Re: Thread: memory leak when using not detached thread?

[Vass Andras]

Thread are created joinable by default - at least in commoncpp2-1.0.7.
>From the libc info pages:
"When a joinable thread terminates, its memory resources (thread
     descriptor and stack) are not deallocated until another thread
     performs `pthread_join' on it. Therefore, `pthread_join' must be
     called once for each joinable thread created to avoid memory leaks."
The problem can be solved if you detach the thread in the Thread::~Thread
destructor,
right before calling terminate (See below)

ps: has anynone taken a look at the bug report on savannah.gnu.org?

Thread::~Thread()
{
#ifdef WIN32
  terminate();

  if (isThread())
  {
    priv->_tid = 0;
    _self.setKey(DUMMY_INVALID_THREAD);
  }
  if (priv->_hThread) CloseHandle(priv->_hThread);
  if (priv->_cancellation) CloseHandle(priv->_cancellation);

#else
  detach();
  if(this != &_mainthread){
    terminate();
  }
#endif // WIN32
}

----- Original Message -----
From: "David Sugar" <address@hidden>
To: "Gernot Hillier" <address@hidden>
Cc: <address@hidden>
Sent: Tuesday, December 10, 2002 3:19 PM
Subject: Re: Thread: memory leak when using not detached thread?


>
> A thread cannot delete it's own context or join itself.  To make a thread
> that is a self running object that self-deletes, one has to detach the
> thread.  However, there is very definately a known bug in at least some
> glibc releases that when a detached thread exits, it will not clean up
> it's stack frame allocations because that code only existed in the
> pthread_join implimentation, and, of course, one cannot self join...
>
> On Mon, 9 Dec 2002, Gernot Hillier wrote:
>
> > --[PinePGP]--------------------------------------------------[begin]--
> > Hi!
> >
> > I'm no pthread guru, so perhaps I've misunderstood something. Please
excuse
> > this ;-)
> >
> > I narrowed my problem down to a very small test application. See
attached
> > test.cpp file.
> >
> > This program produces a memory leak - i.e. a finishing thread doesn't
free its
> > resources.
> >
> > I had a small look on the sources and the problem seems to be in
> > Thread::terminate():
> >
> >         if(pthread_self() != priv->_tid)
> >         {
> >                 printf("grbml\n");
> >                 // in suspend thread cannot be cancelled or signaled
> >                 // ??? rigth
> >                 // ccxx_resume(priv->_tid);
> >
> >                 // assure thread has ran before we try to cancel...
> >                 if(_start)
> >                         _start->post();
> >
> >                 pthread_cancel(priv->_tid);
> >                 pthread_join(priv->_tid,NULL);
> >         }
> >
> > This doesn't get called as pthread_self() seems to be the same thread
which
> > deletes this. So pthread_join isn't called and the resources aren't
freed.
> >
> > Now I thought Thread::final() won't run in the same thread context as my
new
> > thread? So why doesn't this work?
> >
> > Do I have to use Thread::detach() instead of Thread::start() when I want
to
> > "delete this"?
> >
> > Could you elaborate on the cited glibc bug mentioned in the
Thread::detach()
> > docu? I asked a glibc developer and he told me that it's my fault if I
don't
> > run pthread_join - no glibc bug.
> >
> > I've seeked the archives a  little bit but found no mail responding my
> > question. Sorry if this is a FAQ.
> >
> > --
> > Ciao,
> >
> > Gernot
> > "Der Horizont vieler Menschen ist ein Kreis mit Radius Null - und das
nennen
> > sie ihren Standpunkt." (A. Einstein)
> > --[PinePGP]-----------------------------------------------------------
> > gpg: Warning: using insecure memory!
> > gpg: Signature made Mon 09 Dec 2002 05:12:42 AM EST using DSA key ID
619E49E2
> > gpg: Can't check signature: public key not found
> > PinePGP: Encryption backend encountered error.
> > --[PinePGP]----------------------------------------------------[end]--
> >
>
>
>
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