Problem with ghc on Windows ME

[Simon Marlow]

After Googling around a bit, I found this description of exactly how
Windows interprets command lines in the C runtime:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng
/htm/progs_12.asp

As you can see, the rules are indeed very strange, but they are
invertible.  I think this code should do the trick:

translate :: String -> String
translate str = '"' : snd (foldr escape (True,"\"") str)
  where escape '"'  (_,     str) = (True,  '\\' : '"'  : str)
        escape '\\' (True,  str) = (True,  '\\' : '\\' : str)
        escape '\\' (False, str) = (False, '\\' : str)
        escape c    (_,     str) = (False, c : str)

Cheers,
	Simon

> -----Original Message-----
> From: glasgow-haskell-users-bounces at haskell.org 
> [mailto:glasgow-haskell-users-bounces at haskell.org] On Behalf 
> Of Simon Marlow
> Sent: 29 January 2004 11:31
> To: Claus Reinke; Simon Peyton-Jones; 
> glasgow-haskell-users at haskell.org
> Subject: RE: Problem with ghc on Windows ME
> 
>  
> > So does that mean functionality has been lost in the move from
> > ghc-6.0.1?
> 
> No, the behaviour is improved in 6.2 because we're now 
> careful to escape
> quotes before passing the command-line to the operating system.
> 
> I think confusion has arisen because Simon pointed out that there's no
> way, on Windows, to pass this sequence of characters as an 
> argument to a
> command:
>   
>    \"
> 
> This is not entirely true, I just discovered that the 
> sequence \\\" will
> turn into \".  But in general, the sequence \\ does not turn into \.
> Windows' command-line quoting rules are highly mysterious, to say the
> least.
> 
> So the patch I posted is not complete.  It looks like rawSystem should
> additionally translate \" as \\\".
> 
> > Because that (on win98) happily accepts such useful
> > contraptions as
> > 
> >     System.Cmd.rawSystem "\"c:\\silly 
> > space\\Vim\\vim62\\gvim.exe\" --servername GVIM --remote-send
> > \":echo \\\"hi \\\\\\\" there\\\"<cr>\"" >>= print
> 
> The idea is that you should pass to rawSystem *exactly* the 
> command and
> arguments you want to run, with no quoting except that required by the
> Haskell lexical syntax.  You'll notice that rawSystem now takes the
> command and list of arguments separately in 6.2.  The 
> implementation of
> rawSystem will attempt to compensate for the internal translation that
> Windows does on the command-line; on Unix no translation is necessary.
> So clients of rawSystem should be more portable, because they 
> don't have
> to know about quoting that happens under the hood.
> 
> Your example will probably work once it's reformulated for 
> 6.2's version
> of rawSystem, and once we fix rawSystem in light of the \\\" hack I
> discovered above.
> 
> Cheers,
> 	Simon
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