helloworld_emcc_connect_to_js_01.log

$ emcc libsqrt.c 

#include <math.h>
int int_sqrt(int x) {
  return sqrt(x);
}

$ emacs main.c

#include<stdio.h>
int int_sqrt(int x);
int main(int argc, char** argv) {
  printf("%d\r\n", int_sqrt(2));
}

$ emcc main.c libsqrt.c 
$ node a.out.js 
1