macOS kernel return 46 (KERN_NOT_SUPPORTED): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The Mach operation targeted an empty thread activation with no linked thread.

Could be also:
Constant	Type	OS
ippStsNoAntialiasing	Intel Ipp Status	Any
EL3HLT	errno	Linux
EPFNOSUPPORT	errno	Mac
ENOLCK	errno	Solaris
DATA_BUS_ERROR	BugCheck Code	Windows

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KERN_RPC_CONTINUE_ORPHAN	KERN_NODE_DOWN

KERN_NOT_SUPPORTED

Not a generic feature-unsupported status

KERN_NOT_SUPPORTED has a specific historical meaning in XNU kern_return.h: the operation targeted an empty thread activation with no linked thread. It should not be read as a broad statement that macOS, a device, or an API feature does not support the requested capability.

The right diagnosis is an object-state check. Identify whether the caller retained a thread-activation reference after it lost its thread, or passed an activation object to an API that requires a linked, live thread.

What to inspect

Determine what created the activation and when a thread was associated with it.
Check whether thread termination or task teardown detached the underlying thread first.
Determine whether legacy Mach code can use a modern supported abstraction instead.
Look for a more precise lifetime result from the surrounding API after the activation becomes invalid.

References

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