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

[John McCall]

> On May 2, 2017, at 6:44 PM, Jon Shier via swift-evolution <swift-evolution at swift.org> wrote:
> 	I’m not a language or memory expert, so I think the proposal could use a few more examples of the code it would disallow. Perhaps examples from real world projects? Without being an expert I’m having a hard time seeing the full impact of the proposed rules. 

We hope that there will not be any widespread examples from real-world projects that run afoul of the rule.  If the examples seem a little contrived, that's good; we believe the rule is almost always already followed.

> 	Also, the @exclusivity syntax doesn’t seem fully defined. Is there a @exclusivity(checked) counterpart?

Yes, which would be the default (on class properties and global variables).

> Would subclasses be allowed to mark inherited properties more or less strictly?

No.  The rule has to be established by the place which creates the storage.

> Also, is the logic for @ attributes and keyword attributes documented anywhere? Otherwise it seems like exclusive / nonexclusive would be an option.

The guidelines about when to use an @ attribute and when to use a keyword attribute are always a bit uncertain, but in this case I think they clearly point us towards an @ attribute.  This is an attribute which opts in to unsafe behavior for performance reasons; it is not expected to be important enough to warrant a keyword.

John.

> 
> 
> 
> Jon
> 
>> On May 2, 2017, at 4:07 PM, Ben Cohen via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> 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
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>> 
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>> Ben Cohen
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