search

launchdarkly / ios-client-sdk

LaunchDarkly Client-side SDK for iOS (Swift and Obj-C)
https://docs.launchdarkly.com/sdk/client-side/ios
Other
70 stars 84 forks source link

Fix crash with findChangedFlagKeys and symmetricDifference #179

Closed aelkady closed 5 years ago

aelkady commented 5 years ago

Background

We are seeing two bad crashes in the LaunchDarkly SDK in our app. The stacktraces are below:

Crashed: com.apple.main-thread
0  LaunchDarkly                   0x10247cf10 $ss17_dictionaryUpCastySDyq0_q1_GSDyxq_GSHRzSHR0_r2_lFSS_12LaunchDarkly11FeatureFlagVSSypTg5 + 168
1  LaunchDarkly                   0x10247fe64 $s12LaunchDarkly18FlagChangeNotifierC011findChangedC4Keys33_AAE936965AC09485A5BF28D82C960463LL8oldFlags03newP0SaySSGSDySSAA07FeatureC0VG_AKtFTf4nnd_n + 168
2  LaunchDarkly                   0x10247a9a0 $s12LaunchDarkly18FlagChangeNotifierC15notifyObservers4user8oldFlags0iC6SourceyAA6LDUserV_SDySSAA07FeatureC0VGAA011LDFlagValueK0OtF + 300
3  LaunchDarkly                   0x10247d388 $s12LaunchDarkly18FlagChangeNotifierCAA0cD9NotifyingA2aDP15notifyObservers4user8oldFlags0jC6SourceyAA6LDUserV_SDySSAA07FeatureC0VGAA011LDFlagValueL0OtFTW + 20
4  LaunchDarkly                   0x1024a2d60 $s12LaunchDarkly8LDClientC27updateCacheAndReportChanges33_14C52C04C80D938C2FE76924F7908AD1LL4user8oldFlags0R10FlagSourceyAA6LDUserV_SDySSAA07FeatureT0VGAA011LDFlagValueU0OtF + 456
5  LaunchDarkly                   0x1024a7a7c $s12LaunchDarkly8LDClientC18onFlagSyncComplete33_14C52C04C80D938C2FE76924F7908AD1LL6resultyAA0eF6ResultO_tFyycfU0_TA + 96
6  LaunchDarkly                   0x10248cc80 $s12LaunchDarkly9FlagStoreC06deleteC00E10Dictionary10completionySDySSypG_yycSgtFyycfU_6$deferL_yyFyycfU_TA + 28
7  LaunchDarkly                   0x102485600 $sIeg_IeyB_TR + 28
8  libdispatch.dylib              0x19befca38 _dispatch_call_block_and_release + 24
9  libdispatch.dylib              0x19befd7d4 _dispatch_client_callout + 16
10 libdispatch.dylib              0x19beab004 _dispatch_main_queue_callback_4CF$VARIANT$mp + 1068
11 CoreFoundation                 0x19c44dec0 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
12 CoreFoundation                 0x19c448df8 __CFRunLoopRun + 1924
13 CoreFoundation                 0x19c448354 CFRunLoopRunSpecific + 436
14 GraphicsServices               0x19e64879c GSEventRunModal + 104
15 UIKitCore                      0x1c89ffb68 UIApplicationMain + 212
16 *******                        0x100e95438 main (main.m:16)
17 libdyld.dylib                  0x19bf0e8e0 start + 4
Crashed: com.apple.main-thread
0  LaunchDarkly                   0x1060b5b34 $sShyShyxGqd__nc7ElementQyd__RszSTRd__lufCSS_SD4KeysVySS12LaunchDarkly11FeatureFlagV_GTg5 + 32
1  LaunchDarkly                   0x1060b57d4 $sSD12LaunchDarklySSRszrlE19symmetricDifferenceySaySSGSDySSypGFAA11FeatureFlagV_Tg5 + 60
2  LaunchDarkly                   0x1060d7e70 $s12LaunchDarkly18FlagChangeNotifierC011findChangedC4Keys33_AAE936965AC09485A5BF28D82C960463LL8oldFlags03newP0SaySSGSDySSAA07FeatureC0VG_AKtFTf4nnd_n + 180
3  LaunchDarkly                   0x1060d29a0 $s12LaunchDarkly18FlagChangeNotifierC15notifyObservers4user8oldFlags0iC6SourceyAA6LDUserV_SDySSAA07FeatureC0VGAA011LDFlagValueK0OtF + 300
4  LaunchDarkly                   0x1060d5388 $s12LaunchDarkly18FlagChangeNotifierCAA0cD9NotifyingA2aDP15notifyObservers4user8oldFlags0jC6SourceyAA6LDUserV_SDySSAA07FeatureC0VGAA011LDFlagValueL0OtFTW + 20
5  LaunchDarkly                   0x1060fad60 $s12LaunchDarkly8LDClientC27updateCacheAndReportChanges33_14C52C04C80D938C2FE76924F7908AD1LL4user8oldFlags0R10FlagSourceyAA6LDUserV_SDySSAA07FeatureT0VGAA011LDFlagValueU0OtF + 456
6  LaunchDarkly                   0x1060ffa7c $s12LaunchDarkly8LDClientC18onFlagSyncComplete33_14C52C04C80D938C2FE76924F7908AD1LL6resultyAA0eF6ResultO_tFyycfU0_TA + 96
7  LaunchDarkly                   0x1060e4c80 $s12LaunchDarkly9FlagStoreC06deleteC00E10Dictionary10completionySDySSypG_yycSgtFyycfU_6$deferL_yyFyycfU_TA + 28
8  LaunchDarkly                   0x1060dd600 $sIeg_IeyB_TR + 28
9  libdispatch.dylib              0x20293ca38 _dispatch_call_block_and_release + 24
10 libdispatch.dylib              0x20293d7d4 _dispatch_client_callout + 16
11 libdispatch.dylib              0x20291d9e4 _dispatch_main_queue_callback_4CF$VARIANT$armv81 + 1008
12 CoreFoundation                 0x202e8ec1c __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
13 CoreFoundation                 0x202e89b54 __CFRunLoopRun + 1924
14 CoreFoundation                 0x202e890b0 CFRunLoopRunSpecific + 436
15 GraphicsServices               0x20508979c GSEventRunModal + 104
16 UIKitCore                      0x22f6f5978 UIApplicationMain + 212
17 *******                        0x104ad14c0 main (main.m:16)
18 libdyld.dylib                  0x20294e8e0 start + 4

These are the stacktraces we get from Crashlytics. I was unable to produce these crashes locally but my suspicion based on the stacktrace is that they are triggered when a feature flag is deleted on LaunchDarkly and the iOS client is updating its flags as a result.

For both crashes we are getting the following crash reason:

Crashed: com.apple.main-thread
EXC_BAD_ACCESS KERN_INVALID_ADDRESS 0x0000000000000000

Potential Findings

This tells me that something in either findChangedFlagKeys or symmetricDifference is trying to access a deallocated object. I have included in this PR measures to mitigate against this.

Version bump

I have also included in this PR a version bump in the podspec - I would like to respectfully ask that this change come with a version bump to the LaunchDarkly SDK as well as a push to the Cocoapods trunk so that we can take advantage of this fix as quickly as possible.

torchhound commented 5 years ago

Hi @aelkady, thanks for the PR! We've been experiencing similar issue in internal testing. We'll evaluate your solution and get back to you ASAP.

torchhound commented 5 years ago

We have identified and reproduced this issue internally. We have a partial solution thanks in part to @aelkady. We will have an update to the iOS Client SDK out very soon. Thank you for your patience.

torchhound commented 5 years ago

@aelkady We just released an update that fixes this issue.

aelkady commented 5 years ago

@torchhound thanks for the update! Will be sure to install it and report back if there are any more issues.

Thanks again, especially for the quick turnaround time on this! 😄