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Labview向dll传递结构体参数（带字符串指针的结构体传参）

DLL端代码（c++）
```cpp
//DLL定义的结构体格式如下：
typedef struct Struct_Parm_Test{
char* username;
char* userpass;
char* db_name;
char* tab_name;
char* data_arr_str;
int wWaitTickCount;
}Struct_Parm_Test;
Struct_Parm_Test * RX_ARG;
//测试函数
int _stdcall struct_test(void* arg,char * str) {
std::string str_out;
RX_ARG = (Struct_Parm_Test*)arg;
str_out= std::string(RX_ARG->username)+"|"+std::string(RX_ARG->userpass) + "|" + std::string(RX_ARG->db_name) + "|" + std::string(RX_ARG->tab_name)+"|"+ std::string(RX_ARG->data_arr_str);
memcpy(str, str_out.c_str(), str_out.size()+1);
return RX_ARG->wWaitTickCount;
}
```