Integrating editline with ghc
Manuel M T Chakravarty
chak at cse.unsw.edu.au
Sun Jan 27 00:41:37 EST 2008
Am 25.01.2008 um 03:44 schrieb Judah Jacobson:
> On Jan 22, 2008 1:49 AM, Manuel M T Chakravarty
> <chak at cse.unsw.edu.au> wrote:
>> Simon Marlow:
>>> I think it would be a bad idea to provide EditReadline as
>>> described. The reason being that this would be a package with a
>>> variant license: its license is conditional on how it is built,
>>> which makes it that much harder for clients to understand what
>>> licensing restrictions apply, and to license themselves
>>> appropriately. (the alternative is to make EditReadline GPL, but
>>> that defeats the purpose).
>>> I don't even think we've considered variant licenses in Cabal
>>> before, and my inclination would be to disallow or at least
>>> vigorously discourage it.
>> I don't like this either.
>>> So I suggest we just keep readline as it is, and packages that want
>>> to use editline can switch at their discretion, using
>>> System.Console.Editline.Readline to make porting easier. In GHC I
>>> imagine we'll just switch to using editline.
>> That's fine if all platforms that by default have readline also have
>> editline. I just checked, Fedora 8 does have both. How about other
>> Linux distros? What is the situation on Solaris?
> A few distros (including Solaris) have libedit version 1.*, which
> appears to be too old to provide enough functionality to replace
> readline. From what I can tell, libedit-1 provides the header
> <editline.h>, whereas libedit-2 provides <histedit.h> as well as
> either <readline/readline.h> or <editline/readline.h>. (OS X 10.4 and
> 10.5 have 2.6 and 2.9, respectively.)
> From Christian, who helped me figure out what was going on:
>> It looks pretty bad with libedit under non-macs. It's also not on our
>> fedora7 machines. Under Solaris I did not find histedit.h
>> Surely http://www.thrysoee.dk/editline/libedit-20070831-2.10.tar.gz
>> could be installed on the platforms or supplied with ghc as a static
>> library. With libedit dynamically linked user programs will hardly
>> though, on non-macs.
* I don't think it is feasible to entirely drop readline from ghci (as
some widely used Linux distributions, eg, Fedora 7 and Solaris doesn't
support sufficiently recent versions of editline).
* We don't seem to want a package with a variant license plus might
have trouble specifying one with Cabal.
* The readline package stays as it is (stays GPL).
* We add the new editline package (as a boot package) including
Editline.Readline as the compatibility layer (is BSD3).
* GHC uses configure magic to pick editline when available and
* Any other software can, at their discretion, choose to support only
readline, or only editline, or use configure magic similar to GHC.
This is a bit of extra hassle, but that may be a good thing as it
forces developers to become aware of the licensing issues they get into.
Simon, what do you think?
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