[David Abrahams] > ...which explains why I have to > # define SIZEOF_LONG 4 > explicitly to build any Cygwin extension modules. I don't believe anything said here explained that. All Python ports have to define SIZEOF_LONG, and if Cygwin's isn't then that's a bug unique to Cygwin's config. On Unixoid systems, I believe that's supposed to be done by the autoconf hair.