Is there a clean way to write overflowing adds?

[H2CO3]

@jbe

I guess calling something "undefined behavior" in C is usually different from when you call something UB in Rust?

No.

@jbe

Can the "undefined behavior" in C affect anything else than the result of the integer computation?

Yes. What you are thinking about is Unspecified Behavior. Undefined Behavior means that any other part of the program can do absolutely whatever it wants. Integer overflow can erase your hard disk and still claim to be conforming.

@jbe

but does anyone have a more authoritative link on (signed) integer overflows being undefined in C?

It's §6.5.5 in C11:

5. If an exceptional condition occurs during the evaluation of an expression (that is, if the result is not mathematically defined or not in the range of representable values for its type), the behavior is undefined.