In short: I can't cabal install xmonad-contrib. Longer version: It a appears that a program which does not exist on my computer seems to insist on a package version which does not exist in my universe, I'm starting to wonder whether I have lost my marbles. Could some kind soul please point me in some sensible direction? cabal install xmonad-contrib Resolving dependencies... Configuring X11-xft-0.3... cabal: pkg-config version >=0.9.0 is required but it could not be found. cabal: Error: some packages failed to install: X11-xft-0.3 failed during the configure step. The exception was: ExitFailure 1 xmonad-contrib-0.9.1 depends on X11-xft-0.3 which failed to install. cabal install x11-xft Resolving dependencies... Configuring X11-xft-0.3... cabal: pkg-config version >=0.9.0 is required but it could not be found. cabal: Error: some packages failed to install: X11-xft-0.3 failed during the configure step. The exception was: ExitFailure 1 X11-xft version 0.9.0 doesn't even exist, as far a I can tell: 0.3 seems to be the highest. So what is making cabal believe that such a version is needed? Is it pkg-config? I'm not at all familiar with pkg-config, and, as far as I can tell it's not even installed on the Mac on which I am trying to do this. Curiously, its man page *does* work (it's in /usr/X11/man, for some reason). Does Cabal have some sort of embedded pkg-config?