[Gibbon1]

"So now you need to check everything, everywhere"

If you want to write robust code in C that what you need to do. UB doesn't give you runtime checks nor compile time checks for overflow.

"Does not give you any assurances that your answer will be correct."

Your problem is you think C's int is a mathematical integer when it is not. It's an ordered set.

[chongli]

You misunderstood what I was saying. Those statements are from the perspective of the hypothetical language proposal I was critiquing. That proposal turns off all the optimizations by default and forces you to add annotations to turn them back on. At the same time, it does not actually give you anything useful for your trouble because it still doesn't solve the problem of signed overflow giving incorrect results.

The way C is now, you get the performance by default and safety is opt-in. That's the tradeoff C makes and it's a good one. Other languages give safety by default and make performance opt-in. The proposal I was responding to gives neither.