IssueTracker

Version: laster master.
=> I've reproduced this in Android Studio 3.2.1, but have also been running the code from latest master directly and was able to reproduce there as well.

We've discovered this issue thanks to LeakCanary (https://github.com/square/leakcanary/issues/1124), but I've been able to successfully reproduce it in Android Studio.

Steps:

* Get a heap dump that misses a Thread object (more on that below). Those are sometimes generated by Android (not sure why). LeakCanary users have uploaded their heap dumps, here are two: 1) https://drive.google.com/file/d/1c3R1CsBltauNsiCsmh14ag-YoeBP8umB/view?usp=sharing 2) https://drive.google.com/file/d/1Y0dGnwYhOXEWkkkqTdoe6cByT3JA_nrQ/view?usp=sharing
* Load the Heap dump in Android Studio.
=> The profiler tab says "Selected Capture has no content"
* Open the same Heap Dump in YourKit Java Profiler, it parses it fine.

I've been debugging through the perflib code, here's what I think is happening:

* When parsing a heap dump, we normally first read a ROOT_THREAD_OBJECT and call HprofParser.loadThreadObject(), that thread gets added to the threads of the current heap.
* Then we get a ROOT_NATIVE_STACK and call HprofParser.loadNativeStack(), which reads the thread serial number and uses that to retrieve the ThreadObj from the current heap.
* Unfortunately, these heap dumps have a ROOT_NATIVE_STACK but no corresponding ROOT_THREAD_OBJECT. I've looked in depth at the second one listed above, it has 700 ROOT_NATIVE_STACK tags all referencing thread serial number 2. Note that YourKit does not show a thread 2, so they likely just ignore this issue. Thread serial number 1 is the main thread, so I wonder what that second missing thread is.
* Because there's no ROOT_THREAD_OBJECT to retrieve in HprofParser.loadNativeStack(), mSnapshot.getThread(threadSerialNumber) returns null and we get an NullPointerException on thread.mStackTrace
* The exception bubbles up, it's caught in HprofParser.parse(), logged and silently ignored. https://android.googlesource.com/platform/tools/base/+/studio-master-dev/perflib/src/main/java/com/android/tools/perflib/heap/HprofParser.java#211 . From the outside, everything looks fine, except there's 0 data in the heap dump.