[Haskell-cafe] Cabal Compiler Flag Problem

Ben Derrett ben.derrett at googlemail.com
Wed Mar 24 01:26:02 EDT 2010

I'm trying to install the Haskell cgi module, as per here
http://passingcuriosity.com/2009/haskell-fastcgi-with-apache/. When I type
cabal install cgi, I get the following error (on a Fedora instance):

cabal install cgi
Resolving dependencies...
Configuring MonadCatchIO-mtl-
Preprocessing library MonadCatchIO-mtl-
Building MonadCatchIO-mtl-
[1 of 1] Compiling Control.Monad.CatchIO ( Control/Monad/CatchIO.hs,
dist/build/Control/Monad/CatchIO.o )

    Illegal signature in pattern: E.SomeException
        Use -XPatternSignatures to permit it
cabal: Error: some packages failed to install:
MonadCatchIO-mtl- failed during the building phase. The exception
exit: ExitFailure 1
cgi-3001.1.8 depends on MonadCatchIO-mtl- which failed to install.

So, I modified my /root/.cabal/config with:
-- flags: -XPatternSignatures

This doesn't seem to resolve the problem. What do I need to do to change the
compiler flags?


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