Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC

Commits:

• 9788c0ec
  by Cheng Shao at 2026-01-21T16:10:24-05:00

  ghci: print external interpreter trace messages to stderr instead of stdout
  
  This patch makes ghci print external interpreter trace messages to
  stderr instead of stdout, which is a much saner choice for diagnostic
  information. Closes #26807.
  

1 changed file:

• libraries/ghci/GHCi/Server.hs

Changes:

 import Text.Printf

 import System.Environment (getProgName, getArgs)

 import System.Exit

+import System.IO

 type MessageHook = Msg -> IO Msg

 trace :: String -> IO ()

-trace s = getProgName >>= \name -> printf "[%20s] %s\n" name s

+trace s = getProgName >>= \name -> hPrintf stderr "[%20s] %s\n" name s

 serv :: Bool -> MessageHook -> Pipe -> (forall a .IO a -> IO a) -> IO ()

 serv verbose hook pipe restore = loop