[GHC] #10822: GHC inconsistently handles \\?\ for long paths on Windows

[GHC]

#10822: GHC inconsistently handles \\?\ for long paths on Windows
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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:  Unknown/Multiple
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
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Comment (by dobenour):

 CoreCLR ran into the same problem and fixed it by adding the {{{\\?\}}}
 prefix to any overlong path, after making the path absolute with the
 {{{GetFullPathNameW}}} function in the Windows API.  For UNC paths (that
 begin with {{{\\}}} but not with {{{\\?\}}}), the solution is to replace
 {{{\\}}} with {{{\\?\UNC\}}}.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10822#comment:1>
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