Replicant

h1. Build a Native Developement Kit (NDK) with Replicant 4.2

h2. Principle of operation

The [[ReplicantSourceCode|Android 4.2 source code]] ships a @ndk@ directory with NDK build scripts.

These tools download various upstream imports from https://git.androidproject.xxx/toolchain/XXX/ with optional commit date (no branches or tags), apply patches, and build them.

Note: as of 2015-07, the upcoming Android version moved to a different build system, and will populate $topdir/toolchain/ through @repo@ instead of invoking git in a temporary directory (i.e. ditched @download-toolchain-sources.sh@).

h2. Ubuntu 12.04 build environment with LXC

Replicant 4.2 is based on CyanogenMod 10.1 which is based on AOSP 4.2.2 (2013-02).

The build environment used by NDK release managers should be Ubuntu LTS 12.04.

We recreate it through LXC.  If you know how to use Triskel 6 instead, please contribute the instructions.

<pre>

lxc-create -n replicant -t download -- -d ubuntu -r precise -a amd64

# Note: or Triskel 6, if you know how to configure LXC/debootstrap for it

lxc-start -n replicant -d

lxc-attach -n replicant

# clean-up non-free sources

sed -i -e 's/ restricted//' -e 's/ multiverse//' /etc/apt/sources.list

apt-get update

# prepare build user

apt-get install openssh-server

useradd replicant --shell /bin/bash --create-home

mkdir -p -m 700 ~replicant/.ssh

cat <<EOF >> ~replicant/.ssh/authorized_keys

your public key

EOF

chown -R replicant: ~replicant

</pre>

Note: compiling from Debian 8 will yield errors from texinfo (doc in binutils) and Perl (POD in LLVM) due to more recent, stricter versions of these.

h2. Build dependencies

<pre>

# Base Android build dependencies (from https://source.android.com/source/initializing.html, section "Installing required packages (Ubuntu 12.04)")

# Dropping mingw to skip windows builds for now.

# Installing g++-multilib first otherwise apt-get complains.

apt-get install build-essential g++-multilib

apt-get install git gnupg flex bison gperf \

  zip curl libc6-dev libncurses5-dev:i386 x11proto-core-dev \

  libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 \

  libgl1-mesa-dev \

  python-markdown libxml2-utils xsltproc zlib1g-dev:i386

# Additional NDK build dependencies (completed from https://android.googlesource.com/platform/ndk/+/master/README.md)

apt-get install curl texinfo bison flex libtool pbzip2 groff

# Make 'bash' the default shell otherwise 'build-gabi++.sh' will fail

dpkg-reconfigure dash

</pre>

h2. Preparing the sources

Based on [[ReplicantSourceCode]] with additional configuration.

Login as user @replicant@ and:

<pre>

mkdir ~/tools/

cd ~/tools/

wget http://commondatastorage.googleapis.com/git-repo-downloads/repo

chmod a+x repo

cd ~

cat <<EOF >> ~/.bashrc

export USE_CCACHE=1

EOF

# Avoid prompts

git config --global user.email "you@example.com"

git config --global user.name "Your Name"

git config --global color.ui true

mkdir replicant-4.2/

cd replicant-4.2/

../tools/repo init -u git://git.replicant.us/manifest.git -b replicant-4.2

../tools/repo sync -j4 

# > 1h, 27GB (inc. 17GB .repo)

</pre>

h2. Determining the checkout date

Since there's no NDK release tag for the @toolchain/@ Git checkouts, we need to find the right date.

@cd ndk/ && git log@ says the last commit is 2012-10-05, so it's around NDK r8b (2012-07) and NDK r8c (2012-11).

Checking @build/tools/toolchain-patches/@ in the NDKs shows r8c has matching patches.

Also NDKs from google contain several @SOURCES@ files listing Git repos and commit IDs.

With r8c's release date (@ls --full-time RELEASE.TXT@ => 2012-10-22 05:59), @build/tools/download-toolchain-sources.sh@ checkouts the same Git commit IDs, and the patches apply.

Only, r8c references a LLVM Git repo, while our scripts download a tarball.

So our scripts match a NDK version between r8b and r8c, and can almost exactly reproduce r8c. Let's call it r8b2.

h2. Building the SDK

Based on @ndk/docs/DEVELOPMENT.html@, with much improvement :)

<pre>

export NDK=~/replicant-4.2/ndk

cd $NDK

# Allow checking build errors

export NDK_LOGFILE=$HOME/ndk.log

# Follow Python download redirection

sed -i -e 's/curl -S/curl -L -S/' build/tools/download-toolchain-sources.sh

# Get the sources from toolchain/ repos, with r8c release date:

bash $NDK/build/tools/download-toolchain-sources.sh --git-date='2012-10-22T05:59:40Z' ~/ndk-dl

# ndk-dl: 2.5GB

# Define NDK_TMPDIR and and use --incremental so the build can be resumed on error

export NDK_TMPDIR=~/ndk-tmp

mkdir -p $NDK_TMPDIR/release-r8b2/

# Build the release

bash $NDK/build/tools/make-release.sh --toolchain-src-dir=$HOME/ndk-dl --release=r8b2 --incremental

# 30mn with 4 cores, 28GB (inc. 17GB .repo), 2.5GB ndk-dl, 1GB /tmp

</pre>

The GNU/Linux NDK release is in @/tmp/ndk-replicant/release/android-ndk-r8b2-linux-x86.tar.bz2@ :)

h2. TODOs

h3. Mirror @toolchain/@ repos

@download-toolchain-sources.sh@'s default is @--git-base=https://android.googlesource.com/toolchain@.

Should we use a git.replicant.us repo? (note: there's no 'toolchain' there yet)

h3. Windows build

Build deps:

<pre>

# windows build is triggered by the presence of mingw32

apt-get install mingw32 tofrodos

# and requires running maketab.exe

apt-get install wine

# I had troubles in LXC registering direct .exe execution:

# $ /tmp/ndk-replicant/tmp/build-3038/maketab.exe 

# run-detectors: unable to find an interpreter for /tmp/ndk-replicant/tmp/build-3038/maketab.exe

# Work-around:

update-binfmts --disable

dpkg-reconfigure wine1.4 --pri=high

</pre>

Code fixes:

<pre>

# build-ndk-stack/elff/ produces a warning with mingw32, and uses -Werror

# cf. https://android.googlesource.com/platform/ndk/+/32e74f3f1b969ff65f037e1ee89e21a5cbc0ecf0

sed -i -e 's/-Werror//' sources/host-tools/ndk-stack/GNUMakefile

# TODO: maybe 'export EXTRA_CFLAGS=-Wall' would be enough?

# TODO: does this mean google was rebuilding from Ubuntu 10.04 instead of 12.04?

</pre>

...

<pre>

bash $NDK/build/tools/make-release.sh --toolchain-src-dir=$HOME/ndk-dl --release=r8b2 --incremental

# /home/replicant/ndk-dl/build/../binutils/binutils-2.21/gold/arm.cc:2171: internal compiler error: in make_rtl_for_nonlocal_decl, at cp/decl.c:4971

# => let's disable the windows build for now.. maybe better with 10.04? or a later ndk.git revision?

</pre>

h3. Use of prebuilts

Check how much of $topdir/prebuilts/ is used to compile the NDK. We shouldn't rely on untrusted binaries.

h3. Other build method

Attempt to rebuild r8e with the same build environment, but checkout-ing precise .git revisions from ndk.git and development.git:

less patches + local LLVM repo + precise control over the ndk scripts revision

According to @ndk/docs/DEVELOPMENT.html@ one only needs:

  git clone https://git.androidproject.xxx/platform/ndk.git ndk

  git clone https://git.androidproject.xxx/platform/development.git development

This means we wouldn't rely on exactly the build scripts shipped in Replicant 4.2.

h4. Yet another build method

@ndk/docs/DEVELOPMENT.html@ references using an existing (trusted) NDK to build the next one.