Convert priority 3 MethodDescCallSite calls to UnmanagedCallersOnly

[steveisok]

First set of priority 3 conversions from #123864 — replace MethodDescCallSite/CallDescrWorker calls with UnmanagedCallersOnly reverse P/Invoke calls.

Converted call sites

File	Call site	Method
appdomain.cpp	AppDomain::RaiseExitProcessEvent	ON_PROCESS_EXIT
appdomain.cpp	AppDomain::OnUnhandledException	ON_UNHANDLED_EXCEPTION
assembly.cpp	RunManagedStartup	MANAGED_STARTUP
assembly.cpp	RunMainInternal (TARGET_BROWSER)	HANDLE_ASYNC_ENTRYPOINT
invokeutil.cpp	InvokeUtil::CreateClassLoadExcept	ReflectionTypeLoadException ctor
invokeutil.cpp	InvokeUtil::CreateTargetExcept	TargetInvocationException ctor

Remaining priority 3 items (follow ups)

• Main entry point in RunMainInternal (dynamic MethodDesc)
• CustomAttribute_CreateCustomAttributeInstance (dynamic ctor, already a QCall)
• CorHost2::ExecuteAssembly (dynamic method lookup)
• FuncEvalWrapper/DoNormalFuncEval (debugger func-eval)

Pattern

Follows the same conversion pattern as #124834 (priority 2). Each conversion adds an [UnmanagedCallersOnly] managed wrapper with an Exception* out-parameter and replaces the native MethodDescCallSite + ARG_SLOT with
UnmanagedCallersOnlyCaller::InvokeThrowing.

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[Copilot]

Pull request overview

This PR converts priority 3 MethodDescCallSite/CallDescrWorker calls to more efficient UnmanagedCallersOnly reverse P/Invoke calls, following the established pattern from PR #124834. The conversions target application entry points and process lifecycle events in CoreCLR.

Changes:

• Adds [UnmanagedCallersOnly] wrappers in managed code with Exception* out-parameters for exception propagation
• Replaces native MethodDescCallSite calls with UnmanagedCallersOnlyCaller::InvokeThrowing template class
• Refactors ReflectionTypeLoadException creation from native to managed code via QCall pattern

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.Browser.cs	Adds UCO wrapper for HandleAsyncEntryPoint to handle async Main entry points on Browser target
src/coreclr/System.Private.CoreLib/src/System/StartupHookProvider.CoreCLR.cs	Adds UCO wrapper for ManagedStartup with exception handling
src/coreclr/System.Private.CoreLib/src/System/Exception.CoreCLR.cs	Adds UCO wrapper for CreateTargetInvocationException
src/coreclr/System.Private.CoreLib/src/System/AppContext.CoreCLR.cs	New file with UCO wrappers for OnProcessExit and OnUnhandledException
src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeModule.cs	Updates GetTypes QCall to return exceptions array for managed-side exception construction
src/coreclr/System.Private.CoreLib/System.Private.CoreLib.csproj	Adds new AppContext.CoreCLR.cs file to build
src/coreclr/vm/metasig.h	Adds new metasig definitions for UCO method signatures
src/coreclr/vm/corelib.h	Updates DEFINE_METHOD entries to reference new UCO signatures
src/coreclr/vm/appdomain.cpp	Replaces MethodDescCallSite with UnmanagedCallersOnlyCaller for process lifecycle events
src/coreclr/vm/assembly.cpp	Replaces MethodDescCallSite with UnmanagedCallersOnlyCaller for startup hooks and async entry points
src/coreclr/vm/invokeutil.h	Removes obsolete CreateClassLoadExcept declaration
src/coreclr/vm/invokeutil.cpp	Removes CreateClassLoadExcept implementation; converts CreateTargetExcept to use UCO pattern
src/coreclr/vm/commodule.h	Adds retExceptions parameter to RuntimeModule_GetTypes QCall signature
src/coreclr/vm/commodule.cpp	Returns exceptions array via out-parameter instead of throwing from native code
src/coreclr/vm/exceptionhandlingqcalls.h	Formatting fix - adds blank line at end of file

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/coreclr/vm/commodule.cpp:766

• RuntimeModule_GetTypes no longer throws inside the QCall when type loading fails, but the loop still doesn’t advance curPos on failure. With retExceptions.Set(...) replacing the throw, execution now continues and will hit _ASSERTE(curPos == dwNumTypeDefs) when any type load fails. Adjust the loop to keep curPos in sync with dwNumTypeDefs (e.g., advance and leave a null slot for failed loads, or remove/replace the assertion and ensure the returned Types array matches the intended semantics).

    // Return exceptions to managed side for throwing
    if (cXcept > 0) {

        gc.xceptRet = (PTRARRAYREF) AllocateObjectArray(cXcept,g_pExceptionClass);
        for (DWORD i=0;i<cXcept;i++) {
            gc.xceptRet->SetAt(i, gc.xcept->GetAt(i));
        }
        retExceptions.Set(gc.xceptRet);
    }

    // We should have filled the array exactly.
    _ASSERTE(curPos == dwNumTypeDefs);

[jkotas]

Test failure

ASSERT FAILED
	Expression: curPos == dwNumTypeDefs
	Location:   /__w/1/s/src/coreclr/vm/commodule.cpp:765
	Function:   RuntimeModule_GetTypes
	Process:    84956

[jkotas]

The wasm temporary callhelpers needs to be regenerated as part of these PRs: https://github.com/dotnet/runtime/blob/main/docs/workflow/wasm-documentation.md#running-coreclr-callhelpers-generator

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated no new comments.

[jkotas]

Thanks!

[Copilot]

Pull request overview

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

[Copilot]

The PR description's "Converted call sites" table claims that RunMainInternal (TARGET_BROWSER) / HANDLE_ASYNC_ENTRYPOINT in assembly.cpp has been converted, but the actual diff only converts RunManagedStartup. The RunMainInternal function still uses MethodDescCallSite. This appears to be an inaccuracy in the PR description, not the code — the actual "Remaining priority 3 items" section correctly notes that the main entry point in RunMainInternal is left as a follow-up.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

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[Copilot]

A managed [UnmanagedCallersOnly] UCO wrapper for OnUnhandledException with the signature (object* pObj, Exception* pException) is missing. The corelib.h declares ON_UNHANDLED_EXCEPTION with metasig SM_PtrObj_PtrException_RetVoid, and appdomain.cpp calls raiseEvent.InvokeThrowing(pThrowable) expecting that wrapper to exist, but no such UCO method has been added to either AppContext.CoreCLR.cs or AppContext.cs. The existing AppContext.OnUnhandledException(object e) is not marked [UnmanagedCallersOnly] and does not have the Exception* out-parameter. Without this method, METHOD__APPCONTEXT__ON_UNHANDLED_EXCEPTION binding will fail at runtime when the unhandled exception event fires.