<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><div style="direction: inherit;">I'd also like to understand this more and this answer does not completely satisfy me. I understand backwards compatibility, especially in terms of source breaking changes.</div><div style="direction: inherit;"><br></div><div style="direction: inherit;">I have more difficulties understanding what breaks or not the ABI and how to make educated guesses about what features will require breaking it.</div></div><div><div style="direction: inherit;"><br></div>On 11 Aug 2016, at 13:24, Anton Zhilin via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">2016-08-11 11:52 GMT+03:00 Jonathan Hull via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Could someone explain in simple terms what the ABI is and what sorts of things might affect it?<br>
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I had thought it was the layout in memory of structs/classes/etc… and how the program knows where to go to find a particular field. This seems to be incorrect though, as I have seen many features that I would assume have some affect on this layout ruled “out of scope for phase 1”. For example, I would think that many generics features would have an impact on the ABI, or the idea of COW (via secret boxing) for structs, or even union types.<br>
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At the very least, I would think that mix-ins would have a fairly significant effect.</blockquote><div><br></div><div>ABI stability means that changes will have to be backwards compatible after a certain stage. If we can add mixins feature without modifying old code (and its SIL and IR and whatever), then we are fine. </div></div></div></div>
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