wsl-doom

Doom (linuxdoom-1.10) patched to compile and run on 64-bit Linux / WSL2 with TrueColor X11 and SDL audio.

Doom source port family tree (modified from Wikipedia)

What is this?

The original linuxdoom-1.10 source release from id Software assumes 32-bit pointers and 8-bit PseudoColor X11 displays — neither of which exist on modern systems. This repo contains the minimal patches needed to get it running on x86-64 Linux (including WSL2 on Windows).

Changes from original linuxdoom-1.10

64-bit portability fixes

File	Change	Why
r_data.c	*4 → *sizeof(void*) for pointer arrays	Pointer arrays need 8 bytes per entry, not 4
r_data.c	void **columndirectory → int columndirectory	WAD format uses 32-bit offsets; void** adds padding on 64-bit
p_setup.c	total*4 → total*sizeof(line_t*)	Pointer array allocation
d_net.c	(int)& → (long)&	Pointer-to-int casts need long on LP64
p_saveg.c	(int) → (long) for pointer/index casts	Same
r_draw.c	(int)translationtables → (long)	Same
m_misc.c	(int) "string" → (long) "string"	Same
i_sound.c	extern int errno → #include <errno.h>	glibc defines errno as a macro
i_system.c	mb_used = 6 → mb_used = 32	64-bit pointer arrays + sound precaching need more zone memory
m_misc.c	defaultvalue field int → long, *(long*) writes for string entries	default_t stores string pointers in defaultvalue; 4-byte int truncates 64-bit pointers
info.c/info.h	sprnames[NUMSPRITES] → sprnames[NUMSPRITES+1] with 0 terminator	R_InitSpriteDefs iterates until NULL; original relies on zero-filled memory after array
d_main.c	Removed #ifndef SNDSERV / #ifndef SNDINTR guards	These conditionals are unnecessary without the external sound server; removing them allows the in-process mixing and SDL output to run
m_misc.c	Removed SNDSERV defaults block (sndserver_filename, mb_used=2)	Not used with SDL audio

TrueColor X11 patch

Modern X servers don't support 8-bit PseudoColor. i_video_truecolor.c replaces i_video.c with:

• 24-bit TrueColor visual instead of 8-bit PseudoColor
• rgb_palette[256] lookup table for 8-bit → 32-bit ARGB conversion
• Separate screens[0] buffer (8-bit indexed, not aliased to 32-bit XImage)
• Works with MITSHM extension on WSL2

SDL audio patch

The original linuxdoom-1.10 output sound via OSS (/dev/dsp), a Linux audio API deprecated in 2002 and unavailable on modern systems. The game also supported an external sndserver process, but this was a separate proprietary binary not included in the source release. As a result, the open-source Linux Doom had no working audio out of the box.

i_sound_sdl.c replaces i_sound.c with SDL2 audio output:

• All original mixing code (channel management, volume lookup, stereo separation) is preserved unchanged
• OSS open("/dev/dsp") + write() replaced with SDL_OpenAudioDevice + SDL_QueueAudio
• Audio queue capped at ~100ms to prevent sound delay accumulation
• Removed OSS includes, ioctl helpers, and timer interrupt code (SNDINTR)
• Fixed linked sound length calculation: (ptr - array)/sizeof(T) → ptr - array (C pointer subtraction already returns element count, extra divide was wrong in original)
• sndserver_filename retained as a stub for compatibility with the defaults system

SDL2 was chosen over PulseAudio or ALSA because it automatically selects the best available backend (PulseAudio, PipeWire, ALSA, etc.) — no user configuration needed. It's also the standard audio library used by every modern Doom source port.

No music support yet — Doom's MUS format requires a MIDI synthesizer, which is a larger addition.

Building

Prerequisites

sudo apt install gcc libx11-dev libxext-dev libsdl2-dev

Compile and link

# Compile (skip original i_video.c and i_sound.c — replaced by patched versions)
for f in *.c; do
  [ "$f" = "i_video.c" ] && continue    # use i_video_truecolor.c instead
  [ "$f" = "i_sound.c" ] && continue    # use i_sound_sdl.c instead
  gcc -c -DNORMALUNIX -DLINUX -w "$f" -o "$(basename "$f" .c).o" $(sdl2-config --cflags)
done

# Link
gcc *.o -o linuxxdoom -lXext -lX11 -lm $(sdl2-config --libs)

Run

You need a WAD file. The shareware doom1.wad works:

./linuxxdoom -iwad doom1.wad

To jump straight to a level:

./linuxxdoom -iwad doom1.wad -warp 1 1

WSL2 setup

You need an X server running on Windows. Options:

• VcXsrv (free)
• X410 (paid, simpler)

Set DISPLAY in your .bashrc:

export DISPLAY=$(cat /etc/resolv.conf | grep nameserver | awk '{print $2; exit;}'):0.0

Controls

Key	Action
Arrow keys	Move / turn
Ctrl	Shoot
Space	Open doors / use
Shift	Run
Escape	Menu
Tab	Automap
1-7	Select weapon

License

Original source code released by id Software under the Doom Source Code License.