[swift-evolution] [Review] SE-0055 Make unsafe pointer nullability explicit using Optional

[Brent Royal-Gordon]

> In the low level world, there is no such thing as an invalid address; both 0x0 and ~0x0 are perfectly valid byte pointers. So using something else than 0x0 for Swift invalid pointer just shuffle the problem around.

Let me state it this way: You cannot write a fully-conforming C compiler for a platform which does not have some way to represent an invalid pointer. However C does it, Swift can do the same thing.

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Brent Royal-Gordon
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