[GHC] #10762: On Windows, out-of-codepage characters can cause GHC build to fail

[GHC]

#10762: On Windows, out-of-codepage characters can cause GHC build to fail
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        Reporter:  snoyberg      |                   Owner:
            Type:  bug           |                  Status:  new
        Priority:  normal        |               Milestone:
       Component:  Compiler      |                 Version:  7.10.2
      Resolution:                |                Keywords:
Operating System:  Windows       |            Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |               Test Case:
      Blocked By:                |                Blocking:
 Related Tickets:  #6037         |  Differential Revisions:
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Comment (by snoyberg):

 After this discussion, here's the proposal I'd make, which is a libraries
 change, not just a GHC-internal change:

 * The default filesystem encoding will always be UTF-8, regardless of
 environment variables or codepage
 * We modify the encoding logic on Windows to also respect an environment
 variable (perhaps LANG, not sure) to override the codepage for
 stdin/stdout/stderr character encoding

 One I'm on the fence about:

 * Modify the character encoding codepaths to not throw an exception on an
 unhandled character when using the default encoding for
 stdin/stdout/stderr. This would be nice in that GHC wouldn't die on
 printing a warning if the codepage/LANG variable is set to something
 unusual, but does have the property of just swallowing problematic
 behavior.

 I'm fairly certain that will solve the major problems we have with GHC,
 and will fit the stack use case nicely. Does anyone else reading see a
 problem with this approach before I bring it up with the core libraries
 committee?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10762#comment:7>
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