Re: Memory leak
From: Michael J. Salamone [eMVP] (mikesa#at#entrek#dot#com)
Date: 02/26/04
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Date: Thu, 26 Feb 2004 09:12:32 -0800
Memory corruption can turn into leaks. For example, calls to free could
fail (if it's heap corruption).
I noticed you init your pointers to NULL, but you don't check them for
non-NULL before you call Release(). That could of course cause an access
violation.
You might check your calls to Release() that they are returning 0. If they
are not, then you may be leaking interfaces.
Also, this shouldn't be your problem, but it seems wasteful to call
CoInitializeEx every time in. Why not just call it once when the process
starts? Plus, you do need to balance CoInitializeEx with CoUninitialize.
--
Michael Salamone [eMVP]
Entrek Software, Inc.
www.entrek.com
"Siv" <anonymous@discussions.microsoft.com> wrote in message
news:233401c3fc6d$ebb924c0$a001280a@phx.gbl...
>
> Thanks for the reply.
>
> I have been using the function for long without any
> problem, may be thats because all my XML messages were
> short(less than 500char ). Any how i will try and add the
> suggetions.
>
>
> Why i say there could be a memory leak is
> 1. in sytem-settings-memeory the inuse memeory for
> programs increases rapidly when this app' is run
> 2. after 15 min or so the app' freezes as there is not
> enough program memory in the IPAQ.
>
> Since it works for 15min or so and then freezes, made me
> to think it was a memeory leak than a memory corruption.
>
> I was wondering could XML COM compoenet is not properly
> relased?
>
>
>
> Siv
>
>
> >-----Original Message-----
> >I haven't looked thoroughly through your code snippet,
> but the biggest thing
> >that worries me is the potential for memory overwrites
> (memory corruption).
> >
> >For example, in these line:
> >
> >> strncpy(m_XMLMessage,(const char*) XML, strlen(XML)+1);
> >
> >Is it possible XML string is larger than m_XMLMessage
> buffer will
> >accomodate? You probably want 1024, or better, sizeof
> (m_XMLMessage),
> >instead of strlen(XML)+1.
> >
> >> m_XMLMessage[strlen(m_XMLMessage) + 1] = '\0';
> >
> >The available subscripts on a string, just like any
> array, are 0..n, where
> >n=size of the array (in chars, or elements) - 1.
> >In your case, you can go from 0-1023. And the max NULL-
> terminated string
> >you could have is 1023 characters plus a NULL terminator -
> 1024 characters
> >total.
> >
> >If, in your case, the string was exactly the number of
> characters you could
> >have (1023), then strlen(m_XMLMessage) is 1023, that + 1
> is 1024, and you
> >have corruption. You don't want the "+1".
> >
> >You also have calls to mbstowcs and wcstombs that I
> see "+1"'s in. Again I
> >didn't go through this thoroughly, but I'm betting that's
> your problem.
> >
> >Btw, you probably don't want a number like "60" in your
> code. You should
> >probably have a sizeof() or #define or just about
> anything other than 60. I
> >see you declared your buffer that long, but I'm most
> worried about the call
> >to wcstombs that uses it. As soon as you change that 60
> to something
> >smaller, you're toast. You sizeof(m_CommandType).
> >
> >Why do you assume a leak?
> >
> >Also, I would review all my code for similar problems.
> >--
> >
> >Michael Salamone [eMVP]
> >Entrek Software, Inc.
> >www.entrek.com
> >
> >
> >"Siv" <anonymous@discussions.microsoft.com> wrote in
> message
> >news:22b901c3fc56$3d4d77e0$a401280a@phx.gbl...
> >> Hi,
> >>
> >> There is a a memory leak in a application, and i think
> >> the leak is caused by the following function, which is
> >> called in the main application many times( in while a
> >> loop). Moreover after running the application for 15min
> >> the following function fails. Below is the function. Can
> >> anyone spot a memory leak in the function???
> >>
> >> ////////////////////////////////////////////////////////
> ///
> >> ////////////////////////////////
> >> //Returns tag value for a given tag name from XML event
> >> notification
> >> //IN tag name
> >> //return tag value
> >> char* GetTagValueFromXMLmessage(char* XML,char* tagName)
> >> {
> >>
> >>
> >> char m_XMLMessage[1024];
> >> strncpy(m_XMLMessage,(const char*) XML, strlen(XML)+1);
> >> m_XMLMessage[strlen(m_XMLMessage) + 1] = '\0';
> >>
> >> char m_tagName[100];
> >> strncpy(m_tagName,(const char*)tagName,strlen(tagName)
> +1);
> >> m_tagName[strlen(m_tagName) + 1] ='\0';
> >>
> >> IXMLDOMDocument *iXMLDoc = NULL;
> >> IXMLDOMNodeList *iXMLNodeList = NULL;
> >> IXMLDOMNode *iXMLNodeCommandPtr = NULL;
> >>
> >> HRESULT hr;
> >> VARIANT_BOOL tEmpty;
> >>
> >> BSTR bstrCommandText;
> >> wchar_t pwc_xml[sizeof( wchar_t )*1024];
> >> wchar_t pwc_tagName[sizeof( wchar_t )*100];
> >>
> >> char m_xml[1024];
> >> char m_CommandType[60];
> >>
> >> _try
> >> {
> >>
> >> //create instance of msXML COM componenet
> >> hr = CoInitializeEx(NULL,COINIT_MULTITHREADED);
> >> if(!SUCCEEDED(hr)) return 0;
> >>
> >> hr = CoCreateInstance (CLSID_DOMDocument, NULL,
> >> CLSCTX_INPROC_SERVER | CLSCTX_LOCAL_SERVER,
> >> IID_IXMLDOMDocument,(LPVOID *)&iXMLDoc);
> >>
> >> if(iXMLDoc)
> >> {
> >> iXMLDoc->put_async(VARIANT_FALSE);
> >>
> >> //convert xmlMessage to wchar
> >> int ii = mbstowcs( pwc_xml, m_XMLMessage, strlen
> >> (m_XMLMessage) + 1 );
> >>
> >>
> >> //Load XML
> >> iXMLDoc->loadXML( pwc_xml, &tEmpty);
> >>
> >>
> >> //convert tagName to wchar
> >> ii = mbstowcs( pwc_tagName,m_tagName, strlen(m_tagName)
> >> +1 );
> >>
> >> //get command node
> >> //iXMLDoc->getElementsByTagName
> (L"Value",&iXMLNodeList);
> >> iXMLDoc->getElementsByTagName
> (pwc_tagName,&iXMLNodeList);
> >>
> >> iXMLNodeList->get_item(0, &iXMLNodeCommandPtr);
> >>
> >> iXMLNodeCommandPtr->get_text(&bstrCommandText);
> >> ii = wcstombs( m_CommandType, bstrCommandText, 60 );
> >>
> >> }//end if
> >>
> >> //Release memory
> >> iXMLNodeList->Release();
> >> iXMLNodeList = NULL;
> >> iXMLNodeCommandPtr->Release();
> >> iXMLNodeCommandPtr = NULL;
> >> iXMLDoc->Release();
> >> SysFreeString(bstrCommandText);
> >>
> >>
> >>
> >>
> >> }
> >> __except(EXCEPTION_EXECUTE_HANDLER)
> >> { int di;
> >> printf("ERROR in ..XML parse for tag: %
> >> s\n",m_tagName);
> >> scanf("%d",&di);
> >>
> >> }
> >>
> >> char a_m_xml[1024];
> >> strncpy(a_m_xml,m_CommandType, strlen(m_CommandType)
> >> +1);
> >>
> >> return a_m_xml;
> >>
> >>
> >>
> >> }
> >>
> >> Any replies is much appreciated
> >>
> >> Thanks
> >> Siv
> >
> >
> >.
> >
- Next message: Paul G. Tobey [eMVP]: "Re: Creating a separate desktop in WinCE 3.0."
- Previous message: Sarah: "eVC installation error"
- In reply to: Siv: "Re: Memory leak"
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