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ERROR_BAD_DLL_ENTRYPOINT
What ERROR_BAD_DLL_ENTRYPOINT means
The loader or calling component expected a function entry point that is absent, malformed, incompatible, or points to an unusable implementation. The file may be the wrong version even when its name and signature appear valid.
Where it commonly appears
- Application startup and plug-in loading
- Delay-loaded imports
- Mixed-version deployments
- Manual GetProcAddress-based integration
Likely causes
- The deployed DLL lacks the required exported symbol
- Name decoration, calling convention, or architecture differs
- An incompatible DLL earlier in the search path was loaded
- The export table or binary is corrupt
- A forwarded export resolves to a missing dependency
Diagnostic checklist
- Record the full path of the DLL actually loaded, not only its base name
- Inspect exports with a binary analysis tool and compare the exact expected symbol
- Check process and DLL architecture
- Use loader diagnostics to find search-order substitutions and missing forwarded dependencies
- Compare file version and hash with the intended deployment artifact
Guidance for developers
Bind to documented exports and validate optional entry points before calling them. Avoid relying on ordinal-only imports across versions. Package private dependencies beside the application or use a controlled loader search path.
Guidance for administrators
Repair or reinstall the application as a unit. Copying a DLL from another machine can create a more subtle version mismatch and should not be the first remedy.
Example incident
A plug-in built against a newer SDK expects InitializeEx, but deployment includes an older DLL exporting only Initialize. The file loads, yet entry-point resolution fails with this code.
Related conditions
ERROR_MOD_NOT_FOUND means a module could not be found; ERROR_PROC_NOT_FOUND is a closely related missing-export result. This code can also cover invalid entry-point behavior during loader processing.
Operational decision points
Operational triage should begin by deciding whether the report represents a loader contract condition and not merely a transient API failure. For ERROR_BAD_DLL_ENTRYPOINT, the deciding evidence is resolved path, expected export, actual exports, architecture, file version. Preserving this first-occurrence evidence is more useful than increasing retry frequency for investigation sequence 2.
- Impact boundary: identify the exact process, account, device, file, session, host, or connection affected by this result; do not assume the whole machine is in the same state.
- State change required: the next attempt is justified only after the relevant loader contract state can differ from the failed attempt.
- Partial outcome: verify whether the operation allocated resources, changed data, sent a request, or modified policy before this result was returned.
- Escalation evidence: preserve resolved path, expected export, actual exports, architecture, file version together with component version and the first preceding failure.
Concrete recovery example
Consider a case where a plug-in expected an export present only in a newer library. Repeating the same call leaves the underlying condition unchanged and produces another this result. The durable response is to deploy the matching binary and bind to documented exports. Validation for it should use one controlled operation and inspect both the returned status and the resulting state associated with case 2.
Monitoring and validation
A monitoring rule for it should distinguish first occurrence from repetition, group events by affected object, and correlate them with deployments or configuration changes. The recovery is complete only when the expected loader contract state is present and consistent; absence of another log line by itself is not sufficient proof.
Retain the original this result event until validation for investigation case 2 is complete. After it is corrected, verify that no partial or stale artifact specific to remediation sequence 2 remains before declaring recovery complete. This it-specific verification prevents a hidden secondary problem from surviving after remediation step 2.
References
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