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