Avoid unsafePerformIO for getProgName

getProgName was used to append the name of the program (e.g. "ghc") to
printed error messages in the Show instance of GhcException. It doesn't
belong here as GHCi and GHC API users may want to override this behavior
by setting a different error handler. So we now call it in the
defaultErrorHandler instead.

1 files changed, 6 insertions, 4 deletions

diff --git a/ghc/Main.hs b/ghc/Main.hs
index bda5cd9ef9..ad975d1840 100644
--- a/ghc/Main.hs
+++ b/ghc/Main.hs
@@ -762,11 +762,13 @@ showUsage ghci dflags = do
   let usage_path = if ghci then ghciUsagePath dflags
                            else ghcUsagePath dflags
   usage <- readFile usage_path
-  dump usage
+  progName <- getProgName
+  dump progName usage
   where
-     dump ""          = return ()
-     dump ('$':'$':s) = putStr progName >> dump s
-     dump (c:s)       = putChar c >> dump s
+    dump progName xs = case xs of
+      ""        -> return ()
+      '$':'$':s -> putStr progName >> dump progName s
+      c:s       -> putChar c >> dump progName s
 
 dumpFinalStats :: Logger -> IO ()
 dumpFinalStats logger = do