unsafePerformIO safety.

[Isaac Dupree]

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David Brown wrote:
> I've noticed quite a few pages referencing constructs such as:
> 
>   var :: MVar ([Foo])
>   var = unsafePerformIO (newMVar ([]))
> 
> and the likes.  Is there a danger of different uses of 'var' getting
> new MVars instead of all sharing one.

If I remember correctly, you "should" put {-# NOINLINE var #-} on a line
just before that.

> 
> Having a reliable way to create a piece of global state would be very
> convenient.

This is well known and extensively discussed - unfortunately it is a
complicated (or at least controversial) issue

Isaac

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