1Notes for Android platforms 2=========================== 3 4 Requirement details 5 ------------------- 6 7 Beside basic tools like perl and make you'll need to download the Android 8 NDK. It's available for Linux, macOS and Windows, but only Linux 9 version was actually tested. There is no reason to believe that macOS 10 wouldn't work. And as for Windows, it's unclear which "shell" would be 11 suitable, MSYS2 might have best chances. NDK version should play lesser 12 role, the goal is to support a range of most recent versions. 13 14 Configuration 15 ------------- 16 17 Android is a cross-compiled target and you can't rely on `./Configure` 18 to find out the configuration target for you. You have to name your 19 target explicitly; there are `android-arm`, `android-arm64`, `android-mips`, 20 `android-mip64`, `android-x86` and `android-x86_64` (`*MIPS` targets are no 21 longer supported with NDK R20+). 22 23 Do not pass --cross-compile-prefix (as you might be tempted), as it 24 will be "calculated" automatically based on chosen platform. However, 25 you still need to know the prefix to extend your PATH, in order to 26 invoke `$(CROSS_COMPILE)clang` [`*gcc` on NDK 19 and lower] and company. 27 (`./Configure` will fail and give you a hint if you get it wrong.) 28 29 Apart from `PATH` adjustment you need to set `ANDROID_NDK_ROOT` environment 30 to point at the `NDK` directory. If you're using a side-by-side NDK the path 31 will look something like `/some/where/android-sdk/ndk/<ver>`, and for a 32 standalone NDK the path will be something like `/some/where/android-ndk-<ver>`. 33 Both variables are significant at both configuration and compilation times. 34 The NDK customarily supports multiple Android API levels, e.g. `android-14`, 35 `android-21`, etc. By default latest API level is chosen. If you need to target 36 an older platform pass the argument `-D__ANDROID_API__=N` to `Configure`, 37 with `N` being the numerical value of the target platform version. For example, 38 to compile for Android 10 arm64 with a side-by-side NDK r20.0.5594570 39 40 export ANDROID_NDK_ROOT=/home/whoever/Android/android-sdk/ndk/20.0.5594570 41 PATH=$ANDROID_NDK_ROOT/toolchains/llvm/prebuilt/linux-x86_64/bin:$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin:$PATH 42 ./Configure android-arm64 -D__ANDROID_API__=29 43 make 44 45 Older versions of the NDK have GCC under their common prebuilt tools 46 directory, so the bin path will be slightly different. EG: to compile 47 for ICS on ARM with NDK 10d: 48 49 export ANDROID_NDK_ROOT=/some/where/android-ndk-10d 50 PATH=$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH 51 ./Configure android-arm -D__ANDROID_API__=14 52 make 53 54 Caveat lector! Earlier OpenSSL versions relied on additional `CROSS_SYSROOT` 55 variable set to `$ANDROID_NDK_ROOT/platforms/android-<api>/arch-<arch>` to 56 appoint headers-n-libraries' location. It's still recognized in order 57 to facilitate migration from older projects. However, since API level 58 appears in `CROSS_SYSROOT` value, passing `-D__ANDROID_API__=N` can be in 59 conflict, and mixing the two is therefore not supported. Migration to 60 `CROSS_SYSROOT`-less setup is recommended. 61 62 One can engage clang by adjusting PATH to cover same NDK's clang. Just 63 keep in mind that if you miss it, Configure will try to use gcc... 64 Also, PATH would need even further adjustment to cover unprefixed, yet 65 target-specific, ar and ranlib. It's possible that you don't need to 66 bother, if binutils-multiarch is installed on your Linux system. 67 68 Another option is to create so called "standalone toolchain" tailored 69 for single specific platform including Android API level, and assign its 70 location to `ANDROID_NDK_ROOT`. In such case you have to pass matching 71 target name to Configure and shouldn't use `-D__ANDROID_API__=N`. `PATH` 72 adjustment becomes simpler, `$ANDROID_NDK_ROOT/bin:$PATH` suffices. 73 74 Running tests (on Linux) 75 ------------------------ 76 77 This is not actually supported. Notes are meant rather as inspiration. 78 79 Even though build output targets alien system, it's possible to execute 80 test suite on Linux system by employing qemu-user. The trick is static 81 linking. Pass -static to Configure, then edit generated Makefile and 82 remove occurrences of -ldl and -pie flags. You would also need to pick 83 API version that comes with usable static libraries, 42/2=21 used to 84 work. Once built, you should be able to 85 86 env EXE_SHELL=qemu-<arch> make test 87 88 If you need to pass additional flag to qemu, quotes are your friend, e.g. 89 90 env EXE_SHELL="qemu-mips64el -cpu MIPS64R6-generic" make test 91