[GHC] #15848: ghc builds cbits with -fPIC even when -fPIC is not passed to ghc on linux

[GHC]

#15848: ghc builds cbits with -fPIC even when -fPIC is not passed to ghc on linux
----------------------------------------+---------------------------------
           Reporter:  watashi           |             Owner:  (none)
               Type:  bug               |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  Driver            |           Version:  8.7
           Keywords:                    |  Operating System:  Linux
       Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:  #15847
Differential Rev(s):                    |         Wiki Page:
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 ghc assumes that on linux, C compiler (e.g. gcc) will build non-PIC object
 code when no `-fPIC` is passed. But this is no longer true for recent gcc
 version on some distributions. e.g.

 {{{
 $ uname -a
 Linux watashi-arch32 4.18.5-arch1-1.0-ARCH #1 SMP PREEMPT Tue Aug 28
 20:45:30 CEST 2018 i686 GNU/Linux
 $ gcc --version
 gcc (GCC) 7.3.1 20180312
 $ touch dummy.c
 $ gcc -Q -v dummy.c 2>&1 | grep PIC
 options enabled:  -fPIC -fPIE -faggressive-loop-optimizations
 }}}

 We need pass `-fno-PIC` explicitly just like `-no-pie`.

 In particular, this results in 300+ ext-interp related tests to fail on
 i386 when built with a gcc that has `-fPIC` on by default, as we don't
 support loading non-PIC .o built from .c on i386. (See #15847, fix this
 bug will mitigate #15847)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15848>
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