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2 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
 Brummel
|
c5fd16a4eb |
feat(codegen): StrRep loop-carried Str ⇒ Heap, close the #49 recur leak
mir.4 closes bug #49 (a heap-Str loop binder replaced across `recur`
leaks every superseded slab; the loop result leaks too) structurally,
by making every Str a loop binder holds OR a loop returns an owned heap
slab — then deleting the `!is_str` carve-out from BOTH codegen gates
that carried it. The leg-by-leg `!is_str` patches are gone.
Mechanism (the milestone thesis: representation in MIR, codegen reads
it). lower_to_mir sets rep = StrRep::Heap on every Str literal in a
loop-carried position; codegen's MTerm::Str arm promotes a Heap literal
via ailang_str_clone (a fresh ailang_rc_alloc slab, rc_header refcount
1). Three promotion positions, all in the Loop/Recur lowering:
1. binder seed inits (is_str_ty on the binder type);
2. recur args at Str-binder positions (read off the innermost
loop_stack frame);
3. exit-arm tail result literals (promote_tail_str_literals walks the
loop body's tail positions when the loop returns Str).
With every loop-carried Str now owned-heap, both gates lose !is_str:
the recur superseded-value dec (lib.rs) frees each intermediate slab;
the loop-result trackability gate (drop.rs:493) lets the caller's
scope-close free the final slab.
Why both gates, and the planning-time error this corrects. The original
plan/spec scoped the deletion to the recur dec gate only, reasoning the
#49 loop result is "consumed by print". The implement-orchestrator
landed that scope (Tasks 1-2) clean and correctly BLOCKED: it took #49
from live=3 to live=1, the residual being the loop RESULT. I verified
the diagnosis empirically:
- print BORROWS its arg (prelude: `(let s (show x) (do io/print_str
s))`, the eob.1 heap-Str discipline), so `(print s)` does not free
the loop result; the caller's let-binder does, via drop.rs:493.
"consumed by print" != "freed by print" — that was the error.
- Deleting drop.rs:493's !is_str takes #49 and the recur-literal
fixture to live=0.
- Deleting drop.rs:493 WITHOUT exit-arm promotion SIGSEGVs (exit 139)
on a loop returning a static Str literal — hence the third
promotion position and the static-exit witness.
The agent surfaced a real spec defect via an empirical BLOCK rather
than guessing; I corrected the spec refinement note (both gates, three
positions) and completed the loop-result leg inline, the context
already loaded from verifying the BLOCK (CLAUDE.md "already loaded
context" carve-out). drop.rs:493's Str carve-out is now sound to delete.
Boundary (asserted ill-typed, not constructible): a borrowed static-Str
Var seeded/recur'd into a consumed Str loop binder — rejected upstream
by uniqueness (a consumed binder position is owned).
Verification (orchestrator-run): all four leak fixtures reach live=0
under AILANG_RC_STATS — #49 (xyyy), recur-literal (reset), static-exit
(result), and the
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|
Brummel
|
2536b5f535 |
plan(mir.4): StrRep loop-carried Str ⇒ Heap, delete the recur !is_str gate
mir.4 closes bug #49 (a heap-Str loop binder replaced across `recur` leaks every superseded str_concat slab, live=3) structurally rather than with a fourth leg-by-leg patch. Design calls made in planning (folded into the spec as the mir.4 refinement note): - Mechanism: producer-side representation, codegen reads it — the milestone thesis. lower_to_mir sets rep = StrRep::Heap on every MTerm::Str literal that flows into a Str loop-binder alloca (seed inits AND recur args at Str-binder positions); codegen's MTerm::Str arm gains a Heap leg that promotes the static literal via ailang_str_clone (fresh ailang_rc_alloc slab, rc_header refcount 1). No special-casing in the codegen Loop/Recur store arms — the clone is emitted automatically when the Str{Heap} node is lowered. - Recur args are promoted too, not just seeds: `(recur "reset" …)` is well-typed (verified: `ail check` accepts it), and a seed-only promotion would leave a static literal under the now-unconditional dec — a constructible UB hole. Soundness over minimalism on the highest-risk RC/drop surface. - Only the recur dec gate (lib.rs:2231) loses !is_str. The drop.rs loop-RESULT trackability gate (drop.rs:493) STAYS conservative: deleting it needs a broader "every Str a loop can return is owned-heap" guarantee (a static exit-arm literal breaks it) and is not required by the #49 acceptance (the #49 loop result is consumed by print). drop.rs is untouched. - Boundary (out of scope, asserted ill-typed): a borrowed static-Str Var seeded/recur'd into a consumed Str loop binder is rejected upstream by uniqueness (a consumed binder position is owned), so it is not constructible. Plan 0119 carries exact code per step: producer rep promotion + a loop-frame-driven Str-binder mask for recur args (reusing the existing ctx.loop_stack, no new ctx field), the codegen Heap leg, the gate deletion, the #[ignore] lift on the #49 pin, a recur-literal witness fixture + runtime pin proving the recur-arg leg, and the full-suite + ir_snapshot verification. The existing lower_to_mir_ty Static-seed pin flips to assert Heap. |