From: Eric Bavier <ericbavier@openmailbox.org>
To: Federico Beffa <beffa@ieee.org>
Cc: Guix-devel <guix-devel@gnu.org>, federico.beffa@gmail.com
Subject: Re: [PATCH 0/2] native-search-paths for GHC
Date: Wed, 07 Oct 2015 16:27:11 -0500 [thread overview]
Message-ID: <de8e0cc2e54f6b640d4a4930e17bff81@openmailbox.org> (raw)
In-Reply-To: <CAKrPhPNBejn+1yqNwqWDSmPFwDKJOaEGjsftWCLeqfkcCu=V0g@mail.gmail.com>
On 2015-10-07 11:07, Federico Beffa wrote:
> ericbavier@openmailbox.org writes:
>
>> From: Eric Bavier <bavier@member.fsf.org>
>>
>> The first of these patches lets search-path-as-list function correctly
>> when a
>> pattern is given and the 'directory file type is specified.
>>
>> The second adds a native-search-paths field to our ghc package. It
>> modifies
>> our haskell-build-system to install a package-specific package
>> database with
>> each haskell library. GHC insists on a binary package cache file
>> called
>> 'package.cache' to be in each directory listed in GHC_PACKAGE PATH, so
>> we
>> uniquely name the package database directories, and use a file-pattern
>> to add
>> those to GHC_PACKAGE_PATH.
>>
>> The benefit of this over the current situation is that one gets the
>> benefit of
>> `guix package --search-paths`. Currently, after installing ghc
>> packages, the
>> user needs to know to manually add
>> ~/.guix-profile/lib/ghc-7.8.4/package.conf.d to their
>> GHC_PACKAGE_PATH. GHC
>> package recipes would no longer need to propagate runtime
>> dependencies, and
>> 'guix environment' also works nicely out-of-the-box::
>>
>> $ guix environment --ad-hoc ghc ghc-attoparsec
>> $ ghc-pkg list
>> /gnu/store/...-ghc-mtl-2.1.3.1/lib/ghc-7.8.4/ghc-mtl-2.1.3.1.conf.d
>> base-4.7.0.2
>> ghc-prim-0.3.1.0
>> integer-gmp-0.5.1.0
>> mtl-2.1.3.1
>> rts-1.0
>> transformers-0.3.0.0
>> /gnu/store/...-ghc-regex-base-0.93.2/lib/ghc-7.8.4/ghc-regex-base-0.93.2.conf.d
>> array-0.5.0.0
>> base-4.7.0.2
>> bytestring-0.10.4.0
>> ...
>> /gnu/store/4vvmngz1w8ccm7v7mk4f4dxk45834464-ghc-attoparsec-0.13.0.0/lib/ghc-7.8.4/ghc-attoparsec-0.13.0.0.conf.d
>> array-0.5.0.0
>> attoparsec-0.13.0.0
>> ...
>>
>> Though, as you can see in this example, libraries may be listed more
>> than
>> once. As far as I can tell at this point, that is just an aesthetic
>> detail.
>>
>> Future work might involve filtering build-only library dependencies
>> from the
>> generated package database. We could probably also remove the ghc
>> package
>> database creation during profile generation.
>>
>> I'd be interested in hearing others' thoughts on this approach.
>
> Hi Eric,
>
> sounds like a good approach to work around the "package.cache" clash. I
> have a couple of questions:
>
> * If I understand correctly, the configuration files of dependencies
> are
> copied in a unique directory for each package. Instead of copying
> would a symlink work? (There are literally thousands of packages on
> Hackage and hopefully Guix will get more of them.)
I don't know if symlinking is allowed across store directories, though
if it is, that'd be something to try.
> * Some Haskell libraries have a rather large list of dependencies. For
> this reason I can imagine that in some situations GHC_PACKAGE_PATH
> could grow rather long.
Not every package would end up with an entry in GHC_PACKAGE_PATH, only
those that are installed, or declared inputs. Dependent libraries would
be found when GHC examines the package databases of those packages.
> This thought made me wonder if there is a
> maximum length to the value of environment variables that we could
> possibly hit.
We've already pushed this quite far. E.g. the hydra package creates a
rather sizable PER5LIB path.
--
`~Eric
next prev parent reply other threads:[~2015-10-07 21:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-07 16:07 [PATCH 0/2] native-search-paths for GHC Federico Beffa
2015-10-07 21:27 ` Eric Bavier [this message]
2015-10-08 12:00 ` Ludovic Courtès
-- strict thread matches above, loose matches on Subject: below --
2015-10-06 21:26 ericbavier
2015-10-16 13:35 ` Eric Bavier
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