> On Aug 10, 2017, at 9:44 AM, Alastair Houghton <alast...@alastairs-place.net> > wrote: > > On 10 Aug 2017, at 15:24, Jeremy Hughes <moon.rab...@virginmedia.com > <mailto:moon.rab...@virginmedia.com>> wrote: >> >>> On 10 Aug 2017, at 15:15, Alastair Houghton <alast...@alastairs-place.net >>> <mailto:alast...@alastairs-place.net>> wrote: >>> >>> On 10 Aug 2017, at 15:09, Charles Srstka <cocoa...@charlessoft.com >>> <mailto:cocoa...@charlessoft.com>> wrote: >>>> >>>> They’re equivalent syntactically, but performance-wise, +array and friends >>>> will cause the object to be put into an autorelease pool. Therefore, +new >>>> is better for performance. >>> >>> Not with ARC they don’t. The ARC logic circumvents the autorelease pool in >>> that case. >> >> Are you sure? > > Yes, I’m sure. At the call site, ARC causes the compiler to emit a call to > objc_retainAutoreleasedReturnValue() or > objc_unsafeClaimAutoreleasedReturnValue(), while in the method itself, ARC > will use objc_autoreleaseReturnValue() or > objc_retainAutoreleaseReturnValue(). The latter looks at the code for the > call site and, assuming it matches, it will *not* do the autorelease and will > set a flag that causes objc_retainAutoreleasedReturnValue() to eliminate the > retain.
The frameworks (and thus, the implementation of +array) are not built using ARC. The -autorelease method is called manually, and the object is put in the autorelease pool. You can see this for yourself by making a small test app that calls [NSMutableArray array] and running it in Instruments, where the autorelease will be clearly visible. Charles _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
