[GHC] #9657: I found a duplicate definition for symbol: __x86.get_pc_thunk.bx

[GHC]

#9657: I found a duplicate definition for symbol: __x86.get_pc_thunk.bx
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              Reporter:  nomeata     |            Owner:
                  Type:  bug         |           Status:  closed
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.6.3
            Resolution:  wontfix     |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:  Compile-    |       Blocked By:
  time crash                         |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by rwbarton):

 * status:  new => closed
 * resolution:   => wontfix


Comment:

 The ghci linker doesn't understand whatever magic gcc/binutils uses to
 deduplicate multiple `__x86.get_pc_thunk.bx` symbols. That's not too
 surprising, there's a lot of kinds of magic that the ghci linker doesn't
 understand and this is one of the reasons that in 7.8 ghci uses dynamic
 libraries by default.

 I don't think the library author should need to specify `-fpic` in `cc-
 options` though. Cabal should invoke ghc with `-shared` when building the
 C files for a dynamic Haskell library, and ghc should then invoke gcc with
 `-fPIC`.

 In fact I just tried removing `-fpic` from `vty.cabal` and building it in
 a sandbox with `--ghc-options=-v` and I see
 {{{
 /usr/bin/gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -O2 -O2 -x c \
 cbits/mk_wcwidth.c -o /tmp/ghc11196_0/ghc11196_1.s -fPIC -U__PIC__
 -D__PIC__ \
 -Wimplicit -S '-D__GLASGOW_HASKELL__=708' [....]
 }}}
 so it seems that Cabal and ghc are both doing the right thing, and the vty
 author can remove `-fpic`. Maybe submit a bug report there?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9657#comment:7>
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