Solved

CString memory leak in cwinthread

Posted on 2011-03-01
4
1,480 Views
Last Modified: 2012-05-11
When running my code I get this:

Detected memory leaks!
Dumping objects ->
strcore.cpp(118) : {86} normal block at 0x00302DF0, 31 bytes long.
 Data: <            Dude> 01 00 00 00 12 00 00 00 12 00 00 00 44 75 64 65
Object dump complete.

This is the code:
CString sD;
sD = "Dude this is weird";

If I comment out the second line only, the memory leak goes away.

This code is within a CWinThread object that is called from the main window and exits with a call to AfxEndThread(0); after sending a message back to the parent.  I can put this code in the parent window and it's fine.

There's another instance within the CWinThread object prior to these lines where this code is run:

CFtpConnection* pCon = NULL;
                     
try
      {
           pCon = parent->m_sSession->GetFtpConnection(FTP_SERVER, FTP_USER, FTP_PW, 21, TRUE);
      }
      catch (CInternetException* pEx)
      {
            CString sConnectionErrorMsg;
            TCHAR sz[1024];
            pEx->GetErrorMessage(sz, 1024);
            sConnectionErrorMsg.Format("Return error message: %s", sz);
            returnCode = UPDATE_CONNECTION_ERROR;
            m_sLog += "\r\nFTP connection failed\r\n" + sConnectionErrorMsg;
            pEx->Delete();
            delete pCon;
            pCon = NULL;
      }

Notice the use of CString object sConnectionErrorMsg here.  This does NOT create a memory leak.

Any ideas?
0
Comment
Question by:theclay
4 Comments
 
LVL 4

Accepted Solution

by:
parnasso earned 350 total points
ID: 35007545
My guess is that in the first case, when you end the thread with AfxEndThread(0), no destructor of the CString is called.

On the other hand, the code you written of the thread that uses the CString object sConnectionErrorMsg, DOES call the CString destructor and therefore, there is no memory leaks.

To solve your problem, wrap the first thread code in a function, and outside of that function called AfxEndThread so that every destructor get called because the objects get out of the scope.

Something like this.

functionDosomething()
{
  CString sD;
  sD = "Dude this is weird";
} // The object sD get out of scope so it will be released

functionThread()
{
   // do something
  functionDosomething();
  AfxEndThread(0);
}

Hope this helps
0
 
LVL 31

Assisted Solution

by:Zoppo
Zoppo earned 150 total points
ID: 35007909
Hi,

I agree with parnasso - just as additional info: 'AfxEndThread' internally uses '_endthreadex'. http://msdn.microsoft.com/en-us/library/hw264s73%28v=VS.100%29.aspx says: '_endthread and _endthreadex cause C++ destructors pending in the thread not to be called'

ZOPPO
0
 
LVL 33

Expert Comment

by:sarabande
ID: 35008873
you should omit the AfxEndThread. simply return from thread function.

Sara
0
 

Author Closing Comment

by:theclay
ID: 35009175
That took care of it - thanks.
0

Featured Post

Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Entering a date in Microsoft Access can be tricky. A typo can cause month and day to be shuffled, entering the day only causes an error, as does entering, say, day 31 in June. This article shows how an inputmask supported by code can help the user a…
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
With the power of JIRA, there's an unlimited number of ways you can customize it, use it and benefit from it. With that in mind, there's bound to be things that I wasn't able to cover in this course. With this summary we'll look at some places to go…
In this seventh video of the Xpdf series, we discuss and demonstrate the PDFfonts utility, which lists all the fonts used in a PDF file. It does this via a command line interface, making it suitable for use in programs, scripts, batch files — any pl…

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question