RFC: ghc's dynamic linker

[Alastair Reid]

> Just a comment: it's, well, interesting how GHC has this fantastic
> method of importing modules at runtime, which is similar (at least
> in what it achieves) to the dynamic linker.  I dunno, it feels like
> reinvent-wheel syndrome.  Not saying that's a bad or good thing,
> just an observation.

I've played with dynamic linking quite a bit myself.  The problem with
dl_open and friends is that it was designed with very, very narrow
goals and the API doesn't provide anything not required to meet those
goals.  

It would be quite straightforward for the library to support multiple
namespaces so that you can load two versions of the same library and
have some of your code use one namespace and some use the other
namespace.  No joy.  (I don't think GHC needs this but it's something
we wanted for Knit.  Knit is a component-programming extension of C -
if you think 'ML functors', you're in the right ballpark.)

It would probably be trivial for the library to provide a way to say
'Please insert symbol "X" into your lookup table' but it doesn't.  
(IIRC, this is the essential function that the standard library lacks.)

--
Alastair Reid                 alastair@reid-consulting-uk.ltd.uk  
Reid Consulting (UK) Limited  http://www.reid-consulting-uk.ltd.uk/alastair/