When the pipeline just copies the file, prepend a LINE pragma

For example, "ghc -E Foo.hs -o Foo.bar" just copies Foo.hs to
Foo.bar.  This patch adds a LINE pragma to the beginning of Foo.bar so
that further processing can track the location of the original file.

The motiviation for this is bug #1044.  When generating Haddock docs,
we preprocess the .hs to a .raw-hs, sometimes this doesn't involve any
actual preprocessing and in those cases we lose track of the original
filename.

diff --git a/compiler/main/DriverPipeline.hs b/compiler/main/DriverPipeline.hs
index 59f0721..1ee2924 100644 (file)
--- a/compiler/main/DriverPipeline.hs
+++ b/compiler/main/DriverPipeline.hs
@@ -29,7 +29,7 @@ module DriverPipeline (
 import Packages
 import HeaderInfo
 import DriverPhases
-import SysTools                ( newTempName, addFilesToClean, copy )
+import SysTools
 import qualified SysTools      
 import HscMain
 import Finder
@@ -442,17 +442,19 @@ runPipeline stop_phase dflags (input_fn, mb_phase) output maybe_loc
   -- Sometimes, a compilation phase doesn't actually generate any output
   -- (eg. the CPP phase when -fcpp is not turned on).  If we end on this
   -- stage, but we wanted to keep the output, then we have to explicitly
-  -- copy the file.
+  -- copy the file, remembering to prepend a {-# LINE #-} pragma so that
+  -- further compilation stages can tell what the original filename was.
   case output of
     Temporary -> 
        return (dflags', output_fn)
     _other ->
        do final_fn <- get_output_fn dflags' stop_phase maybe_loc
-          when (final_fn /= output_fn) $
-                 copy dflags ("Copying `" ++ output_fn ++ "' to `" ++ final_fn
-                       ++ "'") output_fn final_fn
+          when (final_fn /= output_fn) $ do
+              let msg = ("Copying `" ++ output_fn ++"' to `" ++ final_fn ++ "'")
+                  line_prag = Just ("{-# LINE 1 \"" ++ input_fn ++ "\" #-}\n")
+             copyWithHeader dflags msg line_prag output_fn final_fn
           return (dflags', final_fn)
-               
+
 
 
 pipeLoop :: DynFlags -> Phase -> Phase 

diff --git a/compiler/main/SysTools.lhs b/compiler/main/SysTools.lhs
index e44ed6d..9885b8d 100644 (file)
--- a/compiler/main/SysTools.lhs
+++ b/compiler/main/SysTools.lhs
@@ -19,7 +19,8 @@ module SysTools (
        runMkDLL,
 
        touch,                  -- String -> String -> IO ()
-       copy,                   -- String -> String -> String -> IO ()
+       copy,
+        copyWithHeader,
        normalisePath,          -- FilePath -> FilePath
        
        -- Temporary-file management
@@ -469,15 +470,21 @@ touch :: DynFlags -> String -> String -> IO ()
 touch dflags purpose arg =
   runSomething dflags purpose (pgm_T dflags) [FileOption "" arg]
 
-copy :: DynFlags -> String -> String -> String -> IO ()
-copy dflags purpose from to = do
+copy :: DynFlags -> String -> FilePath -> FilePath -> IO ()
+copy dflags purpose from to = copyWithHeader dflags purpose Nothing from to
+
+copyWithHeader :: DynFlags -> String -> Maybe String -> FilePath -> FilePath
+               -> IO ()
+copyWithHeader dflags purpose maybe_header from to = do
   showPass dflags purpose
 
   h <- openFile to WriteMode
   ls <- readFile from -- inefficient, but it'll do for now.
                      -- ToDo: speed up via slurping.
+  maybe (return ()) (hPutStr h) maybe_header
   hPutStr h ls
   hClose h
+
 \end{code}
 
 %************************************************************************