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1 | Notes 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`, `android-x86_64` and `android-riscv64` | |
21 | (`*MIPS` targets are no 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 `$ANDROID_NDK_ROOT/platforms/android-<api>/arch-<arch>` to | |
56 | appoint headers-n-libraries' location. It's still recognized in order | |
57 | to facilitate migration from older projects. However, since API level | |
58 | appears in `CROSS_SYSROOT` value, passing `-D__ANDROID_API__=N` can be in | |
59 | conflict, and mixing the two is therefore not supported. Migration to | |
60 | `CROSS_SYSROOT`-less setup is recommended. | |
61 | ||
62 | One can engage clang by adjusting PATH to cover the same NDK's clang. Just | |
63 | keep in mind that if you miss it, Configure will try to use gcc... | |
64 | Also, PATH would need even further adjustment to cover unprefixed, yet | |
65 | target-specific, ar and ranlib. It's possible that you don't need to | |
66 | bother, if binutils-multiarch is installed on your Linux system. | |
67 | ||
68 | Another option is to create so called "standalone toolchain" tailored | |
69 | for single specific platform including Android API level, and assign its | |
70 | location to `ANDROID_NDK_ROOT`. In such case, you have to pass matching | |
71 | target name to Configure and shouldn't use `-D__ANDROID_API__=N`. `PATH` | |
72 | adjustment becomes simpler, `$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 |