How To Generate Standalone Webassembly With Emscripten

The documentation offers two options: let optimizer strip unnecessary code and then replace the .js glue with your own, or use SIDE_MODULE flag. Both options result in a memory imp

Solution 1:

You can simply set the output option (-o) to a filename with the .wasm extension. Emscripten will then output only the wasm file.

So if you have the following test.c file:

#include "emscripten.h"

EMSCRIPTEN_KEEPALIVE
int add(int a, int b) {
    return a + b;
}

And you compile it with emscripten like this:

emcc -O3 test.c -o test.wasm

you will only get the file test.wasm and no extra .js file. Also if you disassemble test.wasm using e.g. wasm2wat you'll get this WebAssembly text:

(module
  (type (;0;) (func))
  (type (;1;) (func (param i32 i32) (result i32)))
  (func (;0;) (type 0)
    nop)
  (func (;1;) (type 1) (param i32 i32) (result i32)
    local.get 0
    local.get 1
    i32.add)
  (memory (;0;) 256 256)
  (export "memory" (memory 0))
  (export "add" (func 1))
  (export "_start" (func 0))
  (data (;0;) (i32.const 1536) "\a0\06P"))

as you can see it's just what you would expect from a minimum webassembly binary.