RFC: Scoped attributes for checked arithmetic

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[Pretty]: https://github.com/glaebhoerl/rfcs/blob/scoped-attributes-for-checked-arithmetic/active/0000-scoped-attributes-for-checked-arithmetic.md
In what scenario would overflow be Rusts problem when interfacing with existing C libraries in particular? It is not like we can prevent overflow in the C code (which may then lead to memory unsafety).