# Milestone: V3 self-hosts (byte-identical fixpoint)

Tags `v3-fixpoint`, `v3-bootstrap`, `v3-selfhosting`.
Suite **111/111**.

## What it means

`m2compiler-V3` now compiles its **own complete source set** with
itself, reproducing its image **byte for byte**:

```
bootstrap/fixpoint.sh
  Stage 1  gm2 -fiso builds V3 (CR -m)             -> m2s1
  Stage 2  m2s1 compiles SymTab QbeGen M2S M2P M2  -> stage2.ssa  -> m2s2
  Stage 3  m2s2 compiles the same set              -> stage3.ssa
  cmp                                               -> FIXPOINT OK
                                                       (1,991,439 bytes)
```

The compiler no longer needs GNU Modula-2 except as a one-time seed for
Stage 1; Stage 2 onward is V3 all the way down.

## The pipeline

- **Frontend**: Coco/R grammar (`src/M2.atg` → `M2S` scanner, `M2P`
  parser, `M2` driver).
- **Symbol table** (`SymTab`) + **QBE backend** (`QbeGen`) → SSA text.
- **`qbe` → `cc`** (with `runtime/syslib/shim.c`).
- Two compiler generations coexist: gm2 builds it for the seed; V3
  rebuilds it thereafter.

## Building blocks delivered along the way

Language: scalars, composites (arrays/records/sets/pointers), control
flow, procedures (value/VAR/open/nested + static links/FORWARD),
separate compilation (DEFINITION/IMPLEMENTATION, IMPORT, opaque),
64-bit ints, `ADDRESS`/`ADR`/`SIZE`, procedure types + indirect calls,
Wirth-style nested modules, short-circuit `AND`/`OR`, `BITSET`, typed
set constructors, `HALT`, and GNU-compatible literals (`0x`, octal
char, `LENGTH`/`ORDL`/`CAP`, `&`/`~`).

Runtime/ABI: NUL-terminated CHAR arrays (terminator slot at index =
count), inline record array fields, heap/stack descriptor initialisation
(nested arrays included), string lib (`Strings`), `FileIO` (host for
Stage 1; self-hosted `runtime/syslib/FileIO` for Stage 2+), C shim.

## Reproduce

```sh
cd /home/eric/Projets/Projets-Modula2/MyWork/m2compiler-V3
./bootstrap/fixpoint.sh                        # FIXPOINT OK
cd compiler && ./build.sh && ./run_tests.sh    # 111/111
```

## Deliberate divergences (per plan)

No generics/interfaces, no ARC/exceptions, QBE backend is terminal (no
native codegen), Linux only, and some GNU/classic conveniences accepted
for self-hosting. `SYSTEM` facilities are built-ins, not an importable
module.

## Where to go next

- Make cross-stage `FileIO` selection explicit; `M2make`-driven builds.
- Broaden the stdlib; the Unicode step from `docs/plan.md` (UCHAR/
  UString).
- Optional native backend / additional targets (Blaise parity).