[GHC] #15338: ghc-pkg misbehaves after possible miscompilation on m68k and sh4

[GHC]

#15338: ghc-pkg misbehaves after possible miscompilation on m68k and sh4
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        Reporter:  glaubitz          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  m68k
 Type of failure:  Incorrect result  |            Test Case:
  at runtime                         |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by slyfox):

 Replying to [comment:3 slyfox]:
 > I'll keep debugging.

 I think I understand breakage mechanics now:

 The example above breaks because '''stdout''' haskell closure is evaluated
 twice:
 - once in the test binary
 - once in shared library

 and creates two objects. '''hFlush''' is called only for second (shared
 library) object because it is called from there.

 Duplication happens because '''base_GHCziIOziHandleziFD_stdout_closure'''
 (closure behind '''System.IO.stdout''' object) is copied by the linker
 '''COPY''' relocation:
 {{{
 $ objdump -R -D bug/ghc-pkg

 00415248 <base_GHCziIOziHandleziFD_stdout_closure>:
         ...
                         415248: R_SH_COPY
 base_GHCziIOziHandleziFD_stdout_closure
 }}}

 It should be just an external reference like '''R_SH_GLOB_DAT''' instead.

 Normally '''COPY''' relocations are used only for immutable ('''const'''
 in C land) data. But '''_closure'''s are mutable. I'll double-check
 generated C code and file a toolchain bug upstream.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15338#comment:4>
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