Where is the wasmOffsetData come from?

[junyuecao]

I was trying to run asan builds with pthreads and custom instantiateWasm.
I don't see any demo or test case that shows how to construct this data.

emscripten/src/preamble.js

Lines 1092 to 1101 in 0538c9d

	if (Module['instantiateWasm']) {
	#if USE_OFFSET_CONVERTER && PTHREADS
	if (ENVIRONMENT_IS_PTHREAD) {
	#if ASSERTIONS
	assert(Module['wasmOffsetData'], 'wasmOffsetData not found on Module object');
	#endif
	wasmOffsetConverter = resetPrototype(WasmOffsetConverter, Module['wasmOffsetData']);
	}
	#endif

I only see a demo like this, so is this the way to inject a WasmOffsetConverter?

emscripten/test/manual_wasm_instantiate.html

Line 178 in 0538c9d

wasmOffsetConverter = new WasmOffsetConverter(wasmBinary, output.module);

[sbc100]

Is the problem you are seeing the the assert on line 1097 of preamble.js is firing? i.e. is it
Module['wasmOffsetData'] that is missing?

[junyuecao]

Is the problem you are seeing the the assert on line 1097 of preamble.js is firing? i.e. is it
Module['wasmOffsetData'] that is missing?

@sbc100 Do you mean that I should construct a new WasmOffsetConverter and set to the Module['wasmOffsetData'] ?
The problem is constructing a WasmOffsetConverter need the output.module which is not ready before calling Module['instantiateWasm'] (ling 1113)

emscripten/src/preamble.js

Lines 1099 to 1113 in 0538c9d

	wasmOffsetConverter = resetPrototype(WasmOffsetConverter, Module['wasmOffsetData']);
	}
	#endif
	#if LOAD_SOURCE_MAP && PTHREADS
	if (ENVIRONMENT_IS_PTHREAD) {
	#if ASSERTIONS
	assert(Module['wasmSourceMapData'], 'wasmSourceMapData not found on Module object');
	#endif
	wasmSourceMap = resetPrototype(WasmSourceMap, Module['wasmSourceMapData']);
	}
	#endif
	try {
	return Module['instantiateWasm'](info, receiveInstance);

I was wondering if we should move constructing WasmOffsetConverter to

emscripten/src/preamble.js

Line 951 in 0538c9d

function receiveInstance(instance, module) {

[sbc100]

Sorry no, I wasn't suggesting anything, I was asking a specific questions in order to better understand what is going on: Is the problem you are seeing that the assert on line 1097 of preamble.js is firing?

[junyuecao]

@sbc100

Is the problem you are seeing that the assert on line 1097 of preamble.js is firing?

It's not about the assert on line 1097. Let me try to explain the problem:
If I didn't set wasmOffsetData , here it is undefined

then resetPrototype will return an object without offset data so that asan can not get the func name of an offset.

So it means I should provide an Module["wasmOffsetData"] for resetPrototype to retrurn a correct WasmOffsetConverter.
Here is the problem: the constructor of WasmOffsetConverter accept wasmBytes and wasmModule. But I can't get the wasmModule before Module["instantiateWasm"] is called.

function WasmOffsetConverter(wasmBytes, wasmModule) {}

I think it may work to put it in the function receiveInstance(instance, module) so that I have a chance to constructing an WasmOffsetConverter in my custom Module["instantiateWasm"].