package description fields

[Simon Marlow]

On 09 August 2005 11:23, Ross Paterson wrote:

> On Tue, Aug 09, 2005 at 09:02:50AM +0100, Simon Marlow wrote:
>> On 08 August 2005 16:57, Jonathan Cast wrote:
>> [Simon wrote:]
>>>> 
>>>>   --bindir=<dir>
>>>>   --libdir=<dir>
>>>>   --datadir=<dir>
>>>> 
>>>> where the values of these would be directories relative to $prefix
>>>> (or absolute?  relative to $prefix seems nicer).
>>> 
>>> Relative paths here break compatibility  with Autoconf; when I
>>> install a program, I don't care where its configure script comes
>>> from, I just want to   be  able  to   invoke  it   the  way   I
>>> expect   to.   Gratuitous incompatibilities between configure
>>> scripts is very inconvenient.
>> 
>> I do agree, and I half-expected someone to point out the
>> inconsistency. OTOH, this isn't a "configure script", it's the
>> Setup.lhs program.  You already have to know that it isn't an
>> autoconf configure script, because it has different syntax.
> 
> Another incompatibility is that configure has options --datadir etc
> with a different meaning to yours.  I think yours should be renamed;
> we might want the autoconf-style ones too.

Really?  I intended them to work in the same way.  What differences are
you referring to?

If you think this is a generalisation too far, I guess I could live with
having fixed values for all these, but they should be relative to
$prefix, and that still leaves us with Krasimir's complaint about the
default $bindir/$libdir on Windows.

>> One reason I suggested that relative paths would be better is
>> because it allows you to build a binary/library that is
>> prefix-independent, at least on Windows where a binary knows the
>> absolute $bindir and hence can derive $prefix because it knows
>> $bindir relative to $prefix. 
> 
> What would the code in the packaged program look like?  It seems you'd
> want some library support for this.

I suppose you'd have something like this:

  getPrefix :: FilePath  -- bindir relative to prefix
            -> FilePath  -- returns prefix

but it only works on Windows.  GHC, Happy, Alex and Haddock all have
something like this internally (but bindir is either fixed or assumed to
be equal to $prefix right now).  From prefix you can get libdir and
datadir, if these are also specified relative to prefix.

> And what if the builder modified bindir?

If the builder can modify bindir, the program gets the value from
paths.h (or whatever mechanism we choose).

Cheers,
	Simon