Emscripten: PROXY_TO_PTHREAD causes runtime to exit despite NO_EXIT_RUNTIME

[VirtualTim]

Example:

#include <iostream>
int main(int argc, char** argv) {
    std::cout << "I shouldn't exit" << std::endl;
}

Compile like:
emcc test.cpp -s USE_PTHREADS=1 -s PROXY_TO_PTHREAD=1 -s NO_EXIT_RUNTIME=1 -o test.html

The following gets logged to the console:

15:03:52.887 Preallocating 1 workers for a pthread spawn pool. test.html:1237:13
15:03:53.018 I shouldn't exit test.html:1237:13
15:03:53.020 ExitStatus: Program terminated with exit(0) test.js:7291:24

This is not personally an issue for me, just something I ran into when testing. I figured I should log it anyway.

[niklasf]

Shutting down the runtime also prevents calling functions (for example with Module.ccall(...)) later on.

Since this might be a bit of a niche issue I put a $100 bounty on it.

[sbc100]

Wow, is this the first emscripten bounty? Very exciting. Somebody will go for it I'm sure.

[niklasf]

@juj mentioned a workaround in https://github.com/emscripten-core/emscripten/issues/8969#issuecomment-511328047: EM_ASM(Module['noExitRuntime'] = true);

[dschuff]

I was investigating related behavior in #9251 and I tried running with atexit() handlers registered, and it appears that they correctly do not get run. Also it doesn't appear that browsers currently log ExitStatus results. So I'm a bit unsure what behavior this bug is referring to? Is this a node application?

[VirtualTim]

When I reported this I was seeing this in a browser. Perhaps things changed since February?
Also I'm pretty sure that previously this code was getting hit on exit: https://github.com/emscripten-core/emscripten/blob/bef558affb630141e9fb0e955a9c444a87fb73fe/src/postamble.js#L153-L157

[VirtualTim]

Just tested this with 1.38.43. Exit code doesn't get logged, but the program still terminates.
This can be verified by putting a breakpoint in the ExitStatus function mentioned in the above comment.

[juj]

Fixed in https://github.com/emscripten-core/emscripten/pull/10126

[VirtualTim]

Make sure you collect your bounty @juj :)

[juj]

Oh wait what, there was a bounty? That is very cool! :)