On Monday, 12 November 2012 at 02:31:05 UTC, Walter Bright wrote:
To make a shared type work in an algorithm, you have to: 1. ensure single threaded access by aquiring a mutex 2. cast away shared 3. operate on the data 4. cast back to shared 5. release the mutex
This is a fairly reasonable use of shared, but it is bypassing the type system. Once shared is cast away, it is free to be mixed with thread local variables. Pieces can be assigned to non-shared globals, impure functions can stash reference, weakly pure functions can mix their arguments together, etc... If locking converts shared(T) to bikeshed(T), I bet some of safeD's logic for no escaping references could be used to improve things.
It's also interesting to note that casting away shared after taking a lock implicitly means that everything was transitively owned by that lock. I wonder how well a library could promote/enforce such a thing?
