dll调用问题

//动态链接里面函数定义
int ykt_readopencard4442_local(int offset, int length, char *pData, char *pwarnmsg, char *pErrmsg)


//delphi中定义
function ykt_readopencard4442_local(offSet: Integer; Len: Integer; pData: Pchar; pWarnMsg: Pchar; pErrMsg: Pchar): longint; stdcall;

//调用时：
    pCardNo := StrAlloc(1024);

    sWarnMsg := StrAlloc(1024);
    pErrMsg := StrAlloc(1024);
    Res := ykt_readopencard4442_local(0, 10, pCardNo, sWarnMsg, pErrMsg);

//其中pCardNo传回来的是一堆乱码，请这是啥问题