[GHC] #8859: import conditionalization in System.Posix.Files.Common is wrong

[GHC]

#8859: import conditionalization in System.Posix.Files.Common is wrong
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       Reporter:  rwbarton          |             Owner:
           Type:  bug               |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  libraries/unix    |           Version:  7.8.1-rc2
       Keywords:                    |  Operating System:  Other
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 `System/Posix/Files/Common.hsc` imports `Data.Int` and `Data.Ratio`
 conditionally, to avoid "unused import" compiler warnings:

 {{{
 #if defined(HAVE_STRUCT_STAT_ST_CTIM) || \
     defined(HAVE_STRUCT_STAT_ST_MTIM) || \
     defined(HAVE_STRUCT_STAT_ST_ATIM) || \
     defined(HAVE_STRUCT_STAT_ST_ATIMESPEC) || \
     defined(HAVE_STRUCT_STAT_ST_MTIMESPEC) || \
     defined(HAVE_STRUCT_STAT_ST_CTIMESPEC)
 import Data.Int
 import Data.Ratio
 #endif
 }}}

 but those modules are actually used in functions like

 {{{
 accessTimeHiRes (FileStatus stat) =
   unsafePerformIO $ withForeignPtr stat $ \stat_ptr -> do
     sec  <- (#peek struct stat, st_atime) stat_ptr :: IO EpochTime
 #ifdef HAVE_STRUCT_STAT_ST_ATIM
     nsec <- (#peek struct stat, st_atim.tv_nsec) stat_ptr :: IO (#type
 long)
     let frac = toInteger nsec % 10^(9::Int)
 #elif HAVE_STRUCT_STAT_ST_ATIMESPEC
     nsec <- (#peek struct stat, st_atimespec.tv_nsec) stat_ptr :: IO
 (#type long)
     let frac = toInteger nsec % 10^(9::Int)
 #elif HAVE_STRUCT_STAT_ST_ATIMENSEC
     nsec <- (#peek struct stat, st_atimensec) stat_ptr :: IO (#type long)
     let frac = toInteger nsec % 10^(9::Int)
 #elif HAVE_STRUCT_STAT_ST_ATIME_N
     nsec <- (#peek struct stat, st_atime_n) stat_ptr :: IO (#type int)
     let frac = toInteger nsec % 10^(9::Int)
 #elif HAVE_STRUCT_STAT_ST_UATIME
     usec <- (#peek struct stat, st_uatime) stat_ptr :: IO (#type int)
     let frac = toInteger usec % 10^(6::Int)
 #else
     let frac = 0
 #endif
     return $ fromRational $ toRational sec + frac
 }}}

 so there should be additional tests for
 `defined(HAVE_STRUCT_STAT_ST_ATIMENSEC)`,
 `defined(HAVE_STRUCT_STAT_ST_ATIME_N)`, ... (15 total).

 Or, maybe there's a better alternative, since this is very long-winded and
 fragile...

 This breaks the build on Android, which has `st_atimensec`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8859>
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