Expose AR_...=llvm-ar with Android NDK 23+ toolchains

[montekki]

I am trying to build a project that has ring as a dependency that uses cc-rs which among other things requires invoking custom CC and ARs among other things.

Since r23 GNU binutils including stuff like x86_64-linux-android-ar have been removed so what I am trying to do is to point the build to the llvm-ar like this:

cargo {
	targets = ["x86_64"]
	apiLevel = 21
	exec { spec, toolchain ->
		if (toolchain.target == "x86_64-linux-android") {
			spec.environment("AR_x86_64_linux_android", "llvm-ar")
		}
	}
}

But apparently it has no effect and falls back with an error message

error occurred: Failed to find tool. Is `/home/$USER/Android/Sdk/ndk/24.0.8215888/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android-ar` installed?

[ncalexan]

Hmm, interesting. So the exec block should impact those variables for the actual invocation, but it won't impact the checking by the rust-android-gradle plugin itself -- and that's what you're seeing.

It rather sounds like we need to accommodate these changes to NDK 23+ in

rust-android-gradle/plugin/src/main/kotlin/com/nishtahir/RustAndroidPlugin.kt

Lines 110 to 152 in 5bfc241

	data class Toolchain(val platform: String,
	val type: ToolchainType,
	val target: String,
	val compilerTriple: String,
	val binutilsTriple: String,
	val folder: String) {
	fun cc(apiLevel: Int): File =
	if (System.getProperty("os.name").startsWith("Windows")) {
	if (type == ToolchainType.ANDROID_PREBUILT) {
	File("bin", "$compilerTriple$apiLevel-clang.cmd")
	} else {
	File("$platform-$apiLevel/bin", "$compilerTriple-clang.cmd")
	}
	} else {
	if (type == ToolchainType.ANDROID_PREBUILT) {
	File("bin", "$compilerTriple$apiLevel-clang")
	} else {
	File("$platform-$apiLevel/bin", "$compilerTriple-clang")
	}
	}
	fun cxx(apiLevel: Int): File =
	if (System.getProperty("os.name").startsWith("Windows")) {
	if (type == ToolchainType.ANDROID_PREBUILT) {
	File("bin", "$compilerTriple$apiLevel-clang++.cmd")
	} else {
	File("$platform-$apiLevel/bin", "$compilerTriple-clang++.cmd")
	}
	} else {
	if (type == ToolchainType.ANDROID_PREBUILT) {
	File("bin", "$compilerTriple$apiLevel-clang++")
	} else {
	File("$platform-$apiLevel/bin", "$compilerTriple-clang++")
	}
	}
	fun ar(apiLevel: Int): File =
	if (type == ToolchainType.ANDROID_PREBUILT) {
	File("bin", "$binutilsTriple-ar")
	} else {
	File("$platform-$apiLevel/bin", "$binutilsTriple-ar")
	}
	}

Patches wanted!

[montekki]

I was able to solve this with specifying an absolute path to ndk's llvm-ar

def ndkDir = android.ndkDirectory

exec { spec, toolchain ->
	if (toolchain.target == "x86_64-linux-android") {
		spec.environment("AR_x86_64-linux-android", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
	if (toolchain.target == "armv7-linux-androideabi") {
		spec.environment("AR_armv7-linux-androideabi", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
	if (toolchain.target == "aarch64-linux-android") {
		spec.environment("AR_aarch64-linux-android", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
}

[ncalexan]

I'm going to keep this open -- if the modern NDKs have changed layout, we want to accommodate in the code.

[Will5]

I'm facing the same problem.

I was able to solve this with specifying an absolute path to ndk's llvm-ar

def ndkDir = android.ndkDirectory

exec { spec, toolchain ->
	if (toolchain.target == "x86_64-linux-android") {
		spec.environment("AR_x86_64-linux-android", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
	if (toolchain.target == "armv7-linux-androideabi") {
		spec.environment("AR_armv7-linux-androideabi", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
	if (toolchain.target == "aarch64-linux-android") {
		spec.environment("AR_aarch64-linux-android", "$ndkDir/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar")
	}
}

@montekki, where did you add this?

I added it to the cargo block in my build.gradle file, but the error is still there

[montekki]

I added it to the cargo block in my build.gradle file, but the error is still there

check out our gradle file here

[ncalexan]

This should be fixed in the just published 0.9.3. Testing appreciated!

[Will5]

It seems the llvm-ar error is resolved, but now I am getting an lgcc error:

  = note: ld: error: unable to find library -lgcc
          clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

The release notes mention lgcc, so perhaps it is related.

[ncalexan]

It seems the llvm-ar error is resolved, but now I am getting an lgcc error:

  = note: ld: error: unable to find library -lgcc
          clang-12: error: linker command failed with exit code 1 (use -v to see invocation)

The release notes mention lgcc, so perhaps it is related.

Can I get more logs? Including some details on your build environment? The plugin takes care to use a linker invocation that rewrites -lgcc to -lunwind, perhaps we are somehow missing it when invoked within a build script? That seems possible.

[Will5]

I created a secret gist

[ncalexan]

I created a secret gist

Well, this is a first: those logs strongly suggest that you're building with cargo ndk, which isn't this plugin. In particular, you'll need the equivalent of #83 in your setup.

[Will5]

I created a secret gist

Well, this is a first: those logs strongly suggest that you're building with cargo ndk, which isn't this plugin. In particular, you'll need the equivalent of #83 in your setup.

You're right. I see someone added cargoNdk as a dependency of another task. I'm not sure what the solution is, but we can stay on NDK 22.