# Step: M2make adapted to the current compiler

Tag `v3-m2make-adapt`. M2make suite **18/18**; compiler suite
**137/137**; fixpoint **OK** (2,156,095 bytes).

## Why

`tools/m2make/M2make.mod` is a dual-target build front-end (GNU
Modula-2 **and** V3).  Its source and README still carried
workarounds for compiler limits that V3 has since outgrown, and its
self-build did not use the driver it produces.

## What changed

1. **Source re-probed and relaxed.** Every "both compilers must
   accept" bullet was re-tested against the current `gm2 -fiso` and
   V3:
   - `AND`/`OR` **short-circuit** in both now, so the string helpers
     dropped their `done`-flag / index-stop gymnastics for ordinary
     guarded loops (`Len`, `Cmp`, `Cat`, `Sub`, `Lower`).
   - nested arrays and nested-element open-array actuals work; the
     flat pools are now documented as a style choice, not a limit.
   - `LONGINT` function results compile; only `VAL(INTEGER, long)`
     (64→32) is still rejected, so `LONGINT` stays a `VAR`
     out-parameter across the `M2makeOS` boundary.
2. **`--extra <path>` option.** `m2` mode links the C shim plus an
   extra C file (`cc <image>.s <shim> [<extra>] -o <out> -lm`), so a
   tool shipping its own C shim (M2make's `m2make_os.c`) can drive
   its own build.  Usage text updated.
3. **`build_m2.sh` dogfoods.** It sets the previous `b_v3/M2make`
   aside, and if one exists it drives the build itself
   (`M2make -c m2 --extra m2make_os.c -I runtime/syslib …`); the
   first run (no driver) falls back to the hand-spelled session.
   Re-running the script is thus a small self-host check for the
   tool.  (The previous driver predates `--extra`, so the very first
   dogfood run after this change bootstraps once.)
4. **README refreshed** — the `--extra` flag, the `-I` module
   resolution shape (same as `bootstrap/fixpoint.sh`), and the
   corrected constraint list.

## Verified

- `tools/m2make/tests/run_tests.sh` → **18/18** (both compilers build
  M2make; ordering, cycle detection, real gm2/m2 builds, up-to-date
  skips, and the cross-driver case).
- `build_m2.sh` clean build (bootstrap path), then a **dogfood** run
  driven by the freshly built `b_v3/M2make`.
- Compiler suite **137/137**; `bootstrap/fixpoint.sh` **FIXPOINT OK**.

## Files

`tools/m2make/M2make.mod` (string helpers, `--extra`, usage),
`tools/m2make/build_m2.sh`, `tools/m2make/README.md`.