Vector of shared pointers , memory problems after clearing the vector

Here sharedptr and the element in vector share the same object which will result in invoking constructor and destructor only once.

you have two copies of shared_ptr<A> in this case, one is the sharedptr variable and the other as an element in the vector.

do this instead

test.push_back(std::move(sharedptr));

note now the original sharedptr has it's internal moved and no longer usable. The other thing is don't do anything at all, this is a perfectly valid usage of of shared_ptr and sharedptr will clean up itself after it goes out of scope.

The problem arises when the push_back adds a copy of the shared_ptr to the vector, leaving the original dangling until main exists. If you don't make the shared_ptr in main scope, the problem does not happen. Just avoid making the shared_ptr in main scope. Make it as a temporary right in the push_back call.

Output is now:   

constructor
I am almost there
destructor
I am here

New code:

#include <vector>
#include <iostream>
#include <memory>

using namespace std;

class A
{
public:
  A(){cout << "constructor" << endl;};
  ~A(){cout << "destructor"  << endl;};
};

int main( )
{
  vector<shared_ptr<A> > test;
  test.push_back(shared_ptr<A>(new A));
  cout << "I am almost there" << endl;
  test.clear();
  cout << "I am here" << endl;
  return 0;
}