Hi Alex, Thanks for digging into this. This seems like a correct solution for now.
I think there is a larger question though, which is why it’s possible to overrelease kCFEmptyString. I think we skirted the issue early in bringup of SCL-Foundation, but constant strings are supposed to be “pinned” and ref count operations on them a no-op. - Tony > On Oct 7, 2016, at 6:47 AM, Alex Blewitt via swift-corelibs-dev > <swift-corelibs-dev@swift.org> wrote: > > I'm looking at https://bugs.swift.org/browse/SR-2879 > <https://bugs.swift.org/browse/SR-2879> which is exposing itself through an > over-release of a constant CF string (in this case, kCFEmptyString). I don't > believe it to be a Swift related problem, because Swift doesn't get into the > internals of CFCalendar where the problem occurs. > > The problem is that CFCalendar releases the localeID when it's deallocated: > > if (calendar->_localeID) CFRelease(calendar->_localeID); > > https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L54 > > <https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L54> > > > The problem is that when the localeID is assigned, it doesn't appear to be > copied or renamed: > > calendar->_localeID = CFLocaleGetIdentifier(CFLocaleGetSystem()); > > https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L252 > > <https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L252> > > https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L281 > > <https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L281> > > > but elsewhere in the code, we do retain it: > > CFStringRef localeID = CFLocaleGetIdentifier(locale); > if (localeID != calendar->_localeID) { > CFRelease(calendar->_localeID); > CFRetain(localeID); > > https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L303-L306 > > <https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFCalendar.c#L303-L306> > > > When a locale isn't supplied, it uses the default global one, which is > defined to be an empty string: > > CFLocaleRef CFLocaleGetSystem(void) { > CFLocaleRef locale; > CFLocaleRef uselessLocale = NULL; //if we lose the race creating the > global locale, we need to release the one we created, but we want to do it > outside the lock. > __CFLocaleLockGlobal(); > if (NULL == __CFLocaleSystem) { > __CFLocaleUnlockGlobal(); > locale = CFLocaleCreate(kCFAllocatorSystemDefault, CFSTR("")); > if (!locale) return NULL; > > https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFLocale.c#L255-L261 > > <https://github.com/apple/swift-corelibs-foundation/blob/1a76e814212e781a9d50782ee24117760cfe9b48/CoreFoundation/Locale.subproj/CFLocale.c#L255-L261> > > > The CFSTR("") results in a reference to kCFEmptyString, which reduces by one > each time a CFCalendar is created and destroyed, leading to the (unrelated) > test failures of https://github.com/apple/swift-corelibs-foundation/pull/667 > <https://github.com/apple/swift-corelibs-foundation/pull/667> as documented > in https://bugs.swift.org/browse/SR-2879 > <https://bugs.swift.org/browse/SR-2879> > > My suggestion is to insert a CFRetain when the calendar->locale is set, to > balance out the CFRelease that's being performed in the deallocator. Building > with this simple change and checking the retain count of kCFEmptyString > verifies that it does fix the problem, although I'm open to suggestions as to > improvements of where the retain takes place, if not on lines 252 and 282. > > 1> import Foundation > 2> :p (int)swift_retainCount(&__kCFEmptyString) > (int) $11 = 1 > 2> _ = Calendar(identifier:.gregorian) > 3> :p (int)swift_retainCount(&__kCFEmptyString) > (int) $12 = 3 > 3> _ = Calendar(identifier:.chinese) > 4> :p (int)swift_retainCount(&__kCFEmptyString) > (int) $13 = 3 > 4> _ = Calendar(identifier:.hebrew) > 5> :p (int)swift_retainCount(&__kCFEmptyString) > (int) $14 = 3 > 5> ^D > > Alex > _______________________________________________ > swift-corelibs-dev mailing list > swift-corelibs-dev@swift.org > https://lists.swift.org/mailman/listinfo/swift-corelibs-dev
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