function ccall(ident, returnType, argTypes, args, opts) {
  // For fast lookup of conversion functions
  var toC = {
    'string': function(str) {
      var ret = 0;
      if (str !== null && str !== undefined && str !== 0) { // null string
        // at most 4 bytes per UTF-8 code point, +1 for the trailing '\0'
        var len = (str.length << 2) + 1;
        ret = stackAlloc(len);
        stringToUTF8(str, ret, len);
      }
      return ret;
    },
    'array': function(arr) {
      var ret = stackAlloc(arr.length);
      writeArrayToMemory(arr, ret);
      return ret;
    }
  };

  function convertReturnValue(ret) {
    if (returnType === 'string') return UTF8ToString(ret);
    if (returnType === 'boolean') return Boolean(ret);
    return ret;
  }

  var func = getCFunc(ident);
  var cArgs = [];
  var stack = 0;
  if (args) {
    for (var i = 0; i < args.length; i++) {
      var converter = toC[argTypes[i]];
      if (converter) {
        if (stack === 0) stack = stackSave();
        cArgs[i] = converter(args[i]);
      } else {
        cArgs[i] = args[i];
      }
    }
  }
  var ret = func.apply(null, cArgs);

  ret = convertReturnValue(ret);
  if (stack !== 0) stackRestore(stack);
  return ret;
}
@param {string|null=} returnType
    @param {Array=} argTypes
    @param {Arguments|Array=} args
    @param {Object=} opts