The bug from hell

unsafe.scala

// This code is unsafe to use in a multithreaded environment.

object A {
  def foo = "foo"
  B.bar
}

object B {
  def bar = "bar"
  A.foo
}






// SPOILER:
//
// Consider Thread-1 and Thread-2 initializing A and B, respectively, at the
// same time. Thread-1 running A's constructor needs to access B, and Thread-2
// running B's constructor needs to access A. Since neither object has finished
// initializing, both threads will wait for the other to finish before they can
// continue, causing a deadlock.