# Step: V3 compiler corpus run (gm2 testsuite)

Tag `v3-corpus-run`. V3 suite **151/151**, fixpoint OK (unchanged —
this only adds a harness and a doc).

## Why

The TopSpeed corpus validated the *sidecar grammar*, not V3 the
compiler (the sidecar is a separate `TSM2` binary built from
`TopSpeed-V3-M2.atg`; it reuses V3's `SymTab`/`QbeGen`/`FileIO` sources
but never runs `compiler/M2`).  So this step runs **V3 itself** over a
real standard-Modula-2 corpus: the gm2 testsuite
`testsuite/gm2/pim/pass` and `testsuite/gm2/iso/run/pass`.

Harness: `tools/v3-corpus/corpus.sh` (copies each file to a scratch
tree, compiles alone, splits failures into CRASH / LIB / LANG — see its
README).

## Baseline (after the crash fix)

| | files |
| --- | --- |
| total | **612** |
| **compile-OK** (0 errors) | **219** |
| CRASH (M2 died, rc ≥ 128) | **0** |
| LIB (imports a gm2 library V3 lacks) | **187** |
| LANG (real V3 gap) | **206** |

(Before the fix: 219 OK / **7 CRASH** / 182 LIB / 204 LANG.)  So ~187
of the 393 failures are simply **missing gm2 libraries** (`StrIO`,
`NumberIO`, `STextIO`, `SWholeIO`, `FpuIO`, `WholeStr`, `StdIO`,
`M2RTS`, `DynamicStrings`, `Processes`, …) — expected, not language
gaps.  The signal is the **206 LANG** files.

## Fix: long-line buffer overflow (the 7 "set crashes")

The 7 crashes (`largeset`, `program2`, `set9`, `sets3`,
`smallset4/5/6`) were **not** set bugs: those files contain a ~860-char
line (a 76-literal enumeration), and

- `PrintListing`'s line buffer was `ARRAY [0 .. 255] OF CHAR`, and
- `GetLine` wrote **without bounding** to `HIGH(line)`.

A source line longer than 255 chars therefore **overflowed the stack**
(corrupting locals and the return address) — hence the garbage line
number in the `.LST` and the segfault.

Fixed in `compiler/src/compiler.frm`:
- `GetLine` now truncates at `HIGH(line)` (still consuming the rest of
  the line so positions stay correct);
- `PrintListing`'s buffer is now `ARRAY [0 .. 4095] OF CHAR`;
- `PrintErr`'s caret loop is bounded by `HIGH(line)`.

Regression test: `compiler/tests/t_longline.mod` (406-char line, exit
0).  Suite **152/152**; fixpoint OK (2,339,115 bytes).

## Top remaining LANG gaps (from the corpus)

- **48 `not supported yet`** — deliberate V3 `230`s; the corpus shows
  which constructs matter, e.g. **array constructors**
  (`array {'h','e','l','l','o'}` in `arrayconst1`).
- **`undeclared identifier`** — mostly **`SYSTEM` facilities** V3 does
  not expose (`FROM SYSTEM IMPORT BYTE;` → `BYTE`), plus small library
  holes.
- **Anchored subranges** `INTEGER [-1 .. 24]` (`array2`, `array3`) —
  PIM form V3's `Subrange` does not parse (`';' expected` at `[`).
- **Unnamed parameters in procedure types**
  (`PROCEDURE (VAR ARRAY OF REAL)` in `another.mod`) — PIM allows
  them; V3 requires a name (`ident expected`).
- Assorted: `incompatible assignment`/`comparison` on char arrays,
  `invalid ArrayType`, `invalid call`, `FOR … BY`, etc.

## Reproduce

```sh
cd tools/v3-corpus
./corpus.sh            # -> 219 compile-OK / 0 CRASH / 187 LIB / 206 LANG
```

## Suggested next steps

1. **`SYSTEM` facilities**: expose at least `BYTE` / `WORD` /
   `SHORTADDR` etc. so `FROM SYSTEM IMPORT …` works.
2. **Anchored subranges** `T[lo..hi]` (small grammar addition).
3. **Unnamed proc-type parameters** (small grammar addition).
4. **Array constructors** `array{…}` (bigger: codegen).

## Files

`tools/v3-corpus/{corpus.sh,README.md}`,
`compiler/src/compiler.frm` (long-line fix),
`compiler/tests/t_longline.mod`, `compiler/run_tests.sh`, this doc.