Building Linux software into a prefix

If, instead of using a pre-made game engine package like Unity, you prefer picking a few libraries and mixing them in your own way, you might reach a point where you want to build your own versions of those libraries so that you can bundle them with your game.

See the Distributing Linux builds page of this book

What is a prefix?

When you install software on Linux, files are placed into a directory hierarchy called the prefix. The default prefix is usually /usr or /usr/local, which means:

• Binaries are installed in /usr/bin/
• Libraries are installed in /usr/lib/
• Data files are installed in /usr/share/
• ...and so on

By specifying your own prefix, you can install a library into an unprivileged, user-owned directory, ready for bundling with your game. Building each library into its own prefix makes it clear which files belong to which library.

For the purpose of bundling your libraries, you would copy the files from your prefix's lib/ directory into your game's bundled library folder.

CMake

CMake is the most common build system for open-source C/C++ libraries. The recommended build process uses an out-of-tree build directory:

$ cmake -B build -DCMAKE_INSTALL_PREFIX=$HOME/myprefix/chipmunk2d
$ cmake --build build
$ cmake --install build

Meson

Meson is used by many Linux libraries, particularly in the freedesktop/GNOME ecosystem. It always uses out-of-tree builds:

$ meson setup build --prefix=$HOME/myprefix/my-library
$ meson compile -C build
$ meson install -C build

autotools (./configure && make)

Some older libraries still use autotools. The build process is:

$ ./configure --prefix=$HOME/myprefix/sdl2
$ make
$ make install

Note: --prefix usually has to be an absolute path.

For a cleaner setup, you can do an out-of-tree build by running configure from a separate directory:

$ mkdir build && cd build
$ ../my-library-source/configure --prefix=$HOME/myprefix/my-library
$ make
$ make install

This keeps the source directory untouched.

Why build your own libraries?

Copying libraries straight out of /usr/lib and into your game's bundle is not always the best idea. Distribution-packaged libraries may have patches or configuration specific to that distribution that cause them to behave differently elsewhere.

Building from source also gives you flexibility: if you find a bug in a library you depend on, you can apply a fix and ship it yourself without waiting for the upstream maintainer and distribution packagers to catch up.