How to cross compile OpenSSL for 64 bit Android on OSX Darwin using NDK 19

Issue

I previously asked essentially the same question (different NDK) here and thought I correctly built openssl but once I got around to trying to link it to my app I discovered I didn't build it correctly.

1. If I bridge of the answer from @AlexCohn here I start with the setenv_android.sh script.

2. I modify the script to set THE_ARCH=arm64-v8a trying to target 64bit android architecture.

3. When I run the script there some things it fails to find:

   ERROR: Failed to find Android cpp. Please edit this script.
   ERROR: Failed to find Android gcc. Please edit this script.
   ERROR: Failed to find Android g++. Please edit this script.
   ERROR: AOSP_STL_INC is not valid. Please edit this script.
   ERROR: AOSP_STL_LIB is not valid. Please edit this script.
   ANDROID_NDK_ROOT: /Users/spartygw/android-ndk-r19/
   AOSP_TOOLCHAIN_PATH: /Users/spartygw/android-ndk-r19//toolchains/aarch64-linux-android-4.9/prebuilt/darwin-x86_64/bin
   AOSP_ABI: arm64-v8a
   AOSP_API: android-21
   AOSP_SYSROOT: /Users/spartygw/android-ndk-r19//platforms/android-21/arch-arm64
   AOSP_FLAGS: -funwind-tables -fexceptions -frtti
   AOSP_STL_INC: /Users/spartygw/android-ndk-r19//sources/cxx-stl/stlport/stlport/
   AOSP_STL_LIB: /Users/spartygw/android-ndk-r19//sources/cxx-stl/stlport/libs/arm64-v8a/libstlport_shared.so
   

4. When I look in /Users/spartygw/android-ndk-r19//toolchains/aarch64-linux-android-4.9/prebuilt/darwin-x86_64/bin there is no aarch64-linux-android-cpp or -gcc or -g++ just as the script output says:

   $ ls -1 ~/android-ndk-r19//toolchains/aarch64-linux-android-4.9/prebuilt/darwin-x86_64/bin
   ./
   ../
   aarch64-linux-android-addr2line
   aarch64-linux-android-ar
   aarch64-linux-android-as
   aarch64-linux-android-c++filt
   aarch64-linux-android-dwp
   aarch64-linux-android-elfedit
   aarch64-linux-android-gprof
   aarch64-linux-android-ld
   aarch64-linux-android-ld.bfd
   aarch64-linux-android-ld.gold
   aarch64-linux-android-nm
   aarch64-linux-android-objcopy
   aarch64-linux-android-objdump
   aarch64-linux-android-ranlib
   aarch64-linux-android-readelf
   aarch64-linux-android-size
   aarch64-linux-android-strings
   aarch64-linux-android-strip
   

This is where I think I got myself into trouble last time. I started hacking the script to get something that seemed to work and I'm sure what I did was wrong now.

I really don't understand the process so I'm hoping for help. Is anyone building arm64-v8a versions of OpenSLL successfully?

Solution

I was able to build, link, and run openssl for android arm64 with NDK r19. But I had to use the standalone toolchain generated from android-ndk-r19.

$ cd /path/to/android-ndk-r19
$ ./build/tools/make-standalone-toolchain.sh               \
            --toolchain=aarch64-linux-android

this will generate a dir called aarch64-linux-android in your tmp dir, put its bin directory in your path. Also, set your ANDROID_NDK_HOME to this location.

$ export PATH=/path/to/aarch64-linux-android/bin:${PATH}
$ export ANDROID_NDK_HOME=/path/to/aarch64-linux-android

then just run openssl's Configure and make.

$ cd /path/to/openssl1.1.1
$ ./Configure android-arm64
$ make

./Configure's output was as follows:

$ ./Configure android-arm64
Configuring OpenSSL version 1.1.1b-dev (0x10101020L) for android-arm64
Using os-specific seed configuration
Creating configdata.pm
Creating Makefile

**********************************************************************
***                                                                ***
***   OpenSSL has been successfully configured                     ***
***                                                                ***
***   If you encounter a problem while building, please open an    ***
***   issue on GitHub <https://github.com/openssl/openssl/issues>  ***
***   and include the output from the following command:           ***
***                                                                ***
***       perl configdata.pm --dump                                ***
***                                                                ***
***   (If you are new to OpenSSL, you might want to consult the    ***
***   'Troubleshooting' section in the INSTALL file first)         ***
***                                                                ***
**********************************************************************
$ 

and finally I created a new Android Studio project, with c++11, exceptions, and rtti support (through the new project wizard), and linked in the output of the build with a CMakeLists.txt slightly modified from the one created by Android Studio:

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
             native-lib

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/cpp/native-lib.cpp )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
              log-lib

              # Specifies the name of the NDK library that
              # you want CMake to locate.
              log )

# HERE ARE THE PARTS I EDITED:
# NOTE FOR THE COMMANDS ABOVE, THIS IS JUST THE OPENSSL SOURCE DIR.
set (SSL_PATH /path/to/ssl/build/outputs/)
include_directories(${SSL_PATH}/include)
set (open-ssl-libs ${SSL_PATH}/libssl.a ${SSL_PATH}/libcrypto.a)


# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       native-lib
                       # LINK SSL AND CRYPTO HERE:
                        ${open-ssl-libs}
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )

this is enough to show that it links, but I added one small reference to libssl.a in the boilerplate c++ code generated by Android Studio:

#include <jni.h>
#include <string>
#include <openssl/ssl.h>

extern "C" JNIEXPORT jstring JNICALL
Java_com_vernier_android_test_1ssl_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {

    SSL* ssl = SSL_new(nullptr);
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

and I ran the app successfully.

Answered By - sorenoid