[GHC] #11587: Place shared objects in LIBDIR

[GHC]

#11587: Place shared objects in LIBDIR
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Package system    |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by chak):

 * cc: trommler (removed)
 * cc: Trommler, chak (added)


Comment:

 I have wondered about this set up in the past. More precisely, I think
 having the dynamic libraries for different packages in separate
 directories with the interface files etc of the package makes a lot of
 sense. I keeps the `$LIBDIR` tidy.

 However, the dynamic linking set up does appear to be rather inefficient
 and, at least on OS X, it makes relocating GHC distributions very hard. In
 the Haskell for Mac build, I hence, post-process all executables and
 dynamic libraries to optimise the linking process. As my ELF is a bit
 rusty let me explain it in MACH-O terms. I am setting the `RPATH` in all
 executables such that it points to `$LIBDIR` and I set the library name of
 each dynamic library to include the package directory. For example, for
 `base`, we might have `base_GDytRqRVSUX7zckgKqJjgw/libHSbase-4.8.1.0
 -GDytRqRVSUX7zckgKqJjgw-ghc7.10.2.dylib`.

 I also set `RPATH` to be relative to `@loader_PATH`, which gives me a
 relocatable set of dynamic libraries and GHC executables.

 So, for example, here is what `base` looks like

 {{{
 LC 03: LC_ID_DYLIB
 @rpath/base_GDytRqRVSUX7zckgKqJjgw/libHSbase-4.8.1.0
 -GDytRqRVSUX7zckgKqJjgw-ghc7.10.2.dylib
 ...
 LC 12: LC_LOAD_DYLIB            @rpath/integ_2aU3IZNMF9a7mQ0OzsZ0dS
 /libHSinteger-gmp-1.0.0.0-2aU3IZNMF9a7mQ0OzsZ0dS-ghc7.10.2.dylib
 LC 13: LC_LOAD_DYLIB            @rpath/ghcpr_8TmvWUcS1U1IKHT0levwg3
 /libHSghc-prim-0.4.0.0-8TmvWUcS1U1IKHT0levwg3-ghc7.10.2.dylib
 ...
 LC 19: LC_RPATH                 @loader_path/..
 }}}

 This avoids the quadratic explosion of the search space, but still keeps
 the dynamic libraries in the package directories (and `$LIBDIR` tidier).
 This is definitely the better set up on OS X. Can't we do something
 equivalent on Linux?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11587#comment:4>
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