# Binary Symbol Table Diff Engine

## Module
BinaryIndex

## Status
VERIFIED

## Description
Symbol table comparison between binary versions tracking exported/imported symbol changes, version map diffs, GOT/PLT table modifications, and ABI compatibility assessment. Produces content-addressed diff IDs for deterministic reporting.

## Implementation Details
- **Modules**: `src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/`
- **Key Classes**:
  - `SymbolTableDiffAnalyzer` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/SymbolTableDiffAnalyzer.cs`) - computes diffs between symbol tables with `ComputeDiffAsync` and `AssessAbiCompatibility`
  - `SymbolTableDiff` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/SymbolTableDiff.cs`) - diff result model with added/removed/changed symbols
  - `VersionMapDiff` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/VersionMapDiff.cs`) - tracks changes in ELF version maps
  - `AbiCompatibility` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/AbiCompatibility.cs`) - ABI compatibility assessment (FullyCompatible, Warnings, Incompatible)
  - `DynamicLinkingDiff` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/DynamicLinkingDiff.cs`) - GOT/PLT table modification tracking
  - `NameDemangler` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/NameDemangler.cs`) - C++ symbol name demangling
- **Interfaces**: `ISymbolTableDiffAnalyzer` (`src/BinaryIndex/__Libraries/StellaOps.BinaryIndex.Builders/SymbolDiff/ISymbolTableDiffAnalyzer.cs`)
- **Registration**: `SymbolDiffServiceExtensions` for DI setup

## E2E Test Plan
- [ ] Compute diff between two ELF binaries with known symbol changes and verify added/removed symbols are correctly identified
- [ ] Verify `AssessAbiCompatibility` returns `FullyCompatible` when only symbols are added
- [ ] Verify `AssessAbiCompatibility` returns `Incompatible` when exported symbols are removed
- [ ] Verify version map diff detection for ELF version script changes
- [ ] Verify C++ symbol demangling produces human-readable names via `NameDemangler`
- [ ] Verify content-addressed diff IDs are deterministic for identical inputs

## Verification
- Verified by QA FLOW run `run-001` on 2026-02-11.
- Evidence: `docs/qa/feature-checks/runs/binaryindex/binary-symbol-table-diff-engine/run-001/` (Tier 0/1/2 artifacts).