data-diff

name	data-diff
description	Diff a DATA symbol (vtable ??_7Class@@6B@, RTTI, pointer/jump table, string pool, static initializer) between the target and the decompiled build, showing byte differences and — for each relocation slot — which function/symbol each side points to. Use when a data symbol is below 100%, or to find which vtable slot resolves to the wrong function. The MCP run_objdiff wrapper does not expose data diffs, so this calls objdiff-cli directly.
argument-hint	<symbol> [--unit UNIT]
allowed-tools	Bash(bin/objdiff-cli *), Bash(nm *), Read, Grep, Glob

Data Diff

Structured byte- and relocation-level diff of a data symbol, target vs the decompiled build. objdiff's normal output (and the mcp__orchestrator__run_objdiff tool) diffs code; --include-data (a milohax-fork feature) handles data: vtables, RTTI, pointer/jump tables, string pools, static initializers.

This answers "where does my decompiled build diverge from the target" for a data symbol — slot by slot, byte by byte. It's the data analogue of /compare-asm.

Arguments

$ARGUMENTS

• First positional: the data symbol, MSVC-mangled — e.g. a vtable ??_7FilePath@@6B@, RTTI ??_R4..., or a string/array symbol. Quote it (the names contain ?@).
• --unit UNIT — objdiff unit. Usually needed for data symbols, which are local to a translation unit.

Steps

1. Run the data diff (directly via bin/objdiff-cli, since the MCP wrapper doesn't pass --include-data):

   bin/objdiff-cli diff -p . -u <unit> "$0" -f json-pretty --include-data
   

   If you don't know the unit, find which object defines the symbol, or use report query to locate the data symbol's unit.

2. Read data_diff.relocations — the actionable part for vtables/pointer tables. Each entry is one pointer slot:

   • target_symbol — function/symbol the target slot points to.
   • base_target_symbol — where the decompiled build points, shown only when it differs. kind: "replace" + a base_target_symbol means this slot resolves to the wrong function — the highest-signal vtable mismatch.
   • A slot present only in the base build is kind: "insert" (empty target_symbol, a base_target_symbol) — an extra/misordered entry.
   • addend / base_addend flag a pointer-into-symbol offset mismatch.

3. Read data_diff.segments for raw (non-pointer) bytes — string contents, enum tables, packed structs. bytes is the target side, base_bytes the decompiled side (present only when they differ); equal runs carry no bytes. Use for string-literal typos and wrong initializer values.

4. Act on it. A replace reloc → the source references the wrong function/global, or the class declaration has the wrong virtual-function order. A replace segment → wrong literal/init value at that offset.

Example

$ bin/objdiff-cli diff -p . -u <unit> "??_7FilePath@@6B@" -f json-pretty --include-data
  data_diff.relocations:
    +0x08  equal    ??_GFilePath@@UAEPAXI@Z
    +0x0c  replace  target=?Print@String@@QBEXPBD@Z  base=?Print@FilePath@@QBEXPBD@Z

Slot +0x0c resolves to the wrong method on the decompiled side — fix the source reference or the virtual-function order so it points to String::Print.

When to Use

• A vtable / RTTI / data symbol is stuck below 100% and you need to know which slot.
• Verifying a class's virtual-function order produced the right compiled vtable.
• A string-pool or static-initializer data symbol mismatches and you need the differing bytes.

Tips

• --include-data is a no-op on code symbols (no data_diff emitted), so it's safe to add when unsure whether a symbol is code or data.
• For code analysis keep using mcp__orchestrator__run_objdiff / mcp__orchestrator__run_diff_inspect; this skill covers the data gap the wrappers don't.
• Full schema (including the instruction branch graph): docs/tools/objdiff/JSON_EXTENSIONS.md.