I don't want to get too bogged down here, but sure: When you use autoconf, you typically run configure, then you're left with a config.h, which then parameteri

I don't want to get too bogged down here, but sure: When you use autoconf, you typically run configure, then you're left with a config.h, which then parameterizes later builds. On the other hand, when you evaluate the the definition of dirent->name, no intermediate file is left behind. Of course in both cases you make temporary C files, but they are ephemeral. The difference is that in the first case you are generating files for inclusion in a later phase, and in the second you are effectively extending your scheme compiler with a c compiler. The surprising about this code from a Scheme programmer's POV is that usually macros are about rewriting Scheme source using Scheme. In this case the macro generates C source, forks to compile and run it, and munges the result into the resulting text. But sure, I can see that from a certain point of view, autoconf and scheme macros can do similar things :)