play with constructor / destructor in C++

constructor_destructor.cpp

#include <iostream>
#include <vector>

using namespace std;

struct X
{
  int val;

  void out(const string& s, int nv) {
    cout << this << "->" << s << ": " << val << " (" << nv << ")" << endl;
  }

  X() { out("X()", 0); val = 0; }

  X(int v)  { out( "X(int)", v); val = v; }

  X(const X& x) { out("X(X&)", x.val); val = x.val; }

  X& operator=(const X& a)
  {
    out("X::operator=()", a.val);
    val = a.val;
    return *this;
  }

  ~X() { out("~X()", 0); }
};

X glob(2);
X copy(X a) { return a; }
X copy2(X a) { X aa = a; return aa; }
X& ref_to(X& a) { return a; }
X* make(int i) { X a(i); return new X(a); }

struct XX { X a; X b; };

int main() {
  X loc(4);
  X loc2 = loc;
  loc = X(5);
  loc2 = copy(loc);
  loc2 = copy2(loc);
  X loc3(6);
  X& r = ref_to(loc);
  delete make(7);
  delete make(8);
  vector<X> v(4);
  XX loc4;
  X* p = new X(9);
  delete p;
  X* pp = new X[5];
  delete[] pp;
}