Mac OSX 10.6 compiler: a puzzling experience with 32 vs 64 bit

Question

I have trouble understanding the gcc compiler provided by OSX 10.6 snow leopard, mainly because of my lack of experience with 64 bits environments.

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Answer 1

The default compiler on Snow Leopard is gcc4.2, and its default architecture is x86_64. The typical way to build Mac software is to build multiple architectures in separate passes, then use lipo to combine the results. (lipo only compiles single-arch files into a multiple-arch file, or strips archs out of a multi-arch file. It has no utility on single-arch files, as you discovered.)

The bitness of the compiler has nothing to do with anything. You can build 32-bit binaries with a 64-bit compiler, and vice versa. (What you think is the "target" of the compiler is actually its executable, which is different.)

The bitness of the kernel has nothing to do with anything. You can build and run 64-bit binaries when booted on a 32-bit kernel, and vice versa.

What matters is when you link, whether you have the appropriate architectures for linking. You can't link 32-bit builds against 64-bit binaries or vice versa. So the important thing is to see what the architectures of your link libraries are, make sure they're coherent, then build your binary of the same architecture so you can link against the libraries you have.