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

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

This howto describes how to create a 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.

The result is a 32-bit executable. If you want to create a 64-bit executable,
have a look at the [[64-bit cross-compilation example|examples/cross-compiling-64-bit-windows-binary]].

### Overview

The idea is simple:

* Install MinGW and Wine.
* 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 mingw32 wine git-core
	sudo apt-get build-dep tinc

Other Linux distributions may also have MinGW packages, use their respective
package management tools to install them.  Debian installs the cross-compiler
in `/usr/i586-mingw32msvc/`. Other distributions might install it in another
directory however, for example `/usr/i686-pc-mingw32/`. Check in which directory
it is installed, and replace all occurences of `i586-mingw32msvc` in this
example with the correct name from your distribution.

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

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

	mkdir $HOME/mingw
	cd $HOME/mingw
	apt-get source openssl liblzo2-dev zlib1g-dev
	git clone git://tinc-vpn.org/tinc

### Making cross-compilation easy

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

	mkdir $HOME/bin
	cat >$HOME/bin/mingw << EOF
	#!/bin/sh
	export CC=i586-mingw32msvc-gcc
	export CXX=i586-mingw32msvc-g++
	export CPP=i586-mingw32msvc-cpp
	export RANLIB=i586-mingw32msvc-ranlib
	export PATH="/usr/i586-mingw32msvc/bin:$PATH"
	exec "$@"
	EOF
	chmod u+x $HOME/bin/mingw

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 `mingw` script by
hand instead of calling the mingw script for every `./configure` or `make`
command, or execute `$HOME/bin/mingw $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 $HOME/mingw/lzo2-2.03
	./configure --host=i586-mingw32msvc
	make
	DESTDIR=$HOME/mingw make install

### 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 $HOME/mingw/zlib-1.2.3.3.dfsg
	mingw ./configure
	mingw make libz.a
	DESTDIR=$HOME/mingw mingw make install

### Compiling OpenSSL

OpenSSL is always a bit hard to compile, because they have their own
`Configure` script that needs some tweaking. There is also a small bug in
e_os2.h in OpenSSL 0.9.8 that breaks compilation with recent versions of GCC.
If you have this version of OpenSSL, then first download
this [[openssl-cross-compilation.diff]] to your home directory, then patch
OpenSSL:

	cd $HOME/mingw/openssl-0.9.8k
	patch < $HOME/openssl-cross-compilation.diff

With OpenSSL 1.0.0, this problem is no longer present. However, `apt-get source` will have applied
Debian-specific patches that break cross-compiling a Windows binary. You need to undo those patches first:

	cd $HOME/mingw/openssl-0.9.8k
	quilt pop -a

Now you can compile OpenSSL.
Do not use the `-j` option when compiling OpenSSL, it will break.

	mingw ./Configure --openssldir=$HOME/mingw/usr/local mingw
	mingw make
	mingw 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 $HOME/mingw/tinc
	autoreconf -fsi
	./configure --host=i586-mingw32msvc --with-openssl=$HOME/mingw/usr/local
	make

### Testing tinc

Since Wine was installed, you can execute the resulting binary even on Linux.
You cannot do much however, since tinc requires a TAP-Win32 device, which is
not available in Wine. Still, the following command should work:

	$HOME/mingw/tinc/src/tincd.exe --help