[question] How do you set the NDK path for Android builds in CMakeToolchain?

I’m trying to figure out how to build for Android using the Conan 2.0 CMakeToolchain. I get this error:

ConanException: CMakeToolchain needs tools.android:ndk_path configuration defined

The docs mention tools.android:ndk_path, but not how to set it. There are a few clues in the source code, but all the things I’ve tried in conanfile.py and conan.conf haven’t worked. This was very easy with the cmake generator, I just did this:

cmake.definitions["CMAKE_TOOLCHAIN_FILE"] = os.getenv("ANDROID_NDK_ROOT") + "/build/cmake/android.toolchain.cmake"

…but it doesn’t work anymore.

Currently, I share this Python script with my Conan 1.x packages to define build settings for desktop and mobile platform builds: https://github.com/ssrobins/conan-cmake_utils/blob/217df94/cmake_utils.py.

In addition to being stuck on this, I’m a bit concerned that Conan 2.0 will make it not possible or at least harder to use custom toolchains, which is critical for close-sourced platforms that don’t have any built-in CMake support.

[ssrobins]

Thanks @memsharded, putting that code in ~/.conan/profiles/default allowed NDK to be found. Unfortunately, it failed right after with:

Invalid Android STL: None.
CMake Error: CMake was unable to find a build program corresponding to "Ninja Multi-Config".  CMAKE_MAKE_PROGRAM is not set.  You probably need to select a different build tool.

I tried adding ANDROID_STL and CMAKE_MAKE_PROGRAM, even though ninja is in my PATH and is working in non-Conan 2.0 packages, but it didn’t help. Here’s my full generate() method:

def generate(self):
    tc = CMakeToolchain(self)
    if self.settings.os == "Android":
        tc.generator = "Ninja Multi-Config"
        tc.variables["CMAKE_MAKE_PROGRAM"] = "/usr/local/bin/ninja"
        tc.variables["ANDROID_STL"] = "c++_static"
    elif self.settings.os == "iOS":
        tc.generator = "Xcode"
        tc.variables["CMAKE_OSX_DEPLOYMENT_TARGET"] = self.settings.os.version
    elif self.settings.os == "Linux":
            tc.generator = "Ninja Multi-Config"
    elif self.settings.os == "Macos":
        tc.generator = "Xcode"
        tc.variables["CMAKE_OSX_DEPLOYMENT_TARGET"] = self.settings.os.version
    tc.generate()
    deps = CMakeDeps(self)
    deps.generate()

The CMAKE_OSX_DEPLOYMENT_TARGET for macOS and iOS are working so this seems to only affect the Android builds.

For Conan 1.x, this is all I had to add to my conanfile.py to build Android:

if settings.os == "Android":
    cmake.generator = "Ninja Multi-Config"
    if settings.arch == "armv7":
        cmake.definitions["ANDROID_ABI"] = "armeabi-v7a"
    elif settings.arch == "armv8":
        cmake.definitions["ANDROID_ABI"] = "arm64-v8a"
    cmake.definitions["ANDROID_TOOLCHAIN"] = "clang"
    cmake.definitions["ANDROID_STL"] = "c++_static"
    cmake.definitions["CMAKE_TOOLCHAIN_FILE"] = os.getenv("ANDROID_NDK_ROOT") + "/build/cmake/android.toolchain.cmake"

I was just able to pass CMake params exactly how it would work without Conan. Yes it’s more code than if it was taken care of for me, but I appreciated the transparency and simplicity. It let me use the ANDROID_NDK_ROOT environment variable as the single definition for NDK on my system that works for CMake and Conan 1.x. It’s also starting to become the standard in cloud CI environments like GitHub Actions.

For the Android toolchain as well as any custom toolchain, I would love for this to be done with a setting in the conanfile.py, like it was before. The cmake interface is excellent in Conan 1.x, I don’t understand why it’s being made less discoverable and spread to multiple files for Conan 2.x.

[memsharded]

Just created a new one from your comment in https://github.com/conan-io/conan/issues/9282, please track it and provide feedback there. Thanks!