c++ - 在 Raspbian 上使用 C++ 线程，无法编译

Question

我正在尝试为我的 Raspberry Pi 2 制作一个简单的 TCP 服务器程序。我已经制作了初始服务器代码并且它可以工作，但是后来，我尝试专门为服务器实现一个线程但我还没有从那时起就可以编译了。

#include <iostream>
#include <thread>
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

void error(const char *msg)
{
    perror(msg);
    exit(1);
}

int serverTask(int port){
    int n;
    char buffer[256];
    /* Socket File Descriptors */
    int socketFd, socketFdNew;
    socklen_t clientLength;

    struct sockaddr_in serverAddress, clientAddress;

    /* TCP Socket */
    socketFd = socket(AF_INET, SOCK_STREAM, 0);
    if(socketFd < 0){
        error("ERROR opening socket\n");
    }

    /* Fills serverAddress with zeroes */
    bzero((char *) &serverAddress, sizeof(serverAddress));

    /* ServerAddress configuration */
    serverAddress.sin_family = AF_INET;
    serverAddress.sin_addr.s_addr = INADDR_ANY;
    serverAddress.sin_port = htons(port);

    /* Biding socket to server address */
    if(bind(socketFd, (struct sockaddr *) &serverAddress,sizeof(serverAddress)) < 0){
        error("ERROR on binding");
    }

    /* Listen for incoming connections, 5 is the number of queued devices */
    listen(socketFd,5);

    /* accept freezes the running thread until a client is found */
    clientLength = sizeof(clientAddress);
    socketFdNew = accept(socketFd, (struct sockaddr *) &clientAddress, &clientLength);
    if (socketFd < 0){
        error("ERROR on accept");
    }

    /* Fill buffer with zeroes */
    bzero(buffer,256);

    /* Reads up to 255 characters in the socket */
    n = read(socketFdNew, buffer, 255);
    if (n < 0){
        error("ERROR reading from socket");
    }

    printf("Received: %s\n",buffer);

    /* Responds with placeholder value */
    n = write(socketFdNew,"40.12\n",7);
    if (n < 0){
        error("ERROR writing to socket");
    }
    close(socketFdNew);
    close(socketFd);
    return 0;
}

int main()
{
    std::thread serverTask(7000);

    std::cout <<"Hello World!\n";

    serverTask.join();
    return 0;
}

我的第一次尝试只是像使用任何其他代码一样使用 g++ -Wall -o "main""main.cpp"

构建代码

这让我出现了以下错误:

In file included from /usr/include/c++/4.6/thread:35:0, from main.cpp:2: /usr/include/c++/4.6/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. main.cpp: In function 'int main()': main.cpp:79:2: error: 'thread' is not a member of 'std' main.cpp:79:14: error: expected ';' before 'serverTask' main.cpp:84:13: error: request for member 'join' in 'serverTask', which is of non-class type 'int(int)' Compilation failed.

然后我尝试使用 C++11，所以我用 g++ -Wall -std=c++0x -pthread -o "main""main.cpp" 我得到了以下信息:

In file included from /usr/include/c++/4.6/thread:39:0, from main.cpp:2: /usr/include/c++/4.6/functional: In member function 'void std::_Bind_result<_Result, _Functor(_Bound_args ...)>::__call(std::tuple<_Args ...>&&, std::_Index_tuple<_Indexes ...>, typename std::_Bind_result<_Result, _Functor(_Bound_args ...)>::__enable_if_void<_Res>::type) [with _Res = void, _Args = {}, int ..._Indexes = {}, _Result = void, _Functor = int, _Bound_args = {}, typename std::_Bind_result<_Result, _Functor(_Bound_args ...)>::__enable_if_void<_Res>::type = int]': /usr/include/c++/4.6/functional:1378:24: instantiated from 'std::_Bind_result<_Result, _Functor(_Bound_args ...)>::result_type std::_Bind_result<_Result, _Functor(_Bound_args ...)>::operator()(_Args&& ...) [with _Args = {}, _Result = void, _Functor = int, _Bound_args = {}, std::_Bind_result<_Result, _Functor(_Bound_args ...)>::result_type = void]' /usr/include/c++/4.6/thread:117:13: instantiated from 'void std::thread::_Impl<_Callable>::_M_run() [with _Callable = std::_Bind_result]' main.cpp:86:1: instantiated from here /usr/include/c++/4.6/functional:1287:4: error: '((std::_Bind_result*)this)->std::_Bind_result::_M_f' cannot be used as a function Compilation failed.

我最后的选择是安装 g++4.9。安装后，我尝试使用 g++-4.9 -Wall -std=gnu++0x -pthread -o "main""main.cpp" 得到以下结果:

In file included from /usr/include/c++/4.9/thread:39:0, from main.cpp:2: /usr/include/c++/4.9/functional: In instantiation of 'struct std::_Bind_simple': /usr/include/c++/4.9/thread:140:47: required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = int; _Args = {}]' main.cpp:79:29: required from here /usr/include/c++/4.9/functional:1665:61: error: no type named 'type' in 'class std::result_of' typedef typename result_of<_Callable(_Args...)>::type result_type; ^ /usr/include/c++/4.9/functional:1695:9: error: no type named 'type' in 'class std::result_of' _M_invoke(_Index_tuple<_Indices...>) ^ Compilation failed.

现在我很困惑，我不知道我做错了什么。

更新 1:尝试使用更简单的代码

#include <iostream>
#include <thread>
#include <stdio.h>


int serverTask(int port){
    return 0;
}

int main()
{
    std::thread serverTask(7000);


    std::cout <<"Hello World!\n";

    serverTask.join();
    return 0;
}

结果还是一样:

g++-4.9 -Wall -std=gnu++0x -pthread -o "test" "test.cpp" (in directory: /home/pi/TempServer) In file included from /usr/include/c++/4.9/thread:39:0, from test.cpp:2: /usr/include/c++/4.9/functional: In instantiation of 'struct std::_Bind_simple': /usr/include/c++/4.9/thread:140:47: required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = int; _Args = {}]' test.cpp:12:29: required from here /usr/include/c++/4.9/functional:1665:61: error: no type named 'type' in 'class std::result_of' typedef typename result_of<_Callable(_Args...)>::type result_type; ^ /usr/include/c++/4.9/functional:1695:9: error: no type named 'type' in 'class std::result_of' _M_invoke(_Index_tuple<_Indices...>) ^ Compilation failed.

Answer 1

这一行:

std::thread serverTask(7000);

声明了一个名为 serverTask 的变量，您尝试传递 7000 作为要在线程中运行的函数的名称。但是 7000 不是函数。不幸的是，g++ 在这里给出了非常神秘的错误消息。

你的意思可能是:

std::thread foo(serverTask, 7000);

使用函数调用 serverTask(7000) 启动一个线程。