数组扩容后再添加，，所遇到的问题

 1 #include<iostream>
 2 using namespace std;
 3 
 4 
 5 int arrayInit(int size, int **outbuf)
 6 {
 7     int a;
 8     int *buf = NULL;
 9     buf = (int *)malloc(sizeof(int)*size);
10     memset(buf, 0, size);
11     *outbuf = buf;
12 
13     cout << "请赋值：" << endl;
14     for (int i = 0; i < size; i++)
15     {
16         cin >> a;
17         buf[i] = a;
18     }
19     cout << "赋值结束！" << endl;
20 //    buf[0] = 2;
21     return size;
22 }
23 
24 void arrayExpand(int *inbuf, int presize, int **outbuf)
25 {
26     int size=2*presize;
27     int *buf = NULL;    
28 //    presize = _msize(inbuf) / sizeof(int);
29 
30     buf = (int*)malloc(sizeof(int)*size);
31     memset(buf, 0, size);    
32     
33     for (int i = 0; i < presize; i++)
34     {
35         buf[i] = inbuf[i];
36     }
37 //    buf[1] = 0;
38     *outbuf = buf;
39 
40 }
41 
42 int arrayAdd(int *inbuf,int a,int presize)
43 {
44     int maxSize = 0;
45     int size = presize + 1;
46     maxSize = _msize(inbuf) / sizeof(int);
47 
48     cout << "maxsize====>" << maxSize << endl;
49     if (size > maxSize)
50     {
51         arrayExpand(inbuf, presize, &inbuf);
52         cout << "扩容了===》" << size << endl;
53     }
54 
55     inbuf[presize] = a;
56 
57     return size;
58 }
59 
60 void main()
61 {
62     int size = 0;
63     int *buf=NULL;
64 //    int *outbuf = NULL;
65     size = arrayInit(1, &buf);            //初始化长度为1的数组
66 
67 //    arrayExpand(buf, size, &buf);        //扩容函数，把容量扩为原来的两倍
68 
69     size = arrayAdd(buf, 5, size);        //在数组最后添加数字5     在添加函数中，扩容后数字添加不成功？？？
70     cout << "size[1]" << buf[1] << endl;
71     size = arrayAdd(buf, 6, size);        //在数组最后添加数字6
72     cout << "size[2]" << buf[2] << endl;
73     cout << "size=" << buf[1] <<endl;
74     cout << "maxsize" << _msize(buf)/sizeof(int) << endl;
75     system("pause");
76 }