title: Swift mutable array thread safety
body: <p>Mutable arrays in Swift are not thread safe, so write access needs to be synchronized. Is it also the case that all reads need to be too? Specifically, are the following thread safe without the use of locks, serial queues etc. (assuming in both cases that other threads could be mutating the array):</p>
  
  <ol>
  <li>Accessing the count property of a mutable array</li>
  <li>Passing the array to a function, or assigning it to a variable (given that both of which will copy the array, since it's a struct)</li>
  </ol>