1 #include <iostream>
 2 #include <cassert>
 3 #include <cstdlib>
 4 #include <cstring>
 5 
 6 using std::cout;
 7 using std::endl;
 8 
 9 struct Singleton;
10 static Singleton* inst = NULL;
11 struct Singleton {
12     virtual void test_what() { 
13         if (this == inst) {
14             cout << "OK, it‘s mine." << endl;
15         } else {
16             cout << "You go the wrong door" << endl; 
17             assert(false);
18         }
19     }
20 
21     void what() {
22         if (this == inst) {
23             cout << "OK, it‘s mine." << endl;
24         } else {
25             cout << "You go the wrong door" << endl; 
26             assert(false);
27         }
28     }
29 
30     void self() {
31         if (this == inst) {
32             cout << "OK, it‘s mine." << endl;
33         } else {
34             cout << "wtf!!!" << endl;
35             assert(false);
36         }
37     }
38 
39     static Singleton* getInstance() {
40         if (NULL == inst)
41             inst = new Singleton;
42         return inst;
43     }
44 
45     static void destroyInstance() {
46         if (NULL != inst) {
47             delete inst;
48             inst = NULL;
49         }
50     }
51 private:
52     Singleton() {}
53     Singleton(const Singleton&);
54     Singleton& operator=(const Singleton&);
55 };
56 
57 
58 int main(int argc, char* argv[])
59 {
60     //在程序开始就初始化，避免多线程中初始化
61     Singleton *a = Singleton::getInstance();
62     Singleton *p = (Singleton*)malloc(sizeof(Singleton));
63 
64     memcpy(p, a, sizeof(Singleton));
65     
66     //p->self();
67     //p->what();
68     p->test_what();
69     a->what();
70 
71     free(p);
72     Singleton::destroyInstance();
73 
74     return 0;
75 }