select 的问题

 #include <errno.h>
 #include <string.h>
 #include <fcntl.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <sys/select.h>
 #include <netinet/tcp.h>
 #include <netinet/ip.h>
 #include <arpa/inet.h>
 #include <unistd.h>
 #include <stdio.h>

 int main(int argc, const char * argv[]) {
     int sock = socket(PF_INET, SOCK_STREAM, );
     if(sock == -){
         const char* str = strerror(errno);
         printf("socket: %s\n", str);
         return -;
     }

     int flags = fcntl(sock, F_GETFD, );
     flags |= O_NONBLOCK;
     fcntl(sock, F_SETFD, flags);

     char ch = ;
     setsockopt(sock, IPPROTO_TP, TCP_NODELAY, &ch, sizeof(ch));
     int value = ;
     setsockopt(sock, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value));

     struct sockaddr_in addr = {};
     addr.sin_family = AF_INET;
     addr.sin_port = htons();
     addr.sin_addr.s_addr = inet_addr("127.0.0.1");

     int ret = connect(sock, (struct sockaddr*)&addr, sizeof(addr));
     if(ret){
         int err = errno;
         if(err != EINPROGRESS && err != EWOULDBLOCK){
             const char* str = strerror(errno);
             printf("connect: %s\n", str);
             //return -1;    // 注释掉这里，后面 select 返回 1
         }

         int nfds = ;
         fd_set wset;
         FD_ZERO(&wset);
         FD_SET(sock, &wset);
         nfds = sock + ;

         struct timeval timeout;
         timeout.tv_sec = ;
         timeout.tv_usec = ;
         int n = select(nfds, , &wset, , &timeout);
         if(n > ){
             struct sockaddr in = {};
             socklen_t len = sizeof(in);
             int e = getpeername(sock, &in, &len);
             if(e){
                 int err = errno;
                 printf("getpeername: %s\n", strerror(err));
             }
         }

     }

     return ;
 }

select 一个 "connection refused" 的 socket, socket 居然状态可写。。

原代码用 select 检查 socket 的可写状态来判断连接是否成功，IOS 版本的代码中没有对 connect 返回值做检查，才发现这个现象。。