[swift-evolution] [Review] SE-0176: Enforce Exclusive Access to Memory

[Félix Cloutier]

I have one concern and one general comment.

General comment: there's a switch to turn off overflow checks for performance reasons. It seems to me that this check is going to be much more expensive than an overflow check, and it's certainly not much more likely to trigger in a release build after some amount of testing, so my opinion would be that there should be a way to turn it off globally. To me, the checking is UBSan behavior more than a language feature.

Concern: `swap` is quoted a lot for a method that would break under this rule, but as it happens, `swap` with the same value on both sides is (should be) a no-op. Is there a way to not trip the static or dynamic checkers in well-defined cases like that one? Is there any way to check that two inout parameters refer to the same value?

> Le 2 mai 2017 à 13:07, Ben Cohen via swift-evolution <swift-evolution at swift.org> a écrit :
> 
> Hello Swift community,
> 
> The review of SE-0176: "Enforce Exclusive Access to Memory" begins now and runs through May 8, 2017.
> 
> The proposal is available here:
> 
> https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md <https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md>
> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at:
> 
> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
> or, if you would like to keep your feedback private, directly to the review manager. 
> 
> When replying, please try to keep the proposal link at the top of the message:
> 
> Proposal link:
> 
> https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md <https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md>
> Reply text
> 
> Other replies
> 
>  <https://github.com/apple/swift-evolution#what-goes-into-a-review-1>
> What goes into a review?
> 
> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
> 
> What is your evaluation of the proposal?
> Is the problem being addressed significant enough to warrant a change to Swift?
> Does this proposal fit well with the feel and direction of Swift?
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> 
> https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
> 
> Thanks,
> Ben Cohen
> Review Manager
> 
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