[CMake] CMake + Gradle for Android

Robert Dailey rcdailey.lists at gmail.com
Fri Aug 25 17:42:33 EDT 2017 

By the way when I try to use "targets", I get a failure. Basically
Gradle doesn't recognize that keyword. I tried singular form as well
("target"), no luck.

I'm running canary build of everything possible. What am I missing?

On Wed, Aug 23, 2017 at 4:20 PM, Jom O'Fisher <jomofisher at gmail.com> wrote:
> By gradle module projects, I just mean the leaf build.gradle files as
> opposed to the root build.gradle. By configurations, I mean Build Types
> (debug vs release) and Product Flavors (demo vs free vs paid). Hereafter I
> will use the term "variant" rather than "configuration" to be precise. See
> this write-up on build variants:
>
> https://developer.android.com/studio/build/build-variants.html#build-types
>
> This build matrix is constructed at the leaf build.gradle level. Native
> build in gradle allows you to set C/C++ flags individually for each variant
> so that you can define compiler flags (for example, -DFREE_VERSION).
>
> One thing to notice at this stage is that the same CMake target may be built
> with different compiler flags across different projects, build types, and
> product flavors. So in the general case, build outputs won't be the same.
>
> You asked which targets build when specifying path. By default, we build all
> targets that produce an .so. You can override this by setting
> externalNativeBuild.cmake.targets. For example,
>
>     paid {
>       ...
>       externalNativeBuild {
>         cmake {
>           ...
>           targets "native-lib-paid"
>         }
>       }
>     }
>
> As for your last question, the model we generally see used is that the main
> CMakeLists.txt is next to the leaf build.gradle such that this
> CMakeLists.txt doesn't couple with peer APK project CMakeLists.txt (though
> they may share common dependencies and settings). Otherwise, multiple APK
> projects would perform pretty much similar to yours--they would build
> targets per-leaf project and not share build outputs. As far as I can see
> your organization is just as valid so long as you only build the targets you
> need.
>
> Regarding native dependencies between java projects. We generally try to
> avoid making the CMake build depend on the gradle build (you should be able
> to replicate the CMake build from the command-line if you set the right
> flags). At the moment I don't see a way we could make things better without
> violating that tenet but that could be lack of imagination on my part.
>
> We'll definitely be discussing this use case at our next C++ meeting and
> I'll also be checking for myself whether ccache will work in this CMake
> scenario. If ccache does work it seems like the natural level at which to
> fold identical builds.
>
>
>
> On Wed, Aug 23, 2017 at 1:03 PM, Robert Dailey <rcdailey.lists at gmail.com>
> wrote:
>>
>> I'm not sure what you mean by "gradle module projects", but maybe
>> having some examples of what you mean by "configurations, C++ flags,
>> etc" might make it more clear.
>>
>> Question: When specifying "path" for the CMakeLists.txt in the
>> build.gradle file, how do you know which targets to build? For
>> example, that run of CMake may generate 100 targets, but only 20 need
>> to build and be packaged (*.so files) with the APK. Do you just build
>> "all"? Is there a way to specify the target itself?
>>
>> Thanks again. I'd still like to know more about what the ideal
>> organization is. I find it hard to believe that large android projects
>> rarely break things up into multiple, separate "components" that are
>> built independently. That's really the gist of what we're dealing with
>> here. Your typical "hello world" project likely will have only 1
>> CMakeLists.txt that is pretty self-contained, but all the
>> documentation I've looked at so far doesn't show the best way to
>> handle native library dependencies across java projects between
>> build.gradle files (or maybe I'm just not looking hard enough).
>>
>> On Wed, Aug 23, 2017 at 1:02 PM, Jom O'Fisher <jomofisher at gmail.com>
>> wrote:
>> > Thanks for the write-up Robert. Having thought about it, I don't believe
>> > we
>> > have a satisfying answer at the gradle level for this kind of
>> > organization.
>> > In the gradle model module projects are the unit of organization for
>> > configurations, C/C++ flags, etc. and that's something we're pretty much
>> > stuck with.
>> > Regarding just the redundant build issue, would something like ccache
>> > help?
>> > I know people have used it with ndk-build with success, I'm not sure
>> > about
>> > CMake but I don't see why that should make a difference.
>> >
>> >
>> >
>> > On Tue, Aug 22, 2017 at 10:27 AM, Robert Dailey
>> > <rcdailey.lists at gmail.com>
>> > wrote:
>> >>
>> >> Another reason to reduce the number of binary directories is that
>> >> there are different ways of managing third party libraries. One in
>> >> particular that we use is to clone a repository into the binary
>> >> directory and build all third party libs in real time based on a
>> >> toolchain file (Similar to the functionality provided by
>> >> ExternalProject module in CMake). This is repeated from scratch only
>> >> if the work hasn't already been done in the binary directory before.
>> >> By having more binary dirs than needed, this work is being done an
>> >> exponential amount of times which can result in a lot of wasted time
>> >> waiting. There are 1 time operations that multiple targets can benefit
>> >> from in a single binary tree, instead of 1 per unique target being
>> >> invoked.
>> >>
>> >> Sorry to keep responding: I'm just thinking of things as I go and
>> >> bringing them up, to shed light on some of the reasoning behind my
>> >> suggestions.
>> >>
>> >> On Tue, Aug 22, 2017 at 9:26 AM, Robert Dailey
>> >> <rcdailey.lists at gmail.com>
>> >> wrote:
>> >> > Sorry I forgot to answer your last set of questions:
>> >> >
>> >> > CommonLib is indeed 2 things:
>> >> >
>> >> > * A common (static or shared) library for native code (most of our
>> >> > CMake targets specify CommonLib as a link dependency)
>> >> > * A common library for Java code (we do specify this as a dependency
>> >> > for most java targets in Gradle, specifically those under
>> >> > Applications/)
>> >> >
>> >> > On Mon, Aug 21, 2017 at 6:20 PM, Raymond Chiu <chiur at google.com>
>> >> > wrote:
>> >> >> Hi Robert,
>> >> >>
>> >> >> I work with Jom on the Android Studio team, and I would like to
>> >> >> clarify
>> >> >> a
>> >> >> few things to better understand your situation.
>> >> >> You mentioned the project is intend to be cross platform.  Normally,
>> >> >> in
>> >> >> such
>> >> >> situation, we expect there to be a single CMake root project to be
>> >> >> imported
>> >> >> into one of the Android library/application.  However, in your case,
>> >> >> there
>> >> >> are subprojects with Java code.
>> >> >>
>> >> >> Are the CMake code in App1/2/3 intended to be cross platform too?
>> >> >> Or
>> >> >> are
>> >> >> they Android specific code?  If they are meant to be cross platform,
>> >> >> how
>> >> >> does the Java code works on other platforms?  Or perhaps you added
>> >> >> Java
>> >> >> binding in those subprojects just for Android?
>> >> >>
>> >> >> The build.gradle in CommonLib, what kind of Gradle project is that?
>> >> >> From
>> >> >> your description, it doesn't look like an Android library project.
>> >> >> Or
>> >> >> am I
>> >> >> mistaken and it also applies the android library plugin?
>> >> >>
>> >> >> Raymond
>> >> >>
>> >> >> On Mon, Aug 21, 2017 at 3:34 PM, Jom O'Fisher <jomofisher at gmail.com>
>> >> >> wrote:
>> >> >>>
>> >> >>> + a colleague
>> >> >>>
>> >> >>> On Mon, Aug 21, 2017 at 3:11 PM, Jom O'Fisher
>> >> >>> <jomofisher at gmail.com>
>> >> >>> wrote:
>> >> >>>>
>> >> >>>> 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
>> >> >>>>> >> >> >> >> >> >
>> >> >>>>> >> >> >> >> >> >
>> >> >>>>> >> >> >> >> >
>> >> >>>>> >> >> >> >> >
>> >> >>>>> >> >> >> >
>> >> >>>>> >> >> >> >
>> >> >>>>> >> >> >
>> >> >>>>> >> >> >
>> >> >>>>> >> >
>> >> >>>>> >> >
>> >> >>>>> >
>> >> >>>>> >
>> >> >>>>
>> >> >>>>
>> >> >>>
>> >> >>
>> >
>> >
>
>

More information about the CMake mailing list