readFile should fail when being asked to read a directory --
see 11.2 of the lib report where a file is defined as being
a non-directory fs object.
Re: green-card - you can reduce the likelihood of running
into this with Hugs98 by reversing 'default_suffixes' (as you
suggest.) You still want "" as an element, since you're not
required to give the .gc suffix when using %#include.
I've committed the one-line change.
--sigbjorn
> -----Original Message-----
> From: Carl R. Witty [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, May 31, 2000 22:53
> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: bug in ghc, hugs, or green-card
>
>
> As you can tell from the title, I'm not sure exactly where the
> responsibility for this bug lies.
>
> The symptom: green-card (running under hugs, with runhugs) fails when
> running in a project directory built with "ghc -split-objs".
>
> The cause: Green Card does import chasing; that is, when processing a
> file containing (say) "import GL_DIS", Green Card will try to find and
> process a corresponding Green Card file. It searches first for a
> file named "GL_DIS"; if that fails, it will search for "GL_DIS.gc".
>
> If this is in a directory which is being built using ghc with the
> "-split-objs" option, then there will be a directory named "GL_DIS".
>
> Consider the following program:
> > module Main where
> >
> > main = catch (do v <- readFile "/etc"; putStrLn ("Success: " ++ v))
> > (\_ -> putStrLn "Failed!")
>
> When run under Hugs, this prints "Success: ". When compiled with ghc,
> this prints "Failed!".
>
> This difference means that if Green Card is run under Hugs, and it
> tries to load the Green Card file corresponding to "import GL_DIS",
> and there is a directory named "GL_DIS", green-card will believe that
> this is an empty Green Card file, process it (with no effect, because
> it's empty; and with no warning or error, because it's present), and
> subsequently fail.
>
> So, the question is, "Should readFile on a directory throw an IO
> error?" If so, then there is a bug in Hugs; if not, there is a bug
> (or at least a severe misfeature) in Green Card (and a bug in the ghc
> libraries, which do throw an IO error).
>
> I couldn't find a definitive answer to this question in the Haskell 98
> report or library report (although I didn't spend too much time
> looking). My personal opinion is that it would be better if an IO
> error were thrown, so that Hugs should be changed; but that Green Card
> should not depend on this, so that the line:
>
> default_suffixes = ["","gc"]
>
> in GreenCard.lhs should be changed to
> default_suffixes = ["gc"]
> or
> default_suffixes = ["gc",""]
>
> In the meantime, a sufficient workaround is to add "--suffix=gc" to
> the green-card command line.
>
> Carl Witty
>
>
