* Problem: Android NDK 22 download broken since support of NDK 23.
Due to the PR to support NDK 23.
With NDK 23, the archive file name has changed.
This change is handled by the PR to support NDK23, but now, only 23 and after
are supported.
Also, NDK 23 support introduced a 2nd occurence of the variable
HOST_PLATFORM, with another value. One occurence being exported,
this may confuse next developpers (and it actually confused me).
Solution: Code review
1st occurence is simply dropped, and the algorithm around is changed so that
there is no need of a 'host_platform' kind of stuff.
2nd occurrence is renamed to ANDROID_BUILD_PLATFORM.
Note that 'HOST' is replaced by 'BUILD', as this is the common naming
when talking about the build/compilation machine, when cross compiling.
A dedicated function is created in the helpers, to actually download
the NDK. As this function is made 'public', more checks are performed.
Note:
To be reported in CZMQ & ZYRE, via ZPROJECT, where NDK is downloaded
in 2 different files.
* Problem: Android build environment variables need clarifications.
Reason: All are spread and initialized throughout the code.
Solution: Declare, initialize and document environment variables on top of build.sh.
Side effect: This participates to documentation.
* Problem: Android APP fails to load ZMQ (ARM64 only)
Seen with physical Android devices running ARM64.
Not seen with ARM, X86 or X86_64.
Any Android APP loading ZMQ fails with:
```
[FATAL] Couldn't load library library zmq from jar. Dependency is required!
```
Unpack zyre-android-2.0.1.jar, find libzmq.so for ARM64 and look for missing
symbols:
```
prompt> unzip zyre-android-2.0.1.jar
prompt> cd lib/arm64-v8a
prompt> nm --undefined-only ./libzmq.so | head
U __aarch64_ldadd4_acq
U __aarch64_ldadd4_acq_rel
U __aarch64_ldadd4_rel
U __aarch64_ldadd4_relax
U __aarch64_ldadd8_acq_rel
U __aarch64_ldadd8_relax
U __aarch64_swp8_acq
U __aarch64_swp8_acq_rel
U __aarch64_swp8_rel
U __aarch64_swp8_relax
prompt>
```
Some more symbols are missing, but those are relevant for this issue.
OK.
These symbols are present in libc++_shared, but not exported ...:
```
prompt> nm libc++_shared.so | grep aarch64
00000000000ee6d0 t __aarch64_cas1_acq_rel
00000000000ee7a0 t __aarch64_cas8_acq_rel
00000000001028f0 b __aarch64_have_lse_atomics
00000000000ee840 t __aarch64_ldadd4_acq_rel
00000000000ee810 t __aarch64_ldadd4_rel
00000000000ee8a0 t __aarch64_ldadd8_acq_rel
00000000000ee870 t __aarch64_ldadd8_relax
00000000000ee7e0 t __aarch64_swp8_acq_rel
prompt>
```
Issue seen also on the WEB, with GCC & CLANG:
- https://bugzilla.redhat.com/show_bug.cgi?id=1830472
- cea175b838
- ...
Solution: Add `-mno-outline-atomics` to CXXFLAGS (FLUTTER fix).
Additionaly, had to introduce NDK_NUMBER.
This variable is calculated in `android_build_helper.sh`.
It represents the numeric form of NDK_VERSION:
```
NDK_VERSION --> NDK_NUMBER
android-ndk-r25 --> 2500
android-ndk-r23c --> 2303
android-ndk-r22 --> 2200
android-ndk-r21e --> 2105
... and so on
```
This will help a few other things (NDK download ?).
* Problem: Android APP fails to load ZMQ since NDK r25.x
With the help of the dump of ./configure options (former PR):
```
LIBZMQ (arm) - ./configure options to build 'LIBZMQ':
> --quiet
> TOOLCHAIN=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64
> CC=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi21-clang
> CXX=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi21-clang++
> LD=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/ld
> AS=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-as
> AR=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar
> RANLIB=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ranlib
> STRIP=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-strip
> CFLAGS= -D_GNU_SOURCE -D_REENTRANT -D_THREAD_SAFE
> CPPFLAGS= -I/home/stephan/git/zproject-android-testing/libzmq/builds/android/prefix/arm/include
> CXXFLAGS=
> LDFLAGS=-L/home/stephan/git/zproject-android-testing/libzmq/builds/android/prefix/arm/lib -L/tmp/android-ndk-r25/sour\
ces/cxx-stl/llvm-libc++/libs/armeabi-v7a
> LIBS=-lc -ldl -lm -llog -lc++_shared
> PKG_CONFIG_LIBDIR=/tmp/android-ndk-r25/prebuilt/linux-x86_64/lib/pkgconfig
> PKG_CONFIG_PATH=/home/stephan/git/zproject-android-testing/libzmq/builds/android/prefix/arm/lib/pkgconfig
> PKG_CONFIG_SYSROOT_DIR=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/sysroot
> PKG_CONFIG_DIR=
> --with-sysroot=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/sysroot
> --host=arm-linux-androideabi
> --prefix=/home/stephan/git/zproject-android-testing/libzmq/builds/android/prefix/arm
> --disable-curve
> --without-docs
```
We can observe that LDFLAGS has invalid `-L<path_to_libc++_shared.so>`:
```
-L/tmp/android-ndk-r25/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a
```
This path is no more valid, since NDK r25, where one should use LLVM path.
Ok, once this is fixed, ./configure requires also the path to libc.so.
I don't understand why libc.so is now required, actually, but without this, ./configure fails
to build its conftest.
Solution: Fix invalid LDFLAGS.
Notes:
- To be reported to CZMQ/ZYRE via ZPROJECT.
- Tested successfully with Android Emulator (x86 & x86_64).
- Still need some more work, as execution still fails with physical devices (observed on arm64).
- Introduced `ANDROID_STL`, `ANDROID_STL_ROOT` & `ANDROID_LIBC_ROOT`. All are initialized in `android_build_helper.sh`.
- New mechanism **MUST** be compatible with former NDK versions.
Proposal is to dump ./configure options to have an output like below:
```
LIBZMQ (x86_64) - ./configure options to build 'LIBZMQ':
> --quiet
> TOOLCHAIN=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64
> CC=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android21-clang
> CXX=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android21-clang++
> LD=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/ld
> AS=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-as
> AR=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar
> RANLIB=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ranlib
> STRIP=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-strip
> CFLAGS= -D_GNU_SOURCE -D_REENTRANT -D_THREAD_SAFE
> CPPFLAGS= -I/builds/CrisalidBox/zproject-android-testing/libzmq/builds/android/prefix/x86_64/include
> CXXFLAGS=
> LDFLAGS=-L/builds/CrisalidBox/zproject-android-testing/libzmq/builds/android/prefix/x86_64/lib -L/tmp/android-ndk-r25/sources/cxx-stl/llvm-libc++/libs/x86_64
> LIBS=-lc -ldl -lm -llog -lc++_shared
> PKG_CONFIG_LIBDIR=/tmp/android-ndk-r25/prebuilt/linux-x86_64/lib/pkgconfig
> PKG_CONFIG_PATH=/builds/CrisalidBox/zproject-android-testing/libzmq/builds/android/prefix/x86_64/lib/pkgconfig
> PKG_CONFIG_SYSROOT_DIR=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/sysroot
> PKG_CONFIG_DIR=
> --with-sysroot=/tmp/android-ndk-r25/toolchains/llvm/prebuilt/linux-x86_64/sysroot
> --host=x86_64-linux-android
> --prefix=/builds/CrisalidBox/zproject-android-testing/libzmq/builds/android/prefix/x86_64
> --disable-curve
> --without-docs
```
Note:
This mechanism is currently in use to identify/fix a bug in a recent PR for NDK update.
This mechanism is added before every call of `./configure`.
To be reported to CZMQ/ZYRE (via ZPROJECT).
Seen in the code:
```
function android_build_verify_so {
...
for dep_soname do
if [[ $elfoutput != *"library: [${dep_soname}]"* ]]; then
ANDROID_BUILD_FAIL+=("Library ${soname} was expected to be linked to library with soname:")
ANDROID_BUILD_FAIL+=(" ${dep_soname}")
fi
done
```
The `for xxx` syntax is wrong, most probably a typo somewhere.
Solution: Fix & complete the `for xxx` loop.
Tested with & without LIBSODIUM (only available dependent library for LIBZMQ).
Note: The same has to be done in ZPROJECT, for CZMQ & ZYRE.
Solution: Modify the build scripts so the user can specify the platform
for which to build, e.g. `./build.sh arm`. This approach originally
significantly reduces the parameters which have to be set before running
the script.
Further the build process is documented in a README now.
Solution: Migrate build scripts from Android NDK r11c to r20.
- Standalone toolchain
- Migration from GCC to Clang
- Migration from libgnustl to libc++
- Dropped support for API level below 16 (Android 4.1), previously it was API level 9 (Android 2.3)
- Dropped support for mips architecture
- The build script now start the build of all 4 Android architectures (arm, arm64, x86, x86_64)
Solution: set the appropriate options, environment variables and paths
so that the host pkg-config files are ignored, and the target ones are
used instead (if any)
