Boost memory leaks in threads

Question

Could somebody explain me why this peace of code produces memory leak(s)?

Boost 1.49 and boost-1.53 gives the same result....

#include <boost/thread.hpp> 
#include <iostream> 
#include <vector> 
#include <cstdlib> 
#include <ctime> 

boost::mutex mutex; 
boost::condition_variable_any cond; 
std::vector<int> random_numbers; 

void fill() 
{ 
  std::srand(static_cast<unsigned int>(std::time(0))); 
  for (int i = 0; i < 3; ++i) 
  { 
    boost::unique_lock<boost::mutex> lock(mutex); 
    random_numbers.push_back(std::rand()); 
    cond.notify_all(); 
    cond.wait(mutex); 
  } 
} 

void print() 
{ 
  std::size_t next_size = 1; 
  for (int i = 0; i < 3; ++i) 
  { 
    boost::unique_lock<boost::mutex> lock(mutex); 
    while (random_numbers.size() != next_size) 
      cond.wait(mutex); 
    std::cout << random_numbers.back() << std::endl; 
    ++next_size; 
    cond.notify_all(); 
  } 
} 

int main() 
{ 
  boost::thread t1(fill); 
  boost::thread t2(print); 
  t1.join(); 
  t2.join(); 
}

Here is valgrind output:

valgrind --leak-check=full --show-reachable=yes ./a.out

==3079== Memcheck, a memory error detector

==3079== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.

==3079== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info

==3079== Command: ./a.out

==3079==

val: 535293148

val: 1979778795

val: 1888522902

==3079==

==3079== HEAP SUMMARY:

==3079== in use at exit: 8 bytes in 1 blocks

==3079== total heap usage: 16 allocs, 15 frees, 1,732 bytes allocated

==3079==

==3079== 8 bytes in 1 blocks are still reachable in loss record 1 of 1

==3079== at 0x4C2B3F8: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)

==3079== by 0x4E45BF9: boost::detail::get_once_per_thread_epoch() (in /usr/local/lib/libboost_thread.so.1.53.0)

==3079== by 0x4E3F861: _ZN5boost9call_onceIPFvvEEEvRNS_9once_flagET_.constprop.239 (in /usr/local/lib/libboost_thread.so.1.53.0)

==3079== by 0x4E3F978: boost::detail::get_current_thread_data() (in /usr/local/lib/libboost_thread.so.1.53.0)

==3079== by 0x40A909: boost::detail::interruption_checker::interruption_checker(pthread_mutex_t*, pthread_cond_t*) (in /u00/system/workspace/shared_lock2/src/a.out)

==3079== by 0x4E40502: boost::thread::join_noexcept() (in /usr/local/lib/libboost_thread.so.1.53.0)

==3079== by 0x40ACAE: boost::thread::join() (in /u00/system/workspace/shared_lock2/src/a.out)

==3079== by 0x4092B0: main (in /u00/system/workspace/shared_lock2/src/a.out)

==3079==

==3079== LEAK SUMMARY:

==3079== definitely lost: 0 bytes in 0 blocks

==3079== indirectly lost: 0 bytes in 0 blocks

==3079== possibly lost: 0 bytes in 0 blocks

==3079== still reachable: 8 bytes in 1 blocks

==3079== suppressed: 0 bytes in 0 blocks

==3079==

==3079== For counts of detected and suppressed errors, rerun with: -v

==3079== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2)

This source is part of cpp book from http://en.highscore.de/cpp/boost/