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This was an amazing read. As someone who spent a long time hacking 68k Macs, I laughed out loud when I came to “Moving or substantially altering this code in Re
by rcarmo 3y ago
This was an amazing read. As someone who spent a long time hacking 68k Macs, I laughed out loud when I came to “Moving or substantially altering this code in ResEdit has side effects, usually explosive ones”.
- duskwuff 3y agoThe cause of those "explosive" side effects is relocations. The JSRs aren't actually jumping to low memory (e.g. 0x000007DE); they're relative to the base of the CODE resource, and get fixed up at load time based on a list of offsets stored elsewhere. Move one of the JSR instructions, and suddenly the relocation gets applied to the wrong place.