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Ran build-all.sh with wasm_of_ocaml 6.3.2: output .wasm units came out byte-identical to the Jun-29 backup (same hashes, diff -rq clean), so 6.3.2 still emits legacy 'try'. A plain rebuild is a dead end; the fix needs a newer wasm_of_ocaml (or flag) that emits try_table. No harm done — deployed artifacts unchanged, live SPA intact. apt wabt/wasm2wat can't read these wasm-GC binaries (0x5e); need wasm-tools or a real-browser check. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
43 lines
2.8 KiB
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43 lines
2.8 KiB
Markdown
# Follow-up: WASM kernel uses deprecated `try` exception instruction (+ sync XHR)
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**Found:** 2026-06-30, from a real browser console on `blog.rose-ash.com` (modern Chrome/Firefox).
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**Severity:** not yet breaking — *deprecation warnings*. The SPA still boots (a hard refresh
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cleared a stale cached loader, which was the day's actual symptom). But when browsers **remove**
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the legacy `try` instruction, the WASM kernel will fail to instantiate → "SxKernel not found
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after 5s" → no SPA (server-rendered pages + native-form writes still work; only SPA nav + the
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interactive picker need the kernel).
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## The two warnings
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1. **`WebAssembly exception handling 'try' instruction is deprecated … use 'try_table' instead`**
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(×6). The kernel `shared/static/wasm/sx_browser.bc.wasm.assets/*.wasm` was compiled (Jun-29
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artifact) with the legacy exception-handling encoding. wasm_of_ocaml standardized on
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`try_table`; current toolchain is **6.3.2**.
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2. **`Synchronous XMLHttpRequest on the main thread is deprecated`** — `sx-platform.js:575`,
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`loadManifest()` does `xhr.open("GET", …module-manifest.sx…, false)` (sync). Browsers
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increasingly restrict sync XHR.
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## Fix
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1. **A plain rebuild does NOT fix it — TESTED 2026-06-30, dead end.** Ran
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`bash hosts/ocaml/browser/build-all.sh` with the current `wasm_of_ocaml 6.3.2`. The output
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`.wasm` units came out **byte-identical** to the Jun-29 backup (same content hashes, e.g.
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`dune__exe__Sx_browser-4878f9e1.wasm`; `diff -rq` clean). So 6.3.2 still emits the legacy
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`try` — rebuilding gains nothing. **The fix needs a newer `wasm_of_ocaml` (or a flag) that
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emits `try_table`** — a toolchain *upgrade* (`opam upgrade wasm_of_ocaml-compiler` to a
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version that defaults to `try_table`, or find the relevant `--enable` flag), then rebuild +
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verify. (Disassembly check note: apt's `wasm2wat`/wabt is too old for these wasm-GC binaries —
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`error: unexpected type form (got 0x5e)`; need `wasm-tools` for wasm-GC, or verify in a real
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up-to-date browser. Playwright's older chromium still accepts `try`, so it won't tell you.)
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2. **`loadManifest` → async.** Change to an async fetch and restructure the boot so the manifest
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is awaited before module loading (it's currently consumed synchronously). Contained to
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`hosts/ocaml/browser/sx-platform.js` + its copy in `shared/static/wasm/`.
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## Scope / ownership
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`hosts/ocaml/browser/` is the OCaml→WASM toolchain — generally out of the host loop's lane, though
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the host loop has committed there for the blog SPA (b21ae05e, 689dae7d). A kernel rebuild affects
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the LIVE SPA, so do it when the box is quiet, with real-browser verification, and a quick rollback
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path (the Jun-29 `.assets` are the known-good artifact — keep a copy before overwriting). Not
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urgent; schedule rather than rush.
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