Hi,

The lack of WIN32 causes bad result (compilation error) of conftest for
win32 extension libraries.
I believe it's not caused by Ruby itself, but the latest Windows SDK's
header files for Win64 support.
The problem is:
 - define 'have_header('..')  in extconf.rb
 - mkmf.rb creates conftest.c for the header with some usual ruby's (cf,
win32.h).
 - but no other user specific macro or header are supplied
 - win32.h includes winsock2.h and it requrires WIN32 or _WIN64 but
there is no chance to supply it.
 - so compilation of conftest.c fails.
 - building the extension library may fail too.
So, it's very harmful for ruby extension library programers without
r30989.

-- 
arton <artonx / yahoo.co.jp>