[Haskell-cafe] Cabal bug? (was Re: Cabal: --enable-shared and executables)

[Magnus Therning]

On Sun, Nov 03, 2013 at 05:05:40PM -0500, Albert Y. C. Lai wrote:
> On 13-11-03 01:46 AM, Magnus Therning wrote:
>>Is there already a way to get Cabal to put in an RPATH such that an
>>*installed* executable works correctly, or is this a fairly serious
>>bug in Cabal?
> 
> It is usually desirable to set RPATH to libs' installation locations
> rather than libs' build trees, and I think I prefer it too. But the
> exception is during "cabal test", when you should test against libs
> in the build tree. It is somewhat a dilemma.

Indeed, that is a bit of a problem.  However, I'd argue that
/installation/ of a package is the scenario to make as simple as
possible.  Forcing the use of LD_LIBRARY_PATH in order to run `cabal
test` is much more acceptable to me than forcing its use to run an
installed executable.

> It is, in fact, sad that we have to set RPATH at all, and we have to
> because Haskell libs are not common, and they are not dumped
> directly into /usr/lib and /usr/local/lib. (They are, instead,
> scattered over /usr/local/lib/p-n/ghc-m, for wide ranges of values
> of p, n, and m.) If not for this, we would set no RPATH, we would do
> nothing special for installations, and we just had to play with
> LD_LIBRARY_PATH or LD_RUN_PATH or something during testing.
> 
> (I would, in fact, not mind that organization, if symlinks were set
> up directly in /usr/local/lib. Note: the filename is already
> libHSp-n-ghcm.so, it already records p, n, and m, there is no clash
> putting that name right into /usr/local/lib alongside siblings and
> cousins --- well, no more clash than the /usr/local/lib/p-n/ghc-m
> scheme.)

We have have been considering a scheme like this when packaging for
Arch Haskell (inofficial packages for Arch Linux).  Something along
the lines of putting symlinks in /usr/lib/ghc-7.6.3/ and then drop a
file in /etc/ld.so.conf.d/ that adds it to the runtime linker's search
path.

/M

-- 
Magnus Therning                      OpenPGP: 0xAB4DFBA4 
email: magnus at therning.org   jabber: magnus at therning.org
twitter: magthe               http://therning.org/magnus

The day after tomorrow is the third day of the rest of your life.
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