Std::deque does not release memory until program exits

Question

On linux, std::deque does not release memory until program exits. The complete code is below. Any help will be greatly appreciated!

#include <deque>
#include <vector>
#include <string>
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <queue>
#include <list>
#include <cstdio>
#include <cstdlib>

typedef  boost::shared_ptr<std::vector<int> > VecPtr;
typedef  std::deque< VecPtr  > QueueType;

 char buf[1024];
 char line[1024];

 int main()
 {

  {

    int v=0;
    QueueType  deq;
    for(int i=0; i<30;++i)
    for(int j=0; j<1000;++j)
    for(int k=0;k<1000;++k)
    {
       VecPtr p( new std::vector<int>);
       deq.push_back(p);
    }

    std::cout<<"Done with increasing deq:deq size="<<deq.size()<<std::endl;
    sleep(20);

    std::cout<<"start decreasing deq size"<<std::endl;
    while(deq.size()>0)
    {
      deq.pop_front();
    }
    std::cout<<"done with decreasing deq size,deq size="<<deq.size()<<std::endl;
  }
  std::cin.getline(line,sizeof(line));
  return 0;
}

Answer 1

That is correct, pop_front() does not deallocate storage that was allocated by push_back() If you want to deallocate it before the program ends, you can end the lifetime of the object. If you want to deallocate it before the lifetime of the object ends, consider using a "shrink-to-fit" idiom for C++ container classes.

QueueType().swap (deq); // C++98
deq.shrink_to_fit(); // C++11