[CMake] [cmake-developers] CMake integration in Gradle (Android Studio)

[Robert Dailey]

Florent, I had the same thoughts. It seems that the CMake generate +
build step happen silently as a prerequisite step when doing the
'gradle build' command somewhere. It makes it appear as if CMake is
not running at all, but instead the Java piece of the build is just
taking forever.

Really I want to get away from ant / eclipse, but unlike Android
Studio, at least in Eclipse I can view C++ code and edit it. I don't
know of any other IDE I can use to edit both java & android code. My
last shining hope is perhaps Visual Studio 2015 and their Android
support. They have a fork of the CMake repository with some changes
for generating Android IDE projects for VS, I have not tried it
though.

What a giant mess this has become... I have no idea what direction to
go on this. Advice on tooling combinations you guys are using would be
very helpful though.

On Mon, Oct 31, 2016 at 5:04 PM, Florent Castelli
<florent.castelli at gmail.com> wrote:
> I tried the Gradle + CMake integration and I'm not really impressed.
> I would recommend not using it right now until they fix the rough edges.
>
> The prime concern is that it is REALLY hard to get the CMake output and
> compilation output,
> even within Android Studio. If you compile from command line, you won't see
> much.
> This is a no go for CI environments where you need to see what went wrong
> and also some
> output once in a while (or builds are usually considered stuck and canceled
> if they take too long).
> See the issue: https://code.google.com/p/android/issues/detail?id=210930
>
> Installing CMake within the SDK is not trivial. There's an open bug with a
> proposed solution,
> it's not pretty stuff but does the work:
> https://code.google.com/p/android/issues/detail?id=221907
> An alternative would be to repackage your SDK folder after running Android
> Studio and installing
> everything you need and distribute that to your CI build machines /
> developer machines.
>
> But essentially, what you want is probably just use their toolchain file,
> which is much better
> than the OpenCV one. You can find it bundled in the latest NDK and I guess
> you could be using
> that directly with CMake. If it is doing weird things, I guess you could
> have a look at it and debug it.
> It's not as complicated as the OpenCV one and I hope you'll find the
> solution to your issues!
>
> As for CMake 3.7, when I asked about it in this mailing list, someone said
> there will be
> a compatibility layer to the toolchain to reuse the upstream support when
> it's available
> if I remember correctly.
>
> /Florent
>
>
> On 25/10/2016 15:48, Robert Dailey wrote:
>>
>> I'm not sure if the CMake mailing lists are the right place to ask
>> this question but I thought I'd ask just in case someone has gone down
>> this path or has experience with what Google/Gradle is actually trying
>> to accomplish with what seems to be a hand-built version of CMake with
>> custom patches that are not in upstream repositories.
>>
>> Prior to switching to Android Studio / Gradle, I was using Eclipse /
>> Ant. The way I did CMake integration was not really integration at
>> all: I generated Ninja build scripts using CMake and implemented
>> custom targets to run "ant release" after all the C++ projects were
>> built. I made sure that CMake copied relevant *.so files to
>> appropriate directories in the Ant structure so they are packaged with
>> built APKs. That's how I did my Android development.
>>
>> Now that I'm integrating CMake into Gradle, first annoyance I noticed
>> is that I can't use CMake 3.7 (or any external installation of CMake)
>> with Android Studio. It requires a version of CMake installed through
>> SDK Manager. This means I can't use the new Android toolchain
>> functionality built into CMake 3.7 (sad face). But this is something I
>> can work around...
>>
>> Next I found out that stuff I'm setting in my CMake scripts, such as
>> CPP flags like `-std=c++14` and `-fexceptions` was not being applied.
>> For whatever reason, Gradle is overriding these from the command line
>> (I'm guessing?). So this requires me to duplicate the toolchain /
>> compiler flag setup I already do in my CMake scripts now in the Gradle
>> build scripts. This seems completely unnecessary and a maintenance
>> burden.
>>
>> What I was expecting Gradle to do was essentially provide me some
>> toolchain file so that CMake can find the compiler and linker to use
>> and then the rest would be determined by CMake itself.
>>
>> Is there a way I can tell Gradle to not take so much control over
>> compiler flags? I want my CMake scripts to do this. I can't imagine
>> they had a good reason to do this. What have others done in this
>> situation with their own Gradle + CMake integration? Looking for
>> advice here, since information is sparse, especially since the Android
>> Studio 2.2 CMake integration is relatively new stuff.
>
>
>