# Session save — 2026-09-28: V3 self-hosting FIXPOINT reached

`master` — suite **111/111**, tree clean except the user's uncommitted
`compiler/toto.mod` edit.

## Headline: the fixpoint

`bootstrap/fixpoint.sh`:

```
Stage 1: gm2 builds V3 (CR -m)              -> m2s1
Stage 2: m2s1 compiles the whole compiler   -> stage2.ssa (assembled -> m2s2)
Stage 3: m2s2 compiles the whole compiler   -> stage3.ssa
cmp stage2.ssa stage3.ssa  *** FIXPOINT OK (1,991,439 bytes) ***
```

The V3 compiler now rebuilds itself to a **byte-identical image**.
Tags: `v3-fixpoint`, `v3-bootstrap`.

## The last fix (`b6ae57b`)

`QbeGen.InitHeap` allocated each nested element sub-array (`ARRAY … OF
ARRAY …` on the heap/stack) but never initialised its descriptor
header, so a local `ARRAY [0..15] OF Name` handed garbage to
`GetName` (scanner) when `names[i]` was passed as an `ARRAY OF CHAR`.
Now `InitHeap(eb, elem)` is called on each sub-array.

## Arc completed

From "sources compile and link" to the fixpoint — every step a real V3
runtime/ABI bug with a minimal repro: nested modules; inline record
array fields; the NUL-terminated string model; `p^` as a `VAR` actual;
de-eagered NIL guards; off-by-one string scans; short-circuit `AND`/`OR`;
nested-array heap initialisation.

## Codebases / tags of interest

- `v3-fixpoint` — `b6ae57b` (the fix + `docs/summary_fixpoint.md`).
- `v3-bootstrap` — `42cbe36` (`bootstrap/fixpoint.sh`).
- Earlier: `v3-short-circuit`, `v3-selfcompiles`, `v3-inline-array-fields`,
  `v3-nul-strings`, `v3-deref-var-actual`, `v3-selfcompile-image`, …

## Remaining polish

- Cross-stage `FileIO` selection is implicit (stage 1 uses the host
  `FileIO`; the compiled image embeds the self-hosted one). Make it
  explicit if desired.
- Optionally `M2make`-driven build; more stdlib; unicode (step 6 plan).
- The toolchain still needs gm2 only for Stage 1 (bootstrapping the
  seed binary); `fixpoint.sh` documents the stage-aware CR flag.

## Resume

```sh
cd .../m2compiler-V3
./bootstrap/fixpoint.sh          # FIXPOINT OK: stage2.ssa == stage3.ssa
cd compiler && ./build.sh && ./run_tests.sh   # 111/111
```