(module
  ;; ---- export main function  ---
  (export "exported_main" (func $main)) ;; 関数$mainを、exported_main という名前で公開
  (func $main (result i32) ;; i32（符号あり32ビット整数）を返す
    i32.const 1 ;; スタックに「定数1」を積む
    return ;; スタックの値を返す
  )
)

$ wat2wasm one.wat

$ git clone --recursive https://github.com/WebAssembly/wabt
$ cd wabt
$ mkdir build
$ cd build
$ cmake ..
$ cmake --build .

'use strict'

const fs = require('fs');
const filename = process.argv[2]; // 対象とするwasmファイル名
console.warn('Loading wasm file: ' + filename);

let source = fs.readFileSync(filename);
let typedArray = new Uint8Array(source);
let ret = null;


WebAssembly.instantiate(typedArray, 
  {} // 実行時の環境
).then(result => {
  ret = result.instance.exports.exported_main();
  console.warn('ret code=' + ret);
  process.exit(ret);
}).catch(e => {
  console.log(e);
});

$ node run_wasm_simple.js
Loading wasm file: one.wasm
ret code=1

(module
  ;; ---- export main function  ---
  (export "exported_main" (func $main))
  (func $main (result i32)
    i32.const 111
    return
  )
)

$ wat2wasm one.wat
$ node run_wasm_simple.js one.wasm
Loading wasm file: one.wasm
ret code=111

8;

(module
  (export "exported_main" (func $main))
  (func $main (result i32)
    i32.const 8
    return
  )
)

$  npm install esprima

const tree = loadAndParseSrc();

[ 'lit', 8 ]

function generate(tree) {
  if (tree === null) {
    return '';
  }

  if (tree[0] === 'lit') {
    const v = tree[1];

    const block = 'i32.const ' + v;
    return block;
  }

  println('-- ERROR: unknown node in generate() ---');
  printObj(tree);
  abort();
}

// ---- compile simplified tree into WAT ---
function compile(tree) {
  const mainBlock = generate(tree);

  let block = '(module' + LF();
  block = block + TAB() + '(export "exported_main" (func $main))' + LF();
  block = block + TAB() + '(func $main (result i32)' + LF();
  block = block + TAB() + TAB() + mainBlock + LF();
  block = block + TAB() + TAB() + 'return' + LF();
  block = block + TAB() + ')' + LF();
  block = block + ')';

  return block;
}

function LF() {
  return '\n';
}

function TAB() {
  return '  ';
}

// --- load and parse source ---
const tree = loadAndParseSrc();

// --- compile to WAT --
const wat = compile(tree);
writeFile('generated.wat', wat);

$ node mininode_wasm_01.js eight.js
$ more generated.wat
(module
  (export "exported_main" (func $main))
  (func $main (result i32)
    i32.const 8
    return
  )
)
$
$ wat2wasm generated.wat
$ node run_wasm_simple.js generated.wasm
Loading wasm file: generated.wasm
ret code=8

8;

process.exit(8);

PreprocessForDirect() {
  echo "-- preprocess for exit code:  src=$jsfile tmp=$direct_file --"
  echo "process.exit(" > $direct_file
  cat $jsfile | sed -e "s/;\$//" >>  $direct_file  #  remove ';' at line end
  echo ");" >> $direct_file
}

NodeDirect() {
  echo "-- node $src --"
  node $direct_file
  direct_exit=$?
  echo "direct exit code=$direct_exit"
}

TranslateToWat() {
  echo "--- translate src=$jsfile wat=$wat_file translater=$translater ---"
  node $translater $jsfile
  if [ "$?" -eq "0" ]
  then
    echo "translate SUCCERSS"
    mv generated.wat $wat_file
  else
    echo "ERROR! ... translate FAILED !"
    exit 1
  fi
}

$ node mininode_wasm_01.js sample/eight.js
$ mv generated.wat test/tmp/eight.js.wat

WatToWasm() {
  echo "--- wat $wat_file to wasm $wasm_file --"
  $wat_to_wasm $wat_file -o $wasm_file
  if [ "$?" -eq "0" ]
  then
    echo "wat2wasm SUCCERSS"
  else
    echo "ERROR! ... wat2wasm FAILED !"
    exit 1
  fi
}

ExecWasm() {
  echo "--- exec $wasm_file from node"
  node $wasm_exec $wasm_file
  wasm_exit=$?
  echo "wasm exit code=$wasm_exit"
}

$ node run_wasm_simple.js test/tmp/eight.js.wasm

$ node mininode_15.js mininode_wasm_01.js sample/eight.js
$ mv generated.wat test/tmp/inetep_eight.js.wat
$ watwasm test/tmp/inetep_eight.js.wat
$ node run_wasm_simple.js test/tmp/inetep_eight.js.wasm

CompareExitCode() {
  if [ "$direct_exit" -eq "$wasm_exit" ]
  then
    echo "OK ... node <-> wasm exit code match: $direct_exit == $wasm_exit"
  else
    echo "ERROR! ... node <-> wasm exit code NOT MATCH : $direct_exit != $wasm_exit"
    echo "ERROR! ... node <-> wasm exit code NOT MATCH : $direct_exit != $wasm_exit" > $exitcode_file
    exit 1
  fi

  if [ "$direct_exit" -eq "$interp_wasm_exit" ]
  then
    echo "OK ... node <-> interp-wasm exit code match: $direct_exit == $interp_wasm_exit"
  else
    echo "ERROR! ... node <-> interp-wasm exit code NOT MATCH : $direct_exit != $interp_wasm_exit"
    echo "ERROR! ... node <-> interp-wasm exit code NOT MATCH : $direct_exit != $interp_wasm_exit" > $exitcode_file
    exit 1
  fi
}

$ cd test
$ sh test_exitcode.sh mininode_wasm_01.js mininode_15.js eight.js
--- translate src=../sample/eight.js wat=tmp/eight.js.wat translater=../mininode_wasm_01.js---
-- start WASM translator --
Loading src file:../sample/eight.js  _argIndex=2
 ... 省略 ...
direct exit code=8
OK ... node <-> wasm exit code match: 8 == 8
OK ... node <-> interp-wasm exit code match: 8 == 8