[Haskell-cafe] Safe/Unsafe calls with the GHC Foreign Function Interface

[Stefan O'Rear]

On Thu, May 17, 2007 at 10:32:11PM -0500, Rob Hoelz wrote:
> More questions from Rob regarding his mysterious bindings...
> 
> So I've been reading the docs for the FFI, and it's my understanding
> that foreign functions imported as "unsafe" are faster, but they've got
> a problem with callbacks.  From what I read, I believe that I should
> just make a foreign function safe if it sets up a callback; is this
> correct?  Normally I wouldn't bother people with questions like this,
> but I'd rather be absolutely certain and avoid tracking down a strange
> bug later.
> 
> Many thanks as always,
> Rob

If it *calls* a callback into haskell.

Also, for unfathomable reasons, safety has been overloaded to include
forking OS threads.  If it could block (like getchar), you must make
it safe. 

Stefan