[[!meta title="cross-compiling tinc for 64-bit Windows under Linux using MinGW"]]

## Howto: cross-compiling tinc for Windows under Linux using MinGW

This howto describes how to create a 64-bit Windows binary of tinc. Although it is
possible to compile tinc under Windows itself, cross-compiling it under Linux
is much faster. It is also much easier to get all the dependencies in a modern
distribution. Therefore, this howto deals with cross-compiling tinc with MinGW
under Linux on a Debian distribution.

### Overview

The idea is simple:

* Install 64-bit MinGW.
* Create a directory where we will perform all cross-compilations.
* Get all the necessary sources.
* Cross-compile everything.

### Installing the prerequisites for cross-compilation

There are only a few packages that need to be installed as root to get started:

	sudo apt-get install gcc-mingw32 mingw64 git-core wget
	sudo apt-get build-dep tinc

Other Linux distributions may also have 64-bit MinGW packages, use their respective
package management tools to install them.  Debian installs the cross-compiler
in `/usr/amd64-mingw32msvc/`. Other distributions might install it in another
directory however. Check in which directory
it is installed, and replace all occurences of `amd64-mingw32msvc` in this
example with the correct name from your distribution.

At the time of writing, the gcc-mingw32 package contains the 64-bit compiler as
well, in the future this might be put into its own package. Also, a header file
is missing in the amd64-mingw32msvc include directory, a workaround is to
create a symlink to the otherwise identical 32-bit version of that header file:

	ln -s ../../i586-mingw32msvc/include/getopt.h /usr/amd64-mingw32msvc/include/getopt.h

### Setting up the build directory and getting the sources

We will create a directory called `mingw64/` in the home directory.  We use
apt-get and wget to get the required libraries necessary for tinc, and use
`git` to get the latest development version of tinc.

	mkdir $HOME/mingw64
	cd $HOME/mingw64
	apt-get source liblzo2-dev zlib1g-dev
	wget http://www.openssl.org/source/openssl-1.0.0.tar.gz
	tar xzf openssl-1.0.0.tar.gz
	git clone git://tinc-vpn.org/tinc

### Making cross-compilation easy

To make cross-compiling easy, we create a script called `mingw64` that will set
up the necessary environment variables so configure scripts and Makefiles will
use the 64-bit MinGW version of GCC and binutils:

	mkdir $HOME/bin
	cat >$HOME/bin/mingw64 << EOF
	#!/bin/sh
	export CC=amd64-mingw32msvc-gcc
	export CXX=amd64-mingw32msvc-g++
	export CPP=amd64-mingw32msvc-cpp
	export RANLIB=amd64-mingw32msvc-ranlib
	export PATH="/usr/amd64-mingw32msvc/bin:$PATH"
	exec "$@"
	EOF

If `$HOME/bin` is not already part of your `$PATH`, you need to add it:

	export PATH="$HOME/bin:$PATH"

We use this script to call `./configure` and `make` with the right environment
variables, but only when the `./configure` script doesn't support cross-compilation itself.
You can also run the export commands from the `mingw64` script by
hand instead of calling the mingw64 script for every `./configure` or `make`
command, or execute `$HOME/bin/mingw64 $SHELL` to get a shell with these
environment variables set, but in this howto we will call it explicitly every
time it is needed.

### Compiling LZO

Cross-compiling LZO is easy:

	cd $HOME/mingw64/lzo2-2.03
	./configure --host=amd64-mingw32msvc
	make
	DESTDIR=$HOME/mingw64 make install

If it fails with a message about not passing the "ACC" test,
create a symlink for the missing getopt.h file as mentioned above.

### Compiling Zlib

Cross-compiling Zlib is also easy, but a plain `make` failed to compile the
tests, so we only build the static library here:

	cd $HOME/mingw64/zlib-1.2.3.3.dfsg
	mingw64 ./configure
	mingw64 make libz.a
	DESTDIR=$HOME/mingw64 mingw64 make install

### Compiling OpenSSL

Although older versions will not compile, OpenSSL 1.0.0 is easy.
Do not use the `-j` option when compiling OpenSSL, it will break.

	cd $HOME/mingw64/openssl-1.0.0
	mingw64 ./Configure --openssldir=$HOME/mingw64/usr/local mingw64
	mingw64 make
	mingw64 make install

### Compiling tinc

Now that all the dependencies have been cross-compiled, we can cross-compile
tinc.  Since we use a clone of the git repository here, we need to run
`autoreconf` first. If you want to cross-compile tinc from a released tarball,
this is not necessary.

	cd $HOME/mingw64/tinc
	autoreconf -fsi
	./configure --host=amd64-mingw32msvc --with-openssl=$HOME/mingw64/usr/local
	make