[Haskell-cafe] Re: Export Haskell Libraries
simonmarhaskell at gmail.com
Tue Apr 17 08:19:51 EDT 2007
Dan Weston wrote:
> In the GHC docs:
> "There can be multiple calls to hs_init(), but each one should be
> matched by one (and only one) call to hs_exit()."
> What exactly happens with nested calls? Is there only one runtime
> created, with a simple counter to know which hs_exit should shut it
Yes. But the runtime doesn't currently support restarting (hs_exit() followed
> If so, is there a way of having multiple interpreters open safely
> at the same time?
I'm not sure exactly what you mean by "multiple interpreters". The runtime is
only designed to support a single instance of itself (it uses global static
> Or does each hs_init() create a new separate concurrent runtime (the
> preferable alternative)?
Nope, see above. To do that you'd need a "runtime handle" returned by hs_init()
and passed to every foreign exported function, somehow.
> And what is the cost of creating and destructing the GHC runtime anyway?
> Can the Haskell interpreter be in a Linux shared-object library, so long
> as I make sure to call hs_init() after loading and hs_exit() before
> unloading it? My experiments so far show this working flawlessly, but I
> vaguely remember an e-mail thread saying GHC couldn't be linked in
Perhaps, although the shared library won't really be shared - it'll be linked in
place each time you use it, because we don't currently have support for PIC
everywhere (well, we have partial support and there's a SoC project to finish it
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