Safari / Chrome discrepancies lead to problems in instantiateWasm implementation example; Uncatchable exceptions in receiveInstance

[vadimkantorov]

These are two errors of two different modules (compiled under Emscripten 2.0.26):

[Error] Unhandled Promise Rejection: TypeError: undefined is not an object (evaluating 'Module["asm"]["oa"]')
	receiveInstance (busybox_unstripped.js:9:10785)
	promiseReactionJob

[Error] Unhandled Promise Rejection: TypeError: undefined is not an object (evaluating 'Module['asm']['memory']')
	receiveInstance (busytex.js:1734)
	promiseReactionJob

I'm initialising module as:

instantiateWasm(imports, successCallback)
            {
                WebAssembly.instantiate(wasm_module, imports).then(successCallback);
            },

where wasm_module is ArrayBuffer (under Safari).

1. How do I make it work under Safari? :)

2. Also for some reason these Unhandled Promise Rejections do not lead to exceptions. I'm using modularised Emscripten module, so I'm doing try-catch, and await inside try. Would you know why it's not failing with an exception and how to at least handle this gracefully?

[sbc100]

Are you writing you own WebAssembly module loading JS code or are you using the JS generated by emscripten?

Does the same code run in other browsers?

[vadimkantorov]

I'm using the JS generated by Emscripten, and specifying instantiateWasm method, source code: https://busytex.github.io/busybox.js

This same code runs in Chrome without problems

[vadimkantorov]

You can even navigate to https://busytex.github.io and just check Safari's developer console

[sbc100]

I think you might need to make changes to your instantiateWasm override. Do you need to overide it? I would take a look at the receiveInstance callback and see what it is receiving.

It seems like Module["asm"] is probably not assigned correctly so check the first argument is coming through correctly to receiveInstance:

  function receiveInstance(instance, module) {                                      
    var exports = instance.exports;    
    Module['asm'] = exports;   

[vadimkantorov]

I overrode it to support compileStreaming in Chrome which allows overlapped downloading and compiling of large modules (even before exports / imports are provided)

[sbc100]

Do things work in safari if you don't override this method?

[vadimkantorov]

Haven't tried yet. Would you have an advice on how to instantiate Emscripten module from arrayBuffer corresponding to downloaded wasm without overriding this method?

[sbc100]

You should be able to override instantiateWasm just fine.. but it seems that you are not quite doing to correctly today. Take a look at what the receiveInstance function is being called with.. I would guess its not correct.. and I would guess that the problem is how your are overriding instantiateWasm.

[vadimkantorov]

The only docs I found are:

• https://emscripten.org/docs/api_reference/module.html
• https://github.com/emscripten-core/emscripten/blob/main/tests/manual_wasm_instantiate.html#L170

Apart from me forgetting to return {}, my impl seems correct. I'll try with returning {}

[vadimkantorov]

Adding return {} did not help Safari :(

[vadimkantorov]

Okay, using output.instance instead of output helps Safari:

instantiateWasm(imports, successCallback)
 {
    WebAssembly.instantiate(wasm_module, imports).then(output => successCallback(output.instance)).catch(e => {throw new Error('Error while initializing BusyTex!')});
    return {};
}

How just then(successCallback) worked under Chrome? :)

[vadimkantorov]

Hmm, then the second memory error (oa problem is gone) persists (the and there are some dependency loading problems:

Unhandled Promise Rejection: TypeError: undefined is not an object (evaluating 'Module['asm']['memory']')

Another question: how could I catch this exception? catch(e => ...) did not help

/bin/busybox:  ||| Preparing... (0/1)
/bin/busybox:  ||| All downloads complete.
/bin/busybox:  ||| Running...
/bin/busybox:  ||| 
$ man 
/bin/busytex: Preparing... (0/1)
/bin/busytex:  | stderr: still waiting on run dependencies:
/bin/busytex:  | stderr: dependency: wasm-instantiate
/bin/busytex:  | stderr: (end of list)

(many copies of lines like this)

[vadimkantorov]

For dependencies, it somehow fixed itself (after I changed initializeInstance at all places). Now I'm getting the following error:

New compilation started: [README.tex]
Module.data_packages https://busytex.github.io/dist/texlive-basic.js data_packages https://busytex.github.io/dist/texlive-basic.js FIN
$ busytex xetex --no-shell-escape --interaction=nonstopmode --halt-on-error --no-pdf --fmt /xelatex.fmt README.tex
/bin/busytex: xetex | stderr: sigaction: signal type not supported: this is a no-op.
/bin/busytex: xetex | stderr: ReferenceError: Can't find variable: ___sys_statfs64
/bin/busytex: xetex | stderr: 
callMain: abort(ReferenceError: Can't find variable: ___sys_statfs64) at jsStackTrace@https://busytex.github.io/dist/busytex.js:1907:28
stackTrace@https://busytex.github.io/dist/busytex.js:1924:28
abort@https://busytex.github.io/dist/busytex.js:1638:54
___sys_fstatfs64@https://busytex.github.io/dist/busytex.js:6029:74
wasm-stub@[wasm code]
<?>.wasm-function[17532]@[wasm code]
<?>.wasm-function[11021]@[wasm code]
<?>.wasm-function[11019]@[wasm code]
<?>.wasm-function[11018]@[wasm code]
<?>.wasm-function[10642]@[wasm code]
<?>.wasm-function[10640]@[wasm code]
<?>.wasm-function[10819]@[wasm code]
<?>.wasm-function[10688]@[wasm code]
<?>.wasm-function[10686]@[wasm code]
<?>.wasm-function[10868]@[wasm code]
<?>.wasm-function[10869]@[wasm code]
<?>.wasm-function[10662]@[wasm code]
<?>.wasm-function[10661]@[wasm code]
<?>.wasm-function[10870]@[wasm code]
<?>.wasm-function[1654]@[wasm code]
<?>.wasm-function[672]@[wasm code]
<?>.wasm-function[1210]@[wasm code]
<?>.wasm-function[1426]@[wasm code]
<?>.wasm-function[375]@[wasm code]
<?>.wasm-function[380]@[wasm code]
<?>.wasm-function[553]@[wasm code]
<?>.wasm-function[127]@[wasm code]
<?>.wasm-function[565]@[wasm code]
<?>.wasm-function[132]@[wasm code]
<?>.wasm-function[584]@[wasm code]
<?>.wasm-function[17519]@[wasm code]
wasm-stub@[wasm code]
17519@[native code]
https://busytex.github.io/dist/busytex.js:1689:27
NOCLEANUP_callMain@https://busytex.github.io/dist/busytex_pipeline.js:351:21
https://busytex.github.io/dist/busytex_pipeline.js:443:43
asyncFunctionResume@[native code]
[native code]
promiseReactionJobWithoutPromise@[native code]
promiseReactionJob@[native code] (evaluating 'new WebAssembly.RuntimeError(what)')
/bin/busytex: EXIT CODE: undefined
$ busytex xdvipdfmx -o README.pdf README.xdv
/bin/busytex: xdvipdfmx | stderr: 
/bin/busytex: xdvipdfmx | stderr: xdvipdfmx:fatal: Could not open specified DVI (or XDV) file: README.xdv
/bin/busytex: xdvipdfmx | stderr: 
/bin/busytex: xdvipdfmx | stderr: No output PDF file written.
/bin/busytex: xdvipdfmx | stderr: stdio streams had content in them that was not flushed. you should set EXIT_RUNTIME to 1 (see the FAQ), or make sure to emit a newline when you printf etc.
/bin/busytex: xdvipdfmx | stderr: program exited (with status: 1), but EXIT_RUNTIME is not set, so halting execution but not exiting the runtime or preventing further async execution (build with EXIT_RUNTIME=1, if you want a true shutdown)
/bin/busytex: xdvipdfmx | stderr: 
callMain: Program terminated with exit(1)
/bin/busytex: EXIT CODE: 1
Elapsed time: 4.70 sec

[vadimkantorov]

What "works" in Safari (modulo ) does not work in Chrome:

// variant 1. works in Safari, does not work in Chrome
instantiateWasm(imports, successCallback)
 {
    WebAssembly.instantiate(wasm_module, imports).then(output => successCallback(output.instance)).catch(e => {throw new Error('Error while initializing BusyTex!')});
    return {};
}

// variant 2. works in Chrome, does not work in Safari
instantiateWasm(imports, successCallback)
 {
    WebAssembly.instantiate(wasm_module, imports).then(successCallback).catch(e => {throw new Error('Error while initializing BusyTex!')});
    return {};
}

Chrome error in variant (1):

TypeError: Cannot read property 'exports' of undefined
    at receiveInstance (busybox_unstripped.js:9)
    at busybox.js:33

And still this is uncatchable