Using clang from NDK gradle build system - android-ndk

Question

Using the old Makefile-based Android build system it is possible to using clang to compile sources by adding
NDK_TOOLCHAIN_VERSION=clang
Is there some way to achieve the same thing using the new gradle build system?

Answer 1

It's not directly possible for now, but you can still use the regular Makefiles from gradle:
import org.apache.tools.ant.taskdefs.condition.Os
apply plugin: 'android'
android {
...
sourceSets.main {
jniLibs.srcDir 'src/main/libs' //set jniLibs directory to ./libs
jni.srcDirs = [] //disable automatic ndk-build call
}
// call regular ndk-build(.cmd) script from main src directory
task ndkBuild(type: Exec) {
if (Os.isFamily(Os.FAMILY_WINDOWS)) {
commandLine 'ndk-build.cmd', '-C', file('src/main').absolutePath
} else {
commandLine 'ndk-build', '-C', file('src/main').absolutePath
}
}
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn ndkBuild
}
}

Answer 2

Newer NDK revisions default to Clang. However, you can explicitly request a toolchain using the -DANDROID_TOOLCHAIN switch.
As of the Android Gradle Plugin 2.2.0 things have become much better. You can also adopt cmake. You should look over the new documentation.
android {
...
defaultConfig {
...
// This block is different from the one you use to link Gradle
// to your CMake or ndk-build script.
externalNativeBuild {
// For ndk-build, instead use ndkBuild {}
cmake {
// Passes optional arguments to CMake.
arguments "-DANDROID_TOOLCHAIN=clang"
// Sets optional flags for the C compiler.
cFlags "-D_EXAMPLE_C_FLAG1", "-D_EXAMPLE_C_FLAG2"
// Sets a flag to enable format macro constants for the C++ compiler.
cppFlags "-D__STDC_FORMAT_MACROS"
}
}
}
buildTypes {...}
productFlavors {
...
demo {
...
externalNativeBuild {
cmake {
...
// Specifies which native libraries to build and package for this
// product flavor. If you don't configure this property, Gradle
// builds and packages all shared object libraries that you define
// in your CMake or ndk-build project.
targets "native-lib-demo"
}
}
}
paid {
...
externalNativeBuild {
cmake {
...
targets "native-lib-paid"
}
}
}
}
// Use this block to link Gradle to your CMake or ndk-build script.
externalNativeBuild {
cmake {...}
// or ndkBuild {...}
}
}