21st IOCCC Source Code Released

First time accepted submitter johntromp writes "Source code for the 21st International Obfuscated C Code Contest was released last weekend, following announcement of the winners on Sep 30, and just over a month after the submission window closed on Sep 14, a new speed record for the judges. Happy source code browsing!"

Surprisingly cool Re:OS doesn't matter.

[Fubari]

Surprisingly cool stuff; the hint files of the various entries [ioccc.org] are worth a look too. For example, this is from the zeitak/hint.html [ioccc.org] entry:

Selected Judges Remarks:

This is an extremely subtle and twisted piece of Gold award winning code!

The judges had spent a considerable amount of time analyzing this entry. At one point we spent 18 minutes just to understand 18 key characters of this code.

The file zeitak_deobfucate.c provides a version that has been slightly deobfuscated. You may find reading that file helpful in your attempt to understand this extremely subtle entry.

Author’s comments:
Nesting Errors Detector

What does it do
As you have probably understood by looking at the source*, this program has something to do with parenthesis (and equality of opening and closing parenthesis, if you look close enough). It goes over the file given to it and checks that every opening (, [, or { has a matching closing one and vice versa. It also checks that every “ or ‘ is closed.

If an error is detected, an error message will be printed. If the problem is a superfluous closing bracket, it will even print a few characters around it’s position.

Make sure you view the source with 4 spaces tab width.

Features
Ignores parenthesis inside strings or character constants, so no errors will be detected in the following line:

printf(")");

Doesn’t get confused by the 1984/anonymous entry!

Mis-Features
Escapes (e.g. \") are ignored, so the following line will produce an error:

printf("\"");

Obfuscation
IOCCC winners already contain entries without digits, control-flow keywords and certain operators in their source. This entry has an even more limited source, that is:

Without any digits.
Without any character constants.
Without using functions from headers other than stdio.
Without any control-flow keywords (not even the ?: operator).
Without any arithmetic or logic operators!

Underhanded was always more interesting

[monkeyhybrid]

Very clever stuff but I always found The Underhanded C Contest [xcott.com] much more interesting. Sadly the last one of those was in 2009. I'd love to see that return.