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Hi,  I seen some memory leak in my code during analyzing using DevPartner tool. I tried to fix it but didnt get any success. Please help me here.  Description: I am having an array of ATL::CString cla

Posted on 2009-07-13
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Last Modified: 2013-12-04
Hi,

I seen some memory leak in my code during analyzing using DevPartner tool. I tried to fix it but didnt get any success. Please help me here.

Description: I am having an array of ATL::CString class. In loop i am converting  these strings to _variant_t type like:

_variant_t varValue = LPCTSTR(m_StrArray[i]);

Then i am having one COM API: AddKey(VARIANT *pVarVal); Which takes VARIANT* as an input parameter.

I am calling  this API by passing  varValue as a paremeter in the following way:
spSomeInterface->AddKey(&varValue);

This API internally assign its parameter to _variant_t variable like:

HRESULT AddKey(VARIANT *pVarVal)
{
  m_vardata.Attach(*pVarVal);
}

When i run this code then DevPartner tool shows memory leak in the following line:
_variant_t varValue = LPCTSTR(m_StrArray[i]);

Please assist me to fix this leak. Its very important to fix because this leak exist in my core component.
suppose m_StrArray is the array of CString objects.
 
for(int i = 0; i < m_StrArray.Count(); i++)
{
    _variant_t varValue = LPCTSTR(m_StrArray[i]); //HERE IS MEMORY LEAK
     m_spSomeInterface->AddKey(&varValue);
}
 
AddKey function is defined as:
 
STDMETHODIMP CMyClass::AddKey(VARIANT *pVarVal)
{
    TItemMap::iterator it = m_Map.insert(_variant_t(), true).first;
    it->first.Attach(*pVarVal);    
}
 
Where m_Map is the map of _variant_t and bool value. Its member variable. So i am first creating a place holder for variant and then i am attaching it with the input VARIANT* parameter.

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Question by:harish_dixit1
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6 Comments
 
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Accepted Solution

by:
jkr earned 1000 total points
ID: 24841626
As in http://www.experts-exchange.com/Programming/Languages/CPP/Q_24565906.html

You are probably adding a CString (at least 'varValue = LPCTSTR(m_StrArray[i]);' suggests that), which means that first a new variant is constructed and assigned, which now is kinda 'orphaned'. Try

HRESULT AddKey(VARIANT *pVarVal)
{
  m_vardata.Clear(); // <---- !
  m_vardata.Attach(*pVarVal);
}

instead.
0
 

Author Comment

by:harish_dixit1
ID: 24841876
Sorry these two questions are same but first i submitted to MS Dev zone and i didnt get any response so i thought zone is not correct thats why i posted it in other zone also.
0
 

Author Comment

by:harish_dixit1
ID: 24841923
Thanks for reply.

I tried it as you suggested, but problem still exist.

I am giving stack trace shown by DevPartner tool here.
I am getting memory leak in the following function in comutil.h header file:

inline _variant_t& _variant_t::operator=(const wchar_t* pSrc)
{
      _COM_ASSERT(V_VT(this) != VT_BSTR || pSrc == NULL || V_BSTR(this) != pSrc);

    // Clear the VARIANT (This will SysFreeString() any previous occupant)
    //
    Clear();

    V_VT(this) = VT_BSTR;

    if (pSrc == NULL) {
        V_BSTR(this) = NULL;
    }
    else {
        V_BSTR(this) = ::SysAllocString(pSrc);

        if (V_BSTR(this) == NULL) {
            _com_issue_error(E_OUTOFMEMORY);
        }
    }

    return *this;
}


And Tool shows the leak in my code:
for(int i = 0; i < m_StrArray.Count(); i++)
{
    _variant_t varValue = LPCTSTR(m_StrArray[i]); //HERE IS MEMORY LEAK
     m_spSomeInterface->AddKey(&varValue);
}

If u want some more info then i can provide it.
Thanks.
0
 

Author Comment

by:harish_dixit1
ID: 24846820
I tried to comment the call of API m_spSomeInterface->AddKey(&varValue);
in the loop then DevPartner doesn't show any memory leak. It means the problem is not in the statement where we are converting String to variant. But i think problem is due to API call m_spSomeInterface->AddKey(&varValue);. Because this API is doing following assignment internally:

it->first.Attach(*pVarVal);

So its attaching param VARIANT* to _variant_t (it->first is of type _variant_t).
0
 

Author Comment

by:harish_dixit1
ID: 24856435
I have attached 2 files. One header file where map data structure is defined and source file where i am accessing the interface method.

I am using smart pointer for interface so no need to call Release on interface pointer.
Source.txt
Header.txt
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