I mean this is beyond cruel.
Of course the simple
#define ' ' = '\n'
placed into some obscure header file (for C++) they have no reason to look in would also cause no end of agony. Basically it replaces EVERY space used in the code with a new line instead (aka as if pressing enter key)
You can have a lot of fun with #define
#define if while /makes every if statement an infinite loop
#define break /switch case statements now run every option after the choice, every time
#define true false or #define false true /depends on what the person uses, but this will be very annoying
#define struct union /structs now can only hold one data object at a time, when you change a value that is now the only value in the "struct"
#define else /else statements no longer exist, ALL the "else" code blocks run
Any one of these could be sanity breaking, literal days of bug hunting to find because the compiler errors will never point to these lines of code. Also not coding atm, but bored and found this. Thought it was funny