Just ran into a weird crash with Swift 2.2 in Xcode 7.3. It reproduces in a
playground:
import Foundation
let a = [88]
let b: [Any] = a // CRASH
In my real program, the top of the crash backtrace is:
* thread #1: tid = 0x460b62, 0x000000010669988b
libswiftCore.dylib`swift_unknownRetain + 27, queue = 'com.apple.main-thread',
stop reason = EXC_BAD_ACCESS (code=1, address=0x58)
frame #0: 0x000000010669988b libswiftCore.dylib`swift_unknownRetain + 27
frame #1: 0x0000000106488565
libswiftCore.dylib`Swift._arrayConditionalBridgeElements <A, B>
(Swift.Array<A>) -> Swift.Optional<Swift.Array<B>> + 1029
frame #2: 0x00000001064875a7 libswiftCore.dylib`Swift._arrayForceCast <A,
B> (Swift.Array<A>) -> Swift.Array<B> + 263
It’s interesting that the memory address causing the crash is 0x58, which in
decimal is 88, the first item in the array. If you change the first item of the
array to a different number, the crash address changes to match. So it’s
misinterpreting the integer as a pointer.
Also interestingly, if you remove “import Foundation”, it no longer compiles —
the last line gets an error “Cannot convert value of type ‘[Int]’ to expected
argument type ‘[Any]’”. Is boxing of integers really dependent on Obj-C
bridging?
—Jens
PS: Should I file the bug report with Apple or at swift.org?_______________________________________________
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