C++类调用函数显示：undefined reference to 'XXX'

Question

UdpBroadcast.h文件中创建一个类及成员函数的声明，UdpBroadcast.cpp中包含成员函数的实现方法。

VADettask.cpp调用UdpBroadcast.h的函数成员显示 undefined reference to `UdpBroadcast::UdpSocketCreate()

UdpBroadcast.h代码：

#ifndef _UDP_BROADCAST_H_
#define _UDP_BROADCAST_H_

#include <iostream>
#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>

using namespace std;

class UdpBroadcast
{
private:
    struct sockaddr_in sendaddr;
    struct sockaddr_in recvaddr;

public:
    //UdpBroadcast();
    Uint32 UdpSocketCreate();
    void UdpSendProc(Int32 sockfd,    const char *IP, Uint32 Port);
    void UdpRecvProc(Int32 sockfd, Uint32 Port);
    Uint32 UdpSend(Int32 sockfd, char* msg);
    Uint32 UdpRecv(Int32 sockfd, char *msg, Uint32 len);
};

#endif

UdpBroadcast.cpp代码：

#include <iostream>
#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include "UdpBroadcast.h"

using namespace std;

Uint32 UdpBroadcast::UdpSocketCreate()
{
    Int32 sockfd;
    sockfd=socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd ==-1)
    {
         cout<<"socket error"<<endl;
        return -1;
    }
    return sockfd;
}

VADettask.cpp代码：

UdpBroadcast *m_UdpBroadcast = new(UdpBroadcast);
m_UdpBroadcast->UdpSocketCreate();

大家知道是什么原因吗？

Answer 1

你好，我用下面命令编译通过的了： g++ -o VADettask VADettask.cpp UdpBroadcast.cpp . 系统是Ubuntu v14.04.05.

你报错的原因应该是编译指令写成：g++ -o VADettask VADettask.cpp 了，这样链接的时候找不到 UdpBroadcast::UdpSocketCreate()函数的定义，因此报错。