JVM crash/StackOverflow when merging observables using mergeWith

[mp911de]

JVM crashes when chaining a lot of Observables using mergeWith (tried to chain 1000 observables).

Crash report

siginfo:si_signo=SIGSEGV: si_errno=0, si_code=1 (SEGV_MAPERR), si_addr=0x0000000000000008

Stack: [0x00000001074c1000,0x00000001075c1000],  sp=0x00000001074d7b60,  free space=90k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.dylib+0x40ae31]
V  [libjvm.dylib+0x49e13a]
V  [libjvm.dylib+0x49e275]
v  ~RuntimeStub::StackOverflowError throw_exception
v  ~StubRoutines::call_stub
V  [libjvm.dylib+0x2c5186]
...
V  [libjvm.dylib+0x2bf655]
j  rx.internal.operators.OperatorMerge$InnerSubscriber.emit(Ljava/lang/Object;Z)V+145
j  rx.internal.operators.OperatorMerge$InnerSubscriber.onNext(Ljava/lang/Object;)V+3
j  rx.internal.operators.OperatorMerge$InnerSubscriber.emit(Ljava/lang/Object;Z)V+133
j  rx.internal.operators.OperatorMerge$InnerSubscriber.onNext(Ljava/lang/Object;)V+3
j  rx.internal.operators.OperatorMerge$InnerSubscriber.emit(Ljava/lang/Object;Z)V+133
...

See https://gist.github.com/mp911de/fd8cd7c35c67fddb0c81 for full crash report

Observed crash when running in debug mode. If running without debug, the JVM just hangs.
Java: 1.8.0_40
RxJava: 1.0.11

Code to reproduce:

Observable<String> observable = Observable.empty();
for (int i = 0; i < 1000; i++) {
    observable = observable.mergeWith(Observable.just("my string"));
}
observable.last().toBlocking().first();

Workaround:

List<Observable<String>> observables = new ArrayList<>();
for (int i = 0; i < 1000; i++) {
    observables.add(Observable.just("my string"));
}
Observable.merge(observables).last().toBlocking().first();

[akarnokd]

This is the drawback of long chains operators. You should use the workaround whenever possible or use
the merge(Observable<Observabe<T>>) overload with a PublishSubject if the number of inner Observables is not known upfront.

[mp911de]

I was afraid of that. Thanks.