HTML5: this.rtenv.callMain is not a function when using latest-upstream backend

[LinuxUserGD]

Godot version:
master (3418f76)

OS/device including version:
Arch Linux

Issue description:
This error shows when loading the .pck with Chromium
console log:

test.html:246 this.rtenv.callMain is not a function
displayFailureNotice @ test.html:246

Steps to reproduce:

scons p=x11 bits=64 target=release_debug tools=yes use_llvm=yes use_lld=yes use_thinlto=yes -j 8
./emsdk install latest       OR:      ./emsdk install latest-upstream
./emsdk activate latest               ./emsdk activate latest-upstream
source ./emsdk_env.sh
scons p=javascript target=release_debug tools=no -j 8
python3 -m http.server
http://localhost:8000/test.html

Tested projects: Solus Sphere (https://github.com/HugeGameArtGD/Solus-Sphere) and material demo (both GLES2)

[Mellondill]

Same with me, but I've tried it on macOS.
As I've understood new versions of Emscripten doesn't export callMain function in Module["callMain"] and this is the main problem.
Maybe someone knows how to resolve this problem?
@kripken if you would be so kind, maybe you can tell us what we can do, to enable exporting of callMain function with Emscripten?
Currently we are using 1.38.41 this version of emsdk

[Mellondill]

I've found the problem. Due to Emscriptens changlog :

callMain is no longer exported by default on Module, to allow better JS minification. You must add it to EXTRA_EXPORTED_RUNTIME_METHODS if you want to call it on Module. (In assertions builds, an error with an explanation is shown.)

[kripken]

Correct, yes, as the error says we no longer export it by default. You can add the flag to export it.

Sorry for this annoyance, but we sometimes need to make a breaking change like this in order to make progress. We do try to always document it in the changelog, and to make builds with assertions show a clear error, to minimize the annoyance.

[Mellondill]

@akien-mga , think this issue could be closed

[LinuxUserGD]

@Mellondill I think there should be a PR in Godot to make the flag the default option.

[Mellondill]

@LinuxUserGD ah, sorry forgot about PR

[Mellondill]

@LinuxUserGD created PR with needed changes

[Calinou]

@kripken Do you know which changes would be required for Godot to work without callMain? This way, we could benefit from better JavaScript minification as stated by the changelog 🙂

[kripken]

@Calinou in general you shouldn't need callMain - main will be called automatically by the emscripten runtime, when everything is ready. But if godot has special logic for when to start, then using callMain is reasonable (and the downside isn't big, it's just a few JS strings of "callMain" in the final JS file).

[Mellondill]

@Calinou As I understand, initial resource package must be synced in internal filesystem before main function could be called in Godot, so that's why we need such changes