russell@unturf.com
88c4b05032
Three coupled changes that unblock the ecdsa quantum-circuit simulator's run on the C tier from neoblanka. 1. c/Makefile autodetects libgc-dev — if /usr/include/gc.h is present, the build links Boehm and defines USE_BOEHM_GC. Without GC, ul_free is a no-op (lumbda.h:35) and every allocation leaks; small REPL snippets work but workloads with thousands of envs OOM the process. Override with USE_GC=0 to force the malloc-only path for diagnostics. 2. c/main.c calls GC_INIT before init_symbols, then GC_disable. GC_INIT registers the stack base for conservative scan — without it some Linux configs miss roots. GC_disable is a deliberate stopgap: lumbda Values are NaN-boxed pointers that conservative Boehm cannot recognize as pointers, so live targets get reclaimed (env binding symbol payloads, SymbolEntry strings) and lookups fail with "undefined: <sym>". Reproducing this without GC_disable on the GC build: any sim.lsp call chain triggers the corruption after ~100 named-let iterations. Until tracing is precise, growing the heap is safer than wrong results. Long-running workloads run under ulimit -v. 3. c/builtins.c gains rename-file and delete-file matching the Python tier (lumbda.py:3468). sim.lsp's write-portal! pattern (write to .tmp, rename) needs rename-file to land cross-tier identical results. 4. tests/regression-named-let-leak.lsp + .sh pin four shapes that blew up ecdsa: the c/TODO-named-let-bytecode.md repro, the F1 shape from foxhop.net's lumbda-c-tier-leak-SP.md (12-line minimum), a 200-iter scaled variant, and a sim.lsp run-ops! mirror. Wired into root Makefile as regression-named-let-leak; added to test-all. Wrapper caps memory at 256 MB virt and 15s per tier so a leak regression fails the run instead of consuming host RAM. Known limits: - --fast JIT still has the named-let + inner user-fn call hang (separate TODO; tree-walker handles this fine). - GC_disable means the heap grows; workloads must bound their work budget. ecdsa's sim runs comfortably in 5 MB. Verified inside a 2G/2vCPU QEMU guest (foxhop.net ecdsa/vm-runner.sh): - test-c (tree-walker) — 35/35 PASS - bench-c (tree-walker) — score 18 matches Python tier byte-identical - F1 probe (tree-walker) — all four steps PASS
83 lines
2.8 KiB
Text
83 lines
2.8 KiB
Text
;;; regression-named-let-leak.lsp
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;;;
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;;; Pins two leak shapes that crashed neoblanka on 2026-06-03 when
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;;; ecdsa/lumbda/main.lsp ran through ~/git/lumbda/c/lumbda --fast.
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;;;
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;;; Both shapes share the same root cause: lumbda C tier shipped
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;;; without Boehm GC linked, so ul_free was a no-op and every env,
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;;; vstack data buffer, and closure leaked. The named-let + inner
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;;; user-fn call pattern allocates fast enough to hit kernel oom-killer
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;;; in seconds.
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;;;
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;;; Wrapper at tests/regression-named-let-leak.sh runs this under
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;;; ulimit -v + timeout so a memory regression fails the run instead
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;;; of consuming all RAM.
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(define *pass* 0)
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(define *fail* 0)
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(define (assert-equal name got expected)
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(if (equal? got expected)
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(begin (set! *pass* (+ *pass* 1))
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(display "PASS: ") (display name) (newline))
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(begin (set! *fail* (+ *fail* 1))
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(display "FAIL: ") (display name)
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(display " got=") (write got)
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(display " expected=") (write expected) (newline))))
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;;; ── Shape 1 — c/TODO-named-let-bytecode.md reproducer ─────────
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(define (maybe x) (if (> x 3) #f (+ x 1)))
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(define (g start)
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(let loop ((t start))
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(let ((next (maybe t)))
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(if next (loop next) t))))
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(assert-equal "named-let + inner let + if-tail-call" (g 0) 4)
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;;; ── Shape 2 — F1 from ecdsa/docs/lumbda-c-tier-leak-SP.md ────
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(define (always-true) #t)
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(define (walk1 ops)
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(let loop ((rest ops))
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(if (null? rest)
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#t
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(if (always-true)
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(loop (cdr rest))
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#f))))
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(assert-equal "named-let + inner user-fn call per iter (3-list)"
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(walk1 (list 'a 'b 'c)) #t)
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;;; ── Shape 3 — same shape, larger N, hits leak harder if present ──
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(define (count-down n)
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(let loop ((i n) (sum 0))
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(if (= i 0)
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sum
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(if (always-true)
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(loop (- i 1) (+ sum 1))
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sum))))
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(assert-equal "named-let + inner user-fn call, 200-iter" (count-down 200) 200)
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;;; ── Shape 4 — emulates ecdsa run-ops! shape on a small list ──
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(define state-vec (vector 0 0 0 0 0 0 'running))
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(define (st-status v) (vector-ref v 6))
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(define (st-ok? v) (eq? (st-status v) 'running))
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(define (exec-noop v op) v)
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(define (run-ops! v ops)
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(let loop ((rest ops))
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(cond
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((null? rest) #t)
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((not (st-ok? v)) #f)
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(else
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(exec-noop v (car rest))
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(loop (cdr rest))))))
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(assert-equal "named-let + cond + inner-fn calls (run-ops! shape)"
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(run-ops! state-vec (list 'x 'cx 'ccx 'x 'cx)) #t)
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;;; ── Summary ───────────────────────────────────────────────────
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(newline)
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(display "regression-named-let-leak: pass=") (display *pass*)
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(display " fail=") (display *fail*) (newline)
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(if (> *fail* 0) (exit 1) (exit 0))
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