Signal 10-11
Danielle Just
I've been reading the other posts on tracking down the reasons for getting a SIGSEGV in an Android app. I plan to scour my app for possible NullPointers related to Canvas use, but my SIGSEGV barfs up a different memory address each time. Plus I've seen code=1 and code=2. If the memory address was 0x00000000, I'd have a clue it is a NullPointer.
I have a suspect, but I'm not keen on experimenting with it yet. My app uses the OSMDroid API for offline mapping. The OverlayItem class represents markers/nodes on the map. I have a Service that collects data via the network to populate the OverlayItem which are then displayed on the map. In an effort to simplify my design, I extended OverlayItem into my own NodeOverlayItem class, which includes some addition attributes I use in the UI Activity and in the Service. This gave me a single point of Item information for the UI and Service. I used Intents to broadcast to the Activity to refresh the UI map when something changed. The Activity binds to the Service and there's a Service method to get the list of NodeOverlayItem's. I think it might be the OSMDroid API's use of OverlayItem, and my Service updating node information at the same time. (a concurrency issue)
As I write this I think that's really the problem. The headache isn't splitting out the Node and OverlayItem from NodeOverlayItem, it's that the Activity will need some data from the Node, that the Service holds. Plus when the Activity is created (onResume, etc...) the OverlayItem objects will need to be re-created from the Node data that the Service has been maintaining while the Activity was away. e.g. You start the app, the Service collects data, the UI displays it, you go to Home, then back to the app, the Activity will need to pull and re-create the OverlayItem's from the latest Service node data.
UPDATEHere's the latest crash captured during a debug session. I have 3 of these devices being used for testing and they don't all crash reliably when I'm developing and testing. I included a bit extra just so the GC logging could be noted. You can see the problem is probably not related to memory exhaustion.
Just for an update. I think I was doing Android native build from the whole-source-tree for quite a long time, until today I have myself carefully read the NDK documents. Ever since the release NDK-r6, it has provided a utility called ndk-stack.
To do this, you will first need a directory containing symbolic versions of your application's shared libraries. If you use the NDK build system (i.e. ndk-build), then these are always located under $PROJECT_PATH/obj/local/, where stands for your device's ABI (i.e. armeabi by default).
As of now, ndk-stack doesn't handle libraries that don't have debug information in them. It may be useful to try to detect the nearest function entry point to a given PC address (e.g. as in the libc.so example above).
The libcrypto.so in my dump kind of clued me in. I do a MD5 hash of packet data when trying to determine if I've already seen the packet, and skipping it if I had. I thought at one point this was an ugly threading issue related to tracking those hashes, but it turned out it was the java.security.MessageDigest class! It's not thread safe!
I guess the lesson I can impart to those that were in my situation is, even if you're a 100% Java application, pay attention to the native library and symbol noted in the crash dump for clues. Googling for SIGSEGV + the lib .so name will go a lot farther than the useless code=1, etc... Next think about where your Java app could touch native code, even if it's nothing you're doing. I made the mistake of assuming it was a Service + UI threading issue where the Canvas was drawing something that was null, (the most common case I Googled on SIGSEGV) and ignored the possibility it could have been completely related to code I wrote that was related to the lib .so in the crash dump. Naturally java.security would use a native component in libcrypto.so for speed, so once I clued in, I Googled for Android + SIGSEGV + libcrypto.so and found the documented issue.
I was getting this error by saving an object to the shared preferences as a gson converted string. The gson String was no good, so retrieving and deserializing the object was not actually working correctly. This meant any subsequent accesses to the object resulted in this error. Scary :)
Your application is accessing memory outside of its address space. This is most likely an invalid pointer access. SIGSEGV = segmentation fault in native code. Since it is not occurring in Java code you won't see a stack trace with details. However, you may still see some stack trace information in the logcat if you look around a bit after the application process crashes. It will not tell you the line number within the file, but will tell you which object files and addresses were in use in the call chain. From there you can often figure out which area of the code is problematic. You can also setup a gdb native connection to the target process and catch it in the debugger.
Finally I disable Instant Run and now I am not getting this issue again.Now my application is working after enabling instant run also. It may be the instant run problem, Try with disabling and enabling instant run
I had this issue in Android Studio when tried "Apply changes and restart Activity", since then the app wouldn't start. The reason was I tried this one may be inside the fragment or so, but I had to restart my phone which I used for testing my app, and then the issue was gone.
I've struggled this for hours and finally just went into the storage details of the app I'm debugging and did "clear data". It ran fine afterwards. In my case, it was some strange google services gms bug.
Now I was trying to access that code which was returning native string to me, before processing the the string I had set its default value as nullptr. Now upon retrieving its value in Java code ran into this issue.
For me that issue was due to a bad cast between two activities.I recently moved this method from Activity1 to another 2. Doing so, the refactor left this explicit cast as it was before. So instead of doing
I had this issue with a package that was added to my app (FancyShowCaseView) and caused this problem on pre-lolipop. that package was written in kotlin and my main codes were written in java. so now I'm checking version in pre-lolipop and don't let its class to be executed. temporary solved the problem.check this out if you have similar problem like me
For anyone getting such an error in their Xamarin projects, it might be worth a try to pinpoint the interaction required to cause the issue (such as tapping a button) and put a try-catch block to get the managed exception from it. In my case, Android Fatal signal 11 (SIGSEGV) error was caused originally by a managed C# exception that could be easily fixed. I don't understand why Xamarin doesn't report the managed exception to the debug output though.
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Programmed death 1 (PD-1) is an inhibitory molecule expressed on activated T cells; however, the biological context in which PD-1 controls T cell tolerance remains unclear. Using two-photon laser-scanning microscopy, we show here that unlike naive or activated islet antigen-specific T cells, tolerized islet antigen-specific T cells moved freely and did not swarm around antigen-bearing dendritic cells (DCs) in pancreatic lymph nodes. Inhibition of T cell antigen receptor (TCR)-driven stop signals depended on continued interactions between PD-1 and its ligand, PD-L1, as antibody blockade of PD-1 or PD-L1 resulted in lower T cell motility, enhanced T cell-DC contacts and caused autoimmune diabetes. Blockade of the immunomodulatory receptor CTLA-4 did not alter T cell motility or abrogate tolerance. Thus, PD-1-PD-L1 interactions maintain peripheral tolerance by mechanisms fundamentally distinct from those of CTLA-4.
Note that the four signals are slightly different. The signals from pins 11 and 6 are the inverse of each other, and the signals from pins 10 and 5 are the inverse of each other. All signals have a duty cycle of 50%, BUT the time that signals 10 and 5 first change is time shifted depending on the desired output duty cycle (dutyCycles variable, which is the amount of time that the output signal is on positively or negatively in the half-cycle). Hence, the port manipulation code must take into account the dutyCycles variable to adjust the timing, and hopefully be adaptable to accepting a changing value of dutyCycles in future implementations. Right now, though, I just want to get this working for a constant value of dutyCycles.
Also, the formulas calculating the delays are as they are since onDelay is the amount of time the output signal is positive and negative in its two half-cycles, and offDelay is just the remaining half-cycle time. The output signal is the same frequency as the other four signals, and it is not in the code as these four signals are the control signals for an external circuit that creates the output signal.
All signals have a duty cycle of 50%, BUT the time that signals 10 and 5 first change is time shifted depending on the desired output duty cycle (dutyCycles variable, which is the amount of time that the output signal is on positively or negatively in the half-cycle).
What I mean by "high accuracy" is that if the frequency is given to be 8 kHz, the output signal will be 8 kHz as well, not less than 8 kHz. To put it as a number, within 50 Hz of the host frequency would be ideal. Right now, if I enter in 5 kHz, the output frequency is approximately 4.6 kHz, and if I enter in 10 kHz, the output frequency is approximately 8.5 kHz.
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I apologize if my previous picture wasn't clear. But the signals generated by the Arduino are indeed two-level. In the previous pictures, the Arduino signals were labeled by their variable names (InvPin1, InvPin2, InvPin3, and InvPin4) just as in the code I shared originally. In this picture, I will use their actual pin numbers if that makes it more clear.