<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi Paul,<div class=""><br class=""></div><div class="">Thanks for reviewing the proposal!<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Dec 20, 2017, at 9:21 PM, Paul Cantrell <<a href="mailto:cantrell@pobox.com" class="">cantrell@pobox.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">A concern: how would a library author reason about, and check for bugs in, the combinatorial explosion of old and new implementations that could exist simultaneously with this feature in use?</div></div></div></blockquote><div><br class=""></div>I don’t have a simple answer to this unfortunately, other than the author being really careful, perhaps keeping around build artifacts that were compiled against older versions of the library and testing those.</div><div><br class=""><blockquote type="cite" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">That last paragraph gives a relatively trivial example, but the implications are daunting! If I understand correctly, anything in a library that uses any @inlinable or @abiPublic code must be prepared to deal with every possible combination of every past published implementation of that code. And that “every possible combination” is not per function, but per…call site?</div><div class=""><br class=""></div><div class="">Suppose we have this:</div><div class=""><br class=""></div><div class=""><div class=""> // Module A</div><div class=""><br class=""></div><div class=""> @inlineable func bar() { ... }</div><div class=""><br class=""></div><div class=""> // Module B</div><div class=""><br class=""></div><div class=""> @inlineable func foo() {</div><div class=""> if whatever {</div><div class=""> bar(0) // compiler decides to inline this...</div><div class=""> } else {</div><div class=""> bar(1) // ...but not this, for whatever reason</div><div class=""> }</div><div class=""> }</div><div class=""><br class=""></div><div class=""> // Module C</div><div class=""><br class=""></div><div class=""> func baz() {</div><div class=""> foo()</div><div class=""> }</div></div><div class=""><br class=""></div><div class="">…and suppose B was compiled against A v1.0 but C was compiled against A v2.0. Then, if I’m following, it’s possible for bar(0) to use the 1.0 implementation but bar(1) to use the 2.0 impl. Do I have that right? It seems to be what the hash value example is getting at.</div></div></blockquote><div><br class=""></div>That is correct. Another example is if module A publishes an inlinable function, and module B and C depend on A, but B and C were compiled with different versions of A. Then a fourth module D that depends on B and C might see two different published versions of this function.</div><div><br class=""><blockquote type="cite" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">Or is this not as dangerous as I’m imagining it to be?</div></div></blockquote><div><br class=""></div>It *is* pretty dangerous, which is why I hope this feature is used judiciously by third-party binary frameworks. With source frameworks that are built together with an app and always recompiled, this is less of a concern.</div><div><br class=""></div><div>Also we are using this feature extensively in the standard library, so as the standard library evolves we will learn and develop best practices, hopefully without too many hiccups :)</div><div><br class=""></div><div>Slava</div><div><br class=""><blockquote type="cite" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div><div class="">Cheers, P</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><blockquote type="cite" class=""><div class="">On Dec 20, 2017, at 6:19 PM, Ted Kremenek via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;" class=""><p style="-webkit-print-color-adjust: exact; margin-right: 0px; margin-bottom: 15px; margin-left: 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255); margin-top: 0px !important;" class="">The review of "SE-0193 - Cross-module inlining and specialization" begins now and runs through <strong style="-webkit-print-color-adjust: exact;" class="">January 5, 2018</strong>.</p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">The proposal is available here:</p>
<blockquote style="margin: 5px 5px; padding-left: 10px; border-left: thin solid #1abc9c;" class=""><div style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0193-cross-module-inlining-and-specialization.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0193-cross-module-inlining-and-specialization.md</a></div>
</blockquote><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">Reviews are an important part of the Swift evolution process. All review feedback should be sent to the swift-evolution mailing list at:</p>
<blockquote style="margin: 5px 5px; padding-left: 10px; border-left: thin solid #1abc9c;" class=""><div style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div>
</blockquote><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">or, if you would like to keep your feedback private, directly to the review manager. </p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">When replying, please try to keep the proposal link at the top of the message:</p>
<blockquote style="margin: 5px 5px; padding-left: 10px; border-left: thin solid #1abc9c;" class=""><div style="-webkit-print-color-adjust: exact; margin: 0px;" class="">Proposal link: <a href="https://github.com/apple/swift-evolution/blob/master/proposals/0193-cross-module-inlining-and-specialization.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0193-cross-module-inlining-and-specialization.md</a><br style="-webkit-print-color-adjust: exact;" class="">
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Other replies</div>
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<h3 id="toc_0" style="-webkit-print-color-adjust: exact; margin: 20px 0px 10px; padding: 0px; -webkit-font-smoothing: antialiased; cursor: text; position: relative; font-size: 18px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">What goes into a review of a proposal?</h3><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. </p><p style="-webkit-print-color-adjust: exact; margin: 15px 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">When reviewing a proposal, here are some questions to consider:</p>
<ul style="-webkit-print-color-adjust: exact; margin: 15px 0px; padding-left: 30px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255);" class="">
<li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class="">What is your evaluation of the proposal?</p>
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<li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class="">Is the problem being addressed significant enough to warrant a change to Swift?</p>
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<li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class="">Does this proposal fit well with the feel and direction of Swift?</p>
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<li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class="">If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?</p>
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<li style="-webkit-print-color-adjust: exact; margin: 0px;" class=""><p style="-webkit-print-color-adjust: exact; margin: 0px 0px 15px;" class="">How much effort did you put into your review? A glance, a quick reading, or an in-depth study?</p>
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</ul><p style="-webkit-print-color-adjust: exact; margin-top: 15px; margin-right: 0px; margin-left: 0px; font-family: Helvetica, arial, sans-serif; background-color: rgb(255, 255, 255); margin-bottom: 0px !important;" class="">Thanks,<br style="-webkit-print-color-adjust: exact;" class="">
Ted Kremenek<br style="-webkit-print-color-adjust: exact;" class="">
Review Manager</p>
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