What does HRESULT 0x000401E2 (MK_S_REDUCED_TO_SELF) mean?

MK_S_REDUCED_TO_SELF

Moniker reduction produced the same moniker

MK_S_REDUCED_TO_SELF is HRESULT 262626 (0x000401E2) from winerror.h. The documented description is “Moniker reduced to itself.” The high-order severity bit is clear, so this is a success result, but it carries more information than plain S_OK.

IMoniker::Reduce completed and determined that no simpler equivalent moniker could replace the current moniker.

State to verify

The central question is whether the returned moniker identity and ownership rules are honored even when the result refers to the original object.

A reliable interpretation of this result names the exact method contract, the object instance, and the outputs that remain valid. This prevents a success-with-information result from being promoted to full success or demoted to a generic error.

Where the result is encountered

• This result can appear in moniker canonicalization before binding; record the producing interface and method.
• It can appear in composite moniker simplification; record the producing interface and method.
• It can appear in running-object and link resolution code; record the producing interface and method.

Evidence to preserve

• Preserve input display name.
• Preserve bind context and reduction flags.
• Preserve returned IMoniker pointer identity.
• Preserve reference-count transitions.
• Preserve comparison and binding result after reduction.

Diagnostic sequence

• Capture the raw HRESULT 0x000401E2 immediately after the returning method and record whether the caller used SUCCEEDED, FAILED, equality testing, or exception translation.
• Verify the method-specific state: the returned moniker identity and ownership rules are honored even when the result refers to the original object.

Correct handling, retry, and recovery

Continue with the existing moniker and avoid recursive reduction. Respect COM reference ownership because the returned interface may alias the original moniker.

Practical validation scenario

A resolver reduces a canonical file moniker that contains no redundant components. It receives it, retains one valid reference, and proceeds directly to binding.

Difference from nearby HRESULT values

MK_S_ME, MK_S_HIM, and MK_S_US describe common-prefix relationships; it describes reduction output.

Developer and administrator guidance

References

• Microsoft: COM moniker status codes
• Microsoft: IMoniker::Reduce
• Microsoft: IMoniker