Obfuscated Tiny C Compiler

What is it ?

The Obfuscated Tiny C Compiler (OTCC) is a very small C compiler I wrote in order to win the International Obfuscated C Code Contest (IOCCC) in 2002.

My goal was to write the smallest C compiler which is able to compile itself. I choose a subset of C which was general enough to write a small C compiler. Then I extended the C subset until I reached the maximum size authorized by the contest: 2048 bytes of C source excluding the ';', '{', '}' and space characters.

I choose to generate i386 code. The original OTCC code could only run on i386 Linux because it relied on endianness and unaligned access. It generated the program in memory and launched it directly. External symbols were resolved with dlsym().

In order to have a portable version of OTCC, I made a variant called OTCCELF. It is only a little larger than OTCC, but it generates directly a dynamically linked i386 ELF executable from a C source without relying on any binutils tools! OTCCELF was tested succesfully on i386 Linux and on Sparc Solaris.

NOTE: My other project TinyCC which is a fully featured ISOC99 C compiler was written by starting from the source code of OTCC !

Download

Compilation:
gcc -O2 otcc.c -o otcc -ldl
gcc -O2 otccelf.c -o otccelf 
Self-compilation:
./otccelf otccelf.c otccelf1
As a test, here are the executables generated by OTCCELF: otcc1, otccelf1, otccex1.

C Subset Definition

Read joint example otccex.c to have an example of C program.

OTCC Invocation

You can use OTCC by typing:
otcc prog.c [args]...
or by giving the C source to its standard input. 'args' are given to the 'main' function of prog.c (argv[0] is prog.c).

Examples:

An alternate syntax is to use it as a script interpreter: you can put
#!/usr/local/bin/otcc
at the beginning of your C source if you installed otcc at this place.

OTCCELF Invocation

You can use OTCCELF by typing:
otccelf prog.c prog
chmod 755 prog
'prog' is the name of the ELF file you want to generate.

Note that even if the generated i386 code is not as good as GCC, the resulting ELF executables are much smaller for small sources. Try this program:

#include <stdio.h>

main() 
{
    printf("Hello World\n");
    return 0;
}
Results:
CompilerExecutable size (in bytes)
OTCCELF424
GCC (stripped)2448

Links

License

The obfuscated OTCC and OTCCELF are public domain. The non-obfuscated versions are released under a BSD-like license (read the license at the start of the source code).
This page is Copyright (c) 2002 Fabrice Bellard
Fabrice Bellard - http://bellard.org/ - http://www.tinycc.org/