Closes Gitea #4. Removes the Boehm-Demers-Weiser conservative GC
backend wholesale across six layers in one atomic iteration. After
this iter, `AllocStrategy` has two variants (`Rc`, `Bump`),
`--alloc=gc` is rejected at CLI parse with `unknown --alloc value`,
the libgc link arm is gone, and the design ledger describes RC
(canonical) + bump (raw-alloc bench-floor) as the only allocators.
Layer-by-layer summary:
CLI surface — `crates/ail/src/main.rs`:
`parse_alloc_strategy` arm `"gc" => Ok(AllocStrategy::Gc)`
removed; error wording updated to `(expected `rc` or `bump`)`;
clap-derive `value_parser = ["gc","bump","rc"]` allowlist on
BOTH `Build` and `Run` subcommands DROPPED so that
`parse_alloc_strategy` remains the sole gatekeeper for the
unknown-value diagnostic (otherwise clap shadows the runtime
diagnostic with `invalid value 'gc' for '--alloc'`, which would
miss the milestone-pin's stderr substring check). The
`default_value = "rc"` stays.
Codegen — `crates/ailang-codegen/src/lib.rs`:
`AllocStrategy::Gc` variant + `Default` derive removed (no
caller of `AllocStrategy::default()` existed in the workspace,
so the trait derivation was dead). `fn_name` (spec called it
`runtime_alloc_fn` loosely; actual identifier is `fn_name`)
drops the `Gc => "GC_malloc"` arm. `lower_workspace` and
`lower_workspace_staticlib` defaults flip from `Gc` to `Rc`.
In-source negative-complement codegen test (mod tests, lib.rs:3571ff)
retargets from `AllocStrategy::Gc` to `AllocStrategy::Bump`
(bump also doesn't emit per-type drop fns; the test's semantic
"no drop fns under non-RC" is preserved).
Link branch — `crates/ail/src/main.rs:2389ff`:
The `match strategy { AllocStrategy::Gc => { ... cmd.arg("-lgc"); ... } }`
arm and its libgc-link block are entirely gone. The surviving
match exhausts on `Bump` and `Rc` (Rust's exhaustiveness check
confirms; no `error[E0004]`). Staticlib-guard diagnostic
rewritten to drop the "shared Boehm collector" phrasing while
preserving the prefix `staticlib (swarm) artefact is RC-only`
verbatim (the surviving `staticlib_bump_is_rejected` test
depends on that substring).
Test suite — 3 pure-differential e2e tests deleted
(`gc_handles_recursive_list_construction`,
`alloc_rc_produces_same_stdout_as_gc`,
`alloc_rc_matches_gc_on_std_list_demo`); 9 RC-feature tests
stripped of their `stdout_gc` build call and differential
`assert_eq!(stdout_gc, stdout_rc, ...)` (absolute
`assert_eq!(stdout_rc.trim(), "<n>")` pin retained as
correctness oracle); `staticlib_gc_is_rejected` deleted; new
milestone-pin `crates/ail/tests/boehm_retirement_pin.rs`
asserts `ail build --alloc=gc` exits ≠ 0 with stderr containing
`unknown --alloc value` and `\`gc\``; `examples/gc_stress.ail`
fixture deleted (no remaining references).
Implementer expansion (not in plan): `iter17a_local_box_alloca`
(in `e2e.rs`) carried an IR-shape assertion against
`@GC_malloc`-absence as the witness for non-escaping
allocation. After the Task-2 codegen default flip, the witness
shifts to `@ailang_rc_alloc`-absence in escape-targeted
positions; assertion + doc-comment updated. Property
protected ("no heap allocation in non-escaping contexts") is
unchanged; only the named allocator shifts.
Bench harness — `bench/run.sh` 9→6 column compaction
(workload + bump(s) + rc(s) + rc/bump + bump RSS + rc RSS);
gc-arm `bench_latency_implicit_gc` build call + harness
invocation dropped from latency block; header comment reframed
from "GC-overhead bench harness" to "RC-overhead bench
harness"; "Decision 10's Boehm-retirement target (1.3x)"
rewording to "RC-overhead-vs-bump bench-health regression gate".
`bench/check.py:62` header-sentinel changes from
`"gc(s)" in line` to `"bump(s)" in line`; column-count check
at `:72` flips from `!= 9` to `!= 6`; per-workload field set
drops `gc_s`/`gc_over_bump`/`gc_rss_kb`; `ARM_LABEL_TO_KEY`
drops the `"implicit @ gc": "implicit_at_gc"` entry.
`bench/baseline.json` regenerated via `--update-baseline`.
Implementer note (planner-defect): `write_new_baseline`
iterated over the *existing* baseline's metric list when
emitting the regenerated file, so even after parser-level
`gc_*` removal, the fallback emitted them back into the JSON.
Scrubbed post-update; the cleaner fix (have
`write_new_baseline` emit only keys present in
`parsed_throughput[workload]`) is a follow-up if the script
becomes load-bearing for further allocator changes.
Design ledger — `design/models/rc-uniqueness.md` excises the
`## Dual allocator — RC canonical, Boehm parity oracle`
section and the `Boehm-Demers-Weiser conservative GC` choice
block + rationale + trade-offs; the per-fn-alloca section
generalises Boehm-specific language to allocator-agnostic;
the memory-model section's `## Choice.` paragraph reframes the
1.3× target from "Boehm-retirement gate" to "bench-health
regression gate".
`design/models/pipeline.md` drops the `--alloc=gc → links libgc`
arm of the pipeline diagram and replaces it with
`--alloc=bump → links bump-floor`; the accompanying prose
rewrites accordingly.
`design/contracts/scope-boundaries.md` rewrites the
"Memory management via Boehm conservative GC" bullet to
describe RC + per-fn-arena present-tense; the dead reference
to `examples/gc_stress.ail.json` (file never existed; the
fixture only ever had a `.ail` form, deleted by this iter) is
dropped along with the `examples/std_list_stress.ail.json`
reference whose purpose was Boehm-only soak testing.
`:67`'s `@printf` / `@GC_malloc` parenthetical updated.
`design/contracts/memory-model.md:232` drops the
"leaks like the pre-Boehm era" phrase; the RC inc/dec
instrumentation is wired up, so the "until then" conditional
that referenced pre-Boehm is closed.
`design/contracts/embedding-abi.md:42-44` rewrites the
staticlib-guard prose to drop the `--alloc=gc` clause (gc is
now a CLI-parser-level unknown-value, not a staticlib-guard
rejection) and reframe the swarm-safety justification around
`--alloc=bump` (leak-only bench instrument) rather than the
historical Boehm collector.
Honesty pin — `crates/ailang-core/tests/docs_honesty_pin.rs`
inverts the polarity: the present-tense Boehm-anchor assertion
on `pipeline.md` (`:116-117`) is deleted, and four
absence-pins are added to `design_md_has_no_wunschdenken`
against the Boehm-zombie strings `transitional Boehm`,
`parity oracle`, `GC_malloc`, `libgc`. The
`design_corpus()` already includes `rc-uniqueness.md` so no
path-list change was needed for the new pins to scan.
`crates/ailang-core/tests/design_index_pin.rs:166` drops the
`"pre-Boehm"` token from the protected-exception comment list
(the phrase no longer appears in `memory-model.md` after this
iter, so the exception is dead).
Runtime docs — `runtime/bump.c`, `runtime/rc.c`, `runtime/str.c`
header comments scrubbed of Boehm/`GC_malloc`/`libgc`
references. `bump.c`'s function signature description still
documents `void *bump_malloc(size_t)` as the bench-floor
allocator interface, but no longer cross-references libgc.
Example fixtures — `examples/bench_latency_implicit.ail`,
`bench_latency_explicit.ail`, `escape_local_demo.ail`,
`reuse_as_demo.ail`, `rc_pin_recurse_implicit.ail` doc-comment
headers scrubbed of `--alloc=gc` / Boehm references. The
`.ail` surface (AST) is untouched in every case; round-trip
invariant holds (`cargo test -p ailang-surface --test round_trip`
green).
Skill / agent prompts — `skills/audit/agents/ailang-bencher.md`
rewritten to use an RC-vs-bump worked example pattern for the
hypothesis-driven bench tutorial, replacing the recurring
"RC vs Boehm under heap pressure" example.
`skills/implement/agents/ailang-implementer.md` Decision-10 /
Boehm references replaced with present-tense RC-commitment
framing.
IR snapshots — the 5 checked-in snapshots
(`crates/ail/tests/snapshots/{hello,list,max3,sum,ws_main}.ll`)
regenerated via `UPDATE_SNAPSHOTS=1 cargo test -p ail --test
ir_snapshot`. Each previously contained
`declare ptr @GC_malloc(i64)` and (for `list.ll`) a `call ptr
@GC_malloc(...)` invocation; post-flip the snapshots contain
`declare ptr @ailang_rc_alloc(i64)` plus the rc inc/dec runtime
declarations.
Spec-vs-acceptance addendum (caught at orchestrator end-report,
absorbed here rather than in a follow-up spec edit): spec §6
acceptance criteria said "Boehm-grep returns matches ONLY in
docs_honesty_pin.rs". The plan itself prescribed historical Boehm
references in 3 additional files: (a) the new milestone-pin
`boehm_retirement_pin.rs` (must literally invoke `--alloc=gc` to
assert its rejection), (b) `embed_staticlib_alloc_guard.rs` file
doc-comment historical note ("`--alloc=gc` no longer exists as a
CLI value"), (c) `embedding-abi.md:44-45` contract historical
clause ("see the Boehm-retirement iter"). All three are
prescribed; the spec's grep wording was too narrow. The four
absence-pins in `docs_honesty_pin.rs` catch the actual zombies
(Boehm-narrative re-emerging in the design ledger), which is the
substantive intent the spec was aiming at — the four extra
documented-by-design exceptions are the cost of having an
explicit milestone-pin and contract-level historical anchors.
Net delta:
- 32 files modified, 2 new (boehm_retirement_pin.rs + stats),
1 deleted (gc_stress.ail);
- workspace tests: every binary `0 failed`. Pass-count delta:
-3 net (4 e2e tests deleted, 1 new milestone-pin test added);
- boehm-grep state: hits only in the four by-design exceptions
documented above;
- `bench/check.py` exit 0 against regenerated baseline;
- CLI must-fail fixture: `ail build --alloc=gc examples/hello.ail`
exits non-zero with stderr containing `unknown --alloc value`
and `\`gc\``;
- design ledger present-tense honest (Boehm-narrative gone from
`rc-uniqueness.md` + `pipeline.md`; the few historical
references in `embedding-abi.md` / `boehm_retirement_pin.rs` /
`embed_staticlib_alloc_guard.rs` are explicit milestone-pins
or contract anchors, not silent ledger residue).
Bench measurement variance noted: closure-chain and hof-pipeline
are ±1-5% jittery between runs; one regeneration flagged 2
metrics as `regressed` before a second run returned 0. The
captured baseline is within self-comparison range. Existing
per-metric tolerances absorb the jitter.
Stats file:
`bench/orchestrator-stats/2026-05-20-iter-boehm-retirement.1.json`.
closes#4
Brummel
14a91f0ae5