[RemoteConfig] Crash if initializing after app start

[tecbot]

[REQUIRED] Step 2: Describe your environment

• Xcode version: 10.2.1
• Firebase SDK version: 6.4.0
• Firebase Component: RemoteConfig
• Component version: 4.2.0

[REQUIRED] Step 3: Describe the problem

Stack trace:

EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000fca8c6b30
-[RCNConfigExperiment initWithDBManager:]

Crashed: com.apple.main-thread
0  libobjc.A.dylib                0x180d87530 objc_msgSend + 16
1  Runner                         0x10284c130 -[RCNConfigExperiment initWithDBManager:] + 4376871216
2  Runner                         0x102841920 -[FIRRemoteConfig initWithAppName:FIROptions:namespace:DBManager:configContent:] + 4376828192
3  Runner                         0x1028450e8 -[FIRRemoteConfigComponent remoteConfigForNamespace:] + 4376842472
4  Runner                         0x102841660 +[FIRRemoteConfig remoteConfigWithFIRNamespace:app:] + 4376827488
5  Runner                         0x102841720 +[FIRRemoteConfig remoteConfig] + 4376827680
6  Runner                         0x102905bec -[FirebaseRemoteConfigPlugin handleMethodCall:result:] + 39 (FirebaseRemoteConfigPlugin.m:39)
7  Flutter                        0x102f55ba8 (Missing)
8  Flutter                        0x102ef96a4 (Missing)
9  Flutter                        0x102f48ad0 (Missing)
10 Flutter                        0x102f04534 (Missing)
11 Flutter                        0x102f07cc8 (Missing)
12 CoreFoundation                 0x181b27650 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 28
13 CoreFoundation                 0x181b27380 __CFRunLoopDoTimer + 864
14 CoreFoundation                 0x181b26bb4 __CFRunLoopDoTimers + 248
15 CoreFoundation                 0x181b21b04 __CFRunLoopRun + 1844
16 CoreFoundation                 0x181b210b0 CFRunLoopRunSpecific + 436
17 GraphicsServices               0x183d2179c GSEventRunModal + 104
18 UIKitCore                      0x1ae38d978 UIApplicationMain + 212
19 Runner                         0x102601d48 main + 5 (AppDelegate.swift:5)
20 libdyld.dylib                  0x1815e68e0 start + 4

Steps to reproduce:

After upgrading Firebase dependencies from 6.3.0 to 6.4.0 and RemoteConfig from 4.1.0 to 4.2.0 we are getting crashes directly on app start. If the crash happen the next app starts are working. After some time (~1 hour) the crash happen again. We are using Firebase in a Flutter project.

Relevant Code:

Entry point: https://github.com/flutter/plugins/blob/master/packages/firebase_remote_config/ios/Classes/FirebaseRemoteConfigPlugin.m#L39

[ryanwilson]

Hi @tecbot - looking into this right away. Some quick questions as I start investigating:

• Does this happen on any specific iOS version, or all of them?
• Does it happen on both device and simulator?
• Can you enable Zombies in your application and see where it's failing? It looks like it's trying to access an already deallocated instance of something (based on KERN_INVALID_ADDRESS)

Thanks, and sorry for the troubles!

[ryanwilson]

I haven't been able to reproduce this using a non-Flutter app, looking at setting up Flutter in order to try it out. If you have a plain reproduction (without GoogleService-Info.plist) you could share, it'd be very helpful 🙂

[mouness2020]

I have 2 crashes in same class in my apps :
first one
RCNConfigExperiment initWithDBManager
Fatal Exception: NSInvalidArgumentException-[__NSCFString setTimeZone:]: unrecognized selector sent to instance 0x2800f36f0

second one
-[RCNConfigExperiment initWithDBManager:]
Crashed: com.google.perf.FPREventsQueue
EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x7265567733237863

com.test.app_issue_crash_f34c5ae3e6924654a8390f7336a46fd3_DNE_0_v2.txt
com.test.app_issue_crash_ed38c08906b044109d994521a23efeb5_DNE_0_v2.txt

 

[paulb777]

@mouness2020 Thanks for the additional detail.

@ryanwilson, @dmandar I suspect a thread safety issue with the static variable assigned the NSDateFormatter. One thread is creating another instance while another thread is sending the setTimeZone: message.

[mouness2020]

new crashes happen in version 6.4.0

com.newline.syarah_issue_crash_80e7ff5eea8b4185992b08670574f421_DNE_0_v2.txt
com.newline.syarah_issue_crash_6650134ac76d48528fa3660b4e8d130b_DNE_0_v2.txt
com.newline.syarah_issue_crash_af4f450837314836b968679b66abea0d_DNE_0_v2.txt
com.newline.syarah_issue_crash_debb40baeb19479188b8c0e74cf2316b_DNE_0_v2.txt

[ryanwilson]

Thanks folks for the extra information - I have a pending fix internally at cl/258032937.

We still haven't been able to reproduce this, so if anyone can provide reproduction steps so we can verify the fix works properly, it would be greatly appreciated.