Brummel
e8c6e99a87
Iter B (Own-param dec at fn return) gates on param_modes[i] ==
ParamMode::Own and skips Implicit/Borrow because those modes carry
no caller-handed-off-ownership signal. Iter A (arm-close pattern-
binder dec) is the same shape — pattern-binders loaded out of a
scrutinee owe their drop-validity to the scrutinee's ownership —
but Iter A had no such gate and fired on every ptr-typed binder
with consume_count == 0.
Concrete failure (regression test): pin (params t) is Implicit,
caller loop holds t and re-passes it to itself. pin's (TNode v l r)
arm dec'd l and r, fragmenting the tree the caller still references.
Next recursion tripped ailang_rc_dec underflow.
Fix: thread current_param_modes onto the emitter, set it in
emit_fn from the fn type's param_modes (and reset/save it across
lambda thunk emission). In lower_match, derive scrutinee_is_owned
from the scrutinee's mode (Own only; let-binders and temps are
treated as owned) and skip Iter A when not owned.
Carve-out: a let-alias of a non-Own param is not yet detected;
the regression doesn't trigger it and a propagation pass belongs
in its own iter. Recorded in JOURNAL.
Red: alloc_rc_pattern_bind_in_implicit_fn_does_not_dec_borrowed_children.
Pre-fix the rc binary aborted with refcount underflow; post-fix
matches alloc=gc ("0").
56 lines
1.6 KiB
Plaintext
56 lines
1.6 KiB
Plaintext
; Iter 18d.4 regression fixture: under --alloc=rc, codegen's
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; "pattern-binder dec at arm close" (Iter A) was firing on
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; pattern-bound pointer fields whose enclosing fn is Implicit-
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; mode. Result: a free of memory the caller still references.
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;
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; Symptom under --alloc=rc before the fix:
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; - Implicit-mode pin/loop: refcount underflow at runtime.
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; - Same code under --alloc=gc: clean exit, prints `0`.
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;
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; Pattern shape: a heap-allocated value `t` shared between a
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; callee that pattern-destructures it (pin) and a recursive
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; call that re-passes it (loop). Pattern arm binds the children
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; (l, r) without consuming them — pre-fix, codegen emitted a
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; drop on each, freeing memory still referenced via the outer
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; let-binder `t`.
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(module rc_pin_recurse_implicit
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(data Tree
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(ctor TLeaf)
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(ctor TNode (con Int) (con Tree) (con Tree)))
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(fn build
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(type (fn-type (params (con Int)) (ret (con Tree))))
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(params d)
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(body
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(if (app == d 0)
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(term-ctor Tree TLeaf)
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(term-ctor Tree TNode 1
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(app build (app - d 1))
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(app build (app - d 1))))))
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(fn pin
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(type (fn-type (params (con Tree)) (ret (con Int))))
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(params t)
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(body
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(match t
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(case (pat-ctor TLeaf) 0)
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(case (pat-ctor TNode v l r) 1))))
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(fn loop
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(type (fn-type (params (con Int) (con Tree)) (ret (con Int))))
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(params n t)
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(body
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(if (app == n 0)
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0
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(let _v (app pin t)
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(app loop (app - n 1) t)))))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(let t (app build 2)
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(do io/print_int (app loop 3 t))))))
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