CODEWITHSUNDEEP
c++multithreadingg++valgrindboost-thread
petersohn
petersohn

Reputation: 11720

Valgrind reports 'possibly lost' memory when working with Boost threads

I have a program that runs some action in a separate therad, then joins on the thread, such as this one:

#include <boost/thread.hpp>
#include <iostream>

using namespace std;

void f() {
    for (int i = 0; i < 100; ++i) cout << i << endl;
}

int main() {
    boost::thread t(f);
    t.join();
    return 0;
}

If I run Valgrind on it, it reports 'possibly lost' memory. This seems logical if I omit the join(), because in that case the thread is still running when the program exits. But if the thread is finished, I would expect that there are no warnings.

Here is the backtrace:

==8797== 288 bytes in 1 blocks are possibly lost in loss record 2 of 3
==8797==    at 0x4A1F8B3: calloc (vg_replace_malloc.c:467)
==8797==    by 0x400F289: allocate_dtv (in /lib64/ld-2.4.so)
==8797==    by 0x400F34D: _dl_allocate_tls (in /lib64/ld-2.4.so)
==8797==    by 0x53EF981: pthread_create@@GLIBC_2.2.5 (in /lib64/libpthread-2.4.so)
==8797==    by 0x4B3311D: boost::thread::start_thread() (in /home/egbomrt/BOOST/inst_1_47_0/lib/libboost_thread.so.1.47.0)
==8797==    by 0x40A20C: boost::thread::thread<void (*)()>(void (*)(), boost::disable_if<boost::is_convertible<void (*&)(), boost::detail::thread_move_t<void (*)()> >, boost::thread::dummy*>::type) (thread.hpp:204)
==8797==    by 0x406295: main (main.cpp:12)

Is this a problem with Boost Thread, Posix Thread or is this perfectly normal? I could just create a suppression rule for it, but it would also be good if I got a warning if there is an unfinished thread, but not when all threads are finished.

Upvotes: 11

Views: 1220

Answers (1)

petersohn
petersohn

Reputation: 11720

I found that the problem is with the pthread library. If I run the program on SUSE 10, I get the memory leaks, but if I run it on SUSE 11, I don't get the problem.

I get the same results with and without Boost.

Thanks for the comments. That helped me pinpoint the problem.

Upvotes: 4

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