EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000000 on JSONDecoder.decode

Question

I can see the exc bad excess on crashylitics , following is the code base . Is there anything wrong I am doing ? Crash is occurring on following line

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guard let data = userData, let userDetails = try? JSONDecoder().decode(UserDetailsThreadSafe.self, from: data) else {

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class UserDetailsThreadSafe:UserDetails
{

    let queue = DispatchQueue(label: "auth-thread-safe-queue", attributes: .concurrent)

    static let shared = UserDetailsThreadSafe()

    private override init()
    {
        super.init()
    }

    required init(from decoder: Decoder) throws {
        try super.init(from: decoder)
    }
    
    fileprivate func getUserDetails() -> UserDetailsThreadSafe? {
        
        queue.sync {
            // perform read and assign value
            var userData: Data? = LoginAuth.sharedInstance().defaultStorage?.secureValue(forKey: kUserDetails)
            if  userData == nil  {
                userData = UserDefaults.standard.value(forKey: kUserDetails) as? Data
            }
            guard let data = userData, let userDetails = try? JSONDecoder().decode(UserDetailsThreadSafe.self, from: data) else {
                return nil
            }
            return userDetails
        }
       
    }
    
    fileprivate func archieveData() {
        
        queue.async(flags: .barrier) {
            // perform writes on data
            if let data = try? JSONEncoder().encode(self), data.isEmpty == false, let jsonString = String(data: data, encoding: .utf8) {
                LoginAuth.sharedInstance().defaultStorage?.setSecure(jsonString, forKey: kUserDetails)
            }
        }
       
    }
}

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Answer 1

When adding tasks to your queue it is recommended to use "async" with the Barrier flag:

queue.async(flags: .barrier) {...}

Since we use async and not sync, the signature of getUserDetails() should change. This function should now pass back the result values using completion block, and return void.