On 15 November 2012 17:17, Andrei Alexandrescu <SeeWebsiteForEmail@erdani.org> wrote:
On 11/15/12 1:08 AM, Manu wrote:
On 14 November 2012 19:54, Andrei Alexandrescu
<SeeWebsiteForEmail@erdani.org <mailto:SeeWebsiteForEmail@erdani.org>>

wrote:
    Yah, the whole point here is that we need something IN THE LANGUAGE
    DEFINITION about atomicLoad and atomicStore. NOT IN THE IMPLEMENTATION.

    THIS IS VERY IMPORTANT.


I won't outright disagree, but this seems VERY dangerous to me.

You need to carefully study all popular architectures, and consider that
if the language is made to depend on these primitives, and the
architecture doesn't support it, or support that particular style of
implementation (fairly likely), than D will become incompatible with a
huge number of architectures on that day.

All contemporary languages that are serious about concurrency support atomic primitives one way or another. We must too. There's no two ways about it.

[snip]
Side note: I still think a convenient and fairly practical solution is
to make 'shared' things 'lockable'; where you can lock()/unlock() them,
and assignment to/from shared things is valid (no casting), but a
runtime assert insists that the entity is locked whenever it is
accessed.

This (IIUC) is conflating mutex-based synchronization with memory models and atomic operations. I suggest we postpone anything related to that for the sake of staying focused.

I'm not conflating the 2, I'm suggesting to stick with the primitives that are already present and proven, at least for the time being.
This thread is about addressing the problem in the short term, long term plans can simmer until they're ready, but any moves in the short term should make use of the primitives available and known to work, ie, don't try and weave in language level support for architectural atomic operations until there's a thoroughly detailed plan, and it's validated against many architectures so we know what we're losing.
Libraries can already be written to do a lot of atomic stuff, but I still agree with the OP that shared should be addressed and made more useful in the short term, hence my simplistic suggestion; runtime assert that a shared object is locked when it is read/written, and consequently, lift the cast requirement, making it compatible with templates.