CString causing memory leaks when being reassigned

[nyjil]

Jeez, I hope someone can help me.<br><br>I'm using edit boxes to display CStrings via the UpdateData(FALSE).&nbsp;&nbsp;At times the variable attached to the edit box are changed.&nbsp;&nbsp;Whenever I change the CString variable the gosh-darn thing causes a memory leak.&nbsp;&nbsp;Why? I have no idea and that is my question.&nbsp;&nbsp;The edit box in question is part of a child window that is started by a DoModal() in the parent window.&nbsp;&nbsp;I was under the impression that I could change the CString variable at anytime by simply reassigning it and then give the command UpdateData(FALSE) and the computer would display the newly reassigned value in the edit box.&nbsp;&nbsp;Example<br><br><br>//Assigns value to variable CString 'text' and displays on screen in an edit box.<br>text = &quot;Hello&quot;;<br>UpdateData(FALSE);<br><br>//causes a memory leak when 'text' is reassigned.<br>text = &quot;Goodbye&quot;;<br>UpdateData(FALSE);<br><br>I get the intended result and the program does redisplay the edit box with the newly reassigned value, but now for some reason a memory leak occurs.&nbsp;&nbsp;Why is this? Please I've been pulling out my hair for over a month trying to figure out this one.&nbsp;&nbsp;Do I need to clear the value of &quot;Hello&quot; before assigning &quot;Goodbye&quot;?&nbsp;&nbsp;If so, how do I do this?&nbsp;&nbsp;Does the fact that the edit box is in a child window instead of the main window have anything to do with my problem?&nbsp;&nbsp;Any help would be appriciated<br><br>Thank you<br>Nyjil

 

[palbano]

Dear Nyjil,<br><br>What you describe should not cause a memory leak. Have you installed all the SP's for your OS and your Visual C++?<br><br>What version of VC are you running?<br>What OS are you on?<br>How are you determining there is a memory leak?<br><br>-pete

 

[nyjil]

Palbano,<br><br>I am running VC 6.0 and am on Windows 98.&nbsp;&nbsp;I am determining that there is a memory leak by using:<br><br>(begining of function)<br>#ifdef _DEBUG<br> CMemoryState oldMemState, newMemState, diffMemState;<br> oldMemState.Checkpoint();<br>#endif<br><br>//function itself....<br><br>#ifdef _DEBUG<br> newMemState.Checkpoint();<br> if( diffMemState.Difference( oldMemState, newMemState) )<br> {<br> TRACE( &quot;Memory leaked!\n&quot; );<br> }<br>#endif<br>(end of function)<br><br>Am I using this correctly?&nbsp;&nbsp;Please let me know.<br><br>Thank you<br>Nyjil

 

[palbano]

Dear Nujil,<br><br>&gt; Am I using this correctly?<br><br>Well if you are doing this:<br><br>Setup memory check<br>text = &quot;Goodbye&quot;;<br>UpdateData(FALSE);<br>check memory<br><br>Then no, you are not using it correctly<br><br>Hope this helps<br>-pete

 

[nyjil]

Dear Palbano<br><br>What a relief to hear that I'm not doing it right. Thought I had a major memory leak because of it.&nbsp;&nbsp;I have been testing for memory leaks by the exact way that you described that I should not.&nbsp;&nbsp;Means something else is wrong with my program then.&nbsp;&nbsp;I appricate your time, and I will just have to continue to hunt down the problem then.<br><br>By the way, why is it that the memory check is coming up as a leak when I use it in the manner that you say is wrong?<br><br>Thanks yet again,<br><br>Nyjil

 

[palbano]

Dear nyjil,<br><br>From the MSDN documentation of CMemoryCheck:<br><br>************<br>CMemoryState provides a convenient way to detect memory leaks in your program. A “memory leak” occurs when memory for an object is allocated on the heap but not deallocated when it is no longer required.<br>************<br><br>That does not match the way you are using it because you are not deallocating the 'text' variable before performing the check. Also if I guess correctly, your variable 'text' is a stack based entity to begin with.<br><br>Hope this helps<br>-pete<br>