Debugging native code in android app using the android ndk gdb.

This is a small tutorial which combines the information that got over Google for making use of the "ndk-gdb" present in the Android NDK

AVD: 2.3.3 API Level 10
NDK: r6b (or) r7

Prerequisites:
Basic knowledge of Android ndk
Knowledge of GDB


Steps for using the android gdb:
1) Go to the build_binary.mk file present in the location ...\android-ndk\build\core\build-binary.mk and do the following changes (present in the last lines of the build-binary.mk file)


#Commented - This is the original code
#    $(hide) $(call cmd-strip, $(PRIVATE_DST))
#Added
ifneq ($(APP_OPTIM),debug)
    @ echo "Stripping the library for the release mode....."
    $(hide) $(call cmd-strip, $(PRIVATE_DST))
endif

2) Build the library with ndk-build NDK_DEBUG=1(Build command) and LOCAL_EXPORT_CFLAGS += -g ( in Android.mk of your application) and APP_OPTIM=debug (of your Application.mk). And also set this flag in your AndroidManifest.xml file "android:debuggable="true"" and sdk version in the same AndriodManifest.xml file as
"uses-sdk android:minSdkVersion="10" android:targetSdkVersion="9" "

3) Open the command prompt in the root folder (parent of jni (or) libs (or) obj)

Ex: CallbackJava here

4) Now if you are in Linux machine it's fine, else go to shell prompt by making use of the cygwin in windows machine. and you will get a prompt like this

sh-4.1$

Tip: It will be better if "bin" folder of the cygwin is added to the "path" environmental variable in windows.

5) Now run the command in shell prompt like below

After executing the above command make sure that you will get the "(gdb)" prompt and not the following error 

    ERROR: Could not extract package's data directory. Are you sure that
           your installed application is debuggable?
    sh-4.1$ 

If you are getting the error, either device is not debuggable or your package is not built with debugging information. Please make sure step 2.

6) Once you get the “(gdb)” prompt set the break point  Ex: break : and then type “c” or “continue” and hit enter. Application starts running and the moment it hits the break point you will be able to see in the command prompt. And debug as usual like gdb.

Once it hits the break point like showed in the above image you can make use of gdp commands "step, next, list....." and so on and start debugging.

Observations:
This ndk-gdb is bit slow. Sorry lying its tooooo slow :D :) :P

Happy debugging.....



FAQ:
1) If you are getting an error message like
"No symbol table is loaded.  Use the "file" command."
It can be due to creation of the gdb.setup problem.
Try to convert the file to unix format by making use of the dos2unix command.
Ex: dos2unix gdb.setup

2) Code changes for the Android NDK - 8c for build_binary.mk file in step 1.

$(LOCAL_INSTALLED): $(LOCAL_BUILT_MODULE) clean-installed-binaries
@$(HOST_ECHO) "Install        : $(PRIVATE_NAME) => $(call pretty-dir,$(PRIVATE_DST))"
$(hide) $(call host-install,$(PRIVATE_SRC),$(PRIVATE_DST))
#Suman - Start
#Commented
# $(hide) $(PRIVATE_STRIP_CMD)
#Added
@ echo "APP_OPTIM is............................. $(APP_OPTIM)"
ifneq ($(APP_OPTIM), debug)
@ echo "Stripping the library for the release mode....."
$(hide) $(PRIVATE_STRIP_CMD)
endif
#Suman - End

$(call generate-dir,$(NDK_APP_DST_DIR))
$(LOCAL_INSTALLED): $(NDK_APP_DST_DIR)