Reference counting and Bacon-Rajan trial deletion are gone from the runtime.
Traced (inferred-gc) objects now die only by the collector; owned values keep
deterministic drops exactly as before.
- wo_hdr: rc retired; borrow and the freed 4 bytes become a union — non-traced
values keep the borrow word, traced objects use the 8 bytes as the intrusive
sweep-list link. Header stays exactly 16 bytes. WHITE is now the all-zero
color (allocations born white by memset); WO_F_BUF retired.
- gc.c rewritten: snapshot-at-beginning tri-color mark-sweep. Roots (frames'
gc+owned masks) shaded atomically at cycle start; Yuasa deletion barrier
shades the OLD target of every gcref edge deleted while marking (SETF
overwrites + every owned-death path, which all funnel through wo_drop_kind's
GCREF case); allocations mid-cycle born black. Mark AND sweep budgeted
(WO_GC_BUDGET objects/slice), sweep resumes via a cursor; gray-worklist OOM
degrades to a blacken-all cycle (frees nothing, never wrong). Owned interiors
walked eagerly (single-owner trees), pruned by a per-class may-gcref bit
computed at rt_init (fixpoint over kinds + v2 field_class/field_elem;
conservative when metadata is absent).
- vm.c: safepoints at NEW (the heap-goal trigger), CALL, and backward JMP;
root scan follows vm_unwind's governing-pc convention. Unwind's gc-mask
branch just nulls the register. RC_INC/RC_DEC are accepted as no-ops until
the emitter stops producing them (next commit) — which also deletes the old
RC_DEC-on-nil trap that broke `?Node` gcref field stores.
- main.c pump: post-exit, a rootless cycle frees everything unreachable in
budgeted slices; the trace line moved into wo_gc_slice (one format for pump
and in-program slices). rt_destroy frees traced remnants (trap paths, tests).
- WO_GC_GOAL joins WO_GC_BUDGET/WO_GC_TRACE as an rt-owned knob (default 256
KiB; a tiny goal forces mid-program cycles for testing).
- tests: test_cycle.c rewritten (abandoned cycle freed, rooted cycle survives,
slices bounded, cycle-through-multi, repeated-cycle leak-freedom, and the
spec's load-bearing DELETION-BARRIER test: an object hidden behind a black
object mid-mark must survive). test_rc.c re-pinned to owned drops + the
owned/traced boundary; test_obj.c asserts tracked-white-linked instead of
rc=1.
Verified: make test + test-iso (all suites, ASan/UBSan; test_cycle 42/0,
test_rc 14/0) + cli_smoke; oop-e2e 79/0 (gc corpus traces unchanged: the new
slice math reproduces steps=1/freed=2 and steps=2/freed=4); employee 8/0;
log-watcher 7/0. THE RING RUNS: docs/examples/gc-cycle prints
`ring a -> b -> c -> a`, is reclaimed post-exit (freed=3 remaining=0), is ASan
clean, and survives an in-program cycle while rooted (WO_GC_GOAL=64: mid-run
slice frees 0, post-exit frees 3).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
shoney.arickathil
e2c825843f