[dataflow]

You're not understanding what I'm saying. I'm talking about what I see in the debugger when I'm debugging. When you see 0xCC in a variable in the debugger you know you probably had an out of bounds read. Because in debug mode the compiler and runtime leave these markers in uninitialized memory. For that to be helpful you need to swap until the max of the initialized sizes of both arrays, so that you preserve these markers. You defeat that helpful feature if you copy the uninitialized portion of the buffer instead of swapping.

[cmeacham98]

Oh I think I see, I never considered the scenario where the buffer was half uninitialized, I thought you meant you were swapping an (entirely) uninitialized buffer with an initialized one.

[dataflow]

Well that certainly could be a special case of the more general scenario I wrote; that's what would happen if it turned out the first buffer had nothing useful in it and the second one was full. But yeah, in general they'd both be partially filled: you have [0, ?, ?] and [1, 1, ?] and want to swap them. You wouldn't touch the last ? in either, but you would swap the [0, ?] with [1, 1], and in debug mode you'd see ? = 0xCC. Except the language doesn't really let you do that, even though fundamentally there should be nothing wrong with it, and in fact is likely to be desirable in practice.