Haddock version during build

[Claus Reinke]

> It wouldn't be a disaster if we had to ship Haddock with GHC, but it's not 
> ideal.  I really want Haddock to be a separate entity, as far as possible - 
> just a client of the GHC API.  This is a problem that will crop up with 
> other clients of the GHC API too: they all need to know the default 
> package.conf location.  Perhaps we should have a general solution to this? 
>  I'm open to suggestions.  Here's one: when installing a GHC distribution 
> we create a tiny library called libghc-defaults.a that exports a single symbol
> 
>   char *ghc_default_libdir="/usr/lib/ghc-6.10/or/whatever"
> 
> and we always add libghc-defaults.a when linking the GHC package.
> 
> The downside is that this means running a C compiler at install time, but 
> only if the GHC binary dist is supposed to be position-independent - many 
> are not.

Why not make that a proper package, exposing a Haskell module
GHC.SettingsAndPaths? There are other paths that have similar
issues, I assume (docdir, manpage, ghc-pkg database, ..)? 

Are there differences in who is trying to find those paths (GHC 
vs GHC-compiled GHC API client vs GHC-based commandline
tools vs ..), or could one solution fit all? GHC can't currently find
it docdir, so I suggested registering these paths with ghc-pkg, 
which GHC can find, but perhaps using runghc on a one-liner
that imports GHC.SettingsAndPaths would work just as well?

And if one does relocate (parts of) GHC, how is the relinking 
(of GHC, GHCi, Haddock, ToolX, ..) supposed to be done,
to get the uptodate locations? If the paths themselves are
registered with ghc-pkg, updating is easy, but if a package
with path info is registered with ghc-pkg, one either needs
to relink, or link dynamically?

Btw, could any results from this discussion, and any other GHC API
issues, please be linked from the GhcApiStatus page? I added the 
libdir issue and the generic AST traversal issue a while ago, but I 
can't tell from that page what is going on, and I haven't seen others 
using this page, nor have I seen answers/opinions about the issues 
raised (has that Haskell-cafe question "How to get the typechecked 
AST" even received an answer?). Has this GSoC project started 
yet, and is there (going to be) a blog for it? It is just that I'm really 
interested in this, and don't want to miss any developments!-)

Claus