[project @ 2001-10-26 05:31:05 by sof]

pipeLoop: Handle pipelines that end with ineffective
final stages (e.g., CPP and/or PP) correctly. i.e.,
need to copy the outcome of the pipeline into the
expected output file, since the final stage didn't.

diff --git a/ghc/compiler/main/DriverPipeline.hs b/ghc/compiler/main/DriverPipeline.hs
index 0e8c898..ec85815 100644 (file)
--- a/ghc/compiler/main/DriverPipeline.hs
+++ b/ghc/compiler/main/DriverPipeline.hs
@@ -33,7 +33,7 @@ import DriverUtil
 import DriverMkDepend
 import DriverPhases
 import DriverFlags
-import SysTools                ( newTempName, addFilesToClean, getSysMan )
+import SysTools                ( newTempName, addFilesToClean, getSysMan, copy )
 import qualified SysTools      
 import HscMain
 import Finder
@@ -285,7 +285,21 @@ pipeLoop (all_phases@((phase, keep, o_suffix):phases))
              ofile <- outputFileName True keep final_suffix
              return (ofile, final_suffix)
           -- carry on ...
-       Just fn -> 
+       Just fn -> do
+               {-
+                 Check to see whether we've reached the end of the
+                 pipeline, but did so with an ineffective last stage.
+                 (i.e., it returned the input_fn as the output filename).
+                 
+                 If we did and the output is persistent, copy the contents
+                 of input_fn into the file where the pipeline's output is
+                 expected to end up.
+               -}
+             atEnd <- finalStage (null phases)
+             when (atEnd && fn == input_fn)
+                  (copy "Saving away compilation pipeline's output"
+                        input_fn
+                        output_fn)
               {-
               Notice that in order to keep the invariant that we can
               determine a compilation pipeline's 'start phase' just
@@ -306,9 +320,14 @@ pipeLoop (all_phases@((phase, keep, o_suffix):phases))
               pipeLoop phases (fn, o_suffix) do_linking use_ofile
                                orig_basename orig_suffix
   where
+     finalStage lastPhase = do
+       o_file <- readIORef v_Output_file
+       return (lastPhase && not do_linking && use_ofile && isJust o_file)
+
      outputFileName last_phase keep suffix
        = do o_file <- readIORef v_Output_file
-            if last_phase && not do_linking && use_ofile && isJust o_file
+            atEnd  <- finalStage last_phase
+            if atEnd
               then case o_file of 
                       Just s  -> return s
                       Nothing -> error "outputFileName"