Simon Peyton-Jones wrote:

[I've updated the "Semantics for foreign threads" document by
re-ordering the sections a bit.  It'd benefit from having a bit more
formal syntax.

That should be just a matter of copying from the ffi spec and adding an additional specialid... I had hoped to avoid learning how to use yet another TeX package... but OK, I'll do that.


No one has commented a single word on the operational
semantics.  I don't know whether that's because it's so clear that no
discussion is needed, or so opaque that no discussion is possible.]

I spent about half an hour staring at a printout, before I saw that it was all perfectly logical if I corrected one typo. Now I think there are no typos left in the formal semantics, so it should need less staring...


Anyway, do you think the proposal has been discussed enough for me to start working on a prototype implementation?

About threadsafe/safe:

I think Wolfgang is saying that the apparent efficiency gain of not
requiring thread-safety is illusory, [..]

In GHC, we might be able to save some time, but only for calls without call-back. As soon as there's a call-back, I can't see how we can save any time at all.


[...] and so we can abolish the
safe/threadsafe distinction.   I think that would be a very worthwhile
gain. Does anyone disagree with this?

Kill it kill it kill it! We don't need that distinction.
However, it might be worthwhile for other implementations of Haskell, but we can't tell, because GHC is the only one that supports "threadsafe" at the moment. Does anyone plan to add support for multiple OS threads to Hugs or NHC?


If someone wants to keep "safe" in the FFI spec as an "optimization hint", then that's fine for me, but something has to be done about the misleading naming ("safe" is NOT SAFE) and an optimization hint should never be the default. And it should be made absolutely clear that an implementation may treat everything as "threadsafe".


Cheers, Wolfgang

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