[Haskell-cafe] unknown flags scramble

Evan Laforge qdunkan at gmail.com
Wed Aug 20 16:15:55 EDT 2008

I've been getting a mysterious error for a while now.  It's come and
gone, but seems to be showing up slightly more consistently now.
Before I was on ghc 6.8.2 and now I'm on ghc 6.8.3, OS X 10.4 and now
10.5, i386 arch.  The problem is that randomly while compiling I get
an error like this:

    unknown flags in  {-# OPTIONS #-} pragma:
-XDeriveDataTypeabl<Data/Array/IArray.hs" #<e Ui.Font ( TextStyle(..),
Font(..), FontFace(..) ) where import qualified Data.Generics as
<Data/Array/IArray.lhs.L<array-<Color as Color import
Foreign import qualified Ui.Util as Util {-# LINE 14 "Ui/Font.hsc"

It looks like somehow pragma parsing gets a bunch of random junk
scrambled in.  In the past this would happen consistently until I did
a make clean and rebuild, but more recently all I have to do is try
again and it doesn't happen the second time.  I haven't gotten it
while compiling for a while, but since I'm using hint which uses the
ghc api to interpret haskell, I'm getting this quite frequently inside
a GhcException when hint wants to interpret some code.  I've also
gotten this from ghci occasionally, and the usual fix is just to do a
reload, and the second time it works.

Does this sound familiar to anyone?  It's not fatal since a retry
clears things up, but it's a little worrying and would not look very
good in released software.  I cast about a bit on the ghc trac and
didn't find any open bugs like this.

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