[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:  watashi
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Driver            |              Version:  8.7
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15847, #12759    |  Differential Rev(s):  Phab:D5288
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"c98e25a4de88f12c6ded0a97fcf3ed8f4996b9ea/ghc"
 c98e25a4/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c98e25a4de88f12c6ded0a97fcf3ed8f4996b9ea"
 Explicitly pass -fno-PIC to C compiler on linux

 Recent gcc on some linux ditributions may have -fPIC on by default

 ```
 $ 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
 ```

 This results in following error for i686:

 ```
 $ TEST=T13366 make test
 ...
 c-iserv.bin:
 /home/watashi/github/ghc/libraries/ghc-prim/dist-install/build/HSghc-pri
 m-0.5.3.o:
 unknown symbol `_GLOBAL_OFFSET_TABLE_'
 ghc-stage2: unable to load package `ghc-prim-0.5.3'
 ...
 ```

 As our runtime linker doesn't support R_386_GOTPC relocations at all
 (#15847).
 Also while we don't have such problem on x86_64, it's not desired to
 build PIC objects either.

 Test Plan: `TEST=T13366 make test` passed on
 {rGHC82a716431cc680392e332bc2b1a1fd0d7faa4cd8}

 Reviewers: simonmar, bgamari, austin

 Reviewed By: simonmar

 Subscribers: rwbarton, carter

 GHC Trac Issues: #15848

 Differential Revision: https://phabricator.haskell.org/D5288
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15848#comment:2>
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