STL中list和vector在添加元素时push_back会调用拷贝构造函数

 #include <iostream>
 #include <list>
 #include <vector>
 #include <cstring>
 using namespace std;

 class B
 {
 public:
     B()
     {
         cout<<"B()"<<endl;
     }
     void print()
     {
         cout<<"print"<<endl;
         p = NULL;
         len = ;
     }
     B(const B& b)
     {
         cout<<"copy B()"<<endl;
         if(p)
         {
             delete b.p;
             len = len;
             p = new char[len];
             memcpy(p, b.p, len);
         }
     }
     ~B()
     {
         cout<<"~B()"<<endl;
         if(p)
         {
             delete []p;
             p = NULL;
             len = ;
         }
     }
     char *p;
     int len;

 };

 int main()
 {
     list<B> ls;
     vector<B> vec;
     B b;
     ls.push_back(b);
     vec.push_back(b);
     return ;
 }

执行结果：