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1. Embed this notice
   David Smith (catfish_man@mastodon.social)'s status on Thursday, 20-Feb-2025 08:42:14 JST David Smith

   This makes me feel old, but lately I've been seeing misunderstandings about what autorelease actually is in objc/swift. "It's a GC", "it's weird magic", "it's a batch allocator", etc…

   Autorelease is just an array. You (or, 99% of the time, SDK methods you're calling) manually put things into the array by calling `autorelease` on them, and then when you reach the closing brace of the autoreleasepool {} block, it calls `release` on anything that was added.

   That's literally all it is.

   #swiftlang

   • Embed this notice
     David Smith (catfish_man@mastodon.social)'s status on Thursday, 20-Feb-2025 08:42:14 JST David Smith

     in reply to

     • Tanner B 🆓🇵🇸

     Autorelease tidbits:

     RunLoops wrap your code in autoreleasepool {} before calling it; so does Swift Concurrency

     DispatchQueues don't, by default! Configure them with .workItem autorelease frequency to fix this

     It's much less overhead than you'd expect from my description

     swiftc can autorelease objects when returning them from @objc methods

     Neither ObjC nor Swift ARC will autorelease things other than that

     Use "Allocations" in Instruments to see where adding a pool would help

     #swiftlang

   • Embed this notice
     Paul Cantrell (inthehands@hachyderm.io)'s status on Thursday, 20-Feb-2025 08:42:14 JST Paul Cantrell

     in reply to

     @Catfish_Man
     Something I realized I don’t know: does the Swift compiler’s ARC ever inject an object autorelease? Or it is always explitict / from libraries?

   • Embed this notice
     David Smith (catfish_man@mastodon.social)'s status on Thursday, 20-Feb-2025 08:47:07 JST David Smith

     in reply to

     • Paul Cantrell

     @inthehands it's *surprisingly* hard to get it to stop doing it for return values from @\objc methods!

     I've even resorted to lying about the return type and returning an Unmanaged<Foo> instead, since ObjC doesn't care as long as the representation is just a pointer.

     Not aware of any situations where it will other than that one though.

   • Embed this notice
     Paul Cantrell (inthehands@hachyderm.io)'s status on Thursday, 20-Feb-2025 08:47:07 JST Paul Cantrell

     in reply to

     @Catfish_Man
     Thanks!

     And, re autoreleasing every return value: I seem to remember that I did that back in the pre-ARC days, so…I can hardly blame it!