NAME

       perlandroid - Perl under Android

SYNOPSIS

       The first portions of this document contains instructions to cross-compile Perl for
       Android 2.0 and later, using the binaries provided by Google.  The latter portions
       describe how to build perl native using one of the toolchains available on the Play Store.

DESCRIPTION

       This document describes how to set up your host environment when attempting to build Perl
       for Android.

Cross-compilation

       These instructions assume an Unixish build environment on your host system; they've been
       tested on Linux and OS X, and may work on Cygwin and MSYS.  While Google also provides an
       NDK for Windows, these steps won't work native there, although it may be possible to
       cross-compile through different means.

       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.

   Get the Android Native Development Kit (NDK)
       You can download the NDK from <https://developer.android.com/tools/sdk/ndk/index.html>.
       You'll want the normal, non-legacy version.

   Determine the architecture you'll be cross-compiling for
       There's three possible options: arm-linux-androideabi for ARM, mipsel-linux-android for
       MIPS, and simply x86 for x86.  As of 2014, most Android devices run on ARM, so that is
       generally a safe bet.

       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.

   Set up a standalone toolchain
       This creates a working sysroot that we can feed to Configure later.

           $ 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

   adb or ssh?
       adb is the Android Debug Bridge.  For our purposes, it's basically a way of establishing
       an ssh connection to an Android device without having to install anything on the device
       itself, as long as the device is either on the same local network as the host, or it is
       connected to the host through USB.

       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

   Configure and beyond
       With all of the previous done, you're now ready to call Configure.

       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

       •   If you are targetting x86 Android, you will have to change "$TARGETARCH-gcc" to
           "i686-linux-android-gcc".

       •   On some older low-end devices -- think early 2.2 era -- some tests, particularly
           t/re/uniprops.t, may crash the phone, causing it to turn itself off once, and then
           back on again.

Native Builds

       While Google doesn't provide a native toolchain for Android, you can still get one from
       the Play Store.

   CCTools
       You may be able to get the CCTools app, which is free.  Keep in mind that you want a full
       toolchain; some apps tend to default to installing only a barebones version without some
       important utilities, like ar or nm.

       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"

   Termux
       Termux <https://termux.com/> provides an Android terminal emulator and Linux environment.
       It comes with a cross-compiled perl already installed.

       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...

AUTHOR

       Brian Fraser <fraserbn@gmail.com>