I love Doom. Actually, Doom II was the first PC game I ever got in my hands onto. The game was fast-paced, gritty and scary like hell, even with its 8 bit architecture. The sound was ominous, the levels and monsters were darn frikin’ hard to go against … I totally agree with anyone that would put it onto their top list of games since the beginning of that instrustry we call “gaming”.

This post is about compiling Doom on a modern Linux distro.

The source of the Doom engine (which ran Doom, Doom II, and Ultimate Doom) was released in 1997 as a Linux port that used X with a separate sound server. It is still available here.

I got interested in the source code in 2003 and started taking notes about compilation, PCX and 8bit paletting, and WAD (de)construction. Now, in 2010, I re-read my notes and decided to give it a go again, this time putting those notes public, although there’s nothing really new here for anyone. With so many ports of Doom that have spawned over the years, there are better options today in playing Doom with full screen graphics, perhaps in 3D, and MP3 sound and music instead using 16 bit mono WAVs and on board MIDI.

But I like retro stuff and this is as close as we can get to the original. The SDL version, made by SDL creator Sam Lantinga, is a straightfoward port of the original with sound and can run on 640 x 480 without palletting. It’s a great way to see how SDL works. But before compiling that version, keep reading this post, there is at least one modification you should be aware of.

Fixing errors and compiling

The first thing about Doom, is that its creator, id software, did released the source code but not any of the data files to run it, called IWADs, which contain the images and sounds of the game. You must either have the commercial version of Doom, Doom II or Ultimate Doom, or the shareware version (a copy of the shareware IWAD is available here). Unzip it and put that file somewhere on your system. We’ll need to point to it later on.

Unzipping the file gives you two packages, the source code of DOOM and a separate sound server that Doom will imbed at run time (apparrently, id licenced a copyrighted sound engine at the time, which is why there is no original DOS release: ‘A mistake’ says John Carmack in the README.TXT file.)

Unzip the source code and make the following changes:

In i_video:49, replace

#include <errnos.h>

with

#include <errno.h>

In i_sound.c:166 and i_video.c:669, delete all declarations of

extern int errno;

and include this file somewhere at the top of i_sound.c:

#include <errno.h>

In s_sound.c:367, replace

#ifndef SNDSRV

with

#ifndef SNDSERV

In the Makefile, add the -DSNDSERV define for compilation.

Finally, and this affects both the original and SDLDoom, change d_main.c:587 from

doomuwad = malloc(strlen(doomwaddir)+1+8+1);

to

doomuwad = malloc(strlen(doomwaddir)+1+9+1);

This “off-by-one” error will generate a ASSERT error in malloc.c:3074 once the X display kicks in. The gdb debugger will tell you so, and yet we are very far from any video initialization at this moment. It took me a while to trap this.

Compile by simply calling ‘make’ at the command line. Everything should compile under 30 seconds. Don’t (?) worry about all the warnings you’ll see passing by. They shouldn’t affect the game at this point. Feel free to clean up the code if you like.

Compiling the sound server

Unzip the sound server’s package and change to that directory. Simply call ‘make’ at the command line.

Move the ‘sndserver’ binary located in the ‘linux’ directory to the same directory you put your IWAD, mentionned above.

Switching to 8 bit

Doom runs in 8 bit (256 palettized colors) at a whoppin size of 320 x 200 pixels. It’s better to simply call another X desktop instead of ruining your current setup.

Issue the following on the command line.

sudo startx -- :1 -depth 8 vt8

This starts another desktop at vt8 (i.e. Ctrl-Alt-F8. You can return to your original desktop with Ctrl-Alt-F7 or loggin off from that session). You’ll notice how rough your desktop will look because of the 8 bit palette it’s running on.

Note that you will be running your new desktop with super-user privileges, so be VERY careful.

Open up a console and set an environment variable called DOOMWADDIR like so:

export DOOMWADDIR=<my path>

and replace <my path> with the location of the IWAD and sound server. If you dip into the code, there always a way to set those changes to a permanent location without defining this value or doing it through some parameter.

You can now run the binary located at linux/linuxdoom in the source code directory.

You’ll see your desktop flashing because Doom will set up its palette to it.

Voilà. Enjoy playing Doom on an itsy bitsy scale.

You can alway resize your desktop to 640 x 480 to see it a little larger. Don’t forget to set it back to its original size. I believe if you don’t, it will screw up your default settings once you run X again from a fresh boot.

If you don’t want to go through all this trouble, make the change I recommend to d_main.c:587 in SDLDoom, compile it and call the -fullscreen parameter to play Doom at a reasonable scale.