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, 0);
    if(sock == -1){
        const char* str = strerror(errno);
        printf("socket: %s
", str);
        return -1;
    }
    
    int flags = fcntl(sock, F_GETFD, 0);
    flags |= O_NONBLOCK;
    fcntl(sock, F_SETFD, flags);
    
    char ch = 1;
    setsockopt(sock, IPPROTO_TP, TCP_NODELAY, &ch, sizeof(ch));
    int value = 1;
    setsockopt(sock, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value));
    
    struct sockaddr_in addr = {0};
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8000);
    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
", str);
            //return -1;    // 注释掉这里，后面 select 返回 1
        }
        
        int nfds = 0;
        fd_set wset;
        FD_ZERO(&wset);
        FD_SET(sock, &wset);
        nfds = sock + 1;
        
        struct timeval timeout;
        timeout.tv_sec = 1;
        timeout.tv_usec = 0;
        int n = select(nfds, 0, &wset, 0, &timeout);
        if(n > 0){
            struct sockaddr in = {0};
            socklen_t len = sizeof(in);
            int e = getpeername(sock, &in, &len);
            if(e){
                int err = errno;
                printf("getpeername: %s
", strerror(err));
            }
        }
        
    }
    
    return 0;
}

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。。