What does HRESULT 0x80010135 (CO_E_PATHTOOLONG) mean?

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CO_E_PATHTOOLONG

COM access-control serialization path is too long

CO_E_PATHTOOLONG is HRESULT 2147549493 (0x80010135) from winerror.h. AllStat describes it as “Path too long.” 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.

Telemetry should preserve CO_E_PATHTOOLONG as a separate outcome rather than merging it with unrelated COM or WinRT failures.

Where it is encountered

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

The immediate focus for CO_E_PATHTOOLONG is a path generated for ACL serialization, temporary files, or COM support data that exceeds the consuming API or format limit. Keep CO_E_PATHTOOLONG attached to that operation; the same numeric severity outside the owning API does not supply enough context.

Decisive interpretation boundary

Before choosing recovery, verify that the full normalized path, component lengths, prefix form, and exact API limit are measured. The decisive boundary for CO_E_PATHTOOLONG determines whether the same object can continue, a new object is required, or policy must change.

For CO_E_PATHTOOLONG, 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.

Evidence and telemetry

• Preserve full path and character count for CO_E_PATHTOOLONG.
• Preserve individual path components for CO_E_PATHTOOLONG.
• Preserve API and long-path support for CO_E_PATHTOOLONG.
• Preserve normalization and prefix for CO_E_PATHTOOLONG.
• Preserve shortened storage result for CO_E_PATHTOOLONG.

For CO_E_PATHTOOLONG, 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_PATHTOOLONG, use hashes, lengths, GUIDs, and SID strings rather than logging confidential payloads or credentials.

Diagnostic sequence

• Capture the raw unsigned value 0x80010135 and symbolic name CO_E_PATHTOOLONG 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_PATHTOOLONG.
• Reconstruct the operation timeline for CO_E_PATHTOOLONG, including object creation, thread or apartment initialization, security setup, callbacks, mutations, shutdown, and cleanup.
• Prove the decisive condition: the full normalized path, component lengths, prefix form, and exact API limit are measured.
• Inspect every output parameter, handle, interface pointer, token, SID, ACL, stream, buffer, server-side object, or asynchronous result produced before CO_E_PATHTOOLONG.
• Reproduce CO_E_PATHTOOLONG with the smallest safe input, change only the suspected precondition, and verify that both the HRESULT and postcondition change as predicted.

Correct handling and recovery

Shorten product-controlled components, use a supported long-path API when all consumers support it, and avoid truncating identity-bearing filenames.

Repeat the operation after CO_E_PATHTOOLONG only when the documented precondition, identity, apartment, object generation, buffer, or configuration has changed.

Lifetime, retry, and cleanup rules

After CO_E_PATHTOOLONG, determine whether the current object, interface pointer, call context, token, stream, metadata reader, asynchronous operation, or access-control instance remains valid. For CO_E_PATHTOOLONG, 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_PATHTOOLONG should state the trigger, maximum attempts, cancellation owner, and reconciliation step for effects that may have completed elsewhere.

Difference from nearby HRESULTs

CO_E_PATHTOOLONG is path-length validation; CO_E_FAILEDTOCREATEFILE can arise for permissions, existence, storage, or other file causes.

Merging CO_E_PATHTOOLONG with the neighboring HRESULT would choose the wrong retry, recreation, authorization, or cleanup path.

Practical scenario

A deeply nested service installation creates an ACL cache filename beyond a legacy limit. Storage moves to a short application-data root with a GUID key.

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

Developer and administrator guidance

Branch on CO_E_PATHTOOLONG before a broad COM error handler when its cleanup, recreation, retry, security, or user-disclosure path is unique. Preserve 0x80010135, interface IID, method, component build, process and thread IDs, apartment model, and correlation ID in structured telemetry.

After CO_E_PATHTOOLONG, 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_PATHTOOLONG.

References

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

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