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E_NOINTERFACE
Requested COM interface is not supported
E_NOINTERFACE is HRESULT 2147500034 (0x80004002) from winerror.h. AllStat describes it as “No such interface supported.” The value must be interpreted at IUnknown::QueryInterface, activation, aggregation, or a language projection requesting a particular IID, because the same high-level symptom can come from a different contract boundary and require different cleanup.
The decisive Interpretation is that the live object does not expose the requested IID under its current identity and aggregation rules. A diagnostic event for it should retain both representations of the HRESULT and the exact API boundary that produced it.
Where the result appears
- This result may surface in IUnknown::QueryInterface, activation, aggregation, or a language projection requesting a particular IID.
- The first boundary to preserve for it is the exact activation, initialization, call-control, or lifetime step that returned it.
- record whether the failure occurred before an object identity existed, while a method was running, or during shutdown; those phases imply different ownership and retry rules.
Before assigning cause to this result, identify the responsible thread, apartment, process, library generation, and server instance rather than relying on the final dialog text.
Typical causes and interpretation boundary
Common cause categories for it are: the IID belongs to another component version; the caller queried the wrong object; aggregation or tear-off rules differ from the caller assumption. The candidate causes for it are alternatives, so test one precondition at a time instead of applying several broad repairs together.
The check that separates this result from nearby HRESULTs is: the live object does not expose the requested IID under its current identity and aggregation rules. When the boundary condition behind it has not been proven, avoid retries or repairs that assume a different neighboring HRESULT.
Correct handling and recovery
The appropriate recovery is to treat the capability as unavailable, query only documented interfaces, and select a compatible component or code path; do not cast an unrelated pointer. Before retrying this result, specify which precondition changed and how duplicate effects or stale outputs will be detected.
Inspect every output before cleanup because interfaces, buffers, server effects, or metadata handles may be partially initialized.
Practical scenario
A plug-in requests a newer configuration interface from an older in-process server and disables only the optional settings panel.
Test it by reproducing the smallest failing contract, recording postconditions, and then changing a single input or state transition.
Difference from related HRESULTs
CLASS_E_CLASSNOTAVAILABLE concerns creation of the class; it occurs after an object identity exists but lacks the requested contract.
Keeping it separate from its neighbor improves retry, cleanup, and user messaging because the two results imply different postconditions.
Developer and administrator guidance
Code handling it should classify it by lifecycle and ownership rather than by the high bit alone. For <code>it</code>, initialization failures normally require rebuilding the process or thread environment, capability results require a fallback, and uncertain remote outcomes require reconciliation before retry.
Operational dashboards should keep it distinct from generic COM failures and attach deployment, service, package, runtime, policy, and architecture dimensions. Administrators should avoid broad registry edits, blanket firewall changes, or permission expansion unless the captured evidence for it identifies that subsystem.
References
- Microsoft: COM error codes
- Microsoft: COM processes, threads, and apartments
- Microsoft: COM security defaults
- Microsoft: HRESULT values
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