I fixed a rather nasty bug today in AspectObjectiveC. One particular unit
test would crash with EXC_BAD_ACCESS every time. After learning far more
about registers and ABIs than I ever wanted to know (thanks, Greg Parker),
it dawned on me that performSelector: was corrupting memory. It was
particularly hard to track down because the crash would happen a couple of
lines after the call to performSelector:, when the corrupted memory was
actually accessed.
I’ve never had a problem with performSelector: before, but this time I was
using it a little differently. The return value of the selector was an
NSRect.
Now for the gory explanation.