Alamofire: EXC_BAD_ACCESS KERN_INVALID_ADDRESS upon request execution

[rnkyr]

• [x] I've read, understood, and done my best to follow the *CONTRIBUTING guidelines.

What did you do?

I got a single entry point for any requests in my project (something like "RequestManager") that does the following:

fileprivate func _executeRequest(withPath path: String,
                                     params: [String: Any]? = nil,
                                     method: HTTPMethod,
                                     tokenNeeded: Bool = true,
                                     encoding: ParameterEncoding = URLEncoding.default
    ) -> Observable<DataResponse<Any>> {
        return Observable.create { [weak self] observer -> Disposable in
            guard let `self` = self else { return Disposables.create() }

            let request = self.sessionManager.requestWithoutCache(
                    self.defaultPath + path,
                    method: method,
                    parameters: params,
                    encoding: encoding,
                    headers: self.headers(with: tokenNeeded))
                .validate()
                .responseJSON { response in
                    switch response.result {
                    case .success:
                        observer.onNext(response)
                        observer.onCompleted()

                    case .failure(let error):
                        let fagError = FiveAndGoError.Network.from(error: error, metadata: response.data)
                        observer.onError(fagError)
                    }
                }

            return Disposables.create {
                request.cancel()
            }
        }
    }

What did you expect to happen?

Regular requests being sent.

What happened instead?

Some of the requests crashing.
I cannot reproduce this in my debug/staging environment through Xcode

But I got a lot of users' crashes sent to Fabric. The following contains stack trace of the crash:

Crashed: com.apple.main-thread
0  CFNetwork                      0x187e8d628 HTTPParser::HTTPParser(__CFAllocator const*, HTTPParserClient*, HTTPParser*) + 48
1  CFNetwork                      0x187d581d0 HTTPMessage::commonInitialization(unsigned char, HTTPMessage const*) + 248
2  CFNetwork                      0x187d581d0 HTTPMessage::commonInitialization(unsigned char, HTTPMessage const*) + 248
3  CFNetwork                      0x187d58360 HTTPMessage::HTTPMessage(HTTPMessage const*) + 112
4  CFNetwork                      0x187e8e670 HTTPRequestMessage::HTTPRequestMessage(HTTPRequestMessage const*) + 36
5  CFNetwork                      0x187d38ed8 HTTPRequest::HTTPRequest(HTTPRequest const*) + 24
6  CFNetwork                      0x187d3b5e4 URLRequest::initialize(URLRequest const*, unsigned char) + 640
7  CFNetwork                      0x187cf2f40 _createRequestCopy(__CFAllocator const*, _CFURLRequest const*, unsigned char) + 152
8  CFNetwork                      0x187c77f48 -[NSURLRequest mutableCopyWithZone:] + 44
9  libswiftFoundation.dylib       0x10f7560cc specialized URLRequest.init(_bridged:) + 36
10 libswiftFoundation.dylib       0x10f73afd0 static URLRequest._unconditionallyBridgeFromObjectiveC(_:) + 36
11 Alamofire                      0x107901c58 DataRequest.request.getter (Request.swift:108)
12 Alamofire                      0x1079377fc DataRequest.validate() (Validation.swift:84)
13 Core                           0x10d71e494 closure #1 in RequestManager._executeRequest(withPath:parameters:method:tokenNeeded:deviceIdNeeded:encoding:) (RequestManager.swift:245)
14 Core                           0x10d71f80c partial apply for closure #1 in RequestManager._executeRequest(withPath:parameters:method:tokenNeeded:deviceIdNeeded:encoding:) (<compiler-generated>)
15 RxSwift                        0x10c6be454 AnonymousObservable.run<A>(_:cancel:) (<compiler-generated>)
16 RxSwift                        0x10c6e6a94 Producer.subscribe<A>(_:) (Producer.swift:18)
17 RxSwift                        0x10c6a4dc4 CatchSink.run() (Catch.swift:123)
18 RxSwift                        0x10c6a5354 Catch.run<A>(_:cancel:) (Catch.swift:165)
19 RxSwift                        0x10c6e6a94 Producer.subscribe<A>(_:) (Producer.swift:18)
20 RxSwift                        0x10c705944 SwitchSink.run(_:) (Switch.swift:67)
21 RxSwift                        0x10c706b7c FlatMapLatest.run<A>(_:cancel:) (Switch.swift:231)
22 RxSwift                        0x10c6e6a94 Producer.subscribe<A>(_:) (Producer.swift:18)
23 RxSwift                        0x10c6d9320 MergeSink.run(_:) (Merge.swift:508)
24 RxSwift                        0x10c6d9b70 FlatMap.run<A>(_:cancel:) + 312
25 RxSwift                        0x10c6e6a94 Producer.subscribe<A>(_:) (Producer.swift:18)
26 RxSwift                        0x10c6a4dc4 CatchSink.run() (Catch.swift:123)
27 RxSwift                        0x10c6a5354 Catch.run<A>(_:cancel:) (Catch.swift:165)
28 RxSwift                        0x10c6e6a94 Producer.subscribe<A>(_:) (Producer.swift:18)
29 RxSwift                        0x10c6de500 ObservableType.subscribe(onNext:onError:onCompleted:onDisposed:) (<compiler-generated>)
30 MyProject                      0x102d7bf9c SomeModel.handleConfirmedStatus() (<compiler-generated>)
31 MyProject                      0x102d7a640 SomeModel.handleExistingDataFlow(someDataModel:) (SomeModel+CreateFlowBindings.swift:141)
32 MyProject                      0x102d7999c closure #1 in SomeModel.fetchCurrentData() (<compiler-generated>)
33 MyProject                      0x102d7e814 partial apply for thunk for @escaping @callee_guaranteed (@guaranteed SomeDataModel?) -> () (<compiler-generated>)
34 RxSwift                        0x10c6de820 closure #1 in ObservableType.subscribe(onNext:onError:onCompleted:onDisposed:) (<compiler-generated>)
35 RxSwift                        0x10c6dea20 partial apply for closure #1 in ObservableType.subscribe(onNext:onError:onCompleted:onDisposed:) (<compiler-generated>)
36 RxSwift                        0x10c697aa0 AnonymousObserver.onCore(_:) (<compiler-generated>)
37 RxSwift                        0x10c6e1078 ObserverBase.on(_:) (ObserverBase.swift:21)
38 RxSwift                        0x10c6e11a4 protocol witness for ObserverType.on(_:) in conformance ObserverBase<A> (<compiler-generated>)
39 RxSwift                        0x10c700404 Sink.forwardOn(_:) (Sink.swift:36)
40 RxSwift                        0x10c6a4fb0 CatchSink.on(_:) (Catch.swift:131)
41 RxSwift                        0x10c6a51f0 protocol witness for ObserverType.on(_:) in conformance CatchSink<A> (<compiler-generated>)
42 RxSwift                        0x10c700404 Sink.forwardOn(_:) (Sink.swift:36)
43 RxSwift                        0x10c7063c8 SwitchSinkIter._synchronized_on(_:) (Switch.swift:171)
44 RxSwift                        0x10c707888 SynchronizedOnType.synchronizedOn(_:) (SynchronizedOnType.swift:15)
45 RxSwift                        0x10c706204 SwitchSinkIter.on(_:) (Switch.swift:145)
46 RxSwift                        0x10c7064d0 protocol witness for ObserverType.on(_:) in conformance SwitchSinkIter<A, B, C> (<compiler-generated>)
47 RxSwift                        0x10c700404 Sink.forwardOn(_:) (Sink.swift:36)
48 RxSwift                        0x10c6d49cc MapSink.on(_:) (Map.swift:45)
49 RxSwift                        0x10c6d4b68 protocol witness for ObserverType.on(_:) in conformance MapSink<A, B> (<compiler-generated>)
50 RxSwift                        0x10c6d3564 Just.subscribe<A>(_:) (Just.swift:83)
51 RxSwift                        0x10c6d4ef8 Map.run<A>(_:cancel:) (Map.swift:100)
52 RxSwift                        0x10c6e6f08 closure #1 in Producer.subscribe<A>(_:) (Producer.swift:26)
53 RxSwift                        0x10c6be994 specialized CurrentThreadScheduler.schedule<A>(_:action:) (<compiler-generated>)
54 RxSwift                        0x10c6e6bb0 Producer.subscribe<A>(_:) (<compiler-generated>)
55 RxSwift                        0x10c705fac SwitchSink.on(_:) (Switch.swift:102)
56 RxSwift                        0x10c706144 protocol witness for ObserverType.on(_:) in conformance SwitchSink<A, B, C> (<compiler-generated>)
57 RxSwift                        0x10c700404 Sink.forwardOn(_:) (Sink.swift:36)
58 RxSwift                        0x10c6a4fb0 CatchSink.on(_:) (Catch.swift:131)
59 RxSwift                        0x10c6a51f0 protocol witness for ObserverType.on(_:) in conformance CatchSink<A> (<compiler-generated>)
60 RxSwift                        0x10c700404 Sink.forwardOn(_:) (Sink.swift:36)
61 RxSwift                        0x10c6be1a0 AnonymousObservableSink.on(_:) (Create.swift:50)
62 RxSwift                        0x10c6be2fc protocol witness for ObserverType.on(_:) in conformance AnonymousObservableSink<A> (<compiler-generated>)
63 RxSwift                        0x10c6e15c0 partial apply (<compiler-generated>)
64 RxSwift                        0x10c697ba0 AnyObserver.on(_:) (<compiler-generated>)
65 RxSwift                        0x10c6e1358 ObserverType.onNext(_:) (ObserverType.swift:27)
66 Core                           0x10d71e89c closure #1 in closure #1 in RequestManager._executeRequest(withPath:parameters:method:tokenNeeded:deviceIdNeeded:encoding:) (RequestManager.swift:250)
67 Alamofire                      0x107915f30 partial apply for specialized  (<compiler-generated>)
68 Alamofire                      0x1078f5910 thunk for @escaping @callee_guaranteed () -> () (<compiler-generated>)
69 libdispatch.dylib              0x1870fd6c8 _dispatch_call_block_and_release + 24
70 libdispatch.dylib              0x1870fe484 _dispatch_client_callout + 16
71 libdispatch.dylib              0x1870ddb34 _dispatch_main_queue_callback_4CF$VARIANT$armv81 + 1012
72 CoreFoundation                 0x187655ce4 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
73 CoreFoundation                 0x187650bac __CFRunLoopRun + 1964
74 CoreFoundation                 0x1876500e0 CFRunLoopRunSpecific + 436
75 GraphicsServices               0x1898c9584 GSEventRunModal + 100
76 UIKitCore                      0x1b48a0c00 UIApplicationMain + 212
77 MyProject                      0x102bfe184 main (AppDelegate.swift:22)
78 libdyld.dylib                  0x18710ebb4 start + 4

Some of the crash reports have different trace before the 14th step (calling function from RequestManager), so it crashes from different places of the app.

The problem is always in calling request getter of the Request.swift (line 108) while validation. Did some investigation, and I think it caused during bridging between swift/obj-c. And maybe converting a computed property into stored one could help, but since I cannot reproduce it I can't be sure either.

Any suggestions on how to fix or at least investigate the issue are highly appreciated!

Alamofire Environment

Alamofire version: 4.7.3, 4.8.1
Xcode version: 10.1
Swift version: 4.2
Platform(s) running Alamofire: iOS
macOS version running Xcode: 10.14.3

[rnkyr]

It looks like the problem lays in the debugging tool we're using. Sorry for bothering

[jshier]

Yes, the underlying C++ implementation of NSURLRequest has threading issues when touched from threads apart from the creating thread, leading to issues with tools that swizzle their way into the networking stack, as well as Alamofire itself sometimes. Alamofire 5 has a specific fix for crashes like this where it copies the request before taking it off the creating queue, which seems to help.

[rnkyr]

thank you for pointing it, will try

[wgrand]

Is there a workaround until Alamofire 5 is released?

[jshier]

@wgrand It's not certain what's causing this particular crash. If it is a queueing issue, one option might be to ensure all of your URLRequest creation is happening on the same queue. In Alamofire 4, request creation is synchronous on the calling queue, so you may need to ensure that request is always called on the same queue. Additionally, if you're creating URLRequests manually, copying them before dispatching to another queue might fix the issue.