Build system idea

Roman Leshchinskiy rl at
Fri Aug 15 00:06:17 EDT 2008

On 14/08/2008, at 18:01, Simon Marlow wrote:

> Roman Leshchinskiy wrote:
>> But that is precisely my (other) point. A lot of that work is  
>> really unnecessary and could be done by Cabal since it only or  
>> mostly depends on the package information. Instead, it is  
>> implemented somewhere in Distribution.Simple and not really usable  
>> from the outside. For instance, a lot of the functionality of setup  
>> sdist, setup register and so on could be implemented generically  
>> and used by a make-based build system as well.
> That's exactly what I'm proposing we do in GHC: re-use Cabal's setup  
> register and some of the other parts of the simple build system in a  
> make-based build system for packages.  It might require a bit of  
> refactoring of Cabal, but I don't expect it to be a major upheaval  
> at all.

Ah! I hadn't realised that you are going to reuse Cabal functionality.  
You wrote "Extract the code from Cabal that generates Makefiles" so I  
thought you won't be really using anything from Cabal.

> I think what you're proposing is mostly a matter of abstracting  
> parts of Cabal with cleaner and more modular APIs, which is  
> absolutely a good thing, but doesn't require a fundamental  
> redesign.  The tight coupling and lack of separation between Cabal's  
> generic parts and the simple build system is somewhat accidental  
> (lazy implementors :-), and is actually a lot better than it used to  
> be thanks to the work Duncan has put in.  I'm sure it'll improve  
> further over time.

IMO, getting this right is absolutely crucial for Cabal's usability  
and should be the primary short-term goal. Then again, I guess I  
should contribute code instead of opinions already :-)

> The other part of your complaint is that the BuildInfo is in  
> the .cabal file along with the PackageDescription (the types are  
> pretty well separated internally).  Again I don't think there's  
> anything fundamental here, and in fact some packages have  
> separate .buildinfo files.

Well, it is fundamental in the sense that this is how Cabal is used  
(and is supposed to be used) at the moment. It is good that Cabal  
separates these things internally but the separation should be  
enforced in the external interface, as well.


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