17 Oct 2019

feedAndroid Developers Blog

Introducing NDK r21: our first Long Term Support release

Posted by Dan Albert, Android NDK Tech Lead

Android NDK r21 is now in beta! It's been a longer than usual development cycle (four months since NDK r20), so there's quite a lot to discuss for this release.

We have the usual toolchain updates, improved defaults for better security and performance, and are making changes to our release process to better accommodate users that need stability without hindering those that want new features.

New Minimum System Requirements

This release comes with new minimum system requirements. Following Android Studio and the SDK, 32-bit Windows is no longer supported. While this change will not affect most developers, this change does have an impact if you use 32-bit versions of Microsoft® Windows®. Linux users must have glibc 2.17 or newer.

Release Cycle Changes and LTS

One release a year will be our Long Term Support (LTS) release for users that want stability more than they need new features. The release will undergo a longer beta cycle before being released, and will receive bug fixes as backports until next year's LTS release. Generally releasing in Q4, our first LTS release will be NDK r21.

The non-LTS releases each year, which we call the "rolling" release, will be similar to our current process. These will be approximately quarterly releases of our latest set of features, which will only be patched later for critical toolchain fixes. If you want the latest features from Clang and libc++, this is the release for you.

More detail, including the criteria we will use to determine what will be backported, what kinds of bugs will trigger a point release, and the bar we hold each release to can be found documented on our GitHub Wiki.

New Features and Updates

There are quite a lot of new things in this release, resolving bugs and helping you write better, safer code.

We've updated GNU Make to version 4.2, which enables --output-sync to avoid interleaving output with error messages. This is enabled by default with ndk-build. This also includes a number of bug fixes, including fixing the pesky CreateProcess errors on Windows.

GDB has been updated to version 8.3, which includes fixes for debugging modern Intel CPUs.

Updated LLVM

As always, we've updated LLVM and all of its components (Clang, lld, libc++, etc) which includes many improvements.

The toolchain has been updated to r365631 (the master branch as of 10 July 2019). This includes fixes for quite a few bugs in the previous release, perhaps most importantly LLD no longer hangs when using multithreaded linking on Windows. OpenMP is now available as a dynamic library (and this is the new default behavior, so link with -static-openmp if you want to stick with the static runtime).

A handful of driver improvements have been made to reduce the amount of compiler configuration required by each build system as well. Build system owners should check the updated Build System Maintainers guide.

libc++ has been updated to r369764.


Fortify is now enabled by default when using ndk-build or the CMake toolchain file (this includes ExternalNativeBuild users). Fortify enables additional checks in the standard library that can help catch bugs sooner and mitigate security issues. For example, without fortify the following code compiles fine:

    const char src[] = "this string is too long";
    char dst[10];
    strcpy(dst, src);

With fortify, the buffer overflow is diagnosed at compile-time:

    test.cpp:10:18: error: 'strcpy' called with string bigger than buffer
      strcpy(dst, src);

It is not always possible for the compiler to detect this issue at compile-time. In those cases, a run-time check will be used instead that will cause the program to abort rather than continue unsafely.

If you're using a build system other than ndk-build or CMake via the NDK's toolchain file, this will not be enabled by default. To enable, simply define _FORTIFY_SOURCE=2. The most reliable way to do this is by adding -D_FORTIFY_SOURCE=2 to your compiler flags.

Clang can also statically detect some of these issues by using -Wfortify-source (also new in r21). This is on by default, but it's recommended to enforce fixing issues with -Werror=fortify-source. Use this in addition to the C library features, not instead of, since the warnings do not cover the same cases as the C library extension, nor can it add run-time checks.

Note that because run-time support is required for fortify and the feature was gradually added to Android over time, the exact set of APIs protected by fortify depends on your minSdkVersion. Fortify is an improvement, but it is not a replacement for good tests, ASan, and writing safe code.

See FORTIFY in Android for an in-depth explanation of fortify.

Other updates

64-bit requirement

Since August 2019, all existing and new apps are now required to support 64-bit before they can be released to Google Play; there's an extension for a limited set of apps. For more information and help on adding support for 64-bit, see our guide.

Neon by default

Arm code is now built with Neon by default. In a previous release we enabled it conditionally based on minSdkVersion, but given the very small number of devices that don't support Neon we now enable it unconditionally. This offers improved performance on all 32-bit Arm devices (64-bit Arm always had this, and it does not affect Intel ABIs).

As before, this behavior can be disabled for apps that need to continue supporting devices without Neon. Alternatively, those devices can be blacklisted in the Play Console. See https://developer.android.com/ndk/guides/cpu-arm-neon for more information.

Up Next

Have a look at our roadmap to see what we're working on next. The next few big things coming up are package management and better CMake integration.

17 Oct 2019 5:25pm GMT

09 Oct 2019

feedAndroid Developers Blog

Previewing #AndroidDevSummit: Sessions, App, & Livestream Details

Posted by The #AndroidDevSummit team

In two weeks, we'll be welcoming Android developers from around the world at Android Dev Summit 2019, broadcasting live from the Google Events Center (MP7) in Sunnyvale, CA on October 23 & 24. Whether you're joining us in person or via the livestream, we've got a great show planned for you; starting today, you can read more details about the keynote, sessions, codelabs, sandbox, the mobile app, and how online viewers can participate.

The keynote, sessions, sandbox and more, kicking off at 10AM PDT

The summit kicks off on October 23 at 10 a.m. PDT with a keynote, where you'll hear from Dave Burke, VP Engineering for Android, and others on the present and future of Android development. From there, we'll dive into two days of deep technical content from the Android engineering team, on topics such as Android platform, Android Studio, Android Jetpack, Kotlin, Google Play, and more.

The full agenda is now available, so you can start to plan your summit experience. We'll also have demos in the sandbox, hands-on learning with codelabs, plus exclusive content for those watching on the livestream.

Get the Android Dev Summit app on Google Play!

The official app for Android Dev Summit 2019 has started rolling out on Google Play. With the app, you can explore the agenda by searching through topics and speakers. Plan your summit experience by saving events to your personalized schedule. You'll be able to watch the livestream and find recordings after sessions occur, and more. (By the way, the app is also an Instant app, so with one tap you can try it out first before installing!)

2019 #AndroidDevSummit app

A front-row seat from your desk, and #AskAndroid your pressing questions!

We'll be broadcasting live on YouTube and Twitter starting October 23 at 10 a.m. PDT. In addition to a front row seat to over 25 Android sessions, there will be exclusive online-only content and an opportunity to have your most pressing Android development questions answered live, broadcast right from the event.

Tweet us your best questions using the hashtag #AskAndroid in the lead-up to the Android Dev Summit. We've gathered experts from Jetpack to Kotlin to Android 10, so we've got you covered. We'll be answering your questions live between sessions on the livestream. Plus, we will share updates directly from the Google Events Center to our social channels, so be sure to follow along!

09 Oct 2019 10:45pm GMT

02 Oct 2019

feedAndroid Developers Blog

Continuous testing with new Android emulator tools

Posted by Lingfeng Yang, Android Studio team

Developers often use the Android Emulator during their day-to-day development to quickly test the latest changes before they are being committed. In addition, developers are increasingly using the emulator in their continuous integration (CI) systems to run a larger suite of automated tests. To better support this use-case, we are open sourcing the Android Emulator Container Scripts and improving the developer experiences around two pain points:

  1. Deployability - finding and running the desired version of Android Emulator.
  2. Debuggability - tracking down bugs from remote instances of Android Emulator.


Android supports a wide variety of hardware and software configurations, and the Android Emulator is no different. However, this wide variety can create confusion over environment configurations. How should developers obtain emulators and system images? What drivers are required? How do you run with or without CPU or GPU acceleration? (etc. etc.)

To address this we have launched:

To increase reproducibility, the underlying Dockerfile template makes the required command line flags and system dependencies more explicit (and reproducible via building Docker images from them). For hardware acceleration, note the --privileged flag that is passed to run.sh; we assume CPU acceleration is available when running the emulator, and --privileged is needed to run the containers with CPU acceleration (KVM) enabled.

For more details on how to create and deploy the Android Emulator image, go to the README.


When the emulator is running and a test or the emulator fails, it can be difficult to dive into the running environment and diagnose the error. Often, diagnosis requires direct interaction with the virtual device. We provide two mechanisms for direct interaction:

  1. ADB
  2. Remote streaming

In the case of ADB, we allow all commands, such as logcat and shell, by forwarding a particular port from the Docker guest to the host. Because the current port is 5555, we'll need to collect more feedback and do more research on how best to separate ports across different containers.

Remote streaming

Security note: With remote streaming, keep in mind that once the service is started, anyone who can connect to your computer on port 80/443 can interact with the emulator. So be careful with running this on a public server!

With remote streaming, you can run the emulator in a container, which is as interactive as running locally. Running the emulator in a container makes it easier to debug issues that can be hard to discover using ADB commands. You can access the emulator using a browser with WebRTC, which is used to stream the video, and gRPC, which is used to send mouse and keyboard events to the emulator. Remote streaming requires three containers:

  1. A container that hosts the latest emulator
  2. A container with an Envoy web proxy needed for gRPC
  3. A container with nginx to serve the React web app

You can compose the Docker containers together using docker-compose, as described in the README. The containers bind to port 80 and 443, so make sure you do not have a web server running. A self-signed certificate will be offered if you point the browser to the host. If you point your browser to the host you should see something like the image below:

Again, keep in mind that anyone who can connect to your host can interact with the emulator. So be careful with running this on a public server!

Let's scale testing!

Testing can seem to be a tax on development time. However, as many seasoned developers have seen, proper automated testing can increase development velocity as the code base becomes bigger and more complex. Continuous testing should give you confidence that the change you make won't break your app.

02 Oct 2019 9:14pm GMT