An Android Cross-Compiling Environment on Windows/UNIX-like systems using NDK | Ivan Kravets: "Creativity comes from talent and never from knowledge"

The Android NDK is a toolset that allows us to implement parts of our app using native-code languages such as C and C++. There are many articles about integrating Android SDK/NDK and writing some “C/C++” JNI compatible code. JNI is the Java Native Interface. It defines a way for managed code (written in the Java programming language) to interact with native code (written in C/C++).

But today we will talk about:

the native cross-compiling on the Windows/UNIX-like systems
uploading of the compiled binary file to the Android device
running the compiled binary file via Android CLI shell.

And what is interesting, we will not use the Android SDK (except adb utility) or any others Android sources 🙂

Downloading the tools

Download the latest Android NDK for our operating system from Android Developers site.

Windows Users. Download the Cygwin (this is a collection of tools which provide a Linux look and feel environment for Windows) from Cygwin Installation page.

Installing

The NDK installation process is very simple. The only step that we should do is to unzip the NDK archive. We can unzip it to any place because we can delete this folder later. Please remember this path because it will be needed to us to replace the <NDK> text in the commands below.

Windows Users. Please run the downloaded Cygwin Setup program and leave all options “by default” pressing “Next” on the each step. Then we should see the “Cygwin Terminal” link on our Desktop if the installation process successfully completed.

Setup Environment

Open the “Terminal” program based on our operation system (for Windows, open “Cygwin Terminal” that was installed in the previous step). All commands below should be executed to this “Terminal” application.
Then go to “NDK Build Tools” folder:

Shell

cd <NDK>/build/tools

1

cd <NDK>/build/tools

Example for Windows & Cygwin (in case we copied the extracted NDK content to the “C:/android-ndk” folder):

Shell

$ cd /cygdrive/c/android-ndk/build/tools/

1

$ cd /cygdrive/c/android-ndk/build/tools/
Now we must setup standalone Toolchain:

Shell

$ ./make-standalone-toolchain.sh --platform=<PLATFORM> --install-dir=<TOOLCHAIN> --ndk-dir=<NDK>

1

$ ./make-standalone-toolchain.sh --platform=<PLATFORM> --install-dir=<TOOLCHAIN> --ndk-dir=<NDK>
- <PLATFORM> the full list of Android platforms are available in “<NDK>/platforms”
- <TOOLCHAIN> please specify the directory where will be installed standalone toolchain.
Example for Windows & Cygwin below:

Shell

$ ./make-standalone-toolchain.sh --platform=android-9 --install-dir=/cygdrive/c/android-toolchain --ndk-dir=/cygdrive/c/android-ndk/

1

$ ./make-standalone-toolchain.sh --platform=android-9 --install-dir=/cygdrive/c/android-toolchain --ndk-dir=/cygdrive/c/android-ndk/
Then we need to update $PATH environment variable to include the “<TOOLCHAIN>/bin” directory, so we can execute compiler from any location:

Shell

$ export PATH=$PATH:<TOOLCHAIN>/bin/

1

$ export PATH=$PATH:<TOOLCHAIN>/bin/

Warning!!! When we will restart the “Terminal” program the $PATH variable will be restored to default value (without <TOOLCHAIN>). In this case we should write “export line that wrote above” to our home ~./bash_profile file with this command:

Shell

$ echo "export PATH=\$PATH:<TOOLCHAIN>/bin/" >> ~/.bash_profile

1

$ echo "export PATH=\$PATH:<TOOLCHAIN>/bin/" >> ~/.bash_profile

Example for Windows & Cygwin below:

Shell

$ echo "export PATH=\$PATH:/cygdrive/c/android-toolchain/bin/" >> ~/.bash_profile

1

$ echo "export PATH=\$PATH:/cygdrive/c/android-toolchain/bin/" >> ~/.bash_profile

Finish. Check ARM compiler version:

# For Unix-like OS
$ arm-linux-androideabi-gcc --version

# For Windows OS:
$ arm-linux-androideabi-gcc.exe --version

# For Unix-like OS

$ arm-linux-androideabi-gcc --version

# For Windows OS:

$ arm-linux-androideabi-gcc.exe --version

And we should receive the result like this:

$ arm-linux-androideabi-gcc.exe --version
arm-linux-androideabi-gcc.exe (GCC) 4.6 20120106 (prerelease)
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ arm-linux-androideabi-gcc.exe --version

arm-linux-androideabi-gcc.exe (GCC) 4.6 20120106 (prerelease)

This is free software; see the source for copying conditions. There is NO

warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiling the “Hello World” Program

For testing we will use the simple “Hello World” program:

# include <stdio.h>
int main()
{
  printf("Hello, world!\n");
  return 0;
}

# include <stdio.h>

int main()

{

printf("Hello, world!\n");

return 0;

}

Please copy the code that is mentioned above into “hello.c” file. The Cross-Compile command will look like:

$ arm-linux-androideabi-gcc hello.c -o hello.bin

1	$ arm-linux-androideabi-gcc hello.c -o hello.bin

After successful compilation we should see “hello.bin” file. Please read below how to run this file on our Android device.

Running the “Hello World” Program

For copying and running our “hello.bin” program we will need the “adb” tool. What is it? Android Debug Bridge (adb) is a versatile command line tool that lets us communicate with an emulator instance or connected Android-powered device.

Install the “adb” tool

Please go to the “Android SDK” page and click on the “DOWNLOAD FOR OTHER PLATFORMS” link (located at the bottom of the page). From the second table named as “SDK Tools Only” please download the SDK for our operation system. Then unpack it (or install it if we are using Windows & SDK Installer version) to any place (later we will use this path to SDK folder as <SDK>).

Then we need to install the “Android SDL Platform-tools”. We can do it with the “Android SDK Manager”. Run it:

# For Unix-like OS:
$ <SDK>/tools/android

# For Windows OS:
$ <SDK>/tools/android.bat

# For Unix-like OS:

$ <SDK>/tools/android

# For Windows OS:

$ <SDK>/tools/android.bat

In the launched “Android SDK Manager” please do these steps:

Click on the “Deselect All” link
Check the “Android SDK Platform-tools”
Click on the “Install 1 package…” button
Accept the “Android SDK License”
Press the “Install” button

If all steps completed successfully we should see the “Android SDK Platform-tools” status as “Installed”. Now please connect our Android-based device to PC and check it with “adb” tool:

$ <SDK>/platform-tools/adb devices

# Example of this command:
$ <SDK>/platform-tools/adb devices
List of devices attached
333039F85F1C00EC	device

$ <SDK>/platform-tools/adb devices

# Example of this command:

$ <SDK>/platform-tools/adb devices

List of devices attached

333039F85F1C00EC device

Install the “hello.bin” program

The easiest way to install binary program is to copy it to any folder on “Android device” where we can setup the “Execute Permission” for the “hello.bin” file. In my case, I have “rooted device” and I can copy binary file to any place. The “copy” command will look like:

$ <SDK>/platform-tools/adb push <the path to the binary file on our PC> <the path to the folder on the Android device>

# For example:
$ <SDK>/platform-tools/adb push hello.bin data/local/tmp/
532 KB/s (6168 bytes in 0.011s)

$ <SDK>/platform-tools/adb push <the path to the binary file on our PC> <the path to the folder on the Android device>

# For example:

$ <SDK>/platform-tools/adb push hello.bin data/local/tmp/

532 KB/s (6168 bytes in 0.011s)

Run the “hello.bin” program

Firstly, we should grant “hello.bin” file with “Execute Permission”. So, now open the command line shell on our “Android device” and execute these commands in order:

$ <SDK>/platform-tools/adb shell
android@shell: $ cd <the path to the folder on the Android device>
android@shell: $ chmod 755 hello.bin

# For example,
$ <SDK>/platform-tools/adb shell
root@crespo:/ $ cd data/local/tmp/
root@crespo:/data/local/tmp $ chmod 755 hello.bin

$ <SDK>/platform-tools/adb shell

android@shell: $ cd <the path to the folder on the Android device>

android@shell: $ chmod 755 hello.bin

# For example,

$ <SDK>/platform-tools/adb shell

root@crespo:/ $ cd data/local/tmp/

root@crespo:/data/local/tmp $ chmod 755 hello.bin

And now run the program:

android@shell: $ ./hello.bin

# Example
root@crespo:/data/local/tmp $ ./hello.bin
Hello, world!

android@shell: $ ./hello.bin

# Example

root@crespo:/data/local/tmp $ ./hello.bin

Hello, world!

The end! 🙂 If this article helped you please share it with yours friends. Thanks!