You can use emscripten to generate fairly minimal code output.
Consider the following trivial file adder.c:
int adder (int a, int b) {
return a + b;
}
Compile it like this (requires a fairly recent emscripten):
emcc -O2 -s WASM=1 -s SIDE_MODULE=1 -o adder.wasm
To see what it generated, disassemble it to wast textual form using binaryen's wasm-dis (you can also use wasm2wast from wabt):
wasm-dis adder.wasm -o adder.wast
The disassembled source should look something like this:
(module
(type $0 (func (param i32 i32) (result i32)))
(type $1 (func))
(import "env" "memoryBase" (global $import$0 i32))
(import "env" "memory" (memory $0 256))
(import "env" "table" (table 0 anyfunc))
(import "env" "tableBase" (global $import$3 i32))
(global $global$0 (mut i32) (i32.const 0))
(global $global$1 (mut i32) (i32.const 0))
(export "__post_instantiate" (func $2))
(export "runPostSets" (func $1))
(export "_adder" (func $0))
(func $0 (type $0) (param $var$0 i32) (param $var$1 i32) (result i32)
(i32.add
(get_local $var$1)
(get_local $var$0)
)
)
(func $1 (type $1)
(nop)
)
(func $2 (type $1)
(block $label$0
(set_global $global$0
(get_global $import$0)
)
(set_global $global$1
(i32.add
(get_global $global$0)
(i32.const 5242880)
)
)
(call $1)
)
)
;; custom section "dylink", size 5
)
You can then run this in node (v8.X or later) like this:
const WA = WebAssembly,
env = {memoryBase: 0,
tableBase: 0,
memory: new WA.Memory({initial: 256}),
table: new WA.Table({initial: 0, element: 'anyfunc'})},
code = new Uint8Array(require('fs').readFileSync('adder.wasm'))
WA.compile(code).then(m => {
return new WA.Instance(m, {env: env})
}).then(i => {
console.log(i.exports._adder(7, 8))
})
Note that if you want to support code that uses the stack and/or heap memory things get more complicated. I.e. you'll at least need to set memoryBase and call __post_instantiate from your host environment before you call any other exports.
If you want to interpret WebAssembly code without a JavaScript environment you can run it using wac/wace (full disclosure: I created this project). Note that wace assumes you have a "_main" or "main" function defined.
