How in the world did they come up with the obfuscated code for this? Surely they must be using a tool?
I remember one back in the day which wasn't obfuscated at all. It was clearly a simple utility. Except that it didn't do what you thought it did, it did something completely different. (alas I can't remember the details...)
Perhaps it was the Underhanded C Contest[1][2]? It's another competition, entires there often seem simple and perform something unexpected.
For an example, see this StackOverflow question and its detailed answers for an overview of what obfuscation techniques can be used, although many more exist of course: https://stackoverflow.com/questions/15393441/obfuscated-c-co...
I was able to compile it on macOS, but had to include an extra flag to stop clang from being too strict (version 16):
cc -Wno-implicit-function-declaration -std=c89 -o test test.c
./test