[QUESTION] "Link" Emscripten JS Runtime via WASM standard API

[Tianqi Chen]

Dear Developers:

https://v8.dev/blog/emscripten-standalone-wasm provides an excellent description about how to compile a stand-alone WASM via emcc.

However, in the case of the syscalls still needs emscripten defined files, we will still need an emscripten generated file, and that means

we will need to interact with the WASM via the emscripten Javascript wrapper, e.g. Module.wrap, and call

Recently we start to look into directly build our js interface on top of the WASM js API.

I am wondering if it is possible to directly interact with the wasm module generated by emscripten via the standard WASM js interface,

but still make these additional emscripten syscalls available.

In particular, I am looking for something like

emcc -O3 mylib.c -o mylib.js -s STANDALONE_WASM

Then

const binary = require('fs').readFileSync('mylib.wasm');

// this line ontains the emscripten defined syscalls as a imports 

// that can be passed to the WebAssembly interface.

imports_with_emscripten_sycalls = getEnv("mylib.js");

WebAssembly.instantiate(binary, imports_with_emscripten_sycalls);

Thank you!

TQ

[Sam Clegg]

No, this is currently not possible.  I think it would be cool feature though.   I'm not sure how much work it would be to modify the generated JS to work in this way.  I'm guessing a fair amount..

 

Thank you!

TQ

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[Tianqi Chen]

I see. I wonder if it is possible to get some middle ground.

// mod is emscripten module 

mod =Module;

wasmInstance = mod.wasmInstance;

wasmMemory = wasmInstance.exports.memory

// Directly interact with wasmInstance

// using the WebAssembly API

// syscall callbacks can trap into emscripten module 

TQ 

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[Sam Clegg]

On Sat, Apr 25, 2020 at 10:51 PM Tianqi Chen <tqc...@cs.washington.edu> wrote:

I see. I wonder if it is possible to get some middle ground.

// mod is emscripten module 

mod =Module;

wasmInstance = mod.wasmInstance;

wasmMemory = wasmInstance.exports.memory

// Directly interact with wasmInstance

// using the WebAssembly API

// syscall callbacks can trap into emscripten module 

I think that should work yes.  I don't see anything stopping you doing that today.  

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