M2compiler-V3/docs/STATUS.md

m2compiler-V3 — status (2026-10-16)

This answers "where are we now?".

Numbers

• Suite 219/219 (compiler/run_tests.sh).
• Self-hosting FIXPOINT OK — stage2 and stage3 images are byte-identical (3,714,376 bytes).
• Corpus 372 / 612 sources compile with 0 errors, 0 crashes (tools/v3-corpus/corpus.sh over the gm2 testsuite); the rest are genuine language gaps or unresolved imports.
• Branch resolve-check; tree clean.

Architecture (current)

per unit:
  Parse   -> AST + declarations; each procedure body is skipped and
             re-parsed at unit end, so forward references bind normally
  Lower   -> walk the AST, emit QBE (the only emitter)
  Emit    -> buffered image, EndModule

• Two-phase parse. Procedure bodies are deferred (module level) and re-parsed after the unit's declarations, which removed the entire forward-reference mechanism (FwdVar*, Design's forward branch). A module body may now call a procedure declared later; a nested-local forward is a plain 201. -notwophase restores the legacy inline parse for debugging.
• No resolve/check pass. The Check module was deleted once it was proven vestigial (gutting it left the emitted .ssa byte-identical): binding is late by construction.
• Lower is the only emitter; the AST is the interface.

Language coverage

Program modules; CONST/VAR/TYPE (scalars, subranges, enums, arrays, records incl. variants, sets, pointers); WITH/IN; whole array/record copy; NEW/DISPOSE; full expressions and control flow; GOTO/labels; procedures (value/VAR params, functions, recursion, FORWARD, nested procedures, procedure values); Clarion-form CLASS (methods, single inheritance, virtual dispatch); PIM coroutines; Unicode (UCHAR/UString, UTF-8 edges); ISO type conversions T(x); separate compilation (FROM/IMPORT, qualified L.x, opaque types); generics (ISO 10514-2 refinement): type/value/procedure parameters, constraints, nested generics, generic classes.

Landed recently (this thread)

• AST + Lower (L0–L7) — Lower emits the whole session from the AST.
• Two-phase parse; forward machinery deleted; Check deleted.
• Generics increment 3: value/procedure parameters, constraint model, nested generics, generic classes via generic modules.
• ISO type conversions T(x) (incl. CONST folding): corpus 365 → 372.
• Clean M2 exit codes (0 ok / 1 errors / 2 usage-IO).
• Bug fixes: PopPos wiping repass diagnostics; global record data size (w 0 → l 0 for pointer/LONGINT/proc fields); template arithmetic over a type formal; proc-typed formals in DEF/IMPL; imported procedures used as values.
• Showcase showcase23 (generic doubly linked list).

What remains

1. Corpus language gaps — top LANG buckets are not supported yet, undeclared identifier, invalid call; separate genuine gaps from missing stdlib imports (LIB), then fix the top bounded one. See docs/analysis_gaps.md.
2. The size-sensitive V3 miscompile — the long-standing "removing ASTDUMP from M2.atg breaks the fixpoint" has never been root-caused. A real correctness landmine.
3. Robustness — fixed table limits resolve silently when exceeded; weak error recovery; error-message polish.
4. Library holes — channel/device framework (docs/wip/).
5. Housekeeping — consolidate docs/summary_*.md (see docs/INDEX.md); decide on merging/pushing resolve-check.

How to check for yourself

cd compiler
./build.sh          # M2.atg -> scanner/parser/driver -> ./M2
./run_tests.sh      # 219/219
cd ..
./bootstrap/fixpoint.sh   # FIXPOINT OK (byte-identical stage2/stage3)