[GHC] #8205: the 'impossible' happened : expectJust block_order

[GHC]

#8205: the 'impossible' happened : expectJust block_order
----------------------------------------+----------------------------------
        Reporter:  erikd                |            Owner:
            Type:  bug                  |           Status:  new
        Priority:  normal               |        Milestone:
       Component:  Compiler             |          Version:  7.7
      Resolution:                       |         Keywords:
Operating System:  Unknown/Multiple     |     Architecture:
 Type of failure:  Building GHC failed  |  Unknown/Multiple
       Test Case:                       |       Difficulty:  Unknown
        Blocking:                       |       Blocked By:
                                        |  Related Tickets:
----------------------------------------+----------------------------------

Comment (by jstolarek):

 Thanks for your `build.mk`. Unfortunately I can't reproduce this on my
 Linux machine - it seems that the problem only happens on Macs.

 > if I revert commit d61c3ac186c94021c851f7a2a6d20631e35fc1ba the stage1
 build completes and then fails during the stage2 build.

 This is most strange. If stage2 fails after reverting that commit this
 would mean that you are experiencing some other bug. Did you clean the
 build tree after reverting the commit? Also, how does stage2 fail? What
 error do you get?

 One thing you could do to help us in debugging this is trying to build
 HEAD and when you get a build failure, you could re-run the last command
 with `-ddump-cmm -dcmm-lint` added to the command line. So this would be
 something like this:

 {{{
 "inplace/bin/ghc-stage1" -hisuf dyn_hi -osuf  dyn_o -hcsuf dyn_hc -fPIC
 -dynamic
   -H32m -O -Werror -Wall -H64m -O0    -hide-all-packages -i -iutils/hpc/.
   -iutils/hpc/dist-install/build -iutils/hpc/dist-install/build/autogen
   -Iutils/hpc/dist-install/build -Iutils/hpc/dist-install/build/autogen
   -optP-include -optPutils/hpc/dist-install/build/autogen/cabal_macros.h
   -package array-0.4.0.2 -package base-4.7.0.0 -package containers-0.5.2.1
   -package directory-1.2.0.1 -package hpc-0.6.0.1 -XHaskell98 -XCPP
   -no-user-package-db -rtsopts -fwarn-tabs     -odir utils/hpc/dist-
 install/build
   -hidir utils/hpc/dist-install/build -stubdir utils/hpc/dist-
 install/build
   -c utils/hpc/dist-install/build/HpcParser.hs
   -o utils/hpc/dist-install/build/HpcParser.dyn_o -ddump-cmm -dcmm-lint
 }}}

 If you could upload output from this command this would tell us why this
 is happening.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8205#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler