I note (with pleasure) that config.guess now knows about Interix. One thing that it would have been nice for it to do at the same time is automatically add a #define _ALL_SOURCE everywhere. The code to do exactly the correct thing is there as a special case for AIX (see lib/autoconf/specific.m4). Recoginzing __INTERIX (two underscores) in the same way that _AIX is already recognized (as in the below taken from specific.m4) would be very helpful. (_ALL_SOURCE has "the same" meaning on AIX and Interix: allow everything, rather than just POSIX.)
AC_EGREP_CPP(yes, [#ifdef _AIX yes #endif ], (Just to avoid IP issues, this is small enough that I'd rather describe it than provide an actual patch.) (Whether it's best to do this as a variant on the AIX macro, or bury it in the existing AIX macro, or add a new "needs _ALL_SOURCE" macro is a judgement call I leave to you.) Donn
