Android / Java build fails on CentOS 7

[stephan57160]

Was trying to setup something to use BUILD_PREFIX and have zyre/czmq/libzmq dependencies installed somewhere else than under
/usr/local/lib

Finally, I come to this:

export BUILD_PREFIX=${PWD}/build-native

Next:

export PKG_CONFIG_PATH=${BUILD_PREFIX}/lib/pkgconfig
export LIBZMQ_ROOT=${PWD}/libzmq
export CZMQ_ROOT=${PWD}/czmq
export ZYRE_ROOT=${PWD}/zyre
...

Then, for libzmq, czmq, zyre and all other dependencies:

./autogen.sh
./configure \
	--prefix=${BUILD_PREFIX} \
	PKG_CONFIG_PATH=${PKG_CONFIG_PATH}
make
make install

make install will install all of them under ${BUILD_PREFIX}, instead of
/usr/local.

With this, Android build fails:

prompt> cd zyre/bindings/jni/zyre-jni/android
prompt> ./build.sh arm
...
:czmq-jni-native:copyLibs (Thread[Execution worker for ':',5,main]) completed. Took 0.054 secs.

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':czmq-jni-native:copyLibs'.
> Entry libcurl.so is a duplicate but no duplicate handling strategy has been set. Please refer to https://docs.gradle.org/7.4.2/dsl/org.gradle.api.tasks.Copy.html#org.gradle.api.tasks.Copy:duplicatesStrategy for details.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --debug option to get more log output.
> Run with --scan to get full insights.

prompt>

I googled a bit and found this happens frequently since Gradle 7:
gradle/gradle#17236

A workaround comes with adding something like duplicatesStrategy = DuplicatesStrategy.WARN,
in a build.gradle.

I had a deeper look and it seems that on my system, java.library.path is set to /usr/lib64 and /lib64 ...
Unfortunatelly, on recent RH-like systems:

prompt> ls -ald /lib64
lrwxrwxrwx. 1 root root 9 12 janv.  2020 /lib64 -> usr/lib64
prompt> 

Now, I have the duplicate search path...
libcurl.so is visible from /usr/lib64 and from /lib64...

Question:
The workaround works for me, and I could raise a PR, only for this.

But when I read this:
https://github.com/zeromq/czmq/blob/master/bindings/jni/czmq-jni-native/build.gradle#L15-L62
I think it would be a better idea to search for dependencies in BUILD_PREFIX first, then in system paths (in case one wants his
own dependency version, rather than the system one).

With previous versions of Gradle, I don't know what was happening:

• override existing libs (then the dependencies installed in BUILD_PREFIX were overriding system ones).
• silently skip existing libs (like with this workaround).

Your opinion on that ?
(changes to be made in ZProject too, I suppose)

[stephan57160]

Regarding only the duplicatesStrategy, I come with this modification, in https://github.com/zeromq/czmq/blob/master/bindings/jni/czmq-jni-native/build.gradle#L31-L61:

    def oldStrategy = duplicatesStrategy                     /* Backup */
    duplicatesStrategy = DuplicatesStrategy.WARN             /* Workaround, for duplicate library entries */
    libraryPaths.each { path ->
        from path
            include 'libczmqjni.so'
            include 'libczmqjni.dylib'
...
            include 'libmicrohttpd.dylib'
            include '*microhttpd*.dll'
        into 'build/natives'
    }
    duplicatesStrategy = oldStrategy                         /* Restore */

The Backup + Restore operation is there to keep existing behaviour on the rest ...
... in case ...

[stephan57160]

Regarding the local dependencies, I come with this, in the same file:

    def libraryPaths = []
    if (project.hasProperty('buildPrefix')) {
        if (osdetector.os == 'windows') {
            // DLLs are installed to the bin directory by cmake
            libraryPaths.add("${project.buildPrefix}/bin")
        }
        libraryPaths.add("${project.buildPrefix}/lib")
    }

    def javaLibraryPaths = System.getProperty('java.library.path').split(File.pathSeparator).toList()
    libraryPaths.addAll(javaLibraryPaths)

    libraryPaths.add('/usr/local/lib')
    if (osdetector.os == 'windows') {
        libraryPaths.add("${rootDir}/czmq-jni/build/Release")
    } else {
        libraryPaths.add("${rootDir}/czmq-jni/build")
    }

A couple of system.out.println() were added to validate this. No other way, for me, so far.