Description
The program below crashes at line 76, which tries to print a property of an optional:
This crash is not easy to reproduce: renaming certain symbols, reordering them, removing apparently unused protocols or reducing the cases of either enum may fix it.
In my original code, the crash is preceded by several logged warnings like
warning: the Swift runtime was unable to demangle the type of field '(null)'. the mangled type name is 'ed': unknown error. this field will show up as an empty tuple in Mirrors
In my original code, printing the nil object actually prints an object with nonsensical properties (interleaved with the above warning), like
ID(name: (), instance: 16)
I'm grateful for any insight into what the cause of the crash is, if there is a workaround, and if it will work for current as well as past operating systems.
Reproduction
enum B: Hashable, Codable {
case c(C)
case d(D)
}
enum C: String, Codable {
case _1
case _2
case _3
case _4
case _5
case _6
case _7
case _8
case _9
case _10
case _11
case _12
case _13
case _14
case _15
case _16
case _17
case _18
case _19
case _20
case _21
case _22
case _23
case _24
case _25
case _26
case _27
case _28
case _29
case _30
case _31
case _32
case _33
}
enum D: String, CaseIterable, Codable {
case _1
case _2
case _3
case _4
case _5
case _6
case _7
case _8
case _9
case _10
case _11
case _12
}
struct ID: Hashable, Codable {
let name: B
let instance: Int
}
class A1 {
init() {
let actionHandler = ActionHandler()
actionHandler.register(b)
try! actionHandler.handle(context: 0)
}
struct A2: Codable {
let a: ID?
}
func b(data: inout A2?, context: Int) {
print(data) // nil
print(data?.a) // crash: Thread 1: EXC_BAD_ACCESS (code=1, address=0x16341e660)
}
}
let a = A1()
class ActionHandler {
private var handle: ((Int) -> Void)!
init() {
}
func register<T: Codable>(_ handle: @escaping (_ data: inout T?, _ context: Int) -> Void) {
self.handle = { context in
var data: T?
handle(&data, context)
}
}
func handle(context: Int) throws {
handle(context)
}
}Stack dump
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=2, address=0x16e701cb0)
frame #0: 0x0000000187ae0ac4 libsystem_platform.dylib`_platform_strlen + 4
frame #1: 0x000000019b1bb70c libswiftCore.dylib`(anonymous namespace)::getFieldAt(swift::TargetMetadata<swift::InProcess> const*, unsigned int) + 284
frame #2: 0x000000019b1b7b5c libswiftCore.dylib`swift_reflectionMirror_count + 864
frame #3: 0x000000019b479754 libswiftCore.dylib`Mirror.init(internalReflecting:subjectType:customAncestor:) + 132
frame #4: 0x000000019b1b6cb4 libswiftCore.dylib`Mirror.init(reflecting:) + 248
frame #5: 0x000000019b1b8dd8 libswiftCore.dylib`_adHocPrint_unlocked(_:_:_:isDebugPrint:) + 3568
frame #6: 0x000000019b1c1114 libswiftCore.dylib`_debugPrint_unlocked(_:_:) + 932
frame #7: 0x000000019b1b855c libswiftCore.dylib`_adHocPrint_unlocked(_:_:_:isDebugPrint:) + 1396
frame #8: 0x000000019b1c1114 libswiftCore.dylib`_debugPrint_unlocked(_:_:) + 932
frame #9: 0x000000019b4601e8 libswiftCore.dylib`specialized _debugPrint(_:separator:terminator:to:) + 1668
frame #10: 0x000000019b4566fc libswiftCore.dylib`Swift.Optional.debugDescription.getter : Swift.String + 392
frame #11: 0x000000019b1bc46c libswiftCore.dylib`_print_unlocked(_:_:) + 492
frame #12: 0x000000019b4605a4 libswiftCore.dylib`specialized _print(_:separator:terminator:to:) + 140
frame #13: 0x000000019b45fa0c libswiftCore.dylib`print(_:separator:terminator:) + 620
* frame #14: 0x0000000100006560 problem`A.b(data=nil, context=0) at main.swift:303:9
frame #15: 0x0000000100005c78 problem`implicit closure #2 in implicit closure #1 in A.init() at main.swift:0
frame #16: 0x0000000100006b84 problem`closure #1 in ActionHandler.register<problem.A.C>(context=0, handle=0x0000000100009b34 problem`partial apply forwarder for implicit closure #2 (inout Swift.Optional<problem.A.C>, Swift.Int) -> () in implicit closure #1 @Sendable (problem.A) -> (inout Swift.Optional<problem.A.C>, Swift.Int) -> () in problem.A.init() -> problem.A at <compiler-generated>) at main.swift:320:13
frame #17: 0x0000000100006d20 problem`ActionHandler.handle(context=0) at main.swift:325:9
frame #18: 0x0000000100005074 problem`A.init() at main.swift:294:28
frame #19: 0x0000000100000d2c problem`A.__allocating_init() at main.swift:0
frame #20: 0x0000000100000cc4 problem`main at main.swift:308:9
frame #21: 0x000000018771be00 dyld`start + 6992
Expected behavior
No crash.
Environment
swift-driver version: 1.148.6 Apple Swift version 6.3.2 (swiftlang-6.3.2.1.108 clang-2100.1.1.101)
Target: arm64-apple-macosx26.0
Additional information
No response
Description
The program below crashes at line 76, which tries to print a property of an optional:
This crash is not easy to reproduce: renaming certain symbols, reordering them, removing apparently unused protocols or reducing the cases of either enum may fix it.
In my original code, the crash is preceded by several logged warnings like
In my original code, printing the
nilobject actually prints an object with nonsensical properties (interleaved with the above warning), likeI'm grateful for any insight into what the cause of the crash is, if there is a workaround, and if it will work for current as well as past operating systems.
Reproduction
Stack dump
Expected behavior
No crash.
Environment
swift-driver version: 1.148.6 Apple Swift version 6.3.2 (swiftlang-6.3.2.1.108 clang-2100.1.1.101)
Target: arm64-apple-macosx26.0
Additional information
No response