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Automatically marshal COM outputs as WinRT - #1771

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Jevan Saks (jevansaks) merged 12 commits into
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user/jevansa/com-out-ptr-marshalling-policy
Sep 1, 2026
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Automatically marshal COM outputs as WinRT#1771
Jevan Saks (jevansaks) merged 12 commits into
mainfrom
user/jevansa/com-out-ptr-marshalling-policy

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@jevansaksJevan Saks (jevansaks) commented Jul 30, 2026•
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Summary

  • Automatically projects recognized COM IID/void** outputs through C#/WinRT when the returned identity implements IInspectable, with COM fallback on E_NOINTERFACE.
  • Enables the behavior by default and adds the comInterop.autoWinRTMarshalling opt-out.
  • Supports flat P/Invoke, generated COM managed call paths, built-in COM, null output, and Native AOT.
  • Preserves existing CsWinRT/source-generated COM RCW identity through ComWrappers.TryGetComInstance and classic COM RCW identity through Marshal.GetIUnknownForObject.
  • Uses generated COM marshalling for [GeneratedComClass] CCWs and C#/WinRT marshalling for ordinary managed CCWs.
  • Documents the selected architecture under docs/design.

Validation

  • Full warning-as-error build and package creation.
  • Full non-hardware and hardware-dependent test suites.
  • Focused .NET 9 and .NET 10 identity, interface, and round-trip tests for CsWinRT RCWs, source-generated COM RCWs, classic COM RCWs, WinRT CCWs, and generated COM CCWs.
  • Fresh package-consumption Native AOT publish and execution of the adaptive marshaller.

Design: #1770

Generated with Copilot CLI, model: GPT-5.6 Sol.

@jevansaks
Add COM output pointer marshalling policies
e020335
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaksJevan Saks (jevansaks) mentioned this pull request Jul 30, 2026
Closed
@jevansaks
Use stable shell path in COM test
d26630d
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks

Jevan Saks (jevansaks) commented Jul 30, 2026

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The first hardware run exposed a test-only environment dependency: SIGDN_NORMALDISPLAY returned win on Windows Server (extensions hidden) instead of win.ini. Commit d26630d now asserts the stable SIGDN_FILESYSPATH; the focused test passes in Release on .NET 9 and .NET 10.

@jevansaks
Automatically marshal COM outputs as WinRT
b806e30
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaksJevan Saks (jevansaks) changed the title Add COM output pointer marshalling policiesAutomatically marshal COM outputs as WinRTJul 31, 2026
@jevansaks
Merge main into automatic COM marshalling
e9c17ae
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Order build-task test dependencies
9132673
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Consolidate Native AOT integration coverage
3322610
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Clarify raw COM marshalling coverage
cfcdc85
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Remove duplicate integration runtime coverage
fbd33d1
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Remove IID marshalling side channel
59402eb
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Jevan Saks (jevansaks) marked this pull request as ready for review August 5, 2026 06:15
Sergio0694
Sergio Pedri (Sergio0694) reviewed Aug 5, 2026
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Comment threadsrc/Microsoft.Windows.CsWin32/templates/ComOrWinRTObjectMarshaller.cs Outdated
@jevansaks
Test WinRT object COM input marshalling
0dc5f01
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Preserve COM and WinRT output identities
77283ff
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: b24622c7-c9d6-44f0-9a20-85aac5ff11d6
@jevansaks
Jevan Saks (jevansaks) marked this pull request as draft August 8, 2026 00:46
@jevansaks
Jevan Saks (jevansaks) marked this pull request as ready for review August 11, 2026 16:22
Sergio0694
Sergio Pedri (Sergio0694) approved these changes Sep 1, 2026
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@Sergio0694Sergio Pedri (Sergio0694) left a comment

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LGTM, seems very convenient!

Comment threadtest/Microsoft.Windows.CsWin32.Tests/COMTests.cs Outdated
@jevansaks
Make auto WinRT marshalling tests resilient
cdfc72b
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 3c541bf2-2b33-4212-8c2f-cb19a7af6728
@jevansaks
Jevan Saks (jevansaks) merged commit 567c2a2 into mainSep 1, 2026
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@jevansaks
Jevan Saks (jevansaks) deleted the user/jevansa/com-out-ptr-marshalling-policy branch September 1, 2026 23:27
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@Sergio0694Sergio Pedri (Sergio0694)Sergio0694 approved these changes

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