This is a linking issue. It seems GHC 7 automatically feeds the linker SimpleJSON.o so when you explicitly provide it too then you get those conflicts. All you need to do is call:
> ghc -o simple Main.hs Unless you're using GHC 6, then the original command is correct: > ghc -o simple Main.hs SimpleJSON.o Or even better, use the --make flag as that works with either version: > ghc --make -o simple Main.hs Cheers, Thomas On Wed, Aug 17, 2011 at 10:37 AM, Paul Reiners <paul.rein...@gmail.com> wrote: > I'm trying to do the following from Chapter 5 of "Real World Haskell": > > Our choice of naming for the source file and function is deliberate. To > create an executable, ghc expects a module named Main that contains a > function named main. The main function is the one that will be called when > we run the program once we've built it. 6 comments > > ghc -o simple Main.hs SimpleJSON.o > > ---from > http://book.realworldhaskell.org/read/writing-a-library-working-with-json-data.html > > When I do that, I get this error: > > C:\ch05>ghc -o simple Main.hs SimpleJSON.o > [2 of 2] Compiling Main ( Main.hs, Main.o ) > Linking simple.exe ... > SimpleJSON.o:fake:(.data+0x0): multiple definition of > `SimpleJSON_getArray_closure' > .\SimpleJSON.o:fake:(.data+0x0): first defined here > SimpleJSON.o:fake:(.text+0x54): multiple definition of > `SimpleJSON_getArray_info' > .\SimpleJSON.o:fake:(.text+0x54): first defined here > SimpleJSON.o:fake:(.data+0x4): multiple definition of > `SimpleJSON_getObject_closure' > .\SimpleJSON.o:fake:(.data+0x4): first defined here > > What's going wrong here? > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
