4 ms·

SecureRandom is thread safe, and the global initialization is volatile. What am I missing?

• deleted 10y ago
  [deleted]
• Groxx 10y ago
  The `volatile_var = local_var = X` seems safe - even if you break it into two assignments it only uses the local var afterward, so SecureRandom should be fully initialized in that thread. And though SecureRandom is non-final, it does look safe to use with double-initialization - it self-seeds if not explicitly seeded (it's not in this case), so even double-init shouldn't repeat a value (which is as strong of a statement as SecureRandom allows here - no idea if it makes that claim!). So I'd think it only matters if `volatile` doesn't guarantee that non-final object fields are fully initialized... and I can't find anything that explicitly states one way or another, so I'm not sure. If it doesn't make that guarantee, then yeah - this could publish a partly-initialized SecureRandom without a generator, which would probably crash. But the contents of https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.htm... imply to me that write-then-read is equivalent to a synchronized block or any other monitor sequence (and in the method they only use the local var, so it doesn't matter for the creator-thread), so I suspect it's fine. Just can't claim any further. @exabrial: care to elaborate? What's unsafe / have you seen crashes due to uninitialized SecureRandom?