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Comment by robryk | Hacker News Reader

Would

   int foo(int x, int y) { return x+y; }

compile? After all, this function can be called in a way that causes UB.

I think what OP is saying is that it should compile and not have any UB, because signed integer overflow should be well-defined.

(This is the case in e.g. C#.)

Presumably, that function would be a compiler error like this.

Unless your program can prove, that the function is only ever called with arguments that don't hit UB.