Web: Bloom WASM functions trap with 'unreachable' after FFI bridge fix (#73)

[babang1da]

Bug Summary

After PR #73 fixed the FFI bridge (bloom_glue.js + build.sh splicing), the game WASM now loads and bootPerryWasm is correctly gated on __bloomReady. The FFI imports (412 bloom_* functions) are registered.

However, the game crashes immediately with WASM Error: unreachable — a WebAssembly trap inside Bloom's WASM functions.

Reproduction

git clone https://github.com/Bloom-Engine/engine.git
cd engine
git submodule update --init --recursive
./native/web/build.sh examples/pong/main.ts
cd dist/web && python3 -m http.server 8080
# Open http://localhost:8080 → "WASM Error: unreachable"

What works

• bloom_glue.js loads Bloom WASM, sets __ffiImports (412 functions)
• window.__bloomReady Promise resolves
• bootPerryWasm is gated correctly (waits for __bloomReady)
• Perry runtime wrapFfiForI64 wraps FFI namespace with NaN-boxing decode
• Perry WASM instantiates successfully
• Native Linux build works (23.4MB binary, runs with X11 display)

What fails

• instance.exports._start() traps with unreachable
• The trap occurs when Perry's game calls Bloom FFI functions (e.g. bloom_init_window, bloom_set_target_fps, bloom_clear_background)

Environment

• Bloom Engine: commit 71fedc9 (PR fix(web): integrate compiled game WASM into the web build (#72) #73 merged)
• Perry: v0.5.1182 (latest from npm)
• Rust 1.96.0, wasm-pack 0.15.0
• Browser: Chromium (headless)
• OS: Debian 13 (Linux x86_64)

Analysis

The unreachable trap suggests Bloom's WASM hits a core::panicked or unreachable!() macro. Likely causes:

1. WebGPU/WGPU initialization failure — bloom_init_window may panic if WebGPU adapter is not available (headless browser / no GPU)
2. Canvas not properly attached — bloom_attach_native may expect a canvas element that isn't ready
3. wgpu web backend — the WASM target may need wgpu web features enabled that aren't compiled in

Expected behavior

The Pong example (or any Bloom game) should render in the browser after build.sh + python3 -m http.server.

Related

• Web build: bloom_glue.js bootBloomGame() doesn't load game.wasm — FFI bridge incomplete #72 — original FFI bridge bug (fixed by fix(web): integrate compiled game WASM into the web build (#72) #73)
• fix(web): integrate compiled game WASM into the web build (#72) #73 — FFI bridge fix (this bug persists after that fix)