If your host system's architecture is 32 bits, remember to change the "x86_64"'s below to "x86"'s. On a similar vein, the examples below use the 4.8 toolchain; if you want to use something older or newer (for example, the 4.4.3 toolchain included in the 8th revision of the NDK), just change those to the relevant version.
With those two in hand, you should add
$ANDROID_NDK/toolchains/$TARGETARCH-4.8/prebuilt/`uname | tr '[A-Z]' '[a-z]'`-x86_64/bin
to your "PATH", where $ANDROID_NDK is the location where you unpacked the NDK, and $TARGETARCH is your target's architecture.
$ export ANDROID_TOOLCHAIN=/tmp/my-toolchain-$TARGETARCH
$ export SYSROOT=$ANDROID_TOOLCHAIN/sysroot
$ $ANDROID_NDK/build/tools/make-standalone-toolchain.sh \
--platform=android-9 \
--install-dir=$ANDROID_TOOLCHAIN \
--system=`uname | tr '[A-Z]' '[a-z]'`-x86_64 \
--toolchain=$TARGETARCH-4.8
Perl can be cross-compiled using either adb or a normal ssh connection; in general, if you can connect your device to the host using a USB port, or if you don't feel like installing an sshd app on your device, you may want to use adb, although you may be forced to switch to ssh if your device is not rooted and you're unlucky --- more on that later. Alternatively, if you're cross-compiling to an emulator, you'll have to use adb.
adb
To use adb, download the Android SDK from <https://developer.android.com/sdk/index.html>. The ``SDK Tools Only'' version should suffice --- if you downloaded the ADT Bundle, you can find the sdk under $ADT_BUNDLE/sdk/.
Add $ANDROID_SDK/platform-tools to your "PATH", which should give you access to adb. You'll now have to find your device's name using "adb devices", and later pass that to Configure through "-Dtargethost=$DEVICE".
However, before calling Configure, you need to check if using adb is a viable choice in the first place. Because Android doesn't have a /tmp, nor does it allow executables in the sdcard, we need to find somewhere in the device for Configure to put some files in, as well as for the tests to run in. If your device is rooted, then you're good. Try running these:
$ export TARGETDIR=/mnt/asec/perl
$ adb -s $DEVICE shell "echo sh -c '\"mkdir $TARGETDIR\"' | su --"
Which will create the directory we need, and you can move on to the next step. /mnt/asec is mounted as a tmpfs in Android, but it's only accessible to root.
If your device is not rooted, you may still be in luck. Try running this:
$ export TARGETDIR=/data/local/tmp/perl
$ adb -s $DEVICE shell "mkdir $TARGETDIR"
If the command works, you can move to the next step, but beware: You'll have to remove the directory from the device once you are done! Unlike /mnt/asec, /data/local/tmp may not get automatically garbage collected once you shut off the phone.
If neither of those work, then you can't use adb to cross-compile to your device. Either try rooting it, or go for the ssh route.
ssh
To use ssh, you'll need to install and run a sshd app and set it up properly. There are several paid and free apps that do this rather easily, so you should be able to spot one on the store. Remember that Perl requires a passwordless connection, so set up a public key.
Note that several apps spew crap to stderr every time you connect, which can throw off Configure. You may need to monkeypatch the part of Configure that creates "run-ssh" to have it discard stderr.
Since you're using ssh, you'll have to pass some extra arguments to Configure:
-Dtargetrun=ssh -Dtargethost=$TARGETHOST -Dtargetuser=$TARGETUSER -Dtargetport=$TARGETPORT
If using adb, a ``basic'' Configure line will look like this:
$ ./Configure -des -Dusedevel -Dusecrosscompile -Dtargetrun=adb \
-Dcc=$TARGETARCH-gcc \
-Dsysroot=$SYSROOT \
-Dtargetdir=$TARGETDIR \
-Dtargethost=$DEVICE
If using ssh, it's not too different --- we just change targetrun to ssh, and pass in targetuser and targetport. It ends up looking like this:
$ ./Configure -des -Dusedevel -Dusecrosscompile -Dtargetrun=ssh \
-Dcc=$TARGETARCH-gcc \
-Dsysroot=$SYSROOT \
-Dtargetdir=$TARGETDIR \
-Dtargethost="$TARGETHOST" \
-Dtargetuser=$TARGETUSER \
-Dtargetport=$TARGETPORT
Now you're ready to run "make" and "make test"!
As a final word of warning, if you're using adb, "make test" may appear to hang; this is because it doesn't output anything until it finishes running all tests. You can check its progress by logging into the device, moving to $TARGETDIR, and looking at the file output.stdout.
Notes
Once you have the toolchain set up properly, the only remaining hurdle is actually locating where in the device it was installed in. For example, CCTools installs its toolchain in /data/data/com.pdaxrom.cctools/root/cctools. With the path in hand, compiling perl is little more than:
export SYSROOT=<location of the native toolchain> export LD_LIBRARY_PATH="$SYSROOT/lib:`pwd`:`pwd`/lib:`pwd`/lib/auto:$LD_LIBRARY_PATH" sh Configure -des -Dsysroot=$SYSROOT -Alibpth="/system/lib /vendor/lib"
Natively compiling perl 5.30 or later should be as straightforward as:
sh Configure -des -Alibpth="/system/lib /vendor/lib"
This certainly works on Android 8.1 (Oreo) at least...