inportb

I return to school at noon, but before then, I’d like to share my evening project: agcc.bash, a rewrite of agcc and agcc2.pl that works with revisions 6 and 7 of the Android NDK.

The NDK is a GCC-based cross-compiler that lets you embed object code in a traditional Android app. It also works as a standalone cross-compiler, though it is not advertised as such. It is quite rough when used by itself, and agcc wraps the complexity in a little script. While agcc and agcc2.pl are written in Perl, agcc.bash is a Bash script. It also supports the latest revisions of the NDK, though r7 is slightly buggy.

With agcc.bash, building native Android software feels almost like working with GCC. As a quick example, let’s try the classic hello world:

AGCC_NDK=~/android-ndk-r6 ./agcc.bash hello.c -o hello

That wasn’t too exciting… but what happened there? I have the NDK installed at ~/android-ndk-r6 and I told agcc.bash where to look for it, using the AGCC_NDK environment variable. I then invoked agcc.bash as if it were GCC. Let’s see what agcc.bash did behind the scenes:

AGCC_NDK=~/android-ndk-r6 AGCC_ECHO=yes ./agcc.bash hello.c -o hello

=> ./agcc.bash hello.c -o hello
<= /home/jyio/android-ndk-r6/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc -o hello -I/home/jyio/android-ndk-r6/platforms/android-8/arch-arm/usr/include -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -DANDROID -DSK_RELEASE -DNDEBUG -UDEBUG -march=armv5te -mtune=xscale -msoft-float -mthumb-interwork -fpic -fno-exceptions -ffunction-sections -funwind-tables -fmessage-length=0 -march=armv5te -mtune=xscale -msoft-float -mthumb-interwork -fpic -fno-exceptions -ffunction-sections -funwind-tables -fmessage-length=0 hello.c -Bdynamic -Wl,-T,/home/jyio/android-ndk-r6/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/arm-linux-androideabi/lib/ldscripts/armelf_linux_eabi.x -Wl,-dynamic-linker,/system/bin/linker -Wl,–gc-sections -Wl,-z,nocopyreloc -Wl,–no-undefined -Wl,-rpath-link=/home/jyio/android-ndk-r6/platforms/android-8/arch-arm -L/home/jyio/android-ndk-r6/platforms/android-8/arch-arm/usr/lib -nostdlib /home/jyio/android-ndk-r6/platforms/android-8/arch-arm/usr/lib/crtend_android.o /home/jyio/android-ndk-r6/platforms/android-8/arch-arm/usr/lib/crtbegin_dynamic.o -lc /home/jyio/android-ndk-r6/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a -lm -ldl

See how it transformed our innocent little command into a monster! This might be overkill for a hello world program, but it provides pretty good support for more complex software such as OpenSSL, cURL, and Python. It would be a good idea to add the NDK toolchain and agcc.bash to $PATH before trying to build a big program. In my case, the toolchain resides in ~/android-ndk-r6/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin. If you want to build some software that come with configure scripts, you might start with:

CC=agcc.bash ./configure

Do try this at home! Relevant links:

• Android NDK r6 (or, the latest version)
• agcc.bash
• hello.c

Opkg is not limited to using packages from files; it is also capable of using apt-get style repositories, vastly simplifying the job of fetching dependencies and updating packages. I already have a repository set up, and it could be added as such

echo "src/gz inportb-android-froyo http://repo.inportb.com/android/froyo" > /cache/etc/opkg/inportb.conf

After doing that, we could refresh the package list

opkg update

Installing a package then becomes as easy as

opkg install name-of-package

And we could keep all our packages up-to-date using

opkg update; opkg upgrade

It’s also quite simple to set up a repository for distributing packages.

Read on »

Now that we have Opkg for Android, we could use it to install packages from local files or off Web servers. Installing a package is as simple as

opkg install path/to/package.opk

or, if it’s on the Web

opkg install http://host/path/to/package.opk

And to remove the package, we would go

opkg remove name-of-package

But what if we wanted to share our own software with others? In this case, we would create our own packages. An Opkg package is essentially a Debian package with fewer control fields. If you know how to make a Debian package, you should be well on your way. In general, a package is an ar archive containing a control tarball, a data tarball, and a debian-binary file. For example let’s have a look at the opkg-hello package:

Read on »

Well, almost. While one could theoretically install Debian packages on Android phones, it is generally a bad idea to install software designed for one system onto a different system. However, the Debian package manager is excellent for keeping track of software, and it would be nice if it could be used on Android as well. iPhone users already have access to this mechanism in the form of Cydia, so why not put it on Android too?

Read on »