Suppose we say we want to define a new variant called +64bit. Let's figure out what we want that to do. Are we asking for a way to build a 64-bit local-architecture binary instead of a 32-bit local-architecture binary (e.g. x86_64 only)? or in addition to a 32-bit local-architecture binary by installing both into separate paths (e.g. ${prefix}/lib and ${prefix}/lib64 -- I don't think this is the Mac way)? or in addition to a 32-bit local-architecture binary by making a single fat binary (e.g. i386 and x86_64 in one file)? What if the user selects +universal in addition to +64bit? How will we handle that?
I have experimented with adding two new "variants" (or configure options): +m32 +m64 These corresponded with the GCC settings with the same name: -m32 and -m64.
Sorry, I guess I should have answered this rather than devising my own proposal... :-) My take on these matters should be evident from that post, however. Oh, and fat binaries/libraries are definitely the Mac way. No separate directories if they can be at all avoided. /Emil