Creating an x86 and ARM* APK using the Intel® Compiler and GNU* gcc

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Table of Contents

1. Introduction
2. Preparing the Build Environment
3. Build from Command Line
   1. Configuring the Application
   2. Cleaning the Application Workspace
   3. Building the Binary for ARM* Architecture
   4. Building the Binary for x86 Architecture
   5. Preparing Application package (APK)
4. Build from Eclipse* IDE
5. Note on Avoiding Cleanup of Binaries under .\libs\[targetabi]
6. Other Related Articles and Resources

Introduction

There are Android* devices running on processors supporting ARM* or x86 instruction set architectures (ISA). Different ISAs are not binary compatible and hence an application, if containing native code, should provide native libraries for each targeted ISA. The 'fat' Android* application packages ('fat' APK) is one of the distribution mechanisms for such applications.

This article provides the step by step instructions on building such 'fat' apk that includes the ISA-independent dex files for Dalvik* virtual machine (Dalvik, 2013) as well as the libraries for different ISA targets. It includes building the native application library for x86 using Intel® Integrated Native Developer Experience (INDE).

We will use hello-jni sample from the NDK r10 distribution for demonstration (which comes with Intel® INDE install).

Preparing the Build Environment

The following tools are necessary and these instructions should be follow in order:

1. Install:
   • Microsoft* .NET Framework
   • Java* Development Kit 7u67 assuming installed at [jdk7-dir]
2. Add this directory to the "PATH" environment variable:
   • Directory "[jdk7-dir]\jre\bin" for using "java" VM. This is required by "ant" tool
     For Windows environment, make sure to use short-folder name like "PROGRA~2" for "program files (x86)"
3. Create a new env-var:
   • "JAVA_HOME=[jdk7-dir]"
4. Install:
   • Intel® Integrated Native Developer Experience assuming installed at [inde-dir]
5. Add this directory to the "PATH" environment variable:
   • Directory "[ant-dir]\bin" for using "ant" tool (Default location of [ant-dir] is: [inde-dir]\IDEintegration)

Build from Command Line

This section provides the instructions on how to create the APK package to support Android devices with ARM* and x86 architectures from a command line build environment.

First open a command window or terminal window on Linux*; go to the Android NDK sample "hello-jni" directory [ndk-dir]\samples\hello-jni; and follow the steps below.

Note: All the tools noted in above section should be accessible from this window.

1. Configuring the Application

   Run the following command from the "hello-jni" directory to generate a build.xml file that will be used to build the sample later.

   $ android update project --target android-19 --name HelloJni --path . --subprojects
   
   Note:
   --target android-19: corresponds to to Android 4.4 (KITKAT) release.

2. Cleaning the Application Workspace

   Use the following command to clean the whole workspace including libraries for all ISA architectures.
   $ ant clean
$ ndk-build V=1 APP_ABI=all clean
   
   Note:
   . V=1 : prints all the commands as they are being executed.
   . APP_ABI=all : forces cleanup of intermediate files for all targets. If this parameter is omitted only the armeabi target will be cleaned.

3. Building the Binary for ARM* Architecture

   Use the command below to build the application binary for ARM architecture:
   $ ndk-build APP_ABI=armeabi-v7a V=1 NDK_TOOLCHAIN=arm-linux-androideabi-4.8
   
   Note:
   . APP_ABI=armeabi-v7a : configures compilation for the ARM* target.
   . NDK_TOOLCHAIN=arm-linux-androideabi-4.8 : overrides the default GNU* gcc 4.6 and uses gcc 4.8.

   The application binary (libhello-jni.so ) is created at .\libs\armeabi-v7a\libhello-jni.so

4. Building the Binary for x86 Architecture with Intel Compiler

   Use the command below to build the application binary with Intel compiler for x86 architecture:
   $ ndk-build APP_ABI=x86 V=1 NDK_TOOLCHAIN=x86-icc NDK_APP.local.cleaned_binaries=true
   
   Note:
   . APP_ABI=x86 : configures compilation for the x86 architecture.
   . NDK_TOOLCHAIN=x86-icc : overrides default compiler gcc 4.6 with Intel C/C++ compiler for Android.
   . NDK_APP.local.cleaned_binaries=true : suppresses the library removal in the libs/armeabi directory. See notes at the bottom.

   The application binary (libhello-jni.so ) is created at .\libs\x86\libhello-jni.so

5. Preparing Application package (APK)

   After all of the binaries have been built for each Android target, check that the libs\[targetabi] directory contains required library for each targeted architecture.

   To simplify the package creation and avoid package signing, use the following command to create a debug package:
   $ ant debug

   After that the new HelloJni-debug.apk package can be found in the .\bin directory. It can be run on x86* or ARM* emulators supporting API level 19 or higher provided by Android SDK.
   The HelloJni-debug.apk package contains libraries for 2 targets: ARM EABI v7a and x86.

Build from Eclipse* IDE

1. Open Eclipse and load the sample [inde-dir]/IDEintegration/NDK/samples/hello-jni
   • Select menu File > New > Project > Android
   • Select the Android Project from Existing Code button
   • In the Root Directory field, click Browse... and select the [ndk-dir]/samples directory.
   • Then click Deselect All and select only the project: hello-jni
   • Check the box the says Copy projects into workspace
   • Click Finish.
2. Add Native Support to the project:
   • Right click on project name and select Android Tools > Add Native Support...
   • Click Finish.
   Note: If you see the console error "Unable to launch cygpath" after this step it can be ignored and will not affect your project.
3. Create a separate build configuration for each target platform and set build command
   Right click on project and select Properties -> C/C++ Build -> "Manage configurations..."
   Click New... to add the following new configurations based on Default configuration:
   • Name: x86_icc Description: For x86 target using Intel Compiler icc
   • Name: arm_gcc Description: For ARM target using GNU gcc
   Still on the same Project Properties window, set Configuration to "x86_icc":
   • Uncheck "Use default build command"
   • Adding following to Build command field:
     ndk-build APP_ABI=x86 NDK_TOOLCHAIN=x86-icc
   • Click Apply
   Again on the same Project Properties window, set Configuration to "arm_gcc":
   • Uncheck "Use default build command"
   • Adding following to Build command field:
     ndk-build APP_ABI=armeabi-v7a NDK_TOOLCHAIN=arm-linux-androideabi-4.8
   • Click Apply and then OK
4. Clean the whole application workspace
   • If Application.mk exists under [eclipse-workspace-dir]\HelloJni\jni directory, make sure it does not have the following line:
     NDK_APP.local.cleaned_binaries=true
   • Right click on project and select Build configurations > Clean all…
5. Create Application.mk under [eclipse-workspace-dir]\HelloJni\jni directory is it does not exist, and make sure it has the following line:
   NDK_APP.local.cleaned_binaries=true
6. Build the app binary for ARM* target using gcc and x86 target using Intel Compiler.
   • Right click on project and select Build Configurations > Build Selected...
   • Select both "arm_gcc" and "x86_icc"
   • Click Ok.
   • Verify the output binary files at:
     • [eclipse-workspace-dir]\HelloJni\libs\armeabi-v7a\libhello-jni.so
     • [eclipse-workspace-dir]\HelloJni\libs\x86\libhello-jni.so
7. Create unsigned application packages
   Right click on project and select Android Tools > Export Unsigned Application Package...

Note on Avoiding Cleanup of Binaries under .\libs\[targetabi]

Use of NDK_APP.local.cleaned_binaries=true parameter to suppress the removal of the previously built libraries may stop working in the future NDK releases. Please consult the [ndk-dir]/build/core/setup-app.mk makefile on how to disable delete actions for the target clean-installed-binaries.

Other Related Articles and Resources

• NDK Android* Application Porting Methodologies
• Changing the default compiler back from Intel C++ Compiler to GCC for x86 targets
• Intel® C++ Compiler for Mac OS* - Compatibility with the GNU* gcc and g++ compilers
• Android* NDK for Intel® Architecture
• Speeding Up the Android* Emulator on Intel® Architecture

To learn more about Intel tools for the Android development, visit Intel® Developer Zone for Android.