Replace `CallDescrWorker` with `UnmanagedCallersOnlyAttribute` pattern

[AaronRobinsonMSFT]

This issue tracks the work to replace MethodDescCallSite / CallDescrWorker infrastructure with more efficient UnmanagedCallersOnly reverse P/Invoke calls for invoking managed code from native code.

Benefits

• Significantly reduced overhead for VM-to-managed calls
• Uses existing reverse P/Invoke infrastructure instead of the expensive CallDescrWorker mechanism
• Better alignment with modern interop patterns

Pattern

The conversion pattern involves:

1. Adding [UnmanagedCallersOnly] wrappers to managed methods with an Exception* out-parameter
2. Using the UnmanagedCallersOnlyCaller template class in C++ to invoke these methods
3. Updating metasig.h and corelib.h with appropriate signatures

Notes

• The UnmanagedCallersOnlyCaller template class is defined in callhelpers.h and can be used to invoke the target.
• WASM builds require regenerating callhelpers-reverse.cpp when adding new UCO methods.

Example PR to follow: #123832

---

Conversion Tasks

Priority 1: Cross-Platform, Simple Conversions

These are straightforward conversions on code paths that run on all platforms.

AppDomain / Assembly Loading (appdomain.cpp) - #123967

• METHOD__ASSEMBLYLOADCONTEXT__ON_ASSEMBLY_LOAD in AppDomain::RaiseAssemblyLoadEvent
• METHOD__ASSEMBLYLOADCONTEXT__ON_TYPE_RESOLVE in AppDomain::RaiseTypeResolveEventThrowing
• METHOD__ASSEMBLYLOADCONTEXT__ON_RESOURCE_RESOLVE in AppDomain::RaiseResourceResolveEvent
• METHOD__ASSEMBLYLOADCONTEXT__ON_ASSEMBLY_RESOLVE in AppDomain::RaiseAssemblyResolveEvent
• METHOD__ASSEMBLYLOADCONTEXT__RESOLVE in AppDomain::BindAssemblySpec
• METHOD__ASSEMBLYLOADCONTEXT__RESOLVESATELLITEASSEMBLY in AppDomain::BindSatelliteResourceByResourceRoots
• METHOD__ASSEMBLYLOADCONTEXT__RESOLVEUSINGEVENT in AppDomain::RaiseLoadFileEvent

Loader Allocator (loaderallocator.cpp) - #124303

• METHOD__LOADERALLOCATOR__CTOR in LoaderAllocator::Init

Custom Marshaler (custommarshalerinfo.cpp) - #124440

• GetCustomMarshaler method lookup in CustomMarshalerInfo::CustomMarshalerInfo

Dynamic Methods / Resolver (dynamicmethod.cpp) - #124303

• METHOD__RESOLVER__GET_JIT_CONTEXT in LCGMethodResolver::GetJitContext
• METHOD__RESOLVER__GET_CODE_INFO in LCGMethodResolver::GetCodeInfo
• METHOD__RESOLVER__GET_LOCALS_SIGNATURE in LCGMethodResolver::GetLocalSig
• METHOD__RESOLVER__GET_STRING_LITERAL in LCGMethodResolver::GetStringLiteral

Interop Utilities (interoputil.cpp) - #124303

• METHOD__CULTURE_INFO__INT_CTOR in GetCultureInfoForLCID
• METHOD__COLORMARSHALER__CONVERT_TO_MANAGED in ConvertOleColorToSystemColor
• METHOD__COLORMARSHALER__CONVERT_TO_NATIVE in ConvertSystemColorToOleColor

Threads / Culture (threads.cpp) - #124303

• METHOD__CULTURE_INFO__GET_CURRENT_CULTURE / METHOD__CULTURE_INFO__GET_CURRENT_UI_CULTURE in Thread::GetCultureInfo
• METHOD__CULTURE_INFO__SET_CURRENT_CULTURE / METHOD__CULTURE_INFO__SET_CURRENT_UI_CULTURE in Thread::SetCultureInfo

Event Sources (corhost.cpp) - #124303

• METHOD__EVENT_SOURCE__INITIALIZE_DEFAULT_EVENT_SOURCES in CorHost2::CreateAppDomain

Diagnostics (ds-rt-coreclr.h) - #124303

• METHOD__STARTUP_HOOK_PROVIDER__CALL_STARTUP_HOOK in ds_rt_apply_startup_hook

---

Priority 2: Cross-Platform, Exception Handling

Exception Construction (clrex.cpp) - #126061

• Exception constructor in EEException::CreateThrowable
• Exception constructor in EEMessageException::CreateThrowable
• Exception constructor in EEResourceException::CreateThrowable

Exception Construction (excep.cpp) - #124834

• METHOD__RUNTIME_WRAPPED_EXCEPTION__OBJ_CTOR in WrapThrowableInRuntimeWrappedException
• Various exception constructors in CreateTypeInitializationExceptionObject

Exception Utilities (excep.cpp) - #124834

• METHOD__OBJECT__TO_STRING in GetExceptionMessage
• METHOD__EXCEPTION__INTERNAL_PRESERVE_STACK_TRACE in RaiseTheExceptionInternalOnly
• METHOD__ENVIRONMENT__GET_RESOURCE_STRING_LOCAL in GetResourceStringFromManaged
• Event args constructor in ExceptionNotifications::DeliverExceptionNotification

Exception Info Retrieval (comutilnative.cpp) - #123986

• METHOD__EXCEPTION__GET_MESSAGE in ExceptionNative::GetMessageFromException
• METHOD__EXCEPTION__GET_CLASS_NAME in ExceptionNative::GetMessageFromException
• METHOD__EXCEPTION__GET_SOURCE in ExceptionNative::GetSource
• METHOD__EXCEPTION__GET_HELP_CONTEXT in ExceptionNative::GetHelpContext

---

Priority 3: Cross-Platform, Entry Points (Complex)

These are entry points or thread-related and require careful consideration.

Application Entry Points (assembly.cpp)

• Thread start / Main entry point in RunMainInternal - Convert MethodDescCallSite to UCO in entrypoints #126222
• METHOD__STARTUP_HOOK_PROVIDER__MANAGED_STARTUP in Assembly::ExecuteMainMethod - Convert priority 3 MethodDescCallSite calls to UnmanagedCallersOnly #124854

Process Lifecycle (appdomain.cpp) - #124854

• METHOD__APPCONTEXT__ON_UNHANDLED_EXCEPTION in AppDomain::RaiseUnhandledExceptionEvent
• METHOD__APPCONTEXT__ON_PROCESS_EXIT in AppDomain::RaiseExitProcessEvent

Invoke / Reflection (invokeutil.cpp) - #124854

• Constructor invocation in InvokeUtil::CreateObject
• Constructor invocation in InvokeUtil::CreateValueType

Host Callbacks (corhost.cpp) - #126222

• Method invocation in CorHost2::ExecuteAssembly

Exception handling

• ThrowHwEx` in HandleManagedFault and HandleHardwareException
• ThrowEx in DispatchManagedException
• Rethrow in DispatchRethrownManagedException

Runtime threads

• FinalizerThread::FinalizeAllObjects
• Thread.Start - KickOffThread_Worker

Reflection Invoke and similar

• MethodInfo.Invoke - RuntimeMethodHandle_InvokeMethod
• Custom attribute constructor in COMCustomAttribute::CreateCaObject
• FuncEvalWrapper() and DoNormalFuncEval()

---

Priority 4: Platform-Specific (ObjC - macOS/iOS)

ObjC Interop (interoplibinterface_objc.cpp) - #124446

• METHOD__OBJCMARSHAL__AVAILABLEUNHANDLEDEXCEPTIONPROPAGATION in ObjCMarshalNative::GetPropagatingExceptionCallback

---

Priority 5: Windows-Only (COM Interop)

These files are only compiled on Windows and are lowest priority.

COM Connection Points (comconnectionpoints.cpp) - #123864

• Delegate constructor in ConnectionPoint::Advise
• Provider method in ConnectionPoint::Advise

Standard Interfaces (stdinterfaces.cpp) - #123864

• CanRead property getter in IDispatchExInfo::GetIDsOfNames
• CanWrite property getter in IDispatchExInfo::GetIDsOfNames

CLR to COM Calls (clrtocomcall.cpp)

• METHOD__COM_OBJECT__GET_EVENT_PROVIDER in ComPlusMethodFrame::DoSlowPathComPlusCall - Convert some COM interop to UCO #125326
• METHOD__CLASS__FORWARD_CALL_TO_INVOKE in CLRToCOMLateBoundWorker - Convert some COM interop to UCO #125326
• Event implmentation dispatch in CLRToCOMEventCallWorker

COM Callable Wrapper (comcallablewrapper.cpp) - #123864

• Custom ICustomQueryInterface::GetInterface in ComCallWrapper::CallICustomQueryInterface

Custom Marshaler (custommarshalerinfo.cpp) - #125326

• METHOD__STUBHELPERS__GET_IENUMERATOR_TO_ENUM_VARIANT_MARSHALER in CustomMarshalerInfo::GetIEnumeratorToEnumVariantMarshaler

Runtime Callable Wrapper (runtimecallablewrapper.cpp)

• METHOD__LICENSE_INTEROP_PROXY__CREATE in LicenseInteropHelper::GetCurrentContextInfo - Revert "Partially revert PR #125326: revert ComActivator/LicenseInter… #126141
• METHOD__LICENSE_INTEROP_PROXY__GETCURRENTCONTEXTINFO in LicenseInteropHelper::GetCurrentContextInfo - Revert "Partially revert PR #125326: revert ComActivator/LicenseInter… #126141
• METHOD__LICENSE_INTEROP_PROXY__SAVEKEYINCURRENTCONTEXT in LicenseInteropHelper::SaveKeyInCurrentContext - Revert "Partially revert PR #125326: revert ComActivator/LicenseInter… #126141

OLE Variant (olevariant.cpp) - #125326

• METHOD__VARIANT__CAST_VARIANT in OleVariant::MarshalOleVariantForObject
• METHOD__VARIANT__CONVERT_VARIANT_TO_OBJECT in OleVariant::MarshalObjectForOleVariant
• METHOD__VARIANT__CONVERT_OBJECT_TO_VARIANT in OleVariant::MarshalOleVariantForObject

Dispatch Info (dispatchinfo.cpp) - ~30 call sites - #126074

Various reflection-based calls in:

• DispatchMemberInfo::GetParamInfo - parameter name retrieval
• DispatchMemberInfo::SetUpMethodMarshalerInfo - method handle retrieval
• DispatchMemberInfo::GetMemberInfoValue - property getters
• DispatchMemberInfo::SetMemberInfoValue - property setters
• DispatchExInfo::InvokeMember - member invocation
• DispatchExInfo::SynchWithManagedView - GetProperties, GetFields, GetMethods
• DispatchInfo::GetExceptionDescription - exception property getter

---

Follow up cleanup

• Delete CallDescrWorker

[dotnet-policy-service]

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

[AaronRobinsonMSFT]

/cc @jkotas @janvorli @davidwrighton

[AaronRobinsonMSFT]

@huoyaoyuan If you'd like to help on this one, feel free to grab any of the remaining issues in the Priority 1 bucket. All of them should be straight forward to address. I'd like to get through Priority 4 in .NET 11 as it would simplify some of the WASM work.

[huoyaoyuan]

Note: for the IDispatch related ones, I actually had an attempt to move larger code to managed and reduce the number of interop boundaries. If not emergent, I think we can explore on this later.

[jkoritzinsky]

@AaronRobinsonMSFT What about the places in the runtime that use the PREPARE_(NON)VIRTUAL_CALLSITE* with DECLARE_ARGHOLDER_ARRAY and CALL_MANAGED_METHOD_* macros? These also use MethodDescCallSite under the hood. I assume that we want to move these over to the UnmanagedCallersOnly pattern as well?