Make -ddump-to-file truncate existing files.

[ghc-hetmet.git] / compiler / main / ErrUtils.lhs

diff --git a/compiler/main/ErrUtils.lhs b/compiler/main/ErrUtils.lhs
index b6297a2..1c7a389 100644 (file)
--- a/compiler/main/ErrUtils.lhs
+++ b/compiler/main/ErrUtils.lhs
@@ -41,6 +41,9 @@ import StaticFlags    ( opt_ErrorSpans )
 
 import System.Exit     ( ExitCode(..), exitWith )
 import Data.List
+import qualified Data.Set as Set
+import Data.IORef
+import Control.Monad
 import System.IO
 
 -- -----------------------------------------------------------------------------
@@ -208,19 +211,26 @@ mkDumpDoc hdr doc
 --     otherwise emit to stdout.
 dumpSDoc :: DynFlags -> DynFlag -> String -> SDoc -> IO ()
 dumpSDoc dflags dflag hdr doc
- = do  let mFile       = chooseDumpFile dflags dflag
-       case mFile of
-               -- write the dump to a file
-               --      don't add the header in this case, we can see what kind
-               --      of dump it is from the filename.
-               Just fileName
-                -> do  handle  <- openFile fileName AppendMode
-                       hPrintDump handle doc
-                       hClose handle
-
-               -- write the dump to stdout
-               Nothing
-                -> do  printDump (mkDumpDoc hdr doc)
+ = do let mFile = chooseDumpFile dflags dflag
+      case mFile of
+            -- write the dump to a file
+            -- don't add the header in this case, we can see what kind
+            -- of dump it is from the filename.
+            Just fileName
+                 -> do
+                        let gdref = generatedDumps dflags
+                        gd <- readIORef gdref
+                        let append = Set.member fileName gd
+                            mode = if append then AppendMode else WriteMode
+                        when (not append) $
+                            writeIORef gdref (Set.insert fileName gd)
+                        handle <- openFile fileName mode
+                        hPrintDump handle doc
+                        hClose handle
+
+            -- write the dump to stdout
+            Nothing
+                 -> printDump (mkDumpDoc hdr doc)
 
 
 -- | Choose where to put a dump file based on DynFlags