[CMake] CMake + Gradle for Android
Jom O'Fisher
jomofisher at gmail.com
Mon Aug 21 18:11:38 EDT 2017
You can find that number like this:
- x = number of externalNativeBuild.cmake.path in your build.gradle files
- y = number of gradle configurations (like debug and release)
- z = number of ABIs that you build
The result is x * y * z. To be more accurate, you should consider y and z
to be functions of each build.gradle file since these can vary.
There is a second set of folders that hold the stripped versions of the .so
files that is purely managed by the android gradle plugin, so you might
consider the answer to be 2 * x * y * z.
Hope this helps.
On Mon, Aug 21, 2017 at 2:41 PM, Robert Dailey <rcdailey.lists at gmail.com>
wrote:
> This definitely a bit better, but still requires the boilerplate in
> each leaf gradle file. But I can't seriously complain too much. I
> think I'm more concerned with the implications this has underneath.
> First, let me ask just to make sure I'm not misunderstanding: Does
> each `externalNativeBuild` entry essentially mean 1 CMAKE_BINARY_DIR?
> How many binary dirs do you manage internally and what determines when
> they get created?
>
> On Mon, Aug 21, 2017 at 2:35 PM, Jom O'Fisher <jomofisher at gmail.com>
> wrote:
> > Would it work for your scenario to provide properties in the root
> > build.gradle:
> >
> > ext {
> > cmakePath = file "CMakeLists.txt"
> > }
> >
> > And then consume them in the leaf app/build.gradle like this?
> >
> > externalNativeBuild {
> > cmake {
> > path cmakePath
> > }
> > }
> >
> > It doesn't fully hide the details but it does centralize the information.
> >
> >
> > On Mon, Aug 21, 2017 at 11:20 AM, Robert Dailey <
> rcdailey.lists at gmail.com>
> > wrote:
> >>
> >> I wouldn't want to do that, it's too convoluted. I have other
> >> platforms that use these CMake scripts as well. For example, I run on
> >> Windows and Linux platforms as well to build the native code. Normal
> >> CMake behavior is designed to work at a root then go downwards to find
> >> targets. However it seems Gradle wants to start at a subdirectory and
> >> work its way up to the root, which is opposite of CMake's intended
> >> behavior IMHO. Not only that but I want to avoid special-casing
> >> behavior in CMake just for Android's use.
> >>
> >> At the moment it feels like (again referring back to my previous
> >> example structure) that both App2 and App3 each run CMake in
> >> independent binary directories instead of sharing 1 binary directory
> >> and building 2 targets inside of it. I prefer this behavior instead,
> >> especially since it allows CMake to operate as it was intended. I
> >> think it's a common case that projects will define multiple targets
> >> starting from a single root, and expect multiple APKs or java
> >> dependencies to be built within it.
> >>
> >> If I'm misunderstanding or making false assumptions please let me know.
> >>
> >>
> >>
> >> On Mon, Aug 21, 2017 at 12:00 PM, Jom O'Fisher <jomofisher at gmail.com>
> >> wrote:
> >> > Would it work for your situation for the leaf CMakeLists.txt to
> include
> >> > the
> >> > root CMakeLists.txt? Then have the leaf-specific logic in the leaf
> >> > CMakeLists.txt?
> >> >
> >> >
> >> >
> >> > On Mon, Aug 21, 2017 at 9:33 AM, Robert Dailey
> >> > <rcdailey.lists at gmail.com>
> >> > wrote:
> >> >>
> >> >> Basically, yes. We have this sort of structure:
> >> >>
> >> >> <Root of git clone>/
> >> >> Applications/
> >> >> App1/
> >> >> build.gradle
> >> >> CMakeLists.txt
> >> >> App2/
> >> >> build.gradle
> >> >> CMakeLists.txt
> >> >> App3/
> >> >> build.gradle
> >> >> CMakeLists.txt
> >> >> CommonLib/
> >> >> build.gradle
> >> >> CMakeLists.txt
> >> >> CMakeLists.txt
> >> >>
> >> >> The libs are defined as follows:
> >> >>
> >> >> * CommonLib is a static library (java code builds into a library)
> >> >> * No dependencies of its own
> >> >> * App1 is a shared library (java code builds into a library)
> >> >> * Dependencies (both java & native): CommonLib
> >> >> * App2 is a shared library (java code builds into an APK)
> >> >> * Dependencies (both java & native): App1, CommonLib
> >> >> * App3 is a shared library (java code builds into an APK)
> >> >> * Dependencies (both java & native): CommonLib
> >> >>
> >> >> In all cases, CMake must be invoked starting at the root
> >> >> CMakeLists.txt 1 time. Each target can be built from the same binary
> >> >> directory after that. Previously with ANT, I was building all native
> >> >> targets first, then moved libs to appropriate directories so that the
> >> >> 'ant' command would package the libs.
> >> >>
> >> >> For gradle, I wanted to avoid redundantly specifying the root
> >> >> directory in each leaf-level project directory. Using the example
> >> >> above, the leaf-level directories in this case would be App1, App2,
> >> >> App3, and CommonLib. However I think we only specify the native CMake
> >> >> stuff for the java targets that actually output an APK (that would be
> >> >> App2 and App3 only).
> >> >>
> >> >> The ultimate goal is to specify stuff that doesn't change per
> >> >> independent "module" of ours at the top level so it is transitive /
> >> >> inherited. Then only specify the differences (e.g. the native CMake
> >> >> target to build) in the leaf build gradle files. However you
> indicated
> >> >> this isn't possible.
> >> >>
> >> >>
> >> >>
> >> >> On Mon, Aug 21, 2017 at 11:11 AM, Jom O'Fisher <jomofisher at gmail.com
> >
> >> >> wrote:
> >> >> > What you're doing already sounds correct. You can't directly
> specify
> >> >> > CMakeLists.txt from the top-level build.gradle. Recommendation is
> >> >> > that
> >> >> > it
> >> >> > should be specified from the build.gradle of the module of the APK.
> >> >> > Is
> >> >> > the
> >> >> > issue that you have multiple APK modules that all reference the
> same
> >> >> > CMake
> >> >> > libraries?
> >> >> >
> >> >> > On Mon, Aug 21, 2017 at 9:00 AM, Robert Dailey
> >> >> > <rcdailey.lists at gmail.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> Thanks this is very helpful. The other question I have is: Is
> there
> >> >> >> a
> >> >> >> place to centrally specify the root CMakeLists.txt? Basically, I
> >> >> >> want
> >> >> >> to specify the CMake root in 1 place, and have targets (defined
> >> >> >> further down in subdirectories) that require APK packaging to
> >> >> >> specify
> >> >> >> only the native target name that should be built & packaged.
> >> >> >>
> >> >> >> At the moment we specify the root CMakeLists.txt by walking up the
> >> >> >> tree, paths like "../../../../CMakeLists.txt". I think this should
> >> >> >> be
> >> >> >> put at the top-level build gradle file if possible. Is this doable
> >> >> >> at
> >> >> >> the moment? What is the recommended setup?
> >> >> >>
> >> >> >> On Mon, Aug 21, 2017 at 9:37 AM, Jom O'Fisher <
> jomofisher at gmail.com>
> >> >> >> wrote:
> >> >> >> > Gradle does introspection on the CMake build to find .so targets
> >> >> >> > and
> >> >> >> > those
> >> >> >> > get packaged.
> >> >> >> > There is also a special case for stl/runtime .so files from the
> >> >> >> > NDK.
> >> >> >> > Any additional .so files need to specified in build.gradle using
> >> >> >> > jniDirs
> >> >> >> >
> >> >> >> > On Mon, Aug 21, 2017 at 7:30 AM, Robert Dailey
> >> >> >> > <rcdailey.lists at gmail.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> How exactly does Gradle package *.so files in an APK? I know
> that
> >> >> >> >> ANT
> >> >> >> >> used to do this for any libs under "libs/<ABI>". Does Gradle do
> >> >> >> >> some
> >> >> >> >> introspection into CMake targets to see if outputs are *.so,
> and
> >> >> >> >> copy
> >> >> >> >> those to some location if needed? What about libraries like
> >> >> >> >> libgnustl_shared.so that come with the NDK? I'd like to know if
> >> >> >> >> any
> >> >> >> >> manual copy steps are needed in CMake to put outputs in proper
> >> >> >> >> locations for the APK build step. I had to do this when using
> >> >> >> >> ANT.
> >> >> >> >>
> >> >> >> >> On Mon, Aug 7, 2017 at 6:16 PM, Jom O'Fisher
> >> >> >> >> <jomofisher at gmail.com>
> >> >> >> >> wrote:
> >> >> >> >> > 1) There is a folder created for each ABI under the project
> >> >> >> >> > module
> >> >> >> >> > folder
> >> >> >> >> > (so unique per module per ABI)
> >> >> >> >> > 2) Gradle doesn't specify language level though you can
> choose
> >> >> >> >> > to
> >> >> >> >> > specify it
> >> >> >> >> > yourself from the build.gradle. This doc does a pretty good
> job
> >> >> >> >> > of
> >> >> >> >> > explaining which variables are set by Gradle:
> >> >> >> >> > https://developer.android.com/ndk/guides/cmake.html#
> variables.
> >> >> >> >> > Philosophically, we try to set as little as we can get away
> >> >> >> >> > with.
> >> >> >> >> > In
> >> >> >> >> > particular, the section titled "Understanding the CMake build
> >> >> >> >> > command"
> >> >> >> >> > lays
> >> >> >> >> > out exactly what we set. You can also see the folders we
> >> >> >> >> > specify
> >> >> >> >> > (one
> >> >> >> >> > per
> >> >> >> >> > module per ABI)
> >> >> >> >> > 3) Not sure I understand this.
> >> >> >> >> >
> >> >> >> >> > The other document worth taking a look at (if you haven't
> >> >> >> >> > already)
> >> >> >> >> > is:
> >> >> >> >> >
> >> >> >> >> > https://developer.android.com/studio/projects/add-native-
> code.html
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > On Mon, Aug 7, 2017 at 3:35 PM, Robert Dailey
> >> >> >> >> > <rcdailey.lists at gmail.com>
> >> >> >> >> > wrote:
> >> >> >> >> >>
> >> >> >> >> >> Thanks Jom
> >> >> >> >> >>
> >> >> >> >> >> Honestly, I prefer option 1 to work simply because that's
> how
> >> >> >> >> >> Google's
> >> >> >> >> >> officially supporting CMake. But it also has debugging which
> >> >> >> >> >> is
> >> >> >> >> >> the
> >> >> >> >> >> #1
> >> >> >> >> >> reason for me.
> >> >> >> >> >>
> >> >> >> >> >> However, I'd like to understand a lot more about how the
> >> >> >> >> >> integration
> >> >> >> >> >> really happens. For example, I have these questions:
> >> >> >> >> >>
> >> >> >> >> >> 1) How, internally, are CMake build directories managed? Do
> >> >> >> >> >> you
> >> >> >> >> >> generate 1 per unique android project? What about for each
> >> >> >> >> >> specific
> >> >> >> >> >> platform (x86, armeabi-v7a, etc)?
> >> >> >> >> >> 2) Last time I looked into CMake integration, things defined
> >> >> >> >> >> inside
> >> >> >> >> >> the CMake scripts were ignored because they are specified at
> >> >> >> >> >> the
> >> >> >> >> >> command line. Namely, all of those settings that are driven
> by
> >> >> >> >> >> the
> >> >> >> >> >> Gradle configuration (CXX language level was one in
> particular
> >> >> >> >> >> I
> >> >> >> >> >> think; I specify C++14 support via CMake, but I recall this
> >> >> >> >> >> being
> >> >> >> >> >> overridden from outside)?
> >> >> >> >> >> 3) How redundant is it to configure individual libraries via
> >> >> >> >> >> the
> >> >> >> >> >> gradle scripts? In my previous attempts, I wanted to define
> >> >> >> >> >> common
> >> >> >> >> >> stuff for CMake / native code at the root gradle or settings
> >> >> >> >> >> file,
> >> >> >> >> >> and
> >> >> >> >> >> only define the differences in the actual gradle build files
> >> >> >> >> >> for
> >> >> >> >> >> each
> >> >> >> >> >> corresponding Java target (like, defining the name of the
> >> >> >> >> >> native
> >> >> >> >> >> (shared library) target in Gradle, but the command line
> >> >> >> >> >> invocation,
> >> >> >> >> >> -D
> >> >> >> >> >> CMake settings, etc would all be common and defined at the
> >> >> >> >> >> root).
> >> >> >> >> >>
> >> >> >> >> >> The TLDR is, the closer we can stay to CMake's way of doing
> >> >> >> >> >> things
> >> >> >> >> >> and
> >> >> >> >> >> keep CMake-related settings self-contained to the CMake
> >> >> >> >> >> scripts
> >> >> >> >> >> themselves, the better. This also makes cross-platform
> easier
> >> >> >> >> >> (we
> >> >> >> >> >> build the native code in Windows, for example, so having
> >> >> >> >> >> settings
> >> >> >> >> >> specified in the gradle files do not carry over to other
> >> >> >> >> >> platforms.
> >> >> >> >> >> Namely, settings that are not platform specific like the C++
> >> >> >> >> >> language
> >> >> >> >> >> level).
> >> >> >> >> >>
> >> >> >> >> >> If there's a detailed document / wiki I can read on the
> >> >> >> >> >> intrinsics
> >> >> >> >> >> of
> >> >> >> >> >> CMake integration in Gradle / Android Studio, I'd love to
> read
> >> >> >> >> >> it.
> >> >> >> >> >> Otherwise, I hope you won't mind if I pick your brain as
> >> >> >> >> >> questions
> >> >> >> >> >> come up. I think I'm going to try option 1 for now and see
> how
> >> >> >> >> >> it
> >> >> >> >> >> goes. It's just black box for me because unlike option 2, I
> >> >> >> >> >> have
> >> >> >> >> >> very
> >> >> >> >> >> little control over what happens after building the shared
> >> >> >> >> >> libraries,
> >> >> >> >> >> and to make up for that I need to really get a deep
> >> >> >> >> >> understanding
> >> >> >> >> >> of
> >> >> >> >> >> how it works so I can make sure I code my CMake scripts
> >> >> >> >> >> properly
> >> >> >> >> >> for
> >> >> >> >> >> not only Android, but my other platforms as well
> (non-Android
> >> >> >> >> >> platforms).
> >> >> >> >> >>
> >> >> >> >> >> Thanks again.
> >> >> >> >> >>
> >> >> >> >> >> On Mon, Aug 7, 2017 at 5:12 PM, Jom O'Fisher
> >> >> >> >> >> <jomofisher at gmail.com>
> >> >> >> >> >> wrote:
> >> >> >> >> >> > Either option can work fine. Disclosure: I work on Android
> >> >> >> >> >> > Studio
> >> >> >> >> >> > and
> >> >> >> >> >> > was
> >> >> >> >> >> > the one that added CMake support.
> >> >> >> >> >> >
> >> >> >> >> >> > Option (1) is the way it's designed to work and we're
> >> >> >> >> >> > working
> >> >> >> >> >> > toward
> >> >> >> >> >> > getting
> >> >> >> >> >> > rid of the need for the CMake fork. I can't really say
> when
> >> >> >> >> >> > that
> >> >> >> >> >> > will
> >> >> >> >> >> > happen
> >> >> >> >> >> > but if you can get away with an older CMake for now then
> I'd
> >> >> >> >> >> > go
> >> >> >> >> >> > this
> >> >> >> >> >> > way.
> >> >> >> >> >> > As you mentioned, option (1) will allow you to view your
> >> >> >> >> >> > source
> >> >> >> >> >> > file
> >> >> >> >> >> > structure in Android Studio, edit files, and debug using
> the
> >> >> >> >> >> > built-in
> >> >> >> >> >> > debugging support.
> >> >> >> >> >> >
> >> >> >> >> >> > To get option (2) to work, you can use jniDirs setting to
> >> >> >> >> >> > tell
> >> >> >> >> >> > Android
> >> >> >> >> >> > Gradle where to pick up your built .so files (see
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > https://stackoverflow.com/questions/21255125/how-can-i-
> add-so-files-to-an-android-library-project-using-gradle-0-7).
> >> >> >> >> >> > I'm not aware of any projects that use this approach but
> it
> >> >> >> >> >> > should
> >> >> >> >> >> > work
> >> >> >> >> >> > in
> >> >> >> >> >> > principal.
> >> >> >> >> >> >
> >> >> >> >> >> > I hope this helps,
> >> >> >> >> >> > Jomo
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > On Mon, Aug 7, 2017 at 11:09 AM, Robert Dailey
> >> >> >> >> >> > <rcdailey.lists at gmail.com>
> >> >> >> >> >> > wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> Right now I have custom targets set to execute the "ant
> >> >> >> >> >> >> release"
> >> >> >> >> >> >> command after my native targets are built. Part of that
> >> >> >> >> >> >> command
> >> >> >> >> >> >> involves copying *.so files to the libs/armeabi-v7a
> >> >> >> >> >> >> directory
> >> >> >> >> >> >> so
> >> >> >> >> >> >> they
> >> >> >> >> >> >> get packaged in an APK.
> >> >> >> >> >> >>
> >> >> >> >> >> >> When switching to gradle, I have two options:
> >> >> >> >> >> >>
> >> >> >> >> >> >> 1. Gradle drives CMake: This means using Android Studio
> and
> >> >> >> >> >> >> being
> >> >> >> >> >> >> locked down to Google's fork of CMake which is a few
> major
> >> >> >> >> >> >> releases
> >> >> >> >> >> >> behind. I see that as a negative.
> >> >> >> >> >> >>
> >> >> >> >> >> >> 2. CMake drives Gradle: This would be the same or similar
> >> >> >> >> >> >> to
> >> >> >> >> >> >> what
> >> >> >> >> >> >> I'm
> >> >> >> >> >> >> already doing: The custom targets I have would execute
> >> >> >> >> >> >> gradle
> >> >> >> >> >> >> as
> >> >> >> >> >> >> a
> >> >> >> >> >> >> separate build step, instead of running ant commands. I'm
> >> >> >> >> >> >> not
> >> >> >> >> >> >> too
> >> >> >> >> >> >> familiar with Gradle, so I'm not sure how you tell it
> where
> >> >> >> >> >> >> your
> >> >> >> >> >> >> shared libraries are for the APK packaging steps.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Which does everyone recommend? Is anyone using one of
> these
> >> >> >> >> >> >> setups
> >> >> >> >> >> >> successfully? The downside to option 2 is probably no
> >> >> >> >> >> >> on-device
> >> >> >> >> >> >> native
> >> >> >> >> >> >> debugging since Android Studio probably can't handle
> gradle
> >> >> >> >> >> >> projects
> >> >> >> >> >> >> without any external CMake builds set up.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Would like some general direction & advice before I move
> >> >> >> >> >> >> away
> >> >> >> >> >> >> from
> >> >> >> >> >> >> ANT. Thanks in advance.
> >> >> >> >> >> >> --
> >> >> >> >> >> >>
> >> >> >> >> >> >> Powered by www.kitware.com
> >> >> >> >> >> >>
> >> >> >> >> >> >> Please keep messages on-topic and check the CMake FAQ at:
> >> >> >> >> >> >> http://www.cmake.org/Wiki/CMake_FAQ
> >> >> >> >> >> >>
> >> >> >> >> >> >> Kitware offers various services to support the CMake
> >> >> >> >> >> >> community.
> >> >> >> >> >> >> For
> >> >> >> >> >> >> more
> >> >> >> >> >> >> information on each offering, please visit:
> >> >> >> >> >> >>
> >> >> >> >> >> >> CMake Support: http://cmake.org/cmake/help/support.html
> >> >> >> >> >> >> CMake Consulting:
> >> >> >> >> >> >> http://cmake.org/cmake/help/consulting.html
> >> >> >> >> >> >> CMake Training Courses:
> >> >> >> >> >> >> http://cmake.org/cmake/help/training.html
> >> >> >> >> >> >>
> >> >> >> >> >> >> Visit other Kitware open-source projects at
> >> >> >> >> >> >> http://www.kitware.com/opensource/opensource.html
> >> >> >> >> >> >>
> >> >> >> >> >> >> Follow this link to subscribe/unsubscribe:
> >> >> >> >> >> >> http://public.kitware.com/mailman/listinfo/cmake
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >
> >> >> >> >
> >> >> >
> >> >> >
> >> >
> >> >
> >
> >
>
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