Reminds me of the time I had to program a Z80-based controller board. It came with a non-standard C Compiler where integers were 16-bits long. Of course, I didn't realize this at first (I suppose I could have read the documentation, but...), so I had to figure it out for myself while debugging :)
It was my first time programming C on something that wasn't a 32 bit CPU :)
EDIT: Forgot to mention that C spec only specifies "at least X" sizes, there is no portability guarantee if the types from stdint.h aren't used.
http://en.cppreference.com/w/c/language/arithmetic_types