ThaUnknown
commented
1 year ago this is.... unusual?
jassub only uses fetch for engines which support streamed WASM compilation, which REQUIRES fetch in the engine to work, as it uses fetch responses, so if fetch doesnt exist, streamed compilation will never run, and never call fetch, so it's a non-issue?
// hack, we want custom WASM URLs
const _fetch = fetch
const wasm = !WebAssembly.instantiateStreaming && read_(data.wasmUrl, true)
if (WebAssembly.instantiateStreaming) self.fetch = _ => _fetch(data.wasmUrl)
WASM({ wasm }).then(Module => {
_malloc = Module._malloc
// ...fetch is overwritten because emscripten in their infinite wisdom decided to hardcode the wasm url when using instantiateStreaming so this unwraps it, kinda hacky, but it works really good
instantiateStreaming was added way after fetch so even if fetch doesn't exist, it should never cause an error during runtime as fetch itself wont ever be called
from emscripten's compiled code:
WebAssembly.instantiateStreaming?WebAssembly.instantiateStreaming(fetch("hardcodedURL.wasm"),imports):WebAssembly.instantiate(Module["wasm"],imports)so fetch will never run on engines which don't support it, this is already checked by jassub and emscripten
promise also shouldn't need to be polyfilled as Promises are only required when using webassembly which was added after promises and on engines which don't support WASM promises aren't used, instead a fake WASM emulation is used:
try {
const module = new WebAssembly.Module(Uint8Array.of(0x0, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00))
if (!(module instanceof WebAssembly.Module) || !(new WebAssembly.Instance(module) instanceof WebAssembly.Instance)) throw new Error('WASM not supported')
} catch (e) {
console.warn(e)
// load WASM2JS code if WASM is unsupported
eval(read_(data.legacyWasmUrl))
}which fakes the promise.then code with [from emscriptens compiled code]:
var
WebAssembly = {
// Note that we do not use closure quoting (this['buffer'], etc.) on these
// functions, as they are just meant for internal use. In other words, this is
// not a fully general polyfill.
/** @constructor */
Memory: function(opts) {
this.buffer = new ArrayBuffer(opts['initial'] * 65536);
},
Module: function(binary) {
// TODO: use the binary and info somehow - right now the wasm2js output is embedded in
// the main JS
},
/** @constructor */
Instance: function(module, info) {
// TODO: use the module somehow - right now the wasm2js output is embedded in
// the main JS
// This will be replaced by the actual wasm2js code.
this.exports = (
// EMSCRIPTEN_START_ASM
// ...esm2js code
// EMSCRIPTEN_END_ASM
)(info);
},
instantiate: /** @suppress{checkTypes} */ function(binary, info) {
return {
then: function(ok) {
var module = new WebAssembly.Module(binary);
ok({
'instance': new WebAssembly.Instance(module, info)
});
// Emulate a simple WebAssembly.instantiate(..).then(()=>{}).catch(()=>{}) syntax.
return { catch: function() {} };
}
};
},
RuntimeError: Error
};it does however require Promise inside the main thread, which I think is already polyfilled in JF web so it shouldn't be an issue?
dmitrylyzo
Describe The Bug JASSUB doesn't work in legacy browsers: worker fails on webOS 1.2, requiring
fetch,Promise(probably more).Steps To Reproduce
ares-inspect.Expected Behavior No error and see subtitles.
System (please complete the following information):
Additional Context Promise in webOS 2 has a weird implementation, so it also requires testing. JASSUB 1.5.13 works fine, because it was built with compatibility flags (browser version).