What does Windows error code 563 (ERROR_INVALID_LDT_OFFSET) mean?

ERROR_INVALID_LDT_OFFSET

The starting value for the LDT information was not an integral multiple of the selector size.

ERROR_INVALID_LDT_OFFSET is Windows system result 563 (0x00000233). Microsoft defines it as “The starting value for the LDT information was not an integral multiple of the selector size.”

How to classify the result

This result represents an x86 Local Descriptor Table offset alignment failure. The correct interpretation depends on the exact starting byte offset or selector supplied to the descriptor-table update.

Where it can appear

• This result can appear in an x86 compatibility subsystem applying a partial LDT update.
• This result can appear in a debugger or emulator restoring descriptor state.
• It can appear in native status conversion after validating a descriptor range.

Typical causes

• the caller passed a byte offset that is not divisible by the selector size.
• a selector value was shifted or unshifted twice.
• an array index was supplied where a byte offset was required.
• structure packing changed the computed start position.
• the range began in the middle of an existing descriptor.

Useful evidence

• Record raw starting offset.
• Record derived selector number.
• Record entry size and structure packing.
• Record range length and ending boundary.
• Record architecture, process bitness, and native status.

Recovery and retry

Recalculate the start from a validated selector boundary and submit the smallest correctly aligned range.

An alignment failure is deterministic; backoff does not help. Retry only with a corrected offset and an unchanged intended descriptor set.

Difference from related results

ERROR_INVALID_LDT_SIZE rejects the extent of the update, while it rejects its starting boundary. Both can appear before descriptor contents are examined.

Example

An emulator restores selector 7 but mistakenly sends offset 7 rather than 7 multiplied by the entry size. The corrected conversion starts at the proper boundary and leaves neighboring descriptors untouched.

Developer and administrator guidance

Use typed helpers for selector-to-offset conversion and unit-test the first, last, and overflow boundaries. Logs should label every quantity with its unit.

References

• Microsoft: System Error Codes 500–999
• Microsoft Open Specifications: Win32 error values
• Microsoft: LDT_ENTRY
• Microsoft: GetThreadSelectorEntry