19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.2 Header <system_error> synopsis [system.error.syn]

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#include <compare> // see [compare.syn] 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, // ENOMSG no_protocol_option, // ENOPROTOOPT no_space_on_device, // ENOSPC 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_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 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 {}; // [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); // [syserr.errcondition.nonmembers], non-member functions error_condition make_error_condition(errc e) noexcept; // [syserr.compare], comparison operator 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; // [syserr.hash], hash support template<class T> struct hash; template<> struct hash<error_code>; template<> struct hash<error_condition>; // [syserr], system error support template<class T> constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value; template<class T> constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value; }
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The value of each enum errc enumerator is the same as the value of the <cerrno> macro shown in the above synopsis.
Whether or not the <system_error> implementation exposes the <cerrno> macros is unspecified.
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The is_error_code_enum and is_error_condition_enum templates may be specialized for program-defined types to indicate that such types are eligible for class error_code and class error_condition implicit conversions, respectively.