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ERROR_CALLBACK_INVOKE_INLINE
The callback function must be invoked inline.
ERROR_CALLBACK_INVOKE_INLINE is Win32 error 812 (0x32C) and belongs to callback dispatch and completion. The system description identifies the immediate condition but does not identify the caller, object, policy, device, service instance, or transition that produced it.
Interpret this result at the API boundary that returned it. Capture it before logging, cleanup, or another Windows call can replace the thread-local last-error value. Compare the recorded inputs with the documented precondition for callback dispatch and completion rather than starting with a broad system repair.
Where the result appears
- This result can surface during an API that can queue or synchronously invoke a completion callback.
- This result can surface during a framework deciding that deferred dispatch cannot preserve ordering.
- It can surface during a callback tied to a short-lived stack or request context.
- It can surface during a completion path that must run before the initiating call returns.
Likely causes
- the callback contract requires execution on the current call path.
- the operation completed before asynchronous dispatch was established.
- the callback owns data whose lifetime ends at return.
- ordering constraints prohibit handing the callback to another thread.
Diagnostic sequence
Diagnosis of it starts with the exact request type: read, write, create, transition, validation, cancellation, or administrative action. Identify the object generation and subsystem owner, then decide whether the failure happened before side effects, during a partial transition, or after completion. This ordering matters in callback dispatch and completion because a blind retry can hide stale state or repeat a non-idempotent change.
- record API name and documented callback contract.
- record whether the callback ran before the initiating function returned.
- record thread identifier, reentrancy depth, and held locks.
- record lifetime of callback context and captured buffers.
- record the completion status delivered to the callback.
Correlate it with the owning component’s operational log, the Windows System log, and any subsystem trace. Telemetry for this Win32 error should preserve native identifiers such as a path or file ID, handle generation, node or peer identity, policy ID, object version, offset and length, or transaction token. Retain decimal 812, hexadecimal 0x32C, and the producing API even when a localized message is also shown.
State boundary to prove
The decisive boundary for this Win32 error is whether the callback contract requires execution on the current call path. Prove or disprove that proposition using API name and documented callback contract together with whether the callback ran before the initiating function returned. When observations for this Win32 error disagree, preserve both and inspect the transition between them instead of choosing the more convenient value.
A focused validation for this Win32 error should recreate the relevant part of this situation: a wrapper assumes every completion is posted to a worker thread. The API returns this status, and the fixed wrapper executes the handler on the current thread without holding its outer mutex. The negative case should keep the responsible condition unchanged and confirm error 812; the recovery case should change only that condition and verify a successful result without an unrecorded side effect.
Handling, retry, and recovery
Invoke or accept the callback inline as the API requires, while making the handler reentrancy-safe. Do not blindly enqueue it later because that can outlive supplied storage or reverse completion order.
Retry it only after evidence shows a change in callback dispatch and completion. Initialization, asynchronous completion, recall, or service readiness can justify bounded backoff; malformed metadata, invalid identifiers, policy rejection, unsupported versions, and integrity failures require correction. Before repeating a write or configuration operation after it, query completion state explicitly.
What to log for support and telemetry
- log decimal 812, hexadecimal
0x32C, and the producing API. - log the target object and observed callback dispatch and completion state.
- log caller identity, process and thread IDs, machine or node identity, and UTC time.
- log attempt number, elapsed time, previous result, and any partial side effect.
- retain the first lower-level or component-specific error before Win32 translation.
Difference from nearby codes
This status communicates a dispatch requirement rather than failure of the callback itself.
Practical example
A wrapper assumes every completion is posted to a worker thread.
Developer and administrator guidance
Code that handles it should keep its Win32 domain visible across exceptions, RPC responses, and JSON or REST wrappers. Administrators should verify the subsystem evidence before changing policy, deleting state, forcing failover, or replacing storage. Recovery is demonstrated only when a test observes 812, changes the responsible condition, and confirms that the same operation succeeds without hidden data loss.
References
- Microsoft: System Error Codes (500–999) — reference for error 812.
- Microsoft: File management functions — reference for error 812.
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