[project @ 2004-02-24 12:39:12 by simonmar]

New version of translate for mingw32, which correctly (allegedly)
reverses the command-line translation done by the standard C runtime
on Windows.

diff --git a/System/Cmd.hs b/System/Cmd.hs
index 78d3b28..41fabb2 100644 (file)
--- a/System/Cmd.hs
+++ b/System/Cmd.hs
@@ -203,9 +203,24 @@ rawSystem cmd args = do
 
 translate :: String -> String
 translate str@('"':_) = str -- already escaped.
-translate str = '"' : foldr escape "\"" str
-  where escape '"'  str = '\\' : '"'  : str
-       escape c    str = c : str
+       -- ToDo: this case is wrong.  It is only here because we
+       -- abuse the system in GHC's SysTools by putting arguments into
+       -- the command name; at some point we should fix it up and remove
+       -- the case above.
+translate str = '"' : snd (foldr escape (True,"\"") str)
+  where escape '"'  (b,     str) = (True,  '\\' : '"'  : str)
+        escape '\\' (True,  str) = (True,  '\\' : '\\' : str)
+        escape '\\' (False, str) = (False, '\\' : str)
+       escape c    (b,     str) = (False, c : str)
+       -- This function attempts to invert the Microsoft C runtime's
+       -- quoting rules, which can be found here:
+       --     http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/progs_12.asp
+       -- (if this URL stops working, you might be able to find it by
+       -- searching for "Parsing C Command-Line Arguments" on MSDN).
+       --
+       -- The Bool passed back along the string is True iff the
+       -- rest of the string is a sequence of backslashes followed by
+       -- a double quote.
 
 foreign import ccall unsafe "rawSystem"
   c_rawSystem :: CString -> IO Int