C 中调用DLL的有关问题 undefined reference to 'InitSMGPAPI’

C 中调用DLL的问题 undefined reference to 'InitSMGPAPI’
程序源码   ：
#include   <stdio.h>


#include   "smgpapi.h "
#include   "smgpdef.h "

#define   RECV_MSG_TIME_OUT 2   /*   Seconds   */

static   DeliverResp   g_DeliverResp;

int   main(void)
{
/*   Local   Vars   */
int   nRetCode;

/*   Call   API   InitSMGPAPI*/
/*   If   Your   Config   File   Not   In   Current   Dir   Or   Config   Dir   Please   */
/*   All   Dir   And   File   Name   */  
nRetCode   =   InitSMGPAPI(NULL);
if(nRetCode)
{
printf( "InitSMGPAPI   Return   Error\n ");
}

/*   Call   SMGPDeliver   To   Get   Message   */  
nRetCode   =   SMGPDeliver((int)RECV_MSG_TIME_OUT,&g_DeliverResp);
if(nRetCode)
{
printf( "Recv   Msg   From   SMGW   Fail!\n ");
}

else  
{
printf( "Recv   Msg   From   SMGW   Success!\n ");

}
return   0;
}

涉及到的头文件及   DLL文件都在同一目录下。

smgpapi.h   如下：

#ifndef   _SMGP_API_H_
#define   _SMGP_API_H_

/*#define   SMGP_CLIENT_VERSION10*/
#ifdef   SMGP_API_EXPORTS
#define   SMGPAPI_EXPORTS   int   __stdcall
#else
#define   SMGPAPI_EXPORTS   int
#endif


#ifdef   _WIN32
    #pragma   pack(push,1)
#elif   defined   _AIX
    #pragma   options   align=packed
#elif   defined   _HPUX
    #pragma   pack   1
#else
    #pragma   pack   (1)
#endif


/*   Send   Batch   Message   Responce   Which   Is   Written   In   File   */
typedef   struct
{
char sMsgID[10+1];
int nErrorCode;
char sPhoneNo[21+1];
}SendBatchResp;

/*   Query   Message   Responce   Struct   */
typedef   struct
{
int nMT_TLMsg;
int nMT_TLusr;
int nMT_Scs;
int nMT_WT;
int nMT_FL;
int nMO_Scs;
int nMO_WT;
int nMO_FL;
}QueryResp;

/*   Receive   Message   Responce   Struct   */
#ifdef   SMGP_API_EXPORTS
/*DLL   VERSION*/
typedef   struct
{
unsigned   int nIsReport;
unsigned   int nMsgFormat;
unsigned   int nMsgLength;
char sMsgID[10+1];
char sRecvTime[14+1];
char sSrcTermID[21+1];
char sDestTermID[21+1];
char sMsgContent[252+1];
        char                 sReserve[8+1];
}DeliverResp;

typedef   struct
{
unsigned   int   nSerialNo;   /*消息头中的流水号*/
unsigned   int   nStatus;
unsigned   int   nMsgType;
        unsigned   int   nMsgFormat;
unsigned   int   nDesMode;
unsigned   int   nKeySerialNo;
unsigned   int   nIIType;
unsigned   int   nMsgLength;
char sMsgID[20+1];
char sSrcTermID[21+1];
char sDestTermID[21+1];
        char sSessionID[20+1];