Mac OS X Debugging Magic

For some time I've been meaning to collect together notes about stuff I've come across that's useful when debugging problems on Mac OS. Stuff that isn't obvious and well-known to a developer from a different Unix. Now I don't have to, because Apple have published TN2124: Mac OS X Debugging Magic which contains just about everything I'd found, plus more.

The only thing I can think of that isn't mentioned there is giving -Wl,-Y -Wl,n options to GCC so Apple's ld(1) shows more information about the first n undefined symbols. Mac OS' linker isn't nearly as loquacious as Linux's, and won't by default tell you which files the symbol appears in; something I often find useful.

Although it sounds useful, I don't understand the INIT_Processes=1 hint, and Google doesn't seem to know anything about it either.