No useful and reliable way to detect integer overflow in C/C++?

Question

No, this is not a duplicate of How to detect integer overflow?. The issue is the same but the question is different.

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The gcc compiler can optimize away an

Answer 1

The gcc developers are entirely correct here. When the standard says that the behavior is undefined that means exactly that there are no requirements on the compiler.

As a valid program can not do anything that causes UB (as then it would not be valid anymore), the compiler can very well assume that UB doesn't happen. And if it still does, anything the compiler does would be ok.

For your problem with overflow, one solution is to consider what ranges the caclulations are supposed to handle. For example, when balancing my bank account I can assume that the amounts would be well below 1 billion, so a 32-bit int will work.

For your application domain you can probably do similar estimates about exactly where an overflow could be possible. Then you can add checks at those points or choose another data type, if available.