Rare crash on startup

[pfleeter]

We are using Unity 2017.4.4 and have a user on Android 8 that was able to send us this log. As best I can make out, it looks like NewGlobalRef is failing because the reference being passed in is already invalid somehow.

07-13 16:20:35.402  2604  2635 F zygote  : indirect_reference_table.cc:58] JNI ERROR (app bug): accessed deleted Global 0x2c86

07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514] Runtime aborting...
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514] Aborting thread:
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514] "UnityMain" prio=5 tid=13 Runnable
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   | group="" sCount=0 dsCount=0 flags=4 obj=0x12c41270 self=0xd50d4600
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   | sysTid=2635 nice=0 cgrp=default sched=0/0 handle=0xc76ff970
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   | state=R schedstat=( 1530772739 28633897 1766 ) utm=136 stm=17 core=5 HZ=100
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   | stack=0xc75fd000-0xc75ff000 stackSize=1038KB
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   | held mutexes= "abort lock" "mutator lock"(shared held)

07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #00 pc 002c521f  /system/lib/libart.so (_ZN3art15DumpNativeStackERNSt3__113basic_ostreamIcNS0_11char_traitsIcEEEEiP12BacktraceMapPKcPNS_9ArtMethodEPv+130)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #01 pc 00356cd1  /system/lib/libart.so (_ZNK3art6Thread9DumpStackERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEbP12BacktraceMapb+200)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #02 pc 003531a3  /system/lib/libart.so (_ZNK3art6Thread4DumpERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEbP12BacktraceMapb+34)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #03 pc 00343b9d  /system/lib/libart.so (_ZNK3art10AbortState10DumpThreadERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEEPNS_6ThreadE+28)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #04 pc 0034397f  /system/lib/libart.so (_ZNK3art10AbortState4DumpERNSt3__113basic_ostreamIcNS1_11char_traitsIcEEEE+346)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #05 pc 00338877  /system/lib/libart.so (_ZN3art7Runtime5AbortEPKc+110)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #06 pc 00338f7f  /system/lib/libart.so (_ZN3art7Runtime7AborterEPKc+10)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #07 pc 003effad  /system/lib/libart.so (_ZN7android4base10LogMessageD1Ev+456)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #08 pc 001c8757  /system/lib/libart.so (_ZN3art22IndirectReferenceTable17AbortIfNoCheckJNIERKNSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE+166)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #09 pc 00234c63  /system/lib/libart.so (_ZNK3art22IndirectReferenceTable10GetCheckedEPv+266)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #10 pc 0023145b  /system/lib/libart.so (_ZN3art9JavaVMExt12DecodeGlobalEPv+10)
07-13 16:20:35.693  2604  2635 F zygote  : runtime.cc:514]   native: #11 pc 0035ab4b  /system/lib/libart.so (_ZNK3art6Thread13DecodeJObjectEP8_jobject+162)
07-13 16:20:35.694  2604  2635 F zygote  : runtime.cc:514]   native: #12 pc 0025fdf3  /system/lib/libart.so (_ZN3art3JNI12NewGlobalRefEP7_JNIEnvP8_jobject+374)
07-13 16:20:35.694  2604  2635 F zygote  : runtime.cc:514]   native: #13 pc 000064c5  /data/app/com.thirdtime.photofinishtwo-K8CqbIHzxiIdyy0X4xOY9g==/lib/arm/libnative-googlesignin.so (_ZN12googlesignin12GoogleSignIn16GoogleSignInImplC2EP8_jobject+32)
07-13 16:20:35.694  2604  2635 F zygote  : runtime.cc:514]   native: #14 pc 00006ac7  /data/app/com.thirdtime.photofinishtwo-K8CqbIHzxiIdyy0X4xOY9g==/lib/arm/libnative-googlesignin.so (_ZN12googlesignin12GoogleSignInC1EP8_jobject+22)
07-13 16:20:35.694  2604  2635 F zygote  : runtime.cc:514]   native: #15 pc 0000616b  /data/app/com.thirdtime.photofinishtwo-K8CqbIHzxiIdyy0X4xOY9g==/lib/arm/libnative-googlesignin.so (GoogleSignIn_Create+30)
07-13 16:20:35.694  2604  2635 F zygote  : runtime.cc:514]   native: #16 pc 0211ce54  /data/app/com.thirdtime.photofinishtwo-K8CqbIHzxiIdyy0X4xOY9g==/lib/arm/libil2cpp.so (???)

[pfleeter]

Could it be that the helper class is garbage collected before it's global reference is created?

I'm not very familiar with this type of JNI coding, but I read here that, "Local references become invalid when the execution returns from the native method in which the local reference is created."

So maybe there is a small window for problems, and the Global Ref needs to be created before FindClass returns.

  if (!helper_clazz_) {
    // Find the java  helper class and initialize it.
    helper_clazz_ = FindClass(HELPER_CLASSNAME, activity);

    assert(helper_clazz_);

    if (helper_clazz_) {
      helper_clazz_ = (jclass)env->NewGlobalRef(helper_clazz_);