Monday, November 9, 2009

native programming on android

Besides programming with java, we're also able to do native programming with c or c++ on android platform.
To do so, we need a cross compiler target on arm processor for our working platform( windows or linux). So I downloaded Sourcery G++ Lite 2009q3-68 for ARM EABI, the tool chain for arm. If you're careful enough, you would have noticed my mistake which took me a day to figure out. Unfortunately, I downloaded the wrong tool chain. The correct one is Sourcery G++ Lite 2009q3-67 for ARM GNU/Linux. This toolchain is used for target platform that runs linux operating system. If I were patient enough to read the getting started guide for the toolchain, I would found out that the first toolchain is for platforms that don't have operating system, and the second one is for linux.
From the embarrassing story, you may tell I'm still a freshman on embedded system. Surely I am. In the last embedded project I worked on, there is already a toolchain and building system up and running built by my experienced colleagues. So I don't need to care about this. Anyway, this frustrating but finally success experience gains me a lot.

Ensuing content is about the steps to build and run hello world with the toolchain.
  1. download the right toolchain and extract the package
  2. add bin to path environment variable for easier access to the toolchain
  3. add below source code

  4.         #include    "stdio.h"

    int main ( int argc, char *argv[] )
    printf("hello world!");
    return 0;
    } // ---------- end of function main ----------

  5. compile the code with arm-none-linux-gnueabi-gcc h.c -static. -static argument is necessary here because android uses a different c library with this toolchain. we must link the application statically against c lib, otherwise, the application will fail to run on android emulator.
  6. download the application to emulator with: adb push hello /data/
  7. log onto emulator with: adb shell
  8. add execution permission to the application with: chmod 777 /data/hello
  9. run the application /data/hello and we get desired output

Note, because we statically linked the c library so we used the c lib provided in the codesourcery arm toolchain rather than the custom Bionic c lib comes with ndk.

Update: native programming with android building system


tarek.attia said...

Thank you very much for these words really.
Helped me so much ,But I have a lil confusion here about the option "-static",how does the linker knows to use the android libraries instead of the libraries of the toolchain??

rxwen said...

The -static option here tells the linker to use libraries of the toolchain. The libs are linked statically to the applicaiton.
The android libraries aren't used at all.

MikeBrWade said...

I keep getting "permission denied" even as root when I try and run this cross compiled application any ideas?

Anonymous said...

it helped me a lot ......thank you ...

Anonymous said...

Thanks for this post.

Also, regarding Permission Denied.

instead of /data use /data/local this should work.

Jaime said...

Thank you for sharing this great post.
Check this one as well...
"Going Native in JavaScript to Boost Website Performance"