What does HRESULT 0x800401EF (MK_E_ENUMERATION_FAILED) mean?

Status / error code:

Category:

Constant name:

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Facility:

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Description:

The moniker could not enumerate the components required by the operation.

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MK_E_NOPREFIX	CO_E_NOTINITIALIZED

MK_E_ENUMERATION_FAILED

Moniker could not be enumerated

The native value 0x800401EF is MK_E_ENUMERATION_FAILED, unsigned 2147746287 and signed -2147221009. According to AllStat, it means “Moniker could not be enumerated”. Treat it as evidence that the moniker could not enumerate the components required by the operation; the operation in progress is walking a composite moniker or exposing its constituent monikers.

The high bit in 0x800401EF is set, so this is a failure rather than a success or informational result. Its facility field is 4 (FACILITY_ITF) and its low 16-bit code is 495 (0x01EF). Those bit fields classify the value, but they do not identify the failing object by themselves; the native method, object identity, and first producer of MK_E_ENUMERATION_FAILED remain essential.

Operational meaning

Understanding MK_E_ENUMERATION_FAILED requires this subsystem context: A moniker is an object with class-specific parsing, comparison, composition, and binding behavior. For MK_E_ENUMERATION_FAILED, display-name text alone does not establish what operations a particular moniker implementation supports.

Associate MK_E_ENUMERATION_FAILED with one exact operation in IMoniker methods, IBindCtx state, display-name parsing, composite monikers, the Running Object Table, deadlines, and object or storage binding.
Confirm that MK_E_ENUMERATION_FAILED came from walking a composite moniker or exposing its constituent monikers, rather than from cleanup or a wrapper that ran afterward.
Preserve any IErrorInfo, underlying Win32 result, provider message, or callback failure that preceded MK_E_ENUMERATION_FAILED; the HRESULT alone should not erase a more specific cause.

Cause model

MK_E_ENUMERATION_FAILED can result when the component enumerator fails partway through a malformed composite.
MK_E_ENUMERATION_FAILED can result when a component object is released or disconnected during enumeration.
MK_E_ENUMERATION_FAILED can result when the implementation returns inconsistent Next/Clone/Reset behavior.

Troubleshooting workflow

Capture MK_E_ENUMERATION_FAILED at the first native return before a wrapper maps it to a generic exception.
Identify the exact object, method, and lifecycle phase involved in walking a composite moniker or exposing its constituent monikers.
Record the component index and last successfully enumerated moniker.
Retain the exact enumerator HRESULT and object identities.
Test Clone, Reset, and single-step Next behavior under stable lifetime.
Reproduce MK_E_ENUMERATION_FAILED with one controlled input or state change, and verify that the correction changes the decisive evidence rather than merely hiding the result.

What to log

A useful MK_E_ENUMERATION_FAILED incident records the moniker class, display name with secrets removed, bind options and deadline, pmkToLeft, requested IID, ROT result, file identity, composite components, and object lifetime registrations in IBindCtx. For MK_E_ENUMERATION_FAILED, also retain the application and component build, architecture, process and thread IDs, COM apartment, operation correlation ID, elapsed time, and the first state-changing event before the failure. When logging MK_E_ENUMERATION_FAILED, redact content and credentials while preserving types, lengths, hashes, opaque identities, and lifecycle generations needed to reproduce its contract.

For MK_E_ENUMERATION_FAILED, record the component index and last successfully enumerated moniker.
For MK_E_ENUMERATION_FAILED, retain the exact enumerator HRESULT and object identities.
For MK_E_ENUMERATION_FAILED, test Clone, Reset, and single-step Next behavior under stable lifetime.

Correction strategy

Correction. For MK_E_ENUMERATION_FAILED, rebuild the composite from validated components or fix the moniker implementation and restart enumeration from a fresh object. Retry boundary. Retry after replacing the enumerator or stabilizing lifetime; continuing after an unknown skipped component is unsafe. Before repeating the MK_E_ENUMERATION_FAILED operation, release partial monikers and bound interfaces, unregister only owned Running Object Table entries, and abandon a bind context whose deadline or parameters no longer match the retry.

Practical scenario

A custom composite stores a released child pointer, so enumeration fails after two valid components; reconstructing it from serialized identities fixes the object. This isolates MK_E_ENUMERATION_FAILED within COM moniker parsing, composition, binding, and storage resolution and provides a regression test for the stated correction.

Difference from related HRESULTs

MK_E_INTERMEDIATEINTERFACENOTSUPPORTED fails while using a component; MK_E_ENUMERATION_FAILED fails while obtaining the component sequence. For MK_E_ENUMERATION_FAILED, keep those outcomes separate in exception mappings, telemetry dimensions, user messages, and automated retry policy.

Developer and administrator guidance

For MK_E_ENUMERATION_FAILED, preserve the concrete moniker class, compose through IMoniker methods rather than string concatenation, set realistic bind deadlines, and request object versus storage interfaces deliberately. Regression coverage for MK_E_ENUMERATION_FAILED should include malformed and class-specific display names, absent left-hand context, expired deadlines, unsupported inverse or enumeration operations, unavailable ROT objects, file access, and storage-only targets.

Operational repair for MK_E_ENUMERATION_FAILED must target the evidence-backed owner: verify the named resource, file, server, or registration identified by the concrete moniker; do not infer a machine-wide COM fault from one provider-specific display name. Retain before-and-after traces for MK_E_ENUMERATION_FAILED so the change can be attributed and reversed.

References

Microsoft: generic COM error codes — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.
Microsoft: HRESULT values — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.
Microsoft: IMoniker — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.
Microsoft: IBindCtx — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.
Microsoft: MkParseDisplayName — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.
Microsoft: IEnumMoniker — official Microsoft documentation relevant to MK_E_ENUMERATION_FAILED.

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