[Haskell-cafe] cabal under windows (was Re: Haskell-CafeDigest, Vol 51, Issue 180)

[Bayley, Alistair]

> From: haskell-cafe-bounces at haskell.org 
> [mailto:haskell-cafe-bounces at haskell.org] On Behalf Of Duncan Coutts
> On Thu, 2007-11-29 at 13:51 +1100, Tim Docker wrote:
> > 
> > Is it actually reasonable to expect any cabal packages that 
> depend on
> > external c libraries and headers to build out of the box on 
> windows? How
> > can cabal find out where those files are, without requiring a config
> > file to be edited?
> 
> It's usually worse than that. The most likely situation is that the C
> library and header files are not even installed. This is a big problem
> for all packages that wrap C libs.

It can be done, with a bit of work, luck, and a brittle cabal Setup.hs
:-)

If you assume that the user has installed the 3rd party library
correctly, and you know it's layout and an executable it uses (which is
on the PATH), then you can do something like what HSQL does (and Takusen
now, which copied HSQL's approach). That is, you ask for the location of
the known executable in the PATH, and then build your header (include)
and library paths relative to the location of the executable. That's
what we've done in Takusen for the Oracle and Sqlite installations. For
PostgreSQL there is a program you can run which will emit the installed
locations of the include and library files, so that's slightly less
brittle.

Of course, if the particular libs are not on the PATH then this won't
work :-(

Alistair
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