8df105aad4
learned that os_unfair_lock with & was quite unsafe when used within swift. Apparently in swift, &foo in Swift means "make a copy of foo and pass it inout to a function, then overwrite its value with whatever the function did to it when that function returns." And if you're using it within a struct, it's apparently even more dangerous. because the address of self can change from call to call — self might not even have an address, it might be contained in registers only. Using NSlock will be a smidge less performant, but notably more safe.
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