void jsvAppendStringBuf(JsVar *var, const char *str, size_t length) {
  assert(jsvIsString(var));
  JsvStringIterator dst;
  jsvStringIteratorNew(&dst, var, 0);
  jsvStringIteratorGotoEnd(&dst);
  /* This isn't as fast as something single-purpose, but it's not that bad,
   * and is less likely to break :) */
  while (length) {
    jsvStringIteratorAppend(&dst, *(str++));
    length--;
  }
  jsvStringIteratorFree(&dst);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.