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ERROR_INVALID_SIGNAL_NUMBER
What ERROR_INVALID_SIGNAL_NUMBER means
The signal number supplied to the process-control operation is not valid. This code is a direct parameter validation failure in a legacy signaling API. Signal ranges and meanings can differ between compatibility subsystems, so a value valid in one environment may be invalid in another.
Common causes
- The caller uses a platform-specific signal constant in the wrong subsystem
- An uninitialized variable becomes the signal number
- A configuration value is outside the allowed range
- Enumeration values changed across module versions
How to investigate
- Log the numeric signal and originating symbolic name
- Check the allowed range for the exact API and subsystem
- Validate configuration before conversion to the API type
- Compare caller and callee header or SDK versions
Developer guidance
Use typed enumerations and reject unknown values at configuration boundaries. Avoid forwarding arbitrary integers directly to process-control APIs.
Administrator and support guidance
Review recently changed scripts or configuration that select signal actions. The operating system generally does not need repair.
How this code differs from related results
This result occurs before delivery. Codes such as ERROR_SIGNAL_REFUSED describe what happened after a valid signal was addressed to a target.
Evidence worth collecting
For ERROR_INVALID_SIGNAL_NUMBER, begin the trace at the operation where the caller uses a platform-specific signal constant in the wrong subsystem. Preserve the exact API boundary, numeric result, process and thread identifiers, relevant object state, and the component version. The first verification point should be to log the numeric signal and originating symbolic name. This evidence distinguishes the specific this result contract from a later secondary failure.
Recovery and verification
Recovery for it should address the observed condition rather than merely retrying the same call. After the change, reproduce the scenario in which the caller uses a platform-specific signal constant in the wrong subsystem, then confirm that the intended operation completes and that cleanup returns all associated resources. Also verify that the next repeated operation follows the same successful path without increasing the resource class implicated by this result.
When to escalate
Escalate this result with a minimal reproduction focused on the failing process-control boundary. Include the operating-system build, binary architecture, runtime or compatibility-layer version, the exact input values, and a timestamped trace showing the caller uses a platform-specific signal constant in the wrong subsystem. For the result escalation record, note whether changing concurrency, object lifetime, target process, module set, or endpoint location alters the result.
References
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