-s LINKABLE=1 -s ASYNCIFY=1 causes main loop to stop working

[BinBashBanana]

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.74 (1092ec30a3fb1d46b1782ff1b4db5094d3d06ae5)
clang version 20.0.0git (https:/github.com/llvm/llvm-project 322eb1a92e6d4266184060346616fa0dbe39e731)
Target: wasm32-unknown-emscripten
Thread model: posix

Take the sample code in emtest.c:

#include <stdio.h>
#include <time.h>

#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#endif

void mainloop(void)
{
	time_t rawtime;
	struct tm *timeinfo;
	time(&rawtime);
	timeinfo = localtime(&rawtime);
	printf("%s", asctime(timeinfo));
}

int main()
{
	printf("Hello from main!\n");
#ifdef __EMSCRIPTEN__
	emscripten_set_main_loop(mainloop, 0, 0);
#else
	while(1)
		mainloop();
#endif
	printf("Bye from main!\n");
	return 0;
}

Any of the below commands will produce a working program; i.e. prints the current time forever.

emcc emtest.c -o emtest.html -s MAIN_MODULE=1
emcc emtest.c -o emtest.html -s ASYNCIFY=1
emcc emtest.c -o emtest.html -s ASYNCIFY=1 -s MAIN_MODULE=2

However with these options set, main is called, but emscripten encounters an exception before mainloop is called.

emcc emtest.c -o emtest.html -s ASYNCIFY=1 -s MAIN_MODULE=1
emcc emtest.c -o emtest.html -s ASYNCIFY=1 -s LINKABLE=1

The exception is below:

Uncaught Internal Error! Attempted to invoke wasm function pointer with signature "v", but no such functions have gotten exported!
quit_				@	emtest.js:50
handleException			@	emtest.js:1168
callUserCallback		@	emtest.js:1219
runIter				@	emtest.js:1456
MainLoop_runner			@	emtest.js:1558
requestAnimationFrame
requestAnimationFrame		@	emtest.js:1478
MainLoop_scheduler_rAF		@	emtest.js:1362
setMainLoop			@	emtest.js:1574
_emscripten_set_main_loop	@	emtest.js:1583
imports.<computed>		@	emtest.js:4395
$__original_main		@	emtest.wasm:0x3e3f
$main				@	emtest.wasm:0x3f9e
ret.<computed>			@	emtest.js:4427
(anonymous)			@	emtest.js:593
callMain			@	emtest.js:5151
doRun				@	emtest.js:5201
(anonymous)			@	emtest.js:5210
setTimeout
run				@	emtest.js:5208
runCaller			@	emtest.js:5136
removeRunDependency		@	emtest.js:526
receiveInstance			@	emtest.js:714
receiveInstantiationResult	@	emtest.js:732
createWasm			@	emtest.js:755
await in createWasm
(anonymous)			@	emtest.js:4797

I built with emcc emtest.c -o emtest.html -s MAIN_MODULE=1 -s ASYNCIFY=1 -s ASYNCIFY_DEBUG=1 -s DYLINK_DEBUG=1 -s ASSERTIONS=2 and attached the full console output to this issue.

localhost-1736814751439.log

Also note that compiling with at least -O1 and without at least -s ASSERTIONS=1, the error becomes silent.