOOPT
    no_space_on_device,                 // ENOSPC
    no_stream_resources,                // ENOSR
    no_such_device_or_address,          // ENXIO
    no_such_device,                     // ENODEV
    no_such_file_or_directory,          // ENOENT
    no_such_process,                    // ESRCH
    not_a_directory,                    // ENOTDIR
    not_a_socket,                       // ENOTSOCK
    not_a_stream,                       // ENOSTR
    not_connected,                      // ENOTCONN
    not_enough_memory,                  // ENOMEM
    not_supported,                      // ENOTSUP
    operation_canceled,                 // ECANCELED
    operation_in_progress,              // EINPROGRESS
    operation_not_permitted,            // EPERM
    operation_not_supported,            // EOPNOTSUPP
    operation_would_block,              // EWOULDBLOCK
    owner_dead,                         // EOWNERDEAD
    permission_denied,                  // EACCES
    protocol_error,                     // EPROTO
    protocol_not_supported,             // EPROTONOSUPPORT
    read_only_file_system,              // EROFS
    resource_deadlock_would_occur,      // EDEADLK
    resource_unavailable_try_again,     // EAGAIN
    result_out_of_range,                // ERANGE
    state_not_recoverable,              // ENOTRECOVERABLE
    stream_timeout,                     // ETIME
    text_file_busy,                     // ETXTBSY
    timed_out,                          // ETIMEDOUT
    too_many_files_open_in_system,      // ENFILE
    too_many_files_open,                // EMFILE
    too_many_links,                     // EMLINK
    too_many_symbolic_link_levels,      // ELOOP
    value_too_large,                    // EOVERFLOW
    wrong_protocol_type,                // EPROTOTYPE
  };
 
  template<> struct is_error_condition_enum<errc> : true_type {};
 
  // 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);
 
  // non-member functions
  error_condition make_error_condition(errc e) noexcept;
 
  // comparison functions
  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;
 
  // hash support
  template<class T> struct hash;
  template<> struct hash<error_code>;
  template<> struct hash<error_condition>;
 
  // system error support
  template<class T>
    inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
  template<class T>
    inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value;
}

[edit] Class std::error_category

namespace std {
  class error_category {
  public:
    constexpr error_category() noexcept;
    virtual ~error_category();
    error_category(const error_category&) = delete;
    error_category& operator=(const error_category&) = delete;
    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;
  };
 
  const error_category& generic_category() noexcept;
  const error_category& system_category() noexcept;
}

[edit] Class std::error_code

namespace std {
  class error_code {
  public:
    // constructors
    error_code() noexcept;
    error_code(int val, const error_category& cat) noexcept;
    template<class ErrorCodeEnum>
      error_code(ErrorCodeEnum e) noexcept;
 
    // modifiers
    void assign(int val, const error_category& cat) noexcept;
    template<class ErrorCodeEnum>
      error_code& operator=(ErrorCodeEnum e) noexcept;
    void clear() noexcept;
 
    // observers
    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;
 
  private:
    int val_;                   // exposition only
    const error_category* cat_; // exposition only
  };
 
  // 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);
}

[edit] Class std::error_condition

namespace std {
  class error_condition {
  public:
    // constructors
    error_condition() noexcept;
    error_condition(int val, const error_category& cat) noexcept;
    template<class ErrorConditionEnum>
      error_condition(ErrorConditionEnum e) noexcept;
 
    // modifiers
    void assign(int val, const error_category& cat) noexcept;
    template<class ErrorConditionEnum>
      error_condition& operator=(ErrorConditionEnum e) noexcept;
    void clear() noexcept;
 
    // observers
    int value() const noexcept;
    const error_category& category() const noexcept;
    string message() const;
    explicit operator bool() const noexcept;
 
  private:
    int val_;                   // exposition only
    const error_category* cat_; // exposition only
  };
}

[edit] Class std::system_error

namespace std {
  class system_error : public runtime_error {
  public:
    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;
  };
}