code: function (readCallback, compile, args) {
      if (readCallback === undefined) {
        readCallback = function (path) {
          return {
            error: 'File import callback not supported'
          };
        };
      }
  
      // This is to support multiple versions of Emscripten.
      var addFunction = soljson.addFunction || soljson.Runtime.addFunction;
      var removeFunction = soljson.removeFunction || soljson.Runtime.removeFunction;
  
      var cb = addFunction(wrapCallback(readCallback));
      var output;
      try {
        args.push(cb);
        output = compile.apply(undefined, args);
      } catch (e) {
        removeFunction(cb);
        throw e;
      }
      removeFunction(cb);
      return output;
    }
docs: This calls compile() with args || cb