Threadsafe singleton using volatile,synchonized

[Sean Kelly]

BLS wrote:
> Thanks Sean, indeed a very interesting thread.
> From 2004;It is really worth to browse the archives!
> What is the reason/rationale for using volatile in this way ?

In D, 'volatile' is a statement rather than a storage attribute.  So you 
need to use it explicitly in places where you want to restrict 
compiler-based code movement.  In the code below, a temporary is used to 
  ensure that Singleton (s) is fully constructed before s is set, 
otherwise the compiler could theoretically do this:

s = new Singleton;

// translates to

s = allocate_memory for Singleton;
s.ctor();

The presence of 'volatile' is to ensure that the compiler doesn't try to 
eliminate 'tmp' entirely and just use 's', since that would be a legal 
optimization.

> Another Question:
> Is something like this available 
> 
> CriticalSectionBegin()
> {
> // Your Single thread code goes here
> }
> CriticalSectionEnd()

Other than synchronized? Could you provide more detail?


Sean