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