#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void main() 
{ 
    unsigned char *tt; // tt已经被分配了一段内存空间，长度为len, 且值为0
    tt = (unsigned char*)calloc(10, sizeof(unsigned char));
    memset(tt, 0, 10); 
}

    int len = 10;
    unsigned char *tt = new unsigned char[len];
    memset(tt, 0, len);
    memset(tt, 0, len);
      memset(tt, 0, len);

typedef struct 
{
 unsigned char Name[20];//这里最好用数组
 bool Need;
 bool NeedBuf;
 int Type;
}DEF_PARAM, *PRT_DEF_PARAM; 

改法1
#include "stdlib.h"


typedef struct  
{ 
    unsigned char Name[32]; 
    bool Need; 
    bool NeedBuf; 
    int Type; 
}DEF_PARAM, *PRT_DEF_PARAM; 



int main() {

    PRT_DEF_PARAM dd; 
    unsigned char *tt; 
    dd = (PRT_DEF_PARAM )malloc(sizeof(DEF_PARAM)); 
    memset(dd, 0, sizeof(DEF_PARAM)); 


    return 0;
}


改法2

#include "stdlib.h"


typedef struct  
{ 
    unsigned char* Name;
    bool Need; 
    bool NeedBuf; 
    int Type; 
}DEF_PARAM, *PRT_DEF_PARAM; 



int main() {

    PRT_DEF_PARAM dd; 
    unsigned char *tt; 
    dd = (PRT_DEF_PARAM )malloc(sizeof(DEF_PARAM)); 
    memset(dd, 0, sizeof(DEF_PARAM)); 
    dd->Name = (unsigned char*)malloc(sizeof(char) * 32);
    tt = dd->Name; 
    memset(tt, 0, sizeof(char) * 32); 

    return 0;
}