[Boost-users] Memory problem using shared_ptr w/ STL-containers, gcc

From: Robert Fendt (robert_at_[hidden])
Date: 2006-10-19 10:24:49

Hi,

I have a somewhat peculiar problem concerning the shared_ptr template.
I use an STL container to hold several shared_ptr values. When the
container is destroyed, all the destructors are called correctly, but
the memory is not freed. Furthermore, shared_ptr usage introduces a
100x memory overhead (or more) in my case. Compiler system is GCC.

Consider the following short example:

#include <iostream>
#include <string>
#include <deque>
#include <boost/shared_ptr.hpp>

class A {
public:
  int a;
  int b;
};

int main() {
  std::string tmp;

  std::cout << "Enter something to continue" << std::endl;
  std::cin >> tmp;

 {
    std::deque<boost::shared_ptr<A> > list;
    for (int i = 0; i < 10; i++) {
      boost::shared_ptr<A> ptr(new A());

      list.push_back(ptr);
    }

    std::cout << "Enter something to continue" << std::endl;
    std::cin >> tmp;
  }

  std::cout << "Enter something to continue" << std::endl;
  std::cin >> tmp;
}

Between the first and the second stop, the program size in memory grows
by about 150k... and that's for 10 objects which are <20 bytes large,
individually. And to top it off, it leaks memory. Between stops two and
three the memory *should* be freed since the scope is left. I can
include a destructor doing debug output in the class which shows that
the objects are indeed destroyed. But the memory stays allocated.

I suspect this is a GCC problem, but I have actually no clue... I
tested it on a recent Debian "Unstable" and an Ubuntu "Breezy". GCC
versions varying from 3.2 to 4.1. Or do I use the template in a wrong
way? Suggestions would be very welcome... and if this is a known bug in
GCC, a feasible work-around would be great.

Thanks in advance,
Robert