Recently a change was made to hsc2hs to fix this ticket: http://hackage.haskell.org/trac/ghc/ticket/2897 Unfortunately, the result is I (apparently) can't use it now. Here's how that happens: The change was to remove the dependency on HsFFI.h. However, the solution is to create a little wrapper .c file that includes wrappers around various stdio functions like fputs(). This relies on C allowing implicit casts from void* to e.g. FILE*, and is also happy to let you use undeclared functions. g++ rejects that code. And since I am calling into C++ (via a 'extern "C" { ... }' wrapper) I wind up including C++ headers that contain the structs I want hsc2hs to calculate offsets for. Of course one solution is to use C as hsc2hs expects, but it would be awkward to split my (largish) c++ program's headers into C compatible and C++ only. So meanwhile I've reverted back to an older version of hsc2hs that includes HsFFI.h. Working with c++ headers was maybe not in the original design for hsc2hs, but it's a very useful feature nonetheless. WRT HsFFI.h and the ticket, I added -I(ghc --print-libdir)/include to my hsc2hs rule a long time ago, and it wasn't very hard to do, though I admit it would have been easier had there been documentation about what to do, or a mandatory flag for the HsFFI.h path. It looks like Duncan suggested that already. Or perhaps there's a better way to wrap C++?