Working dlopen example in Emscripten

build.sh

#!/bin/bash

emcc ./module.c -sSIDE_MODULE -o module.o
emcc ./main.c \
    -lnodefs.js \
    -o ./main.js \
    -sMAIN_MODULE \
    -sEXPORTED_FUNCTIONS='["_main","ccall", "UTF8ToString", "lengthBytesUTF8", "FS"]' \
    -sEXTRA_EXPORTED_RUNTIME_METHODS='["ccall", "UTF8ToString", "lengthBytesUTF8", "FS"]' \
    -sFORCE_FILESYSTEM=1 
node ./main.js

main.c

#include <stdio.h>
#include <dlfcn.h>
#include <unistd.h>

typedef void (*hello_func)();

int main() {
    void* handle = dlopen("./module.o", RTLD_LAZY);
    if (!handle) {
        fprintf(stderr, "%s\n", dlerror());
        return 1;
    }

    hello_func func = (hello_func) dlsym(handle, "helloworld");
    if (!func) {
        fprintf(stderr, "%s\n", dlerror());
        dlclose(handle);
        return 1;
    }

    func();

    dlclose(handle);
    return 0;
}

module.c

#include <stdio.h>

void helloworld() {
    printf("Hello, world!\n");
}