fix IB in fifoToOwnedArrayList

[matklad]

memcpy requires non-overlapping arguments.

fifo.realign() handles this case correctly and tries to provide an optimized implementation.

This probably wasn't hit in practice, as, in a typical usage, fifo's head is not advanced.

[daurnimator]

I don't think you need the if (fifo.head != 0) check: realign should be cheap enough to do unconditionally.

[matklad]

Hm, if I am reading the code correctly, head==0 would go into this branch:

zig/lib/std/fifo.zig

Line 91 in 5d7fa55

mem.copyForwards(T, self.buf[0..self.count], self.buf[self.head..][0..self.count]);

Which is a (noop) for-loop over the entire data, which feels like it could be costly, especially given that head==0 is the common case actually.

[daurnimator]

Which is a (noop) for-loop over the entire data, which feels like it could be costly, especially given that head==0 is the common case actually.

sorry you're right!

[andrewrk]

Thank you.

This data structure looks like a nice candidate to participate in a fuzz test that does various equivalent things with different std lib containers and then asserts that they get the same results.