#7593: Unable to print exceptions of unicode identifiers -------------------------------------+------------------------------------- Reporter: dagit | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Windows | Architecture: Unknown/Multiple Type of failure: Incorrect | Difficulty: Unknown warning at compile-time | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): This issue affects both Win32 consoles (e.g., cmd.exe) and mintty consoles (e.g., Cygwin and MSYS), but in different ways. In mintty consoles, the issue is easily fixed by setting the encoding of the file handle to {{{utf8}}}: {{{

putStrLn "→" *** Exception: <stdout>: hPutChar: invalid argument (invalid character) import System.IO hSetEncoding stdout utf8 putStrLn "→" → getChar >>= putChar → Γ> getChar >>= putChar å> getChar >>= putChar Æ> getChar >>= putChar hSetEncoding stdin utf8 getChar >>= putChar → →> }}}

Fixing the issue on Win32 consoles is not as easy. One approach is to use the FFI to call the native API calls for Unicode output ([http://msdn.microsoft.com/en- us/library/windows/desktop/ms687401%28v=vs.85%29.aspx WriteConsoleW]) and input ([http://msdn.microsoft.com/en- us/library/windows/desktop/ms684961%28v=vs.85%29.aspx ReadConsoleInputW]). This is the approach that [https://github.com/judah/haskeline/blob/0f4ba2c51691f2031371c0bfadcd652abf57... haskeline] takes, and it seems to work well: {{{

import System.Console.Haskeline import Data.Maybe runInputT defaultSettings (getInputChar "") >>= runInputT defaultSettings . outputStrLn . (:[]) . fromJust → → }}}

-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7593#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler