How to free resources when initializing list throws exception in c++?

Question

In below code I don't see A or C's destructor called. I know I can use smart pointers etc, but in general how should we handle already allocated resources when an initializing list throws?

#include <iostream>

using namespace std;

class C
{
public:
  ~C ()
  {
    cout << "destructing C" << endl;
  }
};

class A
{
public:
  A ()
  {
    throw bad_alloc ();
  }
   ~A ()
  {
    cout << "destructing A";
  }
};

class B
{
public:
  B () try:pc (new C ()), pa (new A ())
  {
  }
  catch (...)
  {
    cout << "bad thing happened" << endl;
    throw;
  }


  A *pa;
  C *pc;
};

int
main ()
{
  try
  {
    B b;
  } catch ( ...)
  {
    cout << "i'm catching this bad here" << endl;
  }
  cout << "Hello World" << endl;

  return 0;
}

Is it guaranteed to have a leak? If so is the best practice to allocate in constructor body and then do delete in the exception handler there?

Answer 1

Best practice would be to use smart pointers as you suggest in your question. For example: std::unique_ptr and std::make_unique .

class B {
 public:
  B() : pc(std::make_unique<C>()), pa(std::make_unique<A>()) {}

  std::unique_ptr<C> pc;
  std::unique_ptr<A> pa;
};

In this code, if pa throws, the destructor for pc would still be called.