← Back to the index page

Compiling Lua for MS-DOS/FreeDOS

One cold spring day, while playing classic DOS games like Wolfenstein 3D, Doom, and Mortal Kombat II, I had a crazy idea—what if I could run the Lua programming language on DOS? Lua is lightweight, takes up very little memory, and is written in C. In theory, it should be possible to run it on any DOS-like operating system.

As I started researching, I realized I wasn’t the only one with this idea. I came across a developer from the United Kingdom who had already solved the problem for Lua 5.4.4.

Building on Claude’s solution, I made some minor modifications and improvements. Since I didn’t have an old machine, I had to run it on a modern computer via a USB flash drive. I tested the solution on three different setups:

All three ran Lua 5.4.7 without any issues, at least none that I’ve found so far!

Preparing hardware/software

Me (as you probably as well) do not have a 30-40-year-old machine to install DOS on hardware. Then a handy USB drive can boot FreeDOS on a modern PC.

Another option is to use DOSBox emulator for the DOS operating system.

Issues

Claude fixed many issues in Lua’s source code to make it compatible with Turbo C, which I used as a foundation while making additional minor modifications to the C code.

The main issue here is that Borland Turbo C’s offsetof function is broken. As a workaround, Claude (thanks a lot!) defines it as OFFSETOF:

+#define OFFSETOF(T,f) ((size_t)(char *)&(((T*)(void*)0)->f))

Another challenge is the absence of locale support in DOS, which is inherently a Unix/Linux concept. To work around this, locale-related methods and constants are simply mocked in luaconf.h, and an empty locale.h file is placed in the source code directory to allow inclusion without errors.

+#define CLOCKS_PER_SEC CLK_TCK

-
+/* locale */
+#define LC_ALL 0
+#define LC_COLLATE 1
+#define LC_CTYPE 2
+#define LC_MONETARY 3
+#define LC_NUMERIC 4
+#define LC_TIME 5
+#define strcoll strcmp
+#define setlocale(x,y) ("C")
+#define mktime(x) (-1)
+#define strftime(x,y,z,w) (0)

 #endif

After numerous attempts and failures—mostly due to frustrating out-of-memory errors—I also discovered that line endings differ between DOS and Unix/Linux. The unix2dos command is a helpful tool for converting them, but for some reason, it didn’t completely resolve the issue. As a workaround, I passed the --binary flag to the patch utility.

You can find the scripts in the GitHub repo lua-for-dos.

The process

Step 1

... downloading sofwtare ...
tar -xvf "$LUA.tar.gz"
mv "$LUA" lua

echo '/* blank */' > lua/src/locale.h
cd lua/
unix2dos src/* 
unix2dos ../lua-5.4.7-for-dos-with-borland-turbo-c-2.01.patch
patch -p1 -i "../lua-5.4.7-for-dos-with-borland-turbo-c-2.01.patch" --binary

Tip

You can try to compile Lua with LUA_32BITS enabled, but for some reason it does not work in FreeDOS. Here is a 32-bit patch lua-5.4.7-for-dos-with-borland-turbo-c-2.01.patch32bits.

Step 2

Compile under DOS by running the COMPILE.BAT. This DOS batch file should be run inside a DOS environment; it won’t execute on the GNU/Linux machine.

PATH=C:\TC
CD C:\LUA\SRC
TCC -w- -ms- -mh -I. -c *.c
DEL LUAC.OBJ
TCC -w- -ms- -mh -eLUA.EXE *.obj
DEL LUA.OBJ
TCC -w- -ms- -mh -I. -c LUAC.C
TCC -w- -ms- -mh -eLUAC.EXE *.OBJ
CD ..
MKDIR BIN
COPY SRC\LUA.EXE BIN
COPY SRC\LUAC.EXE BIN
CD BIN
LUA

Download Lua binaries compiled for DOS

Video demonstration

The compilation actually takes 5–10 minutes, depending on the machine. I tried to keep the videos under one minute.

DOSBox

PC

References

Feedback

For feedback, please check the contacts section. Before writing, please specify where you came from and who you are. Sometimes spammers go insane. Thank you in advance for your understanding.

← Back to the index page