Hi,
I’m porting some C to Swift and I need to pass a Swift instance through a `void
*` (ie, UnsafeMutableRawPointer). It works, in one thread, but when a second
thread accesses the exact same pointer, it fails with memory errors like
EXC_BAD_ACCESS
The code below could be pasted into an AppDelegate.swift in a new single view
iOS project.
Anyone know what’s going on here? The second call to `tryUsingUnsafePointer`,
in the new thread, crashes.
Rob
class PointerTest {
let str = "Hello"
init() { print("PointerTest.init") }
deinit { print("PointerTest.deinit") }
func start() {
var mSelf = self
let unsafePtr = UnsafeMutableRawPointer(&mSelf)
tryUsingUnsafePointer(unsafePtr)
print("Passing unsafe pointer to another thread: \(unsafePtr)")
Thread.detachNewThread {
tryUsingUnsafePointer(unsafePtr)
}
}
}
func tryUsingUnsafePointer(_ ptr: UnsafeMutableRawPointer) {
print("Using unsafe pointer:")
let typedPtr = ptr.assumingMemoryBound(to: PointerTest.self)
// let typedPtr = ptr.bindMemory(to: PointerTest.self, capacity: 1)
print(" typedPtr: \(typedPtr)")
let obj = typedPtr.pointee
print(" obj.str: \(obj.str)") // Memory error happening here, or
sometimes line above
}
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
var ptrTest: PointerTest?
func application(_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey:
Any]?) -> Bool {
ptrTest = PointerTest()
ptrTest?.start()
return true
}
[...]
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