The 29th International Obfuscated C Code Contest (IOCCC) 2025 Winners

307 points - today at 5:47 AM

Source

Comments

haunter today at 6:35 AM
The GameBoy emulator's code also looks like the GameBoy. Slow clap this is insane, definitely my favorite entry.

https://github.com/ioccc-src/winner/blob/master/2025/ncw1/pr...

The author, Nick Craig-Wood, is the creator of rclone!

s-macke today at 7:41 AM
My favorite is the 366-byte C program emulator that can run Linux and Doom [0]. The VM implements an OISC - a One Instruction Set Computer [1].

[0] https://github.com/ioccc-src/winner/blob/master/2025/cable/p...

[1] https://github.com/ioccc-src/winner/blob/master/2025/cable/R...

yayitswei today at 7:36 AM
In case anyone was wondering, the IOCCC specifically permits LLM use in their guidelines.

"The IOCCC has a rich history of remarkable winning entries created by authors who skillfully employed various techniques (often their own tools) to develop their code."

aquir today at 6:30 AM
The website itself is obfuscated, it’s not easy to find the C sources at all!
ollybee today at 9:15 AM
I with the Underhanded C Contest would come back, it was far more interesting to me. No disrespect intended to the Obfuscated C competitors.
roer today at 1:05 PM
There's a Frieren [1] reference in there! https://www.ioccc.org/2025/yang2/index.html

One of the main characters is called Fern, and she almost exclusively uses the common offensive magic of Zoltraak.

[1] https://en.wikipedia.org/wiki/Frieren

msk-lywenn today at 12:50 PM
OMG, my game boy game of life implementation is included in one of the winning entries!
locao today at 2:39 PM
Back in 2000 I was being interviewed for my first internship, to join a team of C programmers. They showed me one of the winner entries of the prior years, asked me to review the code and left the room. About 5 minutes later they came back:

– And?

– I'm sorry I wasted your time. I just can't understand it.

They burst into laughs and asked me to start the joining process.

I wonder if people still make fun of interns. I still have a good laugh when I remember myself freaking out.

TZubiri today at 9:04 AM
I love the submissions of IOCCC generally, but the schedule and submission process looks like a mess, is that part of the joke? Or is it just because being consistent and designing a simple process is hard¡
Gathering6678 today at 1:48 PM
There's another contest called Underhanded C that I enjoyed a lot reading, but it has been inactive for a decade at this point...
tomcloney007 today at 3:54 PM
[flagged]
swordlucky666 today at 2:04 PM
[dead]
nsoonhui today at 8:11 AM
I'm not sure this kind of competition is still meaningful, given that LLM can easily convert a program clearly written in any programming language to the most obfuscated C code, and can still easily verify it's correctness in an automated way.

Do I miss anything?

larodi today at 6:39 AM
Tis a pity to not have LLMs compete, given level of obfuscation they be capable of.
rurban today at 7:15 AM
So like at a film festival, 90% of the entries won a price, but unlike a film festival there's not a single best. Weird, like modern education.