• Andrew Wiley (11/11) Dec 16 2011 I was looking through Jonathan Davis's pull request to remove static
• deadalnix (5/16) Dec 27 2011 Well according to the spec, it should work with the garantee given by

Andrew Wiley <wiley.andrew.j gmail.com> writes:

I was looking through Jonathan Davis's pull request to remove static
constructors from std.datetime, and I realized that I don't know
whether Double Checked Locking is legal under D's memory model, and
what the requirements for it to work would be.
(if you're not familiar with the term, check out
http://en.wikipedia.org/wiki/Double-checked_locking - it's a useful
but problematic programming pattern that can cause subtle concurrency
bugs)
It seems like it should be legal as long as the variable tested and
initialized is flagged as shared so that the compiler enforces proper
fences, but is this actually true?

deadalnix <deadalnix gmail.com> writes:

Le 17/12/2011 08:47, Andrew Wiley a écrit :
 I was looking through Jonathan Davis's pull request to remove static
 constructors from std.datetime, and I realized that I don't know
 whether Double Checked Locking is legal under D's memory model, and
 what the requirements for it to work would be.
 (if you're not familiar with the term, check out
 http://en.wikipedia.org/wiki/Double-checked_locking - it's a useful
 but problematic programming pattern that can cause subtle concurrency
 bugs)
 It seems like it should be legal as long as the variable tested and
 initialized is flagged as shared so that the compiler enforces proper
 fences, but is this actually true?

Well according to the spec, it should work with the garantee given by 
shared.

But in real life, the compiler is unable to ensure that. This is 
compiler issue.