[GHC] #8713: Avoid libraries if unneeded (librt, libdl, libpthread)

[GHC]

#8713: Avoid libraries if unneeded (librt, libdl, libpthread)
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              Reporter:  ip1981      |            Owner:
                  Type:  bug         |           Status:  upstream
              Priority:  normal      |        Milestone:
             Component:  GHCi        |          Version:  7.6.3
            Resolution:              |         Keywords:
      Operating System:  Other       |     Architecture:  x86_64 (amd64)
       Type of failure:  GHCi crash  |       Difficulty:  Moderate (less
             Test Case:              |  than a day)
              Blocking:              |       Blocked By:
Differential Revisions:              |  Related Tickets:
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Comment (by ip1981):

 Hi, this changes won't affect solaris. The patch make GHC only check
 whether we need libdl or libpthread. If not it will not load them. On
 Solaris libdl is a filter library. It exists only for backward
 compatibility. dlopen() function really is not even in libc, but in
 runtime linker ld.so.

 As for Dyson hack:

 I use GNU binutils.

 I had linker (GNU ld) problems when linking filter libraries, e. g.
 symbols versions mismach or so, can't remember. In come cases I was not
 able to link libpthread.so or librt.so. But on Solaris, illumos and Dyson
 I don't need to, because all functions are in libc (ld.so)

 Unfortunately, many (== almost all ;-) packages does not check whether
 they need these libraries, some of packages link them unconditionally, e.
 g. gcc -ldl -lpthread, etc.

 So instead of using real symlinks like libdl.so -> libdl.so.1, I made
 libdl.so be a file with [GNU] linker script with does nothing. Thus every
 package is happy finding these libs, and I don't have linking errors.

 In the ideal world GHC should load real library, not a developer symlink,
 e. i. libdl.so.1 instead of just libdl.so.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8713#comment:9>
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