Hacking on Chromium for Android from Eclipse (part 3)

In the previous posts we learnt how to code and debug Chromium for Android C++ code from Eclipse. In this post I’m going to explain how to open the ChromeShell Java code, so that you will be able to hack on it like you would in a normal Android app project. Remember, you will need to install the ADT plugin in Eclipse  and the full featured adb which comes with the standalone SDK from the official pageDon’t try to reuse the android sdk in “third_party/android_tools/sdk”.

Creating the Java project in Eclipse

Follow these instructions to create the Java project for ChromeShell (for instance):

  • File, New, Project…, Android, Android project from existing code
  • Choose “src/chrome/android/shell/java” as project root, because there’s where the AndroidManifest.xml is. Don’t copy anything to the workspace.
  • The project will have a lot of unmet package dependencies. You have to manually import some jars:
    • Right click on the project, Properties, Java build path, Libraries, Add external Jars…
    • Then browse to “src/out/Debug/lib.java” (assuming a debug build) and import these jars (use CTRL+click for multiple selection in the file chooser):
      • base_java.jar, chrome_java.jar, content_java.jar, dom_distiller_core_java.jar, guava_javalib.jar,
      • jsr_305_javalib.jar, net_java.jar, printing_java.jar, sync_java.jar, ui_java.jar, web_contents_delegate_android.jar
    • If you keep having problems, go to “lib.java”, run this script and find in which jar is the class you’re missing:
for i in *.jar; do echo "--- $i ---------------------"; unzip -l $i; done | most
  • The generated resources directory “gen” produced by Eclipse is going to lack a lot of stuff.
    • It’s better to make it point to the “right” gen directory used by the native build scripts.
    • Delete the “gen” directory in “src/chrome/android/shell/java” and make a symbolic link:
ln -s ../../../../out/Debug/chrome_shell_apk/gen .
    • If you ever “clean project” by mistake, delete the chrome_shell_apk/gen directory and regenerate it using the standard ninja build command
  • The same for the “res” directory. From “src/chrome/android/shell/java”, do this (and ignore the errors):
cp -sr $PWD/../res ./
cp -sr $PWD/../../java/res ./
  • I haven’t been able to solve the problem of integrating all the string definitions. A lot of string related errors will appear in files under “res”. By the moment, just ignore those errors.
  • Remember to use a fresh standalone sdk. Install support for Android 4.4.2. Also, you will probably need to modify the project properties to match the same 4.4.2 version you have support for.

And that’s all. Now you can use all the Java code indexing features of Eclipse. By the moment, you still need to build and install to the device using the command line recipe, though:

 ninja -C out/Debug chrome_shell_apk
 build/android/adb_install_apk.py --apk ChromeShell.apk --debug

Debugging Java code

To debug the Java side of the app running in the device, follow the same approach that you would if you had a normal Java Android app:

  • Launch the ChromeShell app manually from the device.
  • In Eclipse, use the DDMS perspective to locate the org.chromium.chrome.shell process. Select it in the Devices panel and connect the debugger using the “light green bug” icon (not to be mistaken with the normal debug icon available from the other perspectives).
  • Change to the Debug perspective and set breakpoints as usual.



Hacking on Chromium for Android from Eclipse (part 2)

In the previous post, I showed all the references to get the Chromium for Android source code, setup Eclipse and build the ChromeShell app. Today I’m going to explain how to debug that app running in the device.

Debugging from command line

This is the first step that we must ensure to have working before trying to debug directly from Eclipse. The steps are explained in the debugging-on-android howto, but I’m showing them here for reference.

Perform the “build Chrome shell” steps but using debug parameters:

 ninja -C out/Debug chrome_shell_apk
 build/android/adb_install_apk.py --apk ChromeShell.apk --debug

To avoid the need of having a rooted Android device, setup ChromeShell as the app to be debugged going to Android Settings, Debugging in your device. Now, to launch a gdb debugging session from a console:

 cd ~/ANDROID/src
 . build/android/envsetup.sh
 ./build/android/adb_gdb_chrome_shell --start

You will see that the adb_gdb script called by adb_gdb_chrome_shell pulls some libraries from your device to /tmp. If everything goes fine, gdb shouldn’t have any problem finding all the symbols of the source code. If not, please check your setup again before trying to debug in Eclipse.

Debugging from Eclipse

Ok, this is going to be hacky. Hold on your hat!

Eclipse can’t use adb_gdb_chrome_shell and adb_gdb “as is”, because they don’t allow gdb command line parameters. We must create some wrappers in $HOME/ANDROID, our working dir. This means “/home/enrique/ANDROID/” for me. The wrappers are:

Wrapper 1: adb_gdb

This is a copy of  ~/ANDROID/src/build/android/adb_gdb with some modifications. It calculates the same as the original, but doesn’t launch gdb. Instead, it creates two symbolic links in ~/ANDROID:

  • gdb is a link to the arm-linux-androideabi-gdb command used internally.
  • gdb.init is a link to the temporary gdb config file created internally.

These two files will make the life simpler for Eclipse. After that, the script prints the actual gdb command that it would have executed (but has not), and reads a line waiting for ENTER. After the user presses ENTER, it just kills everything. Here are the modifications that you have to do to the original adb_gdb you’ve copied. Note that my $HOME (~) is “/home/enrique”:

 # In the begining:
 # At the end:
 log "Launching gdb client: $GDB $GDB_ARGS -x $COMMANDS"

 rm /home/enrique/ANDROID/gdb
 ln -s "$GDB" /home/enrique/ANDROID/gdb
 rm /home/enrique/ANDROID/gdb.init
 ln -s "$COMMANDS" /home/enrique/ANDROID/gdb.init
 echo "---------------------------"

 exit 0

Wrapper 2: adb_gdb_chrome_shell

It’s a copy of ~/ANDROID/src/build/android/adb_gdb_chrome_shell with a simple modification in PROGDIR:


Wrapper 3: gdbwrapper.sh

Loads envsetup, returns the gdb version for Eclipse if asked, and invokes adb_gdb_chrome_shell. This is the script to be run in the console before starting the debug session in Eclipse. It will invoke the other scripts and wait for ENTER.

 cd /home/enrique/ANDROID/src
 . build/android/envsetup.sh
 if [ "X$1" = "X--version" ]
  exec /home/enrique/ANDROID/src/third_party/android_tools/ndk/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gdb --version
  exit 0
 exec ../adb_gdb_chrome_shell --start --debug
 #exec ./build/android/adb_gdb_chrome_shell --start --debug

Setting up Eclipse to connect to the wrapper

Now, the Eclipse part. From the “Run, Debug configurations” screen, create a new “C/C++ Application” configuration with these features:

  • Name: ChromiumAndroid 1 (name it as you wish)
  • Main:
    • C/C++ Application: /home/enrique/ANDROID/src/out/Debug/chrome_shell_apk/libs/armeabi-v7a/libchromeshell.so
    • IMPORTANT: From time to time, libchromeshell.so gets corrupted and is truncated to zero size. You must regenerate it by doing:

rm -rf /home/enrique/ANDROID/src/out/Debug/chrome_shell_apk
ninja -C out/Debug chrome_shell_apk

    • Project: ChromiumAndroid (the name of your project)
    • Build config: Use active
    • Uncheck “Select config using C/C++ Application”
    • Disable auto build
    • Connect process IO to a terminal
  • IMPORTANT: Change “Using GDB (DSF) Create Process Launcher” and use “Legacy Create Process Launcher” instead. This will enable “gdb/mi” and allow us to set the timeouts to connect to gdb.
  • Arguments: No changes
  • Environment: No changes
  • Debugger:
    • Debugger: gdb/mi
    • Uncheck “Stop on startup at”
    • Main:
      • GDB debugger: /home/enrique/ANDROID/gdb (IMPORTANT!)
      • GDB command file: /home/enrique/ANDROID/gdb.init (IMPORANT!)
      • GDB command set: Standard (Linux)
      • Protocol: mi2
      • Uncheck: “Verbose console”
      • Check: “Use full file path to set breakpoints”
    • Shared libs:
      • Check: Load shared lib symbols automatically
  • Source: Use the default values without modification (absolute file path, program relative file path, ChromiumAndroid (your project name)).
  • Refresh: Uncheck “Refresh resources upon completion”
  • Common: No changes.

When you have everything: apply (to save), close and reopen.

Running a debug session

Now, run gdbwrapper.sh in an independent console. When it pauses and starts waiting for ENTER, change to Eclipse, press the Debug button and wait for Eclipse to attach to the debugger. The execution will briefly pause in an ioctl() call and then continue.

To test that the debugging session is really working, set a breakpoint in content/browser/renderer_host/render_message_filter.cc, at content::RenderMessageFilter::OnMessageReceived and continue the execution. It should break there. Now, from the Debug perspective, you should be able to see the stacktrace and access to the local variables.

Welcome to the wonderful world of Android native code debugging from Eclipse! It’s a bit slow, though.

This completes the C++ side of this series of posts. In the next post, I will explain how to open the Java code of ChromeShellActivity, so that you will be able to hack on it like you would in a normal Android app project.


Hacking on Chromium for Android from Eclipse (part 1)

In the Chromium Developers website has some excellent resources on how to setup an environment to build Chromium for Linux desktop and for Android. There’s also a detailed guide on how to setup Eclipse as your development environment, enabling you to take advantage of code indexing and enjoy features such as type hierarchy, call hierarchy, macro expansion, references and a lot of tools much better than the poor man’s trick of grepping the code.

Unfortunately, there are some integration aspects not covered by those guides, so joining all the dots is not a smooth task. In this series of posts, I’m going to explain the missing parts to setup a working environment to code and debug Chromium for Android from Eclipse, both C++ and Java code. All the steps and commands from this series of posts have been tested in an Ubuntu Saucy chroot. See my previous post on how to setup a chroot if you want to know how to do this.

Get the source code

See the get-the-code guide. Don’t try to reconvert a normal Desktop build into an Android build. It just doesn’t work. The detailed steps to get the code from scratch and prepare the dependencies are the following:

 cd ANDROID # Or the directory you want
 fetch --nohooks android --nosvn=True
 cd src
 git checkout master
 gclient sync --nohooks

Configure and generate the project (see AndroidBuildInstructions), from src:

 # Make sure that ANDROID/.gclient has this line:
 # target_os = [u'android']
 # And ANDROID/chromium.gyp_env has this line:
 # { 'GYP_DEFINES': 'OS=android', }
 gclient runhooks

Build Chrome shell, from src:

 # This builds
 ninja -C out/Release chrome_shell_apk
 # This installs in the device
 # Remember the usual stuff to use a new device with adb:
 # http://developer.android.com/tools/device.html 
 # http://developer.android.com/tools/help/adb.html#Enabling
 # Ensure that you can adb shell into the device
 build/android/adb_install_apk.py --apk ChromeShell.apk --release

If you ever need to update the source code, follow this recipe and use Release or Debug at your convenience:

 git pull origin master
 gclient sync
 # ninja -C out/Release chrome_shell_apk
 ninja -C out/Debug chrome_shell_apk
 # build/android/adb_install_apk.py --apk ChromeShell.apk --release
 build/android/adb_install_apk.py --apk ChromeShell.apk --debug

As a curiosity, it’s worth to mention that adb is installed on third_party/android_tools/sdk/platform-tools/adb.

Configure Eclipse

To configure Eclipse, follow the instructions in LinuxEclipseDev. They work nice with Eclipse Kepler.

In order to open and debug the Java code properly, it’s also interesting to install the ADT plugin in Eclipse too. Don’t try to reuse the Android SDK in “third_party/android_tools/sdk”. It seems to lack some things. Download a fresh standalone SDK from the official page instead and tell the ADT plugin to use it.

In the next post, I will explain how to debug C++ code running in the device, both from the command line and from Eclipse.