[Haskell-cafe] Help from C libraries experts

Tillmann Rendel rendel at cs.au.dk
Thu Apr 30 08:35:58 EDT 2009


Maurício wrote:
> My goal is to have a place where one can find reliable and
> comprehensive low-level bindings to foreign libraries, so that
> writing higher level bindings becomes an easier task.

Like others, I think you should consider making this place not a single 
package, but a bunch of packages. For example, one could make a 
convention that a package named bindings-foo contains low-level bindings 
to a c library foo.

In your guidelines, you say:
> Code should be portable and easy to build. 

Does your understanding of "portable" include Windows?

The problem with windows is that you usually do not have these c 
libraries installed, and no easy way to install them, so a binding is 
not enough. For example, the Haskell package zlib bundles the actual 
zlib c code for Windows users, which works not too bad. Do you plan to 
support this kind of thing in your bindings project?

I am not sure which kind of c libraries can be reasonably included in 
cabal packages. I guess the idea breaks with more complicated build 
systems for the c library, and with libraries written in other languages 
then c, and with libraries which are supposed to be linked against 
dynamically, and with complicated license situations, and in all kinds 
of other situations. Anyway, if there are more such libraries then just 
zlib, maybe a naming convention would be helpful, like:

- bundled-foo    is a package which contains just the c code of foo
- bindings-foo   contains the low-level bindings for foo

Now bindings-foo could use cabal configurations to depend on the c 
library directly on most systems, but depend on bundled-foo on Windows. 
This way, on all systems, you could just install bindings-foo and be 
able to use the library. If you have special needs, you could still use 
an explicit flag on Windows to configure bindings-foo not to depend on 
bundled-foo, and install the c library yourself instead.


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