[GHC] #13030: Build error from following default nixos instructions and -Werror

[GHC]

#13030: Build error from following default nixos instructions and -Werror
-------------------------------------+-------------------------------------
           Reporter:  mpickering     |             Owner:
               Type:  bug            |            Status:  new
           Priority:  lowest         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 When building the RTS with the nixos instructions from the wiki
 (https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Linux#NixNixOS)
 if you enable `Werror` then the build fails with warnings from the rts.

 For example

 {{{
 rts/Interpreter.c: In function ‘interpretBCO’:
 rts/Interpreter.c:593:41: error:
      warning: ‘obj’ may be used uninitialized in this function [-Wmaybe-
 uninitialized]
                   debugBelch("Returning: "); printObj(obj);
 }}}

 Is this something I should worry about? Are there additional flags that I
 should pass to gcc in order to turn these warnings off?

 The workaround is compile without `-Werror` and then turn it on once the
 `rts` has been compiled.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13030>
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