Field Context

offset_sig

Overview

offset_sig is the relocation signature used to recover struct-member offsets across versions.

Field Context

• Related YAML fields: struct_name, member_name, offset, size, offset_sig (optional offset_sig_disp).

Generation Principle

• In this repository, authoring usually follows the struct-offset signature workflow (.claude/skills/generate-signature-for-structoffset/SKILL.md).
• Signature is built near an instruction that encodes/uses the target member offset.
• Volatile bytes are wildcarded (??) to improve cross-version robustness.
• Observed outputs generally use forward anchoring (signature starts at target instruction, offset_sig_disp omitted/0).
• Acceptance goal: unique matching plus reliable offset re-derivation.

Usage Method

• In preprocess_struct_offset_sig_via_mcp, old offset_sig is reused to recover the new offset.
• Flow:
  1. Load struct_name, member_name, offset_sig, optional offset_sig_disp, optional size.
  2. Unique-match offset_sig -> sig_addr.
  3. Compute instruction address: inst_addr = sig_addr + offset_sig_disp (default 0).
  4. Decode instruction and inspect operand positions (offb/offo) and candidate sizes.
  5. Extract displacement/immediate candidates; prefer candidates matching old offset when available.
  6. Emit new YAML with updated offset, carrying offset_sig and optional metadata.

Practical Notes

• Multi-hit offset_sig is rejected.
• Non-zero offset_sig_disp means signature starts before target instruction.
• offset may change across versions; offset_sig should remain stable enough to re-derive it.
• Weak signatures (too short/too wildcarded) reduce long-term reliability.