I wouldn't describe this as "no-one knows" the type of char + char. I know what the type of char + char is. I know that it's either int or unsigned int, depen

I wouldn't describe this as "no-one knows" the type of char + char. I know what the type of char + char is. I know that it's either int or unsigned int, depending on the ranges of values supported by types char and int. I know what it is for any given implementation. And I know that it's int, not unsigned int, for every implementation I've ever used or am likely to use. Implementation-defined features are not some unsolvable mystery. They're just implementation-defined.