[browser][coreCLR] no COM, no swift by pavelsavara · Pull Request #125083 · dotnet/runtime

pavelsavara · 2026-03-02T23:23:43Z

Trim COM/SEH-related code for non-Windows targets (Browser WASM)

Summary

This PR conditionally compiles out COM interop, SEH exception, and Windows-only code paths from the CoreCLR runtime when targeting non-Windows platforms (primarily Browser/WASM). It also removes reverse P/Invoke thunks for ComActivator methods that are not applicable on Browser, and teaches the WASM PInvokeCollector to skip callbacks on types marked as unsupported on Browser.

Changes

SEH exception trimming (`#ifdef TARGET_WINDOWS`)

ex.h / ex.cpp: Wrap the SEHException class definition, constructors, and GetHR()/GetMessage() implementations in #ifdef TARGET_WINDOWS.
clrex.cpp: Wrap the SEHException handling path in GetThrowableFromException so non-Windows falls through to the generic HRException/COMException/DelegatingException handler.
dacfn.cpp: Wrap the SEHException rethrow logic in DacExceptionFilter in #ifdef TARGET_WINDOWS.
rexcep.h: Wrap the DEFINE_EXCEPTION for SEHException in #ifdef TARGET_WINDOWS.
excep.cpp:
- MapWin32FaultToCOMPlusException default case: returns kSEHException on Windows, kException with _ASSERTE(!"Expected to be unreachable") on non-Windows.
- Wrap SEHException references in DebugIsEECxxExceptionPointer in #ifdef TARGET_WINDOWS.

Move `CallOutFilter` / `FilterAccessViolation` from generic code

excep.cpp / excep.h: Remove CallOutFilter, CallOutFilterParam, and FilterAccessViolation — these are SEH-specific helpers only used from COM interop code.
interoputil.cpp: Move CallOutFilter and CallOutFilterParam here, where they are actually used (already inside #ifdef FEATURE_COMINTEROP compilation unit).

COM-specific type trimming (`#ifdef FEATURE_COMINTEROP`)

rexcep.h: Move InvalidOleVariantTypeException inside the existing #ifdef FEATURE_COMINTEROP block.
corelib.h: Wrap COMVARIANT class definition in #if defined(FEATURE_COMINTEROP).
metasig.h: Wrap ComVariant-related metasig definitions in #ifdef FEATURE_COMINTEROP.
olevariant.cpp: Wrap VT_VARIANT → CLASS__COMVARIANT mapping in #ifdef FEATURE_COMINTEROP.
Marshal.cs (shared CoreLib): Wrap COR_E_INVALIDOLEVARIANTTYPE → InvalidOleVariantTypeException mapping in #if FEATURE_COMINTEROP.

Swift types Apple-only (`#ifdef TARGET_APPLE`)

corelib.h: Wrap SwiftSelf, SwiftSelf<T>, SwiftError, SwiftIndirectResult class definitions in #ifdef TARGET_APPLE.

Platform annotation

ComActivator.PlatformNotSupported.cs: Add [SupportedOSPlatform("windows")] attribute so the WASM toolchain can detect it as unsupported.

WASM reverse call helpers

callhelpers-reverse.cpp: Remove three ComActivator reverse P/Invoke thunks (GetClassFactoryForTypeInternal, RegisterClassForTypeInternal, UnregisterClassForTypeInternal) and their entries in g_ReverseThunks. Rename OnThreadExiting → OnThreadExited to match the upstream API rename.

WASM PInvoke collector - skip browser-unsupported types

PInvokeCollector.cs: Add IsUnsupportedOnBrowser method that checks for [UnsupportedOSPlatform("browser")] or [SupportedOSPlatform(...)] without "browser" on the declaring type. Callbacks on unsupported types are skipped during WASM app build, avoiding link errors for COM-related methods.

WASM call helper additions (unrelated fixups merged from main)

callhelpers-interp-to-managed.cpp: Add CallFunc_I32_I32_I32_RetI64 thunk and liii signature entry.
callhelpers-pinvoke.cpp: Add SystemNative_ReadV and SystemNative_WriteV P/Invoke declarations and table entries (count 92 → 94).

dotnet-policy-service · 2026-03-02T23:24:49Z

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Copilot

Pull request overview

This PR aims to reduce trimmed size for browser-WASM CoreCLR builds by removing/gating roots and native support code for features that aren’t supported in the browser (COM/interop-related pieces, DynamicInterfaceCastable, Swift interop, and intrinsics metadata rooting).

Changes:

Filters reverse P/Invoke stub generation for types marked [UnsupportedOSPlatform("browser")] and annotates ComActivator accordingly.
Gates ILLink rooting for ComponentActivator.GetFunctionPointer behind the existing native-hosting feature switch.
Adds TARGET_WASM guards to exclude DynamicInterfaceCastable native support on WASM and trims related ILLink roots / metadata retention paths.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/tasks/WasmAppBuilder/generate-coreclr-helpers.cmd	Updates helper generation script used for CoreCLR WASM callhelper regeneration.
src/tasks/WasmAppBuilder/coreclr/PInvokeCollector.cs	Skips generating reverse P/Invoke callback stubs for types unsupported on browser.
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/CompExactlyDependsOnAttribute.cs	Removes `CompExactlyDependsOnAttribute` metadata for browser/WASI builds to improve trimming.
src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Shared.xml	Gates `ComponentActivator.GetFunctionPointer` rooting behind the native-hosting feature switch.
src/coreclr/vm/wasm/callhelpers-reverse.cpp	Regenerated reverse thunk table reflecting removed callbacks.
src/coreclr/vm/wasm/callhelpers-pinvoke.cpp	Regenerated P/Invoke table reflecting upstream removals.
src/coreclr/vm/virtualcallstub.cpp	Removes DynamicInterfaceCastable resolver path from WASM builds.
src/coreclr/vm/rexcep.h	Attempts to exclude interop exception types from WASM ILLink descriptor generation.
src/coreclr/vm/methodtable.cpp	Removes IDynamicInterfaceCastable special method resolution on WASM.
src/coreclr/vm/jithelpers.cpp	Removes IDynamicInterfaceCastable cast path on WASM.
src/coreclr/vm/dynamicinterfacecastable.h	Wraps DynamicInterfaceCastable API surface out of WASM builds.
src/coreclr/vm/dynamicinterfacecastable.cpp	Wraps DynamicInterfaceCastable implementation out of WASM builds.
src/coreclr/vm/corelib.h	Attempts to exclude Swift interop and ComVariant from WASM ILLink descriptor generation; removes DynamicInterfaceCastableHelpers from WASM.
src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.PlatformNotSupported.cs	Marks `ComActivator` as unsupported on browser to suppress reverse stub generation.

src/tasks/WasmAppBuilder/generate-coreclr-helpers.cmd

src/coreclr/vm/corelib.h

src/coreclr/vm/rexcep.h

src/tasks/WasmAppBuilder/coreclr/PInvokeCollector.cs

src/coreclr/vm/corelib.h

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

src/coreclr/vm/rexcep.h

src/coreclr/vm/corelib.h

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

src/coreclr/vm/excep.cpp

src/coreclr/vm/excep.h

Copilot

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

src/coreclr/vm/excep.h

Copilot

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

src/coreclr/vm/interoputil.cpp

src/coreclr/vm/olevariant.cpp

jkotas · 2026-03-25T16:45:41Z

Any numbers for how much this saves? I like to have numbers for anything that claims to be a perf improvement.

pavelsavara · 2026-03-25T16:50:30Z

Any numbers for how much this saves? I like to have numbers for anything that claims to be a perf improvement.

This is not about perf at all.
It started as much bigger IL trimming PR, but I was not able to reproduce Intrinsics at some point.
So, what we have right now is just cleanup. I can measure size difference, but it would not be big deal.

Copilot

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

src/tasks/WasmAppBuilder/coreclr/PInvokeCollector.cs

pavelsavara added this to the 11.0.0 milestone Mar 2, 2026

pavelsavara self-assigned this Mar 2, 2026

Copilot AI review requested due to automatic review settings March 2, 2026 23:23

pavelsavara added arch-wasm WebAssembly architecture area-VM-coreclr size-reduction Issues impacting final app size primary for size sensitive workloads os-browser Browser variant of arch-wasm labels Mar 2, 2026

dotnet-policy-service bot added the linkable-framework Issues associated with delivering a linker friendly framework label Mar 2, 2026

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pavelsavara force-pushed the browser_trim_COM branch from c066985 to 77b2da7 Compare March 3, 2026 07:37

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pavelsavara marked this pull request as ready for review March 18, 2026 08:53

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This was referenced Mar 24, 2026

Android arm32 device not found (armeabi-v7a architecture unavailable) #125440

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System.Formats.Nrbf.Tests.EdgeCaseTests.CanReadArrayOfAnySize times out on checked coreclr #125994

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Copilot AI mentioned this pull request Mar 24, 2026

Fix CanReadArrayOfAnySize timeout on checked coreclr by skipping the 2 GB case on slow runtimes #126006

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pavelsavara requested a review from jkotas March 24, 2026 14:22

Merge branch 'main' into browser_trim_COM

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rever COMVARIANT

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Merge branch 'main' into browser_trim_COM

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pavelsavara commented Mar 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Trim COM/SEH-related code for non-Windows targets (Browser WASM)

Summary

Changes

SEH exception trimming (#ifdef TARGET_WINDOWS)

Move CallOutFilter / FilterAccessViolation from generic code

COM-specific type trimming (#ifdef FEATURE_COMINTEROP)

Swift types Apple-only (#ifdef TARGET_APPLE)

Platform annotation

WASM reverse call helpers

WASM PInvoke collector - skip browser-unsupported types

WASM call helper additions (unrelated fixups merged from main)

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pavelsavara commented Mar 2, 2026 •

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SEH exception trimming (`#ifdef TARGET_WINDOWS`)

Move `CallOutFilter` / `FilterAccessViolation` from generic code

COM-specific type trimming (`#ifdef FEATURE_COMINTEROP`)

Swift types Apple-only (`#ifdef TARGET_APPLE`)