What does HRESULT 0x8001012E (CO_E_CONVERSIONFAILED) mean?

CO_E_CONVERSIONFAILED

Trustee string conversion failed

CO_E_CONVERSIONFAILED is HRESULT 2147549486 (0x8001012E) from winerror.h. AllStat describes it as “Unable to convert a wide character trustee string to a multibyte trustee string.” In the COM IAccessControl, DCOM client identity, trustee translation, token inspection, security descriptor, ACL, or serialization workflow, the code identifies a specific failure boundary and should not be replaced by a generic COM exception.

The hexadecimal value and symbolic name CO_E_CONVERSIONFAILED should remain attached to the originating API and operation generation.

Decisive interpretation boundary

Before choosing recovery, verify that source encoding, code page, destination capacity, invalid-character policy, and account-name round trip are explicit. If this condition cannot be proven for CO_E_CONVERSIONFAILED, stop before consuming outputs or repeating side effects.

For CO_E_CONVERSIONFAILED, also confirm that all observed objects, tokens, buffers, proxies, metadata files, or ACLs belong to the current operation generation and were not retained from an earlier attempt.

Where it is encountered

• CO_E_CONVERSIONFAILED can be returned during IAccessControl initialization, access checks, owner/trustee processing, and serialized ACL persistence. For CO_E_CONVERSIONFAILED, record the interface, method, component version, thread, apartment, process, and correlation ID.
• CO_E_CONVERSIONFAILED can be returned during server-side DCOM impersonation, client blanket inspection, token and SID lookup. For CO_E_CONVERSIONFAILED, record the interface, method, component version, thread, apartment, process, and correlation ID.
• CO_E_CONVERSIONFAILED can be returned during security descriptor construction, DACL canonicalization, file-backed policy storage, or legacy NetAccess migration. For CO_E_CONVERSIONFAILED, record the interface, method, component version, thread, apartment, process, and correlation ID.

The immediate focus for CO_E_CONVERSIONFAILED is conversion of a wide trustee name to a multibyte representation required by a legacy access-control path. Keep CO_E_CONVERSIONFAILED attached to that operation; the same numeric severity outside the owning API does not supply enough context.

Diagnostic sequence

• Capture the raw unsigned value 0x8001012E and symbolic name CO_E_CONVERSIONFAILED before a language projection, exception wrapper, or generic COM helper replaces it.
• Identify the exact interface, method, callback, activation request, metadata query, access-control operation, or marshaling boundary that returned CO_E_CONVERSIONFAILED.
• Reconstruct the operation timeline for CO_E_CONVERSIONFAILED, including object creation, thread or apartment initialization, security setup, callbacks, mutations, shutdown, and cleanup.
• Prove the decisive condition: source encoding, code page, destination capacity, invalid-character policy, and account-name round trip are explicit.
• Inspect every output parameter, handle, interface pointer, token, SID, ACL, stream, buffer, server-side object, or asynchronous result produced before CO_E_CONVERSIONFAILED.
• Reproduce CO_E_CONVERSIONFAILED with the smallest safe input, change only the suspected precondition, and verify that both the HRESULT and postcondition change as predicted.

Evidence and telemetry

• Preserve source trustee and UTF-16 length for CO_E_CONVERSIONFAILED.
• Preserve target code page for CO_E_CONVERSIONFAILED.
• Preserve required and allocated byte counts for CO_E_CONVERSIONFAILED.
• Preserve lossy-character detection for CO_E_CONVERSIONFAILED.
• Preserve round-trip comparison for CO_E_CONVERSIONFAILED.

For CO_E_CONVERSIONFAILED, also record UTC time, process and thread IDs, apartment type, component version, security or package identity where relevant, and a correlation ID. For CO_E_CONVERSIONFAILED, use hashes, lengths, GUIDs, and SID strings rather than logging confidential payloads or credentials.

Correct handling and recovery

Keep Unicode end to end where possible; otherwise use strict conversion with required-size calculation and reject lossy identity transformations.

Backoff alone is not a repair for CO_E_CONVERSIONFAILED; a measurable state or configuration transition must justify another attempt.

Difference from nearby HRESULTs

CO_E_CONVERSIONFAILED is character conversion; trustee syntax and lookup HRESULTs describe later identity parsing or resolution.

A support tool discussing CO_E_CONVERSIONFAILED should name the neighboring result only after the originating API and decisive state are known.

Lifetime, retry, and cleanup rules

After CO_E_CONVERSIONFAILED, determine whether the current object, interface pointer, call context, token, stream, metadata reader, asynchronous operation, or access-control instance remains valid. For CO_E_CONVERSIONFAILED, release only resources owned by the failing attempt, cancel callbacks through their documented mechanism, and avoid double close, double commit, repeated activation, or replay of a non-idempotent remote method.

The retry policy for CO_E_CONVERSIONFAILED should state the trigger, maximum attempts, cancellation owner, and reconciliation step for effects that may have completed elsewhere.

Developer and administrator guidance

When CO_E_CONVERSIONFAILED crosses native, managed, scripting, RPC, or WinRT projection boundaries, preserve the unsigned 32-bit HRESULT. Unit tests for CO_E_CONVERSIONFAILED should assert the code-specific postcondition and resource ownership, not merely that an exception was thrown.

After CO_E_CONVERSIONFAILED, avoid broad permission grants or system-wide resets unless code-specific evidence proves a global configuration problem. Define who owns retry, cancellation, cleanup, policy changes, package repair, and user-facing messaging for CO_E_CONVERSIONFAILED.

Practical scenario

A trustee contains characters absent from the configured ANSI code page. The component switches its persistence format to Unicode instead of substituting question marks.

A regression test should reproduce CO_E_CONVERSIONFAILED, assert the raw HRESULT and all relevant outputs, then correct only the decisive condition and verify the intended success or neighboring failure result.

References

• Microsoft: IAccessControl — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: IAccessControl::IsAccessAllowed — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: AccessCheck — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: LookupAccountSidW — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: LookupAccountNameW — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: access control lists — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: canonical ACE order — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.
• Microsoft: HRESULT values — official Microsoft documentation relevant to CO_E_CONVERSIONFAILED.

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