On 11/14/12 4:23 AM, David Nadlinger wrote:
On Wednesday, 14 November 2012 at 00:04:56 UTC, deadalnix wrote:
That is what java's volatile do. It have several uses cases, including
valid double check locking (It has to be noted that this idiom is used
incorrectly in druntime ATM, which proves both its usefullness and
that it require language support) and disruptor which I wanted to
implement for message passing in D but couldn't because of lack of
support at the time.
What stops you from using core.atomic.{atomicLoad, atomicStore}? I don't
know whether there might be a weird spec loophole which could
theoretically lead to them being undefined behavior, but I'm sure that
they are guaranteed to produce the right code on all relevant compilers.
You can even specify the memory order semantics if you know what you are
doing (although this used to trigger a template resolution bug in the
frontend, no idea if it works now).
David
This is a simplification of what should be going on. The
core.atomic.{atomicLoad, atomicStore} functions must be intrinsics so
the compiler generate sequentially consistent code with them (i.e. not
perform certain reorderings). Then there are loads and stores with
weaker consistency semantics (acquire, release, acquire/release, and
consume).
Andrei
