wasmMemory.buffer instanceof SharedArrayBuffer === false occasionally

[sxzz]

Reproduction:

• Open https://rolldown-browser.vercel.app/
• Typing some code without interruption

Source code: https://github.com/sxzz/rolldown-browser (cannot build locally)

index-DAfNCrBY.js:42708 Error: Build failed with 1 error:

TypeError: Failed to execute 'decode' on 'TextDecoder': The provided ArrayBufferView value must not be shared.
TypeError: The provided ArrayBufferView value must not be shared.
    at Object.UTF8ToString (index-DAfNCrBY.js:9305:49)

Screen.Recording.2025-04-15.at.11.33.22.mov

/cc @Brooooooklyn

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Can we check buffer byusing HEAPU8.buffer[Symbol.toStringTag] === 'SharedArrayBuffer'?

[toyobayashi]

Figured out:

1. From the beginning there is no problem until the wasm memory get grow.

2. When WebAssembly.Memory get grow, v8 will recreated an internal SharedArrayBuffer (but not the same reference to globalThis.SharedArrayBuffer) for WebAssembly.prototype.buffer getter to access, which causes the HEAPU8.buffer instanceof ShardArrayBuffer evaluated to false.

3. Very stupid mistake in emnapi:

   Object.prototype.toString.call(HEAPU8.buffer.constructor) === "[object SharedArrayBuffer]"

   This is always "[object Function]", the .constructor is redundant. I have tried that even HEAPU8.buffer is changed to internal SharedArrayBuffer Object.prototype.toString.call(HEAPU8.buffer) can gets the correct result.