crashpad/doc/developing.md

Developing Crashpad

Status

Project status information has moved to its own page.

Introduction

Crashpad is a Chromium project. Most of its development practices follow Chromium’s. In order to function on its own in other projects, Crashpad uses mini_chromium, a small, self-contained library that provides many of Chromium’s useful low-level base routines. mini_chromium’s README provides more detail.

Prerequisites

To develop Crashpad, the following tools are necessary, and must be present in the $PATH environment variable:

• Appropriate development tools.
  • On macOS, install Xcode. The latest version is generally recommended.
  • On Windows, install Visual Studio with C++ support and the Windows SDK. MSVS 2015 and MSVS 2017 are both supported. Some tests also require the CDB debugger, installed with Debugging Tools for Windows.
• Chromium’s depot_tools.
• Git. This is provided by Xcode on macOS and by depot_tools on Windows.
• Python. This is provided by the operating system on macOS, and by depot_tools on Windows.

Getting the Source Code

The main source code repository is a Git repository hosted at https://chromium.googlesource.com/crashpad/crashpad. Although it is possible to check out this repository directly with git clone, Crashpad’s dependencies are managed by gclient instead of Git submodules, so to work on Crashpad, it is best to use fetch to get the source code.

fetch and gclient are part of the depot_tools. There’s no need to install them separately.

Initial Checkout

$ mkdir ~/crashpad
$ cd ~/crashpad
$ fetch crashpad

fetch crashpad performs the initial git clone and gclient sync, establishing a fully-functional local checkout.

Subsequent Checkouts

$ cd ~/crashpad/crashpad
$ git pull -r
$ gclient sync

Building

Windows, Mac, Linux, Fuchsia

On Windows, Mac, Linux, and Fuchsia Crashpad uses GN to generate Ninja build files. For example,

$ cd ~/crashpad/crashpad
$ gn gen out/Default
$ ninja -C out/Default

You can then use gn args out/Default or edit out/Default/args.gn to configure the build, for example things like is_debug=true or target_cpu="x86".

GN and Ninja are part of the depot_tools. There’s no need to install them separately.

Fuchsia

In order to instruct gclient to download the Fuchsia SDK, you need to add the following to ~/crashpad/.gclient.

target_os=["fuchsia"]

If you're using this tree to develop for multiple targets, you can also add other entries to the the list (e.g. target_os=["fuchsia", "mac"]).

Optional Linux Configs

To pull and use Crashpad's version of clang and sysroot, make the following changes.

Add the following to ~/crashpad/.gclient.

"custom_vars": { "pull_linux_clang": True },

Add these args to out/Default/args.gn.

clang_path = "//third_party/linux/clang/linux-amd64"
target_sysroot = "//third_party/linux/sysroot"

Android

Crashpad’s Android port is in its early stages. This build relies on cross-compilation. It’s possible to develop Crashpad for Android on any platform that the Android NDK (Native Development Kit) runs on.

If it’s not already present on your system, download the NDK package for your system and expand it to a suitable location. These instructions assume that it’s been expanded to ~/android-ndk-r16.

To build Crashpad, portions of the NDK must be reassembled into a standalone toolchain. This is a repackaged subset of the NDK suitable for cross-compiling for a single Android architecture (such as arm, arm64, x86, and x86_64) targeting a specific Android API level. The standalone toolchain only needs to be built from the NDK one time for each set of options desired. To build a standalone toolchain targeting 64-bit ARM and API level 21 (Android 5.0 “Lollipop”), run:

$ cd ~
$ python android-ndk-r16/build/tools/make_standalone_toolchain.py \
      --arch=arm64 --api=21 --install-dir=android-ndk-r16_arm64_api21

Note that Chrome uses Android API level 21 for 64-bit platforms and 16 for 32-bit platforms. See Chrome’s build/config/android/config.gni which sets _android_api_level and _android64_api_level.

To configure a Crashpad build for Android using the standalone toolchain assembled above, use gyp_crashpad_android.py. This script is a wrapper for gyp_crashpad.py that sets several environment variables directing the build to the standalone toolchain, and several GYP options to identify an Android build. This must be done after any gclient sync, or instead of any gclient runhooks operation.

$ cd ~/crashpad/crashpad
$ python build/gyp_crashpad_android.py \
      --ndk ~/android-ndk-r16_arm64_api21 \
      --generator-output out/android_arm64_api21

gyp_crashpad_android.py detects the build type based on the characteristics of the standalone toolchain given in its --ndk argument.

gyp_crashpad_android.py sets the build up to use Clang by default. It’s also possible to use GCC by providing the --compiler=gcc argument to gyp_crashpad_android.py.

The Android port is incomplete, but targets known to be working include crashpad_test, crashpad_util, and their tests. This list will grow over time. To build, direct ninja to the specific out directory chosen by the --generator-output argument to gyp_crashpad_android.py.

$ ninja -C out/android_arm64_api21/out/Debug \
      crashpad_test_test crashpad_util_test

Testing

Crashpad uses Google Test as its unit-testing framework, and some tests use Google Mock as well. Its tests are currently split up into several test executables, each dedicated to testing a different component. This may change in the future. After a successful build, the test executables will be found at out/Debug/crashpad_*_test.

$ cd ~/crashpad/crashpad
$ out/Debug/crashpad_minidump_test
$ out/Debug/crashpad_util_test

A script is provided to run all of Crashpad’s tests. It accepts a single argument, a path to the directory containing the test executables.

$ cd ~/crashpad/crashpad
$ python build/run_tests.py out/Debug

To run a subset of the tests, use the --gtest_filter flag, e.g., to run all the tests for MinidumpStringWriter:

$ python build/run_tests.py out/Debug --gtest_filter MinidumpStringWriter*

Windows

On Windows, end_to_end_test.py requires the CDB debugger, installed with Debugging Tools for Windows. This can be installed either as part of the Windows Driver Kit or the Windows SDK. If the Windows SDK has already been installed (possibly with Visual Studio) but Debugging Tools for Windows is not present, it can be installed from Add or remove programs→Windows Software Development Kit.

Android

To test on Android, ADB (Android Debug Bridge) from the Android SDK must be in the PATH. Note that it is sufficient to install just the command-line tools from the Android SDK. The entire Android Studio IDE is not necessary to obtain ADB.

When asked to test an Android build directory, run_tests.py will detect a single connected Android device (including an emulator). If multiple devices are connected, one may be chosen explicitly with the ANDROID_DEVICE environment variable. run_tests.py will upload test executables and data to a temporary location on the detected or selected device, run them, and clean up after itself when done.

Fuchsia

To test on Fuchsia, you need a connected device running Fuchsia and then run:

$ gn gen out/fuchsia --args='target_os="fuchsia" target_cpu="x64" is_debug=true'
$ ninja -C out/fuchsia
$ python build/run_tests.py out/fuchsia

If you have multiple devices running, you will need to specify which device you want using their hostname, for instance:

$ export ZIRCON_NODENAME=scare-brook-skip-dried; \
  python build/run_tests.py out/fuchsia; \
  unset ZIRCON_NODENAME

Contributing

Crashpad’s contribution process is very similar to Chromium’s contribution process.

Code Review

A code review must be conducted for every change to Crashpad’s source code. Code review is conducted on Chromium’s Gerrit system, and all code reviews must be sent to an appropriate reviewer, with a Cc sent to crashpad-dev. The codereview.settings file specifies this environment to git-cl.

git-cl is part of the depot_tools. There’s no need to install it separately.

$ cd ~/crashpad/crashpad
$ git checkout -b work_branch origin/master
…do some work…
$ git add …
$ git commit
$ git cl upload

Uploading a patch to Gerrit does not automatically request a review. You must select a reviewer on the Gerrit review page after running git cl upload. This action notifies your reviewer of the code review request. If you have lost track of the review page, git cl issue will remind you of its URL. Alternatively, you can request review when uploading to Gerrit by using git cl upload --send-mail.

Git branches maintain their association with Gerrit reviews, so if you need to make changes based on review feedback, you can do so on the correct Git branch, committing your changes locally with git commit. You can then upload a new patch set with git cl upload and let your reviewer know you’ve addressed the feedback.

The most recently uploaded patch set on a review may be tested on a try server by running git cl try or by clicking the “CQ Dry Run” button in Gerrit. These set the “Commit-Queue: +1” label. This does not mean that the patch will be committed, but the try server and commit queue share infrastructure and a Gerrit label. The patch will be tested on try bots in a variety of configurations. Status information will be available on Gerrit. Try server access is available to Crashpad and Chromium committers.

Landing Changes

After code review is complete and “Code-Review: +1” has been received from all reviewers, the patch can be submitted to Crashpad’s commit queue by clicking the “Submit to CQ” button in Gerrit. This sets the “Commit-Queue: +2” label, which tests the patch on the try server before landing it. Commit queue access is available to Crashpad and Chromium committers.

Although the commit queue is recommended, if needed, project members can bypass the commit queue and land patches without testing by using the “Submit” button in Gerrit or by committing via git cl land:

$ cd ~/crashpad/crashpad
$ git checkout work_branch
$ git cl land

External Contributions

Copyright holders must complete the Individual Contributor License Agreement or Corporate Contributor License Agreement as appropriate before any submission can be accepted, and must be listed in the AUTHORS file. Contributors may be listed in the CONTRIBUTORS file.

Buildbot

The Crashpad Buildbot performs automated builds and tests of Crashpad. Before checking out or updating the Crashpad source code, and after checking in a new change, it is prudent to check the Buildbot to ensure that “the tree is green.”