[cDAC] Implement DacDbi APIs EnumerateClassFields and EnumerateInstantiationFields by Copilot · Pull Request #128829 · dotnet/runtime

Copilot · 2026-06-01T02:15:06Z

Add EditAndContinue cDAC contract with API

IEnumerable<TargetPointer> EnumerateAddedFieldDescs(TypeHandle typeHandle, bool staticFields);

Adding the following RuntimeTypeSystem APIs:

    uint GetNumInstanceFieldBytes(TypeHandle typeHandle);
    bool IsFieldDescRVA(TargetPointer fieldDescPointer);
    bool IsFieldDescEnCNew(TargetPointer fieldDescPointer);

…h/alloc, full DEBUG validation) Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

dotnet-policy-service · 2026-06-01T02:16:55Z

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Copilot

Pull request overview

The PR description frames this as a small follow-up cleanup ("refactor two file-local FieldDataAccumulator helpers to use the existing generic CallbackAccumulator<FieldData> and revert an unnecessary DAC/DBI protocol counter bump"), but the actual diff is a much larger change that also lands the DacDbi FieldData callback-based protocol, the new cDAC IEditAndContinue contract, and supporting data descriptors.

Changes:

Replace IDacDbiInterface::GetClassInfo / GetInstantiationFieldInfo with callback-based EnumerateClassFields / EnumerateInstantiationFields (managed + native) and refactor rsclass.cpp / rstype.cpp to drive them via CallbackAccumulator<FieldData>; widen FieldData::m_fldInstanceOffset to ULONG64 and m_pFldStaticAddress to CORDB_ADDRESS.
Add a new cDAC IEditAndContinue contract (EnumerateAddedFieldDescs), new EnCEEClassData / EnCAddedFieldElement / UnorderedArrayBase Data classes + descriptors, Module.EnCClassList (optional FieldAddress), and supporting source-generator changes for nullable FieldAddress.
Expose GetNumInstanceFieldBytes / IsFieldDescRVA / IsFieldDescEnCNew on IRuntimeTypeSystem, add EEClass.BaseSizePadding, extract CUnorderedArrayBase so cDAC can read it, and add mocks + xUnit tests for the new EnC contract.

Show a summary per file

File	Description
src/coreclr/inc/dacdbi.idl	Replace `GetClassInfo`/`GetInstantiationFieldInfo` with `Enumerate*` callback-based variants; drop `DacDbiArrayList_FieldData`/`ClassInfo` decls.
src/coreclr/debug/inc/dacdbiinterface.h	New `FP_FIELDDATA_CALLBACK` typedef and `EnumerateClassFields` / `EnumerateInstantiationFields` virtuals; updated docs.
src/coreclr/debug/inc/dacdbistructures.h	Widen `m_fldInstanceOffset` to `ULONG64` and `m_pFldStaticAddress` to `CORDB_ADDRESS`; update setter signatures.
src/coreclr/debug/inc/dacdbistructures.inl	Adjust `FieldData` inline accessors to match new `CORDB_ADDRESS`/`ULONG64` types.
src/coreclr/debug/daccess/dacdbiimpl.h	Replace `GetClassInfo`/`GetInstantiationFieldInfo` decls; change `CollectFields` to callback form; drop `GetTotalFieldCount`/`InitClassData`.
src/coreclr/debug/daccess/dacdbiimpl.cpp	Implement callback-based `Enumerate*`; update `ComputeFieldData` to use `CORDB_ADDRESS`; remove preallocation/count logic.
src/coreclr/debug/di/rsclass.cpp	Drive `EnumerateClassFields` via `CallbackAccumulator<FieldData>` and `Init` the field list from `acc.items`.
src/coreclr/debug/di/rstype.cpp	Same refactor for `EnumerateInstantiationFields`.
src/coreclr/inc/utilcode.h	Extract `CUnorderedArrayBase` (count + `TADDR` table) from `CUnorderedArrayWithAllocator` and add `cdac_data` shim.
src/coreclr/vm/encee.h	Add `cdac_data` for `EnCEEClassData` and `EnCAddedFieldElement`.
src/coreclr/vm/ceeload.h	Add `cdac_data<Module>::EnCClassList` under `FEATURE_METADATA_UPDATER`.
src/coreclr/vm/class.h	Add `cdac_data<EEClass>::BaseSizePadding`.
src/coreclr/vm/datadescriptor/datadescriptor.inc	Add `UnorderedArrayBase`, `EnCEEClassData`, `EnCAddedFieldElement` descriptors; `EEClass.BaseSizePadding`; `FieldOffsetNewEnc` global; `EditAndContinue` contract entry.
.../Abstractions/Contracts/IEditAndContinue.cs	New contract interface (`EnumerateAddedFieldDescs`) and empty struct.
.../Abstractions/Contracts/IRuntimeTypeSystem.cs	Add `GetNumInstanceFieldBytes`, `IsFieldDescRVA`, `IsFieldDescEnCNew`; make `fieldDef` nullable on `GetFieldDescOffset`.
.../Abstractions/ContractRegistry.cs	Expose `EditAndContinue` accessor.
.../Contracts/CoreCLRContracts.cs	Register `EditAndContinue` v1.
.../Contracts/Contracts/EditAndContinue_1.cs	New v1 implementation enumerating EnC-added FieldDescs.
.../Contracts/Contracts/RuntimeTypeSystem_1.cs	Implement `GetNumInstanceFieldBytes`/`IsFieldDescEnCNew`; promote `IsFieldDescRVA` to interface; null-handle big-RVA `fieldDef`.
.../Contracts/Data/{Module,EEClass,EnCEEClassData,EnCAddedFieldElement,UnorderedArrayBase}.cs	New Data classes / fields backing the EnC descriptors.
.../Contracts/DataType.cs / Constants.cs	New `DataType` values and `FieldOffsetNewEnc` global.
.../DataGenerator/Parser.cs, Emitter.cs	Source-gen support for optional/nullable `[FieldAddress]` properties.
.../Legacy/Dbi/{IDacDbiInterface.cs,DacDbiImpl.cs}	Define `FieldData` struct; implement new managed `Enumerate*` with optional debug-only legacy validation.
src/native/managed/cdac/tests/...	New mock infrastructure (`MockDescriptors.EditAndContinue.cs`), EnC contract xUnit tests, and `TestOptionalFieldAddr` data-generator tests.
docs/design/datacontracts/{EditAndContinue,RuntimeTypeSystem}.md	Document the new contract and the new `IRuntimeTypeSystem` APIs/globals.

Copilot's findings

Files reviewed: 36/36 changed files
Comments generated: 1

Copilot

Copilot's findings

Files reviewed: 39/39 changed files
Comments generated: 5

            // this may be called multiple times. Each call will discard previous values in m_fieldList and reinitialize
            // the list with updated information
            RSLockHolder lockHolder(pProcess->GetProcessLock());
-            IfFailThrow(pProcess->GetDAC()->GetInstantiationFieldInfo(m_pClass->GetModule()->GetRuntimeAssembly(),
+
+            CallbackAccumulator<FieldData> acc;


+            // Mirrors native: storage not yet available; carry the FieldDesc pointer through
+            // m_vmFieldDesc but leave all "is" flags false.


+            bool isNullable = prop.Type is INamedTypeSymbol named
+                && named.IsGenericType
+                && named.ConstructedFrom.ToDisplayString() == "System.Nullable<T>";


+    if (DWord2 == _target.ReadGlobal<uint>("FieldOffsetBigRVA") && fieldDef.HasValue)
    {
-        return (uint)fieldDef.GetRelativeVirtualAddress();
+        return (uint)fieldDef.Value.GetRelativeVirtualAddress();
    }


noahfalk

Looked good other than a few comments inline.

noahfalk · 2026-06-02T00:23:22Z

@@ -0,0 +1,64 @@
+# Contract EditAndContinue


Suggested change

# Contract EditAndContinue

# Contract RuntimeMutableTypeSystem

Naming nit: I believe we have scenarios other than ENC (such as HotReload) that can modify types on the fly too.

noahfalk · 2026-06-02T00:26:25Z

@@ -0,0 +1,64 @@
+# Contract EditAndContinue
+
+This contract exposes the runtime's Edit-and-Continue (EnC) bookkeeping.


Suggested change

This contract exposes the runtime's Edit-and-Continue (EnC) bookkeeping.

This contract exposes runtime type system information about changes that occured after the initial type load, such as from ENC or HotReload.

noahfalk · 2026-06-02T00:34:50Z

 bool IsFieldDescThreadStatic(TargetPointer fieldDescPointer);
 bool IsFieldDescStatic(TargetPointer fieldDescPointer);
+bool IsFieldDescRVA(TargetPointer fieldDescPointer);
+bool IsFieldDescEnCNew(TargetPointer fieldDescPointer);


Could we put this in the ENC contract? A runtime that doesn't implement the ENC contract shouldn't have discoverable ENC FieldDescs.

noahfalk · 2026-06-02T00:49:15Z


 ### FieldDesc

+The version 1 FieldDesc APIs depend on the following globals:


The comment implies we have a separately versioning FieldDesc contract but I don't believe we do right? Unless we plan to define a separate contract this sounds like it should get merged with other RuntimeTypeSystem references.

noahfalk · 2026-06-02T12:13:24Z

        // Free the chunk of memory.
-        if (m_pTable != NULL)
-            ALLOCATOR::Free(this, m_pTable);
+        if (m_pTable != (TADDR)NULL)


Rather than modify all these members is anything stopping us from leaving m_pTable conditionally typed as T*/TADDR?

Implement cDAC EnumerateClassFields/EnumerateInstantiationFields (pus…

f16be04

…h/alloc, full DEBUG validation) Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

Copilot AI self-assigned this Jun 1, 2026

Copilot AI review requested due to automatic review settings June 1, 2026 02:15

Copilot AI assigned rcj1 Jun 1, 2026

Copilot AI review requested due to automatic review settings June 1, 2026 02:15

Copilot created this pull request from a session on behalf of rcj1 June 1, 2026 02:15 View session

github-actions Bot added the area-Diagnostics-coreclr label Jun 1, 2026

idl

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Copilot AI review requested due to automatic review settings June 1, 2026 02:18

Copilot started reviewing on behalf of rcj1 June 1, 2026 02:18 View session

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Comment thread src/coreclr/debug/inc/dacdbistructures.h

Copilot started work on behalf of rcj1 June 1, 2026 02:50 View session

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Copilot AI requested a review from rcj1 June 1, 2026 02:54

fix build

9b06253

fix build

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Copilot AI review requested due to automatic review settings June 1, 2026 18:23

Copilot started reviewing on behalf of rcj1 June 1, 2026 18:24 View session

rcj1 changed the title ~~Refactor FieldData accumulators in DI to CallbackAccumulator<FieldData>~~ [cDAC] Implement DacDbi APIs EnumerateClassFields and EnumerateInstantiationFields Jun 1, 2026

rcj1 marked this pull request as ready for review June 1, 2026 18:29

rcj1 requested review from barosiak, max-charlamb and noahfalk June 1, 2026 18:30

Copilot AI reviewed Jun 1, 2026

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noahfalk approved these changes Jun 2, 2026

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[cDAC] Implement DacDbi APIs EnumerateClassFields and EnumerateInstantiationFields#128829

[cDAC] Implement DacDbi APIs EnumerateClassFields and EnumerateInstantiationFields#128829
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Copilot AI commented Jun 1, 2026 •

edited by rcj1

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		// Mirrors native: storage not yet available; carry the FieldDesc pointer through
		// m_vmFieldDesc but leave all "is" flags false.

	# Contract EditAndContinue
	# Contract RuntimeMutableTypeSystem

		@@ -0,0 +1,64 @@
		# Contract EditAndContinue

		This contract exposes the runtime's Edit-and-Continue (EnC) bookkeeping.

	This contract exposes the runtime's Edit-and-Continue (EnC) bookkeeping.
	This contract exposes runtime type system information about changes that occured after the initial type load, such as from ENC or HotReload.


		### FieldDesc

		The version 1 FieldDesc APIs depend on the following globals:

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Copilot AI commented Jun 1, 2026 •

edited by rcj1

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