malloc/free 不会调用类的构造/析构函数

 1 #include <iostream>
 2 #include <cstdlib>
 3 using namespace std;
 4 
 5 class A
 6 {
 7 public:
 8     A()
 9     {
10         cout << "A";
11     }
12     ~A()
13     {
14         cout << "~A";
15     }
16 };
17 
18 int main()
19 {
20     void *p = malloc(sizeof(A));
21     
22     A *a = new(p) A;
23     
24     free(p);
25     return 0;
26 }