[GHC] #4471: Incorrect Unicode output on Windows Console

[GHC]

#4471: Incorrect Unicode output on Windows Console
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    Reporter:  sankeld   |        Owner:                             
        Type:  bug       |       Status:  new                        
    Priority:  normal    |    Milestone:  7.2.1                      
   Component:  Compiler  |      Version:  6.12.3                     
    Keywords:            |     Testcase:                             
   Blockedby:            |   Difficulty:                             
          Os:  Windows   |     Blocking:                             
Architecture:  x86       |      Failure:  Incorrect result at runtime
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Comment(by simonmar):

 That does clarify things a lot, thanks for that.  To summarise:

  * the bug is that Win32 `WriteFile()` returns the wrong result when
 writing to a Console in codepage 65001.  Furthermore, the result it
 actually returns is the number of characters written to the console, which
 depends on the actual ''font'' being used! (if the font doesn't have the
 required Unicode glyph, it falls back to outputting characters
 corresponding to the raw UTF-8 bytes).

 The only way to work around the bug seems to be to use `WriteConsole()`
 and write Unicode characters directly.  If a Handle is attached to a
 console, then all writes must be decoded from the codepage encoding to
 UTF-16 before being written using `WriteConsole()`.  Even better would be
 to bypass the codepage encoding entirely and encode directly from UTF-32
 to UTF-16 in the IO library.  None of this is particularly easy, though.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4471#comment:12>
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