Re: Memory leak with CAsyncSocket::Create

From:
"AliR \(VC++ MVP\)" <AliR@online.nospam>
Newsgroups:
microsoft.public.vc.mfc
Date:
Tue, 10 Jul 2007 10:33:26 -0500
Message-ID:
<yINki.26173$C96.14953@newssvr23.news.prodigy.net>
As far as the memory being returned, it will eventually, when the system
thinks that the program won't need it anymore.
With the example I posted, before the loop my sample app is using 3676K of
memory after the loop the program is using 4024K of memory but there is no
memory leak.

As far as Create not being reentrant goes, I am not really sure what could
be causing that. There are some many possibilities as to why it doesn't
work the way he wants it. Is Close being called before the next call to
Create? Is the socket being passed from one thread to another? Maybe even
a corrupted install of Visual Studio.

I think that the OP should try and recreate the problem with one socket in
the main thread. And go from there.

AliR.

"Joseph M. Newcomer" <newcomer@flounder.com> wrote in message
news:2c87935kti783rkaf53n5d28th16khebq9@4ax.com...

I would have thought it *would* be returned.

I'm also concerned about the concurrency problem, because I've not seen
that particular
problem in MFC before. I'm wondering if there is some storage damage that
is causing both
apparent problems.
joe

On Tue, 10 Jul 2007 09:45:46 -0500, "AliR \(VC++ MVP\)"
<AliR@online.nospam> wrote:

I couldn't find a memory leak. What you are most likely seeing is windows
memory managment doing its work. The Create method is creating a socket
object, when when it's freed the memory is not given back to the system
right away.

(I used this method to detect a leak)

// Declare the variables needed
#ifdef _DEBUG
  CMemoryState oldMemState, newMemState, diffMemState;
  oldMemState.Checkpoint();
#endif

  for (int i=0; i<10; ++i)
  {
     CAsyncSocket *pAS = new CAsyncSocket;
     pAS->Create();
     pAS->Close();
     delete pAS;
  }

#ifdef _DEBUG
  newMemState.Checkpoint();
  if( diffMemState.Difference( oldMemState, newMemState ) )
  {
     TRACE( "Memory leaked!\n" );
  }
#endif

AliR.

"r norman" <r_s_norman@_comcast.net> wrote in message
news:2895939efidggi556s7fbje0euhm2jd2d0@4ax.com...

I have traced a memory leak problem to CAsyncSocket::Create(). Is
this a known problem? Is there a workaround/solution/fix? Here is
sample code:

 for (int i=0; i<m_nReopenCount; ++i) {
   CAsyncSocket *pAS = new CAsyncSocket;
   pAS->Create();
   pAS->Close();
   delete pAS;
}

Running this 1000 times uses up 1200 KBytes of memory, or just over 1
KByte per call. Commenting out the Create() leaves memory clean. (And
please don't complain about my bracketing style -- I like it.)

I have Visual Studio 2005 Professional version 8.0.

Incidentally, I also discovered that the call to Create() is not
re-entrant. My application involves connecting to some 10 to 20
external devices and my normal code creates a CWinThread to support
each socket, where the socket is created and destroyed only within
the thread routine. Creating all the threads and starting them up
simultaneously meant having multiple instances of
CAsyncSocket::Create() being called at the same time, crashing my
system (memory access faults). That one I found and fixed with
sentries. Now I am left with the memory leak.

The problem is that I have an rather intricate communication protocol
system all self contained so that adding a new hardware device simply
means creating a new instance of the whole works. It runs fine until
the external hardware goes haywire, in which case I destruct the whole
instance and start a new one which breaks and reconnects the socket
with a clean start and, most of the time, results in a good
connection; the external device resets itself through the disconnect.
One faulty device, though, generated thousand upon thousand of
disconnects over a number of days and, after a few hundred thousand of
these I my own system crashed due, I have now found out, to a lack of
memory caused by this leak.

My application must run essentially as an embedded system, unattended
week after week, month after month so I cannot tolerate a memory leak.
Does anybody know about this? Is there a simple clean way to force a
socket disconnection on a CAsyncSocket and then reconnect? My
application is the connect() end of the socket, not the listen() end.


Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

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