# m2compiler-V3 — gap analysis (2026-09-30)

Suite **169/169**, self-hosting fixpoint OK (2,754,353 bytes).
Corpus at this point (with `$V3_LIBS`):

| corpus | compile-OK | CRASH | LANG |
| --- | --- | --- | --- |
| gm2 testsuite (612) | 392 | 0 | 212 |
| gm2 stdlib (336) | 127 | 0 | 209 |

Failure taxonomy (testsuite, per file): `undeclared identifier` 65,
`not supported yet` 43, `invalid call` 25, `incompatible assignment`
25, `ident expected` 8, `invalid ImpName` 7.

## 6. Fixed today (items 1–5)

1. **`FROM libc` intrinsic** — `printf`/`exit`/… import as permissive
   external C procedures (varargs, no result) and bind to the C
   symbols; string/CHAR-array actuals pass as `descriptor+8`.  This
   removed the dominant undeclared bucket (136 → 65 files).
2. **`SET OF enum` and `SET OF <char-range>`** (plus enum subranges
   `[a..d]`, `ARRAY [FALSE..TRUE]`), and the set span limit lifted
   256 → 65536.
3. **`MIN`/`MAX` for REAL/LONGREAL/LONGINT** and gm2 sized names
   (`LONGCARD`, `SHORTREAL`, `INTEGER8/16/32/64`, `CARDINAL8/…`).
4. **SYSTEM/PIM set builtins** — `INCL`/`EXCL` (statements) and
   `SHIFT`/`ROTATE` (expressions), bit-by-bit over a runtime amount.
5. **Module-level forward type references** — a global may name a type
   declared further down; its emission is deferred until the TYPE
   block completes (TYPE-block forwards already worked).


## 1. Language features genuinely missing

Ranked by corpus impact (each verified by a failing file or a probe):

1. **Sets over enumerations and CHAR ranges** — `SET OF <enum>` and
   `SET OF ['A'..'z']` are `230`.  Only `bool`/`char`/integer subrange
   bases are accepted.  (`goodifin.mod`, `charset2.mod`, `enum3.mod`.)
2. **`MIN`/`MAX` for REAL/LONGREAL/LONGINT** — only ordinal types,
   arrays and sets are handled; `MAX(REAL)` / `MIN(LONGINT)` are `230`.
   (`maxreal.mod`, `minmaxreal2.mod`, `longmm.mod`, `constcast.mod`.)
3. **gm2 sized types** — `LONGCARD`, `SHORTREAL`, `INTEGER8/16/32/64`,
   `CARDINAL8/16/32/64`, `LONGWORD` undeclared.
4. **SYSTEM builtins** — `SHIFT`, `INCL`, `EXCL`, `ROTATE`, `LOC`,
   sized-bit names (`INCL`/`EXCL`/`SHIFT` recur).
5. **Enum subranges / BOOLEAN bounds** — `[a..d]`,
   `ARRAY [FALSE..TRUE] …` are `230`.
6. **`String`** — *not* a gm2 built-in: it is an opaque type imported
   from a definition module (`DynamicStrings`, or a local `opaque`).
   V3 now treats unresolved (opaque/forward) aliases as pointer-like,
   which is the real fix.
7. **`GOTO` + labels** — parse error.
8. **Whole-variant-record assignment/equality** — deliberately `236`.
9. **Nested local `MODULE`** — parsed, not lowered.
10. **Result suffixes** `F()^`.
11. **Generics** — not started (`docs/analysis_generics.md`).
12. **Coroutines / processes** (`NEWPROCESS`/`TRANSFER`/`IOTRANSFER`).
13. **Multiple inheritance** — deliberately out of scope (`docs/OOP.txt`).
14. **Recursive `DISPOSE`** (shallow today) and `runtime/syslib/Trap`
    (traps are `$abort`, rc 134).

Procedure types and indirect calls do work (`t_proctype` passes);
`docs/features.md` still lists them as ⏸ — stale.

## 2. Library

- **gm2-only modules V3 lacks**: `String`, `StrIO`, `RealStr`/`WholeStr`,
  `LongIO`/`LongMath`/`LongStr`, the `InOut`/`StdIO`/`STextIO`/
  `SWholeIO`/`SIOResult` family, `IOConsts`, `Termination`,
  `StdChans`/`StreamFile`/`FIO`, `SysStorage`, `wrapclock`/`time`,
  `ChanConsts`/`GenDevIF`/`DeviceTablePtr` (the gm2 device/IO framework).
- **`FROM libc IMPORT printf, exit`** — no intrinsic `libc` module;
  this is the largest `undeclared identifier` bucket (163 + 141
  occurrences) and is not a real language gap.

## 3. Architecture / robustness

- **No AST, single pass.**  Declaration-before-use is enforced, so
  forward references in `CONST`/expressions fail (e.g. `arraycons3.mod`
  declares `TYPE` after the `CONST` constructor and is rejected).  Only
  `FORWARD` procedures and `ForwardType` are tolerated.
- **Single image only** — no per-module object emission, no import
  cycles.
- **Driver robustness** — `M2` exits 0 even with errors (harnesses parse
  the `.LST` verdict) and aborts on a missing input file.
- **Fixed-size tables** — 64 formals/locals (233 past that), 64 call
  args, 256 VAR-actual note entries, 4096 string literals, 256 pooled
  constructors, 8 constructor levels, 4 MiB image buffer.
- **Weak error recovery** — one bad token cascades into `ident
  expected` / `'END' expected`.

## 4. Deliberate dialect choices (not gaps)

Classic identifiers (no `_`), `#` not `<>`, no octal `B`/`C`, `0x`-only
hex, `NOT`/`AND`/`OR` only, TopSpeed legacy isolated in the sidecar.

## 5. Biggest wins (all five landed today — see §6)

1. ~~**`FROM libc` intrinsic**~~ ✅
2. ~~**`SET OF enum` + `SET OF char-range`**~~ ✅
3. ~~**`MIN`/`MAX` for REAL/LONGINT** + **gm2 sized types**~~ ✅
4. ~~**SYSTEM `INCL`/`EXCL`/`SHIFT`/`ROTATE`**~~ ✅
5. ~~**Forward type references**~~ ✅ (module-level globals; TYPE-block
   forwards already worked)

Also done: opaque/pointer-like types (incl. `String`), variant-record
assignment (flat blit), nested-`MODULE` lowering, `ADDRESS`↔pointer
assignment.

Remaining after today: `GOTO`/labels, generics, multiple inheritance
(deliberate), result *suffixes on statement designators*, and the
channel/device library holes in §2.

## 7. Done after the gap analysis (this session)

- **Result suffixes** — `F()^`, `F()[i]`, `F().field` (expression
  context).  Statement-context suffix targets (`F()[i] := x`) and
  chained post-call calls (`F().M()`) are still not accepted.
- **PIM coroutines** — `PROCESS` + `NEWPROCESS`/`TRANSFER`/`IOTRANSFER`
  (ucontext-backed).
- **Core text/ISO library** — `ConvTypes`, `IOConsts`, `SIOResult`,
  `TERMINATION`, `StrIO`, `InOut`, `StdIO`, `WholeStr`, `RealStr`,
  `LongStr`, `LongMath`, `LongIO`, `STextIO`, `SWholeIO`, `SRealIO`,
  `DynamicStrings` (core), `SysStorage`.
- **Backend** — procedure values / LONGINT are 8-byte in array load/
  store and in the parameter prologue (were 32-bit); driver session
  file cap 32 → 128.