[GHC] #15729: Static GHCi can segfault when accessing .bss section in C

[GHC]

#15729: Static GHCi can segfault when accessing .bss section in C
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           Reporter:  watashi         |             Owner:  (none)
               Type:  bug             |            Status:  new
           Priority:  normal          |         Milestone:
          Component:  GHCi            |           Version:  8.6.1
           Keywords:                  |  Operating System:  Linux
       Architecture:  x86_64 (amd64)  |   Type of failure:  GHCi crash
          Test Case:                  |        Blocked By:
           Blocking:                  |   Related Tickets:
Differential Rev(s):                  |         Wiki Page:
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 When an object file is statically linked, GHCi can return junk or segfault
 when trying to access data defined in .bss section via foreign call.

 {{{
 watashi % ~/gao/ghc/inplace/bin/ghc-stage2 --info | grep Dynamic
  ,("Dynamic by default","NO")
  ,("GHC Dynamic","NO")
 watashi % cat bss.c
 int read_bss(int i) {
   static int bss[1 << 20];
   return bss[i];
 }
 watashi % ~/gao/ghc/inplace/bin/ghc-stage2 --interactive test.o
 GHCi, version 8.7.20180920: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/watashi/.ghci
 Prelude> :m + Foreign Foreign.C
 Prelude Foreign Foreign.C> foreign import ccall unsafe "read_bss" read_bss
 :: Int -> IO Int
 Prelude Foreign Foreign.C> read_bss 0
 4294059519
 Prelude Foreign Foreign.C> read_bss 1
 65535
 Prelude Foreign Foreign.C> mapM (read_bss . bit) [0 .. 19]
 zsh: segmentation fault (core dumped)  ~/gao/ghc/inplace/bin/ghc-stage2
 --interactive test.o
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15729>
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