Route QCall exceptions through marshalling by davidwrighton · Pull Request #132420 · dotnet/runtime

davidwrighton · 2026-08-17T17:30:31Z

Summary

route exceptions from BEGIN_QCALL/END_QCALL through an out QCallExceptionStatus value using a stateful source-generated custom marshaller
capture the managed throwable in runtime TLS, return an integer pending status to managed code, and clear and rethrow the throwable from QCallExceptionStatusMarshaller.FromUnmanaged
migrate only QCalls that use the exception-handling macros, explicitly initialize the status to zero, and leave non-throwing or otherwise unwrapped QCalls unchanged
locate the enclosing InlinedCallFrame during native exception capture instead of retaining release-build frame and current-thread locals
preserve binder-visible IL-stub helper signatures with managed wrappers and align native declarations across Windows x86, Apple, Mono, browser, and WASI builds
regenerate the checked-in browser and WASI CoreCLR call helpers for the updated QCall ABI

Testing

build.cmd clr+libs -c Checked (0 warnings, 0 errors)
build.cmd mono+libs (0 warnings, 0 errors)
build.cmd clr+libs -os browser -c Debug (0 warnings, 0 errors)
build.cmd clr.corelib -os osx -a x64 -c Debug (0 warnings, 0 errors)
build.cmd clr.runtime -a x86 -c Checked (0 warnings, 0 errors)
src\tasks\WasmAppBuilder\generate-coreclr-helpers.cmd -c Debug
AmbiguousImplementationException runtime test (exit code 100; exercises 12 sequential exceptions)
migration audit: 360 original BEGIN_QCALL implementations migrated and no original non-BEGIN_QCALL implementations migrated
git diff --check

The WASI build compiles the affected CoreCLR and generated helper translation units, then fails at the existing final-link issues for PAL_ProbeMemory, shm_open, and shm_unlink.

Note

This pull request description was generated by GitHub Copilot.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

dotnet-policy-service · 2026-08-17T17:41:27Z

Tagging subscribers to this area: @agocke
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR changes CoreCLR QCall exception propagation by routing exceptions thrown inside BEGIN_QCALL/END_QCALL through an out QCallException status value that is custom-marshalled back to managed code. The native side captures throwables onto the managed Thread, and the managed marshaller rethrows during unmarshalling, while leaving non-BEGIN_QCALL QCalls on the prior behavior.

Changes:

Introduce QCallException + QCallExceptionMarshaller and update managed QCall signatures to include an out QCallException for BEGIN_QCALL-based QCalls.
Update native QCall entrypoints and exception macros to capture exceptions instead of dispatching/rethrowing directly across the boundary.
Add the per-thread storage needed to temporarily root the captured throwable and rethrow it from managed unmarshalling.

Reviewed changes

Copilot reviewed 170 out of 170 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/libraries/System.Private.CoreLib/src/System/Threading/Wasi/WasiFinalizerScheduler.cs	Add conditional `out QCallException` to WASI finalizer QCalls.
src/libraries/System.Private.CoreLib/src/System/Threading/WaitHandle.Windows.cs	Pass conditional `out _` to updated reentrant wait QCall.
src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs	Update `CurrentOSThreadId` QCall invocation to include conditional `out _`.
src/libraries/System.Private.CoreLib/src/System/Threading/Lock.cs	Use updated `Environment.GetProcessorCount` signature under CORECLR.
src/libraries/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.cs	Thread `out QCallException` through multiple tracing/ALC QCalls.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/TypeMapLazyDictionary.cs	Add `out QCallException` to QCalls used by type map cache population/lookups.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/ObjectiveC/ObjectiveCMarshal.cs	Pass `out _` to updated ObjC marshal QCalls.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/Marshal.NoCom.cs	Extend internal signature with conditional `out _` under CORECLR.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/ComWrappers.cs	Call updated `RegisterIsRootedCallback` under CORECLR.
src/libraries/System.Private.CoreLib/src/System/Reflection/Assembly.cs	Update tracing QCall invocations to include `out _`.
src/libraries/System.Private.CoreLib/src/System/Environment.cs	Update `ProcessorCount` initialization to use CORECLR QCall signature.
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/XplatEventLogger.cs	Add `out QCallException` plumbing to xplat EventSource QCalls.
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipeEventProvider.cs	Add conditional `out _` to EventPipeInternal QCalls.
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipeEventDispatcher.Threads.cs	Add conditional `out _` to EventPipe session wait/disable QCalls.
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipeEventDispatcher.cs	Add conditional `out _` to EventPipe dispatcher QCalls.
src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipe.cs	Add conditional `out _` to EventPipe enable QCall.
src/libraries/System.Private.CoreLib/src/System/AppContext.cs	Add conditional `out _` to host property QCall path.
src/coreclr/vm/weakreferencenative.h	Add `QCallException*` to COM weak ref QCall signatures.
src/coreclr/vm/weakreferencenative.cpp	Add `QCallException*` parameter to COM weak ref QCall implementations.
src/coreclr/vm/wasm/entrypoints.h	Add `QCallException*` to WASI finalizer exported entrypoints.
src/coreclr/vm/versionresilienthashcode.h	Add `QCallException*` to version-resilient hash QCall signature.
src/coreclr/vm/versionresilienthashcode.cpp	Add `QCallException*` to version-resilient hash QCall implementation.
src/coreclr/vm/varargsnative.h	Add `QCallException*` to varargs iterator QCall signatures.
src/coreclr/vm/varargsnative.cpp	Add `QCallException*` to varargs iterator QCall implementations.
src/coreclr/vm/unsafeaccessors.cpp	Add `QCallException*` to unsafe accessor resolver QCall.
src/coreclr/vm/tailcallhelp.h	Add `QCallException*` to tailcall arg buffer allocation QCall.
src/coreclr/vm/tailcallhelp.cpp	Add `QCallException*` to tailcall arg buffer allocation QCall implementation.
src/coreclr/vm/stubhelpers.h	Add `QCallException*` to multiple interop/stub helper QCall signatures.
src/coreclr/vm/stackwalk.h	Add `QCallException*` to `AppendExceptionStackFrame` QCall signature.
src/coreclr/vm/reflectioninvocation.h	Add `QCallException*` to reflection invocation QCall signatures.
src/coreclr/vm/qcall.h	Update QCall guidance/comments and route BEGIN/END macros to capture dispatcher.
src/coreclr/vm/qcall.cpp	Add `QCallException::SetThrowable` implementation and thread rooting logic.
src/coreclr/vm/olevariant.h	Add `QCallException*` to VARIANT record conversion QCall signature.
src/coreclr/vm/olevariant.cpp	Add `QCallException*` to VARIANT record conversion QCall implementation.
src/coreclr/vm/object.h	Add `m_QCallException` field + setter on `ThreadBaseObject`.
src/coreclr/vm/nativelibrarynative.h	Add `QCallException*` to NativeLibrary load-by-name QCall signature.
src/coreclr/vm/nativelibrarynative.cpp	Add `QCallException*` to NativeLibrary load-by-name QCall implementation.
src/coreclr/vm/nativeeventsource.h	Add `QCallException*` to EventSource/perf tracing QCall signatures.
src/coreclr/vm/multicorejit.h	Add `QCallException*` to MultiCoreJIT QCall signatures.
src/coreclr/vm/multicorejit.cpp	Add `QCallException*` to MultiCoreJIT QCall implementations.
src/coreclr/vm/mlinfo.cpp	Add `QCallException*` to `StubHelpers_CreateCustomMarshaler` QCall implementation.
src/coreclr/vm/method.hpp	Add `QCallException*` to unsafe accessor resolver declaration.
src/coreclr/vm/managedmdimport.hpp	Add `QCallException*` to metadata enum QCall signature.
src/coreclr/vm/managedmdimport.cpp	Add `QCallException*` to metadata enum QCall implementation.
src/coreclr/vm/loaderallocator.hpp	Add `QCallException*` to loader allocator destroy QCall signature.
src/coreclr/vm/loaderallocator.cpp	Add `QCallException*` to loader allocator destroy QCall implementation.
src/coreclr/vm/JitQCallHelpers.h	Add `QCallException*` to JIT helper QCall signatures.
src/coreclr/vm/jithelpers.cpp	Add `QCallException*` to JIT helper QCalls and adjust handler installation in rare paths.
src/coreclr/vm/interoplibinterface.h	Add `QCallException*` to ObjC/Java marshal QCall signatures.
src/coreclr/vm/interoplibinterface_objc.cpp	Add `QCallException*` to ObjC marshal QCall implementations.
src/coreclr/vm/interoplibinterface_java.cpp	Add `QCallException*` to Java marshal QCall implementations.
src/coreclr/vm/interoplibinterface_comwrappers.h	Add `QCallException*` to ComWrappers QCall signatures.
src/coreclr/vm/interoplibinterface_comwrappers.cpp	Add `QCallException*` to ComWrappers QCall implementations.
src/coreclr/vm/ilmarshalers.h	Add `QCallException*` to safe array marshaler QCall signatures.
src/coreclr/vm/ilmarshalers.cpp	Add `QCallException*` to safe array marshaler QCall implementations.
src/coreclr/vm/finalizerthread.cpp	Add `QCallException*` to WASI finalizer QCall implementations.
src/coreclr/vm/exceptmacros.h	Introduce `QCallException` native struct and capture-dispatcher exception macros.
src/coreclr/vm/exceptionhandlingqcalls.h	Add `QCallException*` to exception-handling-related QCall signatures.
src/coreclr/vm/exceptionhandling.cpp	Add `QCallException*` to exception-handling-related QCall implementations.
src/coreclr/vm/excep.cpp	Add `QCallException*` to message QCalls and introduce QCall-specific unwind helper.
src/coreclr/vm/eventpipeinternal.h	Add `QCallException*` to EventPipeInternal QCall signatures.
src/coreclr/vm/eventpipeinternal.cpp	Add `QCallException*` to EventPipeInternal QCall implementations.
src/coreclr/vm/debugdebugger.h	Add `QCallException*` to debugger/stacktrace QCall signatures.
src/coreclr/vm/debugdebugger.cpp	Add `QCallException*` to debugger/stacktrace QCall implementations.
src/coreclr/vm/customattribute.h	Add `QCallException*` to custom attribute QCall signatures.
src/coreclr/vm/customattribute.cpp	Add `QCallException*` to custom attribute QCall implementations.
src/coreclr/vm/corelib.h	Add corelib field mapping for new thread `_qcallException` field.
src/coreclr/vm/coreassemblyspec.cpp	Add `QCallException*` to assembly spec initialization QCall signature.
src/coreclr/vm/comsynchronizable.h	Add `QCallException*` to thread/lock-related QCall signatures.
src/coreclr/vm/comsynchronizable.cpp	Add `QCallException*` to thread/lock-related QCall implementations.
src/coreclr/vm/commodule.h	Add `QCallException*` to Reflection.Emit module builder QCall signatures.
src/coreclr/vm/commodule.cpp	Add `QCallException*` to Reflection.Emit module builder QCall implementations.
src/coreclr/vm/comdependenthandle.h	Add `QCallException*` to dependent handle QCall signatures.
src/coreclr/vm/comdependenthandle.cpp	Add `QCallException*` to dependent handle QCall implementations.
src/coreclr/vm/comdelegate.h	Add `QCallException*` to delegate-related QCall signatures.
src/coreclr/vm/comdelegate.cpp	Add `QCallException*` to delegate-related QCall implementations.
src/coreclr/vm/clrconfignative.h	Add `QCallException*` to CLR config QCall signature.
src/coreclr/vm/clrconfignative.cpp	Add `QCallException*` to CLR config QCall implementation.
src/coreclr/vm/arraynative.h	Add `QCallException*` to array creation/ctor QCall signatures.
src/coreclr/vm/arraynative.cpp	Add `QCallException*` to array creation/ctor QCall implementations.
src/coreclr/vm/appdomainnative.hpp	Add `QCallException*` to AppDomain/AppContext/string intern QCall signatures.
src/coreclr/vm/appdomainnative.cpp	Add `QCallException*` to AppDomain/AppContext/string intern QCall implementations.
src/coreclr/System.Private.CoreLib/System.Private.CoreLib.csproj	Include new `QCallException.cs` in CoreCLR CoreLib build.
src/coreclr/System.Private.CoreLib/src/System/Variant.cs	Add `out QCallException` to COM VARIANT-related QCalls.
src/coreclr/System.Private.CoreLib/src/System/ValueType.cs	Add `out QCallException` to ValueType helper QCalls.
src/coreclr/System.Private.CoreLib/src/System/TypeLoadException.CoreCLR.cs	Add `out QCallException` to message-formatting QCall.
src/coreclr/System.Private.CoreLib/src/System/Threading/ObjectHeader.CoreCLR.cs	Add `out QCallException` to lock-object QCall.
src/coreclr/System.Private.CoreLib/src/System/String.CoreCLR.cs	Add `out QCallException` to string intern/is-interned QCalls.
src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CreateUninitializedCache.CoreCLR.cs	Add `out QCallException` to create-uninitialized info QCall.
src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs	Add `out QCallException` to multiple RuntimeType/reflection QCalls.
src/coreclr/System.Private.CoreLib/src/System/RuntimeType.BoxCache.cs	Add `out QCallException` to boxing cache QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/TrackerObjectManager.CoreCLR.cs	Add `out QCallException` to wrapper-cache registration QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/ObjectiveCMarshal.CoreCLR.cs	Add `out QCallException` to ObjC marshal QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeLibrary.CoreCLR.cs	Add `out QCallException` to NativeLibrary load QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/Java/JavaMarshal.CoreCLR.cs	Add `out QCallException` to Java marshal QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/GCHandle.CoreCLR.cs	Add `out QCallException` to GCHandle QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/InteropServices/ComWrappers.CoreCLR.cs	Add `out QCallException` to ComWrappers QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/ExceptionServices/InternalCalls.cs	Add `out QCallException` to EH-related QCall internal calls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/DependentHandle.cs	Add `out QCallException` to dependent handle QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/ControlledExecution.CoreCLR.cs	Add `out QCallException` to `ThreadNative_Abort` QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/VirtualDispatchHelpers.cs	Add `out QCallException` to virtual dispatch resolver QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/StaticsHelpers.cs	Add `out QCallException` to thread statics QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/QCallException.cs	Introduce managed QCall exception status type + custom marshaller.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/InitHelpers.cs	Add `out QCallException` to init-class QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/GenericsHelpers.cs	Add `out QCallException` to generic handle worker QCall.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/CastHelpers.cs	Add `out QCallException` to cast helper QCalls.
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs	Add `out QCallException` to async continuation QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/TypeNameResolver.CoreCLR.cs	Add `out QCallException` to unsafe accessor resolver QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeModule.cs	Add `out QCallException` to module name/types QCalls.
src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeCustomAttributeData.cs	Add `out QCallException` to custom attribute QCalls.
src/coreclr/System.Private.CoreLib/src/System/Reflection/MethodBase.CoreCLR.cs	Add `out QCallException` to GetCurrentMethod QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/MetadataUpdater.cs	Add `out QCallException` to metadata update QCalls.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Metadata/AssemblyExtensions.cs	Add `out QCallException` to raw metadata QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/MdImport.cs	Add `out QCallException` to metadata import enum QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/LoaderAllocator.cs	Add `out QCallException` to loader allocator destroy QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimePropertyBuilder.cs	Add `out _` to Reflection.Emit QCall invocations.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeParameterBuilder.cs	Add `out _` to Reflection.Emit QCall invocations.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeMethodBuilder.cs	Add `out _` to Reflection.Emit QCall invocations.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeFieldBuilder.cs	Add `out _` to Reflection.Emit QCall invocations.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeEventBuilder.cs	Add `out _` to Reflection.Emit QCall invocations.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeAssemblyBuilder.cs	Add `out QCallException` to dynamic assembly creation QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.CoreCLR.cs	Add `out _` to compile-method QCall invocation.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicILGenerator.cs	Add `out _` to destroy handle QCall invocation.
src/coreclr/System.Private.CoreLib/src/System/Reflection/AssemblyName.CoreCLR.cs	Add `out QCallException` to assembly spec init QCall.
src/coreclr/System.Private.CoreLib/src/System/Reflection/Assembly.CoreCLR.cs	Add `out QCallException` to assembly lookup QCalls.
src/coreclr/System.Private.CoreLib/src/System/Object.CoreCLR.cs	Add `out _` to clone allocation QCall invocation.
src/coreclr/System.Private.CoreLib/src/System/IO/Stream.CoreCLR.cs	Add `out QCallException` to overridden-check QCall.
src/coreclr/System.Private.CoreLib/src/System/IO/FileLoadException.CoreCLR.cs	Add `out QCallException` to file load message QCalls.
src/coreclr/System.Private.CoreLib/src/System/Exception.CoreCLR.cs	Add `out QCallException` to exception-related QCalls.
src/coreclr/System.Private.CoreLib/src/System/Environment.CoreCLR.cs	Add `out QCallException` to Environment QCalls (Exit/FailFast/GetProcessorCount).
src/coreclr/System.Private.CoreLib/src/System/Enum.CoreCLR.cs	Add `out QCallException` to enum values/names QCall.
src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackTrace.CoreCLR.cs	Add `out QCallException` to stack trace frames QCall.
src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackFrame.CoreCLR.cs	Add `out QCallException` to method-desc-from-IP QCall.
src/coreclr/System.Private.CoreLib/src/System/Diagnostics/Debugger.cs	Add `out QCallException` to debugger break/notification QCalls.
src/coreclr/System.Private.CoreLib/src/System/Delegate.CoreCLR.cs	Add `out QCallException` to delegate binding/construct QCalls.
src/coreclr/System.Private.CoreLib/src/System/ComAwareWeakReference.CoreCLR.cs	Add `out QCallException` to COM weak ref QCalls.
src/coreclr/System.Private.CoreLib/src/System/CLRConfig.cs	Add `out QCallException` to CLR config QCall.
src/coreclr/System.Private.CoreLib/src/System/Array.CoreCLR.cs	Add `out QCallException` to array creation/ctor QCalls.
src/coreclr/System.Private.CoreLib/src/System/ArgIterator.cs	Add `out QCallException` to varargs iterator QCalls.
src/coreclr/System.Private.CoreLib/src/System/AppContext.CoreCLR.cs	Add `out QCallException` to host property QCall.
src/coreclr/System.Private.CoreLib/src/Internal/VersionResilientHashCode.CoreCLR.cs	Add `out QCallException` to version-resilient hash QCall.
src/coreclr/System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/ThrowHelpers.cs	Add `out QCallException` to throw-helper QCalls.
src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/StackFrameIterator.cs	Add conditional `out _` to EH QCall internal calls.
src/coreclr/nativeaot/Runtime.Base/src/System/Runtime/ExceptionHandling.cs	Add conditional `out _` to EH QCall internal calls.

+
+            if (exceptionPending == 1)
+            {
+                Exception exception = _thread.GetAndClearQCallException();


+        {                                           \
+            GCX_COOP();                             \
+            OBJECTREF throwable = ExInfo::CreateThrowable(ex.GetExceptionRecord(), FALSE); \
+            qcallError->SetThrowable(throwable);    \
+        }                                           \


azure-pipelines · 2026-08-17T21:33:02Z

Azure Pipelines: Successfully started running 3 pipeline(s). 13 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

jkotas · 2026-08-17T23:12:18Z

+namespace System.Runtime.CompilerServices
+{
+    [NativeMarshalling(typeof(QCallExceptionMarshaller))]
+    internal readonly struct QCallException


Naming nit: The name makes it look like an exception type per .NET naming guidelines, but it is not actually an exception type. Copilot suggests QCallExceptionStatus as a better name:

Yes. QCallException is misleading because the type is an out-only marshalling protocol/status value, not an exception object.

My preferred name would be:

internal readonly struct QCallExceptionStatus

This communicates that:

it is associated with QCall exception propagation;

it is a status/result value;

it is not itself throwable or derived from Exception.

Other reasonable alternatives:

Name Comments

QCallExceptionStatus Best overall; explicit and reasonably concise.

QCallExceptionPropagation Emphasizes that its purpose is transferring a pending exception across the boundary. A little abstract for a value type.

QCallExceptionResult Good if the parameter is viewed as an invocation result, although “result” may imply the exception itself is returned.

QCallThrowStatus Short and accurately describes the behavior, but “throw” may sound like an operation rather than a status.

QCallErrorStatus Avoids calling it an exception, but loses the important distinction that it carries managed exceptions rather than ordinary error codes.

QCallExceptionToken Suggests an opaque token, which is not quite accurate because the marshaller retrieves the exception from the managed thread.

QCallExceptionCarrier Describes the mechanism, but sounds like it contains the exception, which the empty managed struct does not.

I would also consider renaming the native pointer consistently:

QCallExceptionStatus* qcallExceptionStatus

or, if using the shorter managed name:

QCallThrowStatus* qcallThrowStatus

For example:

[NativeMarshalling(typeof(QCallExceptionStatusMarshaller))] internal readonly struct QCallExceptionStatus { }

private static partial void SomeQCall( ..., out QCallExceptionStatus exceptionStatus);

The strongest alternative if you want to avoid Exception entirely is probably:

QCallThrowStatus

However, I would favor QCallExceptionStatus because it preserves the semantic connection to the managed exception being propagated while making clear that the type itself is merely a status marker.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Copilot

Pull request overview

Copilot reviewed 170 out of 170 changed files in this pull request and generated 1 comment.

        private static IntPtr AllocateReferenceTrackingHandle(object obj)
            => AllocateReferenceTrackingHandle(ObjectHandleOnStack.Create(ref obj));


…calls

Copilot

Pull request overview

Copilot reviewed 171 out of 171 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/QCallException.cs:26

QCallExceptionMarshaller.FromUnmanaged only treats exceptionPending == 1 as an exception. Since the native representation is an INT32 flag, using a non-zero check (!= 0) is more robust against future expansion or accidental non-1 values, and avoids silently skipping exception propagation if the flag is ever set to another non-zero value.

Add managed forwarding overloads for helpers invoked by native IL stub generation so their CoreLib binder signatures remain stable after adding QCall exception parameters. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Keep the CoreCLR QCall exception argument and Mono zero-argument call in separately formatted conditional branches so both CoreLib builds satisfy style validation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Update browser and WASI interpreter-to-managed thunks for the QCall exception argument and refresh generated P/Invoke tables. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Copilot

Pull request overview

Copilot reviewed 175 out of 175 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/coreclr/vm/exceptmacros.h:220

QCallException is custom-marshalled as an int on the managed side, but the native side now defines it as a struct. Since the managed/native ABI contract depends on this staying a single INT32, add a static_assert to prevent accidental layout changes from silently breaking QCall exception propagation.

Rename the managed and native status carrier to QCallExceptionStatus and update its custom marshaller. Restore runtime-neutral Objective-C wrappers, align the AssemblyName declaration, and remove exception capture from the non-throwing GC mode helper. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Copilot

Pull request overview

Copilot reviewed 174 out of 174 changed files in this pull request and generated 1 comment.

Suppressed comments (1)

src/coreclr/vm/excep.cpp:6713

OBJECTREF throwable created from ExInfo::CreateThrowable(...) is used without GCPROTECT. In cooperative mode, the thread can be suspended for GC before the reference is published to a scanned root (TLS), which risks losing the throwable before SetThrowable stores it.

+    OBJECTREF orThrowable = CLRException::GetThrowableFromException(pException);
+    CONSISTENCY_CHECK(orThrowable != NULL);
+    pQCallException->SetThrowable(orThrowable);


davidwrighton · 2026-08-20T00:22:16Z

I built Release runtime + libraries at the mainline parent (a0f44dfcb92) and at this branch head (780f494666e), then benchmarked short successful QCalls in both host orders. The averaged deltas were -0.38% for string.IsInterned (hit), +0.53% for string.IsInterned (miss), and +0.78% for string.Intern (hit), all below 1 ns. Run-order variation was larger than the measured deltas, so this test found no consistent success-path performance regression above the local noise floor.

Benchmark source, full result table, methodology, and reproduction commands: https://gist.github.com/davidwrighton/3596168f4db88a825f6038ccecac13fe

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+using System.Runtime.ExceptionServices;
+using System.Runtime.InteropServices.Marshalling;
+using System.Threading;
+
+namespace System.Runtime.CompilerServices
+{
+    [NativeMarshalling(typeof(QCallExceptionStatusMarshaller))]
+    internal readonly struct QCallExceptionStatus
+    {
+    }
+
+    [CustomMarshaller(typeof(QCallExceptionStatus), MarshalMode.ManagedToUnmanagedOut, typeof(QCallExceptionStatusMarshaller))]
+    internal struct QCallExceptionStatusMarshaller
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void FromUnmanaged(int exceptionPending)
+        {
+            if (exceptionPending == 1)
+            {
+                HandleException();
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public QCallExceptionStatus ToManaged() => default;
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Free() { }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void HandleException()
+        {
+            Exception exception = Thread.GetAndClearQCallException();
+
+            // Throw during unmarshalling so QCall exception propagation remains as close as
+            // possible to throwing directly from native code, as QCalls did previously.
+            ExceptionDispatchInfo.Throw(exception);
+        }
+    }
+}


Resolve QCall signature conflicts by preserving upstream API updates while retaining explicit exception-status propagation for QCalls that use BEGIN_QCALL. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Squash the LibraryImportErrorHandler branch changes into one independently revertable commit, including hidden-return-value handling and generator tests. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Return pointer-sized exception statuses from native QCalls and process them through LibraryImport hidden-return error handlers. Preserve exact exceptions with GC handles, recreate special exceptions through the runtime, remove thread-local storage, and regenerate WebAssembly helpers. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b31492bf-57a2-4c93-8e29-1bc8e555289d

Release the caught native exception after transferring its throwable to the QCall status, and preserve the previous customer-visible COM exception stack trace. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: df97bfcc-e3cb-470b-be04-ac63dfebcb4a

davidwrighton added 3 commits August 14, 2026 15:44

Initial infrastructure for new eh handling in qcalls

49ef2ee

Route QCall exceptions through marshalling

e8d8016

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 97d405d-8e39-4e76-afe4-2f94b74ecfa2

Limit QCall exception arguments to wrapped calls

01c1f90

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Remove excess use of current thread static

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Checkout failure: "Git fetch failed with exit code 128" dotnet/arcade#9009

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The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

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davidwrighton added 2 commits August 17, 2026 14:11

Fix the build

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Fix build

35b6717

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LibraryImportGenerator.Unit.Tests crashing on linux-x64 mono interpreter #100800

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[ci-scan] Build break: Windows Helix work items fail on unexpanded $HELIX_PYTHONPATH in gen-debug-dump-docs post-command #131382

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Initialize QCall exception status

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Comment thread ...reclr/System.Private.CoreLib/src/System/Runtime/InteropServices/ObjectiveCMarshal.CoreCLR.cs

Comment on lines 62 to 63

private static IntPtr AllocateReferenceTrackingHandle(object obj)

=> AllocateReferenceTrackingHandle(ObjectHandleOnStack.Create(ref obj));

Move qcall exception to tls data to avoid the Thread object

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Merge branch 'main' of https://github.com/dotnet/runtime into fixup_q…

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…calls

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Comment thread src/coreclr/vm/excep.cpp Outdated

Comment on lines +6698 to +6700

OBJECTREF orThrowable = CLRException::GetThrowableFromException(pException);

CONSISTENCY_CHECK(orThrowable != NULL);

pQCallException->SetThrowable(orThrowable);

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slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

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davidwrighton added 4 commits August 24, 2026 17:09

Merge upstream/main into fixup_qcalls

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Fix Unix XplatEventLogger QCall invocation

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Microsoft.Extensions.Configuration.Test.ConfigurationTests.DeletingFilesThatRedefineKeysWithReload: Assert.True() failure #132147

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Merge upstream/main into fixup_qcalls

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CompositeMLDsaCngTests failing on Windows #132830

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[Test Failure] System.Net.Quic.Tests.MsQuicTests.Client_CertificateWithEphemeralKey_Throws #132831

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Route QCall exceptions through marshalling - #132420

Route QCall exceptions through marshalling#132420
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Name	Comments
`QCallExceptionStatus`	Best overall; explicit and reasonably concise.
`QCallExceptionPropagation`	Emphasizes that its purpose is transferring a pending exception across the boundary. A little abstract for a value type.
`QCallExceptionResult`	Good if the parameter is viewed as an invocation result, although “result” may imply the exception itself is returned.
`QCallThrowStatus`	Short and accurately describes the behavior, but “throw” may sound like an operation rather than a status.
`QCallErrorStatus`	Avoids calling it an exception, but loses the important distinction that it carries managed exceptions rather than ordinary error codes.
`QCallExceptionToken`	Suggests an opaque token, which is not quite accurate because the marshaller retrieves the exception from the managed thread.
`QCallExceptionCarrier`	Describes the mechanism, but sounds like it contains the exception, which the empty managed struct does not.

		private static IntPtr AllocateReferenceTrackingHandle(object obj)
		=> AllocateReferenceTrackingHandle(ObjectHandleOnStack.Create(ref obj));

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davidwrighton commented Aug 17, 2026 •

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