Building Python 3.1.2 on Cygwin 1.7, I got errors in main.c stemming from a warning: PATH_MAX redefined (see attached log).  I got around this by commenting out the #define.  I don't know if the best solution is #ifndef, #undef, or something else. . . . I know CygWin has changed the value of PATH_MAX in 1.7 (see: http://www.cygwin.com/cygwin-ug-net/ov-new1.7.html), though I'm not sure why that would cause this problem.