[GHC] #15338: ghc-pkg misbehaves after possible miscompilation on m68k and sh4

[GHC]

#15338: ghc-pkg misbehaves after possible miscompilation on m68k and sh4
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        Reporter:  glaubitz          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  m68k
 Type of failure:  Incorrect result  |            Test Case:
  at runtime                         |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by slyfox):

 Here is the minimal reproducer:

 {{{#!hs
 -- a.hs
 import System.IO

 main = do
     hSetBuffering stdout (BlockBuffering Nothing)
     hPutStrLn stdout "hello"
 }}}

 {{{
 $ ghc --make a.hs -O1 -dynamic
 $ ./a
 <no output>
 }}}

 Confirmed locally that:
 - broken: '''sh4''' and '''m68k'''
 - seem to work: '''x86_64''', '''mipsn32''', '''powerpc''',
 '''powerpc64''', '''sparc'''

 I have not got to the bottom of the bug yet but on the way there. Somehow
 flushStdHandles fails to flush stdout when (and only when) in full
 buffered mode.

 A few observations:
 - the trigger needs both '''-O1' and '''-dynamic'''
 - both '''sh4''' and '''m68k''' are arches with 2-byte instruction width

 I'll keep debugging.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15338#comment:3>
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