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OSS_NULL_FCN
OSS_NULL_FCN (0x80093015) is an OSS ASN.1 runtime result for missing internal codec function pointer. An internal encode/decode entry is null, which points to incomplete initialization, unavailable generated code, or memory corruption. Because selected PDU and encoding rule is central to this condition, Microsoft’s HRESULT range and the OSS Nokalva return-code documentation should be read together. Start the investigation by recording loaded generated code modules, then separate the encoded value from generated artifacts, call arguments, and the runtime package actually loaded by the process.
What not to confuse it with: OSS_NULL_FCN
UNAVAIL_ENCRULES is a deliberate missing rule set; NULL_FCN can also indicate a damaged dispatch structure.
Locate the exact codec boundary
At the missing internal codec function pointer boundary, capture the first OSS function returning the value and note whether the operation was encode, decode, copy, compare, constraint validation, or trace setup. Preserve the selected PDU, encoding rules, and control object state before the failing dispatch; otherwise an outer certificate or security wrapper may hide the useful codec result behind a generic failure.
Evidence worth preserving
| Record | Diagnostic value |
|---|---|
| selected PDU and encoding rule | Locates the concrete message, allocation, module, or API boundary |
| loaded generated code modules | Separates payload-dependent behavior from build and process state |
| control object state before the failing dispatch | Makes the comparison reproducible without rewriting the original artifact |
Keep the original bytes or object graph unchanged while testing repeat with a newly initialized context. A change in loaded generated code modules after reload, plugin replacement, restart, or schema deployment is evidence about runtime state, not permission to discard the reproducer. When control object state before the failing dispatch points to one message, retain a cryptographic hash and the smallest safe sample instead of logging certificate, subscriber, credential, or private-key material.
A controlled way to reproduce it
- repeat with a newly initialized context
- verify required code units were linked
- compare the control object before and after unrelated calls
Decision matrix
| Controlled observation | Conclusion it supports |
|---|---|
| repeat with a newly initialized context | A changed outcome isolates the first proposed control instead of a blind retry |
| selected PDU and encoding rule differs between success and failure | The difference localizes the missing internal codec function pointer boundary before unrelated settings are changed |
| An independent decoder accepts the same artifact | Inspect generated schema, selected rules, ABI, and optional OSS modules before declaring the bytes invalid |
| A fresh control object changes the outcome | Investigate initialization, lifecycle, allocator ownership, configuration mutation, and concurrent access |
Instrumentation
Record the full 32-bit HRESULT and lower OSS return number together with operation direction, symbolic PDU, encoding rule, byte count, and generated-table identifier. Where selected PDU and encoding rule can expose sensitive content, a hash plus a bounded structural excerpt is safer than the complete payload. Use loaded generated code modules together with OSS module paths and versions logged once per process so packaging differences can be correlated without flooding normal diagnostics.
Exit criteria: the result
Restore a complete generated/runtime build and investigate any write that changes dispatch pointers. A recovery test built around repeat with a newly initialized context should replay the same operation under the same schema and encoding rule, retain one deliberately invalid control, and verify ownership and cleanup after both outcomes. Success after an unexamined retry is not proof that selected PDU and encoding rule now satisfies the codec contract.
Technical references
- Microsoft: OSS ASN.1 HRESULT definitions
- OSS Nokalva: encoder/decoder return codes
- OSS Nokalva: runtime functions and control initialization
- Relevant ASN.1 specification or runtime detail
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