std::errc

 

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std::errc

非成员函数

make_error_code

make_error_condition

帮助类

is_error_condition_enum

 

在标头 <system_error> 定义
enum class errc;		(C++11 起)

有作用域枚举 std::errc 定义对应于 POSIX 错误码的可移植错误条件。

成员常量

名称	等价的 POSIX 错误
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 (弃用)	ENODATA
no_message	ENOMSG
no_protocol_option	ENOPROTOOPT
no_space_on_device	ENOSPC
no_stream_resources (弃用)	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 (弃用)	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 (弃用)	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

非成员函数

make_error_code(std::errc) (C++11)	为 errc 枚举 e 创建错误码值 (函数)
make_error_condition(std::errc) (C++11)	为 errc 值 e 创建错误条件 (函数)

辅助类

is_error_condition_enum<std::errc> (C++11)

扩充 std::is_error_condition_enum 类型特性，以鉴别 errc 值为某种错误条件 (函数模板)

示例

运行此代码

#include <filesystem>
#include <fstream>
#include <iomanip>
#include <iostream>
#include <string>
#include <system_error>
#include <thread>
 
void print_error(const std::string& details, std::error_code error_code)
{
    std::string value_name;
    if (error_code == std::errc::invalid_argument)
        value_name = "std::errc::invalid_argument";
    if (error_code == std::errc::no_such_file_or_directory)
        value_name = "std::errc::no_such_file_or_directory";
    if (error_code == std::errc::is_a_directory)
        value_name = "std::errc::is_a_directory";
    if (error_code == std::errc::permission_denied)
        value_name = "std::errc::permission_denied";
 
    std::cout << details << ":\n  "
              << std::quoted(error_code.message())
              << " (" << value_name << ")\n\n";
}
 
void print_errno(const std::string& details, int errno_value = errno)
{
    print_error(details, std::make_error_code(std::errc(errno_value)));
}
 
int main()
{
    std::cout << "脱离不是线程的线程...\n";
    try
    {
        std::thread().detach();
    }
    catch (const std::system_error& e)
    {
        print_error("脱离空线程时报错", e.code());
    }
 
    std::cout << "打开不存在的文件...\n";
    std::ifstream nofile{"nonexistent-file"};
    if (!nofile.is_open())
        print_errno("为读取打开不存在的文件时报错");
 
    std::cout << "将目录当作文件进行读取...\n";
    std::filesystem::create_directory("dir");
    std::ifstream dir_stream{"dir"};
    [[maybe_unused]] char c = dir_stream.get();
    if (!dir_stream.good())
        print_errno("从目录读取数据时报错");
 
    std::cout << "为写入打开只读文件...\n";
    std::fstream{"readonly-file", std::ios::out};
    std::filesystem::permissions("readonly-file", std::filesystem::perms::owner_read);
    std::fstream write_readonly("readonly-file", std::ios::out);
    if (!write_readonly.is_open())
        print_errno("为写入打开只读文件时报错");
}

可能的输出：

脱离不是线程的线程...
脱离空线程时报错:
  "Invalid argument" (std::errc::invalid_argument)
 
打开不存在的文件...
为读取打开不存在的文件时报错:
  "No such file or directory" (std::errc::no_such_file_or_directory)
 
将目录当作文件进行读取...
从目录读取数据时报错:
  "Is a directory" (std::errc::is_a_directory)
 
为写入打开只读文件...
为写入打开只读文件时报错:
  "Permission denied" (std::errc::permission_denied)

缺陷报告

下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。

缺陷报告	应用于	出版时的行为	正确行为
LWG 3869	C++11	成员常量 no_message_available、no_stream_resources、 not_a_stream 和 stream_timeout 涉及了废弃的 POSIX STREAMS API	弃用这些成员常量

参阅

error_code (C++11)	保有依赖于平台的错误码 (类)
error_condition (C++11)	保有可移植的错误码 (类)