Install android ndk in linux and compile the sample code

NDK install

$ mkdir -p ~/ndk
$ cd ~/ndk/
$ curl -O https://dl.google.com/android/repository/android-ndk-r19c-linux-x86_64.zip
$ unzip android-ndk-r19c-linux-x86_64.zip
$ export ANDROID_NDK=/home/test/ndk/android-ndk-r19c

Sample

$ mkdir hello-ndk
$ cd hello-ndk/

• main.cpp

  $ cat << EOF > main.cpp
  #include <iostream>
  
  int main(int argc, char *argv[])
  {
     std::cout << "Hello ndk!" << std::endl;
     return 0;
  }
  EOF

• CMakeLists.txt

  $ cat  << EOF > CMakeLists.txt
  cmake_minimum_required(VERSION 3.5)
  project (hello_cmake)
  
  add_executable(hello_cmake main.cpp)
  EOF

  $ tree
  .
  ├── CMakeLists.txt
  └── main.cpp

  Build for linux executable

  $ mkdir build-linux
  $ cd build-linux
  $ cmake ..
  -- The C compiler identification is GNU 7.5.0
  -- The CXX compiler identification is GNU 7.5.0
  -- Check for working C compiler: /usr/bin/cc
  -- Check for working C compiler: /usr/bin/cc -- works
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Detecting C compile features
  -- Detecting C compile features - done
  -- Check for working CXX compiler: /usr/bin/c++
  -- Check for working CXX compiler: /usr/bin/c++ -- works
  -- Detecting CXX compiler ABI info
  -- Detecting CXX compiler ABI info - done
  -- Detecting CXX compile features
  -- Detecting CXX compile features - done
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /home/test/github/hello-ndk/build-linux
  $ make
  Scanning dependencies of target hello_cmake
  [ 50%] Building CXX object CMakeFiles/hello_cmake.dir/main.cpp.o
  [100%] Linking CXX executable hello_cmake
  [100%] Built target hello_cmake
  $ ./hello_cmake
  Hello ndk!

  Build for android executable

  $ mkdir build-android
  $ cd build-android
  $ cmake -DCMAKE_TOOLCHAIN_FILE=$ANDROID_NDK/build/cmake/android.toolchain.cmake -DANDROID_ABI="arm64-v8a" -DANDROID_NDK=$ANDROID_NDK -DANDROID_PLATFORM=android-21 ..
  -- Check for working C compiler: /home/test/ndk/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang
  -- Check for working C compiler: /home/test/ndk/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang -- works
  -- Detecting C compiler ABI info
  -- Detecting C compiler ABI info - done
  -- Detecting C compile features
  -- Detecting C compile features - done
  -- Check for working CXX compiler: /home/test/ndk/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++
  -- Check for working CXX compiler: /home/test/ndk/android-ndk-r19c/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ -- works
  -- Detecting CXX compiler ABI info
  -- Detecting CXX compiler ABI info - done
  -- Detecting CXX compile features
  -- Detecting CXX compile features - done
  -- Configuring done
  -- Generating done
  -- Build files have been written to: /home/test/github/hello-ndk/build-android
  
  $ make 
  Scanning dependencies of target hello_cmake
  [ 50%] Building CXX object CMakeFiles/hello_cmake.dir/main.cpp.o
  [100%] Linking CXX executable hello_cmake
  [100%] Built target hello_cmake
  $ ./hello_cmake
  -bash: ./hello_cmake: cannot execute binary file: Exec format error

  Run in android

  $ adb push build-android/hello_cmake /data/local/tmp
  # cd /data/local/tmp/
  /data/local/tmp # chmod +x hello_cmake ; ./hello_cmake
  Hello ndk!
  /data/local/tmp # file hello_cmake
  hello_cmake: ELF shared object, 64-bit LSB arm64, dynamic (/system/bin/linker64)

  Diff

  file

  $ file build-linux/hello_cmake
  build-linux/hello_cmake: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=8e568fb9403912403a9daeb3a85cc58b8dad46f7, not stripped
  
  $ file build-android/hello_cmake
  build-android/hello_cmake: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /system/bin/linker64, BuildID[sha1]=322bed0b22b9c27619b3b3a128322993667a5e7a, with debug_info, not stripped

  readelf -h

  $ readelf -h build-linux/hello_cmake
  ELF Header:
    Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
    Class:                             ELF64
    Data:                              2's complement, little endian
    Version:                           1 (current)
    OS/ABI:                            UNIX - System V
    ABI Version:                       0
    Type:                              DYN (Shared object file)
    Machine:                           Advanced Micro Devices X86-64
    Version:                           0x1
    Entry point address:               0x7b0
    Start of program headers:          64 (bytes into file)
    Start of section headers:          7064 (bytes into file)
    Flags:                             0x0
    Size of this header:               64 (bytes)
    Size of program headers:           56 (bytes)
    Number of program headers:         9
    Size of section headers:           64 (bytes)
    Number of section headers:         29
    Section header string table index: 28

  $ readelf -h build-android/hello_cmake
  ELF Header:
    Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
    Class:                             ELF64
    Data:                              2's complement, little endian
    Version:                           1 (current)
    OS/ABI:                            UNIX - System V
    ABI Version:                       0
    Type:                              DYN (Shared object file)
    Machine:                           AArch64
    Version:                           0x1
    Entry point address:               0xdf84
    Start of program headers:          64 (bytes into file)
    Start of section headers:          5142376 (bytes into file)
    Flags:                             0x0
    Size of this header:               64 (bytes)
    Size of program headers:           56 (bytes)
    Number of program headers:         9
    Size of section headers:           64 (bytes)
    Number of section headers:         39
    Section header string table index: 36