> On Jan 8, 2018, at 2:59 PM, Greg Parker via swift-users > <swift-users@swift.org> wrote: > > >> On Jan 8, 2018, at 12:51 PM, Jordan Rose via swift-users >> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote: >> >>> On Jan 8, 2018, at 11:47, Fadi Botros <botros_f...@yahoo.com >>> <mailto:botros_f...@yahoo.com>> wrote: >>> >>> 1st: How to invoke the thread sanitizer? >> >> Check out this article on developer.apple.com <http://developer.apple.com/>: >> https://developer.apple.com/documentation/code_diagnostics/thread_sanitizer/enabling_the_thread_sanitizer >> >> <https://developer.apple.com/documentation/code_diagnostics/thread_sanitizer/enabling_the_thread_sanitizer> >>> 2nd: I think making something like ConcurrentModificationException of Java >>> should be a little better experience (if it will not make, or make a small >>> performance penalty, also if it makes performance penalty, it would be >>> activated only when you make a debug version or non-optimized version) >> >> I don't exactly disagree, but my understanding is that the work to do such a >> thing is nearly equivalent to having thread sanitizer on all the time. But >> maybe there's a simpler model that we could still turn on in debug builds. >> Can you file a bug report requesting this now that bugs.swift.org >> <http://bugs.swift.org/> is back up? > > Something like ConcurrentModificationException ought to be cheaper than the > thread sanitizer. The thread sanitizer works hard to detect every concurrency > error. ConcurrentModificationException typically does something simple and > cheap that catches errors sometimes but makes no attempt to be exhaustive. > > Objective-C's fast enumeration protocol includes a mechanism like this. The > collection can have a simple mutation counter, and the enumerator captures > the counter's value at the start and checks that the value is unchanged as > the enumeration proceeds.
Does ObjC synchronize the mutation counter? My understanding is that that counter was used to detect mutation while iteration on a single thread, not across threads. -Chris
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