Remove /clr:pure from WPF C++/CLI projects by vinnarayana-msft · Pull Request #11575 · dotnet/wpf

vinnarayana-msft · 2026-04-13T08:47:06Z

Description

MSVC 14.51 (VS 18.3) is removing support for /clr:pure when used with /clr:netcore. WPF is the only known consumer of /clr:pure. This PR migrates the two affected C++/CLI projects (DirectWriteForwarder.vcxproj and System.Printing.vcxproj) from /clr:pure to standard /clr:netcore (IJW mixed mode).

Changes:

Changed CLRSupport and CompileAsManaged from pure to NetCore in both vcxproj files
Updated Wpf.Cpp.props to remove the pure to NetCore conversion logic in ManagedCxx conditions
Removed ijwhost.dll from packaging exclusions in both vcxproj files — mixed-mode assemblies require this .NET runtime bootstrap shim to load correctly
Fixed ARM64 build break in intsafe_private_copy.h where _M_ARM64 was missing from an architecture detection #if condition (previously masked by _M_CEE_PURE)

Customer Impact

Without this fix, WPF will fail to build with MSVC 14.51+ (VS 18.3) since /clr:pure + /clr:netcore will no longer be a valid combination. This is a build-time breaking change from the MSVC toolset.

Regression

No. This is a proactive change to address an upcoming MSVC toolset deprecation. No existing behavior is regressed — the output DLLs function identically at runtime.

Testing

Test	Result
x64 build	✅ Pass
ARM64 build compilation	✅ Pass
WPF Gallery app run (x64)	✅ Pass

Risk

Low-Medium. The change is minimal (4 files) and surgical — it only affects the two C++/CLI projects in WPF. The runtime behavior of the DLLs is functionally equivalent; the difference is the compilation mode (pure MSIL → IJW mixed mode). The primary risk is potential performance impact from losing ahead-of-time MSIL compilation.

Microsoft Reviewers: Open in CodeFlow

Migrate DirectWriteForwarder and System.Printing from /clr:pure to /clr:netcore (IJW mixed mode) in preparation for MSVC 14.51 which removes /clr:pure + /clr:netcore support. Changes: - CLRSupport and CompileAsManaged changed from pure to NetCore - Removed pure to NetCore conversion logic in Wpf.Cpp.props - Removed ijwhost.dll packaging exclusion (required for mixed-mode) - Added _M_ARM64 to architecture check in intsafe_private_copy.h Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Updates WPF’s C++/CLI build configuration to remove reliance on deprecated /clr:pure in favor of standard /clr:netcore (IJW mixed mode), aligning with upcoming MSVC toolset behavior and unblocking future builds.

Changes:

Switched CLRSupport and CompileAsManaged from pure to NetCore for DirectWriteForwarder and System.Printing.
Simplified Wpf.Cpp.props by removing the pure→NetCore remapping logic and updating ManagedCxx conditions.
Fixed an ARM64 compilation break by extending architecture detection in intsafe_private_copy.h.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Microsoft.DotNet.Wpf/src/System.Printing/System.Printing.vcxproj	Moves the project to `/clr:netcore` and allows ijwhost.dll to be packaged by removing the exclusion.
src/Microsoft.DotNet.Wpf/src/DirectWriteForwarder/DirectWriteForwarder.vcxproj	Moves the project to `/clr:netcore` and allows ijwhost.dll to be packaged by removing the exclusion.
src/Microsoft.DotNet.Wpf/src/DirectWriteForwarder/CPP/TrueTypeSubsetter/TtfDelta/intsafe_private_copy.h	Adds `_M_ARM64` handling to prevent ARM64 build errors.
eng/WpfArcadeSdk/tools/Wpf.Cpp.props	Updates shared build logic to recognize `CLRSupport=NetCore` and removes the old `pure` remap.

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miloush · 2026-04-13T10:40:58Z

Can we have some link/reference to the deprecation of the combination?

Agent-Logs-Url: https://github.com/dotnet/dotnet/sessions/85dfa847-a6bb-4471-863f-64e56545c584 Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

vinnarayana-msft · 2026-04-24T07:37:01Z

Can we have some link/reference to the deprecation of the combination?
@miloush

Please refer to this page
This page says:

/clr:pure is deprecated. The option is removed in Visual Studio 2017 and later. We recommend that you port code that must be pure MSIL to C#.

The driver also gives a deprecation warning if /clr:pure is used:

cl : Command line warning D9035 : option 'clr:pure' has been deprecated and will be removed in a future release

vinnarayana-msft · 2026-05-04T04:21:18Z

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Address PR review nit: remove CLRSupport=='pure' from DllRenameClause condition since no project sets CLRSupport to 'pure' anymore. Update comment to reference /clr:netcore instead of /clr:pure. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

vinnarayana-msft · 2026-05-08T11:45:21Z

/azp run

azure-pipelines · 2026-05-08T11:45:33Z

Azure Pipelines successfully started running 1 pipeline(s).

…otnet-wpf-int build 20260512.2 On relative base path root Microsoft.DotNet.Wpf.DncEng From Version 11.0.0-preview.2.26165.1 -> To Version 11.0.0-preview.2.26262.2

After the /clr:pure to /clr:NetCore migration (dotnet/wpf#11575), DirectWriteForwarder and System.Printing became mixed-mode C++/CLI assemblies that require ijwhost.dll at runtime. The DLL was being placed in the managed lib/ folder where it is not recognized by RuntimeList.xml, causing it to be missing from self-contained publish output. Move ijwhost.dll packaging logic to Packaging.targets centrally: exclude it from the lib/ folder and route it to runtimes/win-{arch}/native/ so it is properly included in the runtime pack manifest. Fixes dotnet/wpf#11651 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The previous approach tried to include ijwhost.dll from the WPF C++/CLI project output directories, but classic vcxproj files don't produce ijwhost.dll in their output (the .NET SDK's UseIJWHost mechanism only works for SDK-style projects). Instead, source ijwhost.dll directly from the Microsoft.NETCore.App.Host pack (where it is built by the runtime repo) and include it as a NativeRuntimeAsset in the WindowsDesktop shared framework runtime pack. This ensures it is present at runtime for the mixed-mode C++/CLI assemblies (DirectWriteForwarder.dll, System.Printing.dll) that depend on it after the /clr:pure to /clr:netcore migration (dotnet/wpf#11575). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Package ijwhost.dll as native asset for self-contained publish After the /clr:pure to /clr:NetCore migration (#11575), DirectWriteForwarder and System.Printing became mixed-mode C++/CLI assemblies that require ijwhost.dll at runtime. The DLL was being placed in the managed lib/ folder where it is not recognized by RuntimeList.xml, causing it to be missing from self-contained publish output. Exclude ijwhost.dll from the lib/ packaging and add it as a native asset under runtimes/win-{arch}/native/ so it is properly included in the runtime pack manifest. Fixes #11651 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * Move ijwhost.dll packaging logic to Packaging.targets Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

vinnarayana-msft requested review from a team and Copilot April 13, 2026 08:47

dotnet-policy-service Bot requested a review from dipeshmsft April 13, 2026 08:47

dotnet-policy-service Bot assigned vinnarayana-msft Apr 13, 2026

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Copilot started reviewing on behalf of vinnarayana-msft April 13, 2026 08:47 View session

Copilot AI reviewed Apr 13, 2026

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Comment thread eng/WpfArcadeSdk/tools/Wpf.Cpp.props Outdated

Copilot AI mentioned this pull request Apr 20, 2026

[test-only] Remove /clr:pure from WPF C++/CLI projects dotnet/dotnet#6125

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vinnarayana-msft and others added 2 commits April 22, 2026 12:00

Merge branch 'dotnet:main' into user/vinnarayana/remove-clr-pure-main

31c2e8d

Remove empty PropertyGroup left from /clr:pure removal

5f0341e

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dipeshmsft reviewed May 7, 2026

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Comment thread ...ft.DotNet.Wpf/src/DirectWriteForwarder/CPP/TrueTypeSubsetter/TtfDelta/intsafe_private_copy.h

Comment thread eng/WpfArcadeSdk/tools/Wpf.Cpp.props Outdated

harshit7962 previously approved these changes May 8, 2026

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Comment thread src/Microsoft.DotNet.Wpf/src/DirectWriteForwarder/DirectWriteForwarder.vcxproj

vinnarayana-msft dismissed harshit7962’s stale review via 2aad7ee May 8, 2026 06:25

dipeshmsft previously approved these changes May 8, 2026

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vinnarayana-msft and others added 2 commits May 11, 2026 09:01

Merge branch 'dotnet:main' into user/vinnarayana/remove-clr-pure-main

c0ee70a

Update dependencies from https://dev.azure.com/dnceng/internal/_git/d…

1fec6c8

…otnet-wpf-int build 20260512.2 On relative base path root Microsoft.DotNet.Wpf.DncEng From Version 11.0.0-preview.2.26165.1 -> To Version 11.0.0-preview.2.26262.2

vinnarayana-msft dismissed dipeshmsft’s stale review via 1fec6c8 May 12, 2026 10:06

himgoyalmicro approved these changes May 12, 2026

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dipeshmsft approved these changes May 12, 2026

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vinnarayana-msft merged commit e82267a into dotnet:main May 13, 2026
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dipeshmsft mentioned this pull request May 13, 2026

[main] Update dependencies from dnceng/internal/dotnet-wpf-int #11630

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dotnet-maestro Bot mentioned this pull request May 14, 2026

[main] Source code updates from dotnet/wpf dotnet/dotnet#6606

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mmanolova-msft mentioned this pull request May 26, 2026

Package ijwhost.dll as native asset for self-contained publish #11664

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mmanolova-msft mentioned this pull request Jun 3, 2026

[TEST][WPF] Package ijwhost.dll as native asset for self-contained publish dotnet/dotnet#7009

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Remove /clr:pure from WPF C++/CLI projects#11575

Remove /clr:pure from WPF C++/CLI projects#11575
vinnarayana-msft merged 6 commits into
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Description

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vinnarayana-msft commented Apr 13, 2026 •

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