# Session 2026-10-23 — range checks + PACKEDSET

> Continued later the same day with ISO exceptions
> (`summary_session-2026-10-23-exceptions.md`) and then multi-dimensional
> open arrays (`summary_session-2026-10-23-open-arrays.md`).

Branch **`master`**.  Continues `summary_session-2026-10-22.md` from the
2026-10-22 stop point (`v3-smallfix`).

## Numbers

| gate | start | end |
| --- | --- | --- |
| suite (`compiler/run_tests.sh`) | 259/259 | **263/263** |
| fixpoint (`bootstrap/fixpoint.sh`) | OK (4,028,447 B) | **OK (4,075,853 B)** |
| corpus (`tools/v3-corpus/corpus.sh`) | 511/612 | **511/612, 0 crashes** |

## What landed

### `PACKEDSET` — `SymTab` + `QbeGen` + `Lower` + grammar

ISO `PACKEDSET OF <ordinal>` is implemented for spans up to 32 bits:
1/2/4-byte storage (`SIZE` is the packed width), `ORD` is the mask,
and `INCL`/`EXCL`/`IN`, assignment, set operations, packed array/record
elements and value/VAR parameters all work.  Wider spans 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
correctly.  Corpus stays 511.

### Runtime subrange range checks — `Lower` + `QbeGen.CheckRange`

V3 accepted base-typed values into CHAR/enum subranges but emitted no
runtime check.  `Lower.CheckSub` now traps (abort) when the value is
outside the destination subrange on:

- assignment (scalar, field or array element);
- a value actual whose formal is a subrange;
- `RETURN` whose function result is a subrange;
- `INC`/`DEC` on a subrange.

The **post-increment of a `FOR` control variable is exempt**: the final
successor of a loop over a full subrange (`FOR x := 0 TO 3` with
`x: [0..3]`) may legitimately exceed the upper bound.  `LONGINT`
subranges are not checked yet.

Regressions: `t_trap_range` (assignment), `t_trap_range_arg` (actual),
`t_trap_range_ret` (`RETURN`); `t_subrange` remains the in-range case.

## Commits

| commit | tag | work |
| --- | --- | --- |
| `54d84b9` | `v3-rangechecks` | runtime subrange range checks (+3 trap tests) |
| `6b2df4c` | `v3-packedset` | PACKEDSET 1/2/4-byte storage |

## Remaining

See `docs/handoff-2026-10-23-next.md`.  The next candidates are ISO
exceptions (dedicated session), multi-dimensional open arrays (ABI
decision), and the library-folder / separate-compilation plans (both
deferred).