Invoke debugger function evaluations through managed UCO by jkoritzinsky · Pull Request #133659 · dotnet/runtime

jkoritzinsky · 2026-09-11T03:04:36Z

Summary

Layer 3 of the stack for #123864, following #133658. The prior func-eval-specific proposal is #126809.

This layer started as replacing the final native managed-call dispatch with a managed UnmanagedCallersOnly entrypoint. It now moves most debugger function-evaluation preparation, invocation, storage, and copy-back into managed CoreLib while retaining the debugger-specific control flow and GC-safe bootstrap in native code.

Managed invocation and storage

Add Debugger.FunctionEvaluation, a runtime-owned UCO entrypoint that resolves the exact target method from its declaring RuntimeType and rooted IRuntimeMethodInfo.
Extend the shared reflection invocation emitter with debugger-specific thunks that prepare arguments, invoke methods and constructors, copy back writable arguments, and publish results.
Emit newobj for debugger object construction instead of preallocating an object and calling its constructor as an ordinary method. Existing-object constructor calls remain supported, and abstract/interface allocation is rejected.
Keep the entire managed call-address vector registered through GCFrameRegistration, using exact typed locals for memory-backed by-value ref structs so their managed byrefs are reported by normal JIT GC info.
Handle object, primitive, enum, pointer, value-type, nullable, literal, memory, register, and byref argument representations in managed code while preserving native-endian storage and debugger copy-back semantics.
Align nullable behavior with the existing debugger contract: direct value-type memory homes are mutated in place, while debugger handles are not treated as writable nullable homes. Exact register-backed nullable temporaries are boxed only after their MethodTable is instance-active.
Move ordinary value-type result storage into temporary GC-described external memory and defer boxing until after invocation and argument copy-back. Keep byref-like results in persistent external storage and raw byref results rooted directly in the debugger result slot.
Create result handles in managed code only after the result is fully prepared, and preserve object identity and updated field contents across collections and later debugger inspection.

Native debugger and GC integration

Retain native method/signature validation, generic resolution, class initialization, receiver validation inputs, register/home capture, abort state, exception publication, completion, and result ownership.
Capture contiguous register value-type snapshots before the first GC-triggering managed transition and describe them with their exact type layout.
Root non-leaf register references and register value-type snapshots with ExternalMemoryHandle registrations so collections during managed preparation relocate their contents correctly.
Represent external memory with a full tagged TypeHandle, allowing the runtime and cDAC to distinguish inline value types, object-reference slots, managed-byref slots, and unmanaged pointer/function-pointer locals.
Report each external-memory type's loader allocator during GC scanning, keeping collectible layouts alive while external storage is registered.
Add dedicated GC-safe object-register copy-back and native-endian scalar register copy-back paths.
Remove stale native argument copies and architecture-specific packing layers that are no longer needed, while preserving the architecture-specific register-home logic required by debugger IPC.
Treat the debugger UCO entrypoint as a runtime-internal reverse transition for exception handling, and exclude its debugger-only MethodDesc state on WebAssembly targets that do not build debug/ee.
Update the cDAC ExternalMemoryHandles reader, descriptors, tests, and authoritative contract documentation for the exact managed-local representation.

Correctness fixes included

Avoid double relocation of overlapping byrefs in by-value ref structs (Debugger func-eval: a by-value ref struct with overlapping ref fields is reported to the GC twice, so a compacting GC relocates the byref twice #135245).
Keep raw byref results rooted until deferred debugger completion (Debugger func-eval byref result can become stale before deferred completion #135247).
Prevent stale non-leaf register values after a compacting GC (Debugger func-eval can use stale non-leaf register values after GC #135249).
Preserve current external-result fields across collections and later inspection (Debugger external-memory func-eval results can expose stale cached fields after GC #135251).
Keep collectible loader allocators alive while external-memory layouts are scanned (Func-eval ref struct result: ExternalMemoryHandle doesn't keep a collectible LoaderAllocator alive (access violation in GC after unload) #135252).

Validation

Validation used the existing internal MDbg/xUnit debugger-test harness with a private CoreRun and ProjectK/CoreCLR-only configuration:

Targeted nested-byref invariant under target-only GCStress=0x3: 1/1 passed.
Revised normal matrix: 35/35 passed.
Targeted stress matrix: 4/4 passed.
Windows x64 and x86 Checked native, CoreLib, and ReadyToRun builds completed with zero warnings and errors.
cDAC unit tests and generated usage/documentation checks passed for the ExternalMemoryHandle descriptor changes.

Coverage includes moving GC, overlapping and nested byrefs, memory and register homes, non-leaf registers, receiver mutation, constructors, primitive/native-endian copy-back, nullable memory homes, byref/byref-like/value-type results, collectible generics and layouts, nested and exception-time eval, safe/rude/exception-unwind aborts, and post-eval inspection. Runtime hashes and loaded modules were audited; each abort scenario completed the callback, successfully evaluated Echo(42), detached, and exited MDbg with code 100. Test configurations were restored and no debugger/test processes survived the runs.

These results were recorded on the validated pre-refresh candidate. The final stack rebase preserved the layer's net diff; builds and tests were not repeated after the history rewrite at the user's request.

The final native invocation cleanup layer is #133660.

_{Stack created with GitHub Stacks CLI • Give Feedback 💬}

Resolves #135245
Resolves #135247
Resolves #135249
Resolves #135251
Resolves #135252

Note

This PR description and implementation were prepared with GitHub Copilot. Commits that reuse am11's code retain the requested co-author attribution.

azure-pipelines · 2026-09-11T03:05:19Z

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dotnet-policy-service · 2026-09-11T03:26:38Z

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am11 · 2026-09-11T06:02:49Z

discussed on #126542.

nit: funceval was already split: #126809 so #126542 discussion is irrelevant.

jkoritzinsky · 2026-09-15T00:31:39Z

Thanks, @am11. Corrected the summary to reference #126809 for the prior func-eval-specific proposal rather than #126542.

Note

This reply was prepared with GitHub Copilot.

## Summary Layer 1 of the stack for #123864, building on am11's #126542 and the requested split in #126542 (comment). The dependent layers are #133658 (custom attributes), #133659 (func-eval), and #133660 (dead native machinery cleanup). - Use shared, precompilable managed thunks for common `MethodInfo.Invoke`, `ConstructorInfo.Invoke`, `MethodInvoker`, and `ConstructorInvoker` shapes instead of the native reflection dispatcher. - Cover bounded reference/primitive families: ordinary reference-type instance/delegate calls, reference constructors through eight arguments, selected primitive/enum-bearing constructors and methods, and targeted static/reference-byref patterns. Comments identify the ASP.NET Core callsites motivating the specialized shapes. - Resolve virtual/interface targets for the actual receiver, and preserve declared-type argument validation, enum widths/result identity, reference copy-back, and collectible ownership. - Keep unsupported signatures on the cached emitted fallback; this does not add general struct/nullable/value-type-receiver support. - Stay shared for the first **10,000 calls**, then specialize starting on **call 10,001**. Promotion and every specialization strategy require `RuntimeFeature.IsDynamicCodeCompiled`, not merely `IsDynamicCodeSupported`. - Preserve existing-object constructor invocation and make ReadyToRun's explicit-this calli rewrite agree with the VM intrinsic. No public API is added. ## Validation The threshold update passed **1,964 reflection + 631 forced-emitted + 631 forced-shared** cases on Windows x64 Checked CoreCLR. Exact boundary tests cover the object, span, and byref strategies; the old 100-call runtime fails those tests as expected. A controlled CoreLib configuration with **dynamic code supported but not compiled** passed another **631 + 631** forced-mode cases and retained shared invocation beyond 10,000 calls. That configuration is policy coverage, not a claim of executing a native compiler-less platform. The bounded matrix includes virtual/interface/generic-virtual/default-interface dispatch, delegate `DynamicInvoke` with static and multicast callbacks, enum widths/results, reference out-parameter success/false/exception behavior, moving GC, unsupported-shape boundaries, and collectible methods. Later stack validation also executed the invocation suites on Windows x86. Browser/WASI managed CoreLib/ABI generation was checked; actual browser/WASI and big-endian runtime execution was not performed. ## Performance evidence Local measurements used a Windows x64 EPYC 7763 Hyper-V VM. The ASP.NET Core survey at `dotnet/aspnetcore` revision `a2ac63c3a56d` establishes source-level invocation demand, **not measured performance rankings**. Adding the bounded families avoided approximately **1.5–5 KiB of managed allocation per first invocation** versus the earlier stack's emitted fallback. An actual ASP.NET Core 10.0.9 `UseMiddleware`/`ActivatorUtilities` eight-reference-constructor startup probe measured median **16.8753 → 14.4399 ms** and **9,560 → 5,376 bytes** across seven paired fresh-process runs. This did not measure ordinary compiled request dispatch or default-constructor `Activator` paths. For the separate **100 → 10,000 threshold** comparison, matching Release native hosts and baseline/changed CoreLib were run with ReadyToRun disabled for both. Seventy-two fresh-process observations confirmed the actual boundary. Selected warmed BenchmarkDotNet results were: | Shape | Threshold 100 | Threshold 10,000 | Managed allocation | |---|---:|---:|---:| | Eight-reference constructor | 252.30 ns | 228.15 ns | 24 B in both | | Instance primitive getter | 26.57 ns | 25.25 ns | 24 B in both | | Static four-reference method | 115.95 ns | 94.97 ns | 0 B in both | These are short VM-local measurements, not universal throughput guarantees. Earlier expanded-shape testing at threshold 100 exposed a profile-sensitive warmed `ConstructorInfo.Invoke` eight-argument case at approximately 1.30× baseline; tiering-disabled/direct-loop controls and the actual `ConstructorInvoker` middleware API did not reproduce that effect. The threshold comparison above is a separate experiment. --- <sub>Stack created with <a href="https://github.com/github/gh-stack">GitHub Stacks CLI</a> • <a href="https://gh.io/stacks-feedback">Give Feedback 💬</a></sub> > [!NOTE] > This PR description and implementation were prepared with GitHub Copilot. Commits that reuse am11's code retain the requested co-author attribution. --------- Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

jkotas · 2026-10-05T22:20:07Z

+}
+

 /*


#126809 eliminated a lot of the layers that copy arguments around in this file. Is it possible to do it here? Or are there some fundamental problems with it?

I'm working on eliminating some of the copies and moving things to managed (and fixing a bunch of func-eval bugs I've found in the process). That's why this PR is still draft. Should be pushing it up soon I hope.

jkoritzinsky · 2026-10-05T22:37:36Z

+            if (addr == static_cast<CORDB_ADDRESS>(0))
+            {
+                VMPTR_TypeHandle layoutHandle = cv->m_type->m_typeHandleExact;
+                if (layoutHandle.IsNull())
+                {
+                    EX_TRY
+                    {
+                        TypeInfoList types(bufferFrom, static_cast<int>(fullArgTypeNodeCount));
+                        RSLockHolder lockHolder(GetProcess()->GetProcessLock());
+                        hr = GetProcess()->GetDAC()->GetApproxTypeHandle(&types, &layoutHandle);
+                    }
+                    EX_CATCH_HRESULT(hr);
+                    IfFailRet(hr);
+                }
+                bufferFrom[0].data.ClassTypeData.typeHandle = layoutHandle;
+            }
+


This block fixes #135249

jkoritzinsky · 2026-10-05T22:38:14Z

This updates in this file fix #135251

Complete the third layer of #123864 on the shared invocation foundation from #126542. Use rooted receiver/argument/result storage and the common managed emitter instead of native ABI packing. Preserve raw byref and nullable results, in-place receivers, register/literal semantics, exception propagation and abort recovery. Correct native-helper abort contracts and true nullable backing-box copy-back. Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

WebAssembly does not build or link debug/ee even though DEBUGGING_SUPPORTED is defined. Guard both the debugger UCO MethodDesc declaration and its EH comparison with TARGET_WASM instead of referencing an unavailable definition. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Add an internal InvokeForDebugger facade on RuntimeConstructorInfo that forwards to its existing MethodBaseInvoker, so Debugger.InvokeFunction no longer needs direct access to the constructor's Invoker property once it is made private for encapsulation. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

The writable copy is performed by PackArgumentStorage. The residual copy in GetFuncEvalArgStorage references parameters removed by the managed func-eval refactor. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Use debugger-specific emitted thunks for managed argument preparation, invocation, and copy-back. Retain native GC-safe input capture and debugger state handling, protect result and snapshot storage with external memory handles, and preserve reference identity and fresh external-value inspection across collections. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Register known references in serialized non-leaf register slots with external memory handles before managed entry. Read register-only value types from those GC-updated slots, while preserving native snapshots for leaf and mixed homes and leaving numeric register contents unchanged. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Run preparation, invocation, and copy-back within a single managed UCO entry. Use GCFrameRegistration for call storage, and move primitive capture, result handle creation, and memory/literal copy-back into CoreLib while retaining native bootstrap, register, and completion responsibilities. Avoid the invalid cooperative-mode safe-point query uncovered by GCStress validation. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Replace the debugger-specific allocator QCall with RuntimeTypeHandle.InternalAllocNoChecks after activating each type at its actual allocation site. Preserve COM, GCStress, logging, large/finalizable object, and profiler/ETW behavior by falling back to the existing slow allocator when required. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Treat RAK_MEMREG and RAK_REGMEM as scalar 64-bit integer or enum homes rather than hypothetical GC-containing structs. Remove their GC-layout rooting and address registrations, retain scalar snapshots and copy-back, reduce the external-handle bound, and assert the verified invariant. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Register DebuggerEval::m_result[0] directly as the persistent interior root for raw byref returns. Tie root ownership to DebuggerEval cleanup, remove the refresh/controller ownership path, and unregister before exception publication repurposes the slot. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Report the MethodTable loader allocator during external-memory root promotion and remove the redundant debugger typed-owner allocator handle. Preserve the separate raw-byref result lifetime root. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Represent external memory with the exact managed local type, including byrefs and unmanaged pointers. Update runtime callers, cDAC descriptors, root walking, tests, and contract documentation. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

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

Co-authored-by: am11 <3840695+am11@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

This reverts commit cc83a28cb5e01c0c58ff4b73bef5423681110560. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

jkoritzinsky added this pull request to stack #133661 September 11, 2026 03:04

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Remove obsolete native managed-invocation machinery #133660

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Move custom attribute materialization and invocation to managed code #133658

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Use shared managed thunks for reflection invocation #133662

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Integrate value-class GC protection into GCFrame across CoreCLR and NativeAOT #133730

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Runtime_133587 SIGSEGV in mono #133910

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This updates in this file fix #135251

jkoritzinsky mentioned this pull request Oct 6, 2026

Debugger constructor function evaluation lacks an abstract-class allocation check #135301

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jkoritzinsky marked this pull request as ready for review October 7, 2026 22:40

jkoritzinsky and others added 15 commits October 7, 2026 15:45

Fix managed debugger function evaluation storage

dbb5fdd

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

Version the external memory handles contract

1085af5

Co-authored-by: am11 <3840695+am11@users.noreply.github.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Revert "Version the external memory handles contract"

8e7b0b6

This reverts commit cc83a28cb5e01c0c58ff4b73bef5423681110560. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

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Invoke debugger function evaluations through managed UCO - #133659

Invoke debugger function evaluations through managed UCO#133659
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Summary

Managed invocation and storage

Native debugger and GC integration

Correctness fixes included

Validation

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