Segmentation fault in NativeMap$update on Android

[matteblair]

TO REPRODUCE THE ISSUE, FOLLOW THESE STEPS:

• Repeatedly close and re-open an Activity or Fragment containing a MapView.

RESULT:

Sometimes the process will exit with a segmentation fault in NativeMap$update.

EXPECTED RESULT:

The process runs and exits normally.

ENVIRONMENT:

• Android
• Current master (434f27a)

OTHER:

• This was first described in another issue (Memory allocation failure in MapController init #2215)
• This issue does not occur with the last released version (0.13.0).

Several stack traces of these segmentation faults have been provided by @tapetis:

SEGV_ACCERR-1.txt
SEGV_ACCESS-2.txt
SEGV_MAPERR-1.txt
SEGV_MAPERR-2.txt
SEGV_MAPERR-3.txt

[matteblair]

Unfortunately, I have been unable to reproduce this so far. However I do believe this is a real bug - there should be no way to configure or use the Tangram Android SDK that produces a segfault.

I currently believe that the problem is a thread-synchronization issue between MapController and MapRenderer that leads to MapRenderer calling native methods after the native map object has been freed. I am basing this on 3 clues:

• The segfault occurs inconsistently, which is typical of multi-threading issues.
• It occurs at the start or end of the activity, which is when MapController creates and frees native objects.
• It occurs on current builds, but not on the 0.13.0 release - after that release I made some big refactors to the way native map objects are handled (Android JNI Refactor #2187, Reduce allocations in JNI invocations #2206)

[matteblair]

I believe this has been resolved by #2223. If this crash is observed again, this issue should be re-opened.