Installation worked fine. However I encountered a problem that looks like a regression, although it may be a problem with new versions of the package I am trying to install:
It's not an H-P problem; Apple's started using their BLOCKS C extension in system headers, and gtk2hsc2hs doesn't understand it. (And possibly is not using cpp properly when processing headers.) You'll need to take this up with the gtk2hs folks.
#ifdef __BLOCKS__
int scandir_b(const char *, struct dirent ***,
int (^)(const struct dirent *), int (^)(const struct dirent **, const struct