Native code compatibility is challenging. For this reason, device implementers are:
Managed Dalvik bytecode can call into native code provided in the application .apk file as an ELF .so file compiled for the appropriate device hardware architecture. As native code is highly dependent on the underlying processor technology, Android defines a number of Application Binary Interfaces (ABIs) in the Android NDK.
Device implementations:
[C-0-1] MUST be compatible with one or more defined ABIs and implement compatibility with the Android NDK.
[C-0-2] MUST include support for code running in the managed environment to call into native code, using the standard Java Native Interface (JNI) semantics.
[C-0-3] MUST be source-compatible (i.e. header-compatible) and binary-compatible (for the ABI) with each required library in the list below.
[C-0-4] MUST support the equivalent 32-bit ABI if any 64-bit ABI is supported.
[C-0-5] MUST accurately report the native Application Binary Interface (ABI) supported by the device, via the android.os.Build.SUPPORTED_ABIS, android.os.Build.SUPPORTED_32_BIT_ABIS, and android.os.Build.SUPPORTED_64_BIT_ABIS parameters, each a comma separated list of ABIs ordered from the most to the least preferred one.
[C-0-6] MUST report, via the above parameters, only those ABIs documented and described in the latest version of the Android NDK ABI Management documentation, and MUST include support for the Advanced SIMD (a.k.a. NEON) extension.
[C-0-7] MUST make all the following libraries, providing native APIs, available to apps that include native code:
[C-0-8] MUST NOT add or remove the public functions for the native libraries listed above.
[C-0-9] MUST list additional non-AOSP libraries exposed directly to third-party apps in /vendor/etc/public.libraries.txt.
[C-0-10] MUST NOT expose any other native libraries, implemented and provided in AOSP as system libraries, to third-party apps targeting API level 24 or higher as they are reserved.
[C-0-11] MUST export all the OpenGL ES 3.1 and Android Extension Pack function symbols, as defined in the NDK, through the libGLESv3.so library. Note that while all the symbols MUST be present, section 7.1.4.1 describes in more detail the requirements for when the full implementation of each corresponding functions are expected.
[C-0-12] MUST export function symbols for the core Vulkan 1.0 function symobls, as well as the VK_KHR_surface, VK_KHR_android_surface, VK_KHR_swapchain, VK_KHR_maintenance1, and VK_KHR_get_physical_device_properties2 extensions through the libvulkan.so library. Note that while all the symbols MUST be present, section 7.1.4.2 describes in more detail the requirements for when the full implementation of each corresponding functions are expected.
SHOULD be built using the source code and header files available in the upstream Android Open Source Project
Note that future releases of the Android NDK may introduce support for additional ABIs.
If device implementations are 64-bit ARM devices, then:
[C-1-1] Although the ARMv8 architecture deprecates several CPU operations, including some operations used in existing native code, the following deprecated operations MUST remain available to 32-bit native ARM code, either through native CPU support or through software emulation:
If device implementations include a 32-bit ARM ABI, they:
[C-2-1] MUST include the following lines in /proc/cpuinfo when it is read by 32-bit ARM applications to ensure compatibility with applications built using legacy versions of Android NDK.
Features: , followed by a list of any optional ARMv7 CPU features supported by the device.CPU architecture: , followed by an integer describing the device's highest supported ARM architecture (e.g., "8" for ARMv8 devices).SHOULD not alter /proc/cpuinfo when read by 64-bit ARM or non-ARM applications.