[release/5.0] WinRT Reference Tracker memory fixes - #51421
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Found during new ComWrappers aggregation API in .NET 6.
It is possible that a Reference Tracker runtime can QI a managed object wrapper when it has been marked as Destroyed or the associated managed object has been collected. The QI impl must safely ensure prior to performing the QI that the GC hasn't collected the wrapped managed object.
ComWrappers API test passes GCStress=0xf
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Apr 19, 2021
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Approved. I will take for consideration in 5.0.x
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track down an issue for C#/WinRT.
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Runtime follow up fixes for .NET 5 - #45622 and microsoft/CsWinRT#782
Description
The following PR is for rare but not uncommon scenarios in the WinUI interactions with .NET. The C#/WinRT has been able to mitigate some of the following issues but they can still occur and results in leaks or a destabilized application environment.
QueryInterface.QueryInterfacescenario.Once this work is in it will be ported to .NET 6.
Customer Impact
Possible crashing behavior when a Reference Tracker runtime (Xaml) performs a
QueryInterfaceon a collected managed object. Memory leak in an uncommon scenario involving breaking circular references using the .NET GC.Regression
This API is new in .NET 5.0 and these issues have existed since original implementation. However the API is used to address the removal of WinRT built-in support - #37672.
Testing
The C#/WinRT and WinUI teams have signed off on these changes using a private build of the runtime. Additional runtime testing for the fixed behavior in this PR has also been added.
Risk
These changes only impact WinRT scenarios and represent no risk in all other scenarios.
/cc @davidwrighton @Scottj1s @manodasanW @MikeHillberg @jkoritzinsky @elinor-fung