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by mike_hock 27 days ago
> A clear majority of the UB problems with C could be fixed if the standards committee slowly moved all UB into IB

There is no such thing as getting rid of "all UB."

What behavior is the implementation supposed to prescribe for a write to an unpredictable garbage address you read from the network? It could overwrite your code. It could overwrite any value anywhere. It could overlap with anything. Prescribing defined behavior for absolutely everything would require defining a precise, unoptimizable 1-to-1 mapping to assembly code and disallowing any multithreading.
1 comments
lelanthran 27 days ago
> What behavior is the implementation supposed to prescribe for a write to an unpredictable garbage address you read from the network? I

"The compiler is not allowed to elide a write to a garbage address".

Wasn't that easy?

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mike_hock 24 days ago
No, because that doesn't mean anything. All the other guarantees the compiler has to make about the other parts of your program have potentially been violated by the write, so the compiler can't guarantee any particular behavior.

Hence, "undefined behavior," of the entire program, not just that particular write.

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