Next session — plan (from 2026-10-23)

Branch: master. Feature state: v3-exceptions + v3-ptrchain + v3-function-exception. Gates: suite 278/278, fixpoint OK (4,156,434 bytes), corpus 512/612, 0 crashes.

Read first: docs/STATUS.md, docs/features.md, docs/gaps/README.md, docs/summary_session-2026-10-23-exceptions.md.

Policy reminder

V3 follows PIM/ISO Modula-2, not gm2 leniencies. Declaration before use is required for data; only a POINTER's base may forward-reference. gm2 compatibility is accepted only where documented in docs/gaps/.

1. `PACKEDSET` — done (spans ≤ 32 bits)

Implemented 2026-10-23: 1/2/4-byte storage, SIZE/ORD, INCL/EXCL/ IN, assignment, set operations, packed arrays/records/parameters. Wider packed sets are a loud 230 implementation limit. Regression t_packedset.

The corpus files onebyte, onebyte2, onebyte3 still do not compile, but the blocker is earlier: they use the module variable r inside assert before its declaration (declaration order, rejected by policy). With r moved before the procedure they compile and run. Do not relax declaration order for this corpus case.

2. ISO exceptions — done (`v3-exceptions`)

A dedicated feature session, not a small fix. The design is in docs/design-exceptions.md (grammar/AST, handler stack, sigsetjmp/ siglongjmp codegen, EXCEPTIONS/M2EXCEPTION, trap mapping, tests).

M1 parser/AST — done (2026-10-23). EXCEPT/RETRY are reserved words; bodies carry NkExcept/NkRetry; RETRY outside a handler is error 237.

M2 runtime/codegen — done (2026-10-23). Handler stack + saved state, m2_exc_push/leave/retry/raise, sigsetjmp dispatch, EmitRet pops, m2_exc_init in main, SYSTEM.THROW, and basic SIGSEGV/SIGFPE mapping. Positive tests: t_except_parse, t_except_throw, t_except_retry, t_except_return, t_except_nested, t_except_module, t_except_signal; negative t_retry_bad (237).

M3 libraries — done (2026-10-23). SysExceptions, EXCEPTIONS and M2EXCEPTION are implemented in runtime/syslib/SysExceptions.* and stdlib/{exceptions,m2exception}.*. t_except_lib covers RAISE, CurrentNumber, GetMessage, IsCurrentSource, IsExceptionalExecution, wrong-source exException, and M2Exception after SYSTEM.THROW.

M4 language traps — done (2026-10-23). TrapCode, CheckIndex vs CheckRange, CASE caseSelectException, and unhandled-exception abort (rc 134). Tests: t_except_trap, t_except_case, t_except_unhandled.

M5 finalization — done (2026-10-23). Session summary summary_session-2026-10-23-exceptions.md; feature tag v3-exceptions at 02b3763, session-end tag at the docs commit. Optional follow-ups: FINALLY, coroutine/protection exceptions.

Corpus reality: lazyunique now compiles and runs (rc=0, unique output 0, 2, 1) after the pointer-chain follow-up; the corpus count stays 512 because it was already compile-OK. Regression t_ptrchain covers the self-referential record layout and p^.next^.value path. except2/4/5/7/8/9 still fail declaration order because ip is declared after the procedures, like onebyte*; keep moved-ip copies as semantic tests but do not count them in the corpus until the policy changes.

3. Multi-dimensional open arrays — 8 files

unbounded, unbounded2/3/4/6/8, array9, adrunbounded3. Do not just accept them: V3 uses a descriptor per level; gm2 passes a flat block with strides, and the corpus checks ADR(m) = ADR(m[0]) and flat SIZE. Decide on an ABI (flat/strided descriptor) before implementing; otherwise leave parked. unbounded5 is a declaration-order case, not this feature.

4. Runtime range checks — done, follow-ups

Lower.CheckSub covers assignment, value actuals, RETURN and INC/DEC; the FOR final increment is exempt. Possible follow-ups:

LONGINT/CARDINAL subranges (currently skipped);
FOR control variables (decide whether to range-check the initial bound only, as now);
trap tests for CHAR/enum subranges (currently integer).

5. Library folders / separate compilation — deferred plans

docs/plan-separate-compilation.md — stable symbols, per-unit objects, init order, linker; and the appendix on dialect folders.
Library-folder layout (lib/pim, lib/iso, lib/m2r10, shared runtime/syslib) is a low-risk build change, to do after the compiler language work; no need to mix dialects in one session.

6. Corpus leftovers (classify first)

ptrarray3 (open-array actual), unbounded7 (2-D actual for ARRAY OF BYTE), adraddress (ADDRESS/pointer compare), proc / shift3 / shift4 (decl-order), constprocedure/constvec3/ conststrarray (mostly ordered decls). Park gm2 extensions, wide sets (settest1/3) and CHAR.mod as before.

Gates for every step

cd compiler && ./build.sh && ./run_tests.sh          # 278/278
cd .. && TMP="$PWD/.scratch/fixpoint" ./bootstrap/fixpoint.sh
tools/v3-corpus/corpus.sh                            # 512 OK, 0 crash

Update STATUS.md, features.md, gaps/, the comparison table and a session summary; commit with a v3-* tag. Do not push without asking.

Resume

cd .../m2compiler-V3
git checkout master
cd compiler && ./build.sh && ./run_tests.sh          # 278/278
cd .. && TMP="$PWD/.scratch/fixpoint" ./bootstrap/fixpoint.sh
tools/v3-corpus/corpus.sh                            # 512 OK, 0 crash

Recommendation: take the multi-dimensional open-array ABI decision, or start the separate-compilation/library-folder work. Library folders and separate compilation remain deferred (docs/plan-separate-compilation.md).

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