# TP3-comp — Turbo Pascal 3 clone in GNU Modula-2 (ISO)

**Status:** compiler-core (`Compiler.mod`) + shell compiled clean with
`gm2 -fiso -Wall`, and the ISO shell `tpshell` builds and runs (ESC-key
driven, TP3-style DOS screen redraws).  This is the working *implementation*
companion — the human overview is `TP3-COMPILER.md` history summary and
`RESUME-TP3.md`.

## Build (proven, two-phase — the ONLY recipe that beats GNU gm2's
pass-3 "too many errors / too many identifiers" cap on compiler-sized
whole-program programs)

```
gm2 -fiso -c Compiler.mod          # phase A: small per-module pass
gm2 -fiso -fgen-module-list=modules.lst -o /dev/null \
    Compiler.mod Term.o TextBuf.o Posix.o Editor.o  # phase B1: build list
gm2 -fiso -fuse-module-list=modules.lst -o tpshell \
    Shell.mod Compiler.mod Term.o TextBuf.o Posix.o Editor.o  # phase B2: link
```
(Equivalent make target `tpshell` in `shell/Makefile`.) The single `gm2 -o`
whole-program pass 3 silently caps identifier/error counts — see
`build_tpshell.sh`.)

## What was changed inside `Compiler.mod` (all ISO-legal, gm2-verifiable)

1. **CHAR vs hex-int comparisons** (lines ~829, ~1086): Modula-2 `CHAR` is
   not the ZType; `ch = 09H` → `ORD (ch) = 09H` (and likewise 0DH/0AH/0CH).
2. **Return-value discard** (ISO forbids drop in statements; gm2 treats as
   error and has no `-Wno-`): added `DropCh/DropB/DropC` discard helpers
   and wrapped ~39 statement call sites of `GetCh`, `MatchKey`, `NewSym`,
   `EmCall`, `EmJmpNear` (no output reground clutter; TP3 TP5 `cascadepos`
   `waitkey` semantics preserved via the editor's ESC wait).
3. **`AND`/`OR`/`NOT` on W16-folded CARDINAL** (lines ~1233/1246/1454) are
   illegal on ZType in gm2 → added `BitAnd/BitOr/BitNot` (BITSET `*`/`+`/`-`
   fold, VAL-projected back to LONGINT) and rewrote the operands.
4. **`Compile` error-return params** aligned to `Compiler.def`
   (`errNo`/`errPos`, was `eNo`/`ePos`) — gm2 ISO rejects a disparate name
   in the proper procedure.

The compiler's whole-program 8086-emit, TEXT-equivalent, pastres and
errexit flow are unchanged (mirrors TP3 TPSRC file, ConvertTP3).

## Tests
- `/tmp/tp_iso_mods.sh` two-phase build → `tpshell` 120528B ELF, runs,
  redraws, ESC quits.  `make test` and editor/editor-round-trips covered in
  the earlier TP3-EDITOR-PSEUDOCODE suite.

*Generated: 2026-09-22*