Chrome on Android has java and c/c++ code. Each “side” have its own set of tools for debugging. Here's some tips.
You can run the app by using one of the wrappers.
# Installs, launches, and enters logcat. out/Default/bin/content_shell_apk run --args='--disable-fre' 'data:text/html;utf-8,<html>Hello World!</html>' # Launches without first installing. Does not show logcat. out/Default/bin/chrome_public_apk launch --args='--disable-fre' 'data:text/html;utf-8,<html>Hello World!</html>'
Chromium logging from LOG(INFO) etc., is directed to the Android logcat logging facility. You can filter the messages, e.g. view chromium verbose logging, everything else at warning level with:
# Shows a coloured & filtered logcat. out/Default/bin/chrome_public_apk logcat [-v] # Use -v to show logs for other processes
Do not use fprintf or printf debugging! This does not redirect to logcat.
Redirecting stdio to logcat, as documented here, has a bad side-effect that it breaks adb_install.py. See here for details.
build/android/screenshot.py /tmp/screenshot.png
Generate an Android Studio project, and then use Layout Inspector.
For both apk and test targets, pass --wait-for-java-debugger to the wrapper scripts.
Examples:
# Install, launch, and wait: out/Default/bin/chrome_public_apk run --wait-for-java-debugger # Launch, and have GPU process wait rather than Browser process: out/Default/bin/chrome_public_apk launch --wait-for-java-debugger --debug-process-name privileged_process0 # Have Renderers wait: out/Default/bin/chrome_public_apk launch --args="--renderer-wait-for-java-debugger" # Have tests wait: out/Default/bin/run_chrome_public_test_apk --wait-for-java-debugger out/Default/bin/run_chrome_junit_tests --wait-for-java-debugger # Specify custom port via --debug-socket=9999
In Eclipse, make a debug configuration of type “Remote Java Application”. Choose a “Name” and set “Port” to 8700.
Make sure Eclipse Preferences > Run/Debug > Launching > “Build (if required) before launching” is unchecked.
Run Android Device Monitor:
third_party/android_sdk/public/tools/monitor
Now select the process you want to debug in Device Monitor (the port column should now mention 8700 or xxxx/8700).
Run your debug configuration, and switch to the Debug perspective.
While the app is running, use the wrapper script's gdb command to enter into a gdb shell.
When running with gdb attached, the app runs extremely slowly.
# Attaches to browser process. out/Default/bin/content_shell_apk gdb out/Default/bin/chrome_public_apk gdb # Attaches to gpu process. out/Default/bin/chrome_public_apk gdb --debug-process-name privileged_process0 # Attach to other processes ("chrome_public_apk ps" to show pids). out/Default/bin/chrome_public_apk gdb --pid $PID
When connecting, gdb will complain of not being able to load a lot of libraries. This happens because of java code. The following messages are all expected:
Connecting to :5039... warning: Could not load shared library symbols for 211 libraries, e.g. /system/framework/arm/boot.oat. Use the "info sharedlibrary" command to see the complete listing. Do you need "set solib-search-path" or "set sysroot"? Failed to read a valid object file image from memory.
While the app is running, run the gdb command with --ide:
out/Default/bin/content_shell_apk gdb --ide
Once the script has done its thing (generally ~1 second after the initial time its used), open vscode.md and ensure you have the Android launch entry.
Connect via the IDE's launch entry. Connecting takes 30-40 seconds.
When troubleshooting, it's helpful to enable engine logging.
Known Issues:
# Install, launch, and wait: out/Default/bin/chrome_public_apk run --args="--wait-for-debugger" # Launch, and have GPU process wait rather than Browser process: out/Default/bin/chrome_public_apk launch --args="--wait-for-debugger-children=gpu-process" # Or for renderers: out/Default/bin/chrome_public_apk launch --args="--wait-for-debugger-children=renderer"
Once gdb attaches, the app will resume execution, so you must set your breakpoint before attaching.
Once attached, gdb will drop into a prompt. Set your breakpoints and run “c” to continue.
If a crash has generated a tombstone in your device, use:
build/android/tombstones.py --output-directory out/Default
If you have a stack trace (from adb logcat) that needs to be symbolized, copy it into a text file and symbolize with the following command (run from ${CHROME_SRC}):
third_party/android_platform/development/scripts/stack --output-directory out/Default [tombstone file | dump file]
stack can also take its input from stdin:
adb logcat -d | third_party/android_platform/development/scripts/stack --output-directory out/Default
Example:
third_party/android_platform/development/scripts/stack --output-directory out/Default ~/crashlogs/tombstone_07-build231.txt
You will need the ProGuard mapping file that was generated when the application that crashed was built. When building locally, these are found in:
out/Default/apks/ChromePublic.apk.mapping out/Default/apks/ChromeModernPublic.apk.mapping etc.
Build the java_deobfuscate tool:
ninja -C out/Default java_deobfuscate
Then run it via:
# For a file: out/Default/bin/java_deobfuscate PROGUARD_MAPPING_FILE.mapping < FILE # For logcat: adb logcat | out/Default/bin/java_deobfuscate PROGUARD_MAPPING_FILE.mapping
In your build environment:
adb root adb shell stop adb shell setprop log.redirect-stdio true adb shell start
In the source itself, use fprintf(stderr, "message"); whenever you need to output a message.
To run unit tests use the following command:
out/Debug/bin/run_test_name -f <test_filter_if_any> --wait-for-debugger -t 6000
That command will cause the test process to wait until a debugger is attached.
To attach a debugger:
build/android/adb_gdb --output-directory=out/Default --package-name=org.chromium.native_test
After attaching gdb to the process you can use it normally. For example:
(gdb) break main Breakpoint 1 at 0x9750793c: main. (2 locations) (gdb) continue