Re: Cstring question Again

 <tarun.kanal <at> ...> writes:

> 
> Hi All
> 
> I've come across a piece of code.
> 
> This is defined in AtlBase.h line number 3977
> 
> 	BSTR Detach()
> 	{
> 		BSTR s = m_str;
> 		m_str = NULL;
> 		return s;
> 	}
> 
> Now in this method m_str is being made NULL without being released.
> Is this correct? Its giving me a memory leak out here.
> 

Yes, this is correct. The alternative could be:

BSTR Detach()
{
	BSTR garbage = m_str;
        ::SysFreeString(m_str); // This line trashes 'garbage'
	m_str = NULL;
	return garbage;
}

See what I mean? This function HAS to return a VALID BSTR. 

> My Code is as follows
> 
> CComBSTR  bstrTemp = T2W(szData); 
> *bstrBuffer = bstrTemp.Detach(); //this is giving a memory leak
> 
> Any pointers how to tackle this or is my approach wrong??
> 

Option 1:

   CComBSTR  bstrTemp = T2W(szData); 
  *bstrBuffer = bstrTemp.Detach(); //this is giving a memory leak

   // After returning from wherever the former happened...
   DoStuffWith(bstrBuffer);
   DoMoreStuffWith(bstrBuffer);

   // And, finally.
   ::SysFreeString(*bstrBuffer);

Option 2:

{
   CComBSTR  bstrTemp = T2W(szData); 
   DoStuffWith(bstrTemp);
   DoMoreStuffWith(bstrTemp);
   // bstrTemp's destructor cleans up very nicely.
}

See also:

http://www.devguy.com/fp/Tips/COM/bstr.htm

Best wishes, 

Pablo.

> Regards
> Tarun
> 
> 
> 
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> 
> 
> 
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