NOTES FOR ANDROID PLATFORMS =========================== Requirement details ------------------- Beside basic tools like perl and make you'll need to download the Android NDK. It's available for Linux, Mac OS X and Windows, but only Linux version was actually tested. There is no reason to believe that Mac OS X wouldn't work. And as for Windows, it's unclear which "shell" would be suitable, MSYS2 might have best chances. NDK version should play lesser role, the goal is to support a range of most recent versions. Configuration ------------- Android is naturally cross-compiled target and you can't use ./config. You have to use ./Configure and name your target explicitly; there are android-arm, android-arm64, android-mips, android-mip64, android-x86 and android-x86_64. Do not pass --cross-compile-prefix (as you might be tempted), as it will be "calculated" automatically based on chosen platform. Though you still need to know the prefix to extend your PATH, in order to invoke $(CROSS_COMPILE)gcc and company. (Configure will fail and give you a hint if you get it wrong.) Apart from PATH adjustment you need to set ANDROID_NDK environment to point at NDK directory as /some/where/android-ndk-. NDK customarily supports multiple Android API levels, e.g. android-14, android-21, etc. By default latest one available is chosen. If you need to target older platform, pass additional -D__ANDROID_API__=N to Configure. N is numeric value of the target platform version. For example, to compile for ICS on ARM with NDK 10d: ANDROID_NDK=/some/where/android-ndk-10d PATH=$ANDROID_NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH ./Configure android-arm -D__ANDROID_API__=14 Caveat lector! Earlier OpenSSL versions relied on additional CROSS_SYSROOT variable set to $ANDROID_NDK/platforms/android-/arch- to appoint headers-n-libraries' location. It's still recognized in order to facilitate migration from older projects. However, since API level appears in CROSS_SYSROOT value, passing -D__ANDROID_API__=N can be in conflict, and mixing the two is therefore not supported. Migration to CROSS_SYSROOT-less setup is recommended. One can engage clang by adjusting PATH to cover NDK's clang. Just keep in mind that if you miss it, Configure will try to use gcc... Also, PATH would need even further adjustment to cover unprefixed, yet target-specific, ar and ranlib (or not, if you use binutils-multiarch on your Linux). Running tests (on Linux) ------------------------ This is not actually supported. Notes are meant rather as inspiration. Even though build output targets alien system, it's possible to execute test suite on Linux system by employing qemu-user. The trick is static linking. Pass -static to Configure, then edit generated Makefile and remove occurrences of -ldl and -pie flags. You would also need to pick API version that comes with usable static libraries, 42/2=21 used to work. Once built, you should be able to env EXE_SHELL=qemu- make test If you need to pass additional flag to qemu, quotes are your friend, e.g. env EXE_SHELL="qemu-mips64el -cpu MIPS64R6-generic" make test