Build system idea

[Roman Leshchinskiy]

On 13/08/2008, at 17:47, Simon Marlow wrote:

> Roman Leshchinskiy wrote:
>> On 12/08/2008, at 20:11, Simon Marlow wrote:
>>> - Extract the code from Cabal that generates Makefiles, and treat  
>>> it as
>>>  part of the GHC build system.  Rather than generating a Makefile
>>>  complete with build rules, we generate a Makefile that just
>>>  has the package-specific metadata (list of modules, etc.), and put
>>>  the code to actually build the package in the GHC build system.
>> Sounds good. It would be nice if the .cabal parser from Cabal could  
>> be made into a separate, stable library which ghc (and nhc?) could  
>> use.
>> This makes me wonder, though. Wouldn't this model make more sense  
>> for Cabal in general than the current approach of duplicating the  
>> functionality of autoconf, make and other stuff? If it works ghc,  
>> it ought to work for other projects, too. Cabal as a preprocessor  
>> seems much more attractive to me than as a universal build system.
>
> So packages would be required to provide their own build system?   
> That sounds like it would make it a lot harder for people to just  
> create a package that others can use.  The ease of making a Cabal  
> package has I think a lot to do with the wealth of software  
> available on Hackage.

Of course there should be a standard build system for simple packages.  
It could be part of Cabal or a separate tool (for which Cabal could,  
again, act as a preprocessor).

> GHC is a special case: we already need a build system for other  
> reasons.

I agree. I just don't think that adding a full-fledged build system to  
Cabal is the solution. In my experience, huge monolithic tools which  
try to do everything never work well. I much prefer small, modular  
tools. A Haskell-based build system is an interesting project but why  
does it have to be a part of Cabal?

> It was a design decision early on with Cabal that we didn't want to  
> rely on the target system having a Unix-like build environment.  You  
> might disagree with this, but it certainly has some value: a Windows  
> user can download GHC and immediately start building and installing  
> external packages without having to install Cygwin.

I agree with this decision but IIUC, this only really works for simple  
(wrt building) packages which don't even use configure. Making Cabal  
into a modular preprocessor and providing a thin wrapper for ghc -- 
make which can act as a target for Cabal would achieve this just as  
well.

Roman