Note: If there‘s anything you want to see done in the NDK, file a bug! Nothing here is set in stone, and if there’s something that we haven‘t thought of that would be of more use, we’d be happy to adjust our plans for that.
Disclaimer: Everything here is subject to change. The further the plans are in the future, the less stable they will be. Things in the upcoming release are fairly certain, and the second release is quite likely. Beyond that, anything written here is what we would like to accomplish in that release assuming things have gone according to plan until then.
Note: For release timing, see our release schedule on our wiki.
Estimated release: Q4 2018
Now that the NDK is down to a single compiler and STL, if we just taught the Clang driver to emit -D__ANDROID_API__=foo and to link libc.so.18 instead of libc.so, standalone toolchains would be obsolete because the compiler would already be a standalone toolchain. The NDK toolchain would Just Work regardless of build system, and the logic contained in each build system could be greatly reduced.
Related to this (but maybe occurring in a later release), we'll want to switch from libgcc to libcompiler-rt and our own unwinder.
See the corresponding bug make all toolchains standalone toolchains for detailed discussion of the implementation and sub-tasks.
See the r19 hotlist.
Estimated release: Q1 2019
r19 covers the bulk of the work, but there are still a handful of flags required for building Android that should be lifted into the Clang driver. See Issue 812 for more information.
NDK r18 made lld available, r19 encourages its use, and r20 will make it the default assuming there are no unresolved issues turned up in r19.
See the r20 hotlist.
Estimated release: Q2 2019
If r20 was able to switch the default to lld and no major unresolved issues remained, we should remove gold and bfd.
See the r21 hotlist.
The following projects are listed in order of their current priority.
Note that some of these projects do not actually affect the contents of the NDK package. The samples, cdep, documentation, etc are all NDK work but are separate from the NDK package. As such they will not appear in any specific release, but are noted here to show where the team's time is being spent.
There are many other commonly-used libraries (such as Curl and BoringSSL) that are currently difficult to build/package, let alone keep updated. We should offer (a) a tool to build open source projects, (b) a repository of prebuilts, (c) a command-line tool to add prebuilts to an ndk-build/cmake project, and (d) Studio integration to add prebuilts via a GUI.
We currently have cdep, but it doesn't have a very large corpus and could use some build system integration polish. If not cdep, adding support for exposing native libraries from AARs would be an alternative.
We don't currently build, test, or ship libc++‘s std::filesystem. Until recently this API wasn’t final, but now is at least a stable API (though it sounds like the ABI will change in the near future).
There‘s a fair amount of work involved in getting these tests running, but that’s something we should do.
CMake added their own NDK support about the same time we added our toolchain file. The two often conflict with each other, and a toolchain file is a messy way to implement this support. However, fully switching to the integrated support puts NDK policy decisions (default options, NDK layout, etc) fully into the hands of CMake, which makes them impossible to update without the user also updating their CMake version.
We will reorganize our toolchain file to match the typical implementation of a CMake platform integration (like $CMAKE/Modules/Platform/Android-*.cmake) and CMake will be modified to load the implementation from the NDK rather than its own.
See Issue 463 for discussion.
iOS developers are used to using weak symbols to refer to function that may be present in their equivalent of targetSdkVersion but not in their minSdkVersion. They use a run-time null check to decide whether the new function is available or not. Apparently clang also has some support for emitting a warning if you dereference one of these symbols without a corresponding null check.
This seems like a more convenient option than is currently available on Android, especially since no currently shipping version of Android includes a function to check which version of Android you're running on.
We might not want to make this the default (because it's such a break with historical practice, and might be surprising), but we should offer this as an option.
An interesting technical problem here will be dealing with the DT_NEEDED situation for “I need this library (but it might not exist yet)”.
By Q2 2019 Clang may have a complete enough implementation of the modules TS and Android may have a Clang with those changes available.
At least for the current spec (which is in the process of merging with the Clang implementation, so could change), the NDK will need to:
The following projects are things we intend to do, but have not yet been sheduled into the sections above.
We should probably add basic doc comments to the bionic headers:
char* point to? Who owns it? Are errors -1 (as for most functions) or <errno.h> values (for pthread_mutex_lock)?Should these be in the NDK API reference too? If so, how will we keep them from swamping the “real” NDK API?
vim is ready, Android Studio now supports doxygen comments (but seems to have gained a new man page viewer that takes precedence), and Visual Studio Code has nothing but feature requests.
The samples are low-quality and don't necessarily cover interesting/difficult topics.
The NDK has long included gtest and clang supports various sanitiziers, but there are things we can do to improve the state of testing/code quality:
gmock.We should make lldb available in the NDK. It's currently shipped as part of Studio. Medium-term we should have Studio ship our lldb. Long-term Studio should probably use the NDK lldb directly.
NDK APIs are C-only for ABI stability reasons. We should offer header-only C++ wrappers for NDK APIs, even if only to offer the benefits of RAII. Examples include Bitmap, ATrace, and ASharedMemory.
Complaints about basic JNI handling are common. We should make libnativehelper or something similar available to developers.
For serious i18n, icu4c is too big too bundle, and non-trivial to use the platform. We have a C API wrapper prototype, but we need to make it easily available for NDK users.
We still need to update libc++ twice: once for the platform, and once for the NDK. We also still have two separate test runners.
Full history is available, but this section summarizes major changes in recent releases.
Removed GCC and gnustl/stlport. Added lld.
Added compile_commands.json for better tooling support.
Defaulted to libc++.
Removed ARMv5 (armeabi), MIPS, and MIPS64.
Fixed libandroid_support, libc++ now the recommended STL (but still not the default).
Removed non-unified headers.
Defaulted to unified headers (opt-out).
Removed support for API levels lower than 14 (Android 4.0).
Added unified headers (opt-in).
Added simpleperf.
Removed armeabi-v7a-hard.
Removed support for API levels lower than 9 (Android 2.3).