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Real browser console on blog.rose-ash.com shows the WASM kernel (Jun-29 artifact, built with an older wasm_of_ocaml) emits the legacy 'try' exception instruction (deprecated; use try_table) + loadManifest does a sync XHR. Not breaking yet (SPA boots; the day's symptom was a stale cached loader, cleared by hard refresh) but will break when browsers drop 'try'. Fix = rebuild the kernel with the current 6.3.2 toolchain (may emit try_table) + verify in a real browser + make loadManifest async. hosts/ocaml/browser toolchain; schedule when the box is quiet with a rollback path, don't rush. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
41 lines
2.5 KiB
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41 lines
2.5 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. **Rebuild the kernel with the current toolchain.** `bash hosts/ocaml/browser/build-all.sh`
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(dune builds `browser/sx_browser.bc.wasm.js`), then `bundle.sh` syncs to
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`shared/static/wasm/`. Modern wasm_of_ocaml 6.x *may* emit `try_table` by default → a fresh
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rebuild alone could fix #1. **Verify:** disassemble a `.wasm` unit (`wasm-tools print` / grep
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for `try_table` vs `try`), then boot it in a REAL up-to-date browser (not just the older
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Playwright chromium, which still accepts `try`) and confirm no deprecation warning + SxKernel
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registers. If 6.3.2 still emits legacy `try`, check for a wasm_of_ocaml flag or bump the
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compiler.
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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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