boost::lockfree - Call destructor for queued element

Question

I wasn't able to force destruction of a boost::lockfree::spsc_queue element on pop. (They are correctly destroyed when a push overwrites an element of the circular buffer or when the list is destroyed, even when accessing the element by reference ).

Neither I was able to direct access to the element stored in the queue for destroying it via a reference.

#include <boost/lockfree/spsc_queue.hpp>
#include <boost/lockfree/policies.hpp>
#include <iostream>
#include <memory>

using namespace boost::lockfree;

class testDestructor{
        public:
        int x;
        static int y;
        testDestructor(): x(y++){}
        ~testDestructor(){ std::cout << x << std::endl ;}
        };

int testDestructor::y=1;


spsc_queue< std::shared_ptr<testDestructor>, capacity<100>> q;
int sum = 0;

void produce()
{
  for (int i = 1; i <= 100; ++i)
    q.push( std::move( std::shared_ptr<testDestructor>( new testDestructor() ) ) ) ;
}


void consume( std::shared_ptr<testDestructor> & tp){
    sum+=tp->x;
//TRYING TO FORCE DESTRUCTION:
    tp.reset();
}

int main()
{
  produce();
  //consuming a reference to force freeing the pointer
  q.consume_all([](  std::shared_ptr<testDestructor>  & tp){ consume(tp);  });
  std::cout << sum << "<- Destructors should be called before this" << std::endl;
}

Answer 1

There are some issues with spsc_queue in older versions of boost. The code you posted works fine with boost 1.60. Upgrade to the current version if you can.

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