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I have set up debugging in Eclipse for native code using the Android NDK (on Windows XP, with Cygwin) to the stage where I can set breakpoints in both Java and native code and the debugger will break at them correctly. My issue is that when stepping through the native code, I will often get segmentation faults/SIGILLs that do not occur when continuing past the breakpoint instead.

  • My application is debuggable as defined in AndroidManifest.xml
  • I have altered the (NDK)/build/core/build-binary.mk to prevent it from stripping out debug symbols when APP_OPTIM is defined as debug, which it is in the Application.mk file in my jni directory
  • I have defined LOCAL_CFLAGS := -g -O0 in the Android.mk file, and I have also tried each of these flags individually

I have read that this problem is to do with the optimised code generated, but turning optimisation off with -O0 has no impact on my issue. I have also come across using the NDK_BUILD=1 flag when building, but defining debuggable=true in AndroidManifest.xml apparently has the same effect.

I have tried this both on an emulator (running 2.3.3) and on a device (running 2.2 - which surprisingly didn't have the thread issues I expected), with similar results (although if I remember correctly, the failures happened at different points in code).

Does anyone have any insight into possible fixes/steps I could try, and/or have been able to successfully step through native code with no issues?

Thanks very much

Edit: This was never really solved, but for anyone who wants to take a look at my guide for NDK debugging, you can find it here.

Edit 2: The answers I got to this question came once new versions of the NDK had come out, and this question may now be redundant. My guide may still work, but I haven't been using the NDK for a while so I cannot vouch for its continued correctness. I have accepted the answer I have as all three basically say the same thing, and that was the first one to be submitted.

epochengine
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    Hi. Were you ever able to get Native debugging working correctly? For some reason I am not able to step into (F5) any native functions. – Kevin Parker Sep 06 '11 at 03:32
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    @Kevin Hi. The guide I have linked to does set up the NDK debugging to a working state. However, as you've said, it doesn't handle stepping "through" the JNI. But as it will handle breakpoints set in both Java and C/C++, you can get the equivalent by setting a breakpoint at the entry point to your C/C++ function called by the NDK, and continue (F8) to that breakpoint where you want to step in to the native code. Hope that helps. – epochengine Sep 06 '11 at 08:54
  • I've observed this as well. It seems to occur more if I the startup breakpoint set. If I run a application then attach (even with breakpoints present) I do not see the issue. In any case, it's fairly flaky. – NuSkooler Nov 09 '11 at 22:47
  • I too have the setup for NDK Debugging and i dont receive any seg fault for when i hit the breakpoint and try to go step through the code.Mostly on emulater it is too slow and connection to gdbserver timesout but seg fault is not the case. Another case is dont debug java and Native code together in Elcipse. – Praveen Apr 27 '12 at 06:31
  • My intuition is that it's the fault of the gdbserver that I assume eclipse is causing to be run to debug your code. It is touching some memory carelessly in the process, which is not in fact valid. – mcr May 11 '12 at 04:51
  • I notice that you have NDK_BUILD=1, but it should be NDK_DEBUG=1 – JonnyBoy May 12 '12 at 21:22

3 Answers3

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If it works for armeabi and not for armeabi-v7a, this should be a build issue. Unzip the apk file in the bin directory and check the library files in both the armeabi and armeabi-v7a are the same.

user973743
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One thing that I've noticed is that armeabi-v7a doesn't work well for debugging native code on certain devices. Try building for only armeabi and see if that helps.

JonnyBoy
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compile the c++ source files with -march=armv4

In build/core/combo/arm/yourarch.mk put -march=armv4 and then do mm -B showcommands to check if it was used.

Then gdbserver can handle it.

Adam Michnik
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