[pywin32-bugs] [ pywin32-Bugs-736517 ] Memory Leak

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Bugs item #736517, was opened at 2003-05-12 11:49
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Shack Toms (shacktoms)
Assigned to: Nobody/Anonymous (nobody)
Summary: Memory Leak

Initial Comment:
There is a memory leak associated with events delivered 
through the IConnectionPoint interface.   The leak 
occurs when a ByRef VARIANT parameter is passed 
through the interface as an inout parameter.

The culprit appears to be oleargs.cpp, specifically the 
routine PythonOleArgHelper::MakeObjToVariant, which 
is called to replace the original VARIANT with the 
returned one.   In the case VT_VARIANT | VT_BYREF, 
with bCreateBuffers as false, the routine calls 
VariantClear(var), which only clears the referencing 
VARIANT and not the referenced one.   This call should 
be VariantClear(V_VARIANTREF(var)), which will clear 
memory held by the referenced VARIANT before the 
subsequent call to PyCom_VariantFromPyObject 
simply overwrites that VARIANT.

The code as written depends on V_VARIANTREF(var) to 
remain valid after calling VariantClear(var), which seems 
a dangerous assumption.

Note that this repair follows the same logic as is used in 
the existing code for the VT_BSTR | VT_BYREF case, 
in which SysFreeString(*V_BSTRREF(var)) is called, for 
the reason that VariantClear(var) wouldn't free the 
indirectly referenced BSTR.

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