Error ioctl was not declared in this scope

Thread: Qt c++ open && ioctl

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I have get gcc8.2 on aliyun Centos7, but when I get gdb-8.2 and use
./configure
make
then it occur compile error in ser-tcp.c. Here are error infos:

ser-tcp.c:64:13: error: conflicting declaration ‘typedef int socklen_t’
 typedef int socklen_t;
         ^~~~~~~~~
In file included from build-gnulib/import/unistd.h:40,
             from ./gnulib/import/pathmax.h:42,
             from ./common/common-defs.h:84,
             from defs.h:28,
             from ser-tcp.c:20:
/usr/include/unistd.h:274:21: note: previous declaration as ‘typedef __socklen_t socklen_t’
 typedef __socklen_t socklen_t;
                 ^~~~~~~~~
ser-tcp.c: In function ‘int net_open(serial*, const char*)’:
ser-tcp.c:223:19: error: ‘FIONBIO’ was not declared in this scope
   ioctl (scb->fd, FIONBIO, &ioarg);
               ^~~~~~~
ser-tcp.c:223:3: error: ‘ioctl’ was not declared in this scope
   ioctl (scb->fd, FIONBIO, &ioarg);
   ^~~~~

As for gcc-compiler, first I install a gcc-4.8.5 by default from yum.Then download gcc-8.2 and compile and replace.
Here are my gcc-8.2 -v infos:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/8.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-8.2.0/configure --enable-checking=release --enable- languages=c,c++ --disable-multilib
Thread model: posix
gcc version 8.2.0 (GCC) 

By the way, it’s not because of not including header, needed header was divided by Macro in the code.The question is why the macro not right in compiling.

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <sys/socket.h>
#include <sys/unistd.h>
#include <sys/types.h>
#include <sys/errno.h>
#include <netinet/in.h>
#include <signal.h>
#include <iostream>
#include <thread>

using namespace std;

#define BUFFSIZE 2048
#define DEFAULT_PORT 4001    //
#define MAXLINK 2048

void connecter()
{
    printf("Listening...n");
    while (true)
    {
        signal(SIGINT, stopServerRunning);    // 
        // 
        connfd = accept(sockfd, NULL, NULL);
        if (-1 == connfd)
        {
            printf("Accept error(%d): %sn", errno, strerror(errno));
            return -1;
        }
    }
}

void listener()
{
    while(true)
    {
        bzero(buff, BUFFSIZE);
        //
        recv(connfd, buff, BUFFSIZE - 1, 0);
        // 
        printf("клиент: %sn", buff);
        //
        send(connfd, buff, strlen(buff), 0);
    }
}

void sender()
{
    while(true)
    {
        printf("Please input: ");
        scanf("%s", buff);
        send(connfd, buff, strlen(buff), 0);
        bzero(buff, sizeof(buff));
        recv(connfd, buff, BUFFSIZE - 1, 0);
        printf("recv: %sn", buff);
    }
}

int sockfd, connfd; 
void stopServerRunning(int p)
{
    close(sockfd);
    printf("Close Servern");
    exit(0);
}
int main()
{
    struct sockaddr_in servaddr;
    char buff[BUFFSIZE];
    //
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == sockfd)
    {
        printf("Create socket error(%d): %sn", errno, strerror(errno));
        return -1;
    }
    // 
    // 
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(DEFAULT_PORT);
    if (-1 == bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)))
    {
        printf("Bind error(%d): %sn", errno, strerror(errno));
        return -1;
    }
    // 
    //
    if (-1 == listen(sockfd, MAXLINK))
    {
        printf("Listen error(%d): %sn", errno, strerror(errno));
        return -1;
    }
    
    while(true)
    {
        thread my_thread(connecter);
        if(connfd == true)
            break;
    }

    thread my_thread(connecter);
    thread my_thread(listener);
    thread my_thread(sender);

    return 0;
}

}

это исходный код программы, хотел написать что-то вроде чата на сокетах. Я попытался скомпилировать код, но он мне выдал несколько ошибок «was not declared in this scope». Вот вывод компилятора:

server.cpp: In function ‘void connecter()’:
server.cpp:24:24: error: ‘stopServerRunning’ was not declared in this scope
   24 |         signal(SIGINT, stopServerRunning);    // Это предложение используется для выключения сервера при вводе Ctrl + C
      | 

server.cpp:26:9: error: ‘connfd’ was not declared in this scope
   26 |         connfd = accept(sockfd, NULL, NULL);
      |         ^~~~~~

server.cpp:26:25: error: ‘sockfd’ was not declared in this scope; did you mean ‘socket’?
   26 |         connfd = accept(sockfd, NULL, NULL);
      |                         ^~~~~~
      |                         socket

server.cpp: In function ‘void listener()’:
server.cpp:39:15: error: ‘buff’ was not declared in this scope
   39 |         bzero(buff, BUFFSIZE);
      |               ^~~~

server.cpp:41:14: error: ‘connfd’ was not declared in this scope
   41 |         recv(connfd, buff, BUFFSIZE - 1, 0);
      |              ^~~~~~

server.cpp: In function ‘void sender()’:
server.cpp:54:21: error: ‘buff’ was not declared in this scope
   54 |         scanf("%s", buff);
      |                     ^~~~

server.cpp:55:14: error: ‘connfd’ was not declared in this scope
   55 |         send(connfd, buff, strlen(buff), 0);
      |              ^~~~~~

я думаю, что все эти ошибки идут из одной проблемы, но не могу понять откуда

Example

This error happens if a unknown object is used.

Variables

Not compiling:

#include <iostream>

int main(int argc, char *argv[])
{
    {
        int i = 2;
    }

    std::cout << i << std::endl; // i is not in the scope of the main function

    return 0;
}

Fix:

#include <iostream>

int main(int argc, char *argv[])
{
    {
        int i = 2;
        std::cout << i << std::endl;
    }

    return 0;
}

Functions

Most of the time this error occurs if the needed header is not
included (e.g. using std::cout without #include <iostream>)

Not compiling:

#include <iostream>

int main(int argc, char *argv[])
{
    doCompile();

    return 0;
}

void doCompile()
{
    std::cout << "No!" << std::endl;
}

Fix:

#include <iostream>

void doCompile(); // forward declare the function

int main(int argc, char *argv[])
{
    doCompile();

    return 0;
}

void doCompile()
{
    std::cout << "No!" << std::endl;
}

Or:

#include <iostream>

void doCompile() // define the function before using it
{
    std::cout << "No!" << std::endl;
}

int main(int argc, char *argv[])
{
    doCompile();

    return 0;
}

Note: The compiler interprets the code from top to bottom (simplification). Everything must be at least declared (or defined) before usage.

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