# m2comp step 7 — backend listing (tag: `m2comp-step7`)

`MGen.DumpImage` prints the assembled image to StdOut after every
successful emit: global layout per scope (name/slot/size), the
procedure table (number/address/depth), then disassembled code
with resolved labels. Unknown bytes degrade to `DB` (never fail).
A full sweep over all test sources shows zero unknowns. Suite
65/65 (61 inherited + 4 listing checks).

## What was built

- `src/MGen.def/.mod`: `DumpImage` + helpers (`WrS/WrI/WrHex2/
  WrHexQ/WrOp/OpLen/LabelAt`). Instruction sizes: 1, 2 (u8/ext),
  9 (immW/jp/jpfalse); `imm0..15`, signed local slots, `loadParam`
  for `03H..07H`; jumps resolve to `L<n>` (else `+rel`); `immW`
  payloads as 16 hex digits.
- Driver (`compiler.frm`): `DumpImage` after a successful
  `EmitModule` (listings already written, verdict last).
- `run_tests.sh`: `expect_code` (compile + grep backend listing):
  `realCmp` in `r_real` (listing-level guard for the step-5.2 D5
  fix), proc-table entry in `r_proc`, `jpfalse` in `t_case`,
  `storeIndir0` in `t_with`.

## Bugs found (all fixed, all covered)

- `immW` printed 32 hex digits (nibble helper already emits two
  chars each — dropped the manual split).
- `84H/85H` leaves take a u8 param count (undocumented in the
  local table); missing size broke alignment and swallowed a
  label. Same class of latent defect the listing exists to catch.

## Harness findings (multi-file listings)

- Definition and implementation share one `.LST` basename, so the
  committed listing is whichever unit compiles last; ad-hoc
  single-file compiles leave stale content behind. Canonical
  state = one full suite run (each session's last writer wins).
- The "second program" rejection first compiled `d_basic` twice
  in one process (duplicate errors, never reaching the driver
  gate). It now uses a dedicated empty `tests/d_second.mod`, so
  both programs parse clean and the driver's program-last gate
  fires with clean listings on both sides.

## Limits

- No source-line mapping (AST nodes carry no positions — needs
  grammar + AST + backend work; future step).
- Listing goes to StdOut only (one emit per run, after the
  per-file dumps).