Re: Tracing CComBSTR leaks

"Alexander Nickolov" <>
Wed, 17 Jan 2007 09:11:34 -0800
[out, retval] is not the same as [out] in Automation land.
If you don't have any pure [out] arguments then this is not
a source of leaks for you.

VariantCopy definitely makes a copy of anything contained
in the source VARIANT, including BSTRs. You need to clear
the target VARIANT when finished - using VariantClear.
Better yet, use a VARIANT wrapper class like CComVariant
if practical.

Alexander Nickolov
Microsoft MVP [VC], MCSD

"Richard Hollis" <> wrote in message

Maybe I'm misunderstanding you. Do you mean like this for [out,retval]

put_myproperty( BSTR *bsOut )
SysFreeString(bsOut); // free first?
*bsOut = m_sMyCString.AllocSysString();

I'm only using properties so these should all be [out,retval], but I
will double check this tomorrow. What is the relevance of just having
[out] especially with ASP? Does this cause a leak?

I've still been hard on the trail of my leaking BSTRs today and I
believe I found what appears to be a leak: where I have VariantCopy
making a copy an existing variant holding a BSTR. Does it therefore
follow that when you do this you then need to SysFreeString the bstrval
value in the new variant copy? If you don't it appears to be leaking.


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