Runtime checks only take effect at -Onone. Even if you explicitly ask for checks via -enforce-exclusivity=checked, they will be stripped (with a warning from the driver).
Support for dynamic checking at -O is something that will be considered post Swift 4. -Andy > On Jun 1, 2017, at 4:47 PM, Andrew Trick <atr...@apple.com> wrote: > > Hi swift-dev, > > PR-9995 enables exclusivity runtime checks: > https://github.com/apple/swift/pull/9995 > > These checks catch violations of exclusivity that can't be discovered > statically [0], printing the message: > > "Simultaneous accesses to 0x*, but modification requires exclusive access." > > The error message is followed by a backtrace and details on the source > locations of the two conflicting accesses. > > In Swift 3 mode, this runtime diagnostic is a warning. In Swift 4 mode it is > an error, meaning the program aborts immediately after reporting the first > failure. > > To disable the runtime checks, use -enforce-exclusivity=unchecked, which > enables static > checks only. > > This feature is explained in the Swift evolution proposal: Enforce Exclusive > Access to Memory: > https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md > > Note that exclusivity is not yet fully enforced for noescape closures. The > current checks are conservative in this respect. Enforcement will be > strengthened to handle this case in the near future, pending review of the > proposal ammendment: "Restrictions on recursive uses of non-escaping > closures". > https://github.com/apple/swift-evolution/blob/master/proposals/0176-enforce-exclusive-access-to-memory.md#restrictions-on-recursive-uses-of-non-escaping-closures > > [0] dynamic exclusivity violation > > struct MyStruct { > var i: Int = 0 > > mutating func mutateS(_ f: ()->Int) { > i += f() > } > } > > class MyClass { > var s: MyStruct > > init() { s = MyStruct() } > } > > func foo(_ o: MyClass) { > o.s.mutateS({ o.s.i }) > } > > -Andy _______________________________________________ swift-dev mailing list swift-dev@swift.org https://lists.swift.org/mailman/listinfo/swift-dev
